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 linoleic and linolenic acids, which are the products of the hydrolysis of phosphatidylcholine catalyzed by phospholipase A2 (EC 3.1.1.4), significantly potentiate the differentiation of HL-60 cells to macrophages that is induced by either a membrane-permeant diacylglycerol or a phorbol ester. The cell differentiation was assayed by measuring the expression of CD11b, one of the cell surface markers of macrophages, and also by the appearance of phagocytic activity. Snake venom phospholipase A2 added directly to the cells is also active for this potentiation. Neither lysophosphatidylcholine, fatty acid, nor phospholipase A2 is active unless a membrane-permeant diacylglycerol or a phorbol ester is present. The results presented provide further evidence that activation of phospholipase A2 may be intimately related to the signal transduction pathway through protein kinase C.