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The human solute carrier 26 (SLC26) gene family of anion transporters consists of 10 members (SLC26A1-A11, A10 being a pseudogene) that encode membrane glycoproteins with 14 transmembrane segments and a C-terminal cytoplasmic sulfate transporter anti-sigma antagonist domain. Thus far, mutations in eight members of the SLC26 family (A1-A6, A8, and A9) have been linked to diseases in humans. Our goal is to characterize the role of N-glycosylation and the effect of mutations in SLC26A2 and A3 proteins on their functional expression in transfected HEK-293 cells. We found that certain mutants were retained in the endoplamic reticulum via an interaction with the lectin chaperone calnexin. Some could escape protein quality control and traffic to the cell surface upon removal of the N-glycosylation sites. Furthermore, we found that loss of N-glycosylation reduced expression of SLC26A2 at the cell surface. Loss of N-glycosylation had no effect on the stability of SLC26A3, yet resulted in a profound decrease in transport activity. Thus, N-glycosylation plays three roles in the functional expression of SLC26 proteins: (1) to retain misfolded proteins in the endoplamic reticulum, (2) to stabilize the protein at the cell surface, and (3) to maintain the transport protein in a functional state. Key words: anion transport, calnexin, glycoproteins, membrane proteins, protein trafficking, solute carriers (SLC), SLC26, transporters. La famille de transporteurs d'anions SLC26 (<< solute carrier 26 >>) chez l'humain comprend 10 membres (SLC26A1-A11, A10 etant un pseudogene) qui codent des glycoproteines comportant 14 segments transmembranaires et un domaine C-terminal cytoplasmique STAS (<< sulfate transporter anti-sigma6 >>). Jusqu'a present, des mutations au sein de huit membres de la famille SLC26 (A1-A6, A8 et A9) ont ete reliees a des maladies chez l'humain. L'objectif des auteurs consiste a caracteriser le role de la N-glycosylation et l'effet des mutations de SLC26A2 et A3 sur leur expression fonctionnelle chez les cellules HEK-293 transfectees. Ils ont trouve que certains mutants etaient gardes a l'interieur du reticulum endoplasmique par leur interaction avec la calnexine, une lectine chaperon. Certains d'entre eux pouvaient echapper au controle de qualite des proteines et se rendre a la surface cellulaire a la suite de la suppression des sites de N-glycosylation. Qui plus est, ils ont trouve que la perte de N-glycosylation reduisait l'expression de SLC26A2 a la surface cellulaire. La perte de N-glycosylation n'avait pas d'effet sur la stabilite de SLC26A3, mais donnait lieu, neanmoins, a une forte diminution de l'activite de transport. Ainsi, la N-glycosylation joue trois roles dans l'expression fonctionnelle des proteines SCL26 : (1) retenir les proteines mal repliees dans le reticulum endoplasmique, (2) stabiliser la proteine a la surface cellulaire et (3) maintenir la proteine de transport dans un etat fonctionnel. [Traduit par la Redaction] Mots-cles : transport d'anion, calnexine, glycoproteines, proteines membranaires, transport des proteines, transporteurs de solutes (SLC), SLC26, transporteurs., Introduction Solute carrier (SLC) proteins comprise some 456 members subdivided into 52 families of membrane transporters that play essential roles in human health and disease. Regardless, they are one of [...]

