去泛素化酶OTUD3调控自噬途径影响结核分枝杆菌感染的机制研究

Tuberculosis(TB) has plagued humans for thousands of years and remains a major public health problem in our era. Mycobacterium tuberculosis(Mtb), the etiological agent of human tuberculosis, is an extremely successful intracellular pathogen that has co-evolved with its host for eons. A better understanding of the molecular mechanisms underlying host anti-Mtb infection immune defense will provide new potential targets for effective host-directed therapies or adjuvant treatments for TB. Mtb preferentially resides and replicates in macrophages, while macrophages are key components of innate host defense and play a central role in tuberculosis pathology. Upon the invasion of pathogenic bacteria, the host ubiquitin system plays a critical role in activating the host innate immune responses and associated signaling pathways such as inflammatory and immune responses, autophagy, phagosome maturation and cell death,etc. However, it remains elusive the significance of deubiquitylating enzymes (DUBs) in Mtb infection. In our preliminary experiment, we modelled the process of Mtb infection in vitro, and found OTUD3 from varian-tumor proteases (OTUs) family of DUBs changed significantly. Based on the above background and privious experimental results, we plan to clarify the role and mechanism of OTUD3 during Mtb infection through conducting systematic research at molecular, cell and mouse overall levels. Moreover, the study will elucidate the downstreaming targets and regulation mechanisms of OTUD3. This study aims to uncover the function and molecular mechanisms of OTUD3 during Mtb infection, which will deepen our understanding of Mtb-host relationship.

肺结核是一种困扰人类数千年的传染病，至今仍然威胁着公众的健康。肺结核的致病菌结核分枝杆菌（Mycobacterium tuberculosis，Mtb）是极其成功的胞内菌，在与宿主长期的对抗过程中进化出许多生存策略，逃避宿主免疫细胞的杀伤。深入研究宿主的抗结核感染免疫机制是提高疫苗有效性，改善结核治疗策略的基础。泛素系统在激活宿主炎症免疫反应、细胞自噬、吞噬体成熟和细胞死亡等天然免疫功能及相关信号通路中发挥了重要的调控作用。然而，目前很少有研究报道去泛素化酶在Mtb感染巨噬细胞的过程中的功能。通过在体外模拟Mtb感染巨噬细胞的过程，我们对OTU家族去泛素化酶进行了筛选，发现OTUD3在感染后显著上调。本项目拟从分子、细胞、小鼠和病人标本等多个层面开展研究，明确OTUD3在Mtb感染过程中的功能，筛选和鉴定OTUD3在该过程中直接调控的靶分子并明确OTUD3对靶分子的调控机制。

炎症是机体对感染或危险的反应，响应迅速、明确并在威胁消除后终止。当这种调节失灵时，炎症性疾病就会给人类造成很大的痛苦。泛素化修饰精细调节着炎症信号通路的开关与持续，泛素化系统的紊乱与感染性疾病，自身免疫病及肿瘤等病理过程密切相关。E3泛素连接酶(E3)介导的泛素化和去泛素化过程与结肠炎症的发生发展密切相关。OTUD1参与与感染性疾病相关的免疫调节功能。然而，OTUD1在炎症性肠病(IBD)等结肠炎性疾病期间对肠道免疫反应的影响尚不清楚。在这里，我们发现OTUD1在小鼠中通过过度释放促炎细胞因子参与了右旋糖酐硫酸钠(DSS)诱导的结肠炎的发病机制。此外，骨髓移植实验显示，随系来源细胞中OTUD1在防止结肠炎方面起主导作用。机理上，OTUD1物理上与受体相互作用的丝氨酸/苏氨酸蛋白激酶1 (RIPK1)相互作用，选择性地从RIPK1上切割K63连接的多聚泛素链，以抑制NF-κB基本调节因子(NEMO)的招募。此外，溃疡性结肠炎(UC)患者粘膜标本中OTUD1的表达低于健康对照组。我们还发现UC相关的OTUD1 G430V突变破坏了OTUD1抑制RIPK1介导的NF-κB活化和诱发结肠炎的能力。综上所述，我们的研究揭示了OTUD1通过抑制RIPK1介导的NF-κB激活来调节结肠炎的作用，提示OTUD1-RIPK1轴可能是治疗IBD的一个潜在靶点。