VEGFR-1/Flt-1

Vascular Endothelial Growth Factor (VEGF or VEGF-A) family members are major mediators of vasculogenesis and angiogenesis. Specifically, biological activities attributed to VEGFs include: mitogenic activity on endothelial cells, increased permeability of endothelial cells to proteins, stimulation of monocyte migration across endothelial cells and angiogenic activity. Three VEGF family receptors have been described: Flt-1 (fms-like tyrosine kinase) also known as VEGF R1, KDR (kinase-insert domain-containing receptor) also known as Flk-1 and VEGF R2, and Flt-4 also known as VEGF R3. The three receptors contain seven extracellular immunoglobulin-like domains and share substantial sequence homology. In addition, neuropilin-1, a neuronal receptor, also acts as a co-receptor for VEGF when expressed on vascular endothelial cells, endothelial cell progenitors and monocytes. VEGF R1 is expressed primarily on endothelial cells but is also found on human peripheral blood monocytes. Through its endothelial mitogenic and hyperpermeability activities, VEGF influences a variety of immune functions related to wound healing and blood protein traffic across endothelial barriers.