Anoctamin 1 (Ano1) is required for glucose-induced membrane potential oscillations and insulin secretion by murine [beta]-cells

Anions such as Cl^sup -^ and HCO3 ^sup -^ are well known to play an important role in glucose-stimulated insulin secretion (GSIS). In this study, we demonstrate that glucose-induced Cl^sup -^ efflux from [beta]-cells is mediated by the Ca^sup 2+^-activated Cl^sup -^ channel anoctamin 1 (Ano1). Ano1 expression in rat [beta]-cells is demonstrated by reverse transcriptase-polymerase chain reaction, western blotting, and immunohistochemistry. Typical Ano1 currents are observed in whole-cell and inside-out patches in the presence of intracellular Ca^sup ++^: at 1 [mu]M, the Cl^sup -^ current is outwardly rectifying, and at 2 [mu]M, it becomes almost linear. The relative permeabilities of monovalent anions are NO3 ^sup -^ (1.83±0.10) > Br^sup -^ (1.42±0.07) > Cl^sup -^ (1.0). A linear single-channel current-voltage relationship shows a conductance of 8.37 pS. These currents are nearly abolished by blocking Ano1 antibodies or by the inhibitors 2-(5-ethyl-4-hydroxy-6-methylpyrimidin-2-ylthio)-N-(4-(4-methoxyphenyl)thiazol-2-yl)acetamide (T-AO1) and tannic acid (TA). These inhibitors induce a strong decrease of 16.7-mM glucose-stimulated action potential rate (at least 87 % on dispersed cells) and a partial membrane repolarization with T-AO1. They abolish or strongly inhibit the GSIS increment at 8.3 mM and at 16.7 mM glucose. Blocking Ano1 antibodies also abolish the 16.7-mM GSIS increment. Combined treatment with bumetanide and acetazolamide in low Cl^sup -^ and HCO3 ^sup -^ media provokes a 65 % reduction in action potential (AP) amplitude and a 15-mV AP peak repolarization. Although the mechanism triggering Ano1 opening remains to be established, the present data demonstrate that Ano1 is required to sustain glucose-stimulated membrane potential oscillations and insulin secretion.