Endoplasmic reticulum-associated degradation potentiates the infectivity of influenza A virus by regulating the host redox state

• Published in: Free radical biology & medicine Vol. 135; pp. 293 - 305
• Main Authors: Jung, Kwang Il, Ko, Dong-Hyun, Shin, Nary, Pyo, Chul Woong, Choi, Sang-Yun
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.05.2019
• Subjects: A549 Cells; Animals; Endoplasmic Reticulum - metabolism; Endoplasmic Reticulum - pathology; Endoplasmic Reticulum Stress - genetics; Endoplasmic Reticulum-Associated Degradation - genetics; Endoribonucleases - genetics; ER stress; Fibroblasts - drug effects; Fibroblasts - metabolism; Humans; Influenza; Influenza A virus - metabolism; Influenza A virus - pathogenicity; Influenza, Human - genetics; Influenza, Human - metabolism; Influenza, Human - pathology; Influenza, Human - virology; MAP Kinase Signaling System - drug effects; Mice; Oxidation-Reduction - drug effects; Phenylbutyrates - pharmacology; Protein Serine-Threonine Kinases - genetics; Reactive Oxygen Species - metabolism; ROS; SOD1; Sp1 Transcription Factor - genetics; Superoxide Dismutase-1 - genetics; X-Box Binding Protein 1 - genetics; ER stress; Influenza; ROS; SOD1
• ISSN: 0891-5849; 1873-4596
• DOI: 10.1016/j.freeradbiomed.2019.03.021

During influenza A virus (IAV) infection, significant effects of oxidative stress often emerge due to the disruption of the redox balance. Reactive oxygen species (ROS) generated during IAV infection have been known to exert various effects on both the virus and host tissue. However, the mechanisms underlying the accumulation of ROS and their physiological significance in IAV infection have been extensively studied but remain to be fully understood. Here, we show that the levels of Sp1, a key controller of Cu-Zn superoxide dismutase (SOD1) gene expression, and SOD1 are mainly dependent upon the activity of X-box–binding protein 1 (XBP1), which is a downstream factor of the endoplasmic reticulum (ER) transmembrane sensor inositol-requiring enzyme 1 (IRE1) during ER stress. In IRE1-deficient mouse embryo fibroblasts (MEFs) or A549 human lung cells treated with XBP1 siRNA, IAV-induced Sp1 loss was mitigated. However, overexpression of the spliced form of XBP1 in IRE1-deficient MEFs resulted in a further decrease in Sp1 levels, whereas the unspliced form showed no significant differences. Treatment with proteasome inhibitor MG132 markedly inhibited the IRE1/XBP1-mediated loss of Sp1 and SOD, suggesting the involvement of proteasome-dependent ER-associated degradation (ERAD). The increase in SOD1 levels with the expression of siRNA-targeting p97, a central component of the ubiquitin–proteasome system, supports the major role of the ERAD process in IAV-mediated SOD1 loss. In addition, ROS generation due to IAV infection was attenuated in cells lacking either IRE1 or JNK. These results reveal the important roles of both IRE1/XBP1-mediated ERAD and the JNK pathway in IAV infection. Interestingly, the increase in ROS due to IAV infection is correlated with the increase in the virus titer in vitro and in vivo. However, 4-phenylbutyrate (4-PBA), an inhibitor of ER stress signaling, weakened the effect of IAV infection on SOD1 loss in a dose-dependent manner. Furthermore, the treatment of mice with 4-PBA efficiently attenuated ROS generation and ER stress in lung tissue and eventually lowered the IAV titer. These results strongly suggest that the ERAD process plays a major role in IAV infection, thus making it a potential target for antiviral drug therapy. [Display omitted] •IRE1/XBP1-mediated ERAD is induced during influenza A virus (IAV) infection.•ERAD contributes to SOD1 down-regulation, raising ROS levels in IAV-infected cells.•Cells lacking either IRE1 or JNK were impaired in terms of IAV-induced ROS generation.•Oxidative stress and JNK activation are implicated in IAV infectivity in vitro.•Treatment with 4-PBA attenuates ROS generation and lowers the IAV titer in mice.