Activation of adenylyl cyclases, regulation of insulin status, and cell survival by Gαolf in pancreatic β-cells

Abstract

Because we recently identified the Gαolf subunit in rat pancreatic β-cells, we investigated the downstream effectors and the biological functions of this G protein in HEK-293T cells and the insulin-secreting mouse βTC-3 cell line. With the use of transient transfection of HEK-293T cells with constitutively activated Gαolf (GαolfQ214L, i.e., AGαolf), together with expression vectors encoding the adenylyl cyclase (AC) isoforms (AC-I to -VIII and soluble AC), compared with cotransfections using AGαs (GαsR201C), we observed that AGαolf preferentially activates AC-I and -VIII, which are also expressed in β-cells. Stable overexpression of wild-type or AGαolf in βTC-3 cells resulted in partial attenuation of insulin secretion and biosynthesis, suggesting that chronic activation of the Gαolf-signaling pathway is associated with β-cell desensitization. In agreement, transfected βTC-3 cells present a decreased insulin content with respect to parental cells, whereas the proinsulin convertases PC-1 and PC-2 were unaffected. Furthermore, βTC-3-AGαolf cells are resistant to serum starvation-induced apoptosis. Our findings suggest that Gαolf is involved in insulin status, cell survival, and regeneration of the insulin-secreting β-cells during development and diabetes.