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Critical role for Ipaf in Pseudomonas aeruginosa-induced caspase-1 activation

Luigi Franchi1, Joshua Stoolman, Thirumala-Devi Kanneganti

  • 1Department of Pathology and Comprehensive Cancer Center, The University of Michigan Medical School, Ann Arbor, MI 48109, USA.

European Journal of Immunology
|October 16, 2007
PubMed

Insights

The Nod-like receptor Ipaf is crucial for clearing Pseudomonas aeruginosa lung infections. Flagellin sensing by Ipaf and TLR5 involves distinct bacterial residues, impacting immune responses and macrophage cell death.

Area of Science:

  • Immunology
  • Microbiology
  • Cell Biology

Background:

  • Pseudomonas aeruginosa is an opportunistic pathogen causing diverse infections.
  • P. aeruginosa triggers significant host inflammatory responses.
  • Mechanisms of bacterial recognition and immune induction by P. aeruginosa are not fully understood.

Purpose of the Study:

  • To investigate the role of the Nod-like receptor Ipaf in P. aeruginosa lung infection.
  • To elucidate the mechanisms of bacterial recognition and immune activation by P. aeruginosa.

Main Methods:

  • Utilized an in vivo mouse model of P. aeruginosa lung infection.
  • Analyzed bacterial clearance, inflammatory mediator production (caspase-1, IL-1beta), and macrophage cell death.
  • Employed P. aeruginosa mutants with specific flagellin modifications and type III secretion system alterations.

Main Results:

  • Ipaf is essential for optimal bacterial clearance in P. aeruginosa lung infection.
  • Bacterial flagellin is critical for caspase-1 and IL-1beta activation, dependent on Ipaf and ASC, but not TLR5.
  • P. aeruginosa-induced macrophage cell death requires flagellin and Ipaf, but not ASC.
  • Distinct flagellin amino acid residues are recognized by Ipaf and TLR5.
  • Caspase-1 and IL-1beta secretion require a functional type III secretion system, independent of ExoS, ExoT, and ExoY.

Conclusions:

  • Ipaf plays a key role in host defense against P. aeruginosa lung infection.
  • Flagellin is a critical P. aeruginosa component recognized by the host immune system through Ipaf and TLR5.
  • Distinct flagellin epitopes are sensed by Ipaf and TLR5, leading to differential immune outcomes.
  • The type III secretion system, but not its specific effectors, is involved in P. aeruginosa-induced inflammasome activation.

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