The murine cytomegalovirus M35 protein antagonizes type I IFN induction downstream of pattern recognition receptors by targeting NF-κB mediated transcription.
The murine cytomegalovirus M35 protein antagonizes type I IFN induction downstream of pattern recognition receptors by targeting NF-κB mediated transcription.
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DOI：
10.1371/journal.ppat.1006382
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发表时间：
2017-05
期刊：
影响因子：
6.7
通讯作者：
Brinkmann MM
中科院分区：
文献类型：
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作者：
Chan B;Gonçalves Magalhães V;Lemmermann NAW;Juranić Lisnić V;Stempel M;Bussey KA;Reimer E;Podlech J;Lienenklaus S;Reddehase MJ;Jonjić S;Brinkmann MM
I型干扰素（IFN）应答对于建立早期抗病毒免疫应答是必要的。在这里，我们报告的第一个I型IFN拮抗剂的识别编码的小鼠巨细胞病毒（MCMV），关闭信号模式识别受体（PRR）传感。MCMV开放阅读框（ORF）文库筛选鉴定M35为一种新型的强负性调节因子，可在RNA和DNA胞质PRR激活后诱导IFNβ启动子。此外，M35抑制Toll样受体（TLR）下游的促炎细胞因子反应。使用一系列具有特异性转录因子结合位点的基于内切酶的报告基因，我们确定M35靶向NF-κB介导的转录，而不是IRF介导的转录。永生化骨髓源性巨噬细胞（iBMDM）逆转录病毒转导后M35的表达导致IFNβ转录和分泌在IFN基因刺激因子（STING）依赖性信号转导激活后减少。另一方面，M35不拮抗干扰素刺激基因（ISG）56启动子诱导或ISG转录后，外源刺激的I型IFN受体（IFNAR）。M35存在于病毒颗粒中，并且在MCMV感染成纤维细胞后，立即穿梭至细胞核，在细胞核中发挥其免疫调节作用。从MCMV基因组中删除M35并因此从病毒颗粒中删除M35导致体外和体内I型IFN转录和分泌升高。在不存在M35的情况下，在宿主的急性感染期间观察到较低的病毒滴度，并且未检测到唾液腺中的生产性感染。总之，MCMV感染后立即释放M35蛋白，以通过靶向NF-κ B介导的转录巧妙地抑制抗病毒I型IFN应答。这种新型病毒蛋白的鉴定加强了在病毒与宿主之间复杂关系中及时采取对策的重要性。疱疹病毒巨细胞病毒可导致免疫抑制人群的严重发病率，并且在先天性感染的背景下比寨卡病毒造成更大的全球性问题。为了建立感染，巨细胞病毒需要调节其宿主的抗病毒免疫应答。对抗病毒感染的第一道防线之一是I型干扰素反应，它由称为模式识别受体的细胞传感器激活。这些受体感知病毒进入并快速诱导I型干扰素的转录，I型干扰素有助于在感染细胞和周围细胞中诱导抗病毒状态。我们已经确定了第一个由鼠巨细胞病毒编码的病毒蛋白，M35蛋白，其抵消多个模式识别受体下游的I型干扰素转录。我们发现，这种病毒对策发生在病毒进入宿主细胞后不久，因为M35与病毒颗粒一起递送。然后M35定位于细胞核，在那里它调节NF-κ B介导的转录。在体内，缺乏M35蛋白的鼠巨细胞病毒在脾脏和肝脏中复制至较低水平，并且不能在唾液腺中建立生产性感染，唾液腺是病毒传播的关键部位，这突出了M35在建立感染中的重要作用。我们的研究为巨细胞病毒与宿主先天免疫反应之间的复杂相互作用提供了新的见解。
The type I interferon (IFN) response is imperative for the establishment of the early antiviral immune response. Here we report the identification of the first type I IFN antagonist encoded by murine cytomegalovirus (MCMV) that shuts down signaling following pattern recognition receptor (PRR) sensing. Screening of an MCMV open reading frame (ORF) library identified M35 as a novel and strong negative modulator of IFNβ promoter induction following activation of both RNA and DNA cytoplasmic PRR. Additionally, M35 inhibits the proinflammatory cytokine response downstream of Toll-like receptors (TLR). Using a series of luciferase-based reporters with specific transcription factor binding sites, we determined that M35 targets NF-κB-, but not IRF-mediated, transcription. Expression of M35 upon retroviral transduction of immortalized bone marrow-derived macrophages (iBMDM) led to reduced IFNβ transcription and secretion upon activation of stimulator of IFN genes (STING)-dependent signaling. On the other hand, M35 does not antagonize interferon-stimulated gene (ISG) 56 promoter induction or ISG transcription upon exogenous stimulation of the type I IFN receptor (IFNAR). M35 is present in the viral particle and, upon MCMV infection of fibroblasts, is immediately shuttled to the nucleus where it exerts its immunomodulatory effects. Deletion of M35 from the MCMV genome and hence from the viral particle resulted in elevated type I IFN transcription and secretion in vitro and in vivo. In the absence of M35, lower viral titers are observed during acute infection of the host, and productive infection in the salivary glands was not detected. In conclusion, the M35 protein is released by MCMV immediately upon infection in order to deftly inhibit the antiviral type I IFN response by targeting NF-κB-mediated transcription. The identification of this novel viral protein reinforces the importance of timely countermeasures in the complex relationship between virus and host. The herpesvirus cytomegalovirus can cause severe morbidity in immunosuppressed people and poses a much greater global problem in the context of congenital infections than the Zika virus. To establish infection, cytomegalovirus needs to modulate the antiviral immune response of its host. One of the first lines of defense against viral infections is the type I interferon response which is activated by cellular sensors called pattern recognition receptors. These receptors sense viral entry and rapidly induce the transcription of type I interferons, which are instrumental for the induction of an antiviral state in infected and surrounding cells. We have identified the first viral protein encoded by murine cytomegalovirus, the M35 protein, that counteracts type I interferon transcription downstream of multiple pattern recognition receptors. We found that this viral countermeasure occurs shortly after viral entry into the host cell, as M35 is delivered with the viral particle. M35 then localizes to the nucleus where it modulates NF-κB-mediated transcription. In vivo, murine cytomegalovirus deficient of the M35 protein replicates to lower levels in spleen and liver and cannot establish a productive infection in the salivary glands, which is a key site of viral transmission, highlighting the important role of M35 for the establishment of infection. Our study provides novel insights into the complex interaction between cytomegalovirus and the innate immune response of its host.