Molecular Determinant for Specific Ca/Ba Selectivity Profiles of Low and High Threshold Ca2+ Channels

Voltage-gated Ca2+ channels (VGCC) play a key role in many physiological functions by their high selectivity for Ca2+ over other divalent and monovalent cations in physiological situations. Divalent/monovalent selection is shared by all VGCC and is satisfactorily explained by the existence, within the pore, of a set of four conserved glutamate/aspartate residues (EEEE locus) coordinating Ca2+ ions. This locus however does not explain either the choice of Ca2+ among other divalent cations or the specific conductances encountered in the different VGCC. Our systematic analysis of high- and low-threshold VGCC currents in the presence of Ca2+ and Ba2+ reveals highly specific selectivity profiles. Sequence analysis, molecular modeling, and mutational studies identify a set of nonconserved charged residues responsible for these profiles. In HVA (high voltage activated) channels, mutations of this set modify divalent cation selectivity and channel conductance without change in divalent/monovalent selection, activation, inactivation, and kinetics properties. The CaV2.1 selectivity profile is transferred to CaV2.3 when exchanging their residues at this location. Numerical simulations suggest modification in an external Ca2+ binding site in the channel pore directly involved in the choice of Ca2+, among other divalent physiological cations, as the main permeant cation for VGCC. In LVA (low voltage activated) channels, this locus (called DCS for divalent cation selectivity) also influences divalent cation selection, but our results suggest the existence of additional determinants to fully recapitulate all the differences encountered among LVA channels. These data therefore attribute to the DCS a unique role in the specific shaping of the Ca2+ influx between the different HVA channels

Cav2.1 C‐terminal fragments produced in Xenopus laevis oocytes do not modify the channel expression and functional properties

International audienceThe sequence and genomic organization of the CACNA1A gene that encodes the Cav2.1 subunit of both P and Q type Ca2+ channels are well conserved in mammals. In human, rat and mouse CACNA1A, the use of an alternative acceptor site at the exon 46‐47 boundary results in the expression of a long Cav2.1 splice variant. In transfected cells, the long isoform of human Cav2.1 produces a C‐terminal fragment, but it is not known whether this fragment affects Cav2.1 expression or functional properties. Here, we cloned the long isoform of rat Cav2.1 (Cav2.1(e47)) and identified a novel variant with a shorter C‐terminus (Cav2.1(e47s)) that differs from those previously described in the rat and mouse. When expressed in Xenopus laevis oocytes, Cav2.1(e47) and Cav2.1(e47s) displayed similar functional properties as the short isoform (Cav2.1). We show that Cav2.1 isoforms produced short (CT1) and long (CT1(e47)) C‐terminal fragments that interacted in vivo with the auxiliary Cavβ4a subunit. Overexpression of the C‐terminal fragments did not affect Cav2.1 expression and functional properties. Furthermore, the functional properties of a Cav2.1 mutant without the C‐terminal Cavβ4 binding domain (Cav2.1ΔCT2) were similar to those of Cav2.1, and were not influenced by the co‐expression of the missing fragments (CT2 or CT2(e47)). Our results exclude a functional role of the C‐terminal fragments in Cav2.1 biophysical properties in an expression system widely used to study this channel

Analyse de la cristallisation du PLA (Acide PolyLactique) sous écoulement : quantification des effets thermique et mécanique

Lors de l’injection de polymères, le cisaillement provoque une orientation macromoléculaire donnant lieu à une cristallisation supplémentaire Nous avons modélisé la cristallisation du PLA sous écoulement dans des conditions anisothermes et dans une configuration de cisaillement pur. Le modèle de cinétique de cristallisation est inspiré de celui développé par Boutaous et al. [1], basé sur une modification des models décrivant la théorie globale de germination-croissance [2, 3]. Tous les paramètres des modèles thermique, rhéologique et de cristallisation ont été identifiés grâce à des mesures spécifiques effectuées au laboratoire. Les résultats montrent que le matériau présente une succession de paliers correspondant à des changements de structure cristalline. Une quantification des effets thermique et de l’écoulement sur les cinétiques de cristallisation ainsi que sur la taille des entités cristallines sera présentée et analysée. Des observations sous lumière polarisée corroborent les résultats numériques. [1] M. Boutaous, P. Bourgin, M.Zinet, J. Non-Newt. Fluid Mech., 127, 227--237 (2010). [2] J.D. Hoffman, R.L. Miller, Polymer, 38, 3151--3212 (1997). [3] W. Schneider, A. Köll and J. Berger, Inter. Poly. Proc., 3, 4, 151-154, (1988

Targeting TMEM176B Enhances Antitumor Immunity and Augments the Efficacy of Immune Checkpoint Blockers by Unleashing Inflammasome Activation.

