Ephrin-B2 controls VEGF-induced angiogenesis and lymphangiogenesis

Abstract

In development, tissue regeneration or certain diseases, angiogenic growth leads to the expansion of blood vessels and the lymphatic vasculature. This involves endothelial cell proliferation as well as angiogenic sprouting, in which a subset of cells, termed tip cells, acquires motile, invasive behaviour and extends filopodial protrusions. Although it is already appreciated that angiogenesis is triggered by tissue-derived signals, such as vascular endothelial growth factor (VEGF) family growth factors, the resulting signalling processes in endothelial cells are only partly understood. Here we show with genetic experiments in mouse and zebrafish that ephrin-B2, a transmembrane ligand for Eph receptor tyrosine kinases, promotes sprouting behaviour and motility in the angiogenic endothelium. We link this pro-angiogenic function to a crucial role of ephrin-B2 in the VEGF signalling pathway, which we have studied in detail for VEGFR3, the receptor for VEGF-C. In the absence of ephrin-B2, the internalization of VEGFR3 in cultured cells and mutant mice is defective, which compromises downstream signal transduction by the small GTPase Rac1, Akt and the mitogen-activated protein kinase Erk. Our results show that full VEGFR3 signalling is coupled to receptor internalization. Ephrin-B2 is a key regulator of this process and thereby controls angiogenic and lymphangiogenic growth.

Rab13-dependent Trafficking of RhoA Is Required for Directional Migration and Angiogenesis

“…Whereas it is appreciated that directional cell migration requires trafficking of adhesion and growth factor receptors (8), including that of VEGFR2 (42,49,50), the dependence of directional migration on trafficking of cytoskeletal and motility proteins has come to light only recently. Our finding that Rab13-dependent trafficking of Syx and RhoA is required for directional cell migration resonates with a recent report on the requirement of Rab5-dependent trafficking of Rac and Tiam1 for hepatocyte growth factor-stimulated migration of mouse embryo fibroblasts (14).…”

EphrinB2 Reverse Signaling Protects against Capillary Rarefaction and Fibrosis after Kidney Injury

“…25 In response to VEGFA, ephrinB2 DV MVECs were significantly less migratory than WT MVECs (Figure 5B Figure 5C). Recent studies in lung, retina, and skin 14,15 suggest that ephrinB2 is necessary for VEGFR signaling, by stimulating receptor internalization to endosomes where active signaling occurs. 26 To investigate VEGFR2 internalization in ephrinB2 DV MVECs, an "antibody feeding" assay was performed.…”

“…13 Subsequently, ephrinB2 reverse signaling was shown to regulate both developmental and tumor angiogenesis by activating vascular endothelial growth factor receptor 2 (VEGFR-2). 14,15 In separate studies, pericyte-specific ephrinB2 deficiency indicated that ephrinB2 is essential for normal coverage of the microvasculature by pericytes. 16 In these mutant mice, pericytes did not bind to ECs, resulting in microvascular hemorrhage from unstable capillaries in multiple organs such as lung and skin, leading to perinatal lethality.…”

Gene expression profile of endothelial cells during perturbation of the gut vascular barrier

“…To definitively prove the role of the Wnt/b-catenin signaling pathway in the maintenance of the GVB integrity we used Cdh5(PAC)-CreERT2 mice 30 crossed with b-catenin lox(ex3)/lox(ex3) mice. 31 Crossing these mouse strains we obtained an inducible b-catenin gain-of-function mouse model in which, upon tamoxifen treatment, in VE-cadherin expressing endothelial cells exon 3 is excised from b-catenin gene and therefore it becomes constitutively active.…”