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Proliferative inhibition by dominant-negative Ras rescues naive and neuronally differentiated PC12 cells from
1Department of Pathology, Columbia University College of Physicians and Surgeons, New York, NY 10032.
Abstract:
We have used the nerve growth factor (NGF)-responsive PC12 cell line as a model to examine the role of cell cycle progression in apoptotic neuronal cell death triggered by withdrawal of trophic support. Because p21 Ras plays a key role in mitogenic signaling, we tested whether interference with the activity of this protein would affect cell cycle progression and thereby apoptotic death after trophic factor deprivation. For this purpose, we exploited PC12 cells transfected with an inducible form of dominant-inhibitory Ras. In contrast to non-transfected and uninduced cells, which continue to synthesize DNA when deprived of trophic support, PC12 cells induced to express dominant-inhibitory Ras showed little thymidine incorporation. When non-transfected and uninduced cells were deprived of trophic support, these underwent rapid apoptotic death that could be prevented by NGF. However, cells in which dominant-inhibitory Ras was induced and which were consequently quiescent did not die upon withdrawal of trophic support and showed long-term survival in the absence of NGF or other trophic factors. Moreover, induction of dominant-inhibitory Ras also rescued non-dividing, neuronally differentiated PC12 cells from death caused by NGF withdrawal. These findings suggest a relationship between proliferative capacity and neuronal apoptosis and raise the hypothesis that following withdrawal of trophic support, neurons undergo an unsuccessful and fatal attempt to re-enter the cell cycle.
Insights
Blocking cell cycle progression with dominant-inhibitory Ras prevents apoptotic neuronal cell death. This suggests that neuronal death after trophic support withdrawal involves an attempt to re-enter the cell cycle.
Area of Science:
- Neuroscience
- Cell Biology
- Molecular Biology
Background:
- Neuronal cell death is often triggered by the withdrawal of trophic support.
- Cell cycle progression is implicated in neuronal apoptosis, particularly in response to mitogenic signaling pathways.
Purpose of the Study:
- To investigate the role of cell cycle progression in apoptotic neuronal cell death.
- To examine if interfering with p21 Ras activity affects cell cycle progression and subsequent apoptosis after trophic factor deprivation.
Main Methods:
- Utilized the nerve growth factor (NGF)-responsive PC12 cell line.
- Employed PC12 cells transfected with an inducible form of dominant-inhibitory Ras.
- Assessed DNA synthesis via thymidine incorporation and monitored cell survival after NGF withdrawal.
Main Results:
- PC12 cells expressing dominant-inhibitory Ras showed reduced DNA synthesis and were protected from apoptosis upon NGF withdrawal.
- Quiescent cells induced to express dominant-inhibitory Ras survived long-term without trophic support.
- Dominant-inhibitory Ras also rescued non-dividing, differentiated PC12 cells from NGF withdrawal-induced death.
Conclusions:
- Neuronal proliferative capacity is linked to apoptosis following trophic support withdrawal.
- Neurons may attempt an unsuccessful and fatal re-entry into the cell cycle after trophic factor deprivation, leading to apoptosis.