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Title

Regulation of insulin secretion by phosphatidylinositol-4,5-bisphosphate

Authors
Tomas, Alejandra
Pessin, J. E.
Published in Traffic. 2010, vol. 11, no. 1, p. 123-137
Abstract The role of PIP(2) in pancreatic beta cell function was examined here using the beta cell line MIN6B1. Blocking PIP(2) with PH-PLC-GFP or PIP5KIgamma RNAi did not impact on glucose-stimulated secretion although susceptibility to apoptosis was increased. Over-expression of PIP5KIgamma improved cell survival and inhibited secretion with accumulation of endocytic vacuoles containing F-actin, PIP(2), transferrin receptor, caveolin 1, Arf6 and the insulin granule membrane protein phogrin but not insulin. Expression of constitutively active Arf6 Q67L also resulted in vacuole formation and inhibition of secretion, which was reversed by PH-PLC-GFP co-expression. PIP(2) co-localized with gelsolin and F-actin, and gelsolin co-expression partially reversed the secretory defect of PIP5KIgamma-over-expressing cells. RhoA/ROCK inhibition increased actin depolymerization and secretion, which was prevented by over-expressing PIP5KIgamma, while blocking PIP(2) reduced constitutively active RhoA V14-induced F-actin polymerization. In conclusion, although PIP(2) plays a pro-survival role in MIN6B1 cells, excessive PIP(2) production because of PIP5KIgamma over-expression inhibits secretion because of both a defective Arf6/PIP5KIgamma-dependent endocytic recycling of secretory membrane and secretory membrane components such as phogrin and the RhoA/ROCK/PIP5KIgamma-dependent perturbation of F-actin cytoskeleton remodelling.
Keywords AnimalsApoptosis/drug effectsBlotting, WesternCell Culture TechniquesCell LineCell Survival/drug effectsElectrophoresis, Polyacrylamide GelEndocytosis/drug effectsGlucose/pharmacologyIn Situ Nick-End LabelingInsulin/ secretionInsulin-Secreting Cells/drug effects/enzymology/pathology/ secretionMiceMicroscopy, ConfocalMicroscopy, FluorescencePhosphatidylinositol 4,5-Diphosphate/antagonists & inhibitors/ physiologyPhosphotransferases (Alcohol Group Acceptor)/antagonists &Inhibitors/ biosynthesisProtein TransportVacuoles/drug effects/enzymology/metabolism
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PMID: 19845918
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TOMAS, Alejandra et al. Regulation of insulin secretion by phosphatidylinositol-4,5-bisphosphate. In: Traffic, 2010, vol. 11, n° 1, p. 123-137. https://archive-ouverte.unige.ch/unige:9057

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Deposited on : 2010-07-12

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