Mediation of pepsinogen secretion from guinea pig chief cells by Ca2+/calmodulin-dependent protein kinase II

In the presence of Ca2+ bound to calmodulin, Ca2+/calmodulin-dependent protein kinase II (CaMK II) exhibits an intramolecular autophosphorylation and modulates many cell functions. In this study, the role of CaMK II in pepsinogen secretion was investigated in cultured guinea pig chief cells by using a specific CaMK II inhibitor, 1-[N,O-Bis(5-isoquinolinesulfonyl)-N-methyl-l-tyrosyl]-4-phenyl-piperazine (KN-62), and an antibody for the Thr-286-autophosphorylated α subunit of CaMK II which specifically recognized the autophosphorylated form of CaMK II. KN-62 inhibited the pepsinogen secretion stimulated by carbamylcholine chloride, cholecystokinin octapeptide, and ionomycin in a dose-dependent manner without affecting intracellular Ca 2+ concentrations, but had no effect on the secretion by 12-O-tetradecanoyl phorbol-13-acetate (TPA) and forskolin. Heavy staining with the antibody for autophosphorylated CaMK II was observed in the cytoplasm of chief cells treated with carbamylcholine chloride or ionomycin, but only light staining was seen in cells treated with TPA or forskolin. Thus, CaMK II and its autophosphorylation may be a critical step in the intracellular pathway by which Ca2+ causes pepsinogen secretion from guinea pig chief cells.