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International audience; Dear Editor, Loss-of-function and gain-of-function mutations in the KCNH2 gene cause long and short-QT syndromes (LQTS or SQTS), respectively, predisposing to life-threatening F I G U R E 1 Repolarization power of wild-type (WT) hERG as a function of temperature. A simplified and optimized action potential was applied (AP-clamp) by an automated patch clamp system in 384-well plates on HEK293 cells stably expressing hERG. (A) Mean (± SEM) current recordings during AP-clamp at various temperatures (in pA, n = 194, 211, 114 and 172 cells at 22-37 • C, respectively). Dashed line: AP time course (voltage scale: right Y axis). (B) Mean (± SEM) current recordings during AP-clamp at 27 • C for AP of various durations (see inset for APs; for currents: n = 168−254 for Time x 0.5 to x 5). The small inward current observed in (A) and (B), when the AP is returning to resting values, is attributed to contamination of the intracellular solution by the extracellular Tyrode solution, intrinsic to the cell catch process in the automated patch clamp (see supplementary information). (C) Mean (± SEM) time integral of the recorded currents: repolarization power, at various temperatures versus time factor (n = 155−232, 168−254, 79−133 and 144−173 at 22-37 • C, respectively). Horizontal dashed line: repolarization power at 37 • C: 22.3 pA.s. (D) As in (B), at 27 • C, after time and current corrections using various factors from 1.5 to 3 on the respective recordings. For example, for the recordings obtained during the AP of 2 x duration, the time was divided by 2 and the current multiplied by 2. Note the overlap of the current corrected by the factor of 2 at 27 • C (black) with the reference current obtained during the standard AP at 37 • C (red).

Background and purpose Protoxin II (ProTx II) is a high affinity gating modifier that is thought to selectively block the Nav 1.7 voltage-dependent Na+ channel, a major therapeutic target for the control of pain. We aimed at producing ProTx II analogues entitled with novel functionalities for cell distribution studies and biochemical characterization of its Nav channel targets. Experimental approach We took advantage of the high affinity properties of the peptide, combined to its slow off rate, to design a number of new tagged analogues useful for imaging and biochemistry purposes. We used high-throughput automated patch-clamp to identify the analogues best matching the native properties of ProTx II and validated them on various Nav -expressing cells in pull-down and cell distribution studies. Key results Two of the produced ProTx II analogues, Biot-ProTx II and ATTO488-ProTx II, best recapitulate the pharmacological properties of unlabelled ProTx II, while other analogues remain high affinity blockers of Nav 1.7. The biotinylated version of ProTx II efficiently works for the pull-down of several Nav isoforms tested in a concentration-dependent manner, while the fluorescent ATTO488-ProTx II specifically labels the Nav 1.7 channel over other Nav isoforms tested in various experimental conditions. Conclusions and implications The properties of these ProTx II analogues as tools for Nav channel purification and cell distribution studies pave the way for a better understanding of ProTx II channel receptors in pain and their pathophysiological implications in sensory neuronal processing. The new fluorescent ProTx II should also reveal itself useful for the design of new drug screening strategies.

Childhood-Onset Schizophrenia (COS) is a very rare and severe psychiatric disorder defined by adult schizophrenia symptoms occurring before the age of 13. We report a microduplication in the 10q26.3 region including part of the Inositol Polyphosphate-5-Phosphatase A (INPP5A) gene that segregates with Schizophrenia Spectrum Disorders (SSDs) in the family of a female patient affected by both COS and Autism Spectrum Disorder (ASD). Phenotyping and genotyping (including CGH-array) were performed for mother, healthy sister, and affected child according to the GenAuDiss protocol (NCT02565524). The duplication size is 324 kb and is present in a patient with COS and in her mother with SSD, but not in the patient's healthy sister. INPP5A encodes a membrane-associated 43 kDa type I inositol 1,4,5-trisphosphate (InsP3) 5-phosphatase. This protein is found both in mouse and human brains and we found that its Drosophila homologue 5PtaseI is specifically expressed in the central nervous system. Hydrolyzed products from InsP3 5-phosphatases mobilize intracellular calcium, which is relevant for dendritic spine morphogenesis in neurons and altered in both schizophrenia and ASD. These may constitute arguments in favor of this gene alteration in the pathophysiology of COS.

