NET1/ARHGEF8 is a mechanosensitive Guanine Exchange Factor controlling vascular smooth muscle cells' contractility

Cyclic stretch, generated by pulsatile blood pressure, has been identified as a pivotal regulator of vascular smooth muscle cell (VSMC) behavior and arterial wall homeostasis. Research has demonstrated that RhoA activation is a fundamental component of VSMC responses to mechanical stress through its action on cytoskeletal remodeling. However, the upstream mechanosensitive regulators of RhoA activation remain insufficiently defined. In this study, we identify the guanine nucleotide exchange factor (RhoGEF) NET1/ARHGEF8 as a stretch-responsive protein. NET1 appears to be highly expressed in arteries and VSMCs. Under physiological levels of cyclic stretch, NET1 localizes to the cytosol and interacts with RhoA. In contractile cells, loss of NET1 blunted stretch-induced MYPT1 phosphorylation and impaired cell adhesion and spreading, without exerting any effect on cell proliferation. As we demonstrated, NET1s contribution to the stretch-induced response of VSMC was due to its localization in the cytosol. The expression of a cytosolic NET1 mutant promoted contractile gene expression and increased cell contractile capacity. Collectively, these findings identify NET1 as a stretch-sensitive RhoGEF in VSMCs that contributes to their adhesion and contractile behavior.