Manickam, Venkatraman

Vascular endothelial growth factor receptor‐2 (VEGFR2) plays a key role in vasculogenesis and pathophysiological angiogenesis. Cell surface levels of VEGFR2 is regulated by endocytosis and secretory transport of newly synthesized receptors to the plasma membrane. The mechanism of VEGFR2 sorting and trafficking along the secretory pathway is not well defined. In the present study, using human endothelial cells we demonstrate that sorting and trafficking of VEGFR2 from the Golgi is regulated by syntaxin 6, a t‐SNARE involved in intra‐Golgi and post‐Golgi membrane fusion events. Loss of syntaxin 6 function results in altered sorting of VEGFR2 from the Golgi resulting in receptor down regulation. Our data support a model in which syntaxin 6 regulates delivery of VEGFR2 from the Golgi apparatus to the cell surface thereby regulating VEGF‐A‐induced endothelial cell proliferation, migration, and morphogenesis. Grant Funding Source NIH

AbstractVascular endothelial growth factor receptor 2 (VEGFR2) plays a key role in physiologic and pathologic angiogenesis. Plasma membrane (PM) levels of VEGFR2 are regulated by endocytosis and secretory transport through the Golgi apparatus. To date, the mechanism whereby the VEGFR2 traffics through the Golgi apparatus remains incompletely characterized. We show in human endothelial cells that binding of VEGF to the cell surface localized VEGFR2 stimulates exit of intracellular VEGFR2 from the Golgi apparatus. Brefeldin A treatment reduced the level of surface VEGFR2, confirming that VEGFR2 traffics through the Golgi apparatus en route to the PM. Mechanistically, we show that inhibition of syntaxin 6, a Golgi-localized target membrane-soluble N-ethylmaleimide attachment protein receptor (t-SNARE) protein, interferes with VEGFR2 trafficking to the PM and facilitates lysosomal degradation of the VEGFR2. In cell culture, inhibition of syntaxin 6 also reduced VEGF-induced cell proliferation, cell migration, and vascular tube formation. Furthermore, in a mouse ear model of angiogenesis, an inhibitory form of syntaxin 6 reduced VEGF-induced neovascularization and permeability. Our data demonstrate the importance of syntaxin 6 in the maintenance of cellular VEGFR2 levels, and suggest that the inhibitory form of syntaxin 6 has good potential as an antiangiogenic agent.