Abstract
β2-glycoprotein I (β 2GPI) is a glycoprotein of unknown physiological function. It is the main target antigen for antiphospholipid antibodies in patients with antiphospholipid syndrome (APS). β 2GPI binds with high affinity to the atherogenic lipoprotein Lp(a) which shares structural homology with plasminogen, a key molecule in the fibrinolytic system. Impaired fibrinolysis has been described in APS. The present work reports the interaction between β 2GPI and Glu-Plasminogen which may explain the recently described proteolytic effect of plasmin on β 2GPI. In the process of Glu-Plasminogen activation, we found an increase in plasmin generation both at fibrin and cellular surface level as a function of the concentration of β 2GPI added, suggesting an important role as a cofactor in the trimolecular complex β 2GPI-Plasminogen-tPA. This phenomenon represents a novel regulatory step both in the positive feedback mechanism for extrinsic fibrinolysis and in antithrombotic regulation. IgG anti-β 2GPI antibodies recognized the β 2GPI at the endothelial surface inducing its activation with an increase of ICAM-I and a decrease in the expression of thrombomodulin favoring a pro-thrombotic state in the vascular endothelium. The interference in the plasmin conversion by anti-β 2GPI antibodies could generate thrombosis as observed in APS.
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Schedule a callMore From: Biochimica et Biophysica Acta (BBA) - Proteins and Proteomics
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