Pathological cardiac hypertrophy, the maladaptive remodelling of the myocardium, often progresses to heart failure. The sodium-proton exchanger (NHE1) and chloride-bicarbonate exchanger (AE3) have been implicated as important in the hypertrophic cascade. Carbonic anhydrase II (CAII) provides substrates for these transporters (protons and bicarbonate, respectively). CAII physically interacts with NHE1 and AE3, enhancing their respective ion transport activities by in creasing the concentration of substrate at their transport sites. Earlier studies found that a broad-spectrum carbonic anhydrase inhibitor prevented cardiomyocyte hypertrophy (CH), suggesting that carbonic anhydrase is important in the development of hypertrophy. Here we investigated whether cytosolic CAII was the CA isoform involved in hypertrophy. Neonatal rat ventricular myocytes (NRVMs) were transduced with recombinant adenoviral constructs to over-express wild-type or catalytically inactive CAII (CAII-V143Y). Over-expression of wild-type CAII in NRVMs did not affect CH development. In contrast, CAII-V143Y over-expression suppressed the response to hypertrophic stimuli, suggesting that CAII-V143Y behaves in a dominant negative fashion over endogenous CAII to suppress hypertrophy. We also examined CAII-deficient (Car2) mice, whose hearts exhibit physiological hypertrophy without any decrease in cardiac function. Moreover, cardiomyocytes from Car2 mice do not respond to prohypertrophic stimulation. Together, these findings support a role of CAII in promoting CH. Key words: cardiac hypertrophy, heart failure, carbonic anhydrase, bicarbonate transport, sodium-proton exchange, adenovirus, knockout mouse. L'hypertrophie cardiaque pathologique, un remodelage mal adapte du myocarde, evolue souvent vers l'insuffisance cardiaque. L'echangeur sodium-proton (NHE1) et l'echangeur chlorure-bicarbonate (AE3) ont ete impliques comme joueurs importants de la cascade hypertrophique. L'anhydrase carbonique II (CA II) fournit les substrats de ces transporteurs (protons et bicarbonate, respectivement). La CA II interagit physiquement avec NHE1 et AE3, augmentant leurs activites de transport ionique respectives en elevant la concentration de substrat aux sites de transport. Des etudes anterieures ont montre qu'un inhibiteur d'anhydrase carbonique a large spectre prevenait l'hypertrophie des cardiomyocytes (HC), s uggerant que l'anhydrase carbonique soit importante dans le developpement de l'hypertrophie. Nous examinons ici si la CA II cytosolique est l'isoforme de CA impliquee dans l'hypertrophie. Des myocytes ventriculaires de rats nouveaunes (MVRN) ont ete transduits avec des constructions adenovirales qui surexpriment la CA II sauvage ou une CAII inactive sur le plan catalytique (CAII-V143Y). La surexpression de CA II sauvage chez les MVRN n'affectait pas le developpement de l'HC. Au contraire, la surexpression de CAII-V143Y supprimait la reponse aux stimuli hypertrophiques, suggerant que la CAII-V143Y agit de facon dominante negative sur la CAII endogene pour supprimer l'hypertrophie. Nous avons aussi examine des souris depourvues de CAII (Car2), dont les coeurs presentent une hypertrophie physiologique sans diminution de la fonction cardiaque. Aussi, les cardiomyocytes des souris Car2 ne repondaient pas a une stimulation prohypertrophique. Dans l'ensemble, ces donnees appuient l'hypothese que la CAII favorise l'HC. Mots-cles: hypertrophie cardiaque, insuffisance cardiaque, anhydrase carbonique, transport du bicarbonate, echangeur sodium-proton, adenovirus, souris knockout. [Traduit par la Redaction], Introduction Cardiovascular pH regulation processes are implicated in the progression of pathological cardiac hypertrophy (Alvarez et al. 2001; Ennis et al. 2003; Hayasaki-Kajiwara et al. 1999; Karmazyn et al. 2003; [...]

