Department of Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts, United States of America.
PLoS One. 2010 Dec 15;5(12):e15345. doi: 10.1371/journal.pone.0015345.
β2GPI is a major antigen for autoantibodies associated with antiphospholipid syndrome (APS), an autoimmune disease characterized by thrombosis and recurrent pregnancy loss. Only the dimeric form of β2GPI generated by anti-β2GPI antibodies is pathologically important, in contrast to monomeric β2GPI which is abundant in plasma.
We created a dimeric inhibitor, A1-A1, to selectively target β2GPI in β2GPI/antibody complexes. To make this inhibitor, we isolated the first ligand-binding module from ApoER2 (A1) and connected two A1 modules with a flexible linker. A1-A1 interferes with two pathologically important interactions in APS, the binding of β2GPI/antibody complexes with anionic phospholipids and ApoER2. We compared the efficiency of A1-A1 to monomeric A1 for inhibition of the binding of β2GPI/antibody complexes to anionic phospholipids. We tested the inhibition of β2GPI present in human serum, β2GPI purified from human plasma and the individual domain V of β2GPI. We demonstrated that when β2GPI/antibody complexes are formed, A1-A1 is much more effective than A1 in inhibition of the binding of β2GPI to cardiolipin, regardless of the source of β2GPI. Similarly, A1-A1 strongly inhibits the binding of dimerized domain V of β2GPI to cardiolipin compared to the monomeric A1 inhibitor. In the absence of anti-β2GPI antibodies, both A1-A1 and A1 only weakly inhibit the binding of pathologically inactive monomeric β2GPI to cardiolipin.
Our results suggest that the approach of using a dimeric inhibitor to block β2GPI in the pathological multivalent β2GPI/antibody complexes holds significant promise. The novel inhibitor A1-A1 may be a starting point in the development of an effective therapeutic for antiphospholipid syndrome.
β2GPI 是与抗磷脂综合征（APS）相关的自身抗体的主要抗原，APS 是一种自身免疫性疾病，其特征是血栓形成和反复妊娠丢失。只有抗β2GPI 抗体产生的二聚体形式的β2GPI 具有病理性重要性，而单体β2GPI 在血浆中含量丰富。
我们创建了一种二聚体抑制剂 A1-A1，以选择性靶向β2GPI 在β2GPI/抗体复合物中的作用。为了制造这种抑制剂，我们从 ApoER2（A1）中分离出第一个配体结合模块，并使用柔性接头将两个 A1 模块连接起来。A1-A1 干扰 APS 中两种病理性重要的相互作用，即β2GPI/抗体复合物与阴离子磷脂和 ApoER2 的结合。我们比较了 A1-A1 与单体 A1 抑制β2GPI/抗体复合物与阴离子磷脂结合的效率。我们测试了 A1-A1 抑制人血清中存在的β2GPI、从人血浆中纯化的β2GPI 以及β2GPI 的单独结构域 V 的能力。我们证明，当β2GPI/抗体复合物形成时，A1-A1 比 A1 更有效地抑制β2GPI 与心磷脂的结合，无论β2GPI 的来源如何。同样，与单体 A1 抑制剂相比，A1-A1 强烈抑制二聚化的β2GPI 结构域 V 与心磷脂的结合。在没有抗β2GPI 抗体的情况下，A1-A1 和 A1 都只能微弱抑制病理性无活性的单体β2GPI 与心磷脂的结合。
我们的结果表明，使用二聚体抑制剂阻断病理性多价β2GPI/抗体复合物中β2GPI 的方法具有很大的潜力。新型抑制剂 A1-A1 可能是开发抗磷脂综合征有效治疗方法的起点。
