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1. Combining robust urine biomarkers to assess chronic kidney disease progressionResearch in context

Author

Frank Bienaimé, Mordi Muorah, Marie Metzger, Melanie Broeuilh, Pascal Houiller, Martin Flamant, Jean-Philippe Haymann, Jacky Vonderscher, Jacques Mizrahi, Gérard Friedlander, Bénédicte Stengel, Fabiola Terzi, François Vrtovsnik, Eric Daugas, Emmanuelle Vidal-Petiot, Christian Jacquot, Alexandre Karras, Stéphane Roueff, Eric Thervet, Pascal Houillier, Marie Courbebaisse, Dominique Eladari et Gérard Maruani, Pablo Urena-Torres, Jean-Jacques Boffa, Pierre Ronco, H. Fessi, Eric Rondeau, Emmanuel Letavernier, and Nahid Tabibzadeh

Subjects
Chronic kidney disease progression, Urinary biomarkers, EGF, TGF-α, CCL2, NGAL, Medicine, Medicine (General), R5-920
Abstract

Summary: Background: Urinary biomarkers may improve the prediction of chronic kidney disease (CKD) progression. Yet, data reporting the applicability of most commercial biomarker assays to the detection of their target analyte in urine together with an evaluation of their predictive performance are scarce. Methods: 30 commercial assays (ELISA) were tested for their ability to quantify the target analyte in urine using strict (FDA-approved) validation criteria. In an exploratory analysis, LASSO (Least Absolute Shrinkage and Selection Operator) logistic regression analysis was used to identify potentially complementary biomarkers predicting fast CKD progression, determined as the 51CrEDTA clearance-based measured glomerular filtration rate (mGFR) decline (>10% per year) in a subsample of 229 CKD patients (mean age, 61 years; 66% men; baseline mGFR, 38 mL/min) from the NephroTest prospective cohort. Findings: Among the 30 assays, directed against 24 candidate biomarkers, encompassing different pathophysiological mechanisms of CKD progression, 16 assays fulfilled the FDA-approved criteria. LASSO logistic regressions identified a combination of five biomarkers including CCL2, EGF, KIM1, NGAL, and TGF-α that improved the prediction of fast mGFR decline compared to the kidney failure risk equation variables alone: age, gender, mGFR, and albuminuria. Mean area under the curves (AUC) estimated from 100 re-samples was higher in the model with than without these biomarkers, 0.722 (95% confidence interval 0.652–0.795) vs. 0.682 (0.614–0.748), respectively. Fully-adjusted odds-ratios (95% confidence interval) for fast progression were 1.87 (1.22, 2.98), 1.86 (1.23, 2.89), 0.43 (0.25, 0.70), 1.10 (0.71, 1.83), 0.55 (0.33, 0.89), and 2.99 (1.89, 5.01) for albumin, CCL2, EGF, KIM1, NGAL, and TGF-α, respectively. Interpretation: This study provides a rigorous validation of multiple assays for relevant urinary biomarkers of CKD progression which combination may improve the prediction of CKD progression. Funding: This work was supported by Institut National de la Santé et de la Recherche Médicale, Université de Paris, Assistance Publique Hôpitaux de Paris, Agence Nationale de la Recherche, MSDAVENIR, Pharma Research and Early Development Roche Laboratories (Basel, Switzerland), and Institut Roche de Recherche et Médecine Translationnelle (Paris, France).

Published
2023
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2. Red Blood Cell AE1/Band 3 Transports in Dominant Distal Renal Tubular Acidosis Patients

Author

Jean-Philippe Bertocchio, Sandrine Genetet, Lydie Da Costa, Stephen B. Walsh, Bertrand Knebelmann, Julie Galimand, Lucie Bessenay, Corinne Guitton, Renaud De Lafaille, Rosa Vargas-Poussou, Dominique Eladari, and Isabelle Mouro-Chanteloup

Subjects
Diseases of the genitourinary system. Urology, RC870-923
Abstract

Introduction: Anion exchanger 1 (AE1) (SLC4A1 gene product) is a membrane protein expressed in both kidney and red blood cells (RBCs): it exchanges extracellular bicarbonate (HCO3–) for intracellular chloride (Cl–) and participates in acid−base homeostasis. AE1 mutations in kidney α-intercalated cells can lead to distal renal tubular acidosis (dRTA). In RBC, AE1 (known as band 3) is also implicated in membrane stability: deletions can cause South Asian ovalocytosis (SAO). Methods: We retrospectively collected clinical and biological data from patients harboring dRTA due to a SLC4A1 mutation and analyzed HCO3– and Cl– transports (by stopped-flow spectrophotometry) and expression (by flow cytometry, fluorescence activated cell sorting, and Coomassie blue staining) in RBCs, as well as RBC membrane stability (ektacytometry). Results: Fifteen patients were included. All experience nephrolithiasis and/or nephrocalcinosis, 2 had SAO and dRTA (dRTA SAO+), 13 dominant dRTA (dRTA SAO−). The latter did not exert specific RBC membrane anomalies. Both HCO3– and Cl– transports were lower in patients with dRTA SAO+ than in those with dRTA SAO− or controls. Using 3 different extracellular probes, we report a decreased expression (by 52%, P < 0.05) in dRTA SAO+ patients by fluorescence activated cell sorting, whereas total amount of protein was not affected. Conclusion: Band 3 transport function and expression in RBCs from dRTA SAO− patients is normal. However, in SAO RBCs, impaired conformation of AE1/band 3 corresponds to an impaired function. Thus, the driver of acid−base defect during dominant dRTA is probably an impaired membrane expression. Keywords: acidosis, renal tubular, anion exchange protein 1, erythrocyte, hematologic diseases, nephrocalcinosis, nephrolithiasis

Published
2020
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3. In silico model of the human ClC-Kb chloride channel: pore mapping, biostructural pathology and drug screening

Author

Maxime Louet, Sara Bitam, Naziha Bakouh, Yohan Bignon, Gabrielle Planelles, David Lagorce, Maria A. Miteva, Dominique Eladari, Jacques Teulon, and Bruno O. Villoutreix

Subjects
Medicine, Science
Abstract

Abstract The human ClC-Kb channel plays a key role in exporting chloride ions from the cytosol and is known to be involved in Bartter syndrome type 3 when its permeation capacity is decreased. The ClC-Kb channel has been recently proposed as a potential therapeutic target to treat hypertension. In order to gain new insights into the sequence-structure-function relationships of this channel, to investigate possible impacts of amino-acid substitutions, and to design novel inhibitors, we first built a structural model of the human ClC-Kb channel using comparative modeling strategies. We combined in silico and in vitro techniques to analyze amino acids involved in the chloride ion pathway as well as to rationalize the possible role of several clinically observed mutations leading to the Bartter syndrome type 3. Virtual screening and drug repositioning computations were then carried out. We identified six novel molecules, including 2 approved drugs, diflusinal and loperamide, with Kd values in the low micromolar range, that block the human ClC-Kb channel and that could be used as starting point to design novel chemical probes for this potential therapeutic target.

Published
2017
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4. Deficiency of Carbonic Anhydrase II Results in a Urinary Concentrating Defect

Author

Devishree Krishnan, Wanling Pan, Megan R. Beggs, Francesco Trepiccione, Régine Chambrey, Dominique Eladari, Emmanuelle Cordat, Henrik Dimke, and R. Todd Alexander

Subjects
carbonic anhydrase II, polyuria, urine concentration, aquaporin-1, metabolic, Physiology, QP1-981
Abstract

Carbonic anhydrase II (CAII) is expressed along the nephron where it interacts with a number of transport proteins augmenting their activity. Aquaporin-1 (AQP1) interacts with CAII to increase water flux through the water channel. Both CAII and aquaporin-1 are expressed in the thin descending limb (TDL); however, the physiological role of a CAII-AQP1 interaction in this nephron segment is not known. To determine if CAII was required for urinary concentration, we studied water handling in CAII-deficient mice. CAII-deficient mice demonstrate polyuria and polydipsia as well as an alkaline urine and bicarbonaturia, consistent with a type III renal tubular acidosis. Natriuresis and hypercalciuria cause polyuria, however, CAII-deficient mice did not have increased urinary sodium nor calcium excretion. Further examination revealed dilute urine in the CAII-deficient mice. Urinary concentration remained reduced in CAII-deficient mice relative to wild-type animals even after water deprivation. The renal expression and localization by light microscopy of NKCC2 and aquaporin-2 was not altered. However, CAII-deficient mice had increased renal AQP1 expression. CAII associates with and increases water flux through aquaporin-1. Water flux through aquaporin-1 in the TDL of the loop of Henle is essential to the concentration of urine, as this is required to generate a concentrated medullary interstitium. We therefore measured cortical and medullary interstitial concentration in wild-type and CAII-deficient mice. Mice lacking CAII had equivalent cortical interstitial osmolarity to wild-type mice: however, they had reduced medullary interstitial osmolarity. We propose therefore that reduced water flux through aquaporin-1 in the TDL in the absence of CAII prevents the generation of a maximally concentrated medullary interstitium. This, in turn, limits urinary concentration in CAII deficient mice.

Published
2018
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5. A mouse model for distal renal tubular acidosis reveals a previously unrecognized role of the V‐ATPase a4 subunit in the proximal tubule

Author

J. Christopher Hennings, Nicolas Picard, Antje K. Huebner, Tobias Stauber, Hannes Maier, Dennis Brown, Thomas J. Jentsch, Rosa Vargas‐Poussou, Dominique Eladari, and Christian A. Hübner

Subjects
deafness, distal renal tubular acidosis, H+‐ATPase, kidney, proteinuria, Medicine (General), R5-920, Genetics, QH426-470
Abstract

Abstract The V‐ATPase is a multisubunit complex that transports protons across membranes. Mutations of its B1 or a4 subunit are associated with distal renal tubular acidosis and deafness. In the kidney, the a4 subunit is expressed in intercalated cells of the distal nephron, where the V‐ATPase controls acid/base secretion, and in proximal tubule cells, where its role is less clear. Here, we report that a4 KO mice suffer not only from severe acidosis but also from proximal tubule dysfunction with defective endocytic trafficking, proteinuria, phosphaturia and accumulation of lysosomal material and we provide evidence that these findings may be also relevant in patients. In the inner ear, the a4 subunit co‐localized with pendrin at the apical side of epithelial cells lining the endolymphatic sac. As a4 KO mice were profoundly deaf and displayed enlarged endolymphatic fluid compartments mirroring the alterations in pendrin KO mice, we propose that pendrin and the proton pump co‐operate in endolymph homeostasis. Thus, our mouse model gives new insights into the divergent functions of the V‐ATPase and the pathophysiology of a4‐related symptoms.

Published
2012
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6. SLC26A4 targeted to the endolymphatic sac rescues hearing and balance in Slc26a4 mutant mice.

Author

Xiangming Li, Joel D Sanneman, Donald G Harbidge, Fei Zhou, Taku Ito, Raoul Nelson, Nicolas Picard, Régine Chambrey, Dominique Eladari, Tracy Miesner, Andrew J Griffith, Daniel C Marcus, and Philine Wangemann

Subjects
Genetics, QH426-470
Abstract

Mutations of SLC26A4 are a common cause of human hearing loss associated with enlargement of the vestibular aqueduct. SLC26A4 encodes pendrin, an anion exchanger expressed in a variety of epithelial cells in the cochlea, the vestibular labyrinth and the endolymphatic sac. Slc26a4 (Δ/Δ) mice are devoid of pendrin and develop a severe enlargement of the membranous labyrinth, fail to acquire hearing and balance, and thereby provide a model for the human phenotype. Here, we generated a transgenic mouse line that expresses human SLC26A4 controlled by the promoter of ATP6V1B1. Crossing this transgene into the Slc26a4 (Δ/Δ) line restored protein expression of pendrin in the endolymphatic sac without inducing detectable expression in the cochlea or the vestibular sensory organs. The transgene prevented abnormal enlargement of the membranous labyrinth, restored a normal endocochlear potential, normal pH gradients between endolymph and perilymph in the cochlea, normal otoconia formation in the vestibular labyrinth and normal sensory functions of hearing and balance. Our study demonstrates that restoration of pendrin to the endolymphatic sac is sufficient to restore normal inner ear function. This finding in conjunction with our previous report that pendrin expression is required for embryonic development but not for the maintenance of hearing opens the prospect that a spatially and temporally limited therapy will restore normal hearing in human patients carrying a variety of mutations of SLC26A4.

Published
2013
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7. Plasma fibroblast growth factor 23 concentration is increased and predicts mortality in patients on the liver-transplant waiting list.

Author

Dominique Prié, Anne Forand, Claire Francoz, Caroline Elie, Isabelle Cohen, Marie Courbebaisse, Dominique Eladari, Didier Lebrec, François Durand, and Gerard Friedlander

Subjects
Medicine, Science
Abstract

High plasma fibroblast growth factor-23 (FGF23) concentration predicts the risk of death and poor outcomes in patients with chronic kidney disease or chronic heart failure. We checked if FGF23 concentration could be modified in patients with end stage liver disease (ESLD) and predict mortality. We measured plasma FGF23 in 200 patients with ESLD registered on a liver transplant waiting list between January 2005 and October 2008. We found that median plasma FGF23 concentration was above normal values in 63% of the patients. Increased FGF23 concentration was not explained by its classical determinants: hyperphosphataemia, increased calcitriol concentration or decreased renal function. FGF23 concentration correlated with the MELD score, serum sodium concentration, and GFR. Forty-six patients died before being transplanted and 135 underwent liver transplantation. We analyzed the prognostic value of FGF23 levels. Mortality was significantly associated with FGF23 levels, the MELD score, serum sodium concentration and glomerular filtration rate. On multivariate analyses only FGF23 concentration was associated with mortality. FGF23 levels were independent of the cause of the liver disease. To determine if the damaged liver can produce FGF23 we measured plasma FGF23 concentration and liver FGF23 mRNA expression in control and diethyl-nitrosamine (DEN)-treated mice. FGF23 plasma levels increased with the apparition of liver lesions in DEN-treated mice and that FGF23 mRNA expression, which was undetectable in the liver of control mice, markedly increased with the development of liver lesions. The correlation between FGF23 plasma concentration and FGF23 mRNA expression in DEN-treated mice suggests that FGF23 production by the liver accounts for the increased plasma FGF23 concentration. In conclusion chronic liver lesions can induce expression of FGF23 mRNA leading to increased FGF23 concentration, which is associated with a higher mortality in patients on a liver-transplant waiting list. In these patients FGF23 concentration was the best predictor of mortality.

