Tyrosine-protein kinase that acts as a cell-surface receptor for VEGFA, VEGFB and PGF, and plays an essential role in the development of embryonic vasculature, the regulation of angiogenesis, cell survival, cell migration, macrophage function, chemotaxis, and cancer cell invasion. Acts as a positive regulator of postnatal retinal hyaloid vessel regression (PubMed:30936473). May play an essential role as a negative regulator of embryonic angiogenesis by inhibiting excessive proliferation of endothelial cells. Can promote endothelial cell proliferation, survival and angiogenesis in adulthood. Its function in promoting cell proliferation seems to be cell-type specific. Promotes PGF-mediated proliferation of endothelial cells, and proliferation of some types of cancer cells, but does not promote proliferation of normal fibroblasts. Has very high affinity for VEGFA and relatively low protein kinase activity; may function as a negative regulator of VEGFA signaling by limiting the amount of free VEGFA and preventing its binding to KDR. Modulates KDR signaling by forming heterodimers with KDR. Ligand binding leads to the activation of several signaling cascades. Activation of PLCG leads to the production of the cellular signaling molecules diacylglycerol and inositol 1,4,5-trisphosphate and the activation of protein kinase C. Mediates phosphorylation of PIK3R1, the regulatory subunit of phosphatidylinositol 3-kinase, leading to the activation of phosphatidylinositol kinase and the downstream signaling pathway. Mediates activation of MAPK1/ERK2, MAPK3/ERK1 and the MAP kinase signaling pathway, as well as of the AKT1 signaling pathway. Phosphorylates SRC, YES1 and PLCG, and may also phosphorylate CBL. Promotes phosphorylation of AKT1 and PTK2/FAK1 (By similarity). ATP + L-tyrosyl-[protein] = ADP + H(+) + O-phospho-L-tyrosyl-[protein] Present in an inactive conformation in the absence of bound ligand. Binding of VEGFA, VEGFB or PGF leads to dimerization and activation by autophosphorylation on tyrosine residues (By similarity). Interacts with VEGFA, VEGFB and PGF. Monomer in the absence of bound VEGFA, VEGFB or PGF. Homodimer in the presence of bound VEGFA, VEGFB and PGF. Can also form a heterodimer with KDR. Interacts (tyrosine phosphorylated) with CBL, CRK, GRB2, NCK1, PIK3R1, PLCG, PSEN1 and PTPN11. Probably interacts with PTPRB. Interacts with RACK1. Identified in a complex with CBL and CD2AP (By similarity). Autophosphorylation promotes ubiquitination and endocytosis. The second and third Ig-like C2-type (immunoglobulin-like) domains are sufficient for VEGFA binding. N-glycosylated. Ubiquitinated after VEGFA-mediated autophosphorylation, leading to proteolytic degradation. Autophosphorylated on tyrosine residues upon ligand binding. Autophosphorylation occurs in trans, i.e. one subunit of the dimeric receptor phosphorylates tyrosine residues on the other subunit. Phosphorylation at Tyr-1169 is important for interaction with PLCG. Phosphorylation at Tyr-1213 is important for interaction with PIK3R1, PTPN11, GRB2, and PLCG. Phosphorylation at Tyr-1328 is important for endocytosis and for interaction with CBL, NCK1 and CRK. Is probably dephosphorylated by PTPRB (By similarity). Embryonic lethality at about 9 dpc, due to defects in the formation and organization of the vascular network (PubMed:7596436, PubMed:9689083). Mice display abnormal blood island structures in the yolk sac, leading to defects in the organization of the vascular endothelium, excess growth and disorganization of embryonic and extraembryonic vasculature, including the endocardium and the microvasculature (PubMed:7596436). Reduced vascular sprout formation and migration (PubMed:14982871). Loss of retinal hyaloid vessel regression from postnatal day 3 (P3) to P8 (PubMed:30936473). Mice expressing a mutant protein that lacks the kinase domain survive and have no apparent phenotype (PubMed:9689083). Belongs to the protein kinase superfamily. Tyr protein kinase family. CSF-1/PDGF receptor subfamily.