Role of rRNA-derived short non-coding RNAs in innate immune response

项目概要和摘要 微生物的感染会引起广泛的症状和疾病。持续努力了解 针对微生物感染的细胞防御系统的机制对于开发有效的预防是必不可少的 方法和治疗应用。先天免疫系统部署各种模式识别受体， 包括Toll样受体（TLR），以识别微生物的入侵并启动保护性反应。 TLR在细胞表面或细胞内区室（例如，内体和溶酶体）在各种 细胞类型，如巨噬细胞，并识别病原体相关分子模式（PAMP），如 脂多糖（LPS）和肽聚糖（PGN）。PAMP识别启动信号转导 在转录因子如NF-κ B B的激活中达到高潮的途径，导致产生 细胞因子和趋化因子来保护宿主。在转录调控之后，TLR的下游 途径涉及多个水平的调节，包括转录后步骤。在这种情况下，短期非 编码RNA（ncRNA）已经进化为关键的转录后调节因子。在各种短ncRNA中， 核糖体RNA（rRNA），称为rRNA片段（rRFs），是最丰富的一类 短的ncRNA和最近越来越多的关注，其表达和功能意义。 rRF在包括人类在内的多种生物体中组成型表达，并且它们的表达涉及免疫调节。 调节细胞周期和增殖、凋亡以及脂质和葡萄糖代谢。在人类中， 表达以性别和人群特异性方式调节，并与2型糖尿病和其他糖尿病相关。 疾病我们认为rRFs在先天免疫应答中起重要作用。在初步研究中，我们 发现rRFs的表达通过人单核细胞源性单核细胞中表面TLR的活化而上调。 巨噬细胞（HMDM）。重要的是，短的ncRNA测序数据表明， rRF不仅在HMDM中，而且在其分泌的细胞外载体（EV）中。进一步的实验 显示特异性细胞外rRF激活受体HMDM中的内体TLR以诱导细胞因子 分泌，这表明rRFs不仅仅是作为rRNAs的降解副产物积累的， 作为促进免疫反应的功能分子积累。在建议的研究中，我们会找出 TLR途径诱导的rRF在HMDM及其EV中的表达谱（Aim 1）。我们将进一步阐明 细胞外rRFs在内体TLR激活中的分子功能（Aim 2）。最后，我们将描述 结核分枝杆菌感染者和健康人血浆中rRF的表达 (Aim 3）。通过定义一类新的TLR途径诱导的rRFs并进一步确定其作用，我们的研究 将揭示一种新的rRNA参与的ncRNA途径在先天免疫反应，并可能支持未来 探索生物标志物和在微生物感染时靶向ncRNA的有效治疗应用。

Project Summary and Abstract Infection of microbes causes a wide range of symptoms and diseases. Sustained efforts to understand the mechanism of cellular defense systems against microbe infections are essential to develop effective prevention methods and therapeutic applications. The innate immune system deploys various pattern-recognition receptors, including Toll-like receptors (TLRs), to recognize the invasion of microbes and initiate protective responses. TLRs are expressed at the cell surface or intracellular compartments (e.g., endosome and lysosome) in various cell types, such as macrophages, and recognize pathogen-associated molecular patterns (PAMPs) such as lipopolysaccharide (LPS) and peptidoglycan (PGN). The PAMP recognition initiates signal transduction pathways that culminate in the activation of transcription factors such as NF-B, resulting in production of cytokines and chemokines to protect the host. Following transcriptional regulation, the downstream of TLR pathways involves regulation at multiple levels including post-transcription steps. In this context, short non- coding RNAs (ncRNAs) have evolved as key post-transcriptional regulators. Among various short ncRNA species, those from ribosomal RNAs (rRNAs), termed rRNA fragments (rRFs), are the most abundant class of short ncRNAs and have recently gained increasing attentions on their expression and functional significance. rRFs are constitutively expressed in multiple organisms including humans, and their expression is involved in regulation of cell cycle and proliferation, apoptosis, and lipid and glucose metabolism. In humans, their expression is modulated in a sex- and population-specific manner, and associated with type 2 diabetes and other diseases. We propose that rRFs play important roles in innate immune response. In preliminary studies, we found that the expression of rRFs is upregulated by the activation of surface TLR in human monocyte-derived macrophages (HMDMs). Importantly, short ncRNA sequencing data demonstrated the abundant accumulation of the rRFs not only in HMDMs but also in their secreted extracellular vehicles (EVs). Further experiments showed that a specific extracellular rRF activates endosomal TLR in the recipient HMDMs to induce cytokine secretion, suggesting that rRFs are not just accumulated as degradation by-products of rRNAs, but are accumulated as functional molecules promoting immune response. In the proposed studies, we will identify the expression profiles of TLR pathway-induced rRFs in HMDMs and their EVs (Aim 1). We will further elucidate the molecular function of extracellular rRFs in endosomal TLR activation (Aim 2). Finally, we will characterize the rRF expression in plasma samples from healthy subjects and patients infected with Mycobacterium tuberculosis (Aim 3). By defining a novel class of TLR pathway-induced rRFs and further establishing their roles, our study will reveal a novel rRNA-engaged ncRNA pathway in the innate immune response and may support the future exploration of biomarkers and efficacious therapeutic applications targeting ncRNAs upon microbe infection.