title: Neuropilin-1 and neuropilin-2 enhance VEGF121 stimulated signal transduction by the VEGFR-2 receptor.
abstract: The neuropilin-1 (np1) receptor binds the 165 amino-acid form of vascular endothelial growth factor165 (VEGF165) and functions as an enhancer that potentiates VEGF165 signaling via the VEGFR-2 tyrosine-kinase receptor. To study the mechanism by which neuropilins potentiate VEGF activity we produced a VEGF165 mutant (VEGF165KF) that binds to neuropilins but displays a much lower affinity toward VEGFR-1 and VEGFR-2. VEGF165KF failed to induce VEGFR-2 phosphorylation in cells lacking neuropilins. However, in the presence of np1, VEGF165KF bound weakly to VEGFR-2, induced VEGFR-2 phosphorylation, and activated ERK1/2. Interestingly, VEGF165KF did not promote formation of VEGFR-2/np1 complexes nor did high concentrations of VEGF165KF inhibit VEGF165 induced formation of such complexes, suggesting that VEGF165 does not stabilize VEGFR-2/np1 complexes by forming bridges spanning VEGFR-2 and np1. VEGF121 is a VEGF form that does not bind to neuropilins. Surprisingly, both np1 and neuropilin-2 (np2) enhanced VEGF121-induced phosphorylation of VEGFR-2 and VEGF121-induced proliferation of endothelial cells. The enhancement of VEGF121 activity by np1 was accompanied by a 10-fold increase in binding affinity to VEGFR-2 and was not associated with the formation of new VEGFR-2/np1 complexes. These observations suggest that neuropilins enhance the activity of VEGF forms that do not bind to neuropilins, indicate that np2 is a functional VEGF receptor, and imply that spontaneously formed VEGFR-2/np1 complexes suffice for efficient neuropilin mediated enhancement of VEGF activity.
authors.affiliation: Cancer and Vascular Biology Research Center, Rappaport Research Institute in the Medical Sciences, Bruce Rappoport Faculty of Medicine, Technion, Israel Institute of Technology, Haifa 31096, Israel.
authors.forename: Niva
authors.initials: N
authors.lastname: Shraga-Heled
authors.forename: Ofra
authors.initials: O
authors.lastname: Kessler
authors.forename: Claudia
authors.initials: C
authors.lastname: Prahst
authors.forename: Jens
authors.initials: J
authors.lastname: Kroll
authors.forename: Hellmut
authors.initials: H
authors.lastname: Augustin
authors.forename: Gera
authors.initials: G
authors.lastname: Neufeld
mesh_terms: D019943:Amino Acid Substitution; D002478:Cells, Cultured; D004730:Endothelium, Vascular / Q000166:cytology / Q000502:physiology*; D006801:Humans; D009154:Mutation; D039942:Neuropilin-1 / Q000378:metabolism*; D039943:Neuropilin-2 / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D040281:Vascular Endothelial Growth Factor Receptor-1 / Q000378:metabolism*; D040301:Vascular Endothelial Growth Factor Receptor-2 / Q000378:metabolism*
chemical_list: D039943:Neuropilin-2; D039942:Neuropilin-1; D040281:Vascular Endothelial Growth Factor Receptor-1; D040301:Vascular Endothelial Growth Factor Receptor-2