Investigation into the mechanism of the thrombin receptor function of GPIB

描述（由申请人提供）：在美国，超过8300万成年人患有心血管疾病，使他们极易患心脏病和中风。美国33%的死亡是由心脏病和中风引起的。在许多这些病例中，潜在的原因是动脉血栓形成，其中血小板起着关键作用。血小板对血栓形成和止血至关重要。当血管受损时，循环中的血小板迅速附着在损伤部位，被激活并聚集形成原发性血栓。血小板对内皮下基质蛋白的初始粘附，特别是在高剪切速率条件下，是由血管性血液病因子（VWF）与其受体血小板糖蛋白（GP） Ib-IX-V复合物（GPIb）之间的相互作用介导的。VWF和GPIb的相互作用不仅在启动血小板粘附方面很重要，而且在传递血小板完全激活的重要信号方面也很重要。许多报道表明GPIb促进凝血酶诱导的血小板活化。然而，凝血酶与GPIb结合是如何调控的，凝血酶与GPIb结合是如何促进血小板活化的，目前尚不清楚。利用基因工程细胞表达GPIb¿和GPIb¿敲除小鼠的截短形式，我们发现GPIb与细胞内信号蛋白14-3-3的相互作用是刺激所必需的

DESCRIPTION (provided by applicant): In the United States, more than 83 million adults live with cardiovascular diseases making them highly susceptible to heart attack and stroke. 33 percent of all deaths in the U.S. are caused by heart diseases and stroke. In many of these cases the underlying cause is arterial thrombosis, in which platelets play a critical role. Plateles are essential to thrombosis and hemostasis. Upon damage of a blood vessel, circulating platelets rapidly adhere to the site of injury, become activated, and aggregate to form a primary thrombus. The initial platelet adhesion to subendothelial matrix proteins, particularly at high shear rate conditions, is mediated by the interaction between von Willebrand factor (VWF) and its receptor, the platelet glycoprotein (GP) Ib-IX-V complex (GPIb). The interaction of VWF and GPIb is not only important in initiating platelet adhesion, but also for transmitting signals important for full platelet activation. Numerous reports have implicated GPIb in promoting thrombin induced platelet activation. However, it is still unclear how thrombin binding to GPIb is regulated and how thrombin binding to GPIb promotes platelet activation. Using cells genetically engineered to express a truncated form of GPIb¿ and GPIb¿ knockout mice, we show that the interaction of GPIb with the intracellular signaling protein 14-3-3 is required for the stimulatory role of GPIb in thrombin-induced platelet activation. We believe that the binding of 14-3-3 to GPIb is required for platelets to become activated in response to low doses of thrombin. Using molecular biology in combination with bone marrow transplantation methods we will test whether deletion of this interaction prevents thrombin-induced platelet responses in mice expressing GPIb with a mutation in a critical 14-3-3 binding site. We hypothesize that the binding of 14-3-3 to GPIb plays an important stimulatory role in thrombin-induced platelet activation. The specific aims of this proposal are: 1) to determine the functional role of the 14-3 3-GPIb interaction in thrombin-induced platelet activation using platelets expressing 14-3-3 binding deficient GPIb and 2) to investigate the mechanism by which GPIb promotes the platelet response to thrombin. Ultimately understanding how thrombin signaling is regulated by the 14-3-3-GPIb interaction will lead to the development of novel drugs for the treatment of patients suffering from heart attack and stroke.