Angiopoietin-1 / Ang-1

Angiopoietin1 (Ang1) and Angiopoietin2 (Ang2) are two closely related secreted ligands which bind with similar affinity to Tie2, a receptor tyrosine kinase with immunoglobulin and epidermal growth factor homology domains expressed primarily on endothelial cells and early hematopoietic cells. Tie2 and angiopoietins have been shown to play critical roles in embryogenic angiogenesis and in maintaining the integrity of the adult vasculature. Ang1 cDNA encodes a 498 amino acid (aa) residue precursor protein that contains a coiledcoiled domain near the aminoterminus and a fibrinogen like domain at the Cterminus. Human Ang 1 shares approximately 97% and 60% aa sequence identity with mouse Ang1 and human Ang2, respectively. Ang1 activates Tie2 signaling on endothelial cells to promote chemotaxis, cell survival, cell sprouting, vessel growth and stabilization. Ang2 has alternatively been reported to be an antagonist for Ang1 induced Tie2 signaling as well as an agonist for Tie2 signaling, depending on the cell context.