title: Influenza A virus PB1-F2 is involved in regulation of cellular redox state in alveolar epithelial cells.
abstract: 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.
authors.affiliation: Department of Life Sciences, Korea University, Seoul 136-701, Republic of Korea.
authors.forename: Nary
authors.initials: N
authors.lastname: Shin
authors.affiliation: Department of Life Sciences, Korea University, Seoul 136-701, Republic of Korea.
authors.forename: Chul-Woong
authors.initials: CW
authors.lastname: Pyo
authors.affiliation: Department of Life Sciences, Korea University, Seoul 136-701, Republic of Korea.
authors.forename: Kwang Il
authors.initials: KI
authors.lastname: Jung
authors.affiliation: Department of Life Sciences, Korea University, Seoul 136-701, Republic of Korea. Electronic address: sychoi@korea.ac.kr.
authors.forename: Sang-Yun
authors.initials: SY
authors.lastname: Choi
mesh_terms: D000818:Animals; D002460:Cell Line; D004285:Dogs; D006801:Humans; D061985:Madin Darby Canine Kidney Cells; D010084:Oxidation-Reduction; D011650:Pulmonary Alveoli / Q000166:cytology / Q000201:enzymology / Q000378:metabolism*; D017382:Reactive Oxygen Species / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013482:Superoxide Dismutase / Q000378:metabolism; D000072105:Superoxide Dismutase-1; D014764:Viral Proteins / Q000502:physiology*
chemical_list: C442816:PB1-F2 protein, Influenza A virus; D017382:Reactive Oxygen Species; C000606290:SOD1 protein, human; D014764:Viral Proteins; D013482:Superoxide Dismutase; D000072105:Superoxide Dismutase-1
keywords: Apoptosis; Influenza A virus; PB1-F2; ROS; Superoxide anion dismutase 1