Structure and Function of Platelet Glycoprotein lb-IX-V Complex

血小板膜糖蛋白(GP)Ib-IX-V复合体介导血小板与受损血管壁的初始黏附 传导信号以诱导血小板活化和聚集。这种多亚单位受体的功能障碍 复合体会导致严重出血，并可能导致许多心血管疾病。尽管几十年来 深入的研究，对复杂功能的调节尚不清楚，也不清楚血小板- 激活信号是由复合体介导的。我们假设亚基之间的相互作用对 复合体的功能和调控。由于该建筑群的三维组织尚不清楚 亚基之间的相互作用在很大程度上还没有被探索，作为检验我们的假设的必要前奏。 该项目旨在确定和描述GP Ib-IX-V复合体中亚单位间的相互作用。具体而言 目的1，我们提出了跨膜结构域在亚基间起重要作用的假设 缔合，因此对于GP Ib-IX-V复合体的表达和组装是重要的。这些研究是 根据我们的观察，将GP Iba或Lb(3个亚基)的跨膜区替换为 非相关序列显著降低了复杂表达水平。的结构和功能作用 跨膜结构域中的特定残基，包括极性残基和膜-近端二硫化物- 形成半胱氨酸残基，将被定义。GP Ib-IX亚基化学计量学的分子基础 V复合体也将被阐明。在具体目标2中，我们将定义界面区域和残基 在复合体的胞外结构域之间，并探讨它们对复合体组装和 功能。这些研究是基于我们的观察结果：第一，GP IBP和IX的胞外区 亚基之间相互联系和稳定，第二，糖钙素，GP的可溶性胞外区 IBA直接与重组的GP IX胞外区结合。总体而言，对个人的仔细剖析 分离蛋白、转基因哺乳动物细胞和血小板之间的相互作用将使我们能够 开发专门干扰感兴趣的亚基间相互作用的工具和试剂，并将为 研究GP Ib-IX-V复合体中可能的结构变化响应配体结合或 细胞内调节信号。该项目还将为研究两国的相互作用提供一个垫脚石。 GP Ib-IX-V与其他受体的复合体，可能导致新的治疗策略来对抗各种 与复杂相关的血液疾病和疾病。 与公众健康相关：血小板中的糖蛋白Ib-IX-V复合体有助于血液正常凝结。 这一复合体的故障会导致严重出血，并可能导致许多心血管疾病。 该项目旨在了解Ib-IX-V复合体的结构并了解其如何发挥作用。

Platelet glycoprotein (GP) Ib-IX-V complex mediates initial platelet adhesion to the injured vessel wall and transduces signals to induce platelet activation and aggregation. Malfunction of this multi-subunit receptor complex leads to severe bleeding and can contribute to many cardiovascular diseases. Despite decades of intensive study, regulation of the complex function is not clear, nor is the process by which the platelet- activating signal is mediated by the complex. We hypothesize that inter-subunit interactions are important to the functions and regulation of the complex. Since the 3-dimensional organization of the complex is unknown and inter-subunit interactions are largely unexplored, as a necessary prelude to test our hypothesis this project seeks to identify and characterize the inter-subunit interactions in the GP Ib-IX-V complex. In Specific Aim 1, we propose to test the hypothesis that the transmembrane domains play vital roles in inter-subunit associations and thus are important for expression and assembly of the GP Ib-IX-V complex. The studies are based on our observation that replacing the transmembrane domain of GP Iba or lb(3 subunit with an unrelated sequence decreases significantly the complex expression level. Structural and functional roles of specific residues in the transmembrane domains, including polar residues and membrane-proximal disulfide- forming cysteine residues, will be defined. The molecular basis for the subunit stoichiometry in the GP Ib-IX- V complex will also be elucidated. In Specific Aim 2, we will define the interfacial regions and residues among the extracellular domains of the complex and explore their contribution to complex assembly and function. The studies are based on our observations that first, the extracellular domains of GP Ibp and IX subunits associate and stabilize each other, and second, glycocalicin, the soluble extracellular domain of GP Iba, binds directly to the recombinant extracellular domain of GP IX. Overall, careful dissection of individual interactions in the isolated proteins, in the transfected mammalian cells and in the platelets will enable us to develop tools and reagents that specifically perturb the inter-subunit interaction of interest and will pave the way for studies of the likely structural changes in the GP Ib-IX-V complex in response to ligand binding or intracellular regulatory signals. This project will also provide a stepping stone for studies on the interaction of the GP Ib-IX-V complex with other receptors and may lead to novel therapeutic strategies to combat various complex-related hematological disorders and diseases. Relevance to public health: The glycoprotein Ib-IX-V complex in the platelet helps the blood to clot properly. Malfunction of this complex leads to severe bleeding and can contribute to many cardiovascular diseases. This project seeks to understand the structure of the Ib-IX-V complex and to learn how it functions.