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Casey JR, Sly WS, Shah GN, Aivarez BV. Bicarbonate homeostasis in excitable tissues: role of AE3 [Cl.sup.-]/HC[O.sup.-.sub.3] exchanger and carbonic anhydrase XIV interaction. Am J Physiol Cell Physiol 297: C1091-C1102, 2009. First published August 19, 2009; doi:10.1152/ajpcell.00177.2009.--Bicarbonate transport and metabolism are key elements of normal cellular function. Two alternate transcripts of anion exchanger 3 (AE3), full-length (AE3fl) and cardiac (AE3c), are expressed in central nervous system (CNS), where AE3 catalyzes electroneutral [Cl.sup.-]/HC[O.sup.-.sub.3] exchange across the plasma membrane of neuronal and glial cells of CNS. Anion exchanger isoforms, AE3fl and AE3c, associate with the carbonic anhydrases (CA) CAII and CAIV, forming a HC[O.sup.-.sub.3] transport metabolon, to maximize HCOf flux across the plasma membrane. CAXIV, with catalytic domain anchored to the extracellular surface, is also expressed in CNS. Here physical association of AE3 and CAXIV was examined by coimmunoprecipitation experiments, using mouse brain and retinal lysates. CAXIV immunoprecipitated with anti-AE3 antibody, and both AE3 isoforms were immunoprecipitated using antiCAXIV antibody, indicating CAXIV and AE3 interaction in the CNS. Confocal images revealed colocalization of CAXIV and AE3 in Mtiller and horizontal cells, in the mouse retina. [Cl.sup.-]/HC[O.sup.-.sub.3] exchange activity of AE3fl was investigated in transiently transfected human embryonic kidney 293 cells, using intracellular fluorescence measurements of BCECF, to monitor intracellular pH. CAXIV increased the rate of AE3fl-mediated HC[O.sup.-.sub.3] transport by up to 120%, which was suppressed by the CA inhibitor acetazolamide. Association of AE3 and CAXIV may represent a mechanism to enhance disposal of waste C[O.sub.2] and to balance pH in excitable tissues. bicarbonate transport metabolon; AE3/CAXIV complex; central nervous system doi: 10.1152/ajpcell.00177.2009.

Anion exchanger 3 (AE3), expressed in the brain, heart, and retina, extrudes intracellular HC[O.sup.-.sub.3] in exchange for extracellular [Cl.sup.-] . The SLC4A3 gene encodes two variants of AE3, brain or full-length AE3 ([AE3.sub.fl]) and cardiac AE3 (cAE3). Epilepsy is a heterogeneous group of disorders characterized by recurrent unprovoked seizures that affect about 50 million people worldwide. The AE3-A867D allele in humans has been associated with the development of IGE (IGE), which accounts for ~30% of all epilepsies. To examine the molecular basis for the association of the A867D allele with IGE, we characterized wild-type (WT) and AE3n-A867D in transfected human embryonic kidney (HEK)-293 cells. AE3n-A867D had significantly reduced transport activity relative to WT (54 [+ or -] 4%, P < 0.01). Differences in expression levels or the degree of protein trafficking to the plasma membrane did not account for the defect of [AE3.sub.fl]-A867D. Treatment with 8-bromo-cAMP (8-Br-cAMP) increased [Cl.sup.-]/HC[O.sup.-.sub.3] exchange activity of WT and [AE3.sub.fl]-A867D to a similar degree, which was abolished by preincubation with the protein kinase A (PKA)-specific inhibitor H89. This indicates that PKA regulates WT and [AE3.sub.fl]-A867D [Cl.sup.-]/HC[O.sup.-.sub.3] exchange activity. No difference in [Cl.sup.-]/HC[O.sup.-.sub.3] exchange activity was found between cultures of mixed populations of neonatal hippocampal cells from WT and [slc4a3.sup.-/-] mice. We conclude that the A867D allele is a functional (catalytic) mutant of AE3 and that the decreased activity of [AE3.sub.fl]-A867D may cause changes in cell volume and abnormal intracellular pH. In the brain, these alterations may promote neuron hyperexcitability and the generation of seizures. protein kinase A; intracellular pH

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The study aims to monitor the shifts in the strains of Streptococcus pneumoniae that cause acute otitis media (AOM) in children. The results show that the pneumococcal 7-valent conjugate vaccine (PCV7) and the 19A serotype proved successful in the treatment of the infections.

