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Macrophage elastase kills bacteria within murine macrophages
A McGarry Houghton1, William O Hartzell, Clinton S Robbins
1Division of Pulmonary, Allergy, and Critical Care Medicine, Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15213, USA. houghtonm@dom.pitt.edu
Nature
|June 19, 2009
Summary
Matrix metalloproteinase 12 (MMP12) directly kills bacteria by disrupting cell membranes. MMP12 is crucial for macrophage antimicrobial defense, with its carboxy-terminal domain mediating this activity.
Area of Science:
- Immunology
- Microbiology
- Biochemistry
Background:
- Macrophages are key immune cells for pathogen defense, utilizing various antimicrobial substances.
- The role of macrophage-derived proteinases in antimicrobial activity is largely unexplored.
- Macrophage elastase (MMP12) is expressed in macrophages but its physiological functions remain unknown.
Purpose of the Study:
- To investigate the potential antimicrobial role of macrophage elastase (MMP12).
- To determine the mechanism and specific domain responsible for MMP12's antimicrobial activity.
Main Methods:
- Utilized Mmp12(-/-) mice challenged with gram-negative and gram-positive bacteria.
- Analyzed bacterial clearance, mortality rates, and MMP12 localization within macrophages.
- Investigated the role of MMP12's catalytic and carboxy-terminal domains in antimicrobial activity.
Main Results:
- Mmp12(-/-) mice showed impaired bacterial clearance and increased mortality.
- MMP12 is mobilized to macrophage phagolysosomes upon bacterial ingestion.
- MMP12 disrupts bacterial cell membranes, leading to bacterial death, with activity localized to the carboxy-terminal domain.
Conclusions:
- Macrophage elastase (MMP12) possesses direct antimicrobial properties, acting as a crucial component of the innate immune response.
- The carboxy-terminal domain of MMP12, containing a unique four amino acid sequence, is essential for its antibacterial activity.
- This study identifies a novel antimicrobial peptide with unique structural and sequential characteristics.
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