High Affinity Binding of β2-Glycoprotein I to Human Endothelial Cells Is Mediated by Annexin II

Keying Ma, Ronit Simantov, Jing-Chuan Zhang, Roy Silverstein, Katherine A. Hajjar, Keith R. McCrae
2000 Journal of Biological Chemistry  
␤ 2 -Glycoprotein I (␤ 2 GPI) is an abundant plasma phospholipid-binding protein and an autoantigen in the antiphospholipid antibody syndrome. Binding of ␤ 2 GPI to endothelial cells targets them for activation by anti-␤ 2 GPI antibodies, which circulate and are associated with thrombosis in patients with the antiphospholipid antibody syndrome. However, the binding of ␤ 2 GPI to endothelial cells has not been characterized and is assumed to result from association of ␤ 2 GPI with membrane
more » ... olipid. Here, we characterize the binding of ␤ 2 GPI to endothelial cells and identify the ␤ 2 GPI binding site. 125 I-␤ 2 GPI bound with high affinity (K d ϳ18 nM) to human umbilical vein endothelial cells (HUVECs). Using affinity purification, we isolated ␤ 2 GPI-binding proteins of ϳ78 and ϳ36 kDa from HUVECs and EAHY.926 cells. Amino acid sequences of tryptic peptides from each of these were identical to sequences within annexin II. A role for annexin II in binding of ␤ 2 GPI to cells was confirmed by the observations that annexin II-transfected HEK 293 cells bound ϳ10-fold more 125 I-␤ 2 GPI than control cells and that anti-annexin II antibodies inhibited the binding of 125 I-␤ 2 GPI to HU-VECs by ϳ90%. Finally, surface plasmon resonance studies revealed high affinity binding between annexin II and ␤ 2 GPI. These results demonstrate that annexin II mediates the binding of ␤ 2 GPI to endothelial cells.
doi:10.1074/jbc.275.20.15541 pmid:10809787 fatcat:s6tvyu6wcbgutb77523tnh4tme