The type III effectors NleE and NleB from enteropathogenic E. coli and OspZ from Shigella block nuclear translocation of NF-kappaB p65.
Many bacterial pathogens utilize a type III secretion system to deliver multiple effector proteins into host cells. Here we found that the type III effectors, NleE from enteropathogenic E. coli (EPEC) and OspZ from Shigella, blocked translocation of the p65 subunit of the transcription factor, NF-kappaB, to the host cell nucleus. NF-kappaB inhibition by NleE was associated with decreased IL-8 expression in EPEC-infected intestinal epithelial cells. Ectopically expressed NleE also blocked nuclear translocation of p65 and c-Rel, but not p50 or STAT1/2. NleE homologues from other attaching and effacing pathogens as well OspZ from Shigella flexneri 6 and Shigella boydii, also inhibited NF-kappaB activation and p65 nuclear import; however, a truncated form of OspZ from S. flexneri 2a that carries a 36 amino acid deletion at the C-terminus had no inhibitory activity. We determined that the C-termini of NleE and full length OspZ were functionally interchangeable and identified a six amino acid motif, IDSY(M/I)K, that was important for both NleE- and OspZ-mediated inhibition of NF-kappaB activity. We also established that NleB, encoded directly upstream from NleE, suppressed NF-kappaB activation. Whereas NleE inhibited both TNFalpha and IL-1beta stimulated p65 nuclear translocation and IkappaB degradation, NleB inhibited the TNFalpha pathway only. Neither NleE nor NleB inhibited AP-1 activation, suggesting that the modulatory activity of the effectors was specific for NF-kappaB signaling. Overall our data show that EPEC and Shigella have evolved similar T3SS-dependent means to manipulate host inflammatory pathways by interfering with the activation of selected host transcriptional regulators.
Newton
Hayley J
HJ
Department of Microbiology and Immunology, University of Melbourne, Parkville, Victoria, Australia.
Pearson
Jaclyn S
JS
Badea
Luminita
L
Kelly
Michelle
M
Lucas
Mark
M
Holloway
Gavan
G
Wagstaff
Kylie M
KM
Dunstone
Michelle A
MA
Sloan
Joan
J
Whisstock
James C
JC
Kaper
James B
JB
Robins-Browne
Roy M
RM
Jans
David A
DA
Frankel
Gad
G
Phillips
Alan D
AD
Coulson
Barbara S
BS
Hartland
Elizabeth L
EL
D021581:Active Transport, Cell Nucleus / Q000502:physiology; D018938:Caco-2 Cells; D004405:Dysentery, Bacillary / Q000276:immunology / Q000378:metabolism / Q000382:microbiology; D004927:Escherichia coli Infections / Q000276:immunology / Q000378:metabolism / Q000382:microbiology; D019453:Escherichia coli O157 / Q000378:metabolism* / Q000472:pathogenicity; D029968:Escherichia coli Proteins / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D020672:I-kappa B Proteins / Q000378:metabolism; D016209:Interleukin-8 / Q000235:genetics / Q000378:metabolism; D007413:Intestinal Mucosa / Q000276:immunology / Q000382:microbiology; D052002:NF-kappa B p50 Subunit / Q000378:metabolism; D020569:Proto-Oncogene Proteins c-rel / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D050794:STAT1 Transcription Factor / Q000378:metabolism; D050795:STAT2 Transcription Factor / Q000378:metabolism; D012761:Shigella boydii / Q000378:metabolism* / Q000472:pathogenicity; D012763:Shigella flexneri / Q000378:metabolism* / Q000472:pathogenicity; D051996:Transcription Factor RelA / Q000378:metabolism*; D015533:Transcriptional Activation / Q000502:physiology; D014774:Virulence; D037521:Virulence Factors / Q000378:metabolism*
D029968:Escherichia coli Proteins; D020672:I-kappa B Proteins; D016209:Interleukin-8; D052002:NF-kappa B p50 Subunit; C526043:NleE protein, E coli; D020569:Proto-Oncogene Proteins c-rel; D012333:RNA, Messenger; D050794:STAT1 Transcription Factor; C494079:STAT1 protein, human; D050795:STAT2 Transcription Factor; C494084:STAT2 protein, human; D051996:Transcription Factor RelA; D037521:Virulence Factors