Investigation of Self-Nucleic Acids as a Trigger for Neuroinflammation

项目总结 模式识别受体(PRR)是先天免疫系统的重要组成部分，负责 检测入侵的病原体并激活适当的免疫反应。相当大比例的 PRR专门用于检测病毒DNA或RNA。因为DNA和RNA是生命的基本组成部分 在所有物种中，一个耐人寻味且广泛未被探索的问题出现了：PRRs能否检测到内源性(自我) DNA或RNA，以及自身核酸检测的生物学意义是什么？我在哥伦比亚大学的实验室 大学试图了解在两个动态平衡期间PRRs感知自身RNA的生物学意义 和疾病，并进一步阐明如何调节自我RNA感知以预防自身免疫疾病。 艾卡迪-古蒂埃综合征(AGS)的研究揭示了自身核酸介导的PRR的病因作用 自身免疫中的激活。AGS症状与病毒感染相似，因为患者的I型病毒水平升高 干扰素(干扰素)，当PRRs检测到病毒核酸时产生的一种强大的抗病毒细胞因子。核糖核酸的突变 编辑酶ADAR1会导致AGS。ADAR1在细胞双链RNA中引入A-to-I编辑 (DsRNAs)，先前的研究表明ADAR1缺乏导致PKR和MDA5的异常激活， 两种广为人知的PRR可以感知病毒dsRNA并触发强大的抗病毒免疫反应。这些发现 产生了在ADAR1缺乏期间，自身RNA被误认为病毒RNA，从而触发PRR的想法 激活和下游的抗病毒和炎症反应。有趣的是，AGS主要影响大脑， 在观察到I型干扰素产生增加的情况下，大多数患者会留下精神和身体上的残疾 因为脑部受损。ADAR1和许多PRR在所有细胞中普遍表达，但令人费解 为什么神经室特别容易受到失调炎症的影响。目前，基本的 使大脑易受炎症影响的分子机制尚不清楚。我们的长期目标是 定义自我RNA在引发神经炎症中的作用。我们将确定dsRNA感测PRR 促进包括神经元在内的人类神经细胞中结构性I型干扰素的表达(目标1)。那么，我们会 测定神经元中dsRNAs的丰度和亚细胞定位：动态平衡和核糖核酸 失调(目标2)。我们还将阐明ADAR1限制自身RNA的分子机制 激活神经细胞中的PRRs(目标3)。在这一应用中，我们在免疫学和RNA生物学方面积累了丰富的经验 将应用于神经生物学。我们将利用尖端的人类干细胞技术，神经细胞分化 技术和高通量基因组学，与各自领域的领先专家合作。这些研究可以 帮助识别引发大脑炎症的早期分子事件，这可能导致新的发现 治疗AGS的治疗靶点。更广泛地说，这些研究可能对炎症是如何产生的提供洞察。 在其他神经退行性疾病中，如ALS(肌萎缩侧索硬化症)或额颞痴呆 (FTD)，RNA结合蛋白剂量的扰动或扩展的RNA重复元件可导致疾病。

PROJECT SUMMARY Pattern recognition receptors (PRRs) are an essential component of the innate immune system responsible for detecting invading pathogens and activating appropriate immunological responses. A significant proportion of PRRs are specialized in detecting viral DNA or RNA. Since DNA and RNA are the basic building blocks of life across all species, an intriguing and widely unexplored question emerges: Can PRRs detect endogenous (self) DNA or RNA, and what is the biological significance of self-nucleic acid detection? My laboratory at Columbia University seeks to understand the biological significance of self-RNA sensing by PRRs during both homeostasis and disease, and to further elucidate how self-RNA sensing is regulated to prevent autoimmune disorders. Research on Aicardi-Goutières syndrome (AGS) uncovered the causal role of self-nucleic acid mediated PRR activation in autoimmunity. AGS symptoms `mimic' viral infection, as patients exhibit elevated levels of type I interferon (IFN), a potent antiviral cytokine produced when PRRs detect viral nucleic acids. Mutations in the RNA editing enzyme ADAR1 can cause AGS. ADAR1 introduces A-to-I edits in cellular double-stranded RNAs (dsRNAs), and prior studies demonstrated that ADAR1 deficiency leads to aberrant activation of PKR and MDA5, two PRRs widely known to sense viral dsRNAs and trigger potent antiviral immune responses. These findings gave rise to the idea that during ADAR1 deficiency, self-RNAs become mistaken as viral RNAs, triggering PRR activation and downstream antiviral and inflammatory responses. Intriguingly, AGS mainly affects the brain, where elevated type I IFN production is observed, and most patients are left with mental and physical disabilities due to damage to the brain. ADAR1 and many PRRs are ubiquitously expressed in all cells, but it is puzzling why the neural compartment is particularly vulnerable to dysregulated inflammation. Currently the underlying molecular mechanisms that predispose the brain to inflammation are poorly defined. Our long-term goal is to define the role of self-RNAs in triggering neuroinflammation. We will determine if dsRNA sensing PRRs contribute to constitutive type I IFN expression in human neural cells, including neurons (Aim 1). Then, we will determine the abundance and subcellular localization of dsRNAs in neurons: during homeostasis and RNA dysregulation (Aim 2). We will also elucidate the molecular mechanism by which ADAR1 restricts self-RNAs from activating PRRs in neural cells (Aim 3). In this application our rich experience in immunology and RNA biology will be applied to neurobiology. We will utilize cutting edge human stem cell technology, neural cell differentiation techniques, and high-throughput genomics in collaboration with leading experts in their field. These studies can help identify early molecular events that trigger inflammation in the brain, which may lead to discovery of new therapeutic targets to treat AGS. More broadly, these studies may provide insight into how inflammation arises in other neurodegenerative diseases such as ALS (amyotrophic lateral sclerosis) or frontotemporal dementia (FTD), where perturbation of RNA-binding protein dosage or expanded RNA repeat elements can cause disease.