Department of Biology, Indiana University, Bloomington, Indiana, USA.
Department of Biology, Indiana University, Bloomington, Indiana, USA
J Virol. 2019 Apr 17;93(9). doi: 10.1128/JVI.00247-19. Print 2019 May 1.
The environment represents a significant barrier to infection. Physical stressors (heat) or chemical agents (ethanol) can render virions noninfectious. As such, discrete proteins are necessary to stabilize the dual-layered structure of mammalian orthoreovirus (reovirus). The outer capsid participates in cell entry: (i) σ3 is degraded to generate the infectious subviral particle, and (ii) μ1 facilitates membrane penetration and subsequent core delivery. μ1-σ3 interactions also prevent inactivation; however, this activity is not fully characterized. Using forward and reverse genetic approaches, we identified two mutations (μ1 M258I and σ3 S344P) within heat-resistant strains. σ3 S344P was sufficient to enhance capsid integrity and to reduce protease sensitivity. Moreover, these changes impaired replicative fitness in a reassortant background. This work reveals new details regarding the determinants of reovirus stability. Nonenveloped viruses rely on protein-protein interactions to shield their genomes from the environment. The capsid, or protective shell, must also disassemble during cell entry. In this work, we identified a determinant within mammalian orthoreovirus that regulates heat resistance, disassembly kinetics, and replicative fitness. Together, these findings show capsid function is balanced for optimal replication and for spread to a new host.
环境是感染的一个重要障碍。物理应激源（热）或化学剂（乙醇）可使病毒粒子失去感染力。因此，需要离散的蛋白质来稳定哺乳动物正呼肠孤病毒（呼肠孤病毒）的双层结构。外壳参与细胞进入：（i）σ3 被降解以产生感染性亚病毒颗粒，（ii）μ1 促进膜穿透和随后的核心递呈。μ1-σ3 相互作用还可以防止失活；然而，这种活性尚未完全表征。使用正向和反向遗传方法，我们在耐热株中鉴定出两个突变（μ1 M258I 和 σ3 S344P）。σ3 S344P 足以增强衣壳完整性并降低蛋白酶敏感性。此外，这些变化在重组背景下损害了复制适应性。这项工作揭示了呼肠孤病毒稳定性的新细节。无包膜病毒依靠蛋白质-蛋白质相互作用来保护其基因组免受环境影响。衣壳或保护壳在进入细胞时也必须解体。在这项工作中，我们确定了哺乳动物正呼肠孤病毒中调节耐热性、解体动力学和复制适应性的决定因素。这些发现共同表明衣壳功能是为了最佳复制和传播到新宿主而平衡的。
