Rho-guanine nucleotide exchange factors involved in cyclic stretch-induced reorientation of vascular endothelial cells

Abstract

Cyclic stretch is an artificial model of mechanical force loading, which induces the reorientation of vascular endothelial cells (ECs) and their stress fibers in a direction perpendicular to the stretch axis. Rho family GTPases are crucial for cyclic stretch-induced EC reorientation; however, the mechanism underlying stretch-induced activation of Rho family GTPases is unknown. A screen of short-hairpin RNAs targeting 63 Rho-guanine nucleotide exchange factors (Rho-GEFs) revealed that at least 11 Rho-GEFs (Abr, Alsin, ARHGEF10, Bcr, GEF-H1, LARG, p190RhoGEF, PLEKHG1, P-REX2, Solo/ARHGEF40, and α-PIX), which specifically or broadly target RhoA, Rac1 and/or Cdc42, are involved in cyclic stretch-induced perpendicular reorientation of ECs. Overexpression of Solo induced RhoA activation and F-actin accumulation at cell-cell and cell-substrate adhesion sites. Knockdown of Solo suppressed cyclic stretch- or tensile force-induced RhoA activation. Moreover, knockdown of Solo significantly reduced cyclic stretch-induced perpendicular reorientation of ECs when cells were cultured at high density, but not when they were cultured at low density or pretreated with EGTA or VE-cadherin-targeting siRNAs. These results suggest that Solo is involved in cell-cell adhesion-mediated mechanical signal transduction during cyclic stretch-induced EC reorientation.