Investigation into the mechanisms of LRP1-mediated factor VIII clearance

LRP1介导的VIII因子清除机制研究

• 批准号: 9050765
• 负责人: Patricia Young
• 金额: $ 1.59万
• 依托单位: UNIVERSITY OF MARYLAND BALTIMORE
• 依托单位国家: 美国
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-04-13 至 2016-10-09
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9050765
• 关键词: Affect; Affinity; Amino Acids; B-domain-deleted factor VIII; Binding; Binding Sites; Biological Assay; Blood Circulation; Blood Coagulation Disorders; Blood Coagulation Factor VII; Blood Pressure; Blood coagulation; Catabolism; Cell surface; Charge; Coagulation Process; Communities; Complex; Data; Dependence; Disease; Dissociation; Enzyme Precursors; Excision; Factor IXa; Factor VIII; Factor VIII Heavy Chain; Factor VIIIa; Factor Xa; Family; Frequencies; Genes; Goals; Half-Life; Health; Hematological Disease; Hemophilia A; Hemorrhage; Hepatic; Hepatocyte; Hypertension; In Vitro; Inherited; Injection of therapeutic agent; Injury; Investigation; Ionic Strengths; LDL-Receptor Related Protein 1; Length; Life; Ligands; Liver; Low Density Lipoprotein Receptor; Low-Density Lipoproteins; Lysine; Maps; Mediating; Methods; Molecular; Mus; Mutate; Mutation; Nature; Patients; Plasma; Process; Prophylactic treatment; Proteins; Recurrence; Replacement Therapy; Research; Resistance; Role; Techniques; Testing; Thrombin; Time; Treatment Protocols; United States; arthropathies; base; blocking factor; cancer procoagulant; cost; design; economic cost; experience; improved; in vivo; interest; joint injury; male; member; mutant; prevent; prophylactic; public health relevance; receptor; recombinant antihemophilic factor VIII; response; von Willebrand Factor

 DESCRIPTION (provided by applicant): Hemophilia A is a well-known inherited blood disorder that affects 1 in 5,000 males caused by a deficiency in factor VIII (fVIII), a critical blood coagulation protein. In addition to the high economic cost of Hemophilia A, this disease has a significant impact on overall health. Over time recurrent bleeds result in hemophilic arthropathy and permanent joint damage. Further, each time a hemophiliac experiences a bleeding episode, blood pressure deviates from normal and many severe hemophiliacs develop hypertension later in life. Current treatment for hemophiliacs is replacement therapy by routine injection of recombinant fVIII to arrest bleeding episodes. Replacement therapy involves lifetime injection of fVIII in response to a bleed or approximately three times a week to prevent bleeds from occurring. Although effective, current Hemophilia A treatments are difficult to maintain for many patients due to cost and frequency of injections, leading to the need for a better prophylactic treatment. In the circulation, fVIII binds tightly to a protein known as von Willebrand Factor (vWF), which protects it from rapid clearance by preventing fVIII from binding to hepatic receptors. Studies have shown that the hepatic clearance of fVIII is mediated by the low-density lipoprotein receptor-related protein (LRP1), with some contribution by the LDL receptor. Upon injury within the vasculature, fVIII is activated by thrombin, resulting in its dissociation from vF. Activated fVIII binds to enzymatically active factor IXa to trigger the final steps of the coagulaton cascade. While it is known how fVIII functions and what receptor clears it from circulation, the molecular details of its clearance are not well understood. It is particularly of interest to revea molecular mechanisms of fVIII catabolism as a more stable fVIII that can stay in circulation for extended time would improve efficiency of replacement therapy. The objectives for the current project are to define if activation of fVIII is required for efficient LRP1-mediated hepatic clearance and identify mechanisms to delay fVIII clearance. In this project, the mechanisms of fVIII clearance will be elucidated with a combination of in vitro techniques, such as binding assays, and in vivo clearance assays in mice. Successful completion of this project will provide the fVIII research community with invaluable information regarding how fVIII is cleared from the circulation. Further, fVIII clearance from circulation can be delayed by mapping bindings sites to LRP1 on fVIII to develop a recombinant fVIII that will have a longer half-life in circulation and/o soluble LRP1 fragments will be designed to block fVIII binding to LRP1. Either of these strategies may represent an improved strategy for hemophilia therapy.

 描述(申请人提供)：血友病A是一种众所周知的遗传性血液疾病，由关键的凝血蛋白(FVIII)缺乏引起，每5,000名男性中就有1人受到影响。除了血友病A的高昂经济成本外，这种疾病对整体健康也有重大影响。随着时间的推移，反复出血会导致血友病关节病和永久性关节损伤。此外，血友病患者每经历一次出血发作，血压就会偏离正常水平，许多严重的血友病患者在以后的生活中会患上高血压。目前对血友病的治疗是通过常规注射重组FVIII来阻止出血发作的替代疗法。替代疗法包括终生注射FVIII以应对出血，或大约每周三次以防止出血发生。尽管有效，但由于成本和注射频率的原因，目前的血友病A治疗方法对许多患者来说很难维持，这导致需要更好的预防性治疗。在循环中，FVIII与一种名为von Willebrand因子(VWF)的蛋白质紧密结合，vWF通过阻止FVIII与肝脏受体结合来保护它免受快速清除。研究表明，肝脏对FVIII的清除是由低密度脂蛋白受体相关蛋白(LRP1)介导的，低密度脂蛋白受体也有一定的作用。当血管内受损时，凝血酶激活FVIII，导致其与VF解离。活化的FVIII与具有酶活性的因子IXa结合，触发凝血级联反应的最后步骤。虽然已经知道FVIII是如何发挥作用的，以及什么受体将其从循环中清除，但其清除的分子细节还不是很清楚。尤其令人感兴趣的是揭示FVIII分解代谢的分子机制，因为更稳定的FVIII可以在循环中停留更长时间将提高替代治疗的效率。本项目的目标是确定是否激活FVIII是有效的LRP1介导的肝脏清除所必需的，并确定延迟FVIII清除的机制。在这个项目中，FVIII清除的机制将结合体外技术，如结合试验和小鼠体内清除试验来阐明。该项目的成功完成将为FVIII研究界提供关于FVIII如何从流通中清除的宝贵信息。此外，通过将结合位点映射到FVIII上的LRP1以开发具有更长循环半衰期的重组FVIII和/或设计可溶性LRP1片段来阻断FVIII与LRP1的结合，可以延迟FVIII从循环中的清除。这两种策略中的任何一种都可能代表血友病治疗的改进策略。