USP18调控MAVS泛素化修饰及抗RNA病毒天然免疫的机制研究

During the infection of RNA viruses, the activation of MAVS, a key adaptor molecule, is particularly important for the signaling transduction and production of type I interferons. However, the molecular mechanisms regulating the activation of MAVS is not completely understood. Ubiquitination, with its versatile functions associated with multiple types, plays a central role in modulating almost every single step of this signaling cascade. Ubiquitin ligases and deubiquitinases (DUBs), which controls the process of ubiquitination, are the key participants in fine-tuning antiviral signaling transduction. Exploring their dynamic interaction and cooperation in the regulation of signaling molecules is of importance in understanding the homeostasis of the immune response. Our preliminary study has shown that USP18 can interact with MAVS and promote the K63-linked polyubiquitination of MAVS, ultimately enhancing the type I interferon response during RNA virus infection. Further study also indicates that the effect on ubiquitination of MAVS by USP18 is dependent on another E3 ubiquitin ligase TRIM31, but molecular mechanisms for modulating the interaction between TRIM31 and MAVS by USP18 is unresolved. In this study, we are aimed to employ the comprehensive methods, including biochemistry, molecular biology, immunology, together with USP18 knockout mice model to investigate the function of USP18 in innate immunity to RNA viruses and molecular mechanisms for USP18 regulation of ubiquitination of MAVS through TRIM31. Our study is expected to provide a theoretical basis for antiviral drug design and clinical prevention of viral infection.

在RNA病毒感染过程中，MAVS作为重要的接头分子，其活化对下游信号转导和I型干扰素产生起着极其重要的作用, 但其活化的调控机制尚不完全清楚。泛素化修饰具有多种形式和多样功能，可调控天然免疫信号通路中每一步信号转导。泛素连接酶和去泛素化酶相互协同调控蛋白质的泛素化修饰，研究他们如何协同和动态调控机体的免疫信号分子对解析恰当免疫应答具有重要意义。前期工作发现USP18与MAVS相互作用，上调MAVS的K63位泛素化修饰并能够促进病毒感染后I型干扰素的产生；进一步研究发现USP18对MAVS的泛素化修饰调控依赖于泛素连接酶TRIM31，但是具体的调控机制尚不明确。本课题拟综合采用生物化学、分子生物学和免疫学等技术方法，并结合基因敲除小鼠模型深入研究USP18通过TRIM31调控MAVS进而影响抗病毒免疫反应的分子机制，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RNA病毒感染过程中，MAVS作为重要的接头分子，其活化对下游信号转导和I型干扰素产生起着极其重要的作用, 但其活化的调控机制尚不完全清楚。泛素化修饰具有多种形式和多样功能，可调控天然免疫信号通路中每一步信号转导。泛素连接酶和去泛素化酶相互协同调控蛋白质的泛素化修饰，研究他们如何协同和动态调控机体的免疫信号分子对解析恰当免疫应答具有重要意义。我们发现线粒体定位的去泛素化酶USP18特异性与MAVS结合，促进MAVS的K63位泛素化修饰水平，以及MAVS的聚集。USP18上调RNA病毒感染如仙台病毒和脑心肌炎病毒病毒引起的I型干扰素的表达。USP18缺失的小鼠对RNA病毒更加易感。机制上，我们发现USP18作为一个支架蛋白，促进TRIM31从细胞浆转运到线粒体，进而促进TRIM31与MAVS蛋白在线粒体上的相互作用。我们的结果提示USP18作为重要的调控MAVS蛋白质翻译后修饰的去泛素化酶，我们的结果为抗病毒药物设计和临床干预病毒感染提供了理论基础。