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La cellule ß pancréatique sécrète l’insuline, la seule hormone capable de diminuer la concentration en glucose plasmatique. L'insuline est sécrétée de manière régulée sous l’influence de divers stimuli dont avant tout l’élévation de la glycémie, celle-ci augmentant lors de chaque repas. Elle est donc essentielle à la préservation de l'homéostasie du glucose. Son importance est attestée par le développement du diabète sucré et de ses complications sévères et parfois mortelles lorsque sa sécrétion est supprimée ou insuffisante et/ou lorsqu'il existe un défaut de son action.La cellule ß est une cellule excitable, c'est à dire capable de moduler son potentiel membranaire très rapidement en variant certaines conductances ioniques (Dean & Matthews 1968; 1970a; 1970b). En réponse à une élévation du glucose extracellulaire, la cellule ß se dépolarise et génère des potentiels d’action qui aboutissent à une augmentation du calcium cytoplasmique induisant la libération d’insuline par exocytose. La succession des différentes étapes menant à cette sécrétion régulée d'insuline est complexe, souvent désignée sous le vocable de couplage stimulus-sécrétion. Elle commence par une augmentation de l’entrée du glucose et de son métabolisme dans la cellule ß. L’augmentation de la concentration en ATP (ou du rapport de concentrations ATP/ADP) qui en résulte, entraîne la fermeture des canaux potassiques ATP-sensibles (KATP) avec une dépolarisation partielle de la membrane. Toutefois la fermeture de ces canaux ne semble pas suffisante pour expliquer la dépolarisation membranaire observée sous l’effet du glucose et une dépolarisation supplémentaire est nécessaire pour arriver au seuil d’activation des canaux calciques voltage-dépendants ou Cav (Gilon & Rorsman, 2009). Un efflux de Cl- de la cellule ß est déclenché lors d’une stimulation au glucose (Sehlin 1978; Sehlin 1987), proportionnellement à la concentration de glucose entre 5 et 20 mM (Malaisse et coll. 2004). Une diminution de la conc, Doctorat en Sciences biomédicales et pharmaceutiques (Médecine), info:eu-repo/semantics/nonPublished

Mutations of cysticfibrosis transmembrane conductance regulator (CFTR), an epithelial ligand-gated anion channel, are associated with the lethal genetic disease cystic fibrosis. The CFTR G551D mutation impairs ATP hydrolysis and thereby makes CFTR refractory to cAMP stimulation. Both wild-type (WT) and G551D CFTR have been implicated in regulatory volume decrease (RVD), but the underlying mechanism remains incompletely understood. Here, we show that the channel activity of both WT and G551D CFTR is directly stimulated by mechanical perturbation induced by cell swelling at the single-channel, cellular, and tissue levels. Hypotonicity activated CFTR single channels in cell-attached membrane patches and WT-CFTR-mediated short-circuit current (Isc) in Calu-3 cells, and this was independent of Ca2+ and cAMP/PKA signaling. Genetic suppression and ablation but not G551D mutation of CFTR suppressed the hypotonicity- and stretch-induced Isc in Calu-3 cells and mouse duodena. Moreover, ablation but not G551D mutation of the CFTR gene inhibited the RVD of crypts isolated from mouse intestine; more importantly, CFTR-specific blockers markedly suppressed RVD in both WT- and G551DCFTRmice, demonstrating for thefirst time that the channel activity of both WT and G551D CFTR is required for epithelial RVD. Our findings uncover a previously unrecognized mechanism underlying CFTR involvement in epithelial RVD and suggest that the mechanosensitivity of G551D CFTR might underlie the mild phenotypes resulting from this mutation.-Xie, C., Cao, X., Chen, X, Wang, D., Zhang, W. K., Sun, Y., Hu, W., Zhou, Z., Wang, Y., Huang, P. Mechanosensitivity of wild-type and G551D cystic fibrosis transmembrane conductance regulator (CFTR) controls regulatory volume decrease in simple epithelia. FASEB J. 30, 1579-1589 (2016). www.fasebj.org