Melanin-concentrating hormone (MCH) is a ubiquitous vertebrate neuropeptide predominantly synthesized by neurons of the diencephalon that can act through two G protein-coupled receptors, called MCHR1 and MCHR2. The expression of Mchr1 has been investigated in both rats and mice, but its synthesis remains poorly described. After identifying an antibody that detects MCHR1 with high specificity, we employed immunohistochemistry to map the distribution of MCHR1 in the CNS of rats and mice. Multiple neurochemical markers were also employed to characterize some of the neuronal populations that synthesize MCHR1. Our results show that MCHR1 is abundantly found in a subcellular structure called the primary cilium, which has been associated, among other functions, with the detection of free neurochemical messengers present in the extracellular space. Ciliary MCHR1 was found in a wide range of areas, including the olfactory bulb, cortical mantle, striatum, hippocampal formation, amygdala, midline thalamic nuclei, periventricular hypothalamic nuclei, midbrain areas, and in the spinal cord. No differences were observed between male and female mice, and interspecies differences were found in the caudate-putamen nucleus and the subgranular zone. Ciliary MCHR1 was found in close association with several neurochemical markers, including tyrosine hydroxylase, calretinin, kisspeptin, estrogen receptor, oxytocin, vasopressin, and corticotropin-releasing factor. Given the role of neuronal primary cilia in sensing free neurochemical messengers in the extracellular fluid, the widespread distribution of ciliary MCHR1, and the diverse neurochemical populations who synthesize MCHR1, our data indicate that nonsynaptic communication plays a prominent role in the normal function of the MCH system.

Background and aims Mutations in KCNH2 cause long or short QT syndromes (LQTS or SQTS) predisposing to life‐threatening arrhythmias. Over 1000 hERG variants have been described by clinicians, but most remain to be characterised. The objective is to standardise and accelerate the phenotyping process to contribute to clinician diagnosis and patient counselling. In silico evaluation was also included to characterise the structural impact of the variants. Methods We selected 11 variants from known LQTS patients and two variants for which diagnosis was problematic. Using the Gibson assembly strategy, we efficiently introduced mutations in hERG cDNA despite GC‐rich sequences. A pH‐sensitive fluorescent tag was fused to hERG for efficient evaluation of channel trafficking. An optimised 35‐s patch‐clamp protocol was developed to evaluate hERG channel activity in transfected cells. R software was used to speed up analyses. Results In the present work, we observed a good correlation between cell surface expression, assessed by the pH‐sensitive tag, and current densities. Also, we showed that the new biophysical protocol allows a significant gain of time in recording ion channel properties and provides extensive information on WT and variant channel biophysical parameters, that can all be recapitulated in a single parameter defined herein as the repolarisation power. The impacts of the variants on channel structure were also reported where structural information was available. These three readouts (trafficking, repolarisation power and structural impact) define three pathogenicity indexes that may help clinical diagnosis. Conclusions Fast‐track characterisation of KCNH2 genetic variants shows its relevance to discriminate mutants that affect hERG channel activity from variants with undetectable effects. It also helped the diagnosis of two new variants. This information is meant to fill a patient database, as a basis for personalised medicine. The next steps will be to further accelerate the process using an automated patch‐clamp system., We developed a method for rapid analysis of the properties of new hERG channel variants that is helpful for clinicians to diagnose an arrhythmia and help counseling the patient. This method is rapid enough to provide a complete set of channel properties and will set the stage for a more extensive characterization in the future.

International audience; Abbreviations: 3xTG, transgenic mice expressing human APP, MAPT, and PSEN1 genes with three familial mutations; 5xFAD, transgenic mice expressing human APP and PSEN1 genes with five familial mutations; AD, Alzheimer's disease; ADAM, a disintegrin and metalloprotease; APP, amyloid protein precursor; Aβ, beta-amyloid peptide; BACE-1, beta-site APP-cleaving enzyme-1; C3, BACE-1 inhibitor IV; C99/C83, APP CTF of 99/83 amino acids; CAT-, deletion of the catalytic domain; CTF, C-terminal fragment; DAPT, γ-secretase inhibitor; EXT-, deletion of the extracellular domain; GFP, green fluorescent protein; HEKswe, human embryonic kidney cells carrying the APP Swedish mutation; HPX-, deletion of the hemopexin domain; HRP, horseradish peroxidase enzyme; IC-, deletion of the intracytoplasmic domain; MMP, matrix metalloproteinase; MT1/5-MMP, membrane-type 1/5 matrix metalloproteinase; MT1/5Δ-MMP, catalytically inactive MT1-MMP or MT5-MMP; MTT, 3-(4,5-Dimethylthiazol-2yl)-2,5-diphenyl tetrazolium bromide; PSEN 1(2), presenilin 1 and 2; qPCR, quantitative polymerase chain reaction; RFP, red fluorescent protein; RXP03, MMP inhibitor; sAPP95, soluble amyloid protein precursor fragment generated by MT5-MMP; sAPPFL, full-length soluble amyloid protein precursor; sAPPα/β, soluble APPα/β; Tf, transferrin; TIMP, tissue inhibitor of MMPs; TIMP-1Δ, inactive TIMP-1; TM/IC-, deletion of the transmembrane and intracytoplasmic domains.

