Journal
BIOCHEMICAL JOURNAL
Volume 432, Issue -, Pages 375-386Publisher
PORTLAND PRESS LTD
DOI: 10.1042/BJ20100864
Keywords
calcium influx; exocytosis; insulin; pancreatic beta-cell; total internal reflection fluorescent (TIRF) microscopy; transient receptor potential V2 (TrpV2) channel
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Funding
- KAKENHI [C-20570189, 21113523, B-20390260]
- Sumitomo Foundation
- Astellas Foundation for Research on Metabolic Disorders
- Research Foundation for Opto-Science and Technology
- Kyorin University School of Medicince
- Novartis Foundation (Japan) for the Promotion of Science
- Grants-in-Aid for Scientific Research [21113523] Funding Source: KAKEN
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Functional insulin receptor and its downstream effector PI3K (phosphoinositide 3-kinase) have been identified in pancreatic beta-cells, but their involvement in the regulation of insulin secretion from beta-cells remains unclear. In the present study, we investigated the physiological role of insulin and PI3K in glucose-induced biphasic insulin exocytosis in primary cultured beta-cells and insulinoma Min6 cells using total internal reflection fluorescent microscopy. The pretreatment of beta-cells with insulin induced the rapid increase in intracellular Ca2+ levels and accelerated the exocytotic response without affecting the second-phase insulin secretion. The inhibition of PI3K not only abolished the insulin-induced rapid development of the exocytotic response, but also potentiated the second-phase insulin secretion. The rapid development of Ca2+ and accelerated exocytotic response induced by insulin were accompanied by the translocation of the Ca2+-permeable channel TrpV2 (transient receptor potential V2) in a PI3K-dependent manner. Inhibition of TrpV2 by the selective blocker tranilast, or the expression of shRNA (short-hairpin RNA) against TrpV2 suppressed the effect of insulin in the first phase, but the second phase was not affected. Thus our results demonstrate that insulin treatment induced the acceleration of the exocytotic response during the glucose-induced first-phase response by the insertion of TrpV2 into the plasma membrane in a PI3K-dependent manner.
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