Vascular endothelial growth factor receptor 2 tyrosine kinase and Vascular endothelial growth factor receptor 3 tyrosine kinase (VEGFR-2 (also known as KDR or FLK-1) and VEGFR-3 (also known as Flt-4))

Vascular endothelial growth factor receptor 2 and 3 tyrosine kinases are single-pass transmembrane proteins with large extracellular domains comprising seven immunoglobulin-like subdomains, a transmembrane segment, and a split intracellular tyrosine kinase domain[1][2][4][6]. VEGFR-2 is the principal receptor mediating VEGF-driven angiogenesis and vascular permeability, while VEGFR-3 mainly controls lymphangiogenesis through interaction with VEGF-C/D[2][3][4]. Both utilize kinase domain autophosphorylation to trigger a range of intracellular signaling cascades—most notably the MAPK and PI3K/AKT pathways—leading to endothelial cell proliferation, migration, and survival[1][3][5]. Aberrant expression or activation of these receptors is a hallmark of several cancers and vascular diseases, making them prime targets for small molecule inhibitors and antibody therapies in oncology and ophthalmology[1][3][5]. Structural features such as the glycine-rich ATP-binding loop, catalytic HRD motif, and DFG motif regulate enzymatic activity and are exploited in the design of selective inhibitors[1][2]. Both are commonly referred to by abbreviations (VEGFR-2/KDR, VEGFR-3/Flt-4), but should be distinguished in clinical and biochemical contexts due to their distinct physiological and pathological roles.

Other names

Kinase insert domain receptor (KDR)Fetal liver kinase 1 (FLK-1)Fms-like tyrosine kinase 4 (Flt-4)

Inhibition of kinase activity by competitive binding at ATP-binding site; Blockade of ligand binding/VEGF interaction to prevent receptor dimerization and activation; Allosteric modulation of tyrosine kinase domain; Prevention of downstream signal transduction (MAPK/ERK, PI3K/AKT, PKC)