VEGF-R2, known as KDR, CD309, and Flk-1 (mouse), is a type I transmembrane glycoprotein. It is a member of the CSF-1/PDGF receptor family of type III tyrosine kinase receptors. Human VEGF-R2 is mainly expressed by endothelial cells, embryonic tissues, and megakaryocytes. It plays an important role in the regulation of angiogenesis, vasculogenesis and vascular permeability. The ligands of VEGF-R2 include VEGF-A, VEGF-C, VEGF-D, and VEGF splice isoforms. Ligation of VEGF-R2 with its ligands results in the receptor dimerization and autophosphorylation, stimulating endothelial cell proliferation and migration.