Necl-5/Poliovirus Receptor Interacts With VEGFR2 and Regulates VEGF-Induced Angiogenesis

Rationale: Vascular endothelial growth factor (VEGF), a major proangiogenic agent, exerts its proangiogenic action by binding to VEGF receptor 2 (VEGFR2), the activity of which is regulated by direct interactions with other cell surface proteins, including integrin alpha(v)beta(3). However, how the interaction between VEGFR2 and integrin alpha(v)beta(3) is regulated is not clear. Objective: To investigate whether Necl-5/poliovirus receptor, an immunoglobulin-like molecule that is known to bind integrin alpha(v)beta(3), regulates the interaction between VEGFR2 and integrin alpha(v)beta(3), and to clarify the role of Necl-5 in the VEGF-induced angiogenesis. Methods and Results: Necl-5-knockout mice displayed no obvious defect in vascular development; however, recovery of blood flow after hindlimb ischemia and the VEGF-induced neovascularization in implanted Matrigel plugs were impaired in Necl-5-knockout mice. To clarify the mechanism of the regulation of angiogenesis by Necl-5, we investigated the roles of Necl-5 in the VEGF-induced angiogenic responses in vitro. Knockdown of Necl-5 by siRNAs in human umbilical vein endothelial cells (HUVECs) inhibited the VEGF-induced capillary-like network formation on Matrigel, migration, and proliferation, and conversely, enhanced apoptosis. Coimmunoprecipitation assays showed the interaction of Necl-5 with VEGFR2, and knockdown of Necl-5 prevented the VEGF-induced interaction of integrin alpha(v)beta(3) with VEGFR2. Knockdown of Necl-5 suppressed the VEGFR2-mediated activation of downstream proangiogenic and survival signals, including Rap1, Akt, and endothelial nitric oxide synthase. Conclusions: These results demonstrate the critical role of Necl-5 in angiogenesis and suggest that Necl-5 may regulate the VEGF-induced angiogenesis by controlling the interaction of VEGFR2 with integrin alpha(v)beta(3), and the VEGFR2-mediated Rap1-Akt signaling pathway. (Circ Res. 2012;110:716-726.)