POTENTIAL ROLE OF PHOSPHOLIPASE-A2 IN HL-60 CELL-DIFFERENTIATION TO MACROPHAGES INDUCED BY PROTEIN-KINASE-C ACTIVATION

2-Lysophosphatidylcholine and cis-unsaturated fatty acids such as lino leic and linolenic acids, which are the products of the hydrolysis of phosphatidylcholine catalyzed by phospholipase A2 (EC 3.1.1.4), signif icantly potentiate the differentiation of HL-60 cells to macrophages t hat is induced by either a membrane-permeant diacylglycerol or a phorb ol ester. The cell differentiation was assayed by measuring the expres sion of CD11b, one of the cell surface markers of macrophages, and als o by the appearance of phagocytic activity. Snake venom phospholipase A2 added directly to the cells is also active for this potentiation. N either lysophosphatidylcholine, fatty acid, nor phospholipase A2 is ac tive unless a membrane-permeant diacylglycerol or a phorbol ester is p resent. The results presented provide further evidence that activation of phospholipase A2 may be intimately related to the signal transduct ion pathway through protein kinase C.