Integrin α9β1 Directly Binds to Vascular Endothelial Growth Factor (VEGF)-A and Contributes to VEGF-A-induced Angiogenesis

Anne E. Hawkridge,Bradford A. Young,Dean Sheppard,Rachel B. Issaka,Amha Atakilit,Nicholas E. Vlahakis,Nancy Boudreau

doi:10.1074/jbc.m609323200

Abstract

Vascular endothelial growth factor A (VEGF-A) is a potent inducer of angiogenesis. We now show that VEGF-A-induced adhesion and migration of human endothelial cells are dependent on the integrin alpha9beta1 and that VEGF-A is a direct ligand for this integrin. Adhesion and migration of these cells on the 165 and 121 isoforms of VEGF-A depend on cooperative input from alpha9beta1 and the cognate receptor for VEGF-A, VEGF receptor 2 (VEGF-R2). Unlike alpha3beta1or alphavbeta3 integrins, alpha9beta1 was also found to bind the 121 isoform of VEGF-A. This interaction appears to be biologically significant, because alpha9beta1-blocking antibody dramatically and specifically inhibited angiogenesis induced by VEGF-A165 or -121. Together with our previous findings that alpha9beta1 directly binds to VEGF-C and -D and contributes to lymphangiogenesis, these results identify the integrin alpha9beta1 as a potential pharmacotherapeutic target for inhibition of pathogenic angiogenesis and lymphangiogenesis.

Highlights

R2, its angiogenic effect may be modulated through nonVEGF-R2 pathways, including neuropillin-2 [7, 8], heparin sulfate proteoglycans [8], and integrins (9 –13)
We show that Vascular endothelial growth factor A (VEGF-A)-induced angiogenesis in chick CAMs can be inhibited by antibody to ␣9␤1, suggesting that this interaction could have in vivo relevance
Integrin ␣9␤1 Mediates Cell Adhesion and Migration on VEGF-A—To determine whether cells use integrin ␣9␤1 to adhere to VEGF-A, adhesion assays were performed using two different cell lines, ␣9- and mock-transfected MEF and SW-480 cells (Fig. 1)

Summary

Introduction

R2, its angiogenic effect may be modulated through nonVEGF-R2 pathways, including neuropillin-2 [7, 8], heparin sulfate proteoglycans [8], and integrins (9 –13). Integrins are heterodimeric transmembrane proteins that can mediate cell adhesion, migration, and proliferation Following activation by their respective ligands, integrins can modulate these cell functions through coordinated cross-talk with growth factor receptors, including VEGF receptors [14, 15] often utilizing signaling proteins common to both receptor pathways [13, 16, 17]. A previous study has shown that the integrins ␣3␤1 and ␣v␤3 modulate cellular interactions with the 165-kDa form of VEGF-A but not the 121-kDa form [18] These results suggest that any association between these integrins and VEGF-A likely does not involve interaction with sequences encoded by exon 6. We show that VEGF-A (but not bFGF)-induced angiogenesis in chick CAMs can be inhibited by antibody to ␣9␤1, suggesting that this interaction could have in vivo relevance

Methods

Results

Conclusion