FACTOR XI PHYSIOLOGY AND MOLECULAR BIOLOGY

描述：因子Xi是内源性代谢途径的关键组分， 凝血 这种蛋白质在纤维蛋白形成中的功能是由 体外接触活化得到了很好的描述;然而， 负责体内因子Xi活化和该蛋白在 正常止血与病理性凝血不清。 当前 在止血模型中，正常凝血是由因子 VIIa/组织因子复合物，而不是通过接触激活。 因子Xi 将在这些方案中起作用，以通过激活因子 IX，通过因子VIIa/组织因子初始凝血酶形成后。 的 一种蛋白酶，其在无接触活化的情况下活化因子Xi， 目前还不清楚体内的情况，但已证实凝血酶可激活因子Xi 体外血浆系统。 本提案的目标是评估 酶原因子Xi成为活性丝氨酸蛋白酶的机制， 研究因子Xi对正常止血的贡献。 我们有 表达和纯化的嵌合重组因子Xi分子，其中 域已替换为相关的 蛋白酶前激肽释放酶 这些蛋白质已被用于鉴定结合 已知激活因子Xi的蛋白酶的位点。 的机理 最近开发的纤维蛋白模型中因子Xi的活化和作用 还将研究凝块对纤维蛋白溶解的抗性。 最后，为了充分 了解因子Xi对凝血的作用，动物研究 将被要求。 利用同源重组技术， 胚胎干细胞，一种因子Xi缺乏的小鼠模型， 在我们的实验室里创造的。 这些动物将被用来评估 因子Xi在原发性止血和出血中的作用 纤维蛋白溶解激活剂、抗血小板剂和抗凝剂。 的 研究将大大增加我们对因子Xi生物化学的了解 和生理学，并提供一个坚实的知识基础，从研究 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.