Signaling mechanisms of platelet GPIb-IX

血小板 GPIb-IX 的信号传导机制

• 批准号: 9103211
• 负责人: Xiaoping Du
• 金额: $ 39.98万
• 依托单位: UNIVERSITY OF ILLINOIS AT CHICAGO
• 依托单位国家: 美国
• 财政年份: 2000
• 资助国家: 美国
• 起止时间: 2000-07-01 至 2018-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9103211
• 关键词: Adhesions; Agonist; Binding; Biological Assay; Biomechanics; Blood Platelets; Blood Vessels; Blood flow; Calcium; Coagulants; Coagulation Process; Collagen; Cyclic GMP; Cytoplasmic Granules; Cytoplasmic Tail; Data; Disease; Docking; Dose; Funding; Glycoprotein Ib; Grant; Health; Hemorrhage; Hemostatic function; In Vitro; Inflammatory; Injury; Integrins; Ionophores; LIM Domain Kinase 1; Mediating; Membrane; Mitogen-Activated Protein Kinases; Myocardial Infarction; Names; Phosphatidylinositols; Phosphotransferases; Physiological; Platelet Activation; Platelet Glycoprotein GPIb-IX Complex; Platelet aggregation; Play; Process; Proteinase-Activated Receptors; Research Project Grants; Role; Sepsis; Signal Pathway; Signal Transduction; Site; Stroke; Surface; Testing; Thrombin; Thrombosis; Thromboxane A2; Thrombus; Vascular Endothelium; Vesicle; base; in vivo; inhibitor/antagonist; injured; microvesicles; oligomycin sensitivity-conferring protein; prevent; receptor; receptor function; response; shear stress; von Willebrand Factor; von Willebrand factor receptor

DESCRIPTION (provided by applicant): The platelet receptor for von Willebrand factor (VWF), the glycoprotein (GP) Ib-IX-V complex (GPIb-IX), is vital for initial platelet adhesion to injured blood vessel wall, especially under shear stress. VWF binding to GPIb-IX also initiates signaling resulting in the activation of the platelet integrin aIIbb3, which mediates stable platelet adhesio, platelet aggregation, and thrombus formation. In the current funding periods, we have made significant progress in understanding the signaling mechanisms that regulates the receptor function of GPIb and VWF-induced GPIb signaling leading to platelet activation. In particular, we have demonstrated an important role for Rac1 in mediating VWF/GPIb-IX-mediated early signaling. We also demonstrated an unexpected role of a potential downstream Rac1 effector, LIM kinase 1 (LIMK1) in selectively stimulating GPIb- IX-dependent thromboxane (TX) A2 synthesis and signal amplification. GPIb-IX also interacts with thrombin, and is important in low dose thrombin-induced platelet activation. However, it is unclear whether GPIb-IX serves facilitate more efficient thrombin cleavage of protease-activated receptors (PAR), or GPIb signaling promote thrombin-induced platelet activation. Based on our preliminary data, we hypothesize that the Rac1- and LIMK1-mediated GPIb-IX signaling pathways promotes PAR-dependent platelet response to low dose thrombin. In Aim 1 of this competitive renewal application, we will investigate the role of GPIb-IX signaling in promoting thrombin-induced platelet activation and the Rac1 and LIMK1 signaling pathways that mediates VWF- and thrombin-induced GPIb-IX signaling. Activated platelets play an important role in facilitating coagulation, mainly by providing externalized phosphotidylserine (PS). However, under currently accepted assay conditions, even extremely high concentrations of physiological platelet agonists collagen and thrombin only induce a small fraction of platelets to externalize PS, the reason for this paradox remains unclear. We show that under the shear force relevant to normal blood flow, platelets do not express procoagulant activity (although the extremely high shear stress may induce platelet procoagulant MP release that requires GPIb-IX- VWF interaction). However, physiological levels of shear stress are required for agonists to efficiently induce PS externalization and MP release from platelets. Importantly, we discovered that Rac1 plays a critical role in shear-dependent platelet PS externalization and MP release induced by GPIb-independent platelet agonists. Thus, we hypothesize that activation of platelet procoagulant function requires shear force-induced signaling in which Rac1 plays an important role. Therefore, in Aim 2, we will investigate the role of shear force, Rac1 and GPIb-IX signaling in the activation of platelet procoagulant function. These study should facilitate our understanding how low concentrations of agonists thrombin or initial platelet adhesion will elicit strong platele response leading to not only platelet thrombus formation but also clotting at the site of vascular injury, and help develop new inhibitor for treating thrombotic diseases.

描述(申请人提供)：血管性血友病因子的血小板受体(VWF)，糖蛋白(GP)Ib-IX-V复合体(GPIB-IX)，对于最初的血小板与受损血管壁的黏附至关重要，特别是在剪切力下。VWF与GPIB-IX的结合也启动了导致血小板整合素aIIbb3激活的信号，该整合素aIIbb3介导了稳定的血小板黏附、血小板聚集和血栓形成。在目前的资金阶段，我们在了解调节GPIB受体功能的信号机制和VWF诱导的GPIB信号导致血小板激活方面取得了重大进展。特别是，我们已经证明了rac1在介导VWF/GPIB-IX介导的早期信号转导中的重要作用。我们还展示了一个潜在的下游rac1效应器Lim kinase1(LIMK1)在选择性刺激依赖GPIB-IX的血栓烷(TX)A2合成和信号放大方面的意外作用。GPIB-IX还与凝血酶相互作用，在小剂量凝血酶诱导的血小板激活中起重要作用。然而，目前尚不清楚GPIB-IX是否有助于更有效地切割蛋白酶激活受体(PAR)的凝血酶，或者GPIB信号是否促进凝血酶诱导的血小板激活。根据我们的初步数据，我们假设由rac1和LIMK1介导的GPIB-IX信号通路促进PAR依赖的血小板对低剂量凝血酶的反应。在这一竞争性更新应用的目标1中，我们将研究GPIB-IX信号在促进凝血酶诱导的血小板激活中的作用，以及介导VWF和凝血酶诱导的GPIB-IX信号的rac1和LIMK1信号通路。活化的血小板在促进凝血方面起着重要作用，主要是通过提供外化的磷脂酰丝氨酸(PS)。然而，在目前公认的检测条件下，即使极高浓度的生理性血小板激动剂胶原和凝血酶也只能诱导一小部分血小板外化PS，其原因尚不清楚。我们发现，在与正常血流相关的剪切力下，血小板不表现出促凝血活性(尽管极高的剪切力可能会诱导血小板促凝剂MP的释放，这需要GPIB-IX-VWF相互作用)。然而，生理水平的切应力是激动剂有效地诱导PS外化和从血小板释放MP所必需的。重要的是，我们发现rac1在非GPIB非依赖性血小板激动剂诱导的剪切依赖的血小板PS外化和MP释放中起关键作用。因此，我们假设激活血小板促凝血功能需要剪切力诱导的信号转导，而rac1在其中起着重要作用。因此，在目标2中，我们将研究剪切力、rac1和GPIB-IX信号在激活血小板促凝功能中的作用。这些研究将有助于我们了解低浓度的激动剂凝血酶或初始血小板黏附如何引发强烈的血小板反应，不仅导致血小板血栓形成，而且还会导致血管损伤部位的凝血，并有助于开发治疗血栓性疾病的新抑制剂。