Stimulatory transducing systems in pancreatic islet cells

We have determined the cellular distribution of different alpha subtypes of G proteins and adenylyl cyclase (AC) isoforms in endocrine, exocrine, and established pancreatic cell lines. VIP, PACAP, and tGLP-1 receptor proteins are expressed to varying extents in A and B cells, whereas the expression of G alpha subunits is cell specific. Thus, G(olf) alpha is detected in normal rodent B cells and immortalized pancreatic B cell lines, whereas Gs alpha is more ubiquitously expressed. The cellular density of AC isoforms labeling (I, II, III, IV, V/VI) is also islet cell-specific and their distribution is age- and species-dependent. The identification of numerous signaling molecule subtypes, together with the discovery of their specific subcellular distribution, will help the functional characterization of their intraregulatory pathways, leading to the extrusion of insulin or glucagon secretory granules, and those leading to differentiation and apoptosis of islet cells.