The cell adhesion molecule IGPR-1 is activated by and regulates responses of endothelial cells to shear stress

Vascular endothelial cells respond to blood flow-induced shear stress. However, the mechanisms through which endothelial cells transduce mechanical signals to cellular responses remain poorly understood. In this report, using tensile-force assays, immunofluorescence and atomic force microscopy, we demonstrate that immunoglobulin and proline-rich receptor-1 (IGPR-1) responds to mechanical stimulation and increases the stiffness of endothelial cells. We observed that IGPR-1 is activated by shear stress and tensile force and that flow shear stress-mediated IGPR-1 activation modulates remodeling of endothelial cells. We found that under static conditions, IGPR-1 is present at the cell-cell contacts; however, under shear stress, it redistributes along the cell borders into the flow direction. IGPR-1 activation stimulated actin stress fiber assembly and cross-linking with vinculin. Moreover, we noted that IGPR-1 stabilizes cell-cell junctions of endothelial cells as determined by staining of cells with ZO1. Mechanistically, shear stress stimulated activation of AKT Ser/Thr kinase 1 (AKT1), leading to phosphorylation of IGPR-1 at Ser-220. Inhibition of this phosphorylation prevented shear stress-induced actin fiber assembly and endothelial cell remodeling. Our findings indicate that IGPR-1 is an important player in endothelial cell mechanosensing, insights that have important implications for the pathogenesis of common maladies, including ischemic heart diseases and inflammation.