Activity of Pseudomonas Type III Toxins

描述（由申请人提供）：了解寄主和寄生虫之间的动态相互作用，为防止寄主组织损伤和限制寄生虫复制提供了机会。III型假单胞菌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、exy和ExoU四种效应器或毒素通过分泌装置直接注射到真核细胞中，它们都具有重要的特性。每种效应物都是一种酶，每种酶都需要真核辅助因子或激活因子才能发挥最大的活性。催化活性确保快速中毒和细胞生理改变，有利于细菌在宿主环境中的复制和生存。细胞防御的关键要素失活，包括对吞噬和细菌破坏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，不仅可以帮助建立感染，还可以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）的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sod定位于细胞内和细胞外隔室。我们假设ExoU-磷脂酶活性的辅因子的定位可能控制酶的生物活性，并在细菌入侵的某些阶段促进定植或传播。了解酶活性的关键因素如何共同作用以改变蛋白质，将允许合理开发抑制剂，以中断严重铜绿假单胞菌感染的病理后果。重要的是，这些研究可以揭示辅助因子、细菌酶及其哺乳动物同源物（JPLA2、cPLA2和patatin）之间关系的进化见解。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对铜绿假单胞菌及其产物的炎症反应产生新的见解，并可能导致设计一种联合治疗方法，可以帮助危重患者或处于慢性感染早期阶段的患者。

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.