The Cysteine‐Rich Protein 61 Mediates Mechanical Stretch‐Induced Gene Expression in Smooth Muscle Cells

Abstract

Externally applied cyclic stretch to cultured bladder smooth muscle (SM) cells results in the transient expression of the Cyr61 gene that encodes a cysteine-rich extracelluar matrix-associated heparin-binding protein originally described as a proangiogenic factor capable of altering the gene programs for angiogenesis, adhesion and extracellular matrix synthesis. In this study, we investigated the effects of mechanical stretch-induced Cyr61 on the expression of potential mechano-sensitive Cyr61 target genes and the signaling pathways involved. We showed that suppression of Cyr61 expression with an adenoviral vector encoding an anti-sense oligonucleotide reduced mechanical strain-induced vascular endothelial growth factor (VEGF), alpha v integrin and SM alpha-actin gene expression but had no effect on myosin heavy chain (MHC) isoforms, SM-1 and SM-2. Signaling pathways involving RhoA GTPase, phosphatidyl inositol 3-kinase and cytoskeletal actin dynamics altered stretch-induced Cyr61 and Cyr61 target genes. Reciprocally, adenovirus-mediated overexpression of Cyr61 in cells cultured under static conditions increased the expression of VEGF, alpha v integrin and SM alpha-actin, as well as that of SM-1 and SM-2 isoforms suggesting that the effects of a sustained expression of Cyr61 extend to SM specific contractile function. These effects were dependent on the integrity of the actin cytoskeleton. Together, these results indicate that Cyr61 is an important determinant of the genetic reprogramming that occurs in mechanically challenged cells. Supported by NIH Grant R01 DK-060572.