Because of the mostly glycolytic nature of endothelial cell metabolism, the role of mitochondria and mitochondrial shape in angiogenesis, the new blood vessel formation from existing vasculature, has not been studied. Here we show that the mitochondrial fission factor Dynamin related protein 1 (Drp1) unexpectedly limits endosomal VEGFR2 signaling and hence angiogenesis. Drp1 levels were reduced when Human Umbilical Vein Endothelial Cells (HUVECs) were activated, and angiogenesis was accordingly stimulated in HUVECs where DRP1 was silenced. In vivo, constitutive and inducible Drp1 ablation in endothelial cells increased early stage postnatal retina vascular sprouting. Mechanistically, upon VEGF stimulation Drp1 interacted with the internalized VEGFR2 and its early endosome partner Rab5 at the endosomal VEGFR2 signaling platform. Drp1 deletion unleashed VEGFR2 activation and its downstream signaling, indicating that the VEGFR2-Rab5-Drp1 interaction limits VEGFR2 mediated angiogenesis. Our data reveal an unexpected extramitochondrial function of Drp1 in endothelial cells, where it localizes also at the endosomes to constrain the endosomal VEGFR2 signaling platform
