The role of mitochondrial reactive oxygen species in innate immune signaling

描述（由申请人提供）：人体防御传染病的重要组成部分是先天免疫系统。巨噬细胞和其他组成该系统的白细胞是感染的第一反应者，识别入侵的病原体并启动免疫反应。这种反应的一个中心特征是宿主炎症介质和I型干扰素（ifn）的上调和分泌。病原识别与I型干扰素产生之间的分子基础尚不清楚，但依赖于线粒体和内质网定位的适配蛋白，干扰素基因刺激因子（STING）。该研究的目的是表征sting依赖性信号通路的激活，以进一步实现描述巨噬细胞胞内感染过程中I型ifn如何被调节的长期目标。某些细胞内病原体调节宿主线粒体的功能。据推测，巨噬细胞的细胞内感染导致线粒体失调，促使活性氧（ROS）的产生，激活sting依赖的先天免疫途径，导致I型IFN， IFN-¿的表达。小分子5,6-二甲基黄酮-4-乙酸（DMXAA）是巨噬细胞中sting依赖性信号的有效激活剂，将被用作细胞内感染的替代品。此外，在细胞内细菌（土拉弗朗西斯菌）或病毒（呼吸道合胞病毒（RSV））感染时，将检测巨噬细胞中sting依赖性激活。本研究的第一个目的是确定线粒体ROS生成是否足以实现STING二聚化和下游信号成分的激活，并确定在感染或化学治疗期间线粒体ROS生成对IFN-¿表达的必要性。第二个目标将确定感染或DMXAA治疗如何调节线粒体功能和线粒体ROS。据预测，在DMXAA治疗或土拉菌或RSV感染过程中产生的线粒体ROS对于激活STING依赖的先天免疫信号通路是必要的，因为STING依赖于ROS二聚化。由于线粒体颠覆在传染病中的潜在共性，本项目所表征的机制可能在其他感染性生物体中具有广泛的应用。

DESCRIPTION (provided by applicant): An essential component of the body's defense against infectious disease is the innate immune system. Macrophages and other white blood cells that comprise this system are the first responders to infection and recognize invading pathogens and initiate an immune response. A central feature of this response is the up- regulation and secretion of host inflammatory mediators and Type I Interferons (IFNs). The molecular basis connecting pathogen recognition to Type I IFN production is unclear, but is dependent upon the mitochondrial- and endoplasmic reticulum-localized adapter protein, Stimulator of Interferon Genes (STING). The objective of the study is to characterize the activation of STING-dependent signaling pathway(s) to further the long-term goal of delineating how Type I IFNs are regulated during intracellular infection of macrophages. Certain intracellular pathogens modulate the function of host mitochondria. It is hypothesized that intracellular infection of macrophages causes mitochondrial dysregulation, prompting generation of Reactive Oxygen Species (ROS), activating STING-dependent innate immune pathways, leading to expression of the prototypical type I IFN, IFN-¿. The small molecule 5,6-dimethylxanthenone-4-acetic acid (DMXAA) is a potent activator of STING-dependent signaling in macrophages and will be used as a surrogate for intracellular infection. Additionally, STING-dependent activation in macrophages will be examined in response to an intracellular bacterial (Francisella tularensis) or viral (Respiratory Syncytial Virus (RSV)) infection. The first Aim of the study will be to determine whether mitochondrial ROS generation is sufficient for STING dimerization and activation of downstream signaling components, and establish the necessity of mitochondrial ROS generation for IFN- ¿ expression during infection or chemical treatment. The second Aim will establish how mitochondrial function and mitochondrial ROS is modulated by infection or DMXAA treatment. It is predicted that mitochondrial ROS generated during DMXAA treatment, or infection with F. tularensis or RSV, will be necessary for activation of STING-dependent innate immune signaling pathways following ROS-dependent dimerization of STING. Due to the potential commonality of mitochondrial subversion in infectious disease, the mechanism characterized in this project could have wide-ranging applications to other infectious organisms.