Shin Nary, Pyo Chul-Woong, Jung Kwang Il, Choi Sang-Yun
Department of Life Sciences, Korea University, Seoul 136-701, Republic of Korea.
Department of Life Sciences, Korea University, Seoul 136-701, Republic of Korea.
Biochem Biophys Res Commun. 2015 Apr 17;459(4):699-705. doi: 10.1016/j.bbrc.2015.03.010. Epub 2015 Mar 11.
Occurrence of oxidative stress is common in influenza, and renders the host more susceptible to pathogenic effects including cell death. We previously reported that down-regulation of superoxide anion dismutase 1 (SOD1) by influenza A virus (IAV) resulted in a significant increase in the levels of reactive oxygen species (ROS) and viral PB1 polymerase gene product in the early stage of infection. However, the precise molecular mechanism of IAV-mediated ROS generation is not yet fully understood. In this study, we investigated the possible involvement of the key virulence factor PB1-F2 in ROS generation and its contribution to the viral propagation and cell death. The key virulence factor PB1-F2 was found to be responsible, at least in part, for the ROS generation through lowering the SOD1 level in alveolar epithelial A549 cells. PB1-F2 overexpression resulted in SOD1 diminishment and ROS enhancement, while another virulent factor, NS1, did not show significant changes. Inversely, we examined the effects of the absence of PB1-F2 using mutant IAV lacking PB1-F2 expression (mutantΔF2). Infection with mutantΔF2 virus did not significantly lower the SOD1 level, and thus generated moderately low levels of ROS. In addition, the oxidative activity of PB1-F2 was directly reflected by cell viability and death. Infection with the mutant virus reduced the percentage of apoptotic cells more than two-fold compared to the wild-type IAV in A549 cells. Furthermore, expression of exogenous SOD1 gene abrogated a large portion of the PB1-F2-induced apoptosis of cells infected with wild-type IAV, but affected much less of the mutantΔF2 virus-infected cells. These results suggest that the PB1-F2 is directly implicated in virus-induced oxidative stress, thereby contributing to the early stages of IAV replication cycle and ultimately to disease severity.
氧化应激在流感中很常见，会使宿主更容易受到包括细胞死亡在内的致病影响。我们之前报道过，甲型流感病毒（IAV）下调超氧化物歧化酶1（SOD1）会导致感染早期活性氧（ROS）水平和病毒PB1聚合酶基因产物显著增加。然而，IAV介导的ROS产生的确切分子机制尚未完全阐明。在本研究中，我们调查了关键毒力因子PB1-F2在ROS产生中的可能作用及其对病毒传播和细胞死亡的影响。发现关键毒力因子PB1-F2至少部分负责通过降低肺泡上皮A549细胞中的SOD1水平来产生ROS。PB1-F2过表达导致SOD1减少和ROS增加，而另一个毒力因子NS1则没有显著变化。相反，我们使用缺乏PB1-F2表达的突变IAV（突变体ΔF2）研究了PB1-F2缺失的影响。用突变体ΔF2病毒感染不会显著降低SOD1水平，因此产生的ROS水平适中较低。此外，PB1-F2的氧化活性直接反映在细胞活力和死亡上。与野生型IAV相比，用突变病毒感染使A549细胞中凋亡细胞的百分比降低了两倍多。此外，外源性SOD1基因的表达消除了野生型IAV感染细胞中大部分PB1-F2诱导的细胞凋亡，但对突变体ΔF2病毒感染细胞的影响要小得多。这些结果表明，PB1-F2直接参与病毒诱导的氧化应激，从而促进IAV复制周期的早期阶段，并最终影响疾病严重程度。
