Biotinylation of glycan chains in beta2 glycoprotein I induces dimerization of the molecule and its detection by the human autoimmune anti-cardiolipin antibody EY2C9.

Binding of beta2GPI (beta2 glycoprotein I), a human plasma protein, to AnPLs (anionic phospholipids) plays a key role in the formation of antiphospholipid antibodies involved in autoimmune diseases like antiphospholipid syndrome or systemic lupus erythematosus. We recently showed that binding of beta2GPI to AnPLs was enhanced by biotinylation of its glycan chains with biotin-hydrazide. In the present study, we investigated why this chemical modification of beta2GPI increased both its affinity for AnPLs and its recognition by anti-cardiolipin antibodies.

Oxidation and biotinylation of beta 2 glycoprotein I glycan chains induce an increase in its affinity for anionic phospholipids similar to that obtained by the addition of anti-beta 2 glycoprotein I or anti-cardiolipin antibodies.

Binding of beta 2 glycoprotein I (beta2GPI) to apoptotic cells plays a key role in the opsonization of apoptotic bodies and the formation of antiphospholipids antibodies. Here, we describe the binding of beta2GPI to apoptotic cells using beta2GPI labelled with biotin-hydrazide (beta2GPI-bh) after oxidation of its glycan chains. Flow cytometry analyses and confocal microscopy showed that beta2GPI-bh, contrary to native beta(GPI, bound to apoptotic cells, either permeable or non-permeable to propidium iodide (PI), as did annexin-V-FITC.