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Published on: April 8, 2016
Type IV pili-mediated secretion modulates Francisella virulence
Anthony J Hager1, Diana L Bolton, Mark R Pelletier
1Department of Pediatrics, Division of Infectious Diseases, University of Washington, Seattle, WA, USA.
Molecular Microbiology
|September 22, 2006
Summary
Francisella novicida secretes PepO protease via a Type IV pilus system, which limits bacterial spread in mice. Loss of PepO function may explain the high virulence of human pathogenic Francisella strains.
Area of Science:
- Microbiology
- Infectious Diseases
- Bacterial Pathogenesis
Background:
- Francisella tularensis causes tularaemia, a zoonotic disease.
- Francisella novicida is pathogenic in immunocompromised individuals and mice.
- The Type IV pilus (T4P) secretion system's role in Francisella virulence is not fully understood.
Purpose of the Study:
- To identify secreted proteins and the T4P secretion system in F. novicida.
- To investigate the function of the secreted protease PepO in F. novicida pathogenesis.
- To explore the implications of PepO function in the evolution of Francisella virulence.
Main Methods:
- Proteomic and bioinformatic analyses to identify secreted proteins and the T4P system.
- Gene transcription analysis regulated by the virulence regulator MglA.
- Intradermal infection of mice to assess bacterial spread and host immune response.
Main Results:
- Seven F. novicida secreted proteins, including PepO protease and BglX beta-glucosidase, were identified.
- PepO and BglX transcription is regulated by MglA.
- F. novicida mutants lacking T4P secretion or PepO showed enhanced systemic spread in mice.
- PepO mutants increased neutrophil infiltration in mouse airways.
- PepO, a zinc protease, is homologous to mammalian endothelin-converting enzyme ECE-1.
Conclusions:
- Secretion of PepO limits F. novicida spread by inducing vasoconstriction.
- Mutations in PepO in human pathogenic strains may contribute to their high virulence.
- The T4P system and PepO are crucial for F. novicida pathogenesis.
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