Inhibition of mTORC1 Enhances the Translation of Chikungunya Proteins via the Activation of the MnK/eIF4E Pathway.
Inhibition of mTORC1 Enhances the Translation of Chikungunya Proteins via the Activation of the MnK/eIF4E Pathway.
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DOI：
10.1371/journal.ppat.1005091
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发表时间：
2015-08
期刊：
影响因子：
6.7
通讯作者：
Albert ML
中科院分区：
文献类型：
--
作者：
Joubert PE;Stapleford K;Guivel-Benhassine F;Vignuzzi M;Schwartz O;Albert ML
基孔肯雅病毒（CHIKV）是跨越五大洲的主要流行病的病原体，是一种正链mRNA病毒，其使用细胞的帽依赖性翻译机制进行复制。尽管病毒感染抑制mTOR，代谢传感器控制帽依赖性翻译，病毒蛋白质被有效翻译。Raptor处理，沉默mtor或raptor基因，但不沉默rictor，进一步增强了培养细胞中的CHIKV感染。使用生化分析和真实的时间成像，我们证明，这种效果是独立的自噬或I型干扰素的生产。为我们的发现的相关性提供体内证据，用mTORC 1抑制剂治疗的小鼠表现出增加的致死率，并显示出对CHIKV更高的敏感性。对病毒生命周期的系统评价表明，抑制mTORC 1对病毒蛋白具有特定的积极作用，通过增加结构和非结构蛋白的翻译来增强病毒复制。分子分析确定了磷脂酰肌醇-3激酶（PI 3 K）和MAP激酶活化蛋白激酶（MnKs）活化的作用，导致eIF 4 E的过度磷酸化。最后，我们证明了在CHIKV抑制mTORC 1的背景下，病毒复制通过类似的机制优先于宿主翻译。我们的研究揭示了一种意想不到的旁路途径，CHIKV蛋白翻译通过该途径克服了病毒诱导的mTORC 1抑制。加勒比海、中美洲和南美洲正在发生的基孔肯雅热疫情突出表明，我们对CHIKV发病机制的理解是多么贫乏，迫切需要限制CHIKV传播的新策略。免疫学研究表明，感染的传播在很大程度上取决于病毒-宿主细胞相互作用的早期事件。在我们之前的研究中，我们研究了I型干扰素反应和自噬途径作为病毒控制介质的作用。在这里，我们评估了mTOR的作用，令人惊讶的发现，抑制mTORC 1独立于I型IFN和自噬增强病毒蛋白翻译。虽然mTORC 1的抑制对病毒结合或进入没有影响，但我们观察到结构和非结构病毒蛋白的翻译增加。有趣的是，mTORC 1抑制的积极影响仅限于病毒蛋白，而宿主帽依赖性蛋白翻译仍然受到抑制。进一步的分析表明，这种旁路途径介导了PI 3 K和MnKs的激活，这反过来又过度磷酸化eIF 4 E，这是翻译的关键起始蛋白。值得注意的是，CHIKV复制使该途径成为有效复制的手段。因此，我们的研究提供了mTORC 1在控制CHIKV感染中的意想不到的作用，并强调了一种新的策略，通过该策略，CHIKV蛋白的表达可以绕过和/或使用mTORC 1的抑制。
Chikungunya virus (CHIKV), the causative agent of a major epidemic spanning five continents, is a positive stranded mRNA virus that replicates using the cell’s cap-dependent translation machinery. Despite viral infection inhibiting mTOR, a metabolic sensor controls cap-dependent translation, viral proteins are efficiently translated. Rapalog treatment, silencing of mtor or raptor genes, but not rictor, further enhanced CHIKV infection in culture cells. Using biochemical assays and real time imaging, we demonstrate that this effect is independent of autophagy or type I interferon production. Providing in vivo evidence for the relevance of our findings, mice treated with mTORC1 inhibitors exhibited increased lethality and showed a higher sensitivity to CHIKV. A systematic evaluation of the viral life cycle indicated that inhibition of mTORC1 has a specific positive effect on viral proteins, enhancing viral replication by increasing the translation of both structural and nonstructural proteins. Molecular analysis defined a role for phosphatidylinositol-3 kinase (PI3K) and MAP kinase-activated protein kinase (MnKs) activation, leading to the hyper-phosphorylation of eIF4E. Finally, we demonstrated that in the context of CHIKV inhibition of mTORC1, viral replication is prioritized over host translation via a similar mechanism. Our study reveals an unexpected bypass pathway by which CHIKV protein translation overcomes viral induced mTORC1 inhibition. The ongoing chikungunya epidemic outbreak in the Caribbean, Central and South America highlights how poor is our understanding of CHIKV pathogenesis and the urgent need for new strategies that may limit CHIKV spread. Immunological studies have suggested that dissemination of infection is largely determined by early events of viral-host cell interactions. In our prior study, we investigated the role of type I interferon responses and the autophagy pathway as mediators of viral control. Here, we evaluated the role of mTOR, making the surprising discovery that inhibition of mTORC1 enhances viral protein translation independently of type I IFN and autophagy. While the inhibition of mTORC1 has no impact on viral binding or entry, we observed an increased translation of both structural and nonstructural viral proteins. Interestingly, the positive impact of mTORC1 inhibition is restricted to viral proteins, as compared to host cap-dependent protein translation that remains suppressed. Further analysis demonstrates that this bypass pathway is mediated the activation of PI3K and MnKs, which in turn hyper-phosphorylate eIF4E, a critical initiation protein for translation. Notably, CHIKV replication enables this pathway as a means to efficiently replicate. Thus, our study provides an unexpected role for mTORC1 in the control of CHIKV infection and highlights a new strategy by which the expression of CHIKV proteins can bypass and/or use the inhibition of mTORC1.