EVL regulates VEGF receptor 2 internalization and signaling in developmental angiogenesis

Endothelial tip cells are essential for VEGF-induced angiogenesis, but underlying mechanisms are elusive. The Ena/VASP protein family, consisting of EVL, VASP and Mena, plays a pivotal role in axon guidance. Given that axonal growth cones and endothelial tip cells share many common features, from the morphological to the molecular level, we investigated the role of Ena/VASP proteins in angiogenesis. EVL and VASP, but not Mena, were expressed in endothelial cells of the postnatal mouse retina. Global deletion of EVL (but not VASP) compromised the radial sprouting of the vascular plexus in mice. Similarly, endothelial-specific EVL deletion compromised the radial sprouting of the vascular plexus and reduced the endothelial tip cell density and filopodia formation. Gene sets involved in blood vessel development and angiogenesis were down-regulated in EVL-deficient P5-retinal endothelial cells. Consistently, EVL-deletion impaired VEGF-induced endothelial cell proliferation and sprouting, and reduced the internalization and phosphorylation of VEGF receptor-2 and its downstream signaling via the MAPK/ERK pathway. Together, we show that endothelial EVL regulates sprouting angiogenesis via VEGF receptor-2 internalization and signaling.