蛋白质翻译后修饰调控抗病毒天然免疫反应的机制研究

Viral infection is a major threat to human health. The innate immunity is the first line of defense against invading viruses. Recognition of the pathogen associated molecular patterns (PAMPs) by the pattern recognition receptors (PRRs) of the innate immune system initiates complicated signaling events leading to production of type I interferons (IFNs). Type I IFNs further activate downstream signaling pathways to induce transcription of a wide range of antiviral genes, leading to the elimination of virus infection. However, aberrant activation of the innate immunity can lead to human autoimmune diseases and cancers. Thus, the innate immunity need to be tightly controlled. Post-translational modifications (PTMs) of the innate sensors and downstream signaling molecules influence their activity and function through inducing their covalent linkage to new functional groups. In our preliminary data, we showed protein arginine methyltransferase 1 (PRMT1) plays a very important role in the regulation of innate antiviral signaling. We found PRMT1 could target TBK1 to regulate its arginine methylation. We also found listerin E3 ubiquitin protein ligase 1 (LTN1) could interact with and catalyze K63-linked polyubiquitination of STING. While, OTU domain-containing protein 5 (OTUD5) could cleave the K48-linked polyubiquitination chains from STING. These data indicate that LTN1 and OTUD5 may play essential roles in the regulation of innate signaling against DNA virus through modification of the ubiquitination status of STING. In this proposal, we will establish gene deficient mice and apply various molecular techniques to investigate the physiological functions and molecular mechanisms of PRMT1, LTN1 and OTUD5 in the regulation of innate antiviral signaling. This study will reveal new understandings for the regulation of innate antiviral immune signaling especially the intracellular DNA-mediated signaling. Furthermore, the results will provide therapeutic clues for the design of new antiviral drugs, leading to the protection and cure of infection diseases.

天然免疫是机体抵抗病毒感染的第一道防线，对于病毒的清除起着至关重要的作用，但其异常活化会导致自身免疫病和肿瘤等重大疾病的发生。天然免疫信号通路中关键蛋白的翻译后修饰是抗病毒天然免疫反应的重要调控方式，然而其分子机制有待进一步探索。我们前期研究发现精氨酸甲基转移酶1（PRMT1）可靶向抗病毒天然免疫信号通路的关键激酶TBK1，并通过其甲基化转移酶活性调控机体抗病毒免疫反应；泛素连接酶LTN1可靶向抗DNA病毒天然免疫信号通路的关键接头分子STING，促其进行K63位泛素化修饰，而去泛素化酶OTUD5可去除STING K48位连接的泛素链，从而精密调控机体抗DNA病毒天然免疫反应。本课题拟利用生物化学、分子生物学和免疫学等技术和方法，并结合基因敲除小鼠模型深入研究PRMT1、LTN1和OTUD5在抗病毒天然免疫中的生理功能及其分子机制，为抗病毒药物设计和临床防治病毒感染等疾病提供理论基础。

在人类传染病中，病毒感染性疾病高达60%~65%，病毒在与宿主共进化过程中形成了对宿主抗病毒天然免疫反应的精巧调节，从而逃避人体免疫系统攻击，严重危害人类健康。天然免疫作为机体抵抗感染的第一道防线，会迅速感知病毒感染，产生包括I型干扰素在内的多种细胞因子，这些细胞因子一方面可以直接抑制病毒的复制，诱导被感染的细胞凋亡；另一方面还可以进一步激活炎症反应以及适应性免疫，从而杀灭病毒并清除病毒感染的细胞。研究抗病毒天然免疫活化的调控机制，将有助于阐明机体抗病毒免疫反应的机理，帮助寻找新的药物靶标和设计抗病毒药物，并为治疗和预防自身免疫病、炎性疾病以及肿瘤等人类重大疾病提供理论指导，具有重大的科学意义和现实意义。在该项目的资助下，申请人紧密围绕“蛋白质翻译后修饰调控抗病毒天然免疫反应的机制”这一科学问题，进行了一系列深入的研究，发现蛋白质精氨酸甲基转移酶PRMT1、PMRT9，E3泛素连接酶LTN1，去泛素化酶OTUD5、USP27X、USP18等在抗病毒天然免疫信号转导中的重要作用，揭示了蛋白质翻译后修饰调控抗病毒天然免疫反应的关键机制。作为通讯作者发表标注课题号的相关研究论文21篇，其中Signal Transduct Target Ther 3篇、Cell Mol Immunol 1篇、Nat Commun 2篇、Cell Rep 1篇、Adv Sci 1篇、Autophagy 1篇、Cell Death Differ 2篇、J Immunol 5篇。获批发明专利1项。作为项目负责人获批国家自然基金重点项目2项，国家重点研发子课题1项，山东省重点研发计划1项。任务期内，申请人获得国家科技进步二等奖1项（第四位），教育部自然科学一等奖1项（第一位，公示已结束）。培养博士毕业生和硕士毕业生21名，申请人获评国家突出贡献中青年专家和教育部长江学者特聘教授，培养国家优青获得者1名，山东省优青获得者2名。