Abstract
Our previous studies have identified mitsugumin 53 (MG53) as a novel regulator for angiogenesis by directly entering endothelial cells and modulating focal adhesion kinase (FAK) activation, but little is known about how rhMG53 is taken up by cells and how rhMG53 mediates cell movement. In the present study, we demonstrated that the knockdown of caveolin-1 and the clathrin inhibitor, pitstop-2, both significantly reduced the entry of rhMG53 into endothelial cells, indicating caveolae-dependent and clathrin-dependent endocytosis during this process. The internalised rhMG53 remarkably inhibited the phosphorylation of FAK and the downstream signalling molecule paxillin, consequently resulting in a significant decrease in focal adhesion turnover during endothelial cell spreading and migration. Using a 3D collagen culture model, we further found that rhMG53 significantly inhibited tip cell formation and tubulogenesis. Furthermore, rhMG53 also remarkably prevented alkaline injury-induced corneal neovascularization in vivo. Taken together, these results indicate that rhMG53 inhibits angiogenesis through regulating focal adhesion turnover and tip cell formation. This may elucidate novel molecular mechanisms involved in rhMG53 uptake and rhMG53-modulated endothelial cell function and provide evidence for the potential utility of rhMG53 in treating diseases with excessive angiogenesis.