Published
2013
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8. Red Blood Cell AE1/Band 3 Transports in Dominant Distal Renal Tubular Acidosis Patients

Author

Bertrand Knebelmann, Sandrine Genetet, Lucie Bessenay, Rosa Vargas-Poussou, Isabelle Mouro-Chanteloup, Dominique Eladari, Lydie Da Costa, Corinne Guitton, Renaud De Lafaille, Jean-Philippe Bertocchio, Julie Galimand, Stephen B. Walsh, Biologie Intégrée du Globule Rouge (BIGR (UMR_S_1134 / U1134)), Institut National de la Transfusion Sanguine [Paris] (INTS)-Université de La Réunion (UR)-Institut National de la Santé et de la Recherche Médicale (INSERM)-CHU Pointe-à-Pitre/Abymes [Guadeloupe] -Université des Antilles (UA)-Université de Paris (UP), Service de Pédiatrie Générale [CHU Clermont-Ferrand], CHU Estaing [Clermont-Ferrand], CHU Clermont-Ferrand-CHU Clermont-Ferrand, Centre de Recherche des Cordeliers (CRC (UMR_S_1138 / U1138)), École pratique des hautes études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut National de la Santé et de la Recherche Médicale (INSERM)-Sorbonne Université (SU)-Université de Paris (UP), Service d'exploration fonctionnelles rénales [CHU La Réunion], and Centre Hospitalier Universitaire de La Réunion (CHU La Réunion)

Subjects
[SDV]Life Sciences [q-bio], 030232 urology & nephrology, hematologic diseases, 030204 cardiovascular system & hematology, lcsh:RC870-923, 03 medical and health sciences, 0302 clinical medicine, Distal renal tubular acidosis, Clinical Research, nephrocalcinosis, parasitic diseases, Extracellular, Medicine, Band 3, Kidney, biology, business.industry, medicine.disease, lcsh:Diseases of the genitourinary system. Urology, Molecular biology, acidosis, renal tubular, Red blood cell, medicine.anatomical_structure, Membrane protein, Nephrology, biology.protein, anion exchange protein 1, erythrocyte, Nephrocalcinosis, business, human activities, Homeostasis, nephrolithiasis
Abstract

Introduction Anion exchanger 1 (AE1) (SLC4A1 gene product) is a membrane protein expressed in both kidney and red blood cells (RBCs): it exchanges extracellular bicarbonate (HCO3–) for intracellular chloride (Cl–) and participates in acid−base homeostasis. AE1 mutations in kidney α-intercalated cells can lead to distal renal tubular acidosis (dRTA). In RBC, AE1 (known as band 3) is also implicated in membrane stability: deletions can cause South Asian ovalocytosis (SAO). Methods We retrospectively collected clinical and biological data from patients harboring dRTA due to a SLC4A1 mutation and analyzed HCO3– and Cl– transports (by stopped-flow spectrophotometry) and expression (by flow cytometry, fluorescence activated cell sorting, and Coomassie blue staining) in RBCs, as well as RBC membrane stability (ektacytometry). Results Fifteen patients were included. All experience nephrolithiasis and/or nephrocalcinosis, 2 had SAO and dRTA (dRTA SAO+), 13 dominant dRTA (dRTA SAO−). The latter did not exert specific RBC membrane anomalies. Both HCO3– and Cl– transports were lower in patients with dRTA SAO+ than in those with dRTA SAO− or controls. Using 3 different extracellular probes, we report a decreased expression (by 52%, P < 0.05) in dRTA SAO+ patients by fluorescence activated cell sorting, whereas total amount of protein was not affected. Conclusion Band 3 transport function and expression in RBCs from dRTA SAO− patients is normal. However, in SAO RBCs, impaired conformation of AE1/band 3 corresponds to an impaired function. Thus, the driver of acid−base defect during dominant dRTA is probably an impaired membrane expression., Graphical abstract

Published
2020

9. A mouse model of pseudohypoaldosteronism type II reveals a novel mechanism of renal tubular acidosis

Author

Jennifer Baraka-Vidot, María Chávez-Canales, Régine Chambrey, Juliette Hadchouel, Alexia Pillot, Maximilien Jayat, Yusuke Kumai, Karen I. López-Cayuqueo, Christelle Soukaseum, Dominique Eladari, Xavier Jeunemaitre, Francesco Trepiccione, Véronique Baudrie, Cara Büsst, Pascal Houillier, Paris-Centre de Recherche Cardiovasculaire (PARCC - UMR-S U970), Université Paris Descartes - Paris 5 (UPD5)-Hôpital Européen Georges Pompidou [APHP] (HEGP), Hôpitaux Universitaires Paris Ouest - Hôpitaux Universitaires Île de France Ouest (HUPO)-Assistance publique - Hôpitaux de Paris (AP-HP) (APHP)-Hôpitaux Universitaires Paris Ouest - Hôpitaux Universitaires Île de France Ouest (HUPO)-Assistance publique - Hôpitaux de Paris (AP-HP) (APHP)-Institut National de la Santé et de la Recherche Médicale (INSERM), Unité des maladies rénales et métaboliques [Hôpital Européen Georges-Pompidou - APHP], Hôpital Européen Georges Pompidou [APHP] (HEGP), Hôpitaux Universitaires Paris Ouest - Hôpitaux Universitaires Île de France Ouest (HUPO)-Assistance publique - Hôpitaux de Paris (AP-HP) (APHP)-Hôpitaux Universitaires Paris Ouest - Hôpitaux Universitaires Île de France Ouest (HUPO)-Assistance publique - Hôpitaux de Paris (AP-HP) (APHP), Centre de Recherche des Cordeliers (CRC (UMR_S 872)), Université Pierre et Marie Curie - Paris 6 (UPMC)-Université Paris Descartes - Paris 5 (UPD5)-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS), Groupe d'Etude sur l'Inflammation Chronique et l'Obésité (GEICO), Université de La Réunion (UR), University of Edinburgh, López-Cayuqueo, Karen I, Chavez-Canales, Maria, Pillot, Alexia, Houillier, Pascal, Jayat, Maximilien, Baraka-Vidot, Jennifer, Trepiccione, Francesco, Baudrie, Véronique, Büsst, Cara, Soukaseum, Christelle, Kumai, Yusuke, Jeunemaître, Xavier, Hadchouel, Juliette, Eladari, Dominique, Chambrey, Régine, Université Paris Descartes - Paris 5 (UPD5)-Institut National de la Santé et de la Recherche Médicale (INSERM)-Hôpital Européen Georges Pompidou [APHP] (HEGP), Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP)-Hôpitaux Universitaires Paris Ouest - Hôpitaux Universitaires Île de France Ouest (HUPO)-Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP)-Hôpitaux Universitaires Paris Ouest - Hôpitaux Universitaires Île de France Ouest (HUPO), and Université Paris Descartes - Paris 5 (UPD5)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS)

Subjects
0301 basic medicine, Male, pendrin, Pseudohypoaldosteronism, [SDV]Life Sciences [q-bio], 030232 urology & nephrology, Sodium Chloride, Renal tubular acidosis, Gene Knockout Techniques, Mice, 0302 clinical medicine, ComputingMilieux_MISCELLANEOUS, biology, Chemistry, Reabsorption, Acidosis, Renal Tubular, WNK4, Up-Regulation, medicine.anatomical_structure, Nephrology, Sulfate Transporters, renal tubular acidosi, medicine.medical_specialty, hypertension, Mutation, Missense, Mice, Transgenic, Protein Serine-Threonine Kinases, 03 medical and health sciences, intercalated cell, Internal medicine, medicine, Animals, Humans, [SDV.BBM]Life Sciences [q-bio]/Biochemistry, Molecular Biology, Distal convoluted tubule, Kidney Tubules, Collecting, Sodium-Bicarbonate Symporters, Metabolic acidosis, Pendrin, medicine.disease, Mice, Inbred C57BL, Disease Models, Animal, Renal Elimination, 030104 developmental biology, Endocrinology, Gordon syndrome, biology.protein, Potassium, familial hyperkalemic hypertension, Homeostasis
Abstract

Pseudohypoaldosteronism type II (PHAII) is a genetic disease characterized by association of hyperkalemia, hyperchloremic metabolic acidosis, hypertension, low renin, and high sensitivity to thiazide diuretics. It is caused by mutations in the WNK1, WNK4, KLHL3 or CUL3 gene. There is strong evidence that excessive sodium chloride reabsorption by the sodium chloride cotransporter NCC in the distal convoluted tubule is involved. WNK4 is expressed not only in distal convoluted tubule cells but also in β-intercalated cells of the cortical collecting duct. These latter cells exchange intracellular bicarbonate for external chloride through pendrin, and therefore, account for renal base excretion. However, these cells can also mediate thiazide-sensitive sodium chloride absorption when the pendrin-dependent apical chloride influx is coupled to apical sodium influx by the sodium-driven chloride/bicarbonate exchanger. Here we determine whether this system is involved in the pathogenesis of PHAII. Renal pendrin activity was markedly increased in a mouse model carrying a WNK4 missense mutation (Q562E) previously identified in patients with PHAII. The upregulation of pendrin led to an increase in thiazide-sensitive sodium chloride absorption by the cortical collecting duct, and it caused metabolic acidosis. The function of apical potassium channels was altered in this model, and hyperkalemia was fully corrected by pendrin genetic ablation. Thus, we demonstrate an important contribution of pendrin in renal regulation of sodium chloride, potassium and acid-base homeostasis and in the pathophysiology of PHAII. Furthermore, we identify renal distal bicarbonate secretion as a novel mechanism of renal tubular acidosis. Pseudohypoaldosteronism type II (PHAII) is a genetic disease characterized by association of hyperkalemia, hyperchloremic metabolic acidosis, hypertension, low renin, and high sensitivity to thiazide diuretics. It is caused by mutations in the WNK1, WNK4, KLHL3 or CUL3 gene. There is strong evidence that excessive sodium chloride reabsorption by the sodium chloride cotransporter NCC in the distal convoluted tubule is involved. WNK4 is expressed not only in distal convoluted tubule cells but also in beta-intercalated cells of the cortical collecting duct. These latter cells exchange intracellular bicarbonate for external chloride through pendrin, and therefore, account for renal base excretion. However, these cells can also mediate thiazide-sensitive sodium chloride absorption when the pendrin-dependent apical chloride influx is coupled to apical sodium influx by the sodium-driven chloride/bicarbonate exchanger. Here we determine whether this system is involved in the pathogenesis of PHAII. Renal pendrin activity was markedly increased in a mouse model carrying a WNK4 missense mutation (Q562E) previously identified in patients with PHAII. The upregulation of pendrin led to an increase in thiazide-sensitive sodium chloride absorption by the cortical collecting duct, and it caused metabolic acidosis. The function of apical potassium channels was altered in this model, and hyperkalemia was fully corrected by pendrin genetic ablation. Thus, we demonstrate an important contribution of pendrin in renal regulation of sodium chloride, potassium and acid-base homeostasis and in the pathophysiology of PHAII. Furthermore, we identify renal distal bicarbonate secretion as a novel mechanism of renal tubular acidosis.

Published
2018

10. Intercalated Cell Depletion and Vacuolar H + -ATPase Mistargeting in an Ae1 R607H Knockin Model

Author

Francesco Trepiccione, Seth L. Alper, Nicolas Picard, Emmanuelle Cordat, A.K.M. Shahid Ullah, Bettina Serbin, J. Christopher Hennings, Teodor G. Păunescu, Diane E. Capen, Dominique Eladari, Rizwan Mumtaz, Dennis Brown, Christian A. Hübner, Isabelle Mouro-Chanteloup, Rawad Lashhab, Carsten A. Wagner, Antje K. Huebner, Institute of Human Genetics, Jena University Hospital, Friedrich Schiller University, Jena, Germany, Paris-Centre de Recherche Cardiovasculaire (PARCC - UMR-S U970), Hôpital Européen Georges Pompidou [APHP] (HEGP), Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP)-Hôpitaux Universitaires Paris Ouest - Hôpitaux Universitaires Île de France Ouest (HUPO)-Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP)-Hôpitaux Universitaires Paris Ouest - Hôpitaux Universitaires Île de France Ouest (HUPO)-Université Paris Descartes - Paris 5 (UPD5)-Institut National de la Santé et de la Recherche Médicale (INSERM), Department of Cardio-Thoracic and Respiratory Science, Second University of Naples, Naples, Italy, Laboratoire de Biologie Tissulaire et d'ingénierie Thérapeutique UMR 5305 (LBTI), Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS), Department of Physiology, University of Alberta, Edmonton, Alberta, Canada, Center for Systems Biology, Program in Membrane Biology and Division of Nephrology, Massachusetts General Hospital, Beth Israel Deaconess Medical Center [Boston] (BIDMC), Harvard Medical School [Boston] (HMS)-Harvard Medical School [Boston] (HMS), Institut National de la Transfusion Sanguine [Paris] (INTS), Nephrology Division and Vascular Biology Research Center, Beth Israel DeaconessMedical Center, Department of Medicine, HarvardMedical School, Boston,Massachusetts, Institute of Physiology, University of Zurich, Zurich, Switzerland, Diabète athérothrombose et thérapies Réunion Océan Indien (DéTROI), Institut National de la Santé et de la Recherche Médicale (INSERM)-Université de La Réunion (UR), Picard, Nicolas, University of Alberta, Université de La Réunion (UR)-Institut National de la Santé et de la Recherche Médicale (INSERM), University of Zurich, Eladari, Dominique, Université Paris Descartes - Paris 5 (UPD5)-Hôpital Européen Georges Pompidou [APHP] (HEGP), Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP)-Hôpitaux Universitaires Paris Ouest - Hôpitaux Universitaires Île de France Ouest (HUPO)-Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP)-Hôpitaux Universitaires Paris Ouest - Hôpitaux Universitaires Île de France Ouest (HUPO)-Institut National de la Santé et de la Recherche Médicale (INSERM), Centre de Recherche des Cordeliers (CRC), Université Pierre et Marie Curie - Paris 6 (UPMC)-École pratique des hautes études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Université Paris Descartes - Paris 5 (UPD5)-Institut National de la Santé et de la Recherche Médicale (INSERM), Laboratoire d'Excellence : Biogenèse et pathologies du globule rouge (Labex Gr-Ex), Université Paris Diderot - Paris 7 (UPD7)-Université Sorbonne Paris Cité (USPC)-Institut National de la Santé et de la Recherche Médicale (INSERM), Service de Physiologie Explorations Fonctionnelles Rénales, Centre Hospitalier Universitaire de La Réunion (CHU La Réunion), Mumtaz, Rizwan, Trepiccione, Francesco, Hennings, J. Christopher, Huebner, Antje K, Serbin, Bettina, Picard, Nicola, Ullah, A. K. M. Shahid, Păunescu, Teodor G, Capen, Diane E, Lashhab, Rawad M, Mouro Chanteloup, Isabelle, Alper, Seth L, Wagner, Carsten A, Cordat, Emmanuelle, Brown, Denni, Hübner, Christian A., Paris-Centre de Recherche Cardiovasculaire ( PARCC - U970 ), Hôpital Européen Georges Pompidou [APHP] ( HEGP ) -Université Paris Descartes - Paris 5 ( UPD5 ) -Institut National de la Santé et de la Recherche Médicale ( INSERM ), Centre de Recherche des Cordeliers ( CRC ), Université Paris Diderot - Paris 7 ( UPD7 ) -École pratique des hautes études ( EPHE ) -Université Pierre et Marie Curie - Paris 6 ( UPMC ) -Université Paris Descartes - Paris 5 ( UPD5 ) -Institut National de la Santé et de la Recherche Médicale ( INSERM ), Center for Systems Biology, Program in Membrane Biology and Division of Nephrology, Massachusetts General Hospital and ††Nephrology Division and Vascular Biology Research Center, Beth Israel DeaconessMedical Center, Department of Medicine, HarvardMedical School, Boston,Massachusetts, Institut National de la Transfusion Sanguine, Institut National de la Santé et de la Recherche Médicale, Unité Mixte de Recherche en Santé 1134, Laboratory of Excellence Globule Rouge- Excellence, Paris Diderot University, Paris, France, Centre Hospitalier Universitaire de La Réunion ( CHU La Réunion ), Diabète athérothrombose et thérapies Réunion Océan Indien ( DéTROI ), Université de la Réunion ( UR ) -Institut National de la Santé et de la Recherche Médicale ( INSERM ), Hôpitaux Universitaires Paris Ouest - Hôpitaux Universitaires Île de France Ouest (HUPO)-Assistance publique - Hôpitaux de Paris (AP-HP) (APHP)-Hôpitaux Universitaires Paris Ouest - Hôpitaux Universitaires Île de France Ouest (HUPO)-Assistance publique - Hôpitaux de Paris (AP-HP) (APHP)-Institut National de la Santé et de la Recherche Médicale (INSERM), and Université Paris Diderot - Paris 7 (UPD7)-École pratique des hautes études (EPHE)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Université Paris Descartes - Paris 5 (UPD5)-Institut National de la Santé et de la Recherche Médicale (INSERM)

