Clathrin-mediated endocytosis regulates the signalling activity and turnover of multiple plasma membrane proteins. Interfering with endocytosis can therefore have complex effects on developmental processes. William Sessa and colleagues () investigate the role of the Dynamin 2 (Dnm2) GTPase - a key component of the endocytic machinery - during angiogenesis in mice. Using endothelial cells in culture, they find that downregulation of Dnm2 impairs angiogenesis, even though vascular endothelial growth factor (VEGF) signalling is enhanced - due to increased surface levels of the receptor. This is in contrast to previous work suggesting that endocytosis might promote VEGF signalling. The authors ascribe the Dnm2 knockdown-induced defect in vessel formation at least partially to disrupted integrin turnover: focal adhesion size is increased and inactive integrin receptors appear to accumulate on the cell surface. Importantly, these observations hold true in vivo: conditional deletion of Dnm2 in mouse embryos causes severe angiogenic phenotypes that are consistent with impaired integrin function.
