Description
Vascular Endothelial Growth Factor-A was originally isolated from tumor cells and referred to as Tumor Angiogenesis Factor or Vascular Permeability Factor. Although expressed at high levels in certain tumor-derived cells, it is produced by a wide variety of cell types. In addition to stimulating vascular growth and vascular permeability, it may play a role in stimulating vasolidation via nitric oxide-dependent pathways. Alternative splicing of the mRNA for VEGF-A results in several protein isoforms. Rat and bovine VEGF are one amino acid shorter than the human factor, and the bovine and human sequences show a homology of 95 percent. In contrast to other factors mitogenic for endothelial cells such as FGF-1, FGF-2 and PDGF, VEGF is synthesized as a precursor containing a typical hydrophobic secretory signal sequence of 26 amino acids. Glycosylation is not required for efficient secretion of VEGF. Recombinant human VEGF-121 produced in insect cells is a dimeric, non-glycosylated polypeptide chain of 121 amino acids and a molecular mass of 28,423 Dalton