Subjects
Male, 0301 basic medicine, distal tubule, Vacuolar Proton-Translocating ATPases, chronic metabolic acidosis, ATPase, [SDV]Life Sciences [q-bio], Mutant, 030232 urology & nephrology, 610 Medicine & health, Biology, Models, Biological, 10052 Institute of Physiology, Cell & Transport Physiology, ion transport, Mice, 03 medical and health sciences, 0302 clinical medicine, Distal renal tubular acidosis, Mutant protein, Anion Exchange Protein 1, Erythrocyte, medicine, Secretion, Intercalated Cell, Kidney Tubules, Collecting, 2727 Nephrology, [ SDV ] Life Sciences [q-bio], chronic metabolic acidosi, Animal, genetic renal disease, Acidosis, Renal Tubular, General Medicine, medicine.disease, Cell biology, [SDV] Life Sciences [q-bio], transgenic mouse, 030104 developmental biology, Biochemistry, Nephrology, biology.protein, 570 Life sciences, biology, Cotransporter, Intracellular
Abstract

International audience; Distal nephron acid secretion is mediated by highly specialized type A intercalated cells (A-ICs), which contain vacuolar H +-ATPase (V-type ATPase)-rich vesicles that fuse with the apical plasma membrane on demand. Intra-cellular bicarbonate generated by luminal H + secretion is removed by the basolateral anion-exchanger AE1. Chronically reduced renal acid excretion in distal renal tubular acidosis (dRTA) may lead to nephrocalcinosis and renal failure. Studies in MDCK monolayers led to the proposal of a dominant-negative trafficking mechanism to explain AE1-associated dominant dRTA. To test this hypothesis in vivo, we generated an Ae1 R607H knockin mouse, which corresponds to the most common dominant dRTA mutation in human AE1, R589H. Compared with wild-type mice, heterozygous and homozygous R607H knockin mice displayed incomplete dRTA characterized by compensatory upregulation of the Na + /HCO 3 2 cotransporter NBCn1. Red blood cell Ae1-mediated anion-exchange activity and surface polypeptide expression did not change. Mutant mice expressed far less Ae1 in A-ICs, but basolateral targeting of the mutant protein was preserved. Notably, mutant mice also exhibited reduced expression of V-type ATPase and compromised targeting of this proton pump to the plasma membrane upon acid challenge. Accumulation of p62-and ubiquitin-positive material in A-ICs of knockin mice suggested a defect in the degradative pathway, which may explain the observed loss of A-ICs. R607H knockin did not affect type B intercalated cells. We propose that reduced basolateral anion-exchange activity in A-ICs inhibits trafficking and regulation of V-type ATPase, compromising luminal H + secretion and possibly lysosomal acidification.

Published
2017

11. The ClC-K2 Chloride Channel Is Critical for Salt Handling in the Distal Nephron

Author

Yohan Bignon, Nicolas Picard, Régine Chambrey, Antje K. Huebner, J. Christopher Hennings, Olga Andrini, Mathilde Keck, Marc Paulais, Thomas J. Jentsch, Dominique Eladari, Nicolas Cornière, Christian A. Hübner, Jacques Teulon, Irma Karen Lopez Cayuqueo, Friedrich-Schiller-Universität Jena, Centre de Recherche des Cordeliers (CRC), Université Paris Diderot - Paris 7 (UPD7)-École pratique des hautes études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Université Paris Descartes - Paris 5 (UPD5)-Institut National de la Santé et de la Recherche Médicale (INSERM), Paris-Centre de Recherche Cardiovasculaire (PARCC - UMR-S U970), Hôpital Européen Georges Pompidou [APHP] (HEGP), Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP)-Hôpitaux Universitaires Paris Ouest - Hôpitaux Universitaires Île de France Ouest (HUPO)-Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP)-Hôpitaux Universitaires Paris Ouest - Hôpitaux Universitaires Île de France Ouest (HUPO)-Université Paris Descartes - Paris 5 (UPD5)-Institut National de la Santé et de la Recherche Médicale (INSERM), Centro de Estudios Científicos (CECs), Centre Hospitalier Universitaire de La Réunion (CHU La Réunion), Leibniz Forschungsinstitut für Molekulare Pharmakolgie = Leibniz Institute for Molecular Pharmacology [Berlin, Allemagne] (FMP), Leibniz Association, Leibniz-Institut für Molekulare Pharmakologie, Zentrum fuer Molekulare Neurobiologie, Universität Hamburg (UHH)-Institut für Molekulare Neuropathobiologie, Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP)-Hôpitaux Universitaires Paris Ouest - Hôpitaux Universitaires Île de France Ouest (HUPO), Keck, Mathilde, Institute of Human Genetics, Jena University Hospital, Friedrich Schiller University, Jena, Germany, Centre de Recherche des Cordeliers (CRC (UMR_S_1138 / U1138)), École pratique des hautes études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut National de la Santé et de la Recherche Médicale (INSERM)-Sorbonne Université (SU)-Université Paris Cité (UPCité), Centro de Estudios Científicos, Valdivia, Centre hospitalier Félix-Guyon [Saint-Denis, La Réunion], Université Paris Cité - UFR Médecine [Santé] (UPCité UFR Médecine), Université Paris Cité (UPCité), Centre National de la Recherche Scientifique (CNRS), Physiologie et pharmacologie vasculaire et rénale, IFR58-Université Paris Descartes - Paris 5 (UPD5)-Institut National de la Santé et de la Recherche Médicale (INSERM), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut National de la Santé et de la Recherche Médicale (INSERM)-Sorbonne Université (SU)-Université de Paris (UP), Université Paris Descartes - Paris 5 (UPD5)-Institut National de la Santé et de la Recherche Médicale (INSERM)-Hôpital Européen Georges Pompidou [APHP] (HEGP), Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP)-Hôpitaux Universitaires Paris Ouest - Hôpitaux Universitaires Île de France Ouest (HUPO)-Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP)-Hôpitaux Universitaires Paris Ouest - Hôpitaux Universitaires Île de France Ouest (HUPO), Université de Paris - UFR Médecine Paris Centre [Santé] (UP Médecine Paris Centre), and Université de Paris (UP)

Subjects
0301 basic medicine, medicine.medical_specialty, Sodium Chloride Symporter Inhibitors, [SDV]Life Sciences [q-bio], Anion Transport Proteins, 030232 urology & nephrology, Metabolic alkalosis, Sodium Chloride, Bartter syndrome, [SDV.MHEP.UN]Life Sciences [q-bio]/Human health and pathology/Urology and Nephrology, Mice, 03 medical and health sciences, 0302 clinical medicine, Chloride Channels, Furosemide, Internal medicine, medicine, [SDV.MHEP.PHY]Life Sciences [q-bio]/Human health and pathology/Tissues and Organs [q-bio.TO], Bartter-s syndrome, chloride channels, ion transport, transgenic mouse, Animals, Distal convoluted tubule, Diuretics, ComputingMilieux_MISCELLANEOUS, Mice, Knockout, business.industry, urogenital system, [SDV.BBM.BM]Life Sciences [q-bio]/Biochemistry, Molecular Biology/Molecular biology, Nephrons, General Medicine, medicine.disease, [SDV] Life Sciences [q-bio], [SDV.BBM.BP]Life Sciences [q-bio]/Biochemistry, Molecular Biology/Biophysics, Bartter's syndrome, Basic Research, 030104 developmental biology, Endocrinology, medicine.anatomical_structure, Nephrology, Chloride channel, business, Cotransporter, Homeostasis, medicine.drug
Abstract

International audience; Chloride transport by the renal tubule is critical for blood pressure (BP), acid-base, and potassium homeostasis. Chloride uptake from the urinary fluid is mediated by various apical transporters, whereas basolateral chloride exit is thought to be mediated by ClC-Ka/K1 and ClC-Kb/K2, two chloride channels from the ClC family, or by KCl cotransporters from the SLC12 gene family. Nevertheless, the localization and role of ClC-K channels is not fully resolved. Because inactivating mutations in ClC-Kb/K2 cause Bartter syndrome, a disease that mimics the effects of the loop diuretic furosemide, ClC-Kb/K2 is assumed to have a critical role in salt handling by the thick ascending limb. To dissect the role of this channel in detail, we generated a mouse model with a targeted disruption of the murine ortholog ClC-K2. Mutant mice developed a Bartter syndrome phenotype, characterized by renal salt loss, marked hypokalemia, and metabolic alkalosis. Patch-clamp analysis of tubules isolated from knockout (KO) mice suggested that ClC-K2 is the main basolateral chloride channel in the thick ascending limb and in the aldosterone-sensitive distal nephron. Accordingly, ClC-K2 KO mice did not exhibit the natriuretic response to furosemide and exhibited a severely blunted response to thiazide. We conclude that ClC-Kb/K2 is critical for salt absorption not only by the thick ascending limb, but also by the distal convoluted tubule.

Published
2017

12. Acute genetic ablation of pendrin lowers blood pressure in mice

Author

Philine Wangemann, Régine Chambrey, Dominique Eladari, Francesco Trepiccione, Véronique Baudrie, Jacques Teulon, Juliette Hadchouel, Andrew J. Griffith, Bruno O. Villoutreix, Yoon Byung Choi, Christelle Soukaseum, Nicolas Cornière, Yusuke Kumai, Trepiccione, Francesco, Soukaseum, Christelle, Baudrie, Veronique, Kumai, Yusuke, Teulon, Jacque, Villoutreix, Bruno, Cornière, Nicola, Wangemann, Philine, Griffith, Andrew J, Byung Choi, Yoon, Hadchouel, Juliette, Chambrey, Regine, Eladari, Dominique, Paris-Centre de Recherche Cardiovasculaire (PARCC (UMR_S 970/ U970)), Hôpital Européen Georges Pompidou [APHP] (HEGP), Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP)-Hôpitaux Universitaires Paris Ouest - Hôpitaux Universitaires Île de France Ouest (HUPO)-Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP)-Hôpitaux Universitaires Paris Ouest - Hôpitaux Universitaires Île de France Ouest (HUPO)-Institut National de la Santé et de la Recherche Médicale (INSERM)-Université Paris Cité (UPCité), Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP)-Hôpitaux Universitaires Paris Ouest - Hôpitaux Universitaires Île de France Ouest (HUPO), Centre de Recherche des Cordeliers (CRC (UMR_S_1138 / U1138)), École pratique des hautes études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut National de la Santé et de la Recherche Médicale (INSERM)-Sorbonne Université (SU)-Université Paris Cité (UPCité), Molécules Thérapeutiques in silico (MTI), Université Paris Diderot - Paris 7 (UPD7)-Institut National de la Santé et de la Recherche Médicale (INSERM), Centre hospitalier Félix-Guyon [Saint-Denis, La Réunion], Kansas State University, and National Institutes of Health [Bethesda] (NIH)

Subjects
Male, Genetically modified mouse, medicine.medical_specialty, [SDV.MHEP.PHY] Life Sciences [q-bio]/Human health and pathology/Tissues and Organs [q-bio.TO], Anion Transport Proteins, 030232 urology & nephrology, Blood Pressure, Mice, Transgenic, 030204 cardiovascular system & hematology, Chloride, Mice, 03 medical and health sciences, 0302 clinical medicine, [SDV.MHEP.CSC]Life Sciences [q-bio]/Human health and pathology/Cardiology and cardiovascular system, In vivo, Internal medicine, Extracellular fluid, [SDV.MHEP.PHY]Life Sciences [q-bio]/Human health and pathology/Tissues and Organs [q-bio.TO], medicine, otorhinolaryngologic diseases, Animals, Diuretic, Pendrin, Transplantation, Kidney, biology, business.industry, Reabsorption, Original Articles, diuretics, Connecting tubule, [SDV.MHEP.CSC] Life Sciences [q-bio]/Human health and pathology/Cardiology and cardiovascular system, Endocrinology, Blood pressure, medicine.anatomical_structure, Sulfate Transporters, Nephrology, intercalated cells, Hypertension, biology.protein, business, Intercalated cell
Abstract

International audience; Background: Pendrin, the chloride/bicarbonate exchanger of β-intercalated cells of the renal connecting tubule and the collecting duct, plays a key role in NaCl reabsorption by the distal nephron. Therefore, pendrin may be important for the control of extracellular fluid volume and blood pressure.Methods: Here, we have used a genetic mouse model in which the expression of pendrin can be switched-on in vivo by the administration of doxycycline. Pendrin can also be rapidly removed when doxycycline administration is discontinued. Therefore, our genetic strategy allows us to test selectively the acute effects of loss of pendrin function.Results: We show that acute loss of pendrin leads to a significant decrease of blood pressure. In addition, acute ablation of pendrin did not alter significantly the acid-base status or blood K + concentration.Conclusion: By using a transgenic mouse model, avoiding off-target effects related to pharmacological compounds, this study suggests that pendrin could be a novel target to treat hypertension.

