Protein kinase C isotypes required for phorbol-ester induction of stromelysin-1 in rat fibroblasts

The phorbol-ester tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA) is a potent inducer of the metalloproteinase stromelysin in fibroblasts in vivo and in several cultured cell lines. Rat-1 and Rat-2 fibroblasts, however, do not respond to TPA stimulation by induction of stromelysin gene activity, although collagenase promoter-mediated activity is induced threefold by TPA treatment in these cells. We determined that rat fibroblasts expressed protein kinase C(PKC)alpha, PKCdelta, PKCepsilon, and PKCzeta but neither the mRNA nor the protein for PKCbeta. When Rat-2 fibroblasts were stably transfected with an expression vector producing PKCbeta, however, TPA treatment of these variants resulted in a 3.1-fold induction of stromelysin promoter-mediated luciferase activity compared with a 1.3-fold induction in parental Rat-2 cells (P<0.002). Transient transfection of PKCepsilon produced a small but significant increase in TPA-stimulation of both stromelysin- and collagenase-mediated gene expression. These results suggest that there are PKC isotype-specific signaling pathways that can differentially regulate matrix metalloproteinase gene expression.