Inhibition of p-I?B? Ubiquitylation by Autophagy-Related Gene 7 to Regulate Inflammatory Responses to Bacterial Infection.

ABSTRACT: 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.Expression levels of Atg7, ubiquitin (Ub), and tumor necrosis factor (TNF) ? and phosphorylation of I?B? (p-I?B?) were determined with immunoblotting. Ubiquitylation of p-I?B? was determined with immunoprecipitation.We noted an interaction between Atg7 and p-I?B?, which was decreased in MH-S after K. pneumoniae infection, whereas the interaction between Ub and p-I?B? was increased. Knock-down of Atg7 with small interfering RNA increased p-I?B? ubiquitylation, promoted nuclear factor ?B translocation into the nucleus, and increased the production of TNF-?. Moreover, knock-down of Ub with lentivirus-short hairpin RNA Ub particles decreased binding of p-I?B? to Ub and inhibited TNF-? expression in the primary alveolar macrophages and lung tissue of atg7-knockout mice on K. pneumoniae infection.Loss of Atg7 switched binding of p-I?B? from Atg7 to Ub, resulting in increased ubiquitylation of p-I?B? and intensified inflammatory responses against K. pneumoniae. Our findings not only reveal a regulatory role of Atg7 in ubiquitylation of p-I?B? but also indicate potential therapeutic targets for K. pneumoniae control.

SUBMITTER: Ye Y 

PROVIDER: S-EPMC4633763 | biostudies-literature | 2015 Dec

REPOSITORIES: biostudies-literature