Plasminogen Activation & SK: Structure-Function

描述（由申请人提供）：心脏或大脑动脉血栓性闭塞每年导致全球1270万人死亡和残疾。溶栓酶是一种消化纤维蛋白的酶，治疗性地溶解这些血栓可以减少心脏病发作和中风造成的死亡和残疾。纤溶酶是由纤溶酶原（Pg）由Pg激活剂如链激酶（SK）和组织Pg激活剂（TPA）产生的。纤溶酶的产生和活性受到蛋白质与抑制剂（如12-抗纤溶酶）、底物（如纤维蛋白）和其他分子的相互作用的严格调节。更安全、更有效的溶栓药物将显著降低心血管疾病患者的死亡率和致残率。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。在这项资助的最后一个资助期间，我们帮助描述了通过SK将Pg（无裂解）转化为催化效率最高的Pg活化剂的优雅相互作用。见解已经被定义为：1)通过SK启动Pg激活在缺乏纤维蛋白的机制；2) SK中的结构元件可以改变以产生非常有效的纤维蛋白特异性Pg激活剂；3)介导物种特异性Pg激活的SK和Pg之间的分子互补基础；4)如何改变一个新的小分子，形成一个有效激活人类Pg的复合物。这些研究的机制见解导致Pg激活剂的发现，通过不同于SK的机制，在体外和体内以精细的特异性激活Pg。本续提案旨在表征这些新分子，并确定其在血栓和中风相关体内模型中的潜在治疗特性。我们特别寻求：1)重新编程一种新的Pg激活剂的作用机制和纤溶潜力；2)确定哪些新型Pg激活剂在人源化血栓模型中表现出更高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激活是否能降低体内脑出血的风险，来检验纤溶领域的一个核心原则。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被调节的理解，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患者治疗的潜力。公共卫生相关性：阻塞血液流动的血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凝块可以挽救数百万人的生命。我们已经发现了新的凝块溶解分子，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.