The Pirbright Institute, Pirbright, Surrey GU24 0NF, UK.
School of Biological Sciences, University of Reading, Reading RG6 6AJ, UK.
Viruses. 2018 Sep 6;10(9):477. doi: 10.3390/v10090477.
Positive-strand RNA viruses, such as coronaviruses, induce cellular membrane rearrangements during replication to form replication organelles allowing for efficient viral RNA synthesis. Infectious bronchitis virus (IBV), a pathogenic avian of significant importance to the global poultry industry, has been shown to induce the formation of double membrane vesicles (DMVs), zippered endoplasmic reticulum (zER) and tethered vesicles, known as spherules. These membrane rearrangements are virally induced; however, it remains unclear which viral proteins are responsible. In this study, membrane rearrangements induced when expressing viral non-structural proteins (nsps) from two different strains of IBV were compared. Three non-structural transmembrane proteins, nsp3, nsp4, and nsp6, were expressed in cells singularly or in combination and the effects on cellular membranes investigated using electron microscopy and electron tomography. In contrast to previously studied coronaviruses, IBV nsp4 alone is necessary and sufficient to induce membrane pairing; however, expression of the transmembrane proteins together was not sufficient to fully recapitulate DMVs. This indicates that although nsp4 is able to singularly induce membrane pairing, further viral or host factors are required in order to fully assemble IBV replicative structures. This study highlights further differences in the mechanism of membrane rearrangements between members of the coronavirus family.
正链 RNA 病毒，如冠状病毒，在复制过程中诱导细胞膜重排，形成复制细胞器，从而实现有效的病毒 RNA 合成。传染性支气管炎病毒（IBV）是对全球家禽业具有重要意义的致病性禽类病原体，已被证明能诱导双层膜囊泡（DMVs）、拉链内质网（zER）和连接囊泡（称为球体）的形成。这些膜重排是病毒诱导的；然而，目前尚不清楚是哪些病毒蛋白负责。在这项研究中，比较了两种不同株系的 IBV 表达病毒非结构蛋白（nsps）时诱导的膜重排。单独或组合表达三种非结构跨膜蛋白 nsp3、nsp4 和 nsp6，并用电子显微镜和电子断层扫描研究它们对细胞膜的影响。与之前研究的冠状病毒不同，IBV nsp4 单独即可诱导膜配对；然而，共表达这些跨膜蛋白不足以完全重现 DMVs。这表明，尽管 nsp4 能够单独诱导膜配对，但为了完全组装 IBV 复制结构，还需要进一步的病毒或宿主因子。这项研究强调了冠状病毒家族成员之间膜重排机制的进一步差异。
