PROTEIN-KINASE-C PROMOTES ARACHIDONATE MOBILIZATION THROUGH ENHANCEMENT OF COA-INDEPENDENT TRANSACYLASE ACTIVITY IN PLATELETS

A role for protein kinase C in arachidonate mobilization was demonstrated. Treatment of rat platelets with phorbol myristate acetate (PMA) or the diacylglycerol 1-oleoyl-2-acetylglycerol increased the transfer rate of arachidonate (AA) from phosphatidylcholine to phosphatidylethanolamine and stimulated AA release. The transfer dose-dependently induced by PMA was inhibited by staurosporine. Ether phospholipids were the acceptors of AA in these stimulated transfer reactions. Membrane-bound protein kinase C activity was enhanced by PMA, and this increase was inhibited by staurosporine. AA transfer between phospholipids is due to the action of polyunsaturated-fatty-acid-specific transacylases. For this purpose, transacylase activities were assayed in cell-free systems from PMA-treated platelets. We observed that the CoA-independent transacylase activity was modulated in parallel to AA transfer as a function of PMA concentration. Taken together, the data show that protein kinase C activation might promote the mobilization of AA in platelets through the enhancement of CoA-independent transacylase activity.