Endomucin regulates the endothelial cytoskeleton independent of VEGF

The endothelial glycocalyx, lining the apical surface of the endothelium, is involved in a host of vascular processes. The layer contains a network of membrane-bound proteoglycans and glycoproteins. One such glycoprotein is endomucin (EMCN), which our lab has revealed is a modulator of VEGFR2 function. Intravitreal injection of siEMCN into the eyes of P5 mice impairs vascular development. In vitro silencing of EMCN suppresses VEGF-induced proliferation and migration. Signaling pathways that drive cell migration converge on cytoskeletal remodeling. By coupling co-immunoprecipitation with liquid chromatography/mass spectrometry, we identified interactions between EMCN, and proteins associated with actin cytoskeleton organization. The aim of the study was to investigate the influence of EMCN on cytoskeleton dynamics in angiogenesis. EMCN depletion resulted in reduction of F-actin levels, whereas overexpression of EMCN induced membrane protrusions in cells that were rich in stress fibers. The reorganization of the actin filaments did not depend on VEGFR2 signaling, suggesting that EMCN is a potential connection between the cytoskeleton and the glycocalyx.