IDENTIFICATION OF PROTEIN-KINASE C-ZETA ISOZYME IN HAMSTER PANCREAS AND PANCREATIC-CARCINOMA CELL-LINES

Cellular differentiation and proliferation are dependent upon phosphor ylation by endogenous protein kinase C (PKC) isozymes in many cell typ es. Western blotting with a C-terminally directed rabbit polyclonal an ti-PKC zeta antibody detected a doublet of approximately 81 kDa in nor mal hamster pancreatic tissue and hamster pancreatic carcinoma (PC-1) and human pancreatic carcinoma (PANC-1) cells. Preabsorption of the an tibody with the specific peptide blocked the appearance of the 81-kDa band, indicating that the band was specifically recognized by the PKC zeta antibody. In contrast, antibodies for PKC alpha, beta, gamma, del ta, and epsilon failed to show specific immunoreactivity for normal pa ncreatic tissue or PANC-1 or PC-1 cells. Immunocytochemical analysis i dentified PKC zeta in the cytoplasm of ductules and large ducts, to a lesser extent in the islets of the hamster pancreas, and in the normal cultured pancreatic duct epithelial cells and pancreatic carcinoma (P ANC-1 and PC-1) cell lines. Specific reactivity was seen by electron m icroscopy in the ductal cells of the normal pancreatic tissue. In norm al pancreatic ductal tissue and primary pancreatic ductal hyperplasia and carcinoma, the proportional labeling of PKC zeta in nuclei and cyt oplasm was similar. Our results demonstrating the presence of PKC zeta isozyme in the normal pancreas, cultured normal pancreatic duct epith elial cells, and pancreatic carcinoma cells or carcinoma tissue sugges ts a role for this isozyme in the normal physiology of the pancreas an d perhaps in pancreatic carcinoma. (C) 1995 Wiley-Liss, Inc.