Ultralarge multimers of von Willebrand factor form spontaneous high-strength bonds with the platelet glycoprotein Ib-IX complex:: studies using optical tweezers
Ultralarge multimers of von Willebrand factor form spontaneous high-strength bonds with the platelet glycoprotein Ib-IX complex:: studies using optical tweezers
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DOI：
10.1182/blood-2001-11-0060
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发表时间：
2002-06-01
期刊：
影响因子：
20.3
通讯作者：
López, JA
中科院分区：
文献类型：
--
作者：
Arya, M;Anvari, B;López, JA
超大型血管性血友病因子（ULVWF）多聚体与灾难性微血管病性疾病血栓性血小板减少性紫癜的发病机制有关。自发的ULVWF与血小板的结合归因于由于每个分子的血小板结合位点（All结构域）的数量大大增加而增加的亲合力。为了阐明ULVWF与血小板结合增强的机制，我们使用光镊研究了血浆VWF、ULVWF和分离的A1结构域的糖蛋白Ib-IX（GP Ib-IX）复合物的解结合力。解结合力定义为将配体包被的珠拉离其与表达GP Ib-IX的细胞的附着所需的最小力。涂有血浆VWF的珠粒不能自发地与细胞结合，需要调节剂利托那肽或肉毒素。取决于形成的键的数量，破坏利托那韦和肉毒杆菌素诱导的血浆VWF-GP Ib-IX键所需的力分别以6.5pN和8.8pN的整数倍发生。相比之下，包被有ULVWF或A1结构域的珠粒在不存在调节剂的情况下结合细胞，两者的结合强度均为约11.4 pN的整数倍。因此，在不存在剪切应力的情况下，ULVWF多聚体与GIP Ib-IX形成自发的高强度键，而血浆VWF需要外源性调节剂。与GP Ib-IX形成的单个键的强度对于ULVWF和分离的A1结构域是相似的，并且大于由任一调节剂诱导的血浆VWF的强度。因此，我们认为ULVWF多聚体的构象状态比它们与血小板相互作用的大小更重要。(C)2002年，美国血液学会。
Ultralarge von Willebrand factor (ULVWF) multimers have been implicated in the pathogenesis of the catastrophic microangiopathic disorder, thrombotic thrombocytopenic purpura. Spontaneous ULVWF binding to platelets has been ascribed to increased avidity due to the greatly increased number of binding sites for platelets (the All domain) per molecule. To address the mechanism of enhanced ULVWF binding to platelets, we used optical tweezers to study the unbinding forces from the glycoprotein Ib-IX (GP Ib-IX) complex of plasma VWF, ULVWF, and isolated A1 domain. The unbinding force was defined as the minimum force required to pull ligand-coated beads away from their attachment with GP Ib-IX-expressing cells. Beads coated with plasma VWF did not bind to the cells spontaneously, requiring the modulators ristocetin or botrocetin. The force required to break the ristocetin- and botrocetin-induced plasma VWF-GP Ib-IX bonds occurred in integer multiples of 6.5 pN and 8.8 pN, respectively, depending on the number of bonds formed. In contrast, beads coated with either ULVWF or A1 domain bound the cells in the absence of modulators, with bond strengths in integer multiples of approximately 11.4 pN for both. Thus, in the absence of shear stress, ULVWF multimers form spontaneous high-strength bonds with GIP Ib-IX, while plasma VWF requires exogenous modulators. The strength of individual bonds formed with GP Ib-IX was similar for both ULVWF and the isolated A1 domain and greater than those of plasma VWF induced by either modulator. Therefore, we suggest that the conformational state of ULVWF multimers is more critical than their size for interaction with platelets. (C) 2002 by The American Society of Hematology.