title: Inhibition of p-IκBα Ubiquitylation by Autophagy-Related Gene 7 to Regulate Inflammatory Responses to Bacterial Infection.
abstract: BACKGROUND
  Klebsiella pneumoniae causes serious infections and healthcare burdens in humans. We have previously reported that the deficiency of autophagy-related gene (Atg) 7 in macrophages (murine alveolar macrophage cell line [MH-S]) induced irregular host immunity against K. pneumoniae and worsened pathologic effects in the lung. In the current study, we investigated the molecular mechanism by which Atg7 influenced K. pneumoniae-induced inflammatory responses.
  
  
  METHODS
  Expression levels of Atg7, ubiquitin (Ub), and tumor necrosis factor (TNF) α and phosphorylation of IκBα (p-IκBα) were determined with immunoblotting. Ubiquitylation of p-IκBα was determined with immunoprecipitation.
  
  
  RESULTS
  We noted an interaction between Atg7 and p-IκBα, which was decreased in MH-S after K. pneumoniae infection, whereas the interaction between Ub and p-IκBα was increased. Knock-down of Atg7 with small interfering RNA increased p-IκBα ubiquitylation, promoted nuclear factor κB translocation into the nucleus, and increased the production of TNF-α. Moreover, knock-down of Ub with lentivirus-short hairpin RNA Ub particles decreased binding of p-IκBα to Ub and inhibited TNF-α expression in the primary alveolar macrophages and lung tissue of atg7-knockout mice on K. pneumoniae infection.
  
  
  CONCLUSIONS
  Loss of Atg7 switched binding of p-IκBα from Atg7 to Ub, resulting in increased ubiquitylation of p-IκBα and intensified inflammatory responses against K. pneumoniae. Our findings not only reveal a regulatory role of Atg7 in ubiquitylation of p-IκBα but also indicate potential therapeutic targets for K. pneumoniae control.
authors.affiliation: Department of Basic Sciences, School of Medicine and Health Sciences, University of North Dakota, Grand Forks.
authors.forename: Yan
authors.initials: Y
authors.lastname: Ye
authors.affiliation: Department of Basic Sciences, School of Medicine and Health Sciences, University of North Dakota, Grand Forks Laboratory of Biochemistry and Molecular Biology, School of Life Sciences, Yunnan University, Kunming.
authors.forename: Shirui
authors.initials: S
authors.lastname: Tan
authors.affiliation: Department of Basic Sciences, School of Medicine and Health Sciences, University of North Dakota, Grand Forks State Key Laboratory of Biotherapy, Sichuan University, Chengdu, China.
authors.forename: Xikun
authors.initials: X
authors.lastname: Zhou
authors.affiliation: Department of Basic Sciences, School of Medicine and Health Sciences, University of North Dakota, Grand Forks State Key Laboratory of Biotherapy, Sichuan University, Chengdu, China.
authors.forename: Xuefeng
authors.initials: X
authors.lastname: Li
authors.affiliation: Department of Basic Sciences, School of Medicine and Health Sciences, University of North Dakota, Grand Forks.
authors.forename: Michael C
authors.initials: MC
authors.lastname: Jundt
authors.affiliation: Department of Basic Sciences, School of Medicine and Health Sciences, University of North Dakota, Grand Forks.
authors.forename: Natalie
authors.initials: N
authors.lastname: Lichter
authors.affiliation: Department of Basic Sciences, School of Medicine and Health Sciences, University of North Dakota, Grand Forks.
authors.forename: Alec
authors.initials: A
authors.lastname: Hidebrand
authors.affiliation: Department of Basic Sciences, School of Medicine and Health Sciences, University of North Dakota, Grand Forks.
authors.forename: Archana
authors.initials: A
authors.lastname: Dhasarathy
authors.affiliation: Department of Basic Sciences, School of Medicine and Health Sciences, University of North Dakota, Grand Forks.
authors.forename: Min
authors.initials: M
authors.lastname: Wu
mesh_terms: D000818:Animals; D001343:Autophagy / Q000276:immunology; D000071193:Autophagy-Related Protein 7; D002460:Cell Line; D020672:I-kappa B Proteins / Q000378:metabolism*; D007249:Inflammation / Q000276:immunology; D007710:Klebsiella Infections / Q000276:immunology*; D016676:Macrophages, Alveolar / Q000276:immunology / Q000378:metabolism; D051379:Mice; D008822:Mice, Transgenic; D008869:Microtubule-Associated Proteins / Q000378:metabolism*; D015398:Signal Transduction / Q000276:immunology; D051197:Toll-Like Receptor 4; D054875:Ubiquitination / Q000276:immunology*
chemical_list: C502661:Atg7 protein, mouse; D020672:I-kappa B Proteins; D008869:Microtubule-Associated Proteins; C493487:Tlr4 protein, mouse; D051197:Toll-Like Receptor 4; D000071193:Autophagy-Related Protein 7
keywords: IκBα/NF-κB pathway; TLR4; alveolar macrophage; autophagy; ubiquitin