College of Life Sciences, Henan Agricultural University, Zhengzhou, 450002, China.
CAS Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, 100101, China.
Cell Commun Signal. 2022 Jul 12;20(1):103. doi: 10.1186/s12964-022-00922-3.
Cytosolic RNA sensing can elicit immune responses against viral pathogens. However, antiviral responses must be tightly regulated to avoid the uncontrolled production of type I interferons (IFN) that might have deleterious effects on the host. Upon bacterial infection, the germinal center kinase MST4 can directly phosphorylate the adaptor TRAF6 to limit the inflammatory responses, thereby avoiding the damage caused by excessive immune activation. However, the molecular mechanism of how MST4 regulates virus-mediated type I IFN production remains unknown.
The expression levels of IFN-β, IFIT1, and IFIT2 mRNA were determined by RT-PCR. The expression levels of p-IRF3, IRF3, RIG-I, MAVS, and MST4 proteins were determined by Western blot. The effect of secreted level of IFN-β was measured by ELISA. The relationship between MST4 and MAVS was investigated by immunofluorescence staining and coimmunoprecipitation.
In this study, we reported that MST4 can act as a negative regulator of type I IFN production. Ectopic expression of MST4 suppressed the Poly (I:C) (polyino-sinic-polycytidylic acid)- and Sendai virus (SeV)-triggered production of type I IFN, while the knockdown of MST4 enhanced the production of type I IFN. Mechanistically, upon SeV infection, the MST4 competed with TRAF3 to bind to the 360-540 domain of MAVS, thereby inhibiting the TRAF3/MAVS association. Additionally, MST4 facilitated the interaction between the E3 ubiquitin ligase Smurf1 and MAVS. This promoted the K48-linked ubiquitination of MAVS, thereby accelerating the ubiquitin-mediated proteasome degradation of MAVS.
Our findings showed that MST4 acted as a crucial negative regulator of RLR-mediated type I IFN production. Video Abstract.
细胞质 RNA 感应可以引发针对病毒病原体的免疫反应。然而，抗病毒反应必须受到严格调控，以避免不受控制地产生可能对宿主产生有害影响的 I 型干扰素 (IFN)。在细菌感染时，生发中心激酶 MST4 可以直接磷酸化接头 TRAF6，从而限制炎症反应，避免过度免疫激活造成的损伤。然而，MST4 如何调节病毒介导的 I 型 IFN 产生的分子机制尚不清楚。
通过 RT-PCR 测定 IFN-β、IFIT1 和 IFIT2 mRNA 的表达水平。通过 Western blot 测定 p-IRF3、IRF3、RIG-I、MAVS 和 MST4 蛋白的表达水平。通过 ELISA 测定 IFN-β 的分泌水平。通过免疫荧光染色和共免疫沉淀研究 MST4 与 MAVS 之间的关系。
在本研究中，我们报道 MST4 可以作为 I 型 IFN 产生的负调控因子。MST4 的异位表达抑制了 Poly（I:C）（多聚肌苷酸-多聚胞苷酸）和仙台病毒（SeV）触发的 I 型 IFN 的产生，而 MST4 的敲低增强了 I 型 IFN 的产生。机制上，在 SeV 感染后，MST4 与 TRAF3 竞争结合 MAVS 的 360-540 结构域，从而抑制 TRAF3/MAVS 结合。此外，MST4 促进 E3 泛素连接酶 Smurf1 与 MAVS 的相互作用。这促进了 MAVS 的 K48 连接泛素化，从而加速了 MAVS 的泛素介导的蛋白酶体降解。
我们的研究结果表明，MST4 作为 RLR 介导的 I 型 IFN 产生的关键负调控因子发挥作用。
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