Adhesion of Endothelial Cells to NOV Is Mediated by the Integrins αvβ3 and α5β1

NOV is a member of the CCN family of matricellular proteins. We have shown previously that Nov is strongly expressed by vascular smooth muscle cells (VSMCs) of the rat carotid artery. However, 7 days after injury, Nov expression is down-regulated, except near the luminal surface of the developing intima, where it is strongly expressed. These data suggested that NOV might be involved in the regulation of endothelial cell adhesion. NOV promoted the adhesion of human umbilical vein endothelial cells (HUVECs), which was abolished by anti-NOV antibody. HUVEC adhesion to NOV required divalent cations and was inhibited by GRGDS peptide, implicating integrins in the adhesion mechanism. Monoclonal antibodies (mAbs) against αvβ3 inhibited adhesion of HUVECs to NOV, and NOV was shown to bind to αvβ3. Anti-α5β1 mAbs also inhibited HUVEC adhesion to NOV, but adhesion via α5β1 was mediated by fibronectin. HUVEC adhesion to NOV caused intracellular signalling, as evidenced by increased phosphotyrosine content of focal adhesion kinase. Together with evidence that Nov expression in a variety of tissues is restricted to blood vessels containing VSMCs, these data are consistent with a role for NOV in endothelial cell adhesion in vascular homeostasis and in the response to injury.