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Apoptotic cell death analyzed at the molecular level by two-dimensional gel electrophoresis
B Robaye1, A P Døskeland, N Suarez-Huerta
1Institute of Interdisciplinary Research, School of Medicine, Free University of Brussels, Belgium.
Abstract:
The pattern of protein expression and phosphorylation after an apoptotic stimulus has been studied in two systems. Bovine aortic endothelial cells were induced to undergo apoptotic cell death by a combination of a cytokine (tumor necrosis factor, TNF) and inhibitors of protein synthesis, like cycloheximide. Two-dimensional (2-DE) electrophoresis of proteins from such cells revealed specific proteolysis of distinct proteins, some at an early stage of apoptosis and some at a later stage. These proteins may have antiapoptotic properties. In rat IPC-81 promyelocytic leukemia cells, cAMP induced apoptosis. 2-DE of such cells pulse-labeled with [35S]methionine revealed two "novel" protein spots (of 30 kDa and 46 kDa, respectively), induced very rapidly by a posttranscriptional mechanism. It is proposed that "dysphosphorylation" may accompany apoptosis in general, since both endothelial cells treated with TNF/cycloheximide and IPC-81 cells treated with cAMP analog or the apoptosis-inducing phosphatase inhibitors okadaic acid or calyculin A all showed altered protein phosphorylation patterns, as revealed by 2-DE electrophoresis of proteins from cells prelabeled with 32Pi.
Insights
This study investigated protein changes during apoptosis in endothelial and leukemia cells. Researchers found specific protein degradation and altered phosphorylation patterns, suggesting these changes play roles in programmed cell death.
Area of Science:
- Cell Biology
- Biochemistry
- Molecular Biology
Background:
- Apoptosis, or programmed cell death, is a fundamental biological process.
- Understanding the molecular mechanisms of apoptosis is crucial for various fields, including cancer research and drug development.
Purpose of the Study:
- To investigate protein expression and phosphorylation patterns during apoptosis in different cell types.
- To identify specific proteins involved in the apoptotic process and explore potential antiapoptotic roles.
Main Methods:
- Utilized two-dimensional (2-DE) gel electrophoresis to analyze protein expression and phosphorylation.
- Employed apoptotic stimuli such as tumor necrosis factor (TNF) with cycloheximide in bovine aortic endothelial cells.
- Induced apoptosis in rat IPC-81 promyelocytic leukemia cells using cAMP and phosphatase inhibitors (okadaic acid, calyculin A).
- Performed pulse-labeling with [35S]methionine and 32Pi to track newly synthesized proteins and phosphorylation events.
Main Results:
- Identified specific proteolysis of proteins at early and late stages of apoptosis in endothelial cells, with potential antiapoptotic functions.
- Discovered two novel protein spots (30 kDa and 46 kDa) rapidly induced by a posttranscriptional mechanism in leukemia cells.
- Observed altered protein phosphorylation patterns in both cell types under various apoptotic conditions, indicating widespread "dysphosphorylation" during apoptosis.
Conclusions:
- Specific protein degradation and altered phosphorylation are key features of apoptosis across different cell models.
- The identified novel proteins and phosphorylation changes may represent critical regulatory points in programmed cell death.
- Further research into these protein alterations could yield therapeutic targets for diseases involving aberrant apoptosis.