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C3 as substrate for adhesion of Streptococcus pneumoniae
1Department of Pediatrics, Division of Infectious Diseases, and Department of Microbiology, Immunology and Molecular Pathobiology, University of Minnesota, Minneapolis, USA.
The Journal of Infectious Diseases
|July 29, 2000
Summary
Streptococcus pneumoniae's CbpA protein binds to human epithelial cell-secreted C3 complement. This interaction is crucial for pneumococcal adhesion to lung epithelial cells and C3-coated surfaces.
Area of Science:
- Microbiology
- Immunology
- Cell Biology
Background:
- Choline-binding protein A (CbpA) from Streptococcus pneumoniae interacts with complement component 3 (C3).
- This interaction may involve C3 found in the bloodstream or C3 secreted by epithelial cells.
Purpose of the Study:
- To investigate the interaction between pneumococcal CbpA and C3 secreted by pulmonary epithelial cells.
- To determine the role of this interaction in pneumococcal adhesion to epithelial cells.
Main Methods:
- Cultured type II pulmonary epithelial cells (A549) were used to measure C3 secretion.
- Immunofluorescence confirmed C3 expression on epithelial cell surfaces.
- Western blot analysis assessed C3 binding to CbpA.
- Adhesion assays were performed using CbpA mutants on C3-coated matrices and epithelial cells.
Main Results:
- Epithelial cells secreted C3, which was expressed on their surface.
- Secreted C3 bound to the pneumococcal CbpA protein.
- CbpA-deficient mutants showed no C3 binding and were deficient in adhesion to C3-coated substrates and pulmonary epithelial cells.
Conclusions:
- Pneumococcal CbpA directly interacts with C3 secreted by pulmonary epithelial cells.
- This CbpA-C3 interaction is essential for Streptococcus pneumoniae adhesion to lung epithelial cells.
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