Description_x000D_ Application_x000D_ VEGF Receptor-1 (Flt-1)/Fc chimera human may be used tostudy vasculogenesis and angiogenesis._x000D_ Biochem/physiol Actions_x000D_ VEGF Receptor-1 (VEGF R1) also known as Flt-1 belongs to class III subfamily of RTKs and is a potent VEGF antagonist expressed mainly in endothelial cells. VEGF R1 binds to vascular endothelial growth factor B (VEGF-B) and regulates the activity of plasminogen activator in endothelial cells. It also assists endothelial cells in the proper spatial organization of lumen-containing vessels. Additionally, alternatively spliced VEGF R1 pre-mRNA helps in regulating the VEGF activity in angiogenesis. VEGF R1 also activates PLC gamma which in turn produces cellular signaling molecules diacylglycerol as well as inositol 1,4,5-trisphosphate and activates protein kinase C._x000D_ VEGF receptors, class III receptor tyrosine kinases, have seven Ig like extracellular motifs and a tyrosine kinase intracellular domain split by a kinase insert sequence. VEGFR 1 was originally called fms like tyrosine kinase 1 (flt 1), indicating its homology to receptors of PDGF, M CSF, and SCF. VEGFR 1 is one of the five receptor tyrosine kinases (KDR/Flk-1, Flt-4, tie-1 and tek/tie-2) whose expression is almost exclusively restricted to endothelial cells. These receptors are likely to play central roles in vasculogenesis and angiogenesis. Recombinant VEGF R1 binds VEGF with high affinity and is a potent VEGF inhibitor. VEGFR 1 and 2 are both expressed in an endothelial cell-specific manner and are detectable in virtually all tissues in adults and embryos. Hypoxia induces endothelial cell expression of VEGFR 1 but not VEGFR 2. Monocytes express VEGFR 1 and 2 and can migrate to the site of VEGF release, but this response appears to be VEGFR 1 mediated. VEGFR 2 is also expressed in pancreatic duct cells. VEGFR 2 is involved in commitment of endothelial-cell lineages and to cell proliferation, while VEGFR 1 seems to be responsible for guiding endothelial cells into the proper spatial organization into lumen-containing vessels. VEGFR 2 is a key marker for pluripotent HSCs. Neurophilins, a group of unrelated receptors for some VEGF family members may also act as coreceptors to facilitate VEGF binding to VEGFR 2. VEGFR 3 is a specific marker for lymphatic vessels. VEGFR 3 has also been detected on some high endothelial venules, in embryonic pre-lymphatic blood vessels, some tumor blood vessels, and certain hematopoietic and leukemia cells._x000D_ Physical form_x000D_ Lyophilized from a 0.2 μm filtered solution in 20 mM MOPS, 500 mM sodium chloride, 0.05% CHAPS, pH 7.0 containing 50 μg bovine serum albumin per 1 μg of cytokine_x000D_ Analysis Note_x000D_ The biological activity is measured by its ability to Inhibit the VEGF-dependent proliferation of human umbilical vein endothelial cells.