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Direct involvement of p53 in programmed cell death of oligodendrocytes
O Eizenberg1, A Faber-Elman, E Gottlieb
1Department of Neurobiology, Weizmann Institute of Science, Rehovot, Israel.
Abstract:
A covalent dimer of interleukin (IL)-2, produced in vitro by the action of a nerve-derived transglutaminase, has been shown previously to be cytotoxic to mature rat brain oligodendrocytes. Here we report that this cytotoxic effect operates via programmed cell death (apoptosis) and that the p53 tumor suppressor gene is involved directly in the process. The apoptotic death of mature rat brain oligodendrocytes in culture following treatment with dimeric IL-2 was demonstrated by chromatin condensation and internucleosomal DNA fragmentation. The peak of apoptosis was observed 16-24 h after treatment, while the commitment to death was already observed after 3-4 h. An involvement of p53 in this process was indicated by the shift in location of constitutively expressed endogenous p53 from the cytoplasm to the nucleus, as early as 15 min after exposure to dimeric IL-2. Moreover, infection with a recombinant retrovirus encoding a C-terminal p53 miniprotein, shown previously to act as a dominant negative inhibitor of endogenous wild-type p53 activity, protected these cells from apoptosis.
Insights
Dimeric interleukin-2 (IL-2) induces apoptosis in rat brain oligodendrocytes. The p53 tumor suppressor gene plays a direct role in this programmed cell death process, as confirmed by p53 nuclear translocation and protection via p53 inhibition.
Area of Science:
- Neuroscience
- Cell Biology
- Molecular Biology
Background:
- Dimeric interleukin-2 (IL-2) is cytotoxic to mature rat brain oligodendrocytes.
- The mechanism of this cytotoxicity was previously unknown.
Purpose of the Study:
- To elucidate the mechanism of dimeric IL-2-induced oligodendrocyte death.
- To investigate the role of the p53 tumor suppressor gene in this process.
Main Methods:
- Oligodendrocyte cultures were treated with dimeric IL-2.
- Apoptosis was assessed via chromatin condensation and DNA fragmentation.
- p53 localization was monitored by immunofluorescence.
- Cells were infected with a p53 inhibitory retrovirus.
Main Results:
- Dