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，可防止对宿主组织的损伤并限制寄生虫复制。假单胞菌III型系统在急性感染中起重要作用，并且可能在慢性感染的建立中起初始作用。四种效应物或毒素，ExoS、ExoT、ExoY和ExoU，通过分泌装置直接注射到真核细胞中，并且都具有重要的特性。每个效应子是一种酶，并且每个酶需要真核辅因子或激活剂以获得最大活性。催化活性确保快速中毒和细胞生理学的改变，以有利于细菌在宿主环境中的复制和存活。细胞防御的关键要素，包括对吞噬作用和细菌破坏重要的细胞骨架组分（ExoS、ExoT、ExoY）、细胞间相互作用（ExoY）、细胞信号传导途径（ExoS、ExoT、ExoY）和膜完整性（ExoU）的失活改变了先天免疫应答，并且不仅可以帮助建立感染，而且还允许表达其他毒力因子以促进传播到其他组织。本申请建立在我们发现ExoU（磷脂酶）的作用机制和最近的数据暗示超氧化物歧化酶（SOD）作为ExoU的辅因子的基础上。重要的是，哺乳动物SOD定位于细胞内和细胞外区室。我们推测，外切磷脂酶活性的辅因子的本地化可能会控制酶的生物活性，并在细菌入侵的某些阶段促进定植或传播。了解对酶活性至关重要的元素如何共同作用以改变蛋白质，将允许合理开发抑制剂，中断严重铜绿假单胞菌感染的病理后果。重要的是，这些研究可以揭示关于辅因子，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导致对铜绿假单胞菌及其产物的炎症反应的新见解，并可能导致设计一种组合疗法，可以帮助危重患者或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.