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Imaging InlC Secretion to Investigate Cellular Infection by the Bacterial Pathogen Listeria monocytogenes
14:05

Imaging InlC Secretion to Investigate Cellular Infection by the Bacterial Pathogen Listeria monocytogenes

Published on: September 19, 2013

SecA2-dependent secretion of autolytic enzymes promotes Listeria monocytogenes pathogenesis

Laurel L Lenz1, Sina Mohammadi, Aimee Geissler

  • 1Department of Molecular and Cell Biology, University of California, 401 Barker Hall, Berkeley, CA 94720-3202, USA. lenz@uclink4.berkeley.edu

Proceedings of the National Academy of Sciences of the United States of America
|October 7, 2003
PubMed

Insights

The SecA2 secretion system in Listeria monocytogenes releases autolysins that degrade bacterial peptidoglycan, crucial for virulence and host colonization. Disrupting this system impairs bacterial spread and survival during infection.

Area of Science:

  • Microbiology
  • Pathogenesis
  • Bacterial Secretion Systems

Background:

  • Pathogenic bacteria utilize diverse secretion systems to invade hosts and evade immunity.
  • Mechanisms of protein secretion in Gram-positive bacteria, particularly Listeria monocytogenes, remain largely unknown.
  • The auxiliary SecA2 secretion system is identified in L. monocytogenes and other Gram-positive pathogens.

Purpose of the Study:

  • To investigate the role of the SecA2 secretion system in L. monocytogenes virulence.
  • To identify SecA2-dependent secreted proteins and their functions.
  • To elucidate the contribution of SecA2 to host-pathogen interactions.

Main Methods:

  • Proteomics analysis to identify SecA2-dependent proteins.
  • Genetic manipulation (knockout mutants) of L. monocytogenes strains (DeltaSecA2, Deltap60, DeltaNamA).
  • In vivo murine infection models and in vitro cultured cell infection assays to assess bacterial virulence and spread.

Main Results:

  • Seventeen SecA2-dependent proteins were identified, including p60 and NamA autolysins.
  • p60 and NamA hydrolyze bacterial peptidoglycan, contributing to host colonization.
  • DeltaSecA2 mutants showed rapid clearance in vivo and reduced cell-cell spread; Deltap60 and DeltaNamA mutants had intermediate virulence defects.

Conclusions:

  • SecA2-dependent secretion of p60 and NamA is critical for L. monocytogenes virulence, likely through peptidoglycan hydrolysis.
  • The SecA2 system may facilitate the release of muramyl peptides that modulate host inflammatory responses.
  • Targeting the SecA2 system could be a strategy to combat Gram-positive bacterial infections.

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