ECSM2, an endothelial specific VE-cadherin binding protein, has a tyrosine phosphorylation site essential to cell migration

Endothelial cell-specific molecule 2 (ECSM2) is a transmembrane protein located in cell-cell junction of endothelial cells (EC). ECSM2 was determined to play an important role in vascular development, EC migration, apoptosis and proliferation, however, no functional domains were determined in intracellular and extracellular region of ECSM2. In current work, functional domains of ECSM2, the relationship of ECSM2 with other endothelial specific protein such as VE-cadherin and the role of ECSM2 in neovascular diseases were determined. It was shown that the 54th amino acid residue of ECSM2 extracellular domain was a tyrosine phosphorylation site, whose mutation led to the loss of EGF-induced tyrosine phosphorylation and inhibition of cell migration. In primary human umbilical vein endothelial cells, ECSM2 bound with VE-cadherin and VEGF stimulation enhanced their binding. In hepatocellular carcinoma, ECSM2 expression was increased, as compared with para-cancerous tissue. This data firstly revealed the functional sites of ECSM2, the crosstalk between ECSM2 and other endothelial cell specific molecules, the expression of ECSM2 in tissues of angiogenesis diseases, thus providing understanding about ECSM2 in depth.