Helicase Regulation of dsRNA Signaling and Innate Antiviral Immune Responses

描述(由申请人提供)：该项目的长期目标是了解先天抗病毒反应的调节机制和特定媒介。对病毒感染的宿主免疫反应的一个主要贡献是I型干扰素的产生和反应。病毒感染或累积的病毒复制中间产物如双链RNA(DsRNA)可在大多数细胞中触发干扰素的生物合成，而与Toll样受体系统的存在无关。胞质dsRNA的检测是由一系列传感器蛋白介导的，其中包括RIG-I、MDA5和LGP2，这三种蛋白含有DEXD/H-box RNA解旋酶结构域。RIG-I和MDA5解旋酶结构域融合在一个与CARD结构域蛋白同源的N-末端，是导致干扰素生物合成的阳性信号蛋白。LGP2缺乏CARD结构域，被认为是干扰素合成的反馈抑制因子。尽管RNA解旋酶结构域相似，但人们对其特定的酶活性以及催化活性如何影响信号转导知之甚少。初步结果和已发表的报告显示，在RNA识别和不同解旋酶蛋白对酶活性的不同要求方面具有高度的特异性。天然的抑制物，副粘病毒V蛋白，选择性地针对MDA5和LGP2，而不是RIG-I，揭示了进一步的特异性。这项提议将确定RNA靶标偏好和酶特化的作用，赋予解旋酶介导的抗病毒反应特异性和选择性。选择性副粘病毒解旋酶干扰的分子基础将被揭示，并与MDA5和LGP2对宿主反应的贡献的生物学评估相关联。将描述解旋酶介导的信号的调节机制和细胞伙伴。这些目的将揭示细胞内固有抗病毒反应的积极和消极调节的特异性决定因素。副粘病毒如麻疹、腮腺炎、人类副流感和呼吸道合胞病毒，以及其他RNA病毒包括流感、艾滋病毒、埃博拉病毒和丙型肝炎病毒，在全球范围内都是对人类健康的传染性威胁。拟议的实验将揭示细胞抗病毒反应的基本机制，并确定细胞和病毒抑制机制的分子基础。这一战略将揭示抗病毒反应的优势和弱点，并确定治疗干预的目标。

DESCRIPTION (provided by applicant): The long term objective for this project is to understand the regulatory mechanisms and specific mediators of innate antiviral responses. A major contribution to host immune responses to virus infection is the production of and response to type I interferon (IFN). Virus infection or accumulated virus replication intermediates like double-stranded RNA (dsRNA) can trigger IFN biosynthesis in most cells irrespective of the presence of Toll-like receptor systems. Detection of cytosolic dsRNA is mediated by a family of sensor proteins that includes RIG-I, MDA5, and LGP2, three proteins that contain DEXD/H-box RNA helicase domains. RIG-I and MDA5 helicase domains are fused to an N-terminal region homologous to CARD domain proteins, and are positive signaling proteins leading to IFN biosynthesis. LGP2 lacks the CARD domain, and has been characterized as a feedback inhibitor for IFN synthesis. Despite the RNA helicase domain similarities, little is known about the specific enzymatic activities and how catalytic activity can influence the signaling. Preliminary results and published reports reveal a high degree of specificity in RNA recognition and differential requirements for enzymatic activity among the helicase proteins. Further specificity is revealed by natural inhibitors, paramyxovirus V proteins, that selectively target MDA5 and LGP2, but not RIG-I. This proposal will determine RNA target preferences and roles for enzymatic specialization that confer specificity and selectivity to helicase-mediated antiviral responses. The molecular basis for selective paramyxovirus helicase interference will be revealed and correlated with biological evaluation of the contributions of MDA5 and LGP2 to host responses. Regulatory mechanisms and cellular partners for helicase-mediated signaling will be characterized. These aims will expose specificity determinants for both positive and negative regulation of the intracellular innate antiviral response. Paramyxoviruses like measles, mumps human parainfluenza, and respiratory syncytial viruses, as well as other RNA viruses including influenza, HIV, Ebola and hepatitis C viruses are infectious threats to human health worldwide. The proposed experiments will reveal basic mechanisms of cellular antiviral responses and determine the molecular basis for both cellular and viral inhibition mechanisms. This strategy will reveal the strengths and vulnerabilities of the antiviral response and identify targets for therapeutic intervention.