VEGFR

VEGFRs consist of three subtypes, the fms-like tyrosine kinase Flt-1 (VEGFR1/Flt-1), the kinase domain region, also referred to as fetal liver kinase (VEGFR2/KDR/Flk-1), and Flt-4 (VEGFR3). Each receptor has seven immunoglobulinlike domains in the extracellular domain, a single transmembrane region, and a consensus tyrosine kinase sequence interrupted by a kinase insert domain. VEGFR1 and 2 are expressed on vascular endothelial cells, whereas VEGFR3 is expressed on lymphatic endothelial. The VEGF family members VEGF-A, -B, -C, -D, -E, and PlGF, and the human immunodeficiency (HIV) Tat protein bind in specific patterns to three related receptor protein tyrosine kinases, VEGFR1, 2, and 3, and induce the formation of homo- and heteromeric receptor complexes. Binding of VEGF to VEGFR causes dimerization and autophosphorylation of the receptor. Intracellular proteins such as VEGFR-associated protein (VRAP), PLC, and Sck that associate with specific tyrosine residues of VEGFR are phosphorylated upon receptor activation. Several signal transduction pathways are activated by the binding of VEGF to its receptor, leading to increased proliferation, survival, permeability, and migration of cells.