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Identification of mycobacterial surface proteins released into subcellular compartments of infected macrophages
1Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri 63110, USA. beatty@borcim.wustl.edu
Abstract:
Considerable effort has focused on the identification of proteins secreted from Mycobacterium spp. that contribute to the development of protective immunity. Little is known, however, about the release of mycobacterial proteins from the bacterial phagosome and the potential role of these molecules in chronically infected macrophages. In the present study, the release of mycobacterial surface proteins from the bacterial phagosome into subcellular compartments of infected macrophages was analyzed. Mycobacterium bovis BCG was surface labeled with fluorescein-tagged succinimidyl ester, an amine-reactive probe. The fluorescein tag was then used as a marker for the release of bacterial proteins in infected macrophages. Fractionation studies revealed bacterial proteins within subcellular compartments distinct from mycobacteria and mycobacterial phagosomes. To identify these proteins, subcellular fractions free of bacteria were probed with mycobacterium-specific antibodies. The fibronectin attachment protein and proteins of the antigen 85-kDa complex were identified among the mycobacterial proteins released from the bacterial phagosome.
Insights
Mycobacterium bovis BCG releases surface proteins into macrophages, including fibronectin attachment protein and antigen 85-kDa complex proteins. This finding sheds light on bacterial protein release mechanisms in chronic infections.
Area of Science:
- Immunology
- Microbiology
- Cell Biology
Background:
- Mycobacterium spp. proteins are crucial for protective immunity.
- Limited knowledge exists on mycobacterial protein release from phagosomes into chronically infected macrophages.
Purpose of the Study:
- To investigate the release of mycobacterial surface proteins from the phagosome into macrophage subcellular compartments.
- To identify specific mycobacterial proteins released during chronic infection.
Main Methods:
- Surface labeling of Mycobacterium bovis BCG with fluorescein-tagged succinimidyl ester.
- Macrophage infection and subcellular fractionation.
- Immunological probing of bacterial proteins using mycobacterium-specific antibodies.
Main Results:
- Mycobacterial proteins were detected in subcellular compartments separate from bacteria and phagosomes.
- Identified released proteins include the fibronectin attachment protein and the antigen 85-kDa complex.
Conclusions:
- Mycobacterium bovis BCG actively releases surface proteins into the macrophage cytoplasm.
- Fibronectin attachment protein and antigen 85-kDa complex are among the proteins released, suggesting potential roles in macrophage interaction and chronic infection.