Helicase Regulation of dsRNA Signaling and Innate Antiviral Immune Responses

描述（由申请人提供）：本项目的长期目标是了解先天性抗病毒反应的调节机制和特定介质。对宿主对病毒感染的免疫应答的主要贡献是I型干扰素（IFN）的产生和应答。病毒感染或积累的病毒复制中间体如双链RNA（dsRNA）可以在大多数细胞中触发IFN生物合成，而不管Toll样受体系统的存在。胞质dsRNA的检测由传感器蛋白家族介导，所述传感器蛋白家族包括RIG-I、MDA 5和LGP 2，这三种蛋白含有DEXD/H-box RNA解旋酶结构域。RIG-I和MDA 5解旋酶结构域融合到与CARD结构域蛋白同源的N-末端区域，并且是导致IFN生物合成的正信号蛋白。LGP 2缺乏CARD结构域，并且已被表征为IFN合成的反馈抑制剂。尽管RNA解旋酶结构域相似，但对特定的酶活性以及催化活性如何影响信号传导知之甚少。初步结果和已发表的报告揭示了高度的特异性RNA识别和差异的要求之间的解旋酶蛋白的酶活性。天然抑制剂副粘病毒V蛋白揭示了进一步的特异性，其选择性靶向MDA 5和LGP 2，但不靶向RIG-I。该提案将确定RNA靶向偏好和酶专业化的作用，赋予解旋酶介导的抗病毒反应的特异性和选择性。选择性副粘病毒解旋酶干扰的分子基础将被揭示，并与MDA 5和LGP 2对宿主反应的贡献的生物学评价相关。解旋酶介导的信号转导的调控机制和细胞合作伙伴的特点。这些目标将揭示细胞内先天性抗病毒反应的正向和负向调节的特异性决定因素。副粘病毒如麻疹、腮腺炎、人副流感病毒和呼吸道合胞病毒，以及其他RNA病毒，包括流感、HIV、埃博拉病毒和丙型肝炎病毒，是全球范围内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.