Two Conserved Amino Acids within the NSs of Severe Fever with Thrombocytopenia Syndrome Phlebovirus Are Essential for Anti-interferon Activity
Two Conserved Amino Acids within the NSs of Severe Fever with Thrombocytopenia Syndrome Phlebovirus Are Essential for Anti-interferon Activity
复制标题
DOI：
10.1128/jvi.00706-18
复制
发表时间：
2018-10-01
影响因子：
5.4
通讯作者：
Ichinohe, Takeshi
中科院分区：
文献类型：
--
作者：
Moriyama, Miyu;Igarashi, Manabu;Ichinohe, Takeshi
严重发热伴血小板减少综合征静脉病毒（SFTSV）的非结构蛋白（NS）将TANK结合激酶1（TBK 1）隔离到NS诱导的细胞质结构中，以抑制干扰素（IFN）调节因子3（IRF 3）的磷酸化和核转位以及随后的干扰素β（IFN-β）产生。尽管SFTSV NS（NS（66-249））的C-末端区域与NS诱导的细胞质结构的形成和宿主IFN-β应答的抑制有关，但N-末端区域在拮抗宿主抗病毒应答中的作用仍有待确定。在这里，我们证明了两个保守的氨基酸在位置21和23的SFTSV和心脏地带病毒（HRTV）的NS是必不可少的抑制IRF 3磷酸化和IFN-β mRNA表达后感染SFTSV或重组流感病毒缺乏NS 1基因。令人惊讶的是，SFTSV/HRTV NS诱导的细胞质结构的形成对于抑制宿主的抗病毒反应不是必需的。相反，SFTSV/HRTV NS和TBK 1之间的关联是抑制线粒体抗病毒信号蛋白（MAVS）介导的IFN-β启动子活性激活所必需的。尽管SFTSV NS不能阻止TBK 1的泛素化，但它通过其N-末端激酶结构域（残基1至307）与TBK 1缔合以阻断TBK 1的自磷酸化。此外，我们发现野生型NS和SFTSV的21/23 A突变体（其中第21和23位残基被丙氨酸取代的NS）均抑制NLRP 3炎性小体依赖性白细胞介素-1 β（IL-1 β）分泌，表明这些残基的重要性仅限于TBK 1依赖性IFN信号传导。总之，我们的研究结果强烈牵连的两个保守的氨基酸在位置21和23的SFTSV/HRTV NS在抑制宿主干扰素responses.IMPORTANCE识别病毒的宿主先天免疫系统中起着至关重要的作用，不仅在提供抗病毒感染，但也在启动抗原特异性适应性免疫反应对病毒。重症发热伴血小板减少综合征（SFTS）是由SFTS静脉病毒（SFTSV）引起的一种新型传染病。SFTSV的294个氨基酸的非结构蛋白（NS）与TANK结合激酶1（TBK 1）（宿主先天性抗病毒免疫的关键调节因子）相关，以抑制干扰素β（IFN-β）的产生并增强病毒复制。在这里，我们证明了两个保守的氨基酸在位置21和23的SFTSV和心脏地带病毒，另一种蜱传静脉病毒的NS，是必不可少的协会与TBK 1和抑制IFN-β的生产。我们的研究结果提供了重要的洞察SFTSV NS有助于抵消宿主抗病毒策略的分子机制。
The nonstructural protein (NSs) of severe fever with thrombocytopenia syndrome phlebovirus (SFTSV) sequesters TANK-binding kinase 1 (TBK1) into NSs-induced cytoplasmic structures to inhibit the phosphorylation and nuclear translocation of interferon (IFN) regulatory factor 3 (IRF3) and subsequent interferon beta (IFN-beta) production. Although the C-terminal region of SFTSV NSs (NSs(66-249)) has been linked to the formation of NSs-induced cytoplasmic structures and inhibition of host IFN-beta responses, the role of the N-terminal region in antagonizing host antiviral responses remains to be defined. Here, we demonstrate that two conserved amino acids at positions 21 and 23 in the SFTSV and heartland virus (HRTV) NSs are essential for suppression of IRF3 phosphorylation and IFN-beta mRNA expression following infection with SFTSV or recombinant influenza virus lacking the NS1 gene. Surprisingly, formation of SFTSV/HRTV NSs-induced cytoplasmic structures is not essential for inhibition of host antiviral responses. Rather, an association between SFTSV/HRTV NSs and TBK1 is required for suppression of mitochondrial antiviral signaling protein (MAVS)-mediated activation of IFN-beta promoter activity. Although SFTSV NSs did not prevent the ubiquitination of TBK1, it associates with TBK1 through its N-terminal kinase domain (residues 1 to 307) to block the autophosphorylation of TBK1. Furthermore, we found that both wild-type NSs and the 21/23A mutant (NSs in which residues at positions 21 and 23 were replaced with alanine) of SFTSV suppressed NLRP3 inflammasome-dependent interleukin-1 beta (IL-1 beta) secretion, suggesting that the importance of these residues is restricted to TBK1-dependent IFN signaling. Together, our findings strongly implicate the two conserved amino acids at positions 21 and 23 of SFTSV/HRTV NSs in the inhibition of host interferon responses.IMPORTANCE Recognition of viruses by host innate immune systems plays a critical role not only in providing resistance to viral infection but also in the initiation of antigen-specific adaptive immune responses against viruses. Severe fever with thrombocytopenia syndrome (SFTS) is a newly emerging infectious disease caused by the SFTS phlebovirus (SFTSV), a highly pathogenic tick-borne phlebovirus. The 294-amino-acid nonstructural protein (NSs) of SFTSV associates with TANK-binding kinase 1 (TBK1), a key regulator of host innate antiviral immunity, to inhibit interferon beta (IFN-beta) production and enhance viral replication. Here, we demonstrate that two conserved amino acids at positions 21 and 23 in the NSs of SFTSV and heartland virus, another tick-borne phlebo-virus, are essential for association with TBK1 and suppression of IFN-beta production. Our results provide important insight into the molecular mechanisms by which SFTSV NSs helps to counteract host antiviral strategies.