title: The type III secretion effector NleF of enteropathogenic Escherichia coli activates NF-κB early during infection.
abstract: The enteric pathogens enteropathogenic Escherichia coli (EPEC) and enterohemorrhagic E. coli employ a type 3 secretion system (T3SS) to manipulate the host inflammatory response during infection. Previously, it has been reported that EPEC, in a T3SS-dependent manner, induces an early proinflammatory response through activation of NF-κB via extracellular signal-regulated kinases 1 and 2 (ERK1/2) and protein kinase Cζ (PKCζ). However, the activation of NF-κB during infection has not yet been attributed to an effector. At later time points postinfection, NF-κB signaling is inhibited through the translocation of multiple effectors, including NleE and NleC. Here we report that the highly conserved non-LEE (locus of enterocyte effacement)-encoded effector F (NleF) shows both diffuse and mitochondrial localization during ectopic expression. Moreover, NleF induces the nuclear translocation of NF-κB p65 and the expression of interleukin 8 (IL-8) following ectopic expression and during EPEC infection. Furthermore, the proinflammatory activity and localization of NleF were dependent on the C-terminal amino acids LQCG. While the C-terminal domain of NleF has previously been shown to be essential for interaction with caspase-4, caspase-8, and caspase-9, the proinflammatory activity of NleF was independent of interaction with caspase-4, -8, or -9. In conclusion, EPEC, through the T3SS-dependent translocation of NleF, induces a proinflammatory response in an NF-κB-dependent manner in the early stages of infection.
authors.affiliation: MRC Centre for Molecular Bacteriology and Infection, Department of Life Sciences, Imperial College London, London, United Kingdom.
authors.forename: Mitchell A
authors.initials: MA
authors.lastname: Pallett
authors.affiliation: MRC Centre for Molecular Bacteriology and Infection, Department of Life Sciences, Imperial College London, London, United Kingdom.
authors.forename: Cedric N
authors.initials: CN
authors.lastname: Berger
authors.affiliation: Department of Microbiology and Immunology, University of Melbourne at the Peter Doherty Institute for Infection and Immunity, Melbourne, Victoria, Australia.
authors.forename: Jaclyn S
authors.initials: JS
authors.lastname: Pearson
authors.affiliation: Department of Microbiology and Immunology, University of Melbourne at the Peter Doherty Institute for Infection and Immunity, Melbourne, Victoria, Australia.
authors.forename: Elizabeth L
authors.initials: EL
authors.lastname: Hartland
authors.affiliation: MRC Centre for Molecular Bacteriology and Infection, Department of Life Sciences, Imperial College London, London, United Kingdom g.frankel@imperial.ac.uk.
authors.forename: Gad
authors.initials: G
authors.lastname: Frankel
mesh_terms: D020169:Caspases / Q000235:genetics / Q000378:metabolism; D054308:Enteropathogenic Escherichia coli / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000276:immunology*; D006367:HeLa Cells; D006801:Humans; D016209:Interleukin-8 / Q000235:genetics / Q000378:metabolism; D008928:Mitochondria; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D015854:Up-Regulation; D037521:Virulence Factors / Q000235:genetics / Q000378:metabolism*
chemical_list: D029968:Escherichia coli Proteins; D016209:Interleukin-8; D016328:NF-kappa B; C583422:NleF protein, E coli; D012333:RNA, Messenger; D037521:Virulence Factors; D020169:Caspases