Role of Afadin in Vascular Endothelial Growth Factor– and Sphingosine 1-Phosphate–Induced Angiogenesis

Rationale: Angiogenesis contributes to physiological and pathological conditions, including atherosclerosis. The Rap1 small G protein regulates vascular integrity and angiogenesis. However, little is known about the effectors of Rap1 involved in angiogenesis. It is not known whether afadin, an adherens junction protein that connects immunoglobulin-like adhesion molecule nectins to the actin cytoskeleton and binds activated Rap1, plays a role in angiogenesis. Objective: We investigated the role of endothelial afadin in angiogenesis and attempted to clarify the underlying molecular mechanism. Methods and Results: Treatment of human umbilical vein endothelial cells (HUVECs) with vascular endothelial growth factor (VEGF) and sphingosine 1-phosphate (S1P) induced the activation of Rap1. Activated Rap1 regulated intracellular localization of afadin. Knockdown of Rap1 or afadin by small interfering RNA inhibited the VEGF- and S1P-induced capillary-like network formation, migration, and proliferation, and increas...