Journal article
Secretion of Flagellar Proteins by the Pseudomonas aeruginosa Type III Secretion-Injectisome System
Journal of bacteriology, Vol.197(12), pp.2003-2011
06/15/2015
DOI: 10.1128/JB.00030-15
PMCID: PMC4438214
PMID: 25845843
Abstract
The opportunistic pathogen Pseudomonas aeruginosa utilizes an injectisome-type III secretion system (injectisome-T3SS) to elicit cytotoxicity toward epithelial cells and macrophages. Macrophage killing results from the cytotoxic properties of the translocated effector proteins (ExoS, ExoT, ExoU, and ExoY) and inflammasome-mediated induction of pyroptosis. Inflammasome activation can occur following Nlrc4-mediated recognition of cytosolic translocated flagellin (FliC). In the present study, we demonstrate that FliC is a secretion substrate of both the injectisome- and flagellum-associated T3SSs. Molecular analyses indicate that the first 20 amino-terminal residues of FliC are sufficient for secretion by the injectisome-T3SS and that the first 100 residues are sufficient for translocation of FliC into host cells. Although maximal inflammasome activation requires FliC, activation can also occur in the absence of FliC. This prompted us to examine whether other flagellar components might also be translocated into cells to elicit inflammasome activation. Indeed, we find that the flagellar cap (FliD), hook-associated (FlgK and FlgL), hook (FlgE), and rod (FlgE) proteins are secretion substrates of the injectisome-T3SS. None of these proteins, however, result in increased inflammasome activation when they are overexpressed in a fliC mutant and appear to be translocated into host cells. While a role in inflammasome activation has been excluded, these data raise the possibility that flagellar components, which are highly conserved between different bacterial species, trigger other specific host responses from the extracellular milieu or contribute to the pathogenesis of P. aeruginosa.
The inflammasome is a host defense mechanism that recognizes invading bacteria and triggers an inflammatory immune response. The opportunistic pathogen P. aeruginosa produces both inflammasome agonists and antagonists. In this study, we demonstrate that overexpression of an agonist suppresses the activity of an antagonist, thereby resulting in inflammasome activation. Since the relative expression levels of agonists and antagonists likely vary between strains, these differences could be important predictors of whether a particular P. aeruginosa strain elicits inflammasome activation.
Details
- Title: Subtitle
- Secretion of Flagellar Proteins by the Pseudomonas aeruginosa Type III Secretion-Injectisome System
- Creators
- Dilek Ince - Department of Internal Medicine, Division of Infectious Disease, University of Iowa, Iowa City, Iowa, USAFayyaz S Sutterwala - Department of Internal Medicine, Division of Infectious Disease, University of Iowa, Iowa City, Iowa, USA Veterans Affairs Medical Center, Iowa City, Iowa, USATimothy L Yahr - Department of Microbiology, University of Iowa, Iowa City, Iowa, USA tim-yahr@uiowa.edu
- Resource Type
- Journal article
- Publication Details
- Journal of bacteriology, Vol.197(12), pp.2003-2011
- Publisher
- United States
- DOI
- 10.1128/JB.00030-15
- PMID
- 25845843
- PMCID
- PMC4438214
- ISSN
- 0021-9193
- eISSN
- 1098-5530
- Grant note
- N01 AI30040 / NIAID NIH HHS N01 AI030040 / NIAID NIH HHS R01 AI087630 / NIAID NIH HHS
- Language
- English
- Date published
- 06/15/2015
- Academic Unit
- Microbiology and Immunology; Infectious Diseases; Internal Medicine
- Record Identifier
- 9984001136202771
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