Regulation of human involucrin promoter activity by novel protein kinase Cisoforms

Human involucrin (hINV) mRNA level and promoter activity increase when kera tinocytes are treated with the differentiating agent, 12-O-tetradecanoylpho rbol-13-acetate (TPA). This response is mediated via a p38 mitogen-activate d protein kinase-dependent pathway that targets activator protein 1 (Efimov a, T., LaCelle, P. T., Welter, J. F., and Eckert, R. L. (1998) J. Biol, Che m. 273, 24387-24395), In the present study we examine the role of various P KC isoforms in this regulation. Transfection of expression plasmids encodin g the novel PKC isoforms delta, epsilon, and eta increase hINV promoter act ivity. In contrast, neither conventional PKC isoforms (alpha, beta, and gam ma) nor the atypical isoform (zeta) regulate promoter activity. Consistent with these observations, promoter activity is inhibited by the PKC delta-se lective inhibitor, rottlerin, but not by Go-6976, an inhibitor of conventio nal PRC isoforms, and novel PKC isoform-dependent promoter activation is in hibited by dominant-negative PKC delta. This regulation appears to be physi ologically important, as transfection of keratinocytes with PKC delta, -eps ilon, or -eta increases expression of the endogenous hINV gene. Synergistic promoter activation (greater than or equal to 100-fold) is observed when P KC epsilon- or -eta-transfected cells are treated with TPA. In contrast, th e PKC delta-dependent response is more complex as either activation or inhi bition is observed, depending upon PKC delta concentration.