0391 : Molecular mechanisms of ANGPTL4-induced regulation of vascular integrity

Cardiovascular ischemic injuries are associated with vascular damage induced by loss of endothelial junction integrity. Deciphering the mechanisms involved in the regulation of vascular integrity is of major interest in order to develop relevant therapeutic cardioprotective approaches to achieve tissue protection. Our team identified angiopoietin-like 4 (ANGPTL4) as a hypoxiainduced target and a key regulator of vascular integrity by protecting interendothelial cell junctions. However ANGPTL4 receptors and downstream signaling pathways which mediate vasoprotective effect remain poorly investigated. Using both in vitro binding (Surface Plasmon Resonance, SPR) and functional in vivo assays, we show that ANGPTL4 binds αvβ3 integrin and that this interaction is necessary to mediate vasoprotective effects. In addition, ANGPTL4 induces phosphorylation of Tyr773 of β3 integrin subunit and reorganization of focal adhesions in endothelial cells. Mechanistically, binding of ANGPTL4 to αvβ3 leads to Src recruitment and its sequestration away from VEGFR2 combined to a diminished Src signaling downstream VEGFR2, thereby inducing stabilization of both VEGFR2/VE-cadherin and VEGFR2/ αvβ3 complexes. Thus, ANGPTL4 strengthens maturation of adherens junctions, characterized by a transition from a zipper to linear organization of VEcadherin organization. Altogether, our results identify a novel mechanism by which ANGPTL4 counteracts hypoxia-driven vascular permeability through αvβ3 binding, modulation of VEGFR2/Src kinase signaling and endothelial junction stabilization.