The Biochemistry and Physiology of Platelet TFPI

描述（由申请方提供）：组织因子途径抑制剂（TFPI）是启动凝血的组织因子/因子Vila（TF/VIIa）催化复合物的主要抑制剂。因此，TFPI是一种有效的抗凝蛋白。血管系统内TF的量在诸如动脉粥样硬化和癌症的疾病中增加，产生血管内血栓形成，其可导致常见和严重的疾病，诸如心脏病发作、中风和肺栓塞。我们提出的研究的长期目标是了解巨核细胞产生的TFPI在控制血管内TF活性中的作用，并在活化血小板表面表达。我们假设血小板TFPI是最佳的位置和集中，以下调TF活性内不断增长的血凝块。因此，它可以防止血栓的形成，血栓完全堵塞血管并产生严重的、可能致命的疾病。该假设基于以下：1）血液中的循环TF是凝块形成和生长的主要贡献者; 2）TFPI是TF的唯一生理抑制剂; 3）血小板是凝块形成的主要细胞组分; 4）肌动蛋白和TFPI共定位在活化的血小板内;和5）缺乏血小板TFPI的小鼠在其肝和脑中具有大量的纤维蛋白沉积，这在具有血小板TFPI的小鼠中不存在。本文提出的实验将确定1）TFPI在静止血小板内的细胞内位置; 2）TFPI转移至活化血小板表面的生化机制;和3）在TFPI缺乏的体内小鼠模型中血小板TFPI的生理功能。这份建议书是一个跨越5年的职业发展计划的一部分。职业发展计划包括血液学、小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提供1）访问具有血液学，凝血和病理学领域专业知识的经验丰富的研究人员，2）小鼠模型的生产和评价，3）使用体外和体内系统研究凝血，4）通过血液研究所主办的访问系列讲座，接触到国际和国内公认的科学家。这些机会将为Maroney博士过渡到独立资助的研究者提供额外的支持和指导。 相关性（参见说明）：该提案与公共卫生相关，因为它研究了血小板TFPI在血小板凝块形成活性下调中的作用。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的理解，同时控制凝块生长以防止可能导致中风或心脏病发作或其他潜在致命疾病的血管闭塞。 (End摘要）

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)