Department of Biology, Indiana University, Bloomington, Indiana, USA.
Department of Biology, Indiana University, Bloomington, Indiana, USA
J Virol. 2019 May 15;93(11). doi: 10.1128/JVI.00199-19. Print 2019 Jun 1.
The reovirus outer capsid protein μ1 regulates cell death in infected cells. To distinguish between the roles of incoming, capsid-associated, and newly synthesized μ1, we used small interfering RNA (siRNA)-mediated knockdown. Loss of newly synthesized μ1 protein does not affect apoptotic cell death in HeLa cells but enhances necroptosis in L929 cells. Knockdown of μ1 also affects aspects of viral replication. We found that, while μ1 knockdown results in diminished release of infectious viral progeny from infected cells, viral minus-strand RNA, plus-strand RNA, and proteins that are not targeted by the μ1 siRNA accumulate to a greater extent than in control siRNA-treated cells. Furthermore, we observed a decrease in sensitivity of these viral products to inhibition by guanidine hydrochloride (GuHCl) (which targets minus-strand synthesis to produce double-stranded RNA) when μ1 is knocked down. Following μ1 knockdown, cell death is also less sensitive to treatment with GuHCl. Our studies suggest that the absence of μ1 allows enhanced transcriptional activity of newly synthesized cores and the consequent accumulation of viral gene products. We speculate that enhanced accumulation and detection of these gene products due to μ1 knockdown potentiates receptor-interacting protein 3 (RIP3)-dependent cell death. We used mammalian reovirus as a model to study how virus infections result in cell death. Here, we sought to determine how viral factors regulate cell death. Our work highlights a previously unknown role for the reovirus outer capsid protein μ1 in limiting the induction of a necrotic form of cell death called necroptosis. Induction of cell death by necroptosis requires the detection of viral gene products late in infection; μ1 limits cell death by this mechanism because it prevents excessive accumulation of viral gene products that trigger cell death.
呼肠孤病毒外壳蛋白 μ1 调节感染细胞中的细胞死亡。为了区分进入、衣壳相关和新合成的 μ1 的作用，我们使用小干扰 RNA (siRNA) 介导的敲低。新合成的 μ1 蛋白的缺失不会影响 HeLa 细胞中的细胞凋亡，但会增强 L929 细胞中的坏死性细胞死亡。μ1 的敲低也会影响病毒复制的各个方面。我们发现，虽然 μ1 的敲低导致感染细胞中释放的传染性病毒后代减少，但与对照 siRNA 处理的细胞相比，μ1 敲低的细胞中病毒负链 RNA、正链 RNA 和不受 μ1 siRNA 靶向的蛋白质积累的程度更大。此外，我们观察到当 μ1 被敲低时，这些病毒产物对胍盐酸盐 (GuHCl) 的敏感性降低（GuHCl 靶向负链合成以产生双链 RNA）。μ1 敲低后，细胞死亡对 GuHCl 的敏感性也降低。我们的研究表明，μ1 的缺失允许新合成的核心的转录活性增强，从而导致病毒基因产物的积累。我们推测，由于 μ1 的敲低，这些基因产物的积累和检测增加，从而增强了受体相互作用蛋白 3 (RIP3) 依赖性细胞死亡。我们使用哺乳动物呼肠孤病毒作为模型来研究病毒感染如何导致细胞死亡。在这里，我们试图确定病毒因素如何调节细胞死亡。我们的工作强调了呼肠孤病毒外壳蛋白 μ1 在限制诱导一种称为坏死性细胞死亡的坏死形式中的未知作用。通过坏死性细胞死亡诱导细胞死亡需要在感染后期检测病毒基因产物；μ1 通过这种机制限制细胞死亡，因为它阻止了触发细胞死亡的病毒基因产物的过度积累。
