title: Expression of the nuclear factor-κB inhibitor A20 is altered in the cystic fibrosis epithelium.
abstract: A20 is a lipopolysaccharide (LPS)-inducible, cytoplasmic zinc finger protein, which inhibits Toll-like receptor-activated nuclear factor (NF)-κB signalling by deubiquitinating tumour necrosis factor receptor-associated factor (TRAF)-6. The action of A20 is facilitated by complex formation with ring finger protein (RNF)-11, Itch and TAX-1 binding protein-1 (TAX1BP1). This study investigated whether the expression of A20 is altered in the chronically inflamed cystic fibrosis (CF) airway epithelium. Nasal epithelial cells from CF patients (F508del homozygous), non-CF controls and immortalised epithelial cells (16HBE14o- and CFBE41o-) were stimulated with LPS. Cytoplasmic expression of A20 and expression of NF-κB subunits were analysed. Formation of the A20 ubiquitin editing complex was also investigated. In CFBE41o-, peak LPS-induced A20 expression was delayed compared with 16HBE14o- and fell significantly below basal levels 12-24 h after LPS stimulation. This was confirmed in primary CF airway cells. Additionally, a significant inverse relationship between A20 and p65 expression was observed. Inhibitor studies showed that A20 does not undergo proteasomal degradation in CFBE41o-. A20 interacted with TAX1BP1, RNF11 and TRAF6 in 16HBE14o- cells, but these interactions were not observed in CFBE41o-. The expression of A20 is significantly altered in CF, and important interactions with complex members and target proteins are lost, which may contribute to the state of chronic NF-κB-driven inflammation.
authors.affiliation: Centre for Infection and Immunity, Queen's University of Belfast, Belfast, UK.
authors.forename: Catriona
authors.initials: C
authors.lastname: Kelly
authors.forename: Mark T
authors.initials: MT
authors.lastname: Williams
authors.forename: Kathryn
authors.initials: K
authors.lastname: Mitchell
authors.forename: J Stuart
authors.initials: JS
authors.lastname: Elborn
authors.forename: Madeleine
authors.initials: M
authors.lastname: Ennis
authors.forename: Bettina C
authors.initials: BC
authors.lastname: Schock
mesh_terms: D001980:Bronchi / Q000166:cytology; D002460:Cell Line; D003550:Cystic Fibrosis / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004847:Epithelial Cells / Q000166:cytology / Q000378:metabolism; D004848:Epithelium / Q000378:metabolism*; D005434:Flow Cytometry; D005786:Gene Expression Regulation; D006801:Humans; D007249:Inflammation; D016209:Interleukin-8 / Q000378:metabolism; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism*; D008070:Lipopolysaccharides / Q000378:metabolism; D016328:NF-kappa B / Q000378:metabolism*; D009687:Nuclear Proteins / Q000378:metabolism*; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D017434:Protein Structure, Tertiary; D015398:Signal Transduction; D000072598:Tumor Necrosis Factor alpha-Induced Protein 3
chemical_list: D004268:DNA-Binding Proteins; D016209:Interleukin-8; D047908:Intracellular Signaling Peptides and Proteins; D008070:Lipopolysaccharides; D016328:NF-kappa B; D009687:Nuclear Proteins; C076529:TNFAIP3 protein, human; D000072598:Tumor Necrosis Factor alpha-Induced Protein 3; D046988:Proteasome Endopeptidase Complex