The Biology of VWF Self-Association

 描述（由申请方提供）：血管性血友病因子（VWF）是血浆中的一种多聚体糖蛋白，通过介导血小板与血管损伤部位结合在止血中发挥重要作用。 在最近的研究中，VWF也与微血管功能障碍和闭塞有关，部分原因是它具有独特的能力，能够在流体动力学（包括剪切应力和伸长流动）的作用下选择性结合并形成附着在内皮表面的巨大尺寸的超粘附链。当这些链不被血浆中的金属蛋白酶ADAMTS 13去除时，它们有效地结合血小板，并且VWF-血小板血栓的积累导致血管闭塞、组织梗死和器官功能障碍。我们最近发现，高密度脂蛋白（HDL）是血浆中一种众所周知的心脏保护性脂蛋白，其主要成分载脂蛋白（Apo）A-I可以减弱VWF自身结合的程度，并最终降低血管系统血栓并发症的严重程度。 这些研究揭示了HDL/ApoA-I的新的抗血栓性质，我们假设这在以微血管闭塞为特征的疾病中非常重要。 在本申请中，我们将重点关注VWF自缔合的机制，VWF如何与HDL/ApoA-I相互作用，以及HDL-VWF相互作用的生理影响。 在特定目标1中，我们将通过肽图谱和使用VWF变体来鉴定流体动力学作用下暴露的VWF自结合位点。 在具体目标2中，我们将确定剪切应力下VWF自身缔合对ADAMTS 13介导的裂解的影响，并评估HDL在ADAMTS 13介导的VWF裂解中的作用。 在具体目标3中，我们将在TTP和脓毒症的小鼠模型中评估结果和疾病参数是否因HDL缺乏而恶化或因HDL治疗而改善。 这些目标的成功完成将使人们更好地理解VWF自缔合的基本机制，如何调节这一过程，以及如何利用这些信息开发新的方法来治疗由VWF自缔合失调引起的全身性疾病。

 DESCRIPTION (provided by applicant): von Willebrand factor (VWF) is a multimeric glycoprotein in plasma that plays an important role in hemostasis by mediating platelet binding to sites of vascular injury. In recent studies, VWF has also been implicated in microvascular dysfunction and occlusion, in part because of its unique ability to sel�associate and form hyper-adhesive strands of enormous sizes attached to the endothelial surface in response to hydrodynamic forces, including shear stress and elongation flow. When these strands are not removed by the metalloprotease ADAMTS13 in plasma, they bind platelets efficiently, and the accumulation of VWF‐platelet thrombi leads to vessel occlusion, tissue infarction, and organ dysfunction. We recently discovered that high density lipoprotein (HDL), a well‐known cardioprotective lipoprotein in plasma, and its major component protein apolipoprotein (Apo)A‐I, can attenuate the extent of VWF self‐association, and ultimately the severity of thrombotic complications in the vasculature. These studies unveiled a novel antithrombotic property of HDL/ApoA‐I, which we hypothesize is very important in diseases characterized by microvascular occlusion. In this application, we will focus on the mechanism of VWF self‐association, how VWF interacts with HDL/ApoA‐I, and the physiologic impact of the HDL-VWF interaction. In Specific Aim 1, we will identify the VWF self‐ association site exposed by hydrodynamic forces by peptide mapping and use of VWF variants. In Specific Aim 2, we will determine the effect of VWF self‐association on ADAMTS13‐mediated cleavage under shear stress, and assess the role of HDL in ADAMTS13‐mediated cleavage of VWF. In Specific Aim 3, we will evaluate in mouse models of TTP and sepsis whether the outcome and disease parameters are worsened by HDL deficiency or improved by HDL treatment. Successful completion of these aims will provide an improved understanding of the basic mechanism of VWF self‐association, how this process can be regulated, and how this information can be used to develop new approaches to treat systemic diseases caused by dysregulation of VWF self‐association.