International audience; Memory CD8(+) T lymphocytes are critical effector cells of the adaptive immune system mediating long-lived pathogen-specific protective immunity. Three signals - antigen, costimulation and inflammation - orchestrate optimal CD8(+) T-cell priming and differentiation into effector and memory cells and shape T-cell functional fate and ability to protect against challenge infections. While among the conventional spleen DCs (cDCs), the CD8α(+) but not the CD8α(-) cDCs most efficiently mediate CD8(+) T-cell priming, it is unclear which subset, irrespective of their capacity to process MHC class I-associated antigens, is most efficient at inducing naïve CD8(+) T-cell differentiation into pathogen-specific protective memory cells in vivo. Moreover, the origin of the required signals is still unclear. Using mice infected with the intracellular bacterium Listeria monocytogenes, we show that splenic CD8α(+) cDCs become endowed with all functional features to optimally prime protective memory CD8(+) T cells in vivo within only a few hours post-immunization. Such programming requires both cytosolic signals resulting from bacterial invasion of the host cells and extracellular inflammatory mediators. Thus, these data designate these cells as the best candidates to facilitate the development of cell-based vaccine therapy.

International audience; Secreted phospholipases A2 (sPLA2s) are present in atherosclerotic plaques and are now considered novel attractive therapeutic targets and potential biomarkers as they contribute to the development of atherosclerosis through lipoprotein-dependent and independent mechanisms. We have previously shown that hGX-sPLA2-phospholipolyzed LDL (LDL-X) induces proinflammatory responses in human umbilical endothelial cells (HUVECs); here we explore the molecular mechanisms involved. Global transcriptional gene expression profiling of the response of endothelial cells exposed to either LDL or LDL-X revealed that LDL-X activates multiple distinct cellular pathways including the unfolded protein response (UPR). Mechanistic insight showed that LDL-X activates UPR through calcium depletion of intracellular stores, which in turn disturbs cytoskeleton organization. Treatment of HUVECs and aortic endothelial cells (HAECs) with LDL-X led to activation of all 3 proximal initiators of UPR: eIF-2alpha, IRE1alpha, and ATF6. In parallel, we observed a sustained phosphorylation of the p38 pathway resulting in the phosphorylation of AP-1 downstream targets. This was accompanied by significant production of the proinflammatory cytokines IL-6 and IL-8. Our study demonstrates that phospholipolyzed LDL uses a range of molecular pathways including UPR to initiate endothelial cell perturbation and thus provides an LDL oxidation-independent mechanism for the initiation of vascular inflammation in atherosclerosis.-Gora, S., Maouche, S., Atout, R., Wanherdrick, K., Lambeau, G., Cambien, F., Ninio, E., Karabina, S.-A. Phospholipolyzed LDL induces an inflammatory response in endothelial cells through endoplasmic reticulum stress signaling.

International audience; Autosomal dominant polycystic kidney disease (ADPKD) is caused by mutations in two genes, PKD1 and PKD2, which encode polycystin-1 (PC1) and polycystin-2 (PC2), respectively. Earlier work has shown that PC1 and PC2 assemble into a polycystin complex implicated in kidney morphogenesis. PC2 also assembles into homomers of uncertain functional significance. However, little is known about the molecular mechanisms that direct polycystin complex assembly and specify its functions. We have identified a coiled coil in the C-terminus of PC2 that functions as a homodimerization domain essential for PC1 binding but not for its self-oligomerization. Dimerization-defective PC2 mutants were unable to reconstitute PC1/PC2 complexes either at the plasma membrane (PM) or at PM-endoplasmic reticulum (ER) junctions but could still function as ER Ca(2+)-release channels. Expression of dimerization-defective PC2 mutants in zebrafish resulted in a cystic phenotype but had lesser effects on organ laterality. We conclude that C-terminal dimerization of PC2 specifies the formation of polycystin complexes but not formation of ER-localized PC2 channels. Mutations that affect PC2 C-terminal homo- and heteromerization are the likely molecular basis of cyst formation in ADPKD.

