NRP1 Presented in trans to the Endothelium Arrests VEGFR2 Endocytosis, Preventing Angiogenic Signaling and Tumor Initiation

Abstract

Neuropilin 1 (NRP1) modulates angiogenesis by binding vascular endothelial growth factor (VEGF) and its receptor, VEGFR2. We examined the consequences when VEGFR2 and NRP1 were expressed on the same cell (cis) or on different cells (trans). In cis, VEGF induced rapid VEGFR2/NRP1 complex formation and internalization. In trans, complex formation was delayed and phosphorylation of phospholipase Cγ (PLCγ) and extracellular regulated kinase 2 (ERK2) was prolonged, whereas ERK1 phosphorylation was reduced. Trans complex formation suppressed initiation and vascularization of NRP1-expressing mouse fibrosarcoma and melanoma. Suppression in trans required high-affinity, steady-state binding of VEGF to NRP1, which was dependent on the NRP1 C-terminal domain. Compatible with a trans effect of NRP1, quiescent vasculature in the developing retina showed continuous high NRP1 expression, whereas angiogenic sprouting occurred where NRP1 levels fluctuated between adjacent endothelial cells. Therefore, through communication in trans, NRP1 can modulate VEGFR2 signaling and suppress angiogenesis.

Synergistic Binding of Vascular Endothelial Growth Factor-A and Its Receptors to Heparin Selectively Modulates Complex Affinity

“…However, it seems that these classic models might not effectively capture the full complexity of the VEGF system. Recently, new data have surfaced indicating that the role of co-receptors within the VEGF system is dependent on cellular context (30,31). Thus, the goal of the present study was to identify potential mechanistic elements for how co-receptors influence VEGF activity.…”

“…Mice expressing a VEGF isoform unable to bind NRP-1 die before postnatal day 14 because of bleeding in multiple organs or cardiac failure (26 -29), further reinforcing the notion that NRP-1-VEGF 165 interactions are essential for vascular development. Additionally, recent reports suggest that expression of these co-receptors on adjacent cells (trans) as opposed to cis (same cell) with respect to VEGFR-2 on endothelial cells leads to significant changes in signal transduction upon VEGF 165 binding (30,31).…”

Neuropilin 1 binds PDGF-D and is a co-receptor in PDGF-D–PDGFRβ signaling

“…This might be different when PDGFRβ and NRP1 interact in trans, between two adjacent cells or even two different cell types. In the trans situation, physical hindrance would prevent internalization of both PDGFRβ and NRP1 and would lock them at the cell surface, possibly changing signaling kinetics from fast and transient to slow and persistent, as was recently shown for VEGFR2 signaling when NRP1 is presented in trans (Koch et al, 2014). Such a scenario would result in a spatially restricted change of PDGFRβ downstream signaling in a PDGF-D-specific manner.…”

Neuropilin Functions as an Essential Cell Surface Receptor

“…It was first reported that Nrp expressed on CD45 ϩ hematopoietic cells enhances endothelial expressed VEGFR-2 activation, increasing endothelial cell proliferation and angiogenesis (78). More recently, a dramatic difference was shown for Nrp1 interactions with VEGFR-2 in trans (79). In trans, Nrp1 was found to limit receptor internalization and inhibit signal initiation and vascularization.…”