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Updated: Jul 12, 2026

Detection of Toxin Translocation into the Host Cytosol by Surface Plasmon Resonance
10:41

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Published on: January 3, 2012

Intracellular trafficking of Pseudomonas ExoS, a type III cytotoxin

Qing Deng1, Yue Zhang, Joseph T Barbieri

  • 1Department of Microbiology and Molecular Genetics, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226, USA.

Traffic (Copenhagen, Denmark)
|August 24, 2007
PubMed

Insights

Pseudomonas aeruginosa ExoS toxin enters host cells via cholesterol-dependent endocytosis. This bacterial cytotoxin traffics along host microtubules to disrupt cellular signaling pathways.

Area of Science:

  • Microbiology
  • Cell Biology
  • Biochemistry

Background:

  • Pseudomonas aeruginosa utilizes type III secretion systems to deliver effector proteins like ExoS into host cells.
  • ExoS is a bifunctional cytotoxin that disrupts host cell signaling pathways, including Ras and Rho.
  • A specific hydrophobic region targets ExoS to the plasma membrane and endosomes.

Purpose of the Study:

  • To elucidate the intracellular trafficking pathways of the Pseudomonas aeruginosa ExoS toxin within mammalian cells.
  • To identify host cell factors and pathways involved in ExoS endocytosis and intracellular transport.

Main Methods:

  • Utilized metabolic inhibitors and dominant-negative proteins to disrupt vesicle trafficking.
  • Employed methyl-beta-cyclodextrin to deplete cholesterol and nocodazole to disrupt microtubules.
  • Assessed ExoS localization and its ability to ADP-ribosylate Ras in host cells.

Main Results:

  • ExoS release from the plasma membrane was independent of dynamin and ADP ribosylation factor 6.
  • Cholesterol depletion and microtubule disruption inhibited ExoS trafficking and its ability to ADP-ribosylate Ras.
  • ExoS demonstrated cycling between the plasma membrane and perinuclear regions, indicating bidirectional trafficking.

Conclusions:

  • ExoS endocytosis is dependent on host cell cholesterol.
  • Intracellular trafficking of ExoS relies on host microtubules and involves both anterograde and retrograde transport.
  • Understanding ExoS trafficking may reveal therapeutic targets against gram-negative bacterial pathogens.

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