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Domain 4 of pneumolysin from Streptococcus pneumoniae is a multifunctional domain contributing TLR4 activating and

Fang-Feng Chiu1, Chih-Hsiang Leng2, Yi-Jiun Ding1

  • 1National Institute of Infectious Diseases and Vaccinology, National Health Research Institutes, Zhunan Town, Miaoli, Taiwan, ROC.

Biochemical and Biophysical Research Communications
|August 10, 2019
PubMed

Insights

Domain 4 of Streptococcus pneumoniae pneumolysin (Ply) activates immune cells via Toll-like receptor 4 and causes hemolysis. This domain alone contributes significantly to bacterial virulence, independent of apoptosis.

Area of Science:

  • Microbiology
  • Immunology
  • Molecular Biology

Background:

  • Streptococcus pneumoniae produces pneumolysin (Ply), a protein with multiple activities.
  • Ply's structure includes four domains, each potentially contributing to its functions.

Purpose of the Study:

  • To investigate the specific roles of recombinant Ply domains, particularly domain 4 (rPly4), in apoptosis, cytokine production, hemolysis, and virulence.
  • To elucidate the mechanism of rPly4's interaction with immune cells and its contribution to bacterial pathogenesis.

Main Methods:

  • Expression and characterization of recombinant full-length Ply and truncated forms (Ply domain 1-3, rPly4).
  • Assessment of rPly4's effects on dendritic cell activation (TLR4-dependent), hemolytic activity, and lipid bilayer penetration.
  • Evaluation of rPly4's virulence in a mouse model, comparing it to full-length Ply.

Main Results:

  • rPly4 activated murine bone marrow-derived dendritic cells in a Toll-like receptor 4-dependent manner.
  • rPly4 exhibited hemolytic activity at high concentrations and could penetrate lipid bilayers.
  • Domain 4 of Ply was found to be involved in bacterial virulence, with rPly4 causing virulence similar to full-length Ply in the absence of apoptosis.

Conclusions:

  • Domain 4 of pneumolysin is a key virulence factor for Streptococcus pneumoniae.
  • rPly4's ability to activate TLR4 and its hemolytic activity are significant contributors to its role in virulence.

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