Activity of Pseudomonas Type III Toxins

描述(由申请人提供)：了解宿主和寄生虫之间的动态相互作用提供了防止对宿主组织的损害和限制寄生虫复制的机会。假单胞菌III型系统在急性感染中起重要作用，并可能在慢性感染的建立中起初始作用。EXOS、ExoT、ExoY和ExoU四种效应物或毒素通过分泌装置直接注入真核细胞，它们都具有重要的性质。每个效应器都是一种酶，每种酶都需要一个真核辅因子或激活剂才能发挥最大活性。催化活性确保了细胞生理的快速中毒和改变，从而有利于细菌在宿主环境中的复制和生存。细胞防御的关键成分失活，包括对吞噬和细菌破坏至关重要的细胞骨架成分(ExOS、ExoT、ExoY)、细胞间相互作用(ExoY)、细胞信号通路(ExOS、ExoT、ExoY)和膜完整性(ExoU)改变先天免疫反应，不仅有助于建立感染，还允许其他毒力因子的表达，促进传播到其他组织。目前的应用建立在我们对ExoU(磷脂酶)作用机制的发现和最近的数据表明超氧化物歧化酶(SOD)是ExoU的辅助因子。重要的是，哺乳动物的超氧化物歧化酶定位于细胞内和细胞外。我们推测，ExoU-磷脂酶活性的辅助因子的定位可能控制该酶的生物学活性，并在细菌入侵的特定阶段促进定植或扩散。了解酶活性的关键因素是如何共同作用改变蛋白质的，将允许合理开发抑制物，从而阻断严重的铜绿假单胞菌感染的病理后果。重要的是，这些研究可以揭示关于辅因子、细菌酶和它们的哺乳动物同源物(JPLA2、cPLA2和Patatin)之间的关系的进化见解。最后，脂质代谢和花生四烯酸的产生影响免疫功能和细胞代谢的调节。研究ExoU中毒的生物学后果可能会导致对铜绿假单胞菌及其产品的炎症反应的新见解，并可能导致设计一种治疗方法的组合，以帮助危重患者或慢性感染的早期阶段。

DESCRIPTION (provided by applicant): Understanding the dynamic interaction between host and parasite offers opportunities to prevent damage to host tissues and limit parasitic replication. The Pseudomonas type III system plays an important role in acute infections and may play an initial role in the establishment of chronic infections. Four effectors or toxins, ExoS, ExoT, ExoY and ExoU, are directly injected into eukaryotic cells by the secretion apparatus and all share important properties. Each effector is an enzyme and each enzyme requires a eukaryotic cofactor or activator for maximal activity. Catalytic activity ensures rapid intoxication and alteration of cellular physiology to benefit bacterial replication and survival in a host environment. Inactivation of key elements of cellular defenses that include cytoskeletal components important for phagocytosis and bacterial destruction (ExoS, ExoT, ExoY), intercellular interactions (ExoY), cell signaling pathways (ExoS, ExoT, ExoY) and membrane integrity (ExoU) alter the innate immune responses and can aid not only in establishing the infection but also allow expression of other virulence factors to promote dissemination to other tissues. The current application builds upon our discovery of the mechanism of action of ExoU (phospholipase) and recent data implicating superoxide dismutase (SOD) as a cofactor for ExoU. Importantly, mammalian SODs are localized to both intracellular and extracellular compartments. We postulate that the localization of the cofactor for ExoU- phospholipase activity may govern the biologic activities of the enzyme and promote either colonization or dissemination at certain stages of bacterial invasion. Understanding how the elements critical to enzymatic activity work together to alter the protein will allow rational development of inhibitors that interrupt the pathological consequences of serious P. aeruginosa infections. Importantly, these studies could reveal evolutionary insights regarding the relationships between the cofactors, bacterial enzymes and their mammalian homologs (JPLA2, cPLA2 and patatin). Finally lipid metabolism and the production of arachidonic acids effect immune function and the regulation of cellular metabolism. Investigating the biological consequences of ExoU intoxication may lead to new insights regarding the inflammatory response to P. aeruginosa and its products and may result in the design of a combination of therapeutics that could aid individuals who are critically ill or in the early stages of chronic infection.