Pathogen sensing by nuclear hormone receptors in C. elegans intestinal epithelial cells

项目摘要/摘要 肠道上皮细胞的病原体感知和免疫效应器诱导的机制尚不清楚 完全理解。病原体感知和免疫动态平衡机制的破坏 肠道上皮细胞可导致生物失调和炎症，以及对细菌感染的易感性。 对肠道上皮细胞免疫和宿主-病原体相互作用的关键见解已经使用 线虫线虫。线虫通过保守的方式建立对细菌感染的先天性免疫防御 免疫途径，但病原体检测的机制在这种生物中是未知的。在线虫中， 与其他后生动物相比，核激素受体(NHR)家族已经显著扩大。 NHR是配体门控的转录因子，可以感应内源和外源信号来诱导适应性 转录反应。线虫基因组编码274个NHR，其中260个是人类的同源物 HNF4α。HNF4α是炎症性肠病中的一个关键的非霍奇金受体。 HNF4α在人类炎症性肠病中的作用尚不清楚。这项提议的中心假设是 线虫HNF4α同源物是一个古老的病原体传感器家族，其进化扩展在 线虫是由它们在检测不同病原体方面的功能驱动的。以下主要发现支持这一点 假设：(I)核激素受体，nhr-86/hnf4α，感知细胞环境并激活 线虫的肠道免疫防御；(Ii)NHR-86/HNF4α是病原菌抵抗和免疫所必需的 对革兰氏阳性人类病原体粪肠球菌的反应；和(Iii)一种不同的线虫HNF4α 针对革兰氏阴性病原菌的病原体防御和免疫效应调节需要同源基因 铜绿假单胞菌。在这项提案中，目标1将定义线虫NHR-86/HNF4α在病原体检测中的作用 在粪肠球菌感染过程中使用转录组学、芯片和免疫效应器相结合的方法诱导免疫效应。 测序、组织特异性抢救和基因上位性。目标2将描述单独的C的功能。 线虫HNF4α同源基因在铜绿假单胞菌感染病原菌检测中的应用该方法包括： 转录学、全球NHR结合位点鉴定、组织特异性拯救和铜绿假单胞菌遗传学。 总而言之，这些研究将描述一种全新的免疫激活范式，它将 解决线虫中如何感知病原体的一个主要难题。这些调查结果还将建立国家人权机构 作为进化上古老的病原体传感器。最终，人们的期望是，对这一点的详细剖析 HNF4α在哺乳动物病原体感知和炎症性肠炎中的作用机制 疾病。

PROJECT SUMMARY/ABSTRACT The mechanisms of pathogen sensing and immune effector induction in intestinal epithelial cells are not completely understood. Disruption in the mechanisms of pathogen sensing and immune homeostasis in intestinal epithelial cells can lead to dysbiosis and inflammation, as well as susceptibility to bacterial infection. Key insights into intestinal epithelial cell immunity and host-pathogen interactions have been made using the nematode C. elegans. Nematodes mount innate immune defenses against bacterial infection via conserved immune pathways, but the mechanisms of pathogen detection are unknown in this organism. In nematodes, the family of nuclear hormone receptors (NHRs) has dramatically expanded compared to other metazoans. NHRs are ligand-gated transcription factors that sense endogenous and exogenous signals to induce adaptive transcriptional responses. The C. elegans genome encodes 274 NHRs, of which 260 are homologs of human HNF4α. HNF4α is a key NHR involved in inflammatory bowel disease, though the mechanism through which HNF4α mediates inflammatory bowel disease in humans is unknown. The central hypothesis of this proposal is that C. elegans HNF4α homologs are an ancient family of pathogen sensors whose evolutionary expansion in C. elegans was driven by their function in detecting diverse pathogens. The following key findings support this hypothesis: (i) The nuclear hormone receptor, NHR-86/HNF4α, senses the cellular environment and activates C. elegans intestinal immune defenses; (ii) NHR-86/HNF4α is required for pathogen resistance and immune response towards the gram positive human pathogen E. faecalis; and (iii) A different C. elegans HNF4α homolog is required for pathogen defense and immune effector regulation against the gram negative pathogen P. aeruginosa. In this proposal, Aim 1 will define the role of C. elegans NHR-86/HNF4α in pathogen detection and immune effector induction during E. faecalis infection using a combination of transcriptomics, ChIP- sequencing, tissue-specific rescue and genetic epistasis. Aim 2 will characterize the function of a separate C. elegans HNF4α homolog in pathogen sensing during P. aeruginosa infection. The approach includes: transcriptomics, global NHR binding site identification, tissue specific rescue, and P. aeruginosa genetics. Collectively, these studies will characterize a fundamentally new paradigm of immune activation, which will solve a major conundrum of how pathogens are sensed in C. elegans. These findings will also establish NHRs as evolutionarily ancient pathogen sensors. Ultimately, the expectation is that detailed dissection of this mechanism will shed light on the role of HNF4α in mammalian pathogen sensing and inflammatory bowel disease.