Lack of effect of the Salmonella deubiquitinase SseL on the NF-κB pathway

PLoS One. 2013;8(1):e53064. doi: 10.1371/journal.pone.0053064. Epub 2013 Jan 8.

Abstract

Intracellular replication of Salmonella enterica requires effector proteins translocated across the Salmonella-containing vacuolar membrane by Salmonella pathogenicity island-2 (SPI-2) encoded type III secretion system (T3SS). The SPI-2 T3SS effector SseL is a deubiquitinase that contributes to virulence in mice. Previous work has produced conflicting evidence as to the involvement of SseL in interference with the NF-κB pathway. To attempt to clarify these discrepancies, we compared mRNA levels in mouse primary bone marrow-derived macrophages infected with wild-type or sseL mutant strains using a genome-wide microarray. There was no detectable effect of loss of SseL on mRNA levels corresponding to any known NF-κB-regulated gene. In addition, there was no effect of SseL on (i) the activation or levels of both the canonical inhibitor of the NF-κB pathway (IκBα and phospho-IκBα), and the non-canonical NF-κB precursor p100/p52, (ii) the translocation of the NF-κB transcription factor p65 to the nucleus of infected macrophages and (iii) pro-inflammatory cytokines secretion. Furthermore, ectopic expression of SseL did not affect NF-κB activation in reporter cell lines. These results fail to support a role for SseL in the down-regulation of the host immune response and in particular the NF-κB pathway.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cells, Cultured
  • Cytokines / immunology
  • Gene Expression Regulation
  • I-kappa B Proteins / immunology
  • I-kappa B Proteins / metabolism
  • Macrophages / immunology
  • Macrophages / metabolism
  • Macrophages / microbiology*
  • Mice
  • NF-KappaB Inhibitor alpha
  • NF-kappa B / immunology*
  • NF-kappa B / metabolism
  • Phosphorylation
  • Promoter Regions, Genetic
  • Protein Transport
  • RNA, Messenger / genetics
  • Salmonella Infections / genetics
  • Salmonella Infections / immunology
  • Salmonella Infections / metabolism
  • Salmonella Infections / microbiology*
  • Salmonella enterica / enzymology*
  • Salmonella enterica / pathogenicity*
  • Signal Transduction*

Substances

  • Cytokines
  • I-kappa B Proteins
  • NF-kappa B
  • Nfkbia protein, mouse
  • RNA, Messenger
  • NF-KappaB Inhibitor alpha