Published
2017

13. Double Knockout of the Na + -Driven Cl − /HCO 3 − Exchanger and Na + /Cl − Cotransporter Induces Hypokalemia and Volume Depletion

Author

Régine Chambrey, Christian A. Hübner, Anne Sinning, Maximilien Jayat, Karen I. López-Cayuqueo, Stéphanie Baron, R. Todd Alexander, Nicolas Cornière, Juliette Hadchouel, Dominique Eladari, Nikita Radionov, Francesco Trepiccione, Friedrich-Schiller-Universität = Friedrich Schiller University Jena [Jena, Germany], Paris-Centre de Recherche Cardiovasculaire (PARCC (UMR_S 970/ U970)), Hôpital Européen Georges Pompidou [APHP] (HEGP), Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP)-Hôpitaux Universitaires Paris Ouest - Hôpitaux Universitaires Île de France Ouest (HUPO)-Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP)-Hôpitaux Universitaires Paris Ouest - Hôpitaux Universitaires Île de France Ouest (HUPO)-Institut National de la Santé et de la Recherche Médicale (INSERM)-Université Paris Cité (UPCité), Université Paris Descartes - Faculté de Médecine (UPD5 Médecine), Université Paris Descartes - Paris 5 (UPD5), Centro de Estudios Científicos (CECs), Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP)-Hôpitaux Universitaires Paris Ouest - Hôpitaux Universitaires Île de France Ouest (HUPO), Centre Hospitalier Universitaire de La Réunion (CHU La Réunion), University of Alberta, Centre National de la Recherche Scientifique (CNRS), Hadchouel, Juliette, Sinning, Anne, Radionov, Nikita, Trepiccione, Francesco, López Cayuqueo, Karen I, Jayat, Maximilien, Baron, Stéphanie, Cornière, Nicola, Alexander, R. Todd, Eladari, Dominique, Hübner, Christian A, and Chambrey, Régine

Subjects
0301 basic medicine, Epithelial sodium channel, medicine.medical_specialty, hypertension, [SDV.MHEP.PHY] Life Sciences [q-bio]/Human health and pathology/Tissues and Organs [q-bio.TO], diuretic, 030232 urology & nephrology, Mice, 03 medical and health sciences, 0302 clinical medicine, Downregulation and upregulation, [SDV.MHEP.CSC]Life Sciences [q-bio]/Human health and pathology/Cardiology and cardiovascular system, In vivo, Internal medicine, medicine, hypokalemia, [SDV.MHEP.PHY]Life Sciences [q-bio]/Human health and pathology/Tissues and Organs [q-bio.TO], Animals, Chloride-Bicarbonate Antiporters, Thiazide, Mice, Knockout, Blood Volume, biology, Animal, Chemistry, Chloride-Bicarbonate Antiporter, General Medicine, Pendrin, Hypokalemia, diuretics, Up-Regulation, [SDV.MHEP.CSC] Life Sciences [q-bio]/Human health and pathology/Cardiology and cardiovascular system, Basic Research, 030104 developmental biology, Endocrinology, Nephrology, biology.protein, medicine.symptom, Cotransporter, Homeostasis, medicine.drug
Abstract

International audience; We recently described a novel thiazide-sensitive electroneutral NaCl transport mechanism resulting from the parallel operation of the Cl-/HCO3- exchanger pendrin and the Na+-driven Cl-/2HCO3- exchanger (NDCBE) in β-intercalated cells of the collecting duct. Although a role for pendrin in maintaining Na+ balance, intravascular volume, and BP is well supported, there is no in vivo evidence for the role of NDCBE in maintaining Na+ balance. Here, we show that deletion of NDCBE in mice caused only subtle perturbations of Na+ homeostasis and provide evidence that the Na+/Cl- cotransporter (NCC) compensated for the inactivation of NDCBE. To unmask the role of NDCBE, we generated Ndcbe/Ncc double-knockout (dKO) mice. On a normal salt diet, dKO and single-knockout mice exhibited similar activation of the renin-angiotensin-aldosterone system, whereas only dKO mice displayed a lower blood K+ concentration. Furthermore, dKO mice displayed upregulation of the epithelial sodium channel (ENaC) and the Ca2+-activated K+ channel BKCa. During NaCl depletion, only dKO mice developed marked intravascular volume contraction, despite dramatically increased renin activity. Notably, the increase in aldosterone levels expected on NaCl depletion was attenuated in dKO mice, and single-knockout and dKO mice had similar blood K+ concentrations under this condition. In conclusion, NDCBE is necessary for maintaining sodium balance and intravascular volume during salt depletion or NCC inactivation in mice. Furthermore, NDCBE has an important role in the prevention of hypokalemia. Because NCC and NDCBE are both thiazide targets, the combined inhibition of NCC and the NDCBE/pendrin system may explain thiazide-induced hypokalemia in some patients.

Published
2017

14. In silico model of the human ClC-Kb chloride channel: pore mapping, biostructural pathology and drug screening

Author

Naziha Bakouh, Dominique Eladari, Maxime Louet, Maria A. Miteva, Bruno O. Villoutreix, Yohan Bignon, Gabrielle Planelles, Jacques Teulon, Sara Bitam, David Lagorce, Molécules Thérapeutiques in silico (MTI), Université Paris Diderot - Paris 7 (UPD7)-Institut National de la Santé et de la Recherche Médicale (INSERM), Centre de Recherche des Cordeliers (CRC), Université Paris Diderot - Paris 7 (UPD7)-École pratique des hautes études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Université Paris Descartes - Paris 5 (UPD5)-Institut National de la Santé et de la Recherche Médicale (INSERM), Diabète athérothrombose et thérapies Réunion Océan Indien (DéTROI), Institut National de la Santé et de la Recherche Médicale (INSERM)-Université de La Réunion (UR), Service d’Explorations Fonctionnelles Rénales, Centre hospitalier Félix-Guyon [Saint-Denis, La Réunion], HAL UPMC, Gestionnaire, Université Pierre et Marie Curie - Paris 6 (UPMC)-École pratique des hautes études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Université Paris Descartes - Paris 5 (UPD5)-Institut National de la Santé et de la Recherche Médicale (INSERM), Université de La Réunion (UR)-Institut National de la Santé et de la Recherche Médicale (INSERM), Molécules Thérapeutique in silico, Recherche de molécules à visée thérapeutique par approches In Silico ( MTI ), Université Paris Diderot - Paris 7 ( UPD7 ) -Institut National de la Santé et de la Recherche Médicale ( INSERM ), Centre de Recherche des Cordeliers ( CRC ), Université Paris Diderot - Paris 7 ( UPD7 ) -École pratique des hautes études ( EPHE ) -Université Pierre et Marie Curie - Paris 6 ( UPMC ) -Université Paris Descartes - Paris 5 ( UPD5 ) -Institut National de la Santé et de la Recherche Médicale ( INSERM ), Diabète athérothrombose et thérapies Réunion Océan Indien ( DéTROI ), Institut National de la Santé et de la Recherche Médicale ( INSERM ) -Université de la Réunion ( UR ), CHU Félix Guyon, and Université Pierre et Marie Curie - Paris 6 (UPMC)-École Pratique des Hautes Études (EPHE)

Subjects
0301 basic medicine, Models, Molecular, Quantitative structure–activity relationship, [SDV.BBM.BS] Life Sciences [q-bio]/Biochemistry, Molecular Biology/Structural Biology [q-bio.BM], Protein Conformation, Science, [CHIM.THER] Chemical Sciences/Medicinal Chemistry, In silico, Drug Evaluation, Preclinical, Quantitative Structure-Activity Relationship, Computational biology, [CHIM.THER]Chemical Sciences/Medicinal Chemistry, Pharmacology, Bartter syndrome, Article, Membrane Potentials, 03 medical and health sciences, Protein structure, Chlorides, Chloride Channels, medicine, Animals, Humans, Amino Acid Sequence, Membrane potential, Virtual screening, Multidisciplinary, Molecular Structure, [SDV.BBM.BS]Life Sciences [q-bio]/Biochemistry, Molecular Biology/Structural Biology [q-bio.BM], Chemistry, [ CHIM.THER ] Chemical Sciences/Medicinal Chemistry, medicine.disease, 3. Good health, Drug repositioning, 030104 developmental biology, Mutation, Chloride channel, Medicine, Cattle, Disease Susceptibility, Ion Channel Gating, [ SDV.BBM.BS ] Life Sciences [q-bio]/Biochemistry, Molecular Biology/Biomolecules [q-bio.BM]
Abstract

The human ClC-Kb channel plays a key role in exporting chloride ions from the cytosol and is known to be involved in Bartter syndrome type 3 when its permeation capacity is decreased. The ClC-Kb channel has been recently proposed as a potential therapeutic target to treat hypertension. In order to gain new insights into the sequence-structure-function relationships of this channel, to investigate possible impacts of amino-acid substitutions, and to design novel inhibitors, we first built a structural model of the human ClC-Kb channel using comparative modeling strategies. We combined in silico and in vitro techniques to analyze amino acids involved in the chloride ion pathway as well as to rationalize the possible role of several clinically observed mutations leading to the Bartter syndrome type 3. Virtual screening and drug repositioning computations were then carried out. We identified six novel molecules, including 2 approved drugs, diflusinal and loperamide, with Kd values in the low micromolar range, that block the human ClC-Kb channel and that could be used as starting point to design novel chemical probes for this potential therapeutic target.

Published
2017

15. Acidosis and Urinary Calcium Excretion:Insights from Genetic Disorders

Author

Emmanuelle Cordat, Régine Chambrey, Henrik Dimke, R. Todd Alexander, and Dominique Eladari

Subjects
0301 basic medicine, medicine.medical_specialty, Calcium/metabolism, Hypercalciuria, 030232 urology & nephrology, chemistry.chemical_element, Bone Diseases/etiology, Acid-Base Imbalance, Calcium, urologic and male genital diseases, Renal tubular acidosis, 03 medical and health sciences, 0302 clinical medicine, Up Front Matters, Internal medicine, medicine, Humans, Acidosis, business.industry, Chronic metabolic acidosis, Kidney Tubules/metabolism, Metabolic acidosis, General Medicine, medicine.disease, Urinary calcium, Nephrocalcinosis, Nephrocalcinosis/etiology, Kidney Tubules, 030104 developmental biology, Endocrinology, chemistry, Nephrology, Acidosis/classification, Hypercalciuria/etiology, Bone Diseases, medicine.symptom, Acid-Base Imbalance/complications, business
Abstract

Metabolic acidosis is associated with increased urinary calcium excretion and related sequelae, including nephrocalcinosis and nephrolithiasis. The increased urinary calcium excretion induced by metabolic acidosis predominantly results from increased mobilization of calcium out of bone and inhibition of calcium transport processes within the renal tubule. The mechanisms whereby acid alters the integrity and stability of bone have been examined extensively in the published literature. Here, after briefly reviewing this literature, we consider the effects of acid on calcium transport in the renal tubule and then discuss why not all gene defects that cause renal tubular acidosis are associated with hypercalciuria and nephrocalcinosis.

Published
2016

16. Renal Atp6ap2/(Pro)renin receptor is required for normal vacuolar H+-ATPase function but not for the renin-angiotensin system

Author

Karen I. López-Cayuqueo, Francesco Trepiccione, Nicolas Picard, Véronique Baudrie, Simon D. Gerber, Florian Grahammer, Pascal Houillier, Dennis Brown, Tobias B. Huber, Dominique Eladari, Teodor G. Păunescu, Matias Simons, R. Todd Alexander, Diane E. Capen, Régine Chambrey, Trepiccione, Francesco, Gerber, Simon D, Grahammer, Florian, López Cayuqueo, Karen I, Baudrie, Véronique, Păunescu, Teodor G, Capen, Diane E, Picard, Nicola, Alexander, R. Todd, Huber, Tobias B, Chambrey, Regine, Brown, Denni, Houillier, Pascal, Eladari, Dominique, Simons, Matias, Paris-Centre de Recherche Cardiovasculaire (PARCC - UMR-S U970), Hôpital Européen Georges Pompidou [APHP] (HEGP), Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP)-Hôpitaux Universitaires Paris Ouest - Hôpitaux Universitaires Île de France Ouest (HUPO)-Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP)-Hôpitaux Universitaires Paris Ouest - Hôpitaux Universitaires Île de France Ouest (HUPO)-Université Paris Descartes - Paris 5 (UPD5)-Institut National de la Santé et de la Recherche Médicale (INSERM), Laboratory for Neutron Scattering and Imaging [Paul Scherrer Institute] (LNS), Paul Scherrer Institute (PSI), Renal Division, Universitäts Klinikum Freiburg = University Medical Center Freiburg (Uniklinik), Centre de Recherche des Cordeliers (CRC (UMR_S 872)), Université Pierre et Marie Curie - Paris 6 (UPMC)-Université Paris Descartes - Paris 5 (UPD5)-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS), Center for Systems Biology, Program in Membrane Biology and Division of Nephrology, Massachusetts General Hospital, Beth Israel Deaconess Medical Center [Boston] (BIDMC), Harvard Medical School [Boston] (HMS)-Harvard Medical School [Boston] (HMS), Centre de Recherche des Cordeliers (CRC (UMR_S_1138 / U1138)), École Pratique des Hautes Études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Université Paris Descartes - Paris 5 (UPD5)-Institut National de la Santé et de la Recherche Médicale (INSERM)-Sorbonne Université (SU), University of Alberta, Renal Division, University Medical Center Freiburg, Freiburg, Germany, Service de Physiologie [Georges-Pompidou], Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP)-Hôpital Européen Georges Pompidou [APHP] (HEGP), Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP)-Hôpitaux Universitaires Paris Ouest - Hôpitaux Universitaires Île de France Ouest (HUPO)-Hôpitaux Universitaires Paris Ouest - Hôpitaux Universitaires Île de France Ouest (HUPO)-Université Paris Descartes - Paris 5 (UPD5), Diabète athérothrombose et thérapies Réunion Océan Indien (DéTROI), Université de La Réunion (UR)-Institut National de la Santé et de la Recherche Médicale (INSERM), Imagine - Institut des maladies génétiques (IMAGINE - U1163), Université Paris Descartes - Paris 5 (UPD5)-Institut National de la Santé et de la Recherche Médicale (INSERM), École pratique des hautes études (EPHE), Picard, Nicolas, Université Paris Descartes - Paris 5 (UPD5)-Institut National de la Santé et de la Recherche Médicale (INSERM)-Hôpital Européen Georges Pompidou [APHP] (HEGP), Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP)-Hôpitaux Universitaires Paris Ouest - Hôpitaux Universitaires Île de France Ouest (HUPO)-Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP)-Hôpitaux Universitaires Paris Ouest - Hôpitaux Universitaires Île de France Ouest (HUPO), Freiburg University Medical Center, Department of Physiology, University of Alberta, Edmonton, Alberta, Canada, and Institut National de la Santé et de la Recherche Médicale (INSERM)-Université de La Réunion (UR)

