VEGFR-3/FLT-4

Receptor tyrosine kinase VEGFR-3, also known as Flt-4, together with VEGFR-1 (Flt-1) and VEGFR-2 (KDR/Flk-1), are the receptors for vascular endothelial growth factors (VEGF) . The VEGFR family belongs to the class II subfamily of receptor tyrosine kinases (RTKs), containing a large extracellular region which is composed of seven Ig-like domains (D1–D7), a single transmembrane (TM) helix and cytoplasmic region with a tyrosine kinase activity. In VEGFR-3, the fifth Ig homology domain is proteolytically cleaved which results in polypeptides remaining linked by two disulfide bonds. VEGFR-3 is widely expressed on all endothelial cells in early embryogenesis, while, in adult tissues, VEGFR-3 expression disappears from the vascular endothelial cells and is observed only on the lymphatic endothelium. VEGF-C and VEGF-D activation of VEGFR-3 plays an important role in the formation of the lymphatic vessel system.