Angiopoietin-3

Mouse Angiopoietin3 (ANG3), is a secreted glycoprotein belonging to the angiopoietin family. It has the characteristic structural motifs of angiopoietins including the coiled coiled domain near the amino-terminus and a fibrinogen like domain at the C-terminus. Mouse ANG 3 cDNA encodes a 509 amino acid (aa) precursor protein with a 21 aa signal peptide. It shares 47%, 46% and 54% aa sequence identity with mouse ANG1, mouse ANG2 and human ANG4, respectively. Although the sequence homology is much higher between the human and mouse counterparts for ANG1 (97%) and ANG2 (85%), mouse ANG3 is believed to be an ortholog of human ANG4 based on chromosomal localization studies. Human ANG4 is highly expressed in lung and in cultured human umbilical vein endothelial cells (HUVECs). In contrast, mouse ANG3 is expressed in multiple mouse tissues. Human ANG4 is an agonist that can bind and activate Tie2, a receptor tyrosine kinase with immunoglobulin and epidermal growth factor homology domains expressed primarily on endothelial cells and early hematopoietic cells. Mouse ANG3 has been reported to be a Tie2 antagonist. It is likely that mouse ANG3, like ANG2, may exert agonist or antagonist activities depending on the cell context.