Subjects
0301 basic medicine, Male, medicine.medical_specialty, Vacuolar Proton-Translocating ATPases, [SDV]Life Sciences [q-bio], Countercurrent multiplication, Receptors, Cell Surface, acidosi, 030204 cardiovascular system & hematology, Medullary interstitium, Biology, Kidney, Cell & Transport Physiology, Renin-Angiotensin System, 03 medical and health sciences, Mice, 0302 clinical medicine, Distal renal tubular acidosis, Internal medicine, Renin–angiotensin system, medicine, Animals, Intercalated Cell, ATP6AP2, urogenital system, balance, General Medicine, medicine.disease, Angiotensin II, [SDV] Life Sciences [q-bio], Proton-Translocating ATPases, 030104 developmental biology, medicine.anatomical_structure, Endocrinology, Nephrology, water-electrolyte, cell biology and structure, Female, acidosis
Abstract

International audience; ATPase H+-transporting lysosomal accessory protein 2 (Atp6ap2), also known as the (pro)renin receptor, is a type 1 transmembrane protein and an accessory subunit of the vacuolar H+-ATPase (V-ATPase) that may also function within the renin-angiotensin system. However, the contribution of Atp6ap2 to renin-angiotensin-dependent functions remains unconfirmed. Using mice with an inducible conditional deletion of Atp6ap2 in mouse renal epithelial cells, we found that decreased V-ATPase expression and activity in the intercalated cells of the collecting duct impaired acid-base regulation by the kidney. In addition, these mice suffered from marked polyuria resistant to desmopressin administration. Immunoblotting revealed downregulation of the medullary Na+-K+-2Cl- cotransporter NKCC2 in these mice compared with wild-type mice, an effect accompanied by a hypotonic medullary interstitium and impaired countercurrent multiplication. This phenotype correlated with strong autophagic defects in epithelial cells of medullary tubules. Notably, cells with high accumulation of the autophagosomal substrate p62 displayed the strongest reduction of NKCC2 expression. Finally, nephron-specific Atp6ap2 depletion did not affect angiotensin II production, angiotensin II-dependent BP regulation, or sodium handling in the kidney. Taken together, our results show that nephron-specific deletion of Atp6ap2 does not affect the renin-angiotensin system but causes a combination of renal concentration defects and distal renal tubular acidosis as a result of impaired V-ATPase activity.

Published
2016

17. SLC26A4 targeted to the endolymphatic sac rescues hearing and balance in Slc26a4 mutant mice

Author

Tracy Miesner, Daniel C. Marcus, Fei Zhou, Joel D. Sanneman, Taku Ito, Donald G. Harbidge, Xiangming Li, Dominique Eladari, Philine Wangemann, Nicolas Picard, Andrew J. Griffith, Régine Chambrey, and Raoul D. Nelson

Subjects
Cancer Research, Vestibular aqueduct, Endolymph, Membranous labyrinth, Gene Expression, Otology, Mice, 0302 clinical medicine, Pregnancy, Morphogenesis, Hearing Disorders, Genetics (clinical), 0303 health sciences, Cell biology, medicine.anatomical_structure, Sulfate Transporters, Medicine, Female, Research Article, Vacuolar Proton-Translocating ATPases, medicine.medical_specialty, lcsh:QH426-470, Endocochlear potential, Anion Transport Proteins, Mice, Transgenic, Biology, Endolymphatic sac, Vestibular Aqueduct, Molecular Genetics, 03 medical and health sciences, Genetic Mutation, Internal medicine, Genetics, medicine, otorhinolaryngologic diseases, Animals, Humans, Inner ear, Hearing Loss, Molecular Biology, Ecology, Evolution, Behavior and Systematics, Cochlea, 030304 developmental biology, Membrane Transport Proteins, Pendrin, lcsh:Genetics, Endocrinology, Otorhinolaryngology, Ear, Inner, Genetics of Disease, Mutation, biology.protein, sense organs, Gene Function, Endolymphatic Sac, 030217 neurology & neurosurgery, Developmental Biology
Abstract

Mutations of SLC26A4 are a common cause of human hearing loss associated with enlargement of the vestibular aqueduct. SLC26A4 encodes pendrin, an anion exchanger expressed in a variety of epithelial cells in the cochlea, the vestibular labyrinth and the endolymphatic sac. Slc26a4 Δ/Δ mice are devoid of pendrin and develop a severe enlargement of the membranous labyrinth, fail to acquire hearing and balance, and thereby provide a model for the human phenotype. Here, we generated a transgenic mouse line that expresses human SLC26A4 controlled by the promoter of ATP6V1B1. Crossing this transgene into the Slc26a4 Δ/Δ line restored protein expression of pendrin in the endolymphatic sac without inducing detectable expression in the cochlea or the vestibular sensory organs. The transgene prevented abnormal enlargement of the membranous labyrinth, restored a normal endocochlear potential, normal pH gradients between endolymph and perilymph in the cochlea, normal otoconia formation in the vestibular labyrinth and normal sensory functions of hearing and balance. Our study demonstrates that restoration of pendrin to the endolymphatic sac is sufficient to restore normal inner ear function. This finding in conjunction with our previous report that pendrin expression is required for embryonic development but not for the maintenance of hearing opens the prospect that a spatially and temporally limited therapy will restore normal hearing in human patients carrying a variety of mutations of SLC26A4., Author Summary Mutations of SLC26A4 are the most common cause for hearing loss associated with a swelling of the inner ear. This human disease is largely recapitulated in a mutant mouse model. Mutant mice lack Slc26a4 expression and their inner ears swell during embryonic development, which leads to failure of the cochlea and the vestibular organs resulting in deafness and loss of balance. SLC26A4 is normally found in the cochlea and vestibular organs of the inner ear as well as in the endolymphatic sac, which is a non-sensory part of the inner ear. The multitude of sites where SLC26A4 is located made the goal to restore function through restoration look futile, unless some sites were more important than others. Here, we generated a new mutant mouse that expresses SLC26A4 in the endolymphatic sac but not in the cochlea or the vestibular organs of the inner ear. Fantastically, this mouse did not develop the detrimental swelling of the inner ear and even more exciting, the mouse developed normal hearing and balance. Our study provides the proof-of-concept that a therapy aimed at repairing the endolymphatic sac during embryonic development is sufficient to restore a life-time of normal hearing and balance.

Published
2013

18. Correction for Gao et al., Deletion of hensin/DMBT1 blocks conversion of β- to α-intercalated cells and induces distal renal tubular acidosis

Author

Raoul D. Nelson, Cristina Miró-Julià, Ben Yi Tew, Qais Al-Awqatir, Mary McKee, Teodor G. Pǎunescu, Dennis Brown, Françoise Leviel, Faisal H. Cheema, Xiaobo Gao, Lance Miller, and Dominique Eladari

Subjects
Pathology, medicine.medical_specialty, Multidisciplinary, Distal renal tubular acidosis, business.industry, medicine, Physiology, Intercalated Cell, medicine.disease, business, Corrections
Published
2012

19. PTH-independent regulation of blood calcium concentration by the calcium-sensing receptor

Author

Pascal Houillier, Soline Bourgeois, Bharath Wootla, Dominique Eladari, Renaud de la Faille, Robert H. Dodd, Kamel Laghmani, Corinne Collet, Régine Chambrey, Patrick Bruneval, Hélène Faure, Martial Ruat, Erik Ilsø Christensen, Chantal Mandet, Lydie Cheval, Suresh Krishna Ramakrishnan, Alexandre Loupy, Paris-Centre de Recherche Cardiovasculaire (PARCC - UMR-S U970), Université Paris Descartes - Paris 5 (UPD5)-Institut National de la Santé et de la Recherche Médicale (INSERM)-Hôpital Européen Georges Pompidou [APHP] (HEGP), Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP)-Hôpitaux Universitaires Paris Ouest - Hôpitaux Universitaires Île de France Ouest (HUPO)-Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP)-Hôpitaux Universitaires Paris Ouest - Hôpitaux Universitaires Île de France Ouest (HUPO), Centre de Recherche des Cordeliers (CRC (UMR_S 872)), Université Paris Descartes - Paris 5 (UPD5)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS), Department of Neurology, Mayo Clinic Comprehensive Cancer Center, Mayo Clinic, Service de Néphrologie-Transplantation-Dialyse, CHU Bordeaux [Bordeaux]-Groupe hospitalier Pellegrin, Laboratoire de neurobiologie cellulaire et moléculaire (NBCM), Centre National de la Recherche Scientifique (CNRS), CNRS ERL 8228 - Laboratoire de physiologie rénale et tubulopathies, 75006, Paris, France. (TIR), Institut de Chimie des Substances Naturelles (ICSN), Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC), Hôpital Européen Georges Pompidou [APHP] (HEGP), Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP)-Hôpitaux Universitaires Paris Ouest - Hôpitaux Universitaires Île de France Ouest (HUPO)-Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP)-Hôpitaux Universitaires Paris Ouest - Hôpitaux Universitaires Île de France Ouest (HUPO)-Université Paris Descartes - Paris 5 (UPD5)-Institut National de la Santé et de la Recherche Médicale (INSERM), Université Pierre et Marie Curie - Paris 6 (UPMC)-Université Paris Descartes - Paris 5 (UPD5)-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS), Métabolisme et physiologie rénales (ERL 8228), Centre National de la Recherche Scientifique (CNRS)-Centre de Recherche des Cordeliers (CRC (UMR_S_1138 / U1138)), École Pratique des Hautes Études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Université Paris Descartes - Paris 5 (UPD5)-Institut National de la Santé et de la Recherche Médicale (INSERM)-Sorbonne Université (SU)-École Pratique des Hautes Études (EPHE), and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Université Paris Descartes - Paris 5 (UPD5)-Institut National de la Santé et de la Recherche Médicale (INSERM)-Sorbonne Université (SU)

Subjects
Male, MESH: Amino Acids, [SDV]Life Sciences [q-bio], 030232 urology & nephrology, Pamidronate, Parathyroid hormone, MESH: Rats, Sprague-Dawley, MESH: Pamidronate, Rats, Sprague-Dawley, 0302 clinical medicine, MESH: Animals, Amino Acids, Solute Carrier Family 12, Member 1, MESH: Sodium-Potassium-Exchanging ATPase, 0303 health sciences, Kidney, Bone Density Conservation Agents, Diphosphonates, [CHIM.ORGA]Chemical Sciences/Organic chemistry, Chemistry, Reabsorption, MESH: Naphthalenes, General Medicine, Parathyroid chief cell, MESH: Parathyroid Hormone, MESH: Parathyroidectomy, medicine.anatomical_structure, Parathyroid Hormone, Creatinine, MESH: Permeability, MESH: Calcium, MESH: Solute Carrier Family 12, Member 1, Sodium-Potassium-Exchanging ATPase, Calcium-sensing receptor, MESH: Receptors, Calcium-Sensing, medicine.medical_specialty, MESH: Rats, Hypoparathyroidism, Sodium-Potassium-Chloride Symporters, MESH: Diphosphonates, Osteocalcin, chemistry.chemical_element, MESH: Creatinine, Naphthalenes, Calcium, Permeability, MESH: Osteocalcin, MESH: Bone Density Conservation Agents, 03 medical and health sciences, Internal medicine, medicine, Animals, 030304 developmental biology, Parathyroidectomy, Calcium metabolism, MESH: Hypoparathyroidism, MESH: Sodium-Potassium-Chloride Symporters, urogenital system, medicine.disease, MESH: Male, Rats, Endocrinology, Loop of Henle, Receptors, Calcium-Sensing, MESH: Loop of Henle
Abstract

International audience; Tight regulation of calcium levels is required for many critical biological functions. The Ca2+-sensing receptor (CaSR) expressed by parathyroid cells controls blood calcium concentration by regulating parathyroid hormone (PTH) secretion. However, CaSR is also expressed in other organs, such as the kidney, but the importance of extraparathyroid CaSR in calcium metabolism remains unknown. Here, we investigated the role of extraparathyroid CaSR using thyroparathyroidectomized, PTH-supplemented rats. Chronic inhibition of CaSR selectively increased renal tubular calcium absorption and blood calcium concentration independent of PTH secretion change and without altering intestinal calcium absorption. CaSR inhibition increased blood calcium concentration in animals pretreated with a bisphosphonate, indicating that the increase did not result from release of bone calcium. Kidney CaSR was expressed primarily in the thick ascending limb of the loop of Henle (TAL). As measured by in vitro microperfusion of cortical TAL, CaSR inhibitors increased calcium reabsorption and paracellular pathway permeability but did not change NaCl reabsorption. We conclude that CaSR is a direct determinant of blood calcium concentration, independent of PTH, and modulates renal tubular calcium transport in the TAL via the permeability of the paracellular pathway. These findings suggest that CaSR inhibitors may provide a new specific treatment for disorders related to impaired PTH secretion, such as primary hypoparathyroidism.

