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Plasma membrane alterations and cytoskeletal changes in apoptosis
M van Engeland1, H J Kuijpers, F C Ramaekers
1Department of Molecular Cell Biology and Genetics, University of Maastricht, The Netherlands.
Experimental Cell Research
|September 23, 1997
Summary
Early apoptosis involves cell membrane changes like phosphatidylserine exposure and cytoskeletal reorganization. This study reveals these events are independent, with intermediate filaments aggregating but not degrading during cell death.
Area of Science:
- Cell Biology
- Molecular Biology
- Cancer Research
Background:
- Apoptosis involves early plasma membrane changes, including phosphatidylserine (PS) exposure.
- Cytoskeletal organization also undergoes significant alterations during early apoptosis.
- The relationship between PS exposure and cytoskeletal changes during apoptosis is not fully understood.
Purpose of the Study:
- To investigate the relationship between phosphatidylserine exposure and cytoskeletal reorganization during olomoucine- and roscovitin-induced apoptosis.
- To determine if these two early apoptotic events are causally linked or independent.
Main Methods:
- Human lung cancer and neuroblastoma cell lines were induced into apoptosis.
- Loss of membrane asymmetry (PS exposure) was detected using annexin V binding.
- Cytoskeletal components were visualized via immunocytochemistry.
- Analysis included flow cytometry, confocal microscopy, and Western blotting.
Main Results:
- Cytokeratin and vimentin aggregation occurred simultaneously with PS exposure and chromatin condensation in early apoptosis.
- Intermediate filaments were disassembled and proteolytically cleaved, while microfilaments and microtubules aggregated but were not degraded.
- Inducing PS exposure without apoptosis did not cause cytokeratin disassembly.
- Inducing cytokeratin aggregation without apoptosis did not cause PS exposure.
Conclusions:
- Phosphatidylserine exposure and cytokeratin aggregation are independent events during apoptosis.
- Intermediate filament dynamics differ from microfilaments and microtubules during apoptotic cell death.
- These findings clarify distinct molecular mechanisms occurring during early apoptosis.