Activation of protein kinase C inhibits the expression of connective tissue growth factor

Connective tissue growth factor (CTGF) is a member of a protein family in w hich 38 cysteine residues are conserved. Although a wide variety of importa nt biological functions have been ascribed to these proteins in recent year s, the regulation of their gene expression for most members is virtually un known, We studied the effects of protein kinase C (PKC) and tyrosine kinase on the expression of CTGF and observed that at the mRNA level CTGF express ion is inhibited by the activation of PKC, but stimulated by the inhibition of PKC and tyrosine kinase. We further determined that the novel and the c lassical PKC isoforms are needed for the inhibition, but the atypical isofo rms are not involved. Our data suggest that phosphorylation on serine/threo nine and tyrosine by PKC and by tyrosine kinase are all inhibitory to the e xpression of CTGF. (C) 2000 Academic Press.