Association of some plasma membrane bicarbonate transporters with carbonic anhydrase enzymes forms a bicarbonate transport metabolon to facilitate metabolic C[O.sub.2]-HC[O.sup.-.sub.3] conversions and coupled HC[O.sup.-.sub.3] transport. The transmembrane carbonic anhydrase, CAIX, with its extracellular catalytic site, is highly expressed in parietal and other cells of gastric mucosa, suggesting a role in acid secretion. We examined in transfected HEK293 cells the functional and physical interactions between CAIX and the parietal cell [Cl.sup.-]/HC[O.sup.-.sub.3] exchanger AE2 or the putative [Cl.sup.-]/HC[O.sup.-.sub.3] exchanger SLC26A7. Coexpression of CAIX increased AE2 transport activity by 28 [+ or-] 7% and also activated transport mediated by AE1 and AE3 (32 [+ or -] 10 and 37 [+ or -] 9%, respectively). In contrast, despite a transport rate comparable to that of AE3, coexpressed CAIX did not alter transport associated with SLC26A7. The CAIX-associated increase of AE2 activity did not result from altered AE2 expression or cell surface processing. CAIX was coimmunoprecipitated with the coexpressed SLC4 polypeptides AE1, AE2, and AE3, but not with SLC26A7. GST pull-down assays with a series of domain-deleted forms of CAIX revealed that the catalytic domain of CAIX mediated interaction with AE2. AE2 and CAIX colocalized in human gastric mucosa, as indicated by co-immunofluorescence. This is the first example of a functional and physical interaction between a bicarbonate transporter and a transmembrane carbonic anhydrase. We conclude that CAIX can bind to some [Cl.sup.-]/HC[O.sup.-.sub.3] exchangers to form a bicarbonate transport metabolon. SLC4; SLC26; bicarbonate transport metabolon

Anion exchanger 1 (AE1; SLC4A1), the plasma membrane [Cl.sup.-]/HC[O.sup.-.sub.3] exchanger of erythrocytes, is also expressed in heart. The aim of this study was to assess the role of AE1 in heart function through study of AE1-null (AE[1.sup.-/-]) mice, which manifest severe hemolytic anemia resulting from erythrocyte fragility. Heart weight-to-body weight ratios were significantly higher in the AE[1.sup.-/-] mice than in wild-type (AE[1.sup.-/-]) littermates at both 1-3 days postnatal (3.01 [+ or -] 0.38 vs. 1.45 [+ or -] 0.04) and at 7 days postnatal (9.45 [+ or -] 0.53 vs. 4.13 [+ or -] 0.41), indicating that loss of AE1 led to cardiac hypertrophy. Heterozygous (AE[1.sup.+/-]) mice had no signs of cardiac hypertrophy. Morphology of the adult AE[1.sup.-/-] mutant heart revealed an increased left ventricular mass, accompanied by increased collagen deposition and fibrosis. M-mode echocardiography revealed dysfunction of the AE[1.sup.-/-] hearts, including dilated left ventricle end diastole and systole and expanded left ventricular mass compared with AE[1.sup.+/+] hearts. Expression of intracellular pH-regulatory mechanisms in the hypertrophic myocardium of neonate AE[1.sup.-/-] mutant mice was indistinguishable from AE[1.sup.+/-] and AE[1.sup.+/+] mice, as assessed by quantitative real-time RT-PCR. Confocal immunofluorescence revealed that, in normal mouse myocardium, AE1 is sarcolemmal, whereas AE3 and slc26a6 are found both at the sarcolemma and in internal membranes (T tubules and sarcoplasmic reticulum). These results indicate that AE[1.sup.-/-] mice, which suffer from severe hemolytic anemia and spherocytosis, display cardiac hypertrophy and impaired cardiac function, reminiscent of findings in patients with hereditary abnormalities of red blood cells. No essential role for AE1 in heart function was found. AE1; intracellular pH; [Cl.sup.-]/HC[O.sup.-.sub.3] exchange

Abstract: Bicarbonate is a simple single carbon molecule that plays surprisingly important roles in diverse biological processes. Among these are photosynthesis, the Krebs cycle, whole-body and cellular pH regulation, and [...]

