Regulation of Cyr61 gene expression by mechanical stretch through multiple signaling pathways

Department of Histology, University of Pennsylvania, Philadelphia, Pennsylvania 19104 The cysteine-rich protein 61 (Cyr61) is a signaling molecule with functions in cell migration, adhesion, and proliferation. This protein is encoded by an immediate early gene whose expression is mainly induced by serum growth factors. Here we show that Cyr61 mRNA levels increase sharply in response to cyclic mechanical stretch applied to cultured bladder smooth muscle cells. Stretch-induced changes of Cyr61 transcripts were transient and accompanied by an increase of the encoded protein that localized mainly to the cytoplasm and nucleus of the cells. With the use of pharmacological agents that interfere with known signaling pathways, we show that transduction mechanisms involving protein kinase C and phosphatidylinositol 3-kinase activation partly blocked stretch-induced Cyr61 gene expression. Selective inhibition of Rho kinase pathways altered this stretch effect as well. Meanwhile, using inhibitors of the actin cytoskeleton, we show that Cyr61 gene expression is sensitive to mechanisms that sense actin dynamics. These results establish the regulation of Cyr61 gene by mechanical stretch and provide clues to the key signaling molecules involved in this process. smooth muscle cells; signal transduction