Published
2012

20. Determination of the best method to estimate glomerular filtration rate from serum creatinine in adult patients with sickle cell disease: a prospective observational cohort study

Author

Marie Courbebaisse, Dominique Eladari, Jean-Antoine Ribeil, Jean-Benoît Arlet, Dominique Prié, Gérard Friedlander, Jacques Pouchot, Gilles Chatellier, Marianne de Montalembert, Sophie de Seigneux, Jean-Claude Souberbielle, Service de Médecine Interne [CHU HEGP], Centre de référence des syndromes drépanocytaires majeurs-Hôpital Européen Georges Pompidou [APHP] (HEGP), Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP)-Hôpitaux Universitaires Paris Ouest - Hôpitaux Universitaires Île de France Ouest (HUPO)-Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP)-Hôpitaux Universitaires Paris Ouest - Hôpitaux Universitaires Île de France Ouest (HUPO), Service de Biothérapie, Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP)-Centre de référence des syndromes drépanocytaires majeurs-CHU Necker - Enfants Malades [AP-HP], Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP), Centre d'Investigation Clinique, Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP)-Hôpital Européen Georges Pompidou [APHP] (HEGP), Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP)-Hôpitaux Universitaires Paris Ouest - Hôpitaux Universitaires Île de France Ouest (HUPO)-Hôpitaux Universitaires Paris Ouest - Hôpitaux Universitaires Île de France Ouest (HUPO)-Institut National de la Santé et de la Recherche Médicale (INSERM), Centre de Recherche des Cordeliers (CRC (UMR_S 872)), Université Paris Descartes - Paris 5 (UPD5)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS), Service de Néphrologie, Hôpital Cantonal de Genève, Centre de recherche Croissance et signalisation (UMR_S 845), Centre National de la Recherche Scientifique (CNRS)-Institut National de la Santé et de la Recherche Médicale (INSERM)-Université Paris Descartes - Paris 5 (UPD5), Service de Pédiatrie Générale, Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP)-CHU Necker - Enfants Malades [AP-HP], Néphrologie, Hôpital Européen Georges Pompidou [APHP] (HEGP), BMC, Ed., Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP)-Hôpitaux Universitaires Paris Ouest - Hôpitaux Universitaires Île de France Ouest (HUPO)-Hôpitaux Universitaires Paris Ouest - Hôpitaux Universitaires Île de France Ouest (HUPO)-Centre de référence des syndromes drépanocytaires majeurs, Université Pierre et Marie Curie - Paris 6 (UPMC)-Université Paris Descartes - Paris 5 (UPD5)-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS), Université Paris Descartes - Paris 5 (UPD5)-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS), Assistance publique - Hôpitaux de Paris (AP-HP)-Hôpital Européen Georges Pompidou [APHP] ( HEGP ) -Centre de référence des syndromes drépanocytaires majeurs, Assistance publique - Hôpitaux de Paris (AP-HP)-Centre de référence des syndromes drépanocytaires majeurs-CHU Necker - Enfants Malades [AP-HP], Assistance publique - Hôpitaux de Paris (AP-HP)-Hôpital Européen Georges Pompidou [APHP] ( HEGP ) -Institut National de la Santé et de la Recherche Médicale ( INSERM ), Centre de Recherche des Cordeliers ( CRC (UMR_S 872) ), Université Pierre et Marie Curie - Paris 6 ( UPMC ) -Université Paris Descartes - Paris 5 ( UPD5 ) -Institut National de la Santé et de la Recherche Médicale ( INSERM ) -Centre National de la Recherche Scientifique ( CNRS ), Centre de recherche Croissance et signalisation ( UMR_S 845 ), Université Paris Descartes - Paris 5 ( UPD5 ) -Institut National de la Santé et de la Recherche Médicale ( INSERM ) -Centre National de la Recherche Scientifique ( CNRS ), Assistance publique - Hôpitaux de Paris (AP-HP)-CHU Necker - Enfants Malades [AP-HP], and Hôpital Européen Georges Pompidou [APHP] ( HEGP )

Subjects
[ SDV.MHEP.UN ] Life Sciences [q-bio]/Human health and pathology/Urology and Nephrology, Male, 030232 urology & nephrology, 030204 cardiovascular system & hematology, urologic and male genital diseases, lcsh:RC870-923, [SDV.MHEP.UN]Life Sciences [q-bio]/Human health and pathology/Urology and Nephrology, Cohort Studies, chemistry.chemical_compound, 0302 clinical medicine, Ethnicity, Diagnosis, Computer-Assisted, Iohexol plasma clearance, reproductive and urinary physiology, 2. Zero hunger, Middle Aged, female genital diseases and pregnancy complications, Glomerular hyperfiltration, Nephrology, Creatinine, Median body, Female, Kidney Diseases, medicine.symptom, Glomerular filtration rate, Algorithms, medicine.drug, Research Article, Adult, medicine.medical_specialty, Adolescent, Urology, Renal function, CKD-EPI equation, Anemia, Sickle Cell, Sensitivity and Specificity, Nephropathy, 03 medical and health sciences, Young Adult, Internal medicine, medicine, Humans, Albuminuria, Aged, business.industry, Sickle cell disease, Reproducibility of Results, medicine.disease, lcsh:Diseases of the genitourinary system. Urology, [SDV.MHEP.UN] Life Sciences [q-bio]/Human health and pathology/Urology and Nephrology, Endocrinology, chemistry, Microalbuminuria, Iohexol, business, Biomarkers
Abstract

Background Sickle cell disease (SCD) leads to tissue hypoxia resulting in chronic organ dysfunction including SCD associated nephropathy. The goal of our study was to determine the best equation to estimate glomerular filtration rate (GFR) in SCD adult patients. Methods We conducted a prospective observational cohort study. Since 2007, all adult SCD patients in steady state, followed in two medical departments, have had their GFR measured using iohexol plasma clearance (gold standard). The Cockcroft-Gault, MDRD-v4, CKP-EPI and finally, MDRD and CKD-EPI equations without adjustment for ethnicity were tested to estimate GFR from serum creatinine. Estimated GFRs were compared to measured GFRs according to the graphical Bland and Altman method. Results Sixty-four SCD patients (16 men, median age 27.5 years [range 18.0-67.5], 41 with SS-genotype were studied. They were Sub-Saharan Africa and French West Indies natives and predominantly lean (median body mass index: 22 kg/m2 [16-33]). Hyperfiltration (defined as measured GFR >110 mL/min/1.73 m2) was detected in 53.1% of patients. Urinary albumin/creatinine ratio was higher in patients with hyperfiltration than in patients with normal GFR (4.05 mg/mmol [0.14-60] versus 0.4 mg/mmol [0.7-81], p = 0.01). The CKD-EPI equation without adjustment for ethnicity had both the lowest bias and the greatest precision. Differences between estimated GFRs using the CKP-EPI equation and measured GFRs decreased with increasing GFR values, whereas it increased with the Cockcroft-Gault and MDRD-v4 equations. Conclusions We confirm that SCD patients have a high rate of glomerular hyperfiltration, which is frequently associated with microalbuminuria or macroalbuminuria. In non-Afro-American SCD patients, the best method for estimating GFR from serum creatinine is the CKD-EPI equation without adjustment for ethnicity. This equation is particularly accurate to estimate high GFR values, including glomerular hyperfiltration, and thus should be recommended to screen SCD adult patients at high risk for SCD nephropathy.

Published
2012

21. Renal phenotype in mice lacking the Kir5.1 (Kcnj16) K+ channel subunit contrasts with that observed in SeSAME/EAST syndrome

Author

May Bloch-Faure, Marc Paulais, Stéphane Lourdel, Mathilde Keck, Suresh Krishna Ramakrishnan, Pascal Houillier, Jacques Teulon, Dominique Eladari, Thibaut Jacques, Nicolas Picard, Fabien Sohet, Stephen J. Tucker, Centre de Recherche des Cordeliers (CRC (UMR_S 872)), Université Pierre et Marie Curie - Paris 6 (UPMC)-Université Paris Descartes - Paris 5 (UPD5)-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS), Hôpital Européen Georges Pompidou [APHP] (HEGP), Assistance publique - Hôpitaux de Paris (AP-HP) (APHP)-Hôpitaux Universitaires Paris Ouest - Hôpitaux Universitaires Île de France Ouest (HUPO), Clarendon Laboratory, Department of Physics, University of Oxford [Oxford], Laboratoire de physiologie, physiopathologie et génomique rénales, Centre National de la Recherche Scientifique (CNRS)-Centre de Recherche des Cordeliers (CRC (UMR_S_1138 / U1138)), École pratique des hautes études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut National de la Santé et de la Recherche Médicale (INSERM)-Sorbonne Université (SU)-Université Paris Cité (UPCité)-École pratique des hautes études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut National de la Santé et de la Recherche Médicale (INSERM)-Sorbonne Université (SU)-Université Paris Cité (UPCité), Université Paris Descartes - Faculté de Médecine (UPD5 Médecine), Université Paris Descartes - Paris 5 (UPD5), Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP)-Hôpitaux Universitaires Paris Ouest - Hôpitaux Universitaires Île de France Ouest (HUPO), Clarendon Laboratory [Oxford], University of Oxford, This work was supported by Agence Nationale de la Recherche (ANR) Grant Physio 2007-RPVO7084. M.K. holds a PhD fellowship from the French Ministère de la Recherche. S.K.R. holds a PhD fellowship from the Erasmus Mundus External Cooperation Window Lot 15 India European scholarship program. M.P. is an Institut National de la Santé et de la Recherche Médicale researcher. S.J.T. was supported by the Royal Society., Paulais, Marc, Laboratoire de physiologie génomique et de physiopathologie rénale (CNRS ERL 7226), Centre National de la Recherche Scientifique (CNRS)-Centre de Recherche des Cordeliers, École Pratique des Hautes Études (EPHE), and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut National de la Santé et de la Recherche Médicale (INSERM)-Sorbonne Université (SU)-Université Paris Cité (UPCité)-École Pratique des Hautes Études (EPHE)

Subjects
medicine.medical_specialty, Patch-Clamp Techniques, Intracellular pH, [SDV]Life Sciences [q-bio], 030232 urology & nephrology, Hypokalemia, KCNJ10, [SDV.BBM.BM] Life Sciences [q-bio]/Biochemistry, Molecular Biology/Molecular biology, [SDV.MHEP.UN]Life Sciences [q-bio]/Human health and pathology/Urology and Nephrology, Amiloride, Mice, 03 medical and health sciences, 0302 clinical medicine, Sodium Potassium Chloride Symporter Inhibitors, Tubulopathy, Furosemide, Internal medicine, EAST syndrome, medicine, Animals, Humans, Hypercalciuria, Distal convoluted tubule, Potassium Channels, Inwardly Rectifying, Diuretics, Ion transporter, ComputingMilieux_MISCELLANEOUS, 030304 developmental biology, Mice, Knockout, 0303 health sciences, Multidisciplinary, biology, Chemistry, [SDV.BBM.BM]Life Sciences [q-bio]/Biochemistry, Molecular Biology/Molecular biology, Syndrome, Biological Sciences, medicine.disease, [SDV.MHEP.UN] Life Sciences [q-bio]/Human health and pathology/Urology and Nephrology, Hydrochlorothiazide, Kidney Tubules, Phenotype, Endocrinology, medicine.anatomical_structure, biology.protein, medicine.symptom, Acidosis, Sodium Channel Blockers
Abstract

The heteromeric inwardly rectifying Kir4.1/Kir5.1 K + channel underlies the basolateral K + conductance in the distal nephron and is extremely sensitive to inhibition by intracellular pH. The functional importance of Kir4.1/Kir5.1 in renal ion transport has recently been highlighted by mutations in the human Kir4.1 gene ( KCNJ10 ) that result in seizures, sensorineural deafness, ataxia, mental retardation, and electrolyte imbalance (SeSAME)/epilepsy, ataxia, sensorineural deafness, and renal tubulopathy (EAST) syndrome, a complex disorder that includes salt wasting and hypokalemic alkalosis. Here, we investigated the role of the Kir5.1 subunit in mice with a targeted disruption of the Kir5.1 gene ( Kcnj16 ). The Kir5.1 −/− mice displayed hypokalemic, hyperchloremic metabolic acidosis with hypercalciuria. The short-term responses to hydrochlorothiazide, an inhibitor of ion transport in the distal convoluted tubule (DCT), were also exaggerated, indicating excessive renal Na + absorption in this segment. Furthermore, chronic treatment with hydrochlorothiazide normalized urinary excretion of Na + and Ca 2+ , and abolished acidosis in Kir5.1 −/− mice. Finally, in contrast to WT mice, electrophysiological recording of K + channels in the DCT basolateral membrane of Kir5.1 −/− mice revealed that, even though Kir5.1 is absent, there is an increased K + conductance caused by the decreased pH sensitivity of the remaining homomeric Kir4.1 channels. In conclusion, disruption of Kcnj16 induces a severe renal phenotype that, apart from hypokalemia, is the opposite of the phenotype seen in SeSAME/EAST syndrome. These results highlight the important role that Kir5.1 plays as a pH-sensitive regulator of salt transport in the DCT, and the implication of these results for the correct genetic diagnosis of renal tubulopathies is discussed.

Published
2011

22. Deletion of hensin/DMBT1 blocks conversion of β- to α-intercalated cells and induces distal renal tubular acidosis

Author

Raoul D. Nelson, Cristina Miró-Julià, Dominique Eladari, Dennis Brown, Françoise Leviel, Ben Yi Tew, Qais Al-Awqati, Teodor G. Păunescu, Faisal H. Cheema, Xiaobo Gao, Mary McKee, and Lance Edward Miller

Subjects
Cell type, ATPase, Cell, Anion Transport Proteins, Mice, Transgenic, Biology, Extracellular matrix, Mice, Distal renal tubular acidosis, medicine, Animals, Secretion, Intercalated Cell, Kidney Tubules, Collecting, Multidisciplinary, Integrin beta1, Tumor Suppressor Proteins, Calcium-Binding Proteins, Mucins, Pendrin, Acidosis, Renal Tubular, Biological Sciences, Hydrogen-Ion Concentration, medicine.disease, Cell biology, DNA-Binding Proteins, Mice, Inbred C57BL, Bicarbonates, medicine.anatomical_structure, Biochemistry, Sulfate Transporters, biology.protein, Gene Deletion
Abstract

Acid–base transport in the renal collecting tubule is mediated by two canonical cell types: the β-intercalated cell secretes HCO 3 by an apical Cl:HCO 3 named pendrin and a basolateral vacuolar (V)-ATPase. Acid secretion is mediated by the α-intercalated cell, which has an apical V-ATPase and a basolateral Cl:HCO 3 exchanger (kAE1). We previously suggested that the β-cell converts to the α-cell in response to acid feeding, a process that depended on the secretion and deposition of an extracellular matrix protein termed hensin (DMBT1). Here, we show that deletion of hensin from intercalated cells results in the absence of typical α-intercalated cells and the consequent development of complete distal renal tubular acidosis (dRTA). Essentially all of the intercalated cells in the cortex of the mutant mice are canonical β-type cells, with apical pendrin and basolateral or diffuse/bipolar V-ATPase. In the medulla, however, a previously undescribed cell type has been uncovered, which resembles the cortical β-intercalated cell in ultrastructure, but does not express pendrin. Polymerization and deposition of hensin (in response to acidosis) requires the activation of β1 integrin, and deletion of this gene from the intercalated cell caused a phenotype that was identical to the deletion of hensin itself, supporting its critical role in hensin function. Because previous studies suggested that the conversion of β- to α-intercalated cells is a manifestation of terminal differentiation, the present results demonstrate that this differentiation proceeds from HCO 3 secreting to acid secreting phenotypes, a process that requires deposition of hensin in the ECM.