J. Neurochem. (2009) 109, 819–825. Abstract Controversial debates still remain around the nature of the etiologic agent responsible for Amyotrophic lateral sclerosis/Parkinson dementia complex (ALS/PDC) whose incidence is unusually high among the population of the pacific island of Guam. It has been hypothesized that the neurotoxin β-N-methylamino-l-alanine (l-BMAA) produced by cyanobacteria in the roots of Cycas Circinalis seeds might trigger ALS/PDC. Frequently observed in patients with ALS/PDC, retinopathy is one of the clinical features of the disease. The effect of the l-BMAA on cell viability was examined in vivo by measuring the electrophysiological activity of the mouse retinal neurons by electroretinography recordings. Intra-ocular injections of l-BMAA selectively reduced the b-wave amplitude, without affecting neither the a-wave amplitude nor the a- and b-latencies. The cell death of retinal cells was evidenced by histology on retina sections, caspase 3 activation, incorporation of propidium iodide and production of reactive oxygen species. Co-injection with the specific NMDA antagonist, MK-801, significantly protected the retinal neurons from l-BMAA/NMDA-induced apoptosis. We provide evidence that l-BMAA induced neuronal cell death in vivo supporting a direct causal link between l-BMAA and neuronal damages.

Doppel (Dpl) shares common structural features with the prion protein (PrP) whose pathologic isoform is considered as the causative agent of prion diseases. Although their physiological functions in the immune system remain largely unknown, we demonstrated that substantial amounts of PrP and Dpl are expressed by spleen cells notably B lymphocytes, granulocytes and DC, but not T lymphocytes and NK. To characterize trans-interacting partners of PrP and Dpl on mouse splenocytes, fluorescent PrP and Dpl tetramers were produced and used as tracers. Both tetramers specifically bind to B lymphocytes, dendritic cells, macrophages and granulocytes and in a lesser extend to T lymphocytes. No binding was observed on NK, follicular dendritic cells and mesenchymal spleen cells. The activation of intracellular transduction signals (i.e. intracellular calcium concentration and activation of the MAP kinase pathway) suggested that PrP and Dpl tetramers bind to functional receptors on B cells. None of the previously described PrP partners account for the binding sites characterized here. Our study suggests a possible role for PrP and Dpl in the cell-cell interactions in the immune system.

We recently demonstrated that the presenilin-dependent gamma-secretase complex regulates the expression and activity of neprilysin, one of the main enzymes that degrade the amyloid beta-peptide (Abeta) which accumulates in Alzheimer's disease. Here, we examined the influence of endogenous nicastrin (NCT), a member of the gamma-secretase complex, on neprilysin physiology. We show that nicastrin deficiency drastically lowers neprilysin expression, membrane-bound activity and mRNA levels, but it did not modulate the expression of two other putative Abeta-cleaving enzymes, endothelin-converting enzyme and insulin-degrading enzyme. Furthermore, we show that nicastrin restores neprilysin activity and expression in nicastrin-deficient, but not presenilin-deficient fibroblasts, indicating that the control of neprilysin necessitates the complete gamma-secretase complex harbouring its four reported components. Finally, we show that NCT expression peaked 24 h after NCT cDNA transfection of wild-type and NCT-/- fibroblasts, while neprilysin expression drastically increased only after 36 h and was maximal at 48 h. This delayed effect on neprilysin expression correlates well with our demonstration of an indirect gamma-secretase-dependent modulation of neprilysin at its transcriptional level.

ArfGAP1 promotes GTP hydrolysis in Arf1, a small G protein that interacts with lipid membranes and drives the assembly of the COPI coat in a GTP-dependent manner. The activity of ArfGAP1 increases with membrane curvature, suggesting a negative feedback loop in which COPI-induced membrane deformation determines the timing and location of GTP hydrolysis within a coated bud. Here we show that a central sequence of about 40 amino acids in ArfGAP1 acts as a lipid-packing sensor. This ALPS motif (ArfGAP1 Lipid Packing Sensor) is also found in the yeast homologue Gcs1p and is necessary for coupling ArfGAP1 activity with membrane curvature. The ALPS motif binds avidly to small liposomes and shows the same hypersensitivity on liposome radius as full-length ArfGAP1. Site-directed mutagenesis, limited proteolysis and circular dichroism experiments suggest that the ALPS motif, which is unstructured in solution, inserts bulky hydrophobic residues between loosely packed lipids and forms an amphipathic helix on highly curved membranes. This helix differs from classical amphipathic helices by the abundance of serine and threonine residues on its polar face.

