Self‐interaction of soluble and surface‐bound β2‐glycoprotein I and its enhancement by lupus anticoagulants

Abstract Antiphospholipid antibodies found in antiphospholipid syndrome are autoantibodies to phospholipid-binding proteins, such as β 2 -glycoprotein I (β 2 GPI). We have previously reported that among these antibodies, the so-called lupus anticoagulants (LAs) augment β 2 GPI binding to the phospholipid membrane surface, which is associated with the pathological action of LAs. However, the molecular mechanisms underlying this augmentation are uncertain. Here we show that β 2 GPI, which is monomeric in solution, self-interacts at the interface of soluble and surface-bound molecules. In addition, this self-interaction is enhanced by LA-positive, but not LA-negative, anti-β 2 GPI monoclonal antibodies. This study suggests that β 2 GPI self-interaction upon surface binding could be involved in the LA-induced potentiation of β 2 GPI binding to the phospholipid surface. Structured summary MINT- 6743767 : beta2GPI (uniprotkb: P02749 ) binds (MI: 0407 ) to beta2GPI (uniprotkb: P02749 ) by surface plasmon resonance (MI: 0107 ) MINT- 6743776 : beta2GPI (uniprotkb: P02749 ) binds (MI: 0407 ) to beta2GPI (uniprotkb: P02749 ) by saturation binding (MI: 0440 )