Influenza Virus-Induced Caspase-Dependent Enlargement of Nuclear Pores Promotes Nuclear Export of Viral Ribonucleoprotein Complexes
Influenza Virus-Induced Caspase-Dependent Enlargement of Nuclear Pores Promotes Nuclear Export of Viral Ribonucleoprotein Complexes
复制标题
DOI：
10.1128/jvi.03531-14
复制
发表时间：
2015-06-01
影响因子：
5.4
通讯作者：
Pleschka, Stephan
中科院分区：
文献类型：
--
作者：
Muehlbauer, Dirk;Dzieciolowski, Julia;Pleschka, Stephan
甲型流感病毒(IAV)在感染细胞的细胞核内复制其节段性RNA基因组，并利用caspase依赖的核质输出机制将新形成的核糖核蛋白复合体(RNPs)运送到感染病毒在质膜上释放的位置。在这项研究中，我们获得了证据表明，在IAV感染的细胞中，凋亡的caspase激活与核孔复合体的一个完整的亚基--核孔蛋白Nup153的降解有关。透射电子显微镜研究显示，感染IAV的细胞核孔明显增大。病毒感染细胞中多聚体标记蛋白的瞬时表达和亚细胞积累研究为核孔直径的增加提供了额外的证据，促进了大的蛋白质复合体跨核膜的移位。此外，本研究中获得的caspase 3/7抑制数据表明，主动的、依赖CRM1的IAV RNP输出机制在感染后期越来越多地被被动的、caspase诱导的输出机制所补充。因此，病毒复制周期的完成在很大程度上取决于确保病毒核糖核蛋白(RNP)复合体跨核膜转运的细胞内转运机制。在这里，我们证明了病毒诱导的细胞caspase活性导致核孔扩大，从而促进核质转位过程，并可能促进新合成的RNPs的核输出。这些被动转运机制被认为是对已知发生在复制周期早期阶段的依赖CRM1的RNP输出机制的补充，并可能有助于在病毒复制周期的后期高效生产传染性病毒后代。该报告提供了一个耐人寻味的例子，说明流感病毒如何利用细胞结构和调控途径，包括细胞内运输机制，完成其复制周期，并最大限度地产生传染性病毒后代。
Influenza A viruses (IAV) replicate their segmented RNA genome in the nucleus of infected cells and utilize caspase-dependent nucleocytoplasmic export mechanisms to transport newly formed ribonucleoprotein complexes (RNPs) to the site of infectious virion release at the plasma membrane. In this study, we obtained evidence that apoptotic caspase activation in IAV-infected cells is associated with the degradation of the nucleoporin Nup153, an integral subunit of the nuclear pore complex. Transmission electron microscopy studies revealed a distinct enlargement of nuclear pores in IAV-infected cells. Transient expression and subcellular accumulation studies of multimeric marker proteins in virus-infected cells provided additional evidence for increased nuclear pore diameters facilitating the translocation of large protein complexes across the nuclear membrane. Furthermore, caspase 3/7 inhibition data obtained in this study suggest that active, Crm1-dependent IAV RNP export mechanisms are increasingly complemented by passive, caspase-induced export mechanisms at later stages of infection.IMPORTANCEIn contrast to the process seen with most other RNA viruses, influenza virus genome replication occurs in the nucleus ( rather than the cytoplasm) of infected cells. Therefore, completion of the viral replication cycle critically depends on intracellular transport mechanisms that ensure the translocation of viral ribonucleoprotein ( RNP) complexes across the nuclear membrane. Here, we demonstrate that virus-induced cellular caspase activities cause a widening of nuclear pores, thereby facilitating nucleocytoplasmic translocation processes and, possibly, promoting nuclear export of newly synthesized RNPs. These passive transport mechanisms are suggested to complement Crm1-dependent RNP export mechanisms known to occur at early stages of the replication cycle and may contribute to highly efficient production of infectious virus progeny at late stages of the viral replication cycle. The report provides an intriguing example of how influenza virus exploits cellular structures and regulatory pathways, including intracellular transport mechanisms, to complete its replication cycle and maximize the production of infectious virus progeny.