Plasminogen Activation & SK: Structure-Function

描述（由申请人提供）：心脏或大脑动脉的血栓性闭塞每年在全世界造成1270万人死亡和残疾。通过纤溶酶（一种分解纤维蛋白的酶）治疗性溶解这些血栓，减少心脏病发作和中风引起的死亡和残疾。纤溶酶由酶原纤溶酶原（Pg）通过Pg激活剂如链激酶（SK）和组织Pg激活剂（TPA）产生。纤溶酶的产生和活性受到蛋白质与抑制剂（例如，12-抗纤溶酶），底物（例如，纤维蛋白）和其它分子。更安全、更有效的血栓溶解剂将显著降低心血管疾病患者的死亡率和残疾率。我们的长期目标是帮助阐明调节P（g）系统活性的蛋白质-蛋白质相互作用，并将这些见解转化为潜在的治疗方法。在该资助的最后一个资助期内，我们帮助描绘了SK将Pg（无裂解）转化为最具催化效率的Pg激活剂的优雅相互作用。已经对以下方面进行了深入的研究：1）SK在缺乏纤维蛋白的情况下启动Pg活化的机制; 2）SK中可以被改变以产生非常有效的和纤维蛋白特异性的Pg活化剂的结构元件; 3）SK和Pg之间介导物种特异性Pg激活的分子互补性的基础，以及，4）如何在一个新的，小的，分子可以被改变以形成有效激活人Pg的复合物。来自这些研究的机制见解导致发现Pg激活剂，其通过不同于SK的机制在体外和体内以精确的特异性激活Pg。该延续提案旨在表征这些新分子并在血栓形成和中风的相关体内模型中定义其潜在的治疗特性。我们尤其力求：1）重新编程新的Pg激活剂的作用机制和纤溶潜力; 2）确定哪些新的Pg激活剂在人源化血栓形成模型中在体内显示更大的纤维蛋白特异性和纤溶效力; 3）通过确定纤维蛋白特异性Pg激活是否降低体内脑出血的风险来检查纤溶领域的中心原则。对这些独特的Pg激活机制的持续分析将进一步增强我们对P（g）系统的催化活性和特异性是如何调节的理解，并将确定这些具有定制分子修饰的新型Pg激活剂是否具有改善血栓形成患者治疗的潜力。 公共卫生相关性：阻塞血液流动的凝块是中风和心脏病发作的主要原因。找到更安全、更有效的方法来溶解血栓可以挽救数百万人的生命。我们已经发现了新的血栓溶解分子，在这个项目中，我们试图确定它们在中风模型中的有效性和安全性。

DESCRIPTION (provided by applicant): Thrombotic occlusion of the arteries of the heart or brain kills and disables 12.7 million people a year worldwide. Therapeutic dissolution of these thrombi by plasmin, an enzyme that digests fibrin, reduces death and disability from heart attacks and strokes. Plasmin is generated from the zymogen plasminogen (Pg) by Pg activators such as streptokinase (SK) and tissue Pg activator (TPA). Plasmin generation and activity is tightly regulated by protein interactions with inhibitors (e.g., 12-antiplasmin), substrates (e.g., fibrin) and other molecules. Safer and more effective agents for dissolving thrombi would markedly reduce mortality and disability in patients with cardiovascular disease. Our long term goal is to help elucidate the protein-protein interactions that regulate the activity of the P(g) system and to translate these insights into potential therapeutics. During the last funding period of this grant we have helped to delineate the elegant interactions through which SK converts Pg (without cleavage) into the most catalytically efficient Pg activator. Insights have been made into defining: 1) the mechanisms through which SK initiates Pg activation in the absence of fibrin; 2) the structural elements in SK that can be altered to produce extraordinarily potent and fibrin-specific Pg activators; 3) the basis for molecular complementarities between SK and Pg that mediates species-specific Pg activation and, 4) how a novel, small, molecule can be altered to form a complex that efficiently activates human Pg. The mechanistic insights from these studies have lead to the discovery of Pg activators that work through mechanisms different from SK to activate Pg with exquisite specificity in vitro and in vivo. This continuation proposal seeks to characterize these novel molecules and define their potential therapeutic properties in relevant in vivo models of thrombosis and stroke. In particular we seek to: 1) reprogram the mechanisms of action and the fibrinolytic potential of a new Pg activator; 2) define which novel Pg activators display greater fibrin-specificity and fibrinolytic potency in vivo in humanized thrombosis models and, 3) examine a central tenet of the fibrinolytic field by determining whether fibrin-specific Pg activation decreases the risk of cerebral hemorrhage in vivo. Continued analysis of these unique mechanisms of Pg activation will further enhance our understanding of how the catalytic activity and specificity of P(g) system is regulated and, will define whether these novel Pg activators, with tailored molecular modifications, have potential for improving the treatment for patients with thrombosis. PUBLIC HEALTH RELEVANCE: Clots that block the flow of blood are the primary causes of stroke and heart attacks. Finding safer and more effective ways to dissolve blood clots could save millions of lives. We have discovered novel clot dissolving molecules and, in this project we seek to determine how effective and safe they are in models of stroke, etc.