Redistribution of phospholipid/calcium-dependent protein kinase and altered phosphorylation of its soluble and particulate substrate proteins in phorbol ester-treated rat pancreatic acini

Abstract

The biological activity of phorbol esters, such as 12-O-tetra-decanoylphorbol-13-acetate, have been associated with activation of phospholipid/Ca2+-dependent protein kinase. Treatment of rat pancreatic acini with 12-O-tetradecanoylphorbol-13-acetate (10(-6) M) resulted in a sustained translocation of phospholipid/Ca2+-dependent protein kinase activity to the membrane site. The pattern of phosphorylation of at least two substrate proteins (Mr 22,000 and 18,000) for this Ca2+-dependent protein kinase was also altered following exposure to phorbol ester, these phosphoproteins disappearing from the soluble fraction and appearing in the particulate. Concurrently, 12-O-tetradecanoylphorbol-13-acetate stimulated amylase release from intact acini in a time- and dose-dependent fashion. These results suggest a potential role for phospholipid/Ca2+-activated protein kinase in the regulation of pancreatic exocrine function.