Localization of beta II subspecies of protein kinase C in beta-cells

Protein kinase C (PKC) has been generally accepted to play a key role in stimulus-response coupling in various secretory cells, including pancreatic islets and pancreatic acini. The enzyme exists as a large family of multiple subspecies with highly related structures (alpha-, beta I-, beta II-, gamma-, delta-, epsilon-, and zeta-PKC). With an immunocytochemical procedure with subspecies-specific antibodies, beta II-PKC-like immunoreactivity was identified to localize in the beta-cells of the rat pancreatic islets. Neither beta I- nor gamma-PKC-like immunoreactivity was found in both islets and acini. Biochemical analysis confirmed that the rat whole pancreatic tissues contain a significant amount of alpha-PKC and a minute amount of beta II-PKC but neither beta I- nor gamma-PKC. On the other hand, beta II-PKC-like immunoreactivity was not detected in rat insulinoma cells, in which insulin secretion was induced in response to 12-O-tetradecanoylphorbol-13-acetate and carbachol but not in response to glucose. These findings suggest that beta II-PKC is the major, if not the sole, subspecies of PKC in beta-cells of rat pancreatic islets and a possible candidate for involvement in glucose-induced insulin secretion.