UP-REGULATION OF TISSUE INHIBITOR OF METALLOPROTEINASES-3 GENE-EXPRESSION BY TGF-BETA IN ARTICULAR CHONDROCYTES IS MEDIATED BY SERINE THREONINE AND TYROSINE KINASES/

The balance between matrix metalloproteinases (MMPs) and tissue inhibi tors of metalloproteinases (TIMPs) regulates extracellular matrix turn -over in normal animal development, cancer cell metastasis, atheroscle rotic plaque rupture and erosion of arthritic cartilage. Transforming growth factor beta (TGF-beta), an inducer of matrix synthesis, potentl y enhances mRNA and protein of a recently characterized MMP inhibitor, TIMP-3, in bovine articular chondrocytes. We examined the implication of protein kinases in the TGF-beta-mediated induction of TIMP-3 expre ssion by utilizing activators and inhibitors of these enzymes. Protein kinase A activators, dibutyryl cyclic AMP, or forskolin had little or no effect, respectively, while phorbol 12-myristate 13-acetate (PMA), a PKC activator, increased TIMP-3 gene expression. H7, a serine/threo nine protein kinase inhibitor, markedly reduced the response of TIMP-3 gene to TGF-beta. Furthermore, two protein tyrosine kinase inhibitors , genistein and herbimycin A, inhibited TGF-beta induction of TIMP-3. H7 and genistein also suppressed TGF-beta-induced TIMP-3 protein expre ssion. These results suggest that TGF-beta signaling for TIMP-3 gene i nduction involves H7-sensitive serine/threonine kinase as well as herb imycin A- and genisrein-sensitive protein tyrosine kinases. J. Cell. B iochem. 70:517-527, 1998. (C) 1998 Wiley-Liss, Inc.