Qin Xiaowei, Li Chuanrui, Liang Mincong, Qian Zhen, You Yanlin, Weng Shaoping, He Jianguo, Guo Changjun
School of Marine Sciences, State Key Laboratory for Biocontrol/Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Guangdong Provincial Key Laboratory of Marine Resources and Coastal Engineering & Guangdong Provincial Observation and Research Station for Marine Ranching of the Lingdingyang Bay, Sun Yat-sen University, Guangzhou, China.
School of Life Sciences, Guangdong Province Key Laboratory for Aquatic Economic Animals, Sun Yat-sen University, Guangzhou, China.
Front Immunol. 2024 Dec 11;15:1525376. doi: 10.3389/fimmu.2024.1525376. eCollection 2024.
Stimulator of interferon genes (STING) is a key connector protein in interferon (IFN) signaling, crucial for IFN induction during the activation of antiviral innate immunity. In mammals, ring finger protein 5 (RNF5) functions as an E3 ubiquitin ligase, mediating STING regulation through K150 ubiquitylation to prevent excessive IFN production. However, the mechanisms underlying RNF5's regulation of STING in teleost fish remain unknown. This study investigated the regulatory role of the mandarin fish () RNF5 (RNF5) in the STING-mediated antiviral immune response and identified the specific regulatory sites on STING. Furthermore, an examination of RNF5 expression patterns in virus-infected cells revealed its responsiveness to mandarin fish ranavirus (MRV) infection. The ectopic expression of RNF5 suppressed STING-mediated IFN signaling and facilitated MRV replication. Co-immunoprecipitation experiments indicated an interaction between RNF5 and STING. The further experiments demonstrated that RNF5 exerted its inhibitory effect by promoting the degradation of STING, which was observed to be blocked by MG132 treatment. Ubiquitination assays with various STING mutants showed that RNF5 catalyzed the ubiquitination of STING at K135 and K155 residues. Furthermore, we provided evidence that RNF5 significantly attenuated STING-dependent antiviral immunity by targeting negative regulators within the STING signaling cascade. This study underscored that RNF5 negatively regulated the STING-mediated IFN signaling pathway in mandarin fish, attenuated STING's antiviral activity, and facilitated STING degradation via the ubiquitin-proteasome pathway at two novel lysine sites (K135 and K155). Our work offered valuable insights into the regulatory mechanisms of STING-mediated signaling in teleost fish, paving the way for further research.
干扰素基因刺激因子（STING）是干扰素（IFN）信号通路中的关键衔接蛋白，在抗病毒天然免疫激活过程中对IFN的诱导至关重要。在哺乳动物中，环指蛋白5（RNF5）作为一种E3泛素连接酶，通过K150泛素化介导STING调节，以防止IFN过度产生。然而，硬骨鱼中RNF5对STING的调节机制仍不清楚。本研究调查了鳜鱼RNF5（RNF5）在STING介导的抗病毒免疫反应中的调节作用，并确定了STING上的特定调节位点。此外，对病毒感染细胞中RNF5表达模式的检测揭示了其对鳜鱼蛙病毒（MRV）感染的反应。RNF5的异位表达抑制了STING介导的IFN信号通路，并促进了MRV复制。免疫共沉淀实验表明RNF5与STING之间存在相互作用。进一步的实验表明，RNF5通过促进STING的降解发挥其抑制作用，MG132处理可阻断这种降解。对各种STING突变体进行的泛素化分析表明，RNF5催化STING在K135和K155残基处的泛素化。此外，我们提供的证据表明，RNF5通过靶向STING信号级联中的负调节因子，显著减弱了STING依赖性抗病毒免疫。本研究强调，RNF5在鳜鱼中负调节STING介导的IFN信号通路，减弱STING的抗病毒活性，并通过泛素-蛋白酶体途径在两个新的赖氨酸位点（K135和K155）促进STING降解。我们的工作为硬骨鱼中STING介导的信号调节机制提供了有价值的见解，为进一步研究铺平了道路。
