Thrombus Formation Initiation and Propagation

描述（由申请方提供）：本提案的目的是确定血小板胶原蛋白受体和因子Xi在体内血栓形成中的作用。虽然止血系统的这些成分的作用已经在体外得到了很好的研究，并且人类中一些参与蛋白质的突变暗示了体内作用，但现在存在机会，使用独特的真实的时间活体显微镜技术来描绘它们在体内的重要性。将检查小鼠糖蛋白VI缺失小鼠、具有低水平糖蛋白VI的小鼠和缺乏整联蛋白α 2 β 1的小鼠的小动脉中激光诱导血栓形成的时间过程和动力学，以确定这些胶原受体在该模型中血栓形成中的作用。将检查三种小鼠基因型中血栓中血小板积聚的活化状态，以探测两种不同胶原受体在血小板响应胶原的信号传导中的作用。缺乏糖蛋白VI的小鼠和缺乏α 2整联蛋白链的小鼠似乎在血栓形成的小鼠模型中受到保护，但与缺乏糖蛋白Ib（损伤部位血小板粘附的另一种引发剂）时存在的出血表型相反，缺乏糖蛋白VI或α 2整联蛋白链的小鼠不出血。因此，这些蛋白质可能是抗血栓药物的有用靶点，从而更好地了解它们在体内血栓形成中的作用。目前的血液凝固模型是通过在血管损伤部位暴露组织因子而引发，导致产生少量因子Xa和凝血酶。在因子Xa存在下，通过该途径产生的凝血酶的量受到TFPI对因子VIIa-组织因子复合物的抑制的限制。在所形成的其它功能中，初始凝血酶激活因子Xi，然后因子XI通过因子IX的激活维持凝血酶通量。将检查因子Xi缺失小鼠中激光诱导血栓形成的时间过程和动力学，以更好地理解因子Xi在体内的作用。血液凝固复合物的分子结构的阐明仍然是理解这一过程的主要未解决的问题之一。为了补充我们对因子Xi在血栓形成中的作用的体内研究，将确定因子Xi苹果结构域和因子IX Gla结构域之间形成的复合物的结构。

DESCRIPTION (provided by applicant): The objectives of this proposal are to determine the role of platelet collagen receptors and of factor XI in thrombus formation in vivo. While the role of these components of the hemostatic system have been well studied in vitro and mutations in some of the participating proteins in humans hint at in vivo roles, the opportunity now exists, using a unique real time intravital microscopy technique, to delineate their importance in vivo. The time course and kinetics of laser induced thrombus formation in the arterioles of mice glycoprotein VI null mice, mice with low levels of glycoprotein VI and mice lacking the integrin alpha2 beta1 will be examined to determine the role of these collagen receptors in thrombus formation in this model. The activation state of the platelets accumulating in thrombi in the three mouse genotypes will be examined to probe the role of the two different collagen receptors in platelet signaling in response to collagen. Both mice lacking glycoprotein VI and mice lacking the alpha2 integrin chain appear to be protected in mouse models of thrombosis but in contrast to the bleeding phenotype present in deficiency of glycoprotein Ib, another initiator of platelet adhesion at sites of injury, mice lacking glycoprotein VI or the alpha2 integrin chain do not bleed. Thus these proteins may be useful targets for anti-thrombotic agents warranting a better understanding of their role in thrombus formation in vivo. A current model for blood coagulation is that the initiation occurs through exposure of tissue factor at sites of vascular injury resulting in the generation of small quantities of factor Xa and thrombin. The amount of thrombin generated through this pathway is limited by the inhibition of the factor Vlla-tissue factor complex by TFPI, in the presence of factor Xa. The initial thrombin among other functions formed activates factor XI which then maintains the thrombin flux through activation of factor IX. The time course and kinetics of laser induced thrombus formation in factor XI null mice will be examined to obtain a better understanding of the role of factor XI in vivo. The elucidation of the molecular architecture of blood coagulation complexes remains one of the major unresolved problems in the understanding of this process. To complement our in vivo studies of the role of factor XI in thrombus formation the structure of the complex formed between the factor XI apple domain(s)and the factor IX Gla domain will be determined.