Cellular and Subcellular Expression of Golf/Gs and Gq/G11 α-Subunits in Rat Pancreatic Endocrine Cells

Abstract

SUMMARYWe studied the cellular and subcellular localization of G ␣-subunits in pancreas by immunocytochemistry. Golf ␣ and G11 ␣ were specifically localized in islet insulin B-cells and glucagon A-cells, respectively. Gs ␣ and Gq ␣ labeling was more abundant in B-cells. The presence of Golf ␣ in B-cells was confirmed by in situ hybridization. In B-cells, Golf ␣ and Gs ␣ 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 ␣ was detected on the rough endoplasmic reticulum (RER) near the Golgi apparatus. In A-cells, the G ␣-subunits were mostly within the glucagon granules: G11 ␣ gave the strongest signal, Gs ␣ less strong, Gq was scarce, and Golf was practically absent. Gq ␣ and Gs ␣ immunoreactivity was detected in acinar cells, although it was much weaker than that in islet cells. The cell-dependent distribution of the G ␣-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 participate in granule trafficking and hormone secretion.

Ghrelin Uses Gαi2 and Activates Voltage-Dependent K+ Channels to Attenuate Glucose-Induced Ca2+ Signaling and Insulin Release in Islet β-Cells

“…The mediation by the Gprotein G␣ i2 -subtype is surprising in light of the current concept that GHS-R signaling is mediated primarily by the G 11 subtype (2). However, our result is consistent with the reports that G␣ i2 is expressed in ␤-cells (29,31), whereas G␣ 11 is expressed primarily in non-␤-cells in islets (32)(33)(34).…”

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

“…We also investigated the possible role of G␣olf on insulin status, using the mouse secreting ␤TC-3 cell line in culture, because we found that G␣olf was present in insulin secretory granules of pancreatic ␤-cells (2). Several studies by others and us (17,21,28) demonstrated that all of the membrane-bound ACI-VIII isoforms are present in ␤-cells.…”

“…Recently, we identified G␣olf in pancreatic ␤-cells by in situ hybridization, immunocytochemistry, and electron microscopy (2). In Langerhans islets, G␣olf is located inside the insulin-secretory granules and ␤-cell plasma membrane, suggesting that it is involved in granule migration, processing, and exocytosis.…”

Tumeurs juvéniles de la granulosa : expression clinique et moléculaire

“…Dans l'espèce humaine, les tumeur de la granulosa synthétisent et secrètent de l'inhibine. Matzuk a donc proposé une résistance a cette hormone au sein de la tumeur [107]. La protéine p120, suspectée d'être un élément important dans la transduction du signal de l'inhibine, est sous-exprimée ou absente des les TJG par rapport aux tumeurs épithéliales et à l'ovaire normal [62].…”