Editors' ChoiceAngiogenesis

Signaling from the Surface and the Nucleus

Science Signaling  28 Oct 2014:
Vol. 7, Issue 349, pp. ec303
DOI: 10.1126/scisignal.aaa1557

Coordination of neurons and blood vessels results in neuronal activity stimulating the formation of blood vessels that deliver nutrients and oxygen and remove waste. The mouse retina is a convenient system to study angiogenesis and neovascularization, processes that require retinal ganglion cells (RGCs). Joyal et al. found that knocking down F2rl1, a G protein-coupled receptor (GPCR) of the protease-activated receptor family, by intravitreal injection (predominantly affecting RGCs) impaired retinal developmental neovascularization. Injection of the F2rl1 agonist peptide (F2rl1-AP) stimulated neovascularization in wild-type mice, but not in mice lacking RGCs. Conditioned medium from cultured RGCs exposed to F2rl1-AP stimulated proangiogenic vascular sprouting when applied to aortic explants from wild-type or F2rl1-/- mice. Electron microscopy revealed that F2rl1 was present in the nucleus of RGCs, and exposure of the murine RGC cell line RGC-5 to trypsin (to cleave and activate the receptor) resulted in the nuclear accumulation of F2rl1. Reconstitution of RGCs in F2rl1-/- mice by injection of lentivirus encoding wild-type F2rl1 stimulated the expression of both Vegfa and Ang1, which encode the angiogenic factors VEGF-A and angiopoietin-1, respectively, promoted developmental angiogenesis. In contrast reconstitution with a mutant that could not translocate to the nucleus resulted in increased Ang1, but not Vegfa expression; reconstitution with a completely nuclear localized mutant resulted in increased Vegfa expression. Chromatin immunoprecipitation experiments with both transfected HEK293 and RGC-5 cells indicated that activated F2rl1 bound to the Vegfa promoter. Exposure of RGC-5 cells to F2rl1-AP stimulated an interaction between the transcription factor Sp1 and F2rl1 (detected by coimmunoprecipitation). The translocation of F2r11 to the nucleus required sorting nexin 11 (Snx11) and microtubules. Stimulation of F2rl1 in the presence of microtubule-disrupting agents, in cells in which Snx11 was knocked down, or in cells expressing a mutant F2rl1 that did not translocate to the nucleus resulted in the expression of Ang1, but not Vegfa. Thus, these data indicated that F2rl1 triggers distinct transcriptional events involved in initiating angiogenesis (Vegfa) and stabilizating vessels (Ang1), and these responses are governed by the subcellular localization of F2rl1.

J.-S. Joyal, S. Nim, T. Zhu, N. Sitaras, J. C. Rivera, Z. Shao, P. Sapieha, D. Hamel, M. Sanchez, K. Zaniolo, M. St-Louis, J. Ouellette, M. Montoya-Zavala, A. Zabeida, E. Picard, P. Hardy, V. Bhosle, D. R. Varma, F. Gobeil Jr, C. Beauséjour, C. Boileau, W. Klein, M. Hollenberg, A. Ribeiro-da-Silva,.G. Andelfinger, S. Chemtob, Subcellular localization of coagulation factor II receptor-like 1 in neurons governs angiogenesis. Nat. Med. 20, 1165–1173 (2014). [PubMed]