VASCULAR ENDOTHELIAL GROWTH-FACTOR INDUCES VE-CADHERIN TYROSINE PHOSPHORYLATION IN ENDOTHELIAL-CELLS

Interendothelial junctions play an important role in the regulation of endothelial functions, such as vasculogenesis, angiogenesis, and vasc ular permeability, In this paper we show that vascular endothelial gro wth factor (VEGF), a potent inducer of new blood vessels and vascular permeability in vivo, stimulated the migration of endothelial cells af ter artificial monolayer wounding and induced an increase in paracellu lar permeability of human umbilical vein endothelial cells (HUVECs). F urthermore, VEGF increased phosphotyrosine labeling at cell-cell conta cts. Biochemical analyses revealed a strong induction of VEGF-receptor -2 (flk-1/KDR) tyrosine-autophosphorylation by VEGF which was maximal after 5 minutes and was followed by receptor downregulation, 15 minute s to 1 hour after VEGF stimulation the endothelial adherens junction c omponents VE-cadherin, beta-catenin, plakoglobin, and p120 were maxima lly phosphorylated on tyrosine, while alpha-catenin was not modified. PECAM-1/CD31, another cell-cell junctional adhesive molecule, was tyro sine phosphorylated with similar kinetics in response to VEGF In contr ast, activation of VEGF-receptor-1 (Flt-1) by its specific ligand plac enta growth factor (PIGF) had no effect on the tyrosine phosphorylatio n of cadherins and catenins, Despite the rapid and transient receptor activation and the subsequent tyrosine phosphorylation of adherens jun ction proteins the cadherin complex remained stable and associated wit h junctions. Our results demonstrate that the endothelial adherens jun ction is a downstream target of VEGFR-2 signaling and suggest that tyr osine phosphorylation of its components may be involved in the the loo sening of cell-cell contacts in established vessels to modulate transe ndothelial permeability and to allow sprouting and cell migration duri ng angiogenesis.