Protein kinase C-mediated regulation of the expression of CD14 and CD11/CD18 in U937 cells.

We used the U937 cell line to analyze CD14, CD11/CD18, HLA class-I and DR antigen expression during PMA-induced differentiation. Treatment of U937 cells with PMA markedly increased CD14, CD11a, CD11b and CD18 antigen expression, and slightly increased CD11c expression. Protein kinase C may play a major role in regulating the expression of these antigens. The protein kinase inhibitor H7 abrogated the inductive effect of PMA. Calcium ionophore, when added alone or in the presence of PMA, had no effect. The inhibitory effect of the calcium antagonist verapamil, EGTA, and of chlorpromazine, an antagonist of calcium-binding proteins, supports a role for calcium-dependent protein kinase C in the up-regulation of CD14 and CD11/CD18 surface expression. The specific calmodulin inhibitors R24571 and W7 had no effect on antigen expression. Our findings suggest that protein kinase C activation is an important step in the PMA-induced differentiation of U937 cells.