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A Functional Core of IncA Is Required for Chlamydia trachomatis Inclusion Fusion

Mary M Weber1, Nicholas F Noriea1, Laura D Bauler1

  • 1Host Parasite Interactions Section, Laboratory of Bacteriology, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana, USA.

Journal of Bacteriology
|February 18, 2016
PubMed
Abstract

Insights

Chlamydia trachomatis uses the IncA protein for homotypic inclusion fusion. A functional core within IncA, including SNARE-like domains, is essential for this process, as confirmed by genetic complementation studies.

Area of Science:

  • Microbiology
  • Cell Biology
  • Molecular Biology

Background:

  • Chlamydia trachomatis is an obligate intracellular pathogen causing diseases like trachoma and STIs.
  • Chlamydial inclusions, modified by type III secreted Inc proteins, exhibit homotypic fusion in multiply infected cells.
  • IncA, an inclusion membrane protein, possesses SNARE-like domains homologous to eukaryotic fusion machinery.

Purpose of the Study:

  • To genetically verify the role of IncA in Chlamydia trachomatis homotypic inclusion fusion.
  • To identify the essential functional domains of IncA required for mediating inclusion fusion.
  • To utilize and validate new genetic tools for complementation of site-specific mutants in Chlamydia.

Main Methods:

  • Generation of an incA::bla mutant to inactivate the IncA gene.
  • Complementation of the mutant with full-length IncA and domain-specific variants.
  • Phenotypic analysis of inclusion fusion in wild-type, mutant, and complemented strains.

Main Results:

  • Insertional inactivation of incA resulted in nonfusogenic inclusions, demonstrating IncA's necessity for fusion.
  • Complementation with full-length IncA fully restored homotypic inclusion fusion.
  • Fusion rescue was dependent on the presence of a functional core comprising SNARE-like domain 1 (SLD-1) and part of SNARE-like domain 2 (SLD-2).

Conclusions:

  • The IncA protein, particularly its SNARE-like core domains, is essential for the homotypic fusion of Chlamydia trachomatis inclusions.
  • These findings confirm in vitro biochemical data and highlight the utility of newly developed genetic complementation tools for studying Chlamydia.
  • This work provides a foundation for further investigation into the molecular mechanisms of chlamydial inclusion membrane dynamics.

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