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Type VI secretion system in Pseudomonas aeruginosa: secretion and multimerization of VgrG proteins

Abderrahman Hachani1, Nadine S Lossi, Alexander Hamilton

  • 1Centre for Molecular Microbiology and Infection, Division of Cell and Molecular Biology, Imperial College London, London SW7 2AZ, United Kingdom.

The Journal of Biological Chemistry
|February 18, 2011
PubMed

Insights

Pseudomonas aeruginosa uses its type VI secretion system (T6SS) for infections. Researchers found distinct VgrG proteins have varied roles in T6SS function and substrate secretion.

Area of Science:

  • Microbiology
  • Molecular Biology
  • Bacterial Pathogenesis

Background:

  • Pseudomonas aeruginosa, a Gram-negative bacterium, causes chronic infections, particularly in cystic fibrosis patients.
  • These infections are often linked to an active type VI secretion system (T6SS), a complex molecular machine.
  • The T6SS comprises ~15 conserved proteins, including the AAA+ ATPase ClpV, and secretes effector proteins like Hcp and VgrG.

Purpose of the Study:

  • To investigate the roles of different VgrG proteins in Pseudomonas aeruginosa H1-T6SS function.
  • To determine the secretion mechanisms and functional requirements of specific VgrG variants (VgrG1a, VgrG1b, VgrG1c).
  • To elucidate the involvement of VgrG proteins in the secretion of other T6SS substrates, such as Hcp1 and Tse3.

Main Methods:

  • Genomic identification of vgrG genes in the PAO1 strain.
  • Analysis of gene co-regulation with the H1-T6SS using the RetS sensor.
  • Assessment of protein secretion dependence on ClpV1 and functional assays for substrate secretion (Hcp1, Tse3).

Main Results:

  • Ten vgrG genes were identified in P. aeruginosa PAO1, with three (vgrG1a/b/c) co-regulated with H1-T6SS.
  • VgrG1a and VgrG1c secretion were ClpV1-dependent and formed multimers, suggesting a role in Hcp1 secretion.
  • VgrG1b secretion was ClpV1-independent and not required for Hcp1 secretion or H1-T6SS function; VgrG proteins are essential for Tse3 secretion.

Conclusions:

  • Distinct VgrG proteins exhibit varied secretion mechanisms and functional roles within the P. aeruginosa T6SS.
  • VgrG1a and VgrG1c are crucial for Hcp1 secretion, potentially by facilitating envelope penetration.
  • VgrG proteins are not merely secreted components but are essential for the secretion of other T6SS substrates, highlighting their multifaceted roles.

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