D' Angeac A.D., Stefas I., Graafland H., De Lamotte F., Rucheton M., Palais C., Eriksson A. K., Bosc P., Rose T., Chicheportiche R. (2006). Biotinylation of glycan chains in beta(2) glycoprotein I induces dimerization of the molecule and its detection by the human autoimmune anti-cardiolipin antibody EY2C9. Biochemical Journal, 393 (Part 1), p. 117-127. ISSN 0264-6021.
Titre du document
Biotinylation of glycan chains in beta(2) glycoprotein I induces dimerization of the molecule and its detection by the human autoimmune anti-cardiolipin antibody EY2C9
D' Angeac A.D., Stefas I., Graafland H., De Lamotte F., Rucheton M., Palais C., Eriksson A. K., Bosc P., Rose T., Chicheportiche R.
Source
Biochemical Journal, 2006,
393 (Part 1), p. 117-127 ISSN 0264-6021
Binding of beta(2)GPI ( beta(2) 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 anti phospholipid syndrome or systemic lupus erythematosus. We recently showed that binding of beta(2)GP1 to AnPLs was enhanced by biotinylation of its glycan chains with biotin-hydrazide. In the present study, we investigated why this chemical modification of beta(2)GPI increased both its affinity for AnPLs and its recognition by anti-cardiolipin antibodies. Electrophoretic analysis showed that: (i) high molecular mass beta(2)GPI (dimers and other oligomers) covalently coupled by imine bonds, were present in variable amounts in oxidized beta(2)GPI and in beta(2)GPI-bh (beta(2)GPI-biotin-hydrazide), but were absent in native beta(2)GPI; (ii) binding of beta(2)GPI-bh to phosphatidylserine-coated microtitre plates generated high molecular mass polymers in a time-dependent manner. Native beta(2)GPI did not polymerize in these conditions. These polymers did not bind more strongly to AnPLs than the monomer beta(2)GPI. However, in solution at 1 mu M beta(2)GPI-bh essentially appeared as a dimer as revealed by light-scattering analysis. SPR (surface plasmon resonance) analysis showed that the increased affinity of beta(2)GPI-bh for AnPL monolayers was due to a lower dissociation rate constant compared with native beta(2)GPI. Finally, the monoclonal human aCL (auto-immune anti-cardiolipin antibody) EY2C9 bound to beta(2)GPI-bh but did not bind to monomeric native and oxidized beta(2)GPI. It is likely that the dimeric quaternary structure of beta(2)GPI-bh is in fact responsible for the appearance of the epitopes targeted by the EY2C9 antibody.