The binding of carbonic anhydrase II (CAII) to the regulatory cytosolic domain of NHE1 is reported. The results show that a novel phosphorylation-regulated CAII binding site exists in distal amino acids of the NHE1 tail and Na(super +)/H(super +) exchanger activity is linked to bicarbonate based pH regulation through carbonic anhydrase activity.

Regulation of the human NBC3 [Na.sup.+]/HC[O.sup.-.sub.3] cotransporter by carbonic anhydrase II and PKA. Am J Physiol Cell Physiol 286: C1423-C1433, 2004. First published January 21, 2004; 10.1152/ajpcell.00382.2003.--Human NBC3 is an electroneutral [Na.sup.+]/HC[O.sup.-.sub.3] cotransporter expressed in heart, skeletal muscle, and kidney in which it plays an important role in HC[O.sup.-.sub.3] metabolism. Cytosolic enzyme carbonic anhydrase II (CAH) catalyzes the reaction C[O.sub.2] + [H.sub.2]O [TEXT NOT REPRODUCIBLE IN ASCII.] HC[O.sup.-.sub.3] + [H.sup.+] in many tissues. We investigated whether NBC3, like some [Cl.sup.-]/HC[O.sup.-.sub.3] exchange proteins, could bind CAII and whether PKA could regulate NBC3 activity through modulation of CAII binding. CAII bound the COOH-terminal domain of NBC3 (NBC3Ct) with [K.sub.d] = 101 nM; the interaction was stronger at acid pH. Cotransfection of HEK-293 cells with NBC3 and CAII recruited CAII to the plasma membrane. Mutagenesis of consensus CAII binding sites revealed that the D1135-D1136 region of NBC3 is essential for CAII/NBC3 interaction and for optimal function, because the NBC3 D1135N/Dl136N retained only 29 [+ or -] 22% of wild-type activity. Coexpression of the functionally dominant-negative CAII mutant V143Y with NBC3 or addition of 100 [micro]M 8-bromoadenosine to NBC3 transfected cells reduced intracellular pH (p[H.sub.i]) recovery rate by 31 [+ or -] 3, or 38 [+ or -] 7%, respectively, relative to untreated NBC3 transfected cells. The effects were additive, together decreasing the p[H.sub.i] recovery rate by 69 [+ or -] 12%, suggesting that PKA reduces transport activity by a mechanism independently of CAII Measurements of PKA-dependent phosphorylation by mass spectroscopy and labeling with [[[gamma].sup.-32]P]ATP showed that NBC3Ct was not a PKA substrate. These results demonstrate that NBC3 and CAII interact to maximize the HC[O.sup.-.sub.3] transport rate. Although PKA decreased NBC3 transport activity, it did so independently of the NBC3/CAII interaction and did not involve phosphorylation of NBC3Ct. pH regulation; bicarbonate transport; metabolon

