C. elegans immune defense against the P. aeruginosa toxin Exotoxin A

描述(由申请人提供)：肠道上皮细胞持续暴露于各种摄入的微生物中，必须迅速识别和防御那些致病微生物，同时忽略共生性。如果这一过程失败，它可能导致严重的和潜在的致命感染，并与包括炎症性肠病和代谢综合征在内的多种疾病有关。尽管如此，目前尚不清楚健康的上皮细胞如何识别自己受到攻击，然后能够自卫。为了回答这些问题，我们的实验室使用细小线虫来研究宿主/病原体的相互作用，这种线虫主要依靠肠道上皮免疫来防御摄入的病原体，包括革兰氏阴性细菌铜绿假单胞菌。铜绿假单胞菌是一种常见的医院内病原体，对于免疫功能低下的人，如烧伤患者、囊性纤维症患者或正在接受化疗的人来说，问题尤其严重。使用目前的抗生素很难根除铜绿假单胞菌，因此详细描述宿主细胞如何识别和响应这种病原体对于开发新的治疗策略至关重要。由于细菌入侵和宿主防御的机制在进化中是高度保守的，我使用相对简单和容易处理的线虫模型所做的发现很有可能直接适用于人类。在本申请中，我将研究线虫如何防御铜绿假单胞菌毒素外毒素A(Toxa)。Toxa是铜绿假单胞菌产生的最有效的毒素之一，它通过阻止动物细胞合成新的蛋白质来杀死它们。我之前发现，线虫通过间接检测其酶效应(翻译抑制)来识别弓形虫的存在，并通过上调免疫反应基因来做出反应。令人惊讶的是，野生型线虫在连续喂食Toxa时寿命正常，但免疫信号途径缺陷的动物，包括p38 MAP激酶途径，很快就会死亡。因此，健康的线虫动物有一种监视机制，可以感知毒素介导的翻译抑制，并迅速做出有效的反应。这项应用旨在发现识别蛋白质合成异常如何使线虫能够在弓形虫中存活，并在包括哺乳动物模型在内的其他生物体中探索这一过程。

DESCRIPTION (provided by applicant): Intestinal epithelial cells are continuously exposed to a wide variety of ingested microbes and must quickly recognize and defend against those that are pathogenic while simultaneously ignoring commensals. If this process fails, it can result in serious and potentially fatal infections and has been linked to multiple disorders including inflammatory bowel disease and metabolic syndrome. Despite this, it is unclear how healthy epithelial cells recognize that they are under attack and are then able to defend themselves. To answer these questions, our laboratory investigates host/pathogen interactions using the small worm Caenorhabditis elegans, which relies primarily on intestinal epithelial immunity to defend against ingested pathogens, including the gram-negative bacterium Pseudomonas aeruginosa. P. aeruginosa is a common nosocomial pathogen that is especially problematic for immunocompromised individuals such as burn victims and patients with cystic fibrosis or those undergoing chemotherapy. P. aeruginosa can be difficult to eradicate using current antibiotics and so detailed characterization of how host cells recognize and respond to this pathogen will be critical for the development of new treatment strategies. Since the mechanisms underlying bacterial invasion and host defense are strongly conserved in evolution, the discoveries I make using the relatively simple and tractable C. elegans model have a high likelihood of being directly applicable to humans. In this application, I will investigate how C. elegans defends against the P. aeruginosa toxin Exotoxin A (ToxA). ToxA is one of the most potent toxins produced by P. aeruginosa and kills animal cells by preventing them from synthesizing new proteins. I previously discovered that C. elegans recognizes the presence of ToxA by indirectly detecting its enzymatic effects (translational inhibition) and reacts by upregulating immune-response genes. Surprisingly, wild-type C. elegans have normal lifespan when continuously fed ToxA but animals defective in immune signaling pathways, including the p38 MAP kinase pathway, die rapidly. Thus, healthy C. elegans animals have a surveillance mechanism that can sense ToxA-mediated translational inhibition and quickly mount an effective response. This application seeks to discover how identifying protein synthesis abnormalities enable C. elegans to survive ToxA and to explore this process in other organisms, including mammalian models.