CCN3 (NOV) is a novel angiogenic regulator of the CCN protein family

Abstract

CCN3 (NOV) is a matricellular protein of the CCN family, which also includes CCN1 (CYR61), CCN2 (CTGF), CCN4 (WISP-1), CCN5 (WISP-2), and CCN6 (WISP-3). During development, CCN3 is expressed widely in derivatives of all three germ layers, and high levels of expression are observed in smooth muscle cells of the arterial vessel wall. Altered expression of CCN3 has been observed in a variety of tumors, including hepatocellular carcinomas, Wilm's tumors, Ewing's sarcomas, gliomas, rhabdomyosarcomas, and adrenocortical carcinomas. To understand its biological functions, we have investigated the activities of purified recombinant CCN3. We show that in endothelial cells, CCN3 supports cell adhesion, induces directed cell migration (chemotaxis), and promotes cell survival. Mechanistically, CCN3 supports human umbilical vein endothelial cell adhesion through multiple cell surface receptors, including integrins αvβ3, α5β1, α6β1, and heparan sulfate proteoglycans. In contrast, CCN3-induced cell migration is dependent on integrins αvβ3 and α5β1, whereas α6β1 does not play a role in this process. Although CCN3 does not contain a RGD sequence, it binds directly to immobilized integrins αvβ3 and α5β1, with half-maximal binding occurring at 10 nM and 50 nM CCN3, respectively. Furthermore, CCN3 induces neovascularization when implanted in rat cornea, demonstrating that it is a novel angiogenic inducer. Together, these findings show that CCN3 is a ligand of integrins αvβ3 and α5β1, acts directly upon endothelial cells to stimulate pro-angiogenic activities, and induces angiogenesis in vivo.