Objective. To conduct a meta-analysis of randomized, controlled trials of cephalosporin versus penicillin treatment of group A [beta]-hemolytic streptococcal (GABHS) tonsillopharyngitis in children. Mthodology. Medline, Embase, reference lists, and abstract searches were conducted to identify randomized, controlled trials of cephalosporin versus penicillin treatment of GABHS tonsillopharyngitis in children. Trials were included if they met the following criteria: patients Results. Thirty-five trials involving 7125 patients were included in the meta-analysis. The overall summary odds ratio (OR) for the bacteriologic cure rate significantly favored cephalosporins compared with penicillin (OR: 3.02; 95% confidence interval [CI]: 2.49-3.67, with the individual cephalosporins [cephalexin, cefadroxil, cefuroxime, cefpodoxime, cefprozil, cefixime, ceftibuten, and cefdinir] showing superior bacteriologic cure rates). The overall summary OR for clinical cure rate was 2.33 (95% CI: 1.84-2.97), significantly favoring the same individual cephalosporins. There was a trend for diminishing bacterial cure with penicillin over time, comparing the trials published in the 1970s, 1980s, and 1990s. Sensitivity analyses for bacterial cure significantly favored cephalosporin treatment over penicillin treatment when trials were grouped as double-blind (OR: 2.31; 95% CI: 1.39-3.85), high-quality (OR: 2.50; 95% Ch 1.85-3.36) trials with well-defined clinical status (OR: 2.12; 95% CI: 1.54-2.90), with detailed compliance monitoring (OR: 2.85; 95% CI: 2.33-3.47), with GABHS serotyping (OR: 3.10; 95% CI: 2.42-3.98), with carriers eliminated (OR: 2.51; 95% CI: 1.55-4.08), and with test of cure 3 to 14 days posttreatment (OR: 3.53; 95% CI: 2.75-4.54). Analysis of comparative bacteriologic cure rates for the 3 generations of cephalosporins did not show a difference. Conclusions. This meta-analysis indicates that the likelihood of bacteriologic and clinical failure of GABHS tonsillopharyngitis is significantly less if an oral cephalosporin is prescribed, compared with oral penicillin. Pediatrics 2004;113:866-882; meta-analysis, cephalosporin, penicillin, group A streptococcus, pharyngitis., Penicillin has been the agent of choice for treatment of group A t-hemolytic streptococcal (GABHS) tonsillopharyngitis for the past 5 decades as advocated by the American Heart Association, (1) the [...]

COOH-terminal cytoplasmic tails of chloride/bicarbonate anion exchangers (AE) bind cytosolic carbonic anhydrase II (CAII) to form a bicarbonate transport metabolon, a membrane protein complex that accelerates transmembrane bicarbonate flux. To determine whether interaction with CAII affects the downregulated in adenoma (DRA) chloride/bicarbonate exchanger, anion exchange activity of DRA-transfected HEK-293 cells was monitored by following changes in intracellular pH associated with bicarbonate transport. DRA-mediated bicarbonate transport activity of 18 53 [+ or -] 1 mM [H.sup.+] equivalents/min was inhibited 53 [+ or -] 2% by 100 mM of the CAII inhibitor, acetazolamide, but was unaffected by the membrane-impermeant carbonic anhydrase inhibitor, 1-[5-sulfamoyl-1,3,4-thiadiazol-2-yl-(aminosulfonyl-4-phenyl)] -2,6-dimethyl-4-pheny]-pyridinium perchlorate. Compared with AE1, the COOH-terminal tail of DRA interacted weakly with CAII. Overexpression of a functionally inactive CAII mutant, V143Y, reduced AE1 transport activity by 61 53 [+ or -] 4% without effect on DRA transport activity (105 [+ or -] 7% transport activity relative to DRA alone). We conclude that cytosolic CAII is required for full DRA-mediated bicarbonate transport. However, DRA differs from other bicarbonate transport proteins because its transport activity is not stimulated by direct interaction with CAII. metabolon; chloride/bicarbonate exchanger; downregulated in adenoma

THE HISTORIOGRAPHY OF Irish America dates back to Thomas D'Arcy McGee's A History of the Irish Settlers in North America (1851). McGee concluded his preface by expressing 'the hope that [...]

The TM7-10 region of the erythrocyte membrane anion exchanger AE1 appears to contain the active site of the protein. AE1 is inhibited by stilbene disulfonate compounds and these compounds prevented the labeling of these residues by biotin maleimide.

Hallab, Mary Y. Vampire God: The Allure of the Undead in Western Culture. Albany: State University of New York Press, 2009. 169 pp. Paperback. ISBN 978-1-4384-2860-4. $24.95. Mary Hallab pushes [...]