The role of cytosolic Ca2+, protein kinase C, and protein kinase A in hormonal stimulation of phospholipase D in rat hepatocytes.

摘要: Ca(2+)-dependent and protein kinase C-dependent mechanisms of phospholipase D (PLD) activation were studied in rat hepatocytes by measuring phosphatidylethanol (Peth) formation the presence ethanol. Stimulation Peth 12-O-tetradecanoyl-phorbol 13-acetate (TPA), vasopressin, or A23187 was inhibited multiple C inhibitors down-regulation, indicating that this enzyme is involved action all these agents. A controlled elevation cytosolic Ca2+ concentration ([Ca2+]cyt) over range 0.1-2.0 microM activated absence other agonists. Staurosporin potentiated Ca(2+)-induced shifting [Ca2+]cyt dose-response curve to left. Other (calphostin C, bisindolylmaleimide) Ca(2+)-mediated formation, but inhibition reduced staurosporin-treated cells. Okadaic acid PLD TPA, suppressed elevated [Ca2+]cyt. Desensitization TPA-induced activity did not affect Ca2+. These data indicate control distinct pathways activation, pathway a staurosporin-sensitive kinase. Both contribute vasopressin-induced intact hepatocytes. Activation enhanced TPA-stimulated Ca(2+)-stimulated stimulated formation. Protein acted enhancing hormonal mobilization, rather than directly activating PLD, thereby shifted balance