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Cellular apoptosis is associated with increased caveolin-1 expression in macrophages
Peter Gargalovic1, Ladislav Dory
1Department of Molecular Biology & Immunology, The University of North Texas Health Science Center at Fort Worth, TX 76107, USA.
Journal of Lipid Research
|June 5, 2003
Summary
Macrophage apoptosis involves increased caveolin-1 ( CAV1 ) expression, a key event independent of protein synthesis. This suggests CAV1 may facilitate phosphatidylserine externalization in apoptotic macrophages.
Area of Science:
- Immunology
- Cell Biology
- Biochemistry
Background:
- Macrophage apoptosis influences immune response, atherosclerotic plaque stability, and cellular debris clearance.
- Caveolin-1 (CAV1) has been implicated in apoptosis regulation in non-macrophage cell types.
- Understanding macrophage apoptosis mechanisms is crucial for various physiological and pathological processes.
Purpose of the Study:
- To investigate the role and expression of caveolin-1 during macrophage apoptosis.
- To determine if CAV1 expression changes in response to different apoptotic stimuli in macrophages.
- To elucidate the relationship between CAV1, phosphatidylserine (PS) externalization, and caspase activation in apoptotic macrophages.
Main Methods:
- Treatment of mouse peritoneal macrophages with unrelated apoptotic agents (simvastatin, camptothecin, glucose deprivation).
- Assessment of apoptosis via cell morphology, annexin V labeling, and DNA fragmentation.
- Analysis of caveolin-1 and caveolin-2 expression levels.
- Investigation of CAV1 localization in lipid rafts and its colocalization with PS.
- Evaluation of the effect of cycloheximide on CAV1 increase during apoptosis.
Main Results:
- Various apoptotic stimuli caused a significant increase in CAV1 expression in macrophages, while caveolin-2 remained unchanged.
- CAV1 was found in lipid rafts and colocalized with phosphatidylserine (PS) on the surface of apoptotic macrophages.
- The increase in CAV1 and PS externalization occurred early in apoptosis and were independent of caspase activation and new protein synthesis.
- Cycloheximide did not inhibit the apoptosis-induced increase in CAV1 levels.
Conclusions:
- Elevated caveolin-1 expression is a characteristic feature of the apoptotic phenotype in macrophages.
- Caveolin-1 may play a functional role in the efficient externalization of phosphatidylserine on the surface of apoptotic macrophages.
- CAV1-mediated PS externalization could be a critical step in the clearance of apoptotic macrophages by phagocytes.