去泛素化酶USP13调控抗病毒天然免疫信号转导的分子机制研究

Host innate immune system constitutes the first line for defense against invading viruses. Pattern-recognition receptors detect viral nuclear acid and activate a series signaling cascades that lead to induction of various cytokines including type I interferons (IFNs) and TNF. These cytokines further induce expression of hundreds of downstream genes, the products of which inhibit viral replication and promote clearance of the infected cells. Mediator of IRF3 Activation (MITA, also known as STING or ERIS) is a critical adaptor protein that mediates innate antiviral responses. It has been well documented that posttranslational modifications such as ubiquitination and phosphorylation are critical for MITA activation. However, the reversal processes have not been fully understood. We have identified a MITA-interacting deubiquitinase USP13 by yeast two-hybrid assays and found that knockdown of USP13 potentiates viral infection-induced expression of type I IFNs, indicating that USP13 negatively regulates innate antiviral responses. In this study, we have generated USP13-deficient mice and will explore the roles and mechanisms of USP13 in innate antiviral immune signaling. This study will advance our knowledge about the elegant “check and balance” regulation of innate antiviral signaling.

宿主天然免疫系统是抵御病毒入侵的第一道生理防线，在抗病毒感染过程中发挥关键作用。天然免疫系统通过模式识别受体识别病毒核酸，触发一系列的信号级联反应，激活I型干扰素等细胞因子的表达。这些细胞因子进一步诱导大量的下游基因的表达，进而达到抑制病毒复制、清除被感染的细胞等目的。MITA是介导抗病毒天然免疫信号转导的一个关键接头蛋白，其活性受到泛素化修饰的严格调控，然而其去泛素化的调控机制目前尚不清楚。我们以MITA为诱饵蛋白进行了酵母双杂交实验，发现了去泛素化酶USP13与MITA相互作用。敲低USP13能促进MITA的泛素化、促进病毒感染诱导的IRF3与NF-kB的活化以及I型干扰素等细胞因子的表达。我们已经制备了USP13基因敲除小鼠，拟通过一系列的分子生化以及动物实验阐明USP13调控抗病毒天然免疫信号转导的分子机制。本项目的研究成果将对阐述抗病毒天然信号转导及其精细调控机制做出新的贡献。

MITA在介导抗病毒免疫以及自身免疫等过程中扮演关键角色，其活性与稳定性受到泛素化与去泛素化的严格调控。本项目围绕MITA的去泛素化调控机制进行了深入研究，发现USP13去MITA上K27链接的泛素化，USP49去MITA上K63链接的泛素化，进而抑制MITA的寡聚化与活化及其介导的抗病毒天然免疫信号转导；USP20去MITA上K48链接的泛素化，抑制MITA通过蛋白酶体途径降解，促进抗病毒天然免疫信号转导。相关研究发表在Nat Commun，Plos Pathog，以及J Immunol等感染免疫领域旗舰期刊上，被SCI引用超过25次（google Scholar）。这些研究进一步推动了对MITA调控机制以及抗病毒天然免疫调控机制的认识，为未来治疗病毒性疾病以及自身免疫性疾病提供理论基础与分子靶标。