Mutations of cysticfibrosis transmembrane conductance regulator (CFTR), an epithelial ligand-gated anion channel, are associated with the lethal genetic disease cystic fibrosis. The CFTR G551D mutation impairs ATP hydrolysis and thereby makes CFTR refractory to cAMP stimulation. Both wild-type (WT) and G551D CFTR have been implicated in regulatory volume decrease (RVD), but the underlying mechanism remains incompletely understood. Here, we show that the channel activity of both WT and G551D CFTR is directly stimulated by mechanical perturbation induced by cell swelling at the single-channel, cellular, and tissue levels. Hypotonicity activated CFTR single channels in cell-attached membrane patches and WT-CFTR-mediated short-circuit current (Isc) in Calu-3 cells, and this was independent of Ca2+ and cAMP/PKA signaling. Genetic suppression and ablation but not G551D mutation of CFTR suppressed the hypotonicity- and stretch-induced Isc in Calu-3 cells and mouse duodena. Moreover, ablation but not G551D mutation of the CFTR gene inhibited the RVD of crypts isolated from mouse intestine; more importantly, CFTR-specific blockers markedly suppressed RVD in both WT- and G551DCFTRmice, demonstrating for thefirst time that the channel activity of both WT and G551D CFTR is required for epithelial RVD. Our findings uncover a previously unrecognized mechanism underlying CFTR involvement in epithelial RVD and suggest that the mechanosensitivity of G551D CFTR might underlie the mild phenotypes resulting from this mutation.-Xie, C., Cao, X., Chen, X, Wang, D., Zhang, W. K., Sun, Y., Hu, W., Zhou, Z., Wang, Y., Huang, P. Mechanosensitivity of wild-type and G551D cystic fibrosis transmembrane conductance regulator (CFTR) controls regulatory volume decrease in simple epithelia. FASEB J. 30, 1579-1589 (2016). www.fasebj.org

Mutations of cysticfibrosis transmembrane conductance regulator (CFTR), an epithelial ligand-gated anion channel, are associated with the lethal genetic disease cystic fibrosis. The CFTR G551D mutation impairs ATP hydrolysis and thereby makes CFTR refractory to cAMP stimulation. Both wild-type (WT) and G551D CFTR have been implicated in regulatory volume decrease (RVD), but the underlying mechanism remains incompletely understood. Here, we show that the channel activity of both WT and G551D CFTR is directly stimulated by mechanical perturbation induced by cell swelling at the single-channel, cellular, and tissue levels. Hypotonicity activated CFTR single channels in cell-attached membrane patches and WT-CFTR-mediated short-circuit current (Isc) in Calu-3 cells, and this was independent of Ca2+ and cAMP/PKA signaling. Genetic suppression and ablation but not G551D mutation of CFTR suppressed the hypotonicity- and stretch-induced Isc in Calu-3 cells and mouse duodena. Moreover, ablation but not G551D mutation of the CFTR gene inhibited the RVD of crypts isolated from mouse intestine; more importantly, CFTR-specific blockers markedly suppressed RVD in both WT- and G551DCFTRmice, demonstrating for thefirst time that the channel activity of both WT and G551D CFTR is required for epithelial RVD. Our findings uncover a previously unrecognized mechanism underlying CFTR involvement in epithelial RVD and suggest that the mechanosensitivity of G551D CFTR might underlie the mild phenotypes resulting from this mutation.-Xie, C., Cao, X., Chen, X, Wang, D., Zhang, W. K., Sun, Y., Hu, W., Zhou, Z., Wang, Y., Huang, P. Mechanosensitivity of wild-type and G551D cystic fibrosis transmembrane conductance regulator (CFTR) controls regulatory volume decrease in simple epithelia. FASEB J. 30, 1579-1589 (2016). www.fasebj.org

SCOPUS: ar.j, info:eu-repo/semantics/published

SCOPUS: ar.j, info:eu-repo/semantics/published

This volume contains AFRRI Scientific Reports SR97-1 through SR97-10 for January-June 1997.

Resistance to anti-tumor drugs can be mediated by overexpression of the multidrug resistance 1 (MDR1) protein (P- glycoprotein). In three MDR1-transfected cell lines (Gill et al. Cell 71: 23-32, 1992; Altenberg et al. Cancer Res. 54: 618-622, 1994), a hypotonic stress-induced Cl- current has been demonstrated that can be inhibited by MDR1 substrates and Cl- channel blockers. We tested the hypothesis that MDR1 expression confers additional Cl- conductance by measuring regulatory volume decrease (RVD) in four pairs of isogenic cell lines and 36Cl efflux in two cell lines with and without hypotonic stress. The kinetics of RVD and response to Cl- channel blockers were indistinguishable in MDR and parental cells. Additionally, no significant difference was seen between 36Cl efflux rate constants under hypotonic conditions between NIH/3T3 and L1210 parental and MDR cells. We conclude that, in intact cells, the expression of MDR1 does not alter the rate of volume regulation or the rate of 36Cl efflux under hypotonic conditions between parental and MDR cells., Pub. in American Jnl. of Physiology, v270 pC1453-C1460, 1996