Control of Viral Pathogenesis by Regulation of 2-5A Levels

干扰素诱导和信号传递是病毒双链引发的早期抗病毒反应 (DS)RNA。虽然对限制病毒复制和传播至关重要，但干扰素反应的过度表达可能是 对人体健康有害。例如，艾卡迪-古提雷斯综合征(AGS)是一种严重的神经发育障碍 和炎症性遗传病，特征是宿主诱导过量的干扰素产生和信号传递 自身dsRNA。因此，了解寄主是如何调节自我诱导的dsRNA通路是很重要的。 DsRNA以及病毒(非自身)-dsRNA。寡腺苷合成酶-核糖核酸酶L(OAS-RNAs L)是一种 有效的抗病毒途径，严重限制了许多病毒的发病。在感应dsRNA时，OASs 产生2‘，5’-寡腺苷(2-5A)，激活核糖核酸酶L裂解宿主和病毒单链核糖核酸 从而限制蛋白质的产生、病毒的复制和传播，并导致细胞凋亡。在.期间 上一期我们鉴定和表征了病毒和宿主编码的磷酸二酯酶(PDE)是有效的 核糖核酸酶L激活的拮抗剂，最著名的是小鼠冠状病毒的PDE，NS2，一种肝脏特异性的 毒力因子。我们还确定OAS3是人类细胞中主要的抗病毒OAS。此外，我们发现， 核糖核酸酶L是主要的dsRNA依赖途径，通过 外源dsRNA或通过自身dsRNA在细胞中去除ADAR1的表达，ADAR1是一种破坏稳定的酶 DsRNA，当突变时可引起AGS。然而，在理解如何激活的过程中存在差距 控制核糖核酸酶L以防止dsRNA的潜在破坏性影响，同时仍保持 限制病毒复制和传播。在这个项目的继续中，我们将测试主持人的假设 病毒有多条途径控制2-5A的水平，激活核糖核酸酶L和核糖核酸酶 核糖核酸酶L的直接抗病毒、促细胞凋亡和促炎作用。 在三个互补的物种特有系统中研究美洲呼吸综合征-核糖核酸酶L系统的方法 具有独特的功能。我们将研究：1)ADAR1亚型和宿主PDE是如何调节2-5A水平的 人类细胞，并确定哪些OAS亚型参与其中；2)抗病毒、凋亡和炎症 核糖核酸酶L在MHV小鼠模型中协同清除病毒的作用；以及3)OAS-核糖核酸酶L如何 蝙蝠体内信号转导通路的表达和激活及其拮抗OAS-核糖核酸酶L的机制(S) 丝状病毒VP35激活。这些研究的结果应该会让我们更好地理解宿主 酶控制自身双链RNA和2-5A的水平，以限制未感染细胞中的核糖核酸酶L的活性，同时允许 病毒感染过程中的激活以及抗病毒、凋亡和促炎的联合作用 核糖核酸L在病毒清除中。这些研究将使我们能够确定增强宿主细胞对 病毒在最大限度地减少威胁的同时过度激活L的OAS-核糖核酸酶，最终可能有助于 确定病毒疾病和ADAR1突变的AGS患者的治疗策略。

Interferon (IFN) induction and signaling is an early antiviral response triggered by viral double-stranded (ds)RNA. While critical to limiting viral replication and spread, overexpression of the IFN response can be detrimental to human health. For example, Aicardi-Goutiéres syndrome (AGS) is a severe neurodevelopmental and inflammatory genetic disease, characterized by excessive IFN production and signaling induced by host self-dsRNA. Thus it is important to understand how the host regulates dsRNA pathways induced by self- dsRNA as well as viral (non self)-dsRNA. Oligoadenylate synthetase-ribonuclease L (OAS-RNase L) is a potent antiviral pathway that severely limits pathogenesis of many viruses. Upon sensing dsRNA, OASs produce 2',5'-oligoadenylates (2-5A) which activate RNase L to cleave both host and viral single-stranded RNA thereby limiting protein production, virus replication and spread, and leading to apoptotic cell death. During the last period we identified and characterized virus- and host-encoded phosphodiesterases (PDEs) as potent antagonists of RNase L activation, most notably the PDE of murine coronavirus (MHV), NS2, a liver specific virulence factor. We also identified OAS3 as the principal antiviral OAS in human cells. Moreover, we found that RNase L is the dominant dsRNA-dependent pathway leading to apoptosis in human cell lines by exogenous dsRNA or by self-dsRNA in cells ablated for expression of ADAR1, an enzyme that destabilizes dsRNA and when mutated can cause AGS. However, there is a gap in understanding how the activation of RNase L is controlled to prevent the potentially destructive effects of dsRNA while still maintaining the ability to limit viral replication and spread. In the continuation of this project, we will test the hypothesis that the host and viruses have multiple pathways to control the levels of 2-5A, its activation of RNase L and the directly antiviral as well as proapoptotic and proinflammatory effects of RNase L. We will use innovative approaches to investigate the OAS-RNase L system in three complementary species-specific systems, each with unique features. We will investigate: 1) how ADAR1 isoforms and host PDEs regulate levels of 2-5A in human cells, and determine which OAS isoforms are involved; 2) how the antiviral, apoptotic and inflammatory roles of RNase L cooperate to effect viral clearance in an MHV mouse model; and 3) how the OAS-RNase L pathway is expressed and activated in bats, and the mechanism(s) underlying antagonism of OAS-RNase L activation by filovirus VP35. Results of these studies should provide a better understanding of how host enzymes control the levels of self-dsRNA and 2-5A to limit RNase L activity in uninfected cells, while allowing activation during viral infections as well as the combined antiviral, apoptotic and proinflammatory roles of RNase L in viral clearance. These studies will allow us to identify targets that enhance host cell resistance to virus while minimizing the threat of over activation of OAS-RNase L to the host, and finally may contribute to identifying therapeutic strategies for viral diseases and for AGS patients with mutations in ADAR1.