PMID: 22318724
Parker MW, Xu P, Li X, Vander Kooi CW
Structural basis for the selective vascular endothelial growth factor-A (VEGF-A) binding to neuropilin-1.
J Biol Chem. 2012 Feb 7.
Neuropilin-1 (Nrp1) is an essential receptor for angiogenesis that binds to VEGF-A. Nrp1 directly binds to VEGF-A with high affinity, but the nature of their selective binding has remained unclear. Nrp1 was initially reported to bind to the exon seven encoded region of VEGF-A and function as an isoform specific receptor for VEGF-A164/5. Recent data has implicated exon eight encoded residues, which are found in all pro-angiogenic VEGF-A isoforms, in Nrp binding. We have determined the crystal structure of the exon 7/8 encoded VEGF-A heparin binding domain (HBD) in complex with the Nrp1 b1 domain. This structure clearly demonstrates that residues from both exon seven and eight physically contribute to Nrp1 binding. Using an in vitro binding assay, we have determined the relative contributions of exon seven and eight encoded residues. We demonstrate that the exon eight encoded C-terminal arginine is essential for the interaction of VEGF-A with Nrp1 and mediates high-affinity Nrp binding. Exon seven encoded electronegative residues make additional interactions with the L1 loop of Nrp1. While otherwise conserved, the primary sequence of Nrp1 and Nrp2 differ significantly in this region. We further show that VEGF-A164 binds fifty-fold more strongly to Nrp1 than Nrp2. Direct repulsion between the electronegative exon seven encoded residues of the HBD and the electronegative L1 loop found only in Nrp2 is found to significantly contribute to the observed selectivity. The results reveal the basis for the potent and selective binding of VEGF-A164 to Nrp1.