Cellular and subcellular expression of Golf/Gs and Gq/G11 α-subunits in rat pancreatic endocrine cells

We studied the cellular and subcellular localization of G alpha-subunits in pancreas by immunocytochemistry. Golf alpha and G11 alpha were specifically localized in islet insulin B-cells and glucagon A-cells, respectively. Gs alpha and Gq alpha labeling was more abundant in B-cells. The presence of Golfer in B-cells was confirmed by in situ hybridization. In B-cells, Golf alpha and Gs alpha were found in the Golgi apparatus, plasma membrane (PM) and, remarkably, in mature and immature insulin secretory granules, mainly at the periphery of the insulin grains. Gq alpha was detected on the rough endoplasmic reticulum (RER) near the Golgi apparatus. In A-cells, the G alpha-subunits were mostly within the glucagon granules: G11 alpha gave the strongest signal, Gs alpha less strong, Gq was scarce, and Golf was practically absent. Gq alpha and Gs alpha immunoreactivity was detected in acinar cells, although it was much weaker than that in islet cells. The cell-dependent distribution of the G alpha-subunits indicates that the stimulatory pathways for pancreatic function differ in acinar and in islet B- and A-cells. Furthermore, the G-protein subunits in islet cell secretory granules might be functional and microscopy participate in granule trafficking and hormone secretion.