Alboserpin, a Factor Xa Inhibitor from the Mosquito Vector of Yellow Fever, Binds Heparin and Membrane Phospholipids and Exhibits Antithrombotic Activity
Alboserpin, a Factor Xa Inhibitor from the Mosquito Vector of Yellow Fever, Binds Heparin and Membrane Phospholipids and Exhibits Antithrombotic Activity
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DOI：
10.1074/jbc.m111.247924
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发表时间：
2011-08-12
影响因子：
4.8
通讯作者：
Francischetti, Ivo M. B.
中科院分区：
文献类型：
--
作者：
Calvo, Eric;Mizurini, Daniella M.;Francischetti, Ivo M. B.
已表征了Alboserpin抑制因子Xa（FXa）的分子机制，Alboserpin是来自蚊子和黄热病媒介白纹伊蚊的主要唾液腺抗凝剂。Alboserpin的cDNA预测属于蛋白酶抑制剂的丝氨酸蛋白酶抑制剂家族的45-kDa蛋白。重组Alboserpin显示与FXa的化学计量、竞争性、可逆和紧密结合（皮摩尔范围）。结合是高度特异性的，并且对于FX、催化位点封闭的FXa、凝血酶和12种其他酶是不可检测的。Alboserpin显示出与肝素的高亲和力结合（K-D类似于20 nM），但在辅因子存在下未观察到FXa抑制的变化，这意味着桥接机制未发生。值得注意的是，还发现Alboserpin与磷脂酰胆碱和磷脂酰乙醇胺相互作用，但不与磷脂酰丝氨酸相互作用。此外，膜联蛋白V（在不存在Ca2+的情况下）或肝素在与磷脂囊泡结合方面胜过Alboserpin，这表明了共同的结合位点。与其活性一致，Alboserpin可在体外或离体阻断凝血酶原酶活性并增加凝血酶原时间和活化部分凝血活酶时间。此外，Alboserpin可预防颈动脉三氯化铁损伤引起的血栓形成，并以剂量依赖性方式增加出血。Alboserpin作为靶向FXa的非典型丝氨酸蛋白酶抑制剂出现，并显示出独特的磷脂特异性。可以想象，它使用肝素和磷脂酰胆碱/磷脂酰乙醇胺作为锚，以增加蛋白质定位和损伤部位、细胞活化或炎症部位的有效浓度。
The molecular mechanism of factor Xa (FXa) inhibition by Alboserpin, the major salivary gland anticoagulant from the mosquito and yellow fever vector Aedes albopictus, has been characterized. cDNA of Alboserpin predicts a 45-kDa protein that belongs to the serpin family of protease inhibitors. Recombinant Alboserpin displays stoichiometric, competitive, reversible and tight binding to FXa (picomolar range). Binding is highly specific and is not detectable for FX, catalytic site-blocked FXa, thrombin, and 12 other enzymes. Alboserpin displays high affinity binding to heparin (K-D similar to 20 nM), but no change in FXa inhibition was observed in the presence of the cofactor, implying that bridging mechanisms did not take place. Notably, Alboserpin was also found to interact with phosphatidylcholine and phosphatidylethanolamine but not with phosphatidylserine. Further, annexin V (in the absence of Ca2+) or heparin outcompetes Alboserpin for binding to phospholipid vesicles, suggesting a common binding site. Consistent with its activity, Alboserpin blocks prothrombinase activity and increases both prothrombin time and activated partial thromboplastin time in vitro or ex vivo. Furthermore, Alboserpin prevents thrombus formation provoked by ferric chloride injury of the carotid artery and increases bleeding in a dose-dependent manner. Alboserpin emerges as an atypical serpin that targets FXa and displays unique phospholipid specificity. It conceivably uses heparin and phosphatidylcholine/phosphatidylethanolamine as anchors to increase protein localization and effective concentration at sites of injury, cell activation, or inflammation.