VE-Cadherin-mediated cell-cell interaction suppresses sprouting via signaling to MLC2 phosphorylation.

During new blood vessel formation, the cessation of angiogenic sprouting is necessary for the generation of functional vasculature. How sprouting is halted is not known, but it is contemporaneous with the development of stable intercellular junctions [1]. We report that VE-cadherin, which is responsible for endothelial adherens junction organization [2, 3], plays a crucial role in the cessation of sprouting. Abrogating VE-cadherin function in an organotypic angiogenesis assay and in zebrafish embryos stimulates sprouting. We show that VE-cadherin signals to Rho-kinase-dependent myosin light-chain 2 phosphorylation, leading to actomyosin contractility [4], which regulates the distribution of VE-cadherin at cell-cell junctions. VE-cadherin antagonizes VEGFR2 signaling, and consequently, inhibition of VE-cadherin, Rho-kinase, or actomyosin contractility leads to VEGF-driven, Rac1-dependent sprouting. These findings suggest a novel mechanism by which cell-cell adhesion suppresses Rac1-dependent migration and sprouting by increasing actomyosin contractility at cell junctions.