Molecular Mechanisms of VWF Alteration in Vitro/Vivo

项目总结(见说明)； VWF水平降低或VWF功能缺陷导致von Willebrand病(VWD)是最常见的遗传性出血性疾病。VWF的血浆存活率降低是导致1型VWD(IC型)的一个新机制，可能占1型VWD病例的10%-15%。虽然我们的研究已经定义了IC型表型的特征成分，但对于正常或病理条件下VWF清除的机制知之甚少。我们的目标是定义VWF的清除机制。 我们已经在VWD患者的VWF编码区发现了许多新的突变。这些新的序列变异分布在VWF蛋白的所有结构域中。我们之前的表达研究表明，2A型VWD是由多种机制共同作用的结果：分泌缺陷、多聚化、调节储存或ADAMTSI 3易感性。当2A突变与野生型VWF共表达时，似乎对正常VWF加工的至少一个重要机制产生了负面影响。虽然分泌减少和血浆存活率降低被认为是导致1型VWD的机制，但1型突变对多聚化、调节存储/分泌和ADAMTSI 3介导的降解的影响尚不清楚。我们将定义导致1型VWD的机制，并开发一个模型，允许人们预测突变对VWD表型的影响。 ADAMTSI 3介导的VWF蛋白分解在2A型VWD中起着至关重要的作用。一些研究表明，ADAMTSI 3也可能与1型VWD表型有关。据报道，有一定比例的ADAMTSI 3与循环中的VWF结合，因此在IC型VWD患者中可能很快被清除。我们将确定1型VWF变异体是否增加了对ADAMTS-13蛋白降解的敏感性，并检查ADAMTSI3水平是否在IC型VWD中降低。 从这些研究中获得的知识将增加我们对引起VWD的机制的理解，从而导致更有效的治疗策略的发展

PROJECT SUMMARY (See instructions); Decreased VWF levels or defects in VWF function cause von Willebrand disease (VWD) the most common inherited bleeding disorder. The reduced plasma survival of VWF is a novel mechanism causing type 1 VWD (type IC) and may represent 10-15% of type 1 VWD cases. While our studies have defined the characteristic elements of the type IC phenotype, very little is known about the mechanisms governing VWF clearance under normal or pathological conditions. Our goal is to define VWF clearance mechanisms. We have identified many novel mutations in the VWF coding region for VWD patients. These novel sequence variations are distributed throughout all domains within the VWF protein. Our previous expression studies revealed that type 2A VWD results from a complex intersection of mechanisms: defective secretion, multimerization, regulated storage, or ADAMTSI 3 susceptibility. The 2A mutations, when co-expressed with wild-type VWF, appeared to negatively impact at least one mechanism important for normal VWF processing. While decreased secretion and reduced plasma survival have been implicated as mechanisms causing type 1 VWD, the impact of type 1 mutations on multimerization, regulated storage/secretion, and ADAMTSI 3-mediated degradation is not well-defined. We will define the mechanisms causing type 1 VWD and develop a model that would allow one to predict the impact of mutations on VWD phenotype. ADAMTSI 3-mediated proteolysis of VWF clearly plays a crucial role in type 2A VWD. Some studies have suggested that ADAMTSI 3 may also contribute to the type 1 VWD phenotype. A percentage of ADAMTSI 3 is reported to bind to circulating VWF and thus may be cleared quickly in type IC VWD patients. We will determine if type 1 VWF variants have increased susceptibility to ADAMTS-13 proteolysis and examine if ADAMTSI3 levels are reduced in type IC VWD. The knowledge gained from these studies will increase our understanding of mechanisms causing VWD, leading to the development of more effective treatment strategies