Thrombus Formation Initiation and Propagation

描述(申请人提供)：本提案的目的是确定血小板胶原受体和凝血因子XI在体内血栓形成中的作用。虽然止血系统中这些成分的作用在体外已经得到了很好的研究，而且一些参与蛋白在人类体内的突变暗示了体内的作用，但现在有机会使用一种独特的实时活体显微镜技术来描述它们在体内的重要性。在此模型中，我们将观察小鼠糖蛋白VI缺失小鼠、低水平糖蛋白VI小鼠和整合素α2β1缺失小鼠的微动脉内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血栓形成中的作用。我们将检测三种不同类型的小鼠血栓中聚集的血小板的激活状态，以探讨这两种不同的胶原受体在血小板对胶原的反应信号中所起的作用。在血栓形成的小鼠模型中，缺乏糖蛋白VI的小鼠和缺乏α2整合素链的小鼠似乎都受到保护，但与缺乏糖蛋白Ib的出血表型相反，缺乏糖蛋白VI或α2整合素链的小鼠不出血。因此，这些蛋白质可能是抗血栓药物的有用靶点，从而保证更好地了解它们在体内血栓形成中的作用。目前的一种凝血模型是通过在血管损伤部位暴露组织因子而启动凝血，导致少量凝血因子Xa和凝血酶的产生。在凝血因子Xa存在的情况下，通过这一途径产生的凝血酶的量受到TFPI抑制因子V11a-组织因子复合体的抑制。在形成的其他功能中，最初的凝血酶激活了凝血因子XI，然后通过激活凝血因子IX维持凝血酶流量。为了更好地了解凝血因子XI在体内的作用，我们将研究激光诱导凝血因子XI缺失小鼠血栓形成的时间进程和动力学。阐明凝血复合体的分子结构仍然是理解这一过程的主要未解决问题之一。为了补充我们对凝血因子XI在血栓形成中作用的体内研究，将确定凝血因子XI苹果结构域(S)和凝血因子IX GLA结构域之间形成的复合体的结构。

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.