SSeCKS gene expression in vascular smooth muscle cells: Regulation by angiotensin II and a potential role in the regulation of PAI-1 gene expression

Rat aortic smooth muscle cells (RASM) express the src suppressed C-kinase s ubstrate (SSeCKS), which is thought to be an integral regulatory component of cytoskeletal dynamics and G-protein coupled-receptor signaling modules. The specific sub-classes of growth factor receptors that regulate the genom ic changes in SSeCKS expression in smooth muscle cells have not been charac terized. In this study we identify SSeCKS as an angiotensin type 1 (AT(1)) receptor-dependent target gene in RASM cells treated with angiotensin II (A ng II). SSeCKS mRNA levels increase up to three-fold relative to the contro l within 3.5 h of Ang II treatment and are followed by a slight decrease of mRNA relative to the control levels after 24 h of stimulation. SSeCKS gene expression and plasminogen activator inhibitor-1 (PAI-1) gene expression c orrelate in RASM cells treated with Ang II, By co-transfecting plasmids bea ring recombinant-SSeCKS and a PAI-1-promoter/luciferase reporter into Cos-l cells, we show that alternative forms of recombinant-SSeCKS protein differ entially influence PAI-I promoter activity. These data indicate a biochemic al linkage between SSeCKS activity and one or more of the cytoplasmic signa ling pathways that are involved in the control of PAI-1 promoter activity. Finally, we show that the alternative forms of recombinant-SSeCKS protein d ifferentially influence cell-spreading when ectopically expressed in ms-tra nsformed rat kidney (KNRK) fibroblasts. Taken together, our data suggest th at SSeCKS interacts with intracellular signaling pathways that control cyto skeletal remodeling and extracellular matrix remodeling following Ang II st imulation of the RASM cell. (C) 2000 Academic Press.