Role of ADAM9 in viral RNA sensing and antiviral innate immunity

项目摘要 微小核糖核酸病毒感染是人类病毒性脑炎和心肌炎的主要原因。这些病毒 感染可导致大脑和心脏的大量炎症改变，并导致显著的发病率。 和死亡率。免疫系统检测微小核糖核酸病毒感染和其他单链RNA(单链RNA) 病毒，通过DEAD/H盒(DDX)解旋酶感知胞质病毒单链RNA并启动保护性干扰素 (干扰素)反应。在这一过程中起关键作用的两个DDX解旋酶是维甲酸诱导基因I(RIG-I)和 黑素瘤分化相关基因5(MDA5)。Rig-I和MDA5都是Rig-I类成员 受体(RLR)家族的RNA传感解旋酶。RIG-I已知能感知负义单链RNA(-ssRNA) 病毒(如仙台病毒或水疱性口炎病毒)，而MDA5是来自 小核糖核酸病毒和其他正义单链RNA(+单链RNA)病毒，包括SARS-CoV2和其他 冠状病毒。MDA5是如何被激活和调节的目前还不是很清楚，这与 RIG-I，其激活机制已被详细阐明。 为了研究心肌炎和脑炎的发病机制，研究人员使用了一种原型 小核糖核酸病毒家族的成员，脑心肌炎病毒(EMCV)。使用EMCV，我们演示了 A去整合素和金属蛋白酶蛋白(ADAM9)在病毒发病机制中的重要作用我们 发现缺乏ADAM9的小鼠很快就会死于EMCV感染，但没有表现出这种特征 在野生型小鼠身上看到的干扰素反应。我们的数据表明ADAM9在病毒RNA诱导的干扰素中起到了新的作用 通过DDX解旋酶MDA5生产。 在EMCV感染中，MDA5是识别病毒RNA的传感器，并启动信号级联反应， 导致线粒体抗病毒信号(MAV)途径的激活和随后的干扰素的产生。 当病毒基因组与宿主细胞中的核酸传感器相互作用激活时，干扰素的产生就会被触发 下游的小路。宿主的干扰素反应对于通过限制病毒复制来保护宿主至关重要。我们 假设ADAM9的S在病毒诱导的干扰素产生中的作用是通过MDA5-MAVS途径介导的。 ADAM9在调节干扰素对多种RNA病毒的反应中的作用，包括小核糖核酸病毒和 冠状病毒，将根据其对MDA5与病毒RNA相互作用的能力和其 MAVS途径接头和蛋白对蛋白质-蛋白质相互作用和翻译后修饰的影响 效应器蛋白。通过这些实验，我们将定义新的干扰素激活途径，并更好地定义 研究脑炎和心肌炎的动物模型系统中RNA病毒的致病机制。

Project Abstract Picornavirus infections are a leading cause of viral encephalitis and myocarditis in humans. These viral infections can cause substantial inflammatory changes in the brain and heart and lead to significant morbidity and mortality. The immune system detects picornavirus infections, and other single-stranded RNA (ssRNA) viruses, via DEAD/H-box (DDX) helicases that sense cytosolic viral ssRNA and initiate the protective interferon (IFN) response. Two DDX helicases critical in this process are retinoic acid-inducible gene I (RIG-I) and melanoma differentiation-associated gene 5 (MDA5). Both RIG-I and MDA5 are members of the RIG-I-like receptor (RLR) family of RNA-sensing helicases. RIG-I is known to sense negative-sense ssRNA (–ssRNA) viruses (e.g., Sendai virus or vesicular stomatitis virus), while MDA5 is the major sensor for RNA from picornaviruses and other positive-sense ssRNA (+ssRNA) viruses including SARS-CoV2 and other coronaviruses. How MDA5 is activated and regulated is currently not well known, which is in striking contrast to RIG-I for which the activating mechanisms have been elucidated in detail. To study the pathogenesis of myocarditis and encephalitis, researchers have used a prototypical member of the picornavirus family, encephalomyocarditis virus (EMCV). Using EMCV, we demonstrated an important role for the A disintegrin and metalloproteinase protein (ADAM9) in viral pathogenesis. We discovered that mice lacking ADAM9 rapidly succumb to EMCV infection without mounting the characteristic IFN response seen in wild-type mice. Our data indicate a novel role for ADAM9 in viral RNA-induced IFN production through the DDX helicase MDA5. In EMCV infection, MDA5 is the sensor that recognizes viral RNA and initiates a signaling cascade that leads to activation of the mitochondrial antiviral signaling (MAVS) pathway and subsequent IFN production. IFN production is triggered when the viral genome interacts with nucleic acid sensors in the host cell to activate downstream pathways. The host IFN response is crucial to protect the host by limiting virus replication. We hypothesize that ADAM9’s role in viral-induced IFN production is mediated through the MDA5-MAVS pathway. The role of ADAM9 in regulating the IFN response to diverse RNA viruses, including picornaviruses and coronaviruses, will be defined in terms of its effects on the ability of MDA5 to interact with viral RNA and its effect on protein-protein interactions and post-translational modifications of MAVS pathway adapters and effector proteins. Through these experiments, we will define new pathways of IFN activation and better define the pathogenesis of RNA viruses in an animal model system for studying encephalitis and myocarditis.