The Biochemistry and Physiology of Platelet TFPI

描述(申请人提供)：组织因子途径抑制物(TFPI)是启动凝血的组织因子/因子V1a(Tf/V11a)催化复合体的主要抑制物。因此，TFPI是一种有效的抗凝蛋白。动脉粥样硬化和癌症等疾病会导致血管内血栓形成，从而导致常见和严重的疾病，如心脏病发作、中风和肺栓塞，血管系统内的转铁蛋白含量会增加。我们提出的研究的长期目标是了解巨核细胞产生并表达在激活的血小板表面的TFPI在控制血管内转铁蛋白活性中的作用。我们假设，血小板TFPI的最佳位置和浓度是为了下调不断增长的血栓内的TF活性。因此，它可以防止完全阻塞血管并产生严重的、可能致命的疾病的血块的形成。这一假说基于下列假设：1)血液中循环的转铁蛋白是凝块形成和生长的主要因素；2)TFPI是凝块形成的唯一生理抑制物；3)血小板是凝块形成的主要细胞成分；4)肌动蛋白和TFPI共存于激活的血小板内；5)血小板TFPI缺乏的小鼠在肝脏和大脑中有大量的纤维蛋白沉积，这在患有血小板TFPI的小鼠中是不存在的。这些实验将确定1)TFP I在静止的血小板中的细胞内定位；2)TFP I转移到激活的血小板表面的生化机制(S)；3)在体内TFP I缺乏的小鼠模型中，血小板TFP I的生理功能(S)。这项提议是一项为期5年的职业发展计划的一部分。职业发展计划包括血液学、老鼠病理学和胚胎发生学科的额外培训。与威斯康星州血液中心血液研究所(BRI)和威斯康星州医学院的基础科学家的持续互动将使他们1)接触到在血液学、凝血和病理学领域具有专业知识的经验丰富的研究人员，2)生产和评估小鼠模型，3)使用体外和体内系统研究凝血，以及4)通过血液研究所赞助的访问讲座系列接触国际和国内公认的科学家。随着马罗尼博士向独立资助的研究人员过渡，这些机会将提供额外的支持和指导。 相关性(见说明书)：这项建议与公众健康相关，因为它调查了血小板TFPI在下调血小板凝块形成活动中所起的作用。对这些机制的研究将增强我们对血小板如何形成凝块以防止严重出血，同时控制凝块增长以防止血管闭塞可能导致中风或心脏病发作或其他潜在致命疾病的理解。(摘要结束)

DESCRIPTION (provided by applicant): Tissue factor pathway inhibitor (TFPI) is the major inhibitor of the tissue factor/factor Vila (TF/Vlla) catalytic complex that initiates blood coagulation. Therefore, TFPI is a potent anticoagulant protein. The amount of TF within the vasculature system increases in diseases such as atherosclerosis and cancer producing intravascular thrombosis that can result in common and severe diseases such as heart attack, stroke and pulmonary embolism. The long term goal of our proposed studies is to understand the role of TFPI produced by megakaryocytes and expressed on the surface of activated platelets in controlling intravascular TF activity. We hypothesize that platelet TFPI is optimally located and concentrated in order to down-regulate TF activity within a growing blood clot. Thereby, it prevents the formation of blood clots that totally occlude the blood vessel and produce severe, potentially lethal, disease. This hypothesis is based on the following: 1) circulating TF in the blood is a major contributor to clot formation and growth; 2) TFPI is the only physiological inhibitor of TF; 3) platelets are the major cellular component of clot formation; 4) actin and TFPI co-localize within activated platelets; and 5) mice deficient in platelet TFPI have substantial amounts of fibrin deposition in their liver and brain that is not present in mice with platelet TFPI. The experiments proposed here will determine 1) the intracellular location of TFPI within quiescent platelets; 2) the biochemical mechanism(s) for transfer of TFPI to the surface of activated platelets; and 3) the physiological function(s) of platelet TFPI in an in vivo mouse model of TFPI deficiency. This proposal is part of a career development plan spanning 5 years. The career development plan includes additional training in the discipline of hematology, mouse pathology and embryogenesis. Continuous interactions with basic scientists at the Blood Research Institute (BRI) of the Blood Center of Wisconsin and the Medical College of Wisconsin will provide 1) access to experienced investigators with expertise in the areas of hematology, coagulation, and pathology, 2) production and evaluation of mouse models, 3) use of in vitro and in vivo systems to study coagulation, and 4) access to internationally and nationally recognized scientists through the visiting lecture series sponsored by the Blood Research Institute. These opportunities will provide additional support and mentoring as Dr. Maroney transitions to an independently funded investigator. RELEVANCE (Seeinstructions): This proposal is relevant to public health as it investigates the role platelet TFPI plays in the down-regulation of the clot forming activities of platelets. Investigation of these mechanisms will enhance our understanding of how platelets can form clots to prevent severe bleeding while controlling clot growth to prevent vessel occlusion that can result in stroke or heart attack or other potentially lethal diseases. (End of Abstract)