Extracellular Calcium influx activates Adenylate Cyclase 1 and potentiates Insulin secretion in MIN6 cells

In this study, we investigated the interplay between intracellular cAMP and Ca2+ concentrations ([cAMP]i and [Ca2+]i, respectively) in the pancreatic β cell line MIN6 cells using total internal reflection fluorescence microscopy. For measuring [cAMP]i, we developed a genetically encoded yellow fluorescent biosensor for cAMP (fluorescent cAMP indicator; Flamindo), which changes fluorescence intensity with cAMP binding. Application of high-KCl or glucose to MIN6 cells induced the elevation of [cAMP]i and exocytosis. Furthermore, application of an L-type Ca2+ channel agonist or ionomycin to induce extracellular Ca2+ influx evoked the elevation of [cAMP]i, whereas application of carbachol or thapsigargin, which mobilize Ca2+ from internal stores, did not evoke the elevation of [cAMP]i. We performed RT-PCR analysis and found that Ca2+-sensitive adenylate cyclase 1 (Adcy1) was expressed in MIN6 cells. Knockdown of endogenous Adcy1 by small interference RNA significantly suppressed glucose-induced exocytosis and the elevation of both [cAMP]i and [Ca2+]i. Taken together, these findings demonstrate that Adcy1 plays an important role in the control of pancreatic β cell cAMP homeostasis and insulin secretion.

Source: BJ Cell - January 3, 2013 Category: Biochemistry Authors: T Kitaguchi, M Oya, Y Wada, T Tsuboi, A Miyawaki Tags: BJ Cell Source Type: research