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Pseudomonas aeruginosa mediated apoptosis requires the ADP-ribosylating activity of exoS

Melissa R Kaufman1, Jinghua Jia2,1, Lin Zeng2,1

  • 1Department of Microbiology and Immunology, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA1.

Microbiology (Reading, England)
|October 6, 2000
PubMed

Insights

Pseudomonas aeruginosa infection triggers programmed cell death (apoptosis) in host cells. The bacterial protein ExoS, through its ADP-ribosylating activity, is essential for inducing this apoptotic response.

Area of Science:

  • Microbiology
  • Cell Biology
  • Pathogenesis

Background:

  • Pseudomonas aeruginosa is an opportunistic pathogen affecting immunocompromised individuals and cystic fibrosis patients.
  • Apoptosis, or programmed cell death, is a critical cellular process.
  • Understanding bacterial mechanisms inducing apoptosis is key to developing treatments.

Purpose of the Study:

  • To investigate the mechanism by which Pseudomonas aeruginosa induces apoptosis in host cells.
  • To identify the specific bacterial factors responsible for triggering this cellular response.

Main Methods:

  • Utilized a tissue culture system with HeLa and other epithelial/fibroblast cell lines.
  • Assessed apoptosis through morphological changes, chromatin condensation, DNA content analysis (subG1), and caspase-3 activity.
  • Employed P. aeruginosa mutants deficient in type III secretion and the ExoS protein.

Main Results:

  • P. aeruginosa efficiently induced apoptosis in host cells, characterized by specific cellular and molecular markers.
  • Type III secretion machinery, not bacterial invasion, was required for apoptosis induction.
  • Mutations in the bacterial ExoS protein abolished apoptosis induction, while complementation restored it.
  • The ADP-ribosylating activity of ExoS was essential for its ability to induce apoptosis.

Conclusions:

  • ExoS is the primary Pseudomonas aeruginosa effector molecule responsible for inducing host cell apoptosis.
  • The ADP-ribosylating function of ExoS is critical for initiating the apoptotic pathway.
  • This study elucidates a key mechanism of P. aeruginosa pathogenesis.

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