Lostalé-Seijo Irene, Martínez-Costas José, Benavente Javier
Centro Singular de Investigación en Química Biolóxica e Materiais Moleculares and Departamento de Bioquímica e Bioloxía Molecular, Universidade de Santiago de Compostela, Santiago de Compostela, Spain.
Centro Singular de Investigación en Química Biolóxica e Materiais Moleculares and Departamento de Bioquímica e Bioloxía Molecular, Universidade de Santiago de Compostela, Santiago de Compostela, Spain
J Virol. 2016 Aug 26;90(18):8328-40. doi: 10.1128/JVI.01175-16. Print 2016 Sep 15.
We have previously shown that the replication of avian reovirus (ARV) in chicken cells is much more resistant to interferon (IFN) than the replication of vesicular stomatitis virus (VSV) or vaccinia virus (VV). In this study, we have investigated the role that the double-stranded RNA (dsRNA)-activated protein kinase (PKR) plays in the sensitivity of these three viruses toward the antiviral action of chicken interferon. Our data suggest that while interferon priming of avian cells blocks vaccinia virus replication by promoting PKR activation, the replication of vesicular stomatitis virus appears to be blocked at a pretranslational step. Our data further suggest that the replication of avian reovirus in chicken cells is quite resistant to interferon priming because this virus uses strategies to downregulate PKR activation and also because translation of avian reovirus mRNAs is more resistant to phosphorylation of the alpha subunit of initiation factor eIF2 than translation of their cellular counterparts. Our results further reveal that the avian reovirus protein sigmaA is able to prevent PKR activation and that this function is dependent on its double-stranded RNA-binding activity. Finally, this study demonstrates that vaccinia virus and avian reovirus, but not vesicular stomatitis virus, express/induce factors that counteract the ability of dithiothreitol to promote eIF2 phosphorylation. Our data demonstrate that each of the three different viruses used in this study elicits distinct responses to interferon and to dithiothreitol-induced eIF2 phosphorylation when infecting avian cells.
Type I interferons constitute the first barrier of defense against viral infections, and one of the best characterized antiviral strategies is mediated by the double-stranded RNA-activated protein kinase R (PKR). The results of this study revealed that IFN priming of avian cells has little effect on avian reovirus (ARV) replication but drastically diminishes the replication of vaccinia virus (VV) and vesicular stomatitis virus (VSV) by PKR-dependent and -independent mechanisms, respectively. Our data also demonstrate that the dsRNA-binding ability of ARV protein sigmaA plays a key role in the resistance of ARV toward IFN by preventing PKR activation. Our findings will contribute to improve the current understanding of the interaction of viruses with the host's innate immune system. Finally, it would be of interest to uncover the mechanisms that allow avian reovirus transcripts to be efficiently translated under conditions (moderate eIF2 phosphorylation) that block the synthesis of cellular proteins.
我们之前已经表明，禽呼肠孤病毒（ARV）在鸡细胞中的复制比水泡性口炎病毒（VSV）或痘苗病毒（VV）的复制对干扰素（IFN）更具抗性。在本研究中，我们研究了双链RNA（dsRNA）激活的蛋白激酶（PKR）在这三种病毒对鸡干扰素抗病毒作用的敏感性中所起的作用。我们的数据表明，虽然禽类细胞的干扰素预处理通过促进PKR激活来阻断痘苗病毒的复制，但水泡性口炎病毒的复制似乎在翻译前步骤被阻断。我们的数据进一步表明，禽呼肠孤病毒在鸡细胞中的复制对干扰素预处理具有相当的抗性，因为这种病毒采用策略下调PKR激活，并且还因为禽呼肠孤病毒mRNA的翻译比其细胞对应物的翻译对起始因子eIF2α亚基的磷酸化更具抗性。我们的结果进一步揭示，禽呼肠孤病毒蛋白sigmaA能够阻止PKR激活，并且该功能依赖于其双链RNA结合活性。最后，本研究表明痘苗病毒和禽呼肠孤病毒，但不是水泡性口炎病毒，表达/诱导抵消二硫苏糖醇促进eIF2磷酸化能力的因子。我们的数据表明，本研究中使用的三种不同病毒在感染禽类细胞时对干扰素和二硫苏糖醇诱导的eIF2磷酸化引发不同的反应。
I型干扰素构成了对抗病毒感染的第一道防线，并且最具特征的抗病毒策略之一是由双链RNA激活的蛋白激酶R（PKR）介导的。本研究结果表明，禽类细胞的IFN预处理对禽呼肠孤病毒（ARV）复制几乎没有影响，但分别通过PKR依赖性和非依赖性机制显著降低痘苗病毒（VV）和水泡性口炎病毒（VSV）的复制。我们的数据还表明，ARV蛋白sigmaA的dsRNA结合能力通过阻止PKR激活在ARV对IFN的抗性中起关键作用。我们的发现将有助于增进目前对病毒与宿主先天免疫系统相互作用的理解。最后，揭示允许禽呼肠孤病毒转录本在阻断细胞蛋白合成的条件（适度的eIF2磷酸化）下有效翻译的机制将是有意义的。
