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Central role of PAFR signalling in ExoU-induced NF-κB activation

Carolina Diettrich Mallet de Lima1, Jessica da Conceição Costa, Sabrina Alves de Oliveira Lima Santos

  • 1Departamento de Microbiologia, Imunologia e Parasitologia, Universidade do Estado do Rio de Janeiro, Rio de Janeiro, RJ, Brazil.

Cellular Microbiology
|March 12, 2014
PubMed

Insights

Pseudomonas aeruginosa toxin ExoU activates NF-κB signaling via PAFR, which amplifies PAFR expression. This mechanism highlights a key response amplification in bacterial infections.

Area of Science:

  • Microbiology
  • Immunology
  • Cell Biology

Background:

  • ExoU is a critical virulence factor in Pseudomonas aeruginosa infections.
  • Understanding the molecular mechanisms of ExoU-induced inflammation is crucial for developing therapeutic strategies.

Purpose of the Study:

  • To elucidate the mechanisms by which ExoU activates the NF-κB pathway.
  • To investigate the role of Platelet-Activating Factor Receptor (PAFR) in ExoU-mediated NF-κB activation and its subsequent regulation of PAFR expression.

Main Methods:

  • Infection of human airway cells and mice with Pseudomonas aeruginosa strains.
  • Confocal microscopy to assess p65 nuclear translocation in lung tissues.
  • Chromatin immunoprecipitation (ChIP) assays to evaluate p65 binding to the PAFR promoter.
  • Luciferase reporter assays to confirm p65 binding to NF-κB sites in the PAFR promoter.
  • Treatment with NF-κB inhibitors (Bay 11-7082) and PAFR antagonists (WEB 2086).

Main Results:

  • PAFR is essential for the activation of the canonical NF-κB pathway by ExoU.
  • PAFR-dependent NF-κB activation primarily occurs in respiratory epithelial cells.
  • ExoU enhances PAFR expression by increasing p65 binding to the PAFR promoter.
  • Inhibition of NF-κB or PAFR signaling reduces PAFR expression in vitro and in vivo.

Conclusions:

  • ExoU activates NF-κB signaling through PAFR.
  • This interaction leads to an amplification loop where NF-κB activation enhances PAFR expression.
  • This mechanism is critical for amplifying the host response to Pseudomonas aeruginosa ExoU toxin.

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