Zhang Hong-Lei, Ye Han-Qing, Liu Si-Qing, Deng Cheng-Lin, Li Xiao-Dan, Shi Pei-Yong, Zhang Bo
Chinese Academy of Sciences Key Laboratory of Special Pathogens and Biosafety, Center for Emerging Infectious Diseases, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, China.
University of Chinese Academy of Sciences, Beijing, China.
J Virol. 2017 Aug 24;91(18). doi: 10.1128/JVI.02396-16. Print 2017 Sep 15.
West Nile virus (WNV) is a mosquito-borne flavivirus that causes epidemics of encephalitis and viscerotropic disease worldwide. This virus has spread rapidly and has posed a significant public health threat since the outbreak in New York City in 1999. The interferon (IFN)-mediated antiviral response represents an important component of virus-host interactions and plays an essential role in regulating viral replication. Previous studies have suggested that multifunctional nonstructural proteins encoded by flaviviruses antagonize the host IFN response via various means in order to establish efficient viral replication. In this study, we demonstrated that the nonstructural protein 1 (NS1) of WNV antagonizes IFN-β production, most likely through suppression of retinoic acid-inducible gene I (RIG-I)-like receptor (RLR) activation. In a dual-luciferase reporter assay, WNV NS1 significantly inhibited the activation of the IFN-β promoter after Sendai virus infection or poly(I·C) treatment. NS1 also suppressed the activation of the IFN-β promoter when it was stimulated by interferon regulatory factor 3 (IRF3)/5D or its upstream molecules in the RLR signaling pathway. Furthermore, NS1 blocked the phosphorylation and nuclear translocation of IRF3 upon stimulation by various inducers. Mechanistically, WNV NS1 targets RIG-I and melanoma differentiation-associated gene 5 (MDA5) by interacting with them and subsequently causing their degradation by the proteasome. Furthermore, WNV NS1 inhibits the K63-linked polyubiquitination of RIG-I, thereby inhibiting the activation of downstream sensors in the RLR signaling pathway. Taken together, our results reveal a novel mechanism by which WNV NS1 interferes with the host antiviral response. WNV Nile virus (WNV) has received increased attention since its introduction to the United States. However, the pathogenesis of this virus is poorly understood. This study demonstrated that the nonstructural protein 1 (NS1) of WNV antagonizes the induction of interferon beta (IFN-β) by interacting with and degrading retinoic acid-inducible gene I (RIG-I) and melanoma differentiation-associated gene 5 (MDA5), which are crucial viral sensors in the host innate immune system. Further experiments suggested that NS1-mediated inhibition of the RIG-I-like receptor (RLR) signaling pathway involves inhibition of RIG-I K63-linked polyubiquitination and that the proteasome plays a role in RIG-I degradation. This study provides new insights into the regulation of WNV NS1 in the RLR signaling pathway and reveals a novel mechanism by which WNV evades the host innate immune response. The novel findings may guide us to discover new therapeutic targets and develop effective vaccines for WNV infections.
西尼罗河病毒（WNV）是一种由蚊子传播的黄病毒，可在全球范围内引发脑炎和嗜内脏疾病的流行。自1999年在纽约市爆发以来，这种病毒迅速传播，对公众健康构成了重大威胁。干扰素（IFN）介导的抗病毒反应是病毒与宿主相互作用的重要组成部分，在调节病毒复制中起着至关重要的作用。先前的研究表明，黄病毒编码的多功能非结构蛋白通过各种方式拮抗宿主的IFN反应，以建立有效的病毒复制。在本研究中，我们证明西尼罗河病毒的非结构蛋白1（NS1）拮抗IFN-β的产生，很可能是通过抑制视黄酸诱导基因I（RIG-I）样受体（RLR）的激活。在双荧光素酶报告基因检测中，西尼罗河病毒NS1在仙台病毒感染或聚肌苷酸-聚胞苷酸（poly(I·C)）处理后显著抑制IFN-β启动子的激活。当IFN-β启动子受到干扰素调节因子3（IRF3）/5D或RLR信号通路中其上游分子刺激时，NS1也抑制其激活。此外，NS1在受到各种诱导剂刺激后阻断IRF3的磷酸化和核转位。从机制上讲，西尼罗河病毒NS1通过与维甲酸诱导基因I（RIG-I）和黑色素瘤分化相关基因5（MDA5）相互作用并随后使其被蛋白酶体降解来靶向它们。此外，西尼罗河病毒NS1抑制RIG-I的K63连接的多聚泛素化，从而抑制RLR信号通路中下游传感器的激活。综上所述，我们的结果揭示了西尼罗河病毒NS1干扰宿主抗病毒反应的新机制。自西尼罗河病毒传入美国以来，它受到了越来越多的关注。然而，这种病毒的发病机制尚不清楚。本研究表明，西尼罗河病毒NS1通过与宿主先天免疫系统中关键的病毒传感器RIG-I和MDA5相互作用并使其降解来拮抗干扰素β（IFN-β）的诱导。进一步的实验表明，NS1介导的对RIG-I样受体（RLR）信号通路的抑制涉及对RIG-I的K63连接的多聚泛素化的抑制，并且蛋白酶体在RIG-I的降解中起作用。本研究为西尼罗河病毒NS1在RLR信号通路中的调节提供了新的见解，并揭示了西尼罗河病毒逃避宿主先天免疫反应的新机制。这些新发现可能指导我们发现新的治疗靶点并开发针对西尼罗河病毒感染的有效疫苗。
