A redox-resistant VEGFR2 C1208S mutant sustains DLL4-dependent angiogenesis in endothelial cells under oxidative...

Vascular endothelial growth factor receptor 2 (VEGFR2) is a central regulator of angiogenesis, and reactive oxygen species (ROS) act as signaling molecules that modulate endothelial function. How the receptor itself translates an oxidative environment into angiogenic output remains poorly defined. Here we examined the redox-sensitive residue Cys1208 in VEGFR2-mediated angiogenesis under oxidative stress. Human umbilical vein endothelial cells (HUVECs) overexpressing wild-type (WT) or C1208S mutant VEGFR2 were analyzed for intracellular ROS, VEGFR2 signaling and subcellular distribution, angiogenic function, and downstream gene expression. Oxidant challenge increased intracellular ROS in both cell types, with levels in C1208S cells at least as high as those in WT cells, indicating that the substitution does not lower the cellular oxidant burden. Nevertheless, C1208S cells preserved VEGFR2 distribution, sustained VEGF-induced VEGFR2 phosphorylation, and maintained VEGF-dependent tube formation and migration under oxidative stress. Among the pro-angiogenic genes examined, DLL4 was selectively restored by VEGF in C1208S cells, and siRNA-mediated DLL4 knockdown abolished the preserved angiogenic responses. These results indicate that Cys1208 confers susceptibility to oxidative inactivation of VEGFR2, and that eliminating this susceptibility sustains DLL4-dependent angiogenic signaling, defining a receptor-level redox checkpoint in endothelial cells.