title: Inhibition of NF-κB signaling in human dendritic cells by the enteropathogenic Escherichia coli effector protein NleE.
abstract: Intestinal dendritic cells (DCs) send processes between epithelial cells into the gut lumen to sample pathogens. Noninvasive enteropathogenic Escherichia coli (EPEC) colonize the gut using a type three secretion system (T3SS) to inject effector proteins into epithelial cells. We hypothesized that EPEC might also inject proteins into DC processes to dampen immune recognition. Using a T3SS-linked fluorescence resonance energy transfer-based system we show that EPEC injects effectors into in vitro grown human myeloid DCs. Injected cells emit a blue signal due to cleavage of the green fluorescence resonance energy transfer-based substrate CCF2/AM by β-lactamase. When cultured with a mutant EPEC unable to translocate effector proteins, myeloid DCs show rapid activation of NF-κB, secrete large amounts of proinflammatory cytokines and increase expression of CD80, CD83, and CD86, whereas wild-type EPEC barely elicits cytokine production and shuts off nuclear translocation of NF-κB p65. By deleting effector protein genes, we identified NleE as being critical for this effect. Expression of NleE in HeLa cells completely prevented nuclear p65 accumulation in response to IL1-β, and luciferase production in an NF-κB reporter cell line. DCs cocultured with wild-type EPEC or NleE-complemented strains were less potent at inducing MLR. EPEC was also able to inject effectors into DCs sending processes through model gut epithelium in a transwell system and into Peyer's patch myeloid DCs. Thus, EPEC translocate effectors into human DCs to dampen the inflammatory response elicited by its own pathogen-associated molecular patterns.
authors.affiliation: Institute of Cell and Molecular Science, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, Whitechapel, London. a.vossenkaemper@qmul.ac.uk
authors.forename: Anna
authors.initials: A
authors.lastname: Vossenkämper
authors.forename: Olivier
authors.initials: O
authors.lastname: Marchès
authors.forename: Peter D
authors.initials: PD
authors.lastname: Fairclough
authors.forename: Gary
authors.initials: G
authors.lastname: Warnes
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Stagg
authors.forename: James O
authors.initials: JO
authors.lastname: Lindsay
authors.forename: Paul C
authors.initials: PC
authors.lastname: Evans
authors.forename: Le A
authors.initials: le A
authors.lastname: Luong
authors.forename: Nicholas M
authors.initials: NM
authors.lastname: Croft
authors.forename: Sandhia
authors.initials: S
authors.lastname: Naik
authors.forename: Gad
authors.initials: G
authors.lastname: Frankel
authors.forename: Thomas T
authors.initials: TT
authors.lastname: MacDonald
mesh_terms: D015153:Blotting, Western; D002469:Cell Separation; D018920:Coculture Techniques; D003713:Dendritic Cells / Q000276:immunology / Q000378:metabolism / Q000382:microbiology*; D054308:Enteropathogenic Escherichia coli / Q000276:immunology / Q000378:metabolism / Q000472:pathogenicity*; D004797:Enzyme-Linked Immunosorbent Assay; D004927:Escherichia coli Infections / Q000276:immunology / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000276:immunology / Q000378:metabolism*; D005434:Flow Cytometry; D005455:Fluorescent Antibody Technique; D006367:HeLa Cells; D006801:Humans; D007959:Lymphocyte Culture Test, Mixed; D018613:Microscopy, Confocal; D016328:NF-kappa B / Q000276:immunology / Q000378:metabolism*; D015398:Signal Transduction / Q000276:immunology*; D037521:Virulence Factors / Q000276:immunology / Q000378:metabolism*
chemical_list: D029968:Escherichia coli Proteins; D016328:NF-kappa B; C526043:NleE protein, E coli; D037521:Virulence Factors