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Coxiella burnetii effector protein subverts clathrin-mediated vesicular trafficking for pathogen vacuole biogenesis

Charles L Larson1, Paul A Beare, Dale Howe

  • 1Coxiella Pathogenesis Section, Laboratory of Intracellular Parasites, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, MT 59840.

Proceedings of the National Academy of Sciences of the United States of America
|November 20, 2013
PubMed

Insights

Coxiella burnetii subverts host cell trafficking for Q fever pathogenesis. The study reveals Coxiella vacuolar protein A (CvpA) hijacks clathrin-mediated vesicle transport, crucial for bacterial replication and vacuole development.

Area of Science:

  • Microbiology
  • Cell Biology
  • Infectious Diseases

Background:

  • Coxiella burnetii causes Q fever by forming a unique parasitophorous vacuole (PV) within host macrophages.
  • Pathogen manipulation of host vesicular trafficking is essential for PV biogenesis, but the mechanisms are not fully understood.
  • The Dot/Icm type 4B secretion system is implicated in delivering effector proteins to the host cytosol for PV development.

Purpose of the Study:

  • To investigate the role of clathrin-mediated vesicular trafficking in Coxiella burnetii PV formation.
  • To define the function of Coxiella vacuolar protein A (CvpA) in hijacking host cell transport pathways.
  • To elucidate how CvpA interacts with host cell machinery to promote bacterial survival and replication.

Main Methods:

  • Analysis of a C. burnetii ΔcvpA mutant for defects in replication and PV development.
  • Localization studies of ectopically expressed mCherry-CvpA in host cells using markers like Rab11 and transferrin receptor.
  • Investigation of CvpA's interaction with clathrin adaptor protein (AP) complexes and clathrin heavy chain using pull-down assays.
  • Assessment of C. burnetii replication following siRNA-mediated depletion of AP2 or clathrin.

Main Results:

  • A C. burnetii ΔcvpA mutant showed significant defects in bacterial replication and PV development.
  • Ectopically expressed CvpA localized to recycling endosomes and its membrane interactions depended on endocytic sorting motifs.
  • CvpA expression interfered with transferrin uptake, indicating modulation of the endocytic recycling system.
  • CvpA directly interacted with AP2 and clathrin, and depletion of these proteins inhibited C. burnetii replication.

Conclusions:

  • Clathrin-mediated vesicular trafficking is critical for Coxiella burnetii infection.
  • Coxiella vacuolar protein A (CvpA) plays a key role in subverting host endocytic pathways for PV biogenesis.
  • CvpA utilizes dileucine and tyrosine-based sorting motifs to engage host adaptor proteins and clathrin, facilitating bacterial colonization.
Keywords:
type IV secretionvesicular fusion

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