Although immune checkpoint blockers have yielded significant clinical benefits in patients with different malignancies, the efficacy of these therapies is still limited. Here, we show that disruption of transmembrane protein 176B (TMEM176B) contributes to CD8+ T cell-mediated tumor growth inhibition by unleashing inflammasome activation. Lack of Tmem176b enhances the antitumor activity of anti-CTLA-4 antibodies through mechanisms involving caspase-1/IL-1β activation. Accordingly, patients responding to checkpoint blockade therapies display an activated inflammasome signature. Finally, we identify BayK8644 as a potent TMEM176B inhibitor that promotes CD8+ T cell-mediated tumor control and reinforces the antitumor activity of both anti-CTLA-4 and anti-PD-1 antibodies. Thus, pharmacologic de-repression of the inflammasome by targeting TMEM176B may enhance the therapeutic efficacy of immune checkpoint blockers.Uruguay INNOVA 2, Fondo Maria Viñas and Clemente Estable from ANII, as well as grants from CABBIO, PEDECIBA, ECOS-SUD and FOCEM (MERCOSUR Structural Convergence Fund), COF 03/11 to MH, The Harry J Lloyd Foundation to MRG and the Instituto Nacional del Cancer to YDM, Agencia de Promoción Científica y Tecnológica to GAR and MRG, Fundación Bunge & Born and Fundación Sales to GA

Reconstructing Mayaro virus circulation in French Guiana shows frequent spillovers

Funder: This study was supported by the “European Regional Development Fund” under EPI-ARBO grant agreement (GY0008695), the “Regional Health Agency of French Guiana”, the “National Center of Spatial Studies”. CF acknowledges funding from Calmette and Yersin allocated by the “Pasteur Institut Department of International Affairs”. N.H. and S.C. acknowledge financial support from the AXA Research Fund, the Investissement d’Avenir program, the Laboratoire d’Excellence Integrative Biology of Emerging Infectious Diseases program (Grant ANR-10-LABX-62-IBEID), the Models of Infectious Disease Agent Study of the National Institute of General Medical Sciences, the INCEPTION project (PIA/ANR-16-CONV-0005), the European Union’s Horizon 2020 research and innovation programme under ZIKAlliance grant agreement No 734548.Abstract: Characterizing the circulation of Mayaro virus (MAYV), an emerging arbovirus threat, is essential for risk assessment but challenging due to cross-reactivity with other alphaviruses such as chikungunya virus (CHIKV). Here, we develop an analytical framework to jointly assess MAYV epidemiology and the extent of cross-reactivity with CHIKV from serological data collected throughout French Guiana (N = 2697). We find strong evidence of an important sylvatic cycle for MAYV with most infections occurring near the natural reservoir in rural areas and in individuals more likely to go to the forest (i.e., adult males) and with seroprevalences of up to 18% in some areas. These findings highlight the need to strengthen MAYV surveillance in the region and showcase how modeling can improve interpretation of cross-reacting assays

PIKfyve regulates CaV1.2 degradation and prevents excitotoxic cell death

Neuronal Ca levels are regulated by glutamate receptor activation, which recruits PIKfyve to voltage-gated Ca channels, prompting their degradation