Published
2010

23. Tissue kallikrein permits early renal adaptation to potassium load

Author

Nicolas Picard, Fabien Sohet, Pascal Houillier, Lydi E. Cheval, Françoise Leviel, Sebastian Frische, Bharath Wootla, Pierre Meneton, May Bloch-Faure, Régine Chambrey, Soumaya El Moghrabi, Dominique Eladari, Physiopathologie, diagnostic et traitements des maladies osseuses / Pathophysiology, Diagnosis & Treatments of Bone Diseases (LYOS), Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut National de la Santé et de la Recherche Médicale (INSERM), Service de Physiologie [Georges-Pompidou], Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP)-Hôpital Européen Georges Pompidou [APHP] (HEGP), Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP)-Hôpitaux Universitaires Paris Ouest - Hôpitaux Universitaires Île de France Ouest (HUPO)-Hôpitaux Universitaires Paris Ouest - Hôpitaux Universitaires Île de France Ouest (HUPO)-Université Paris Descartes - Paris 5 (UPD5), OSA (XLIM-OSA), XLIM (XLIM), Université de Limoges (UNILIM)-Centre National de la Recherche Scientifique (CNRS)-Université de Limoges (UNILIM)-Centre National de la Recherche Scientifique (CNRS), University of California [San Diego] (UC San Diego), University of California (UC), Department of Neurology, Mayo Clinic Comprehensive Cancer Center, Mayo Clinic, Physiologie et pharmacologie vasculaire et rénale, IFR58-Université Paris Descartes - Paris 5 (UPD5)-Institut National de la Santé et de la Recherche Médicale (INSERM), Centre de Recherche des Cordeliers (CRC), Université Pierre et Marie Curie - Paris 6 (UPMC)-École Pratique des Hautes Études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Université Paris Descartes - Paris 5 (UPD5)-Institut National de la Santé et de la Recherche Médicale (INSERM), Laboratoire d'Informatique Médicale et Ingénierie des Connaissances en e-Santé (LIMICS), Université Paris 13 (UP13)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut National de la Santé et de la Recherche Médicale (INSERM), University of California, Université Paris Diderot - Paris 7 (UPD7)-École pratique des hautes études (EPHE), and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Université Paris Descartes - Paris 5 (UPD5)-Institut National de la Santé et de la Recherche Médicale (INSERM)

Subjects
Aldosterone synthase, MESH: Hydrogen-Ion Concentration, [SDV]Life Sciences [q-bio], Tissue kallikrein, 030232 urology & nephrology, Kidney, MESH: Mice, Knockout, chemistry.chemical_compound, H(+)-K(+)-Exchanging ATPase, Mice, 0302 clinical medicine, MESH: Potassium, Dietary, MESH: Cytochrome P-450 CYP11B2, MESH: Reverse Transcriptase Polymerase Chain Reaction, MESH: Sodium, MESH: H(+)-K(+)-Exchanging ATPase, MESH: Animals, Aldosterone, Mice, Knockout, 0303 health sciences, Multidisciplinary, Reverse Transcriptase Polymerase Chain Reaction, Biological Sciences, Hydrogen-Ion Concentration, Adaptation, Physiological, medicine.anatomical_structure, Tissue Kallikreins, medicine.medical_specialty, Sodium, MESH: Biological Transport, MESH: Tissue Kallikreins, chemistry.chemical_element, Biology, In Vitro Techniques, Aldosterone Synthase, Excretion, 03 medical and health sciences, TheoryofComputation_ANALYSISOFALGORITHMSANDPROBLEMCOMPLEXITY, Internal medicine, medicine, Animals, Cytochrome P-450 CYP11B2, Intercalated Cell, Kidney Tubules, Collecting, MESH: Mice, MESH: Kidney Tubules, Collecting, 030304 developmental biology, MESH: In Vitro Techniques, Potassium, Dietary, MESH: Aldosterone, Biological Transport, MESH: Kidney, MESH: Adaptation, Physiological, Endocrinology, chemistry, MESH: Potassium, biology.protein, Potassium
Abstract

Tissue kallikrein (TK) is a serine protease synthetized in renal tubular cells located upstream from the collecting duct where renal potassium balance is regulated. Because secretion of TK is promoted by K + intake, we hypothesized that this enzyme might regulate plasma K + concentration ([K + ]). We showed in wild-type mice that renal K + and TK excretion increase in parallel after a single meal, representing an acute K + load, whereas aldosterone secretion is not modified. Using aldosterone synthase-deficient mice, we confirmed that the control of TK secretion is aldosterone-independent. Mice with TK gene disruption ( TK −/− ) were used to assess the impact of the enzyme on plasma [K + ]. A single large feeding did not lead to any significant change in plasma [K + ] in TK +/+ , whereas TK −/− mice became hyperkalemic. We next examined the impact of TK disruption on K + transport in isolated cortical collecting ducts (CCDs) microperfused in vitro. We found that CCDs isolated from TK −/− mice exhibit net transepithelial K + absorption because of abnormal activation of the colonic H + ,K + -ATPase in the intercalated cells. Finally, in CCDs isolated from TK −/− mice and microperfused in vitro, the addition of TK to the perfusate but not to the peritubular bath caused a 70% inhibition of H + ,K + -ATPase activity. In conclusion, we have identified the serine protease TK as a unique kalliuretic factor that protects against hyperkalemia after a dietary K + load.

Published
2010

24. The Na+-dependent chloride-bicarbonate exchanger SLC4A8 mediates an electroneutral Na+ reabsorption process in the renal cortical collecting ducts of mice

Author

Françoise, Leviel, Christian A, Hübner, Pascal, Houillier, Luciana, Morla, Soumaya, El Moghrabi, Gaëlle, Brideau, Hatim, Hassan, Hassan, Hatim, Mark D, Parker, Ingo, Kurth, Alexandra, Kougioumtzes, Anne, Sinning, Vladimir, Pech, Kent A, Riemondy, R Lance, Miller, Edith, Hummler, Gary E, Shull, Peter S, Aronson, Alain, Doucet, Susan M, Wall, Régine, Chambrey, Dominique, Eladari, Friedrich-Schiller-Universität = Friedrich Schiller University Jena [Jena, Germany], Service de Physiologie [Georges-Pompidou], Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP)-Hôpital Européen Georges Pompidou [APHP] (HEGP), Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP)-Hôpitaux Universitaires Paris Ouest - Hôpitaux Universitaires Île de France Ouest (HUPO)-Hôpitaux Universitaires Paris Ouest - Hôpitaux Universitaires Île de France Ouest (HUPO)-Université Paris Descartes - Paris 5 (UPD5), Centre de Recherche des Cordeliers (CRC), Université Pierre et Marie Curie - Paris 6 (UPMC)-École Pratique des Hautes Études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Université Paris Descartes - Paris 5 (UPD5)-Institut National de la Santé et de la Recherche Médicale (INSERM), Physiopathologie, diagnostic et traitements des maladies osseuses / Pathophysiology, Diagnosis & Treatments of Bone Diseases (LYOS), Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut National de la Santé et de la Recherche Médicale (INSERM), Centre de Recherche des Cordeliers (CRC (UMR_S_1138 / U1138)), École Pratique des Hautes Études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Université Paris Descartes - Paris 5 (UPD5)-Institut National de la Santé et de la Recherche Médicale (INSERM)-Sorbonne Université (SU), Rheinisch-Westfälische Technische Hochschule Aachen University (RWTH), Université de Lausanne = University of Lausanne (UNIL), Laboratoire de physiologie, physiopathologie et génomique rénales, Centre National de la Recherche Scientifique (CNRS)-Centre de Recherche des Cordeliers (CRC (UMR_S_1138 / U1138)), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut National de la Santé et de la Recherche Médicale (INSERM)-Sorbonne Université (SU)-Université Paris Cité (UPCité)-École Pratique des Hautes Études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut National de la Santé et de la Recherche Médicale (INSERM)-Sorbonne Université (SU)-Université Paris Cité (UPCité), Centre de Recherche des Cordeliers (CRC (UMR_S 872)), Université Pierre et Marie Curie - Paris 6 (UPMC)-Université Paris Descartes - Paris 5 (UPD5)-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS), Paris-Centre de Recherche Cardiovasculaire (PARCC - UMR-S U970), Hôpital Européen Georges Pompidou [APHP] (HEGP), Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP)-Hôpitaux Universitaires Paris Ouest - Hôpitaux Universitaires Île de France Ouest (HUPO)-Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP)-Hôpitaux Universitaires Paris Ouest - Hôpitaux Universitaires Île de France Ouest (HUPO)-Université Paris Descartes - Paris 5 (UPD5)-Institut National de la Santé et de la Recherche Médicale (INSERM), Université Paris Descartes - Faculté de Médecine (UPD5 Médecine), Université Paris Descartes - Paris 5 (UPD5), and Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP)-Hôpitaux Universitaires Paris Ouest - Hôpitaux Universitaires Île de France Ouest (HUPO)

Subjects
Epithelial sodium channel, Sodium Chloride Symporter Inhibitors, Xenopus, [SDV]Life Sciences [q-bio], 030232 urology & nephrology, Kidney, Chloride, Amiloride, chemistry.chemical_compound, Mice, 0302 clinical medicine, Clinical investigation, Chloride-Bicarbonate Antiporters, Mice, Knockout, 0303 health sciences, biology, Reabsorption, General Medicine, Electrophysiology, medicine.anatomical_structure, Hydrochlorothiazide, 030220 oncology & carcinogenesis, Corrigendum, medicine.drug, Research Article, medicine.medical_specialty, Bicarbonate, Sodium, chemistry.chemical_element, Mice, Transgenic, Models, Biological, 03 medical and health sciences, Internal medicine, medicine, Animals, Distal convoluted tubule, Na dependent, Kidney Tubules, Collecting, Process (anatomy), 030304 developmental biology, urogenital system, Sodium-Bicarbonate Symporters, Pendrin, Mice, Inbred C57BL, Endocrinology, chemistry, Renal sodium excretion, biology.protein, Oocytes, Amiloride/pharmacology, Chloride-Bicarbonate Antiporters/metabolism, Electrophysiology/methods, Hydrochlorothiazide/pharmacology, Kidney/metabolism, Kidney Tubules, Collecting/metabolism, Oocytes/metabolism, Sodium/chemistry, Sodium Chloride Symporter Inhibitors/pharmacology, Sodium-Bicarbonate Symporters/metabolism, Cotransporter
Abstract

Regulation of sodium balance is a critical factor in the maintenance of euvolemia, and dysregulation of renal sodium excretion results in disorders of altered intravascular volume, such as hypertension. The amiloride-sensitive epithelial sodium channel (ENaC) is thought to be the only mechanism for sodium transport in the cortical collecting duct (CCD) of the kidney. However, it has been found that much of the sodium absorption in the CCD is actually amiloride insensitive and sensitive to thiazide diuretics, which also block the Na-Cl cotransporter (NCC) located in the distal convoluted tubule. In this study, we have demonstrated the presence of electroneutral, amiloride-resistant, thiazide-sensitive, transepithelial NaCl absorption in mouse CCDs, which persists even with genetic disruption of ENaC. Furthermore, hydrochlorothiazide (HCTZ) increased excretion of Na+ and Cl- in mice devoid of the thiazide target NCC, suggesting that an additional mechanism might account for this effect. Studies on isolated CCDs suggested that the parallel action of the Na+-driven Cl-/HCO3- exchanger (NDCBE/SLC4A8) and the Na+-independent Cl-/HCO3- exchanger (pendrin/SLC26A4) accounted for the electroneutral thiazide-sensitive sodium transport. Furthermore, genetic ablation of SLC4A8 abolished thiazide-sensitive NaCl transport in the CCD. These studies establish what we believe to be a novel role for NDCBE in mediating substantial Na+ reabsorption in the CCD and suggest a role for this transporter in the regulation of fluid homeostasis in mice.

Published
2010

25. Pendrin as a regulator of ECF and blood pressure

Author

Sebastian Frische, Marion Vallet, Dominique Eladari, Régine Chambrey, and Aurélie Edwards

Subjects
medicine.medical_specialty, Sodium, chemistry.chemical_element, Blood Pressure, Nephron, Sodium Chloride, Kidney, Chloride, Chlorides, Internal medicine, Extracellular fluid, Internal Medicine, medicine, Animals, Humans, Chloride-Bicarbonate Antiporters, Kidney Tubules, Distal, Ion Transport, biology, Chemistry, Reabsorption, Membrane Transport Proteins, Extracellular Fluid, Pendrin, Nephrons, medicine.anatomical_structure, Endocrinology, Sulfate Transporters, Nephrology, Paracellular transport, biology.protein, medicine.drug
Abstract

Udgivelsesdato: 2009-Jul PURPOSE OF REVIEW: Abnormal renal sodium handling plays a pivotal role in the pathophysiology of arterial hypertension. Though sodium is present in the diet as a chloride salt, most studies have focused on the renal mechanisms of sodium transport and their regulation, and very few have investigated the impact of chloride. However, strong evidence indicates that chloride may play a very important role in the 'prohypertensive' effects of sodium. RECENT FINDINGS: Several observations indicate that sodium has to be administered as NaCl and not as NaHCO3 to raise arterial blood pressure. Recently, genetic studies have pointed out the critical role of the most distal parts of the nephron in regulating sodium balance and blood pressure. Interestingly, in those segments, the transport of Na+ and Cl- proceeds separately, through different molecules. Recent evidence has demonstrated that an apical Cl-/HCO3- exchanger called pendrin is an absolute requirement for chloride reabsorption in the collecting system, indicating that chloride absorption is not passive and paracellular but is mediated by the intercalated cells. Importantly, pendrin disruption protects mice against mineralocorticoid-induced hypertension and impairs renal adaptation to a low NaCl diet. Moreover, recent findings suggest several mechanisms by which chloride transport might affect NaCl balance and blood pressure. SUMMARY: Pendrin-mediated chloride transport through intercalated cells appears to be an independent and important determinant of renal NaCl handling and therefore might represent a new target for blood pressure control.

