Human Vascular endothelial growth factor receptor 2(KDR, VEGFR-2) is a member of the class III subfamily of receptor tyrosine kinases (RTKs). KDR is involved in a number of fundamental biological processes such as the regulation of angiogenesis, vascular development, vascular permeability, and embryonic hematopoiesis. It also plays an essential role in promoting proliferation, survival, migration and differentiation of endothelial cells, reorganization of the actin cytoskeleton. VEGFR2 is identified as the receptor for VEGF and VEGFC and an early marker for endothelial cell progenitors, whose expression is restricted to endothelial cells in vivo.The adaptor protein SHB has been shown to interact with VEGFR2 in receptor tyrosine kinase signaling. In addition, VEGFR2 is able to interact with HIV-1 extracellular Tat protein upon VEGF activation, and seems to enhance angiogenesis in Kaposi's sarcoma lesions. VEGF R2 is thought to be the primary inducer of VEGF-mediated blood vessel growth, while VEGF R3 plays a significant role in VEGF-C and VEGF-D-mediated lymphangiogenesis.