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呼吸道合胞病毒将 NF-κB 亚基 p65 隔离到细胞质包涵体内,以抑制先天免疫信号。

Respiratory Syncytial Virus Sequesters NF-κB Subunit p65 to Cytoplasmic Inclusion Bodies To Inhibit Innate Immune Signaling.

机构信息

The Pirbright Institute, Guildford, Surrey, United Kingdom.

The Pirbright Institute, Guildford, Surrey, United Kingdom

出版信息

J Virol. 2020 Oct 27;94(22). doi: 10.1128/JVI.01380-20.

Abstract

Viruses routinely employ strategies to prevent the activation of innate immune signaling in infected cells. Respiratory syncytial virus (RSV) is no exception, as it encodes two accessory proteins (NS1 and NS2) which are well established to block interferon signaling. However, RSV-encoded mechanisms for inhibiting NF-κB signaling are less well characterized. In this study, we identified RSV-mediated antagonism of this pathway, independent of the NS1 and NS2 proteins and indeed distinct from other known viral mechanisms of NF-κB inhibition. In both human and bovine RSV-infected cells, we demonstrated that the p65 subunit of NF-κB is rerouted to perinuclear puncta in the cytoplasm, which are synonymous with viral inclusion bodies (IBs), the site for viral RNA replication. Captured p65 was unable to translocate to the nucleus or transactivate a NF-κB reporter following tumor necrosis factor alpha (TNF-α) stimulation, confirming the immune-antagonistic nature of this sequestration. Subsequently, we used correlative light electron microscopy (CLEM) to colocalize the RSV N protein and p65 within bovine RSV (bRSV) IBs, which are granular, membraneless regions of cytoplasm with liquid organelle-like properties. Additional characterization of bRSV IBs indicated that although they are likely formed by liquid-liquid phase separation (LLPS), they have a differential sensitivity to hypotonic shock proportional to their size. Together, these data identify a novel mechanism for viral antagonism of innate immune signaling which relies on sequestration of the NF-κB subunit p65 to a biomolecular condensate-a mechanism conserved across the genus and not host-cell specific. More generally, they provide additional evidence that RNA virus IBs are important immunomodulatory complexes within infected cells. Many viruses replicate almost entirely in the cytoplasm of infected cells; however, how these pathogens are able to compartmentalize their life cycle to provide favorable conditions for replication and to avoid the litany of antiviral detection mechanisms in the cytoplasm remains relatively uncharacterized. In this manuscript, we show that bovine respiratory syncytial virus (bRSV), which infects cattle, does this by generating inclusion bodies in the cytoplasm of infected cells. We confirm that both bRSV and human RSV viral RNA replication takes place in these inclusion bodies, likely meaning these organelles are a functionally conserved feature of this group of viruses (the orthopneumoviruses). Importantly, we also showed that these organelles are able to capture important innate immune transcription factors (in this case NF-KB), blocking the normal signaling processes that tell the nucleus the cell is infected, which may help us to understand how these viruses cause disease.

摘要

病毒通常采用策略来防止感染细胞中先天免疫信号的激活。呼吸道合胞病毒 (RSV) 也不例外,因为它编码两种辅助蛋白 (NS1 和 NS2),这些蛋白已被证实可阻断干扰素信号。然而,RSV 抑制 NF-κB 信号的机制尚不清楚。在这项研究中,我们发现 RSV 介导的这条途径的拮抗作用独立于 NS1 和 NS2 蛋白,实际上与其他已知的病毒 NF-κB 抑制机制不同。在人源和牛源 RSV 感染的细胞中,我们证明 NF-κB 的 p65 亚基在细胞质中被重定向到核周点状,这些点状与病毒包涵体 (IB) 同义,后者是病毒 RNA 复制的部位。在肿瘤坏死因子-α (TNF-α) 刺激后,被捕获的 p65 无法易位到细胞核或转激活 NF-κB 报告基因,这证实了这种隔离的免疫拮抗性质。随后,我们使用相关的光电子显微镜 (CLEM) 在牛呼吸道合胞病毒 (bRSV) IB 中对 RSV N 蛋白和 p65 进行共定位,bRSV IB 是细胞质中具有液态细胞器样特性的颗粒状无膜区。对 bRSV IB 的进一步表征表明,尽管它们可能是通过液-液相分离 (LLPS) 形成的,但它们对渗透压冲击的敏感性不同,这与它们的大小成正比。总之,这些数据确定了一种新的病毒拮抗先天免疫信号的机制,该机制依赖于将 NF-κB 亚基 p65 隔离到生物分子凝聚物中,这是一种在属内保守的机制,而不是宿主细胞特异性的。更普遍地说,它们提供了更多证据表明 RNA 病毒包涵体是感染细胞中重要的免疫调节复合物。许多病毒几乎完全在感染细胞的细胞质中复制;然而,这些病原体如何能够将它们的生命周期分隔开来,为复制提供有利条件,并避免细胞质中大量抗病毒检测机制,这仍然相对未知。在本文中,我们表明,感染牛的牛呼吸道合胞病毒 (bRSV) 通过在感染细胞的细胞质中产生包涵体来实现这一点。我们证实,bRSV 和人呼吸道合胞病毒的病毒 RNA 复制都发生在这些包涵体中,这可能意味着这些细胞器是这群病毒(正肺病毒)的一个功能保守特征。重要的是,我们还表明,这些细胞器能够捕获重要的先天免疫转录因子(在这种情况下为 NF-KB),阻断正常的信号转导过程,告知细胞核细胞被感染,这可能有助于我们了解这些病毒如何引起疾病。

https://cdn.ncbi.nlm.nih.gov/pmc/blobs/bdef/7592213/b37dd5d64159/JVI.01380-20-f0001.jpg

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