Published
2009

26. A mutant alphaII-spectrin designed to resist calpain and caspase cleavage questions the functional importance of this process in vivo

Author

Sylvain Metral, Chrystophe Ferreira, Yves Colin, Gaeöl Nicolas, Marie-Christine Lecomte, Fleur Meary, Dominique Eladari, NICOLAS, Gaël, Protéines de la membrane érythrocytaire et homologues non-érythroides, Université des Antilles et de la Guyane (UAG)-Institut National de la Transfusion Sanguine [Paris] (INTS)-Université Paris Diderot - Paris 7 (UPD7)-Université de La Réunion (UR)-Institut National de la Santé et de la Recherche Médicale (INSERM), Institut Claude Bernard - Physiologie et Pathologie ((IFR_2)), Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP)-Université Paris Diderot - Paris 7 (UPD7)-Institut National de la Santé et de la Recherche Médicale (INSERM), Physiologie et pharmacologie vasculaire et rénale, IFR58-Université Paris Descartes - Paris 5 (UPD5)-Institut National de la Santé et de la Recherche Médicale (INSERM), Université des Antilles et de la Guyane ( UAG ) -Institut National de la Transfusion Sanguine [Paris] ( INTS ) -Université Paris Diderot - Paris 7 ( UPD7 ) -Université de la Réunion ( UR ) -Institut National de la Santé et de la Recherche Médicale ( INSERM ), Institut Claude Bernard - Physiologie et Pathologie, Assistance publique - Hôpitaux de Paris (AP-HP)-Université Paris Diderot - Paris 7 ( UPD7 ) -Institut National de la Santé et de la Recherche Médicale ( INSERM ), and IFR58-Université Paris Descartes - Paris 5 ( UPD5 ) -Institut National de la Santé et de la Recherche Médicale ( INSERM )

Subjects
Male, calmodulin, Proteolysis, caspase, Mutant, Blotting, Western, Molecular Sequence Data, knockout, Apoptosis, macromolecular substances, [SDV.BC]Life Sciences [q-bio]/Cellular Biology, Cleavage (embryo), Biochemistry, Mice, medicine, [SDV.BBM] Life Sciences [q-bio]/Biochemistry, Molecular Biology, Animals, Spectrin, [SDV.BBM]Life Sciences [q-bio]/Biochemistry, Molecular Biology, Amino Acid Sequence, Molecular Biology, [ SDV.BBM ] Life Sciences [q-bio]/Biochemistry, Molecular Biology, [SDV.BC] Life Sciences [q-bio]/Cellular Biology, Caspase, Cells, Cultured, Mice, Knockout, medicine.diagnostic_test, biology, Base Sequence, [ SDV.BC ] Life Sciences [q-bio]/Cellular Biology, Gene Transfer Techniques, Gene targeting, Calpain, Cell Biology, Fibroblasts, Embryo, Mammalian, Mice, Inbred C57BL, Phenotype, spectrin, Caspases, fodrin, Mutation, biology.protein, Female, calpain, Biogenesis
Abstract

International audience; alpha- and beta-spectrins are components of molecular scaffolds located under the lipid bilayer and named membrane skeletons. Disruption of these scaffolds through mutations in spectrins demonstrated that they are involved in the membrane localization or the maintenance of proteins associated with them. The ubiquitous alphaII-spectrin chain bears in its central region a unique domain that is sensitive to several proteases such as calpains or caspases. The conservation of this region in vertebrates suggests that the proteolysis of alphaII-spectrin by these enzymes could be involved in important functions. To assess the role of alphaII-spectrin cleavage in vivo, we generated a murine model in which the exons encoding the region defining this cleavage sensitivity were disrupted by gene targeting. Surprisingly, homozygous mice expressing this mutant alphaII-spectrin appeared healthy, bred normally, and had no histological anomaly. Remarkably, the mutant alphaII-spectrin assembles correctly into the membrane skeleton, thus challenging the notion that this region is required for the stable biogenesis of the membrane skeleton in nonerythroid cells. Our finding also argues against a critical role of this particular alphaII-spectrin cleavage in either major cellular functions or in normal development.

Published
2007

27. RhBG and RhCG, the Putative Ammonia Transporters, Are Expressed in the Same Cells in the Distal Nephron

Author

Michel Paillard, Dominique Eladari, Yves Colin, Dominique Goossens, Claude Lopez, Régine Chambrey, Fabienne Quentin, Jean-Pierre Cartron, Lydie Cheval, Physiologie et pharmacologie vasculaire et rénale, IFR58-Université Paris Descartes - Paris 5 (UPD5)-Institut National de la Santé et de la Recherche Médicale (INSERM), Centre de Recherche des Cordeliers (CRC), Université Pierre et Marie Curie - Paris 6 (UPMC)-École Pratique des Hautes Études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Université Paris Descartes - Paris 5 (UPD5)-Institut National de la Santé et de la Recherche Médicale (INSERM), Banque de france, Banque de France, Institut National de la Transfusion Sanguine, Paris, France, Inserm UMR_S 665, Paris, France, Université Paris Diderot, Sorbonne Paris Cité, UMR-S665, Paris, France, Protéines de la membrane érythrocytaire et homologues non-érythroides, Université des Antilles et de la Guyane (UAG)-Institut National de la Transfusion Sanguine [Paris] (INTS)-Université Paris Diderot - Paris 7 (UPD7)-Université de La Réunion (UR)-Institut National de la Santé et de la Recherche Médicale (INSERM), Service de physiologie, explorations fonctionnelles et radioisotopes [CHU HEGP], Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP)-Hôpital Européen Georges Pompidou [APHP] (HEGP), Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP)-Hôpitaux Universitaires Paris Ouest - Hôpitaux Universitaires Île de France Ouest (HUPO)-Hôpitaux Universitaires Paris Ouest - Hôpitaux Universitaires Île de France Ouest (HUPO), Paris-Centre de Recherche Cardiovasculaire (PARCC - UMR-S U970), Hôpital Européen Georges Pompidou [APHP] (HEGP), Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP)-Hôpitaux Universitaires Paris Ouest - Hôpitaux Universitaires Île de France Ouest (HUPO)-Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP)-Hôpitaux Universitaires Paris Ouest - Hôpitaux Universitaires Île de France Ouest (HUPO)-Université Paris Descartes - Paris 5 (UPD5)-Institut National de la Santé et de la Recherche Médicale (INSERM), Université Paris Diderot - Paris 7 (UPD7)-École pratique des hautes études (EPHE), and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Université Paris Descartes - Paris 5 (UPD5)-Institut National de la Santé et de la Recherche Médicale (INSERM)

Subjects
Male, [SDV]Life Sciences [q-bio], MESH: Membrane Glycoproteins, Gene Expression, Nephron, MESH: Rats, Sprague-Dawley, 030204 cardiovascular system & hematology, MESH: Membrane Transport Proteins, Rats, Sprague-Dawley, Mice, 0302 clinical medicine, MESH: Reverse Transcriptase Polymerase Chain Reaction, MESH: Animals, MESH: Ammonia, Cation Transport Proteins, Epithelial polarity, 0303 health sciences, Membrane Glycoproteins, MESH: Immunoblotting, Reverse Transcriptase Polymerase Chain Reaction, General Medicine, Connecting tubule, Cell biology, medicine.anatomical_structure, Nephrology, MESH: Cell Fractionation, Ammonium transport, medicine.medical_specialty, MESH: Gene Expression, MESH: Rats, Renal cortex, Immunoblotting, MESH: Glycoproteins, MESH: Carrier Proteins, Biology, Cell Fractionation, Antibodies, 03 medical and health sciences, MESH: Cation Transport Proteins, Ammonia, Internal medicine, medicine, Animals, Intercalated Cell, RNA, Messenger, Kidney Tubules, Collecting, Ammonia transporter, MESH: Mice, MESH: Kidney Tubules, Collecting, MESH: Nephrons, Glycoproteins, 030304 developmental biology, MESH: RNA, Messenger, MESH: Antibodies, Membrane Transport Proteins, Nephrons, MESH: Male, Rats, Endocrinology, RHCG, biology.protein, Carrier Proteins
Abstract

International audience; Two nonerythroid homologs of the blood group Rh proteins, RhCG and RhBG, which share homologies with specific ammonia transporters in primitive organisms and plants, could represent members of a new family of proteins involved in ammonia transport in the mammalian kidney. Consistent with this hypothesis, the expression of RhCG was recently reported at the apical pole of all connecting tubule (CNT) cells as well as in intercalated cells of collecting duct (CD). To assess the localization along the nephron of RhBG, polyclonal antibodies against the Rh type B glycoprotein were generated. In immunoblot experiments, a specific polypeptide of Mr approximately 50 kD was detected in rat kidney cortex and in outer and inner medulla membrane fractions. Immunocytochemical studies revealed RhBG expression in distal nephron segments within the cortical labyrinth, medullary rays, and outer and inner medulla. RhBG expression was restricted to the basolateral membrane of epithelial cells. The same localization was observed in rat and mouse kidney. RT-PCR analysis on microdissected rat nephron segments confirmed that RhBG mRNAs were chiefly expressed in CNT and cortical and outer medullary CD. Double immunostaining with RhCG demonstrated that RhBG and RhCG were coexpressed in the same cells, but with a basolateral and apical localization, respectively. In conclusion, RhBG and RhCG are present in a major site of ammonia secretion in the kidney, i.e., the CNT and CD, in agreement with their putative role in ammonium transport.

Published
2003

28. Expression of RhCG, a New Putative NH3/NH4+ Transporter, along the Rat Nephron

Author

Jean-Pierre Cartron, Alain Doucet, Dominique Eladari, Fabienne Quentin, Lydie Cheval, I Mouro, Olivier F. Bertrand, Régine Chambrey, Michel Paillard, Baya Cherif-Zahar, Physiologie et pharmacologie vasculaire et rénale, IFR58-Université Paris Descartes - Paris 5 (UPD5)-Institut National de la Santé et de la Recherche Médicale (INSERM), Centre de Recherche des Cordeliers (CRC), Université Paris Diderot - Paris 7 (UPD7)-École pratique des hautes études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Université Paris Descartes - Paris 5 (UPD5)-Institut National de la Santé et de la Recherche Médicale (INSERM), Processus mentaux et activation cérébrale, Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-IFR19-Institut National de la Santé et de la Recherche Médicale (INSERM), Centre de recherche Croissance et signalisation (UMR_S 845), Université Paris Descartes - Paris 5 (UPD5)-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS), Protéines de la membrane érythrocytaire et homologues non-érythroides, Université des Antilles et de la Guyane (UAG)-Institut National de la Transfusion Sanguine [Paris] (INTS)-Université Paris Diderot - Paris 7 (UPD7)-Université de La Réunion (UR)-Institut National de la Santé et de la Recherche Médicale (INSERM), Service de physiologie, explorations fonctionnelles et radioisotopes [CHU HEGP], Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP)-Hôpital Européen Georges Pompidou [APHP] (HEGP), Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP)-Hôpitaux Universitaires Paris Ouest - Hôpitaux Universitaires Île de France Ouest (HUPO)-Hôpitaux Universitaires Paris Ouest - Hôpitaux Universitaires Île de France Ouest (HUPO), Paris-Centre de Recherche Cardiovasculaire (PARCC - UMR-S U970), Hôpital Européen Georges Pompidou [APHP] (HEGP), Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP)-Hôpitaux Universitaires Paris Ouest - Hôpitaux Universitaires Île de France Ouest (HUPO)-Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP)-Hôpitaux Universitaires Paris Ouest - Hôpitaux Universitaires Île de France Ouest (HUPO)-Université Paris Descartes - Paris 5 (UPD5)-Institut National de la Santé et de la Recherche Médicale (INSERM), Université Pierre et Marie Curie - Paris 6 (UPMC)-École Pratique des Hautes Études (EPHE), and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Université Paris Descartes - Paris 5 (UPD5)-Institut National de la Santé et de la Recherche Médicale (INSERM)

Subjects
Male, [SDV]Life Sciences [q-bio], MESH: Membrane Glycoproteins, Nephron, MESH: Rats, Sprague-Dawley, 030204 cardiovascular system & hematology, Kidney, Cell membrane, Rats, Sprague-Dawley, MESH: Quaternary Ammonium Compounds, 0302 clinical medicine, MESH: Animals, MESH: Ammonia, 0303 health sciences, Membrane Glycoproteins, biology, MESH: Immunoblotting, General Medicine, medicine.anatomical_structure, Nephrology, RHAG, medicine.medical_specialty, Kidney Cortex, MESH: Rats, Immunoblotting, MESH: Carrier Proteins, 03 medical and health sciences, Ammonia, Internal medicine, medicine, Animals, Intercalated Cell, RNA, Messenger, Ammonia transporter, MESH: Nephrons, 030304 developmental biology, MESH: RNA, Messenger, Cell Membrane, Nephrons, MESH: Kidney, Apical membrane, Molecular biology, MESH: Male, Rats, Quaternary Ammonium Compounds, MESH: Kidney Cortex, Endocrinology, RHCG, biology.protein, Immunologic Techniques, MESH: Immunologic Techniques, Carrier Proteins, MESH: Cell Membrane
Abstract

International audience; Two non-erythroid members of the erythrocyte Rhesus (Rh) protein family, RhBG and RhCG, have been recently cloned in the kidney. These proteins share homologies with specific NH(3)/NH(4)(+) transporters (Mep/Amt) in primitive organisms and plants. When expressed in a Mep-deficient yeast, RhCG can function as a bidirectional NH(3)/NH(4)(+) transporter. The aim of this study was to determine the intrarenal and intracellular location of RhCG in rat kidney. RT-PCR on microdissected rat nephron segments demonstrated expression of mRNAs encoding RhCG in distal convoluted tubules, connecting ducts, and cortical and outer medullary collecting ducts but not in proximal tubules and thick ascending limbs of Henle's loop. Immunolocalization studies performed on rat kidney sections with rabbit anti-human RhCG 31 to 48 antibody showed labeling of the apical pole of tubular cells within the cortex, the outer medulla, and the upper portion of the inner medulla. All cells within connecting tubules had identical apical staining. In cortical collecting ducts, a subpopulation of cells that has either apical staining (alpha-intercalated cells) or diffuse staining (beta-intercalated cells) for the beta1 subunit of the H(+)-ATPase, was heavily stained at their apical pole with the RhCG antibody while principal cells identified as H(+)-ATPase negative cells showed a faint apical staining for RhCG that was much less intense than in adjacent intercalated cells. In the outer medulla and the upper portion of the inner medulla, RhCG labeling was restricted to a subpopulation of cells within the collecting duct that apically express the beta1 subunit of the H(+)-ATPase, indicating that RhCG expression in medullary collecting ducts is restricted to intercalated cells. No labeling was seen in glomeruli, proximal tubules, and limbs of Henle's loop. Immunoblotting of apical membrane fractions from rat kidney cortex with the rabbit anti-human RhCG 31 to 48 antibody revealed a doublet band at approximatively 65 kD.

Published
2002

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