Institute of Molecular Virology, Westfälische-Wilhelms-University, D-48149 Münster, Germany.
FASEB J. 2010 Oct;24(10):4068-77. doi: 10.1096/fj.10-158766. Epub 2010 May 19.
Influenza viruses have to overcome the type I interferon induced antiviral response to successfully propagate in target cells. A major antiviral factor induced by interferons is the protein kinase R (PKR) that is further activated by dsRNA and phosphorylates the eukaryotic initiation factor 2 (eIF2α). This results in inhibition of protein translation thereby limiting viral replication. Here we describe a novel mechanism by which influenza A viruses escape the antiviral action of PKR. We demonstrate that the mitogen-activated protein kinase-activated protein kinases (MAPKAPKs) MK2 and MK3 are activated on virus infection and, in their active form, directly interact with the repressor of the inhibitor of PKR p88(rIPK). This leads to recruitment of a tetrameric protein complex consisting of p88(rIPK), the inhibitor of PKR p58(IPK) and PKR itself, and finally results in inhibition of the kinase. The importance of MKs for influenza virus propagation was further underscored by demonstrating reduced viral progeny in cells genetically deficient in MK2 or MK3 genes as well as in highly proliferating tumor cells, in which expression of MKs was diminished by specific small interfering RNA. Accordingly, knockdown of MKs resulted in enhanced phosphorylation of PKR and its substrate eIF2α.
流感病毒必须克服 I 型干扰素诱导的抗病毒反应，才能在靶细胞中成功繁殖。干扰素诱导的主要抗病毒因子是蛋白激酶 R（PKR），它进一步被双链 RNA 激活，并磷酸化真核起始因子 2（eIF2α）。这导致蛋白质翻译受到抑制，从而限制了病毒的复制。在这里，我们描述了甲型流感病毒逃避 PKR 抗病毒作用的一种新机制。我们证明，有丝分裂原激活蛋白激酶激活的蛋白激酶（MAPKAPKs）MK2 和 MK3 在病毒感染时被激活，并且在其活性形式下，直接与 PKR 抑制剂 p88(rIPK)的抑制剂相互作用。这导致四聚体蛋白复合物的募集，该复合物由 p88(rIPK)、PKR 的抑制剂 p58(IPK)和 PKR 本身组成，最终导致激酶的抑制。MK 对流感病毒繁殖的重要性进一步强调，通过在基因缺陷型 MK2 或 MK3 基因的细胞以及高度增殖的肿瘤细胞中证明病毒后代减少，在这些细胞中，MK 的表达被特定的小干扰 RNA 削弱。因此，MK 的敲低导致 PKR 和其底物 eIF2α 的磷酸化增强。
