PDGF induction of alpha(2) integrin gene expression is mediated by protein kinase C-zeta

Platelet-derived growth factor (PDGF) stimulates fibroblasts to move over collagen and contract three-dimensional collagen gels, processes important in wound repair and fibrocontractive diseases, These processes depend on alpha(2) beta(1) integrin ligation of collagen and PDGF induces the expression of this integrin, Several lines of evidence presented here suggest that PKC-zeta plays a role in alpha(2) integrin gene expression. The induction was blocked by chemical inhibitors for protein tyrosine kinases (PTK), genistein, and protein kinase C (PKC), chelerythrine, and bisindolylmaleimide GF 109203X, Cells depleted of phorbol 12-myristate 13-acetate (PMA)-inducible PKCs by chronic treatment with PMA still demonstrated an alpha(2) response to PDGF indicating that a non-PMA-sensitive PKC isoform was required, PDGF induced kinase activity in PKC-zeta immunoprecipitates. Antisense oligonucleotides complementary to 5' end of PKC-zeta mRNA sequences blocked the PDGF-induced increase of alpha(2) mRNA levels up to 70%, indicating PKC-zeta, a non-PMA-sensitive PKC isoform, is a component of the PDGF stimulatory pathway for alpha(2) mRNA synthesis. A 961-base pair (bp) upstream region of alpha(2) gene/CAT construct transfected into human dermal fibroblasts was positively regulated by PDGF as judged by CAT enzymatic levels, Both PTK and PKC inhibitors blocked PDGF-stimulation of the alpha(2) promoter fragment/CAT construct, indicating that the phosphorylation requirement occurred at alpha(2) promoter-directed transcription level. Therefore, we propose that PDGF-stimulatory pathway of alpha(2) integrin gene expression involves multiple cellular protein kinases, one of which is PKC-zeta.