title: Proteasome-independent degradation of canonical NFkappaB complex components by the NleC protein of pathogenic Escherichia coli.
abstract: The NFκB transcription factor is a key component of immune and inflammatory signaling as its activation induces the expression of antimicrobial reagents, chemokines, cytokines, and anti-apoptotic factors. Many pathogens encode effector proteins that target factors regulating NFκB activity and can provide novel insights on regulatory mechanisms. Given the link of NFκB dysfunction with inflammatory diseases and some cancers, these effectors have therapeutic potential. Here, screening enteropathogenic Escherichia coli proteins for those implicated in suppressing NFκB function revealed that eGFP-NleC, unlike eGFP, strongly inhibited basal and TNFα-induced NFκB reporter activity to prevent secretion of the chemokine, IL-8. Work involving NleC variants, chemical inhibitors, and immunoprecipitation studies support NleC being a zinc metalloprotease that degrades NFκB-IκBα complexes. The findings are consistent with features between residues 33-65 recruiting NFκB for proteasomal-independent degradation by a mechanism inhibited by metalloprotease inhibitors or disruption of a consensus zinc metalloprotease motif spanning NleC residues 183-187. This raises the prospect that mammalian cells, or other pathogens, employ a similar mechanism to modulate NFκB activity. Moreover, NleC represents a novel tool for validating NFκB as a therapeutic target and, indeed, as a possible therapeutic reagent.
authors.affiliation: Institute for Cell and Molecular Biosciences, Newcastle University Medical School, Newcastle-upon-Tyne NE2 4HH, United Kingdom.
authors.forename: Sabrina
authors.initials: S
authors.lastname: Mühlen
authors.forename: Marie-Hélène
authors.initials: MH
authors.lastname: Ruchaud-Sparagano
authors.forename: Brendan
authors.initials: B
authors.lastname: Kenny
mesh_terms: D054308:Enteropathogenic Escherichia coli / Q000201:enzymology* / Q000235:genetics; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D016209:Interleukin-8 / Q000378:metabolism / Q000494:pharmacology; D008666:Metalloendopeptidases / Q000235:genetics / Q000378:metabolism*; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism*; D046988:Proteasome Endopeptidase Complex; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism / Q000494:pharmacology
chemical_list: C508606:CXCL8 protein, human; D029968:Escherichia coli Proteins; D016209:Interleukin-8; D016328:NF-kappa B; D014409:Tumor Necrosis Factor-alpha; C506688:Z0986 protein, E coli; D008666:Metalloendopeptidases; D046988:Proteasome Endopeptidase Complex