mTOR Dysregulation by Vaccinia Virus F17 Controls Multiple Processes with Varying Roles in Infection
mTOR Dysregulation by Vaccinia Virus F17 Controls Multiple Processes with Varying Roles in Infection
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DOI：
10.1128/jvi.00784-19
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发表时间：
2019-08-01
影响因子：
5.4
通讯作者：
Walsh, Derek
中科院分区：
文献类型：
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作者：
Meade, Nathan;King, Melvin;Walsh, Derek
尽管产生了大量的细胞质DNA，痘病毒通过部署一系列蛋白质在多个层面上对抗宿主的抗病毒反应，继续有效地复制。其中，痘病毒蛋白F17失调宿主激酶哺乳动物雷帕霉素靶蛋白（mTOR），阻止干扰素刺激基因（STING）表达的激活，损害干扰素刺激基因（ISGs）的产生。然而，在缺乏F17的情况下，涉及的宿主DNA传感器及其对感染的影响尚不清楚。本研究表明，在巨噬细胞和肺成纤维细胞中，cycli -di- gmp - amp （cGAMP）合成酶（cGAS）是介导干扰素反应因子（IRF）激活和对缺乏F17的牛痘病毒的ISG反应的主要传感器，尽管其他传感器也在后者细胞类型中起作用。尽管如此，通过敲除cGAS或STING来消除ISG反应并不能挽救晚期病毒蛋白产生的缺陷，实验数据表明mTOR在这方面具有其他功能。mTOR根据细胞需求调节自噬和蛋白质合成过程。对野生型和F17突变型病毒的自噬反应没有显著差异，细胞类型或状态的自噬活性不同，与病毒蛋白积累缺陷没有相关性。相反，使用转化细胞或改变生长条件的结果表明，蛋白质积累的后期缺陷反映了F17突变体未能解除对mTOR的调节并刺激蛋白质产生。最后，修复方法表明，磷酸化可能会破坏F17作为结构蛋白和mTOR调节因子的功能。我们的发现揭示了F17在感染过程中复杂的多功能性。痘病毒是一种大的双链DNA病毒，完全在细胞质中复制，这是一种激活病原体传感器和先天抗病毒反应的不寻常行为。因此，为了复制，痘病毒编码了广泛的先天免疫拮抗剂，其中包括F17，一种失调哺乳动物雷帕霉素靶蛋白激酶（mTOR）以抑制干扰素刺激基因（ISG）反应的蛋白质。然而，在缺乏F17的情况下，检测感染的宿主传感器及其对感染的精确贡献尚不清楚。在这里，我们发现细胞质DNA传感器cGAS主要负责在感染不表达F17的痘病毒的生物学相关细胞类型中激活ISG反应。然而，在F17有助于抑制cgas介导的免疫反应的同时，F17表达类似于100种免疫反应和ISG拮抗剂的蛋白，我们发现其mTOR失调活性的一个关键功能是增强痘病毒蛋白的产生。
Despite producing enormous amounts of cytoplasmic DNA, poxviruses continue to replicate efficiently by deploying an armory of proteins that counter host antiviral responses at multiple levels. Among these, poxvirus protein F17 dysregulates the host kinase mammalian target of rapamycin (mTOR) to prevent the activation of stimulator of interferon genes (STING) expression and impair the production of interferon-stimulated genes (ISGs). However, the host DNA sensor(s) involved and their impact on infection in the absence of F17 remain unknown. Here, we show that cyclic-di-GMP-AMP (cGAMP) synthase (cGAS) is the primary sensor that mediates interferon response factor (IRF) activation and ISG responses to vaccinia virus lacking F17 in both macrophages and lung fibroblasts, although additional sensors also operate in the latter cell type. Despite this, ablation of ISG responses through cGAS or STING knockout did not rescue defects in late-viral-protein production, and the experimental data pointed to other functions of mTOR in this regard. mTOR adjusts both autophagic and protein-synthetic processes to cellular demands. No significant differences in autophagic responses to wild-type or F17 mutant viruses could be detected, with autophagic activity differing across cell types or states and exhibiting no correlations with defects in viral-protein accumulation. In contrast, results using transformed cells or altered growth conditions suggested that late-stage defects in protein accumulation reflect failure of the F17 mutant to deregulate mTOR and stimulate protein production. Finally, rescue approaches suggest that phosphorylation may partition F17's functions as a structural protein and mTOR regulator. Our findings reveal the complex multifunctionality of F17 during infection.IMPORTANCE Poxviruses are large, double-stranded DNA viruses that replicate entirely in the cytoplasm, an unusual act that activates pathogen sensors and innate antiviral responses. In order to replicate, poxviruses therefore encode a wide range of innate immune antagonists that include F17, a protein that dysregulates the kinase mammalian target of rapamycin (mTOR) to suppress interferon-stimulated gene (ISG) responses. However, the host sensor(s) that detects infection in the absence of F17 and its precise contribution to infection remains unknown. Here, we show that the cytosolic DNA sensor cGAS is primarily responsible for activating ISG responses in biologically relevant cell types infected with a poxvirus that does not express F17. However, in line with their expression of similar to 100 proteins that act as immune response and ISG antagonists, while F17 helps suppress cGAS-mediated responses, we find that a critical function of its mTOR dysregulation activity is to enhance poxvirus protein production.