BMJ Med

OBJECTIVE: To evaluate the efficacy of covid-19 convalescent plasma to treat patients admitted to hospital for moderate covid-19 disease with or without underlying immunodeficiency (CORIPLASM trial). DESIGN: Open label, randomised clinical trial. SETTING: CORIMUNO-19 cohort (publicly supported platform of open label, randomised controlled trials of immune modulatory drugs in patients admitted to hospital with moderate or severe covid-19 disease) based on 19 university and general hospitals across France, from 16 April 2020 to 21 April 2021. PARTICIPANTS: 120 adults (n=60 in the covid-19 convalescent plasma group, n=60 in the usual care group) admitted to hospital with a positive SARS-CoV2 test result, duration of symptoms 40. MAIN OUTCOME MEASURES: Primary outcomes were proportion of patients with a WHO Clinical Progression Scale score of ≥6 on the 10 point scale on day 4 (higher values indicate a worse outcome), and survival without assisted ventilation or additional immunomodulatory treatment by day 14. Secondary outcomes were changes in WHO Clinical Progression Scale scores, overall survival, time to discharge, and time to end of dependence on oxygen supply. Predefined subgroups analyses included immunosuppression status, duration of symptoms before randomisation, and use of steroids. RESULTS: 120 patients were recruited and assigned to covid-19 convalescent plasma (n=60) or usual care (n=60), including 22 (covid-19 convalescent plasma) and 27 (usual care) patients who were immunocompromised. 13 (22%) patients who received convalescent plasma had a WHO Clinical Progression Scale score of ≥6 at day 4 versus eight (13%) patients who received usual care (adjusted odds ratio 1.88, 95% credible interval 0.71 to 5.24). By day 14, 19 (31.6%) patients in the convalescent plasma group and 20 (33.3%) patients in the usual care group needed ventilation, additional immunomodulatory treatment, or had died. For cumulative incidence of death, three (5%) patients in the convalescent plasma group and eight (13%) in the usual care group died by day 14 (adjusted hazard ratio 0.40, 95% confidence interval 0.10 to 1.53), and seven (12%) patients in the convalescent plasma group and 12 (20%) in the usual care group by day 28 (adjusted hazard ratio 0.51, 0.20 to 1.32). In a subgroup analysis performed in patients who were immunocompromised, transfusion of covid-19 convalescent plasma was associated with mortality (hazard ratio 0.39, 95% confidence interval 0.14 to 1.10). CONCLUSIONS: In this study, covid-19 convalescent plasma did not improve early outcomes in patients with moderate covid-19 disease. The efficacy of convalescent plasma in patients who are immunocompromised should be investigated further. TRIAL REGISTRATION: ClinicalTrials.gov NCT04345991

Séquences d'apparition de la lésion de sclérose en plaques lors du suivi hebdomadaire en IRM 3Tesla haute résolution

L'objectif de ce travail est de confirmer ou non le rôle de la rupture de BHE dans la formation de la lésion de SEP et de caractériser la séquence d'apparition de la lésion active en IRM. Cinq patients atteints de forme rémittente de SEP en phase active mais non traités, ont été recrutés après accord du comité d'éthique. Huit IRM hebdomadaires consécutives standardisées ont été réalisées pour chacun de ces patients, avec entre autres des séquences haute résolution 3D FLAIR et 3D Tl après injection de gadolinium. Ces séquences ont été recalées entre elles et pour chaque point temporel avec génération de matrice de soustraction et de Jacobien par rapport au premier point temporel. Chaque lésion active a été segmentée dans les trois dimensions de l'espace sur chacune des séquences par deux radiologues en aveugle et validée par un 3ème radiologue expert en neuroradiologie. La taille moyenne des lésions était inférieure à celle déjà décrite dans la littérature du fait de l'utilisation de l'IRM haute résolution. Néanmoins, les micro-lésions de moins de 10mm3, et/ou présentant une durée de rehaussement brève (inférieure à une semaine), paraissent être sous-estimées malgré cette exploration hebdomadaire en IRM 3T haute résolution. Ces micro-lésions pourraient expliquer en partie les modifications de la normal appearing white matter en transfert d'aimantation/diffusion bien décrites dans la littérature. Toutes les lésions actives en FLAIR ont présenté au cours de leur évolution une rupture de barrière hémato encéphalique (BHE), même si cette dernière ne parait pas forcément constituer l'évènement initial de leur formation: en effet 1l lésions sur 152 ont présenté une rupture de BHE après l'apparition de la lésion en FLAIR. Notre étude suggère la prépondérance de micro lésions indétectables avec les techniques d'imagerie conventionnelles. La rupture de la BHE est constante mais non obligatoirement inaugurale dans la formation de la lésion active de SEPLYON1-BU Santé (693882101) / SudocSudocFranceF

Régulations des canaux calciques activés par le voltage de type P/Q par le calcium et les protéines G

MONTPELLIER-BU Médecine UPM (341722108) / SudocPARIS-BIUP (751062107) / SudocMONTPELLIER-BU Médecine (341722104) / SudocSudocFranceF