FACTOR XI PHYSIOLOGY AND MOLECULAR BIOLOGY

描述：凝血因子XI是血管紧张素转换酶的内在途径的关键组成部分。 凝结。该蛋白在纤维蛋白形成中的作用 很好地描述了体外接触激活；然而，其机制 在体内负责因子XI的激活以及该蛋白在 正常止血和病理性凝血尚不清楚。在当前 在止血模型中，正常凝血是由因子启动的 VIIa/组织因子复合体，而不是通过接触激活。第XI因子 将在这些机制中发挥作用，通过激活因子维持凝血 通过凝血因子VIIa/组织因子初步形成凝血酶后。这个 在没有接触激活的情况下激活因子XI的蛋白酶 活体尚不清楚，但凝血酶已被证明能激活因子XI 体外血浆系统。这项提案的目标是评估 酶原因子XI成为活性丝氨酸蛋白酶的机制和 探讨凝血因子XI在正常止血中的作用。我们有 表达和纯化嵌合重组因子XI分子 域已被相关中的相应域替换 蛋白酶激肽释放酶原。这些蛋白质已被用来识别结合 已知能激活因子XI的蛋白水解酶的位置。它的作用机制 凝血因子XI在最近发展的纤维蛋白模型中的激活和作用 还将研究血栓对纤溶的抵抗力。最终，要完全 了解凝血因子XI对凝血的贡献，动物实验 将是必需的。同源重组技术在小鼠体内的应用 胚胎干细胞，一种因子XI缺乏的小鼠模型 在我们实验室创造的。这些动物将被用来评估角色 凝血因子XI在原发止血和出血中的作用 纤溶激活剂、抗血小板药物和抗凝剂。这个 研究将大大增加我们对凝血因子XI生物化学的了解 和生理学，并提供了一个更坚实的知识基础来研究 这种蛋白质对血栓栓塞性疾病的贡献。

DESCRIPTION: Factor XI is a key component of the intrinsic pathway of coagulation. The functions of this protein in fibrin formation initiated by contact activation in vitro are well described; however, the mechanisms responsible for factor XI activation in vivo and the role of this protein in normal hemostasis and pathologic coagulation are not clear. In current models of hemostasis, normal coagulation is initiated by the factor VIIa/tissue factor complex, and not through contact activation. Factor XI would function in these schemes to sustain coagulation by activating factor IX, after initial thrombin formation through factor VIIa/tissue factor. The protease that activates factor XI in the absence of contact activation in vivo is not known, but thrombin has been demonstrated to activate factor XI in vitro plasma systems. The goals of this proposal are to evaluate the mechanisms by which zymogen factor XI becomes an active serine protease and to investigate the contributions of factor XI to normal hemostasis. We have expressed and purified chimeric recombinant factor XI molecules in which domains have been replaced with corresponding domains from the related protease prekallikrein. These proteins have been used to identify binding sites for the proteases known to activate factor XI. The mechanism of activation and role of factor XI in a recently developed model of fibrin clot resistance to fibrinolysis will also be studied. Ultimately, to fully understand the contributions of factor XI to coagulation, studies in animals will be required. Using the technique of homologous recombination in murine embryonic stem cells, a murine model of factor XI deficiency has been created in our laboratory. These animals will be used to evaluate the role of factor XI in primary hemostasis and in bleeding in the presence of activators of fibrinolysis, anti-platelet agents, and anticoagulants. The studies will substantially increase our knowledge of factor XI biochemistry and physiology and provide a firmer knowledge base from which to study the contribution of this protein to thromboembolic diseases.