The 2P domain K(+) channel TREK-1 is widely expres sed in the nervous system. It is opened by a variety of physical and chemical stimuli including membrane stretch, intracellular acidosis and polyunsaturated fatty acids. This activation can be reversed by PKA-mediated phosphorylation. The C-terminal domain of TREK-1 is critical for its polymodal function. We demonstrate that the conversion of a specific glutamate residue (E306) to an alanine in this region locks TREK-1 in the open configuration and abolishes the cAMP/PKA down-modulation. The E306A substitution mimics intracellular acidosis and rescues both lipid- and mechano-sensitivity of a loss-of-function truncated TREK-1 mutant. We conclude that protonation of E306 tunes the TREK-1 mechanical setpoint and thus sets lipid sensitivity.

The FMRF-amide-activated sodium channel (FaNaC), a member of the ENaC/Degenerin family, is a homotetramer, each subunit containing two transmembrane segments. We changed independently every residue of the first transmembrane segment (TM1) into a cysteine and tested each position's accessibility to the cysteine covalent reagents MTSET and MTSES. Eleven mutants were accessible to the cationic MTSET, showing that TM1 faces the ion translocation pathway. This was confirmed by the accessibility of cysteines present in the acid-sensing ion channels and other mutations introduced in FaNaC TM1. Modification of accessibilities for positions 69, 71 and 72 in the open state shows that the gating mechanism consists of the opening of a constriction close to the intracellular side. The anionic MTSES did not penetrate into the channel, indicating the presence of a charge selectivity filter in the outer vestibule. Furthermore, amiloride inhibition resulted in the channel occlusion in the middle of the pore. Summarizing, the ionic pore of FaNaC includes a large aqueous cavity, with a charge selectivity filter in the outer vestibule and the gate close to the interior.

International audience; Results reported in this work suggest a potential therapeutic value of polyunsaturated fatty acids for cerebral pathologies as previously proposed by others for cardiac diseases. We show that the polyunsatur-ated fatty acid linolenic acid prevents neuronal death in an animal model of transient global ischemia even when administered after the insult. Linolenic acid also protects animals treated with kainate against seizures and hippocampal lesions. The same effects have been observed in an in vitro model of seizure-like activity using glutamatergic neurons and they have been shown to be associated with blockade of glutamatergic transmission by low concentrations of distinct poly-unsaturated fatty acids. Our data suggest that the opening of background K + channels, like TREK-1 and TRAAK, which are activated by arachidonic acid and other polyunsaturated fatty acids such as docosahexa-enoic acid and linolenic acid, is a signi®cant factor in this neuroprotective effect. These channels are abundant in the brain where they are located both pre-and post-synaptically, and are insensitive to saturated fatty acids, which offer no neuroprotection.

International audience; We have recently discovered a new class of potassium channels with two pore-forming domains and four membrane-spanning domains. When heterologously expressed, these channels produce time- and voltage-independent currents that classify them as background or leak channels. TWIK (for tandem of P domains in a weak inwardly rectifying K+ channel) was the first member of this family to be cloned. Here, we describe the genomic organization of TWIK in the mouse. The coding sequence as well as the untranslated sequences are contained in three exons. The twik gene (or KCNK1) has been mapped to chromosome 8, consistent with its localization to 1q42-43 in human. The twik gene is expressed in virtually all mouse tissues. It is most abundantly expressed in brain and moderately in other organs such as kidney. The level of expression is increased in brain and kidney from neonate to adult animals, but the TWIK message is also detected during embryogenesis, as early as day 7 post conception.

1. The effects of noradrenaline (NA) were studied on vascular smooth muscle cells isolated from rat portal vein. 2. Two types of single-Ca2+ channel currents with conductances of 17 pS and 8 pS were obtained in cell-attached configuration. Bath application of NA increased the open probability of both channels during depolarizing pulses without a change of background membrane conductance. However, NA did not open Ca2+ channels when the membrane patch potential was held at -50 mV, which is about the resting potential in physiological conditions. 3. In the whole-cell configuration, studies of voltage-dependent Ca2+ channel currents showed that the peak conductance curve was not shifted to more negative potentials by NA. 4. Measurements of internal Ca(2+)-concentration ([Ca2+]i) with Indo-1 indicated that NA increased [Ca2+]i at a holding potential of -50 mV and evoked a Ca(2+)-activated Cl- current. These effects were blocked when heparin was included in the pipette solution. 5. A Cl- channel blocker without effect on Ca2+ channels (anthracene-9-carboxylic acid) inhibited the contractions of portal vein strips induced by NA in a manner similar to that produced by a Ca2+ channel inhibitor (isradipine). The NA-induced contraction was completely suppressed in the presence of ryanodine which depletes intracellular Ca2+ stores. 6. The present study suggests that activation of Cl- channels by Ca2+ release produces a membrane depolarization which is a prerequisite for enhanced opening of voltage-dependent Ca2+ channels in response to NA in venous smooth muscle.

International audience