Nervous system control of intestinal host defense mediated by TFEB

几年前，我们发现HLH-30/TFEB属于MiT转录因子家族，是C.线虫对肠道细菌感染的防御。我们还发现TFEB对于小鼠巨噬细胞的促炎性极化是重要的，因此其在先天免疫中的功能在进化上是保守的。该项目的长期目标是了解通过HLH-30/TFEB连接病原体检测，生物信号转导和宿主防御诱导的事件序列。在之前的资助期间，我们发现神经系统是外周组织中HLH-30激活所必需的。我们还发现了两个相反的机制，基因调控下游的HLH-30，介导的孤儿核受体（NR）。目前，几乎没有关于神经系统调节MiT因子介导的任何生物体中的先天免疫和炎症机制的信息。此外，这种MiT介导的防御机制在很大程度上是未知的。这些是重要的知识差距，阻碍了对体内平衡和宿主防御的基本理解，并掩盖了治疗感染或炎症性疾病的治疗机会。该项目的总体目标是阐明感觉神经元在感知细菌病原体和微生物群以激活HLH-30/TFEB以及HLH-30调节的NR中的作用。核心假设是特定细菌通过其对感觉神经回路的作用诱导胆碱能神经系统激活靶组织中的HLH-30/TFEB，从而引发由保守的孤儿核受体调节的特定宿主防御反应。为了验证这一假设，我们将定义神经系统对HLH-30/TFEB的调节，并定义TFEB下游两个NR的作用机制。这项拟议中的研究在技术上是创新的，因为在真实的时间内将单神经元和“全脑”成像应用于活的感染动物，以及在原代小鼠巨噬细胞中使用敲除策略来翻译C。elegans关于TFEB在先天免疫中功能的转录介质的发现。此外，所提出的工作在概念上是创新的，因为它暗示特定神经元作为微生物群/感染感测和与肠道的组织间通信的新机制的一部分，并且用于识别微生物群-肠-脑轴的TFEB介导机制内肠道感染和神经元变性之间的机制联系。这一建议与人类健康高度相关，因为它关注的是保守的基因和途径，并与人类疾病直接相关。这一提议在脑-肠-微生物群轴的基础知识背景下非常重要，因为它直接解决了重要的知识空白，成功完成这项工作将大大提高我们对微生物，神经和先天免疫之间相互作用的认识。这将产生重要的积极影响，因为这些知识将为广泛的感染性和炎症性疾病揭示新的宿主导向治疗机会。

A few years ago, we discovered that HLH-30/TFEB, which belongs to the MiT transcription factor family, is essential for C. elegans defense against bacterial infections in the intestine. We also discovered that TFEB is important for pro-inflammatory polarization of mouse macrophages, and thus its function in innate immunity is evolutionarily conserved. The long-term goal of this project is to understand the sequence of events linking pathogen detection, organismal signal transduction, and host defense induction via HLH-30/TFEB. In the previous funding period, we discovered that the nervous system is required for HLH-30 activation in peripheral tissues. We also uncovered two opposing mechanisms of gene regulation downstream of HLH-30, mediated by uncharacterized orphan nuclear receptors (NRs). Currently there is little information on the mechanisms by which the nervous system regulates MiT factor-mediated mechanisms of innate immunity and inflammation in any organism. Moreover, such MiT-mediated defense mechanisms are largely unknown. These are important knowledge gaps that impede fundamental understanding of homeostasis and host defense, and that conceal therapeutic opportunities to treat infections or inflammatory diseases. The overall objectives of this project are to elucidate the roles of sensory neurons in sensing bacterial pathogens and microbiota to activate HLH-30/TFEB, and of HLH-30-regulated NRs. The central hypothesis is that specific bacteria, through their action on sensory neural circuits, induce the cholinergic nervous system to activate HLH-30/TFEB in target tissues, thus eliciting a specific host defense response that is modulated by conserved orphan nuclear receptors. To test this hypothesis, we will define regulation of HLH-30/TFEB by the nervous system and define mechanisms of action for two NRs downstream of TFEB. The proposed research is technically innovative because of innovations in the application of single-neuron and “whole brain” imaging to live infected animals in real time, and in the use of knockdown strategies in primary mouse macrophages to translate the C. elegans findings on the transcriptional mediators of TFEB functions in innate immunity. Additionally, the proposed work is conceptually innovative for its implication of specific neurons as part of a novel mechanism of microbiota/infection sensing and inter-tissue communication with the intestine, and for identifying mechanistic links among intestinal infection and neuronal degeneration within a TFEB-mediated mechanism of the microbiota-gut-brain axis. This proposal is highly relevant to human health because it focuses on genes and pathways that are conserved, and directly linked to disease in humans. This proposal is highly significant in the context of fundamental knowledge of the brain-gut-microbiota axis because it directly addresses important knowledge gaps and successful completion of the work will greatly advance our knowledge about the interplay among microbes, nerves, and innate immunity. This will have an important positive impact, because such knowledge will reveal novel host-directed therapeutic opportunities for a broad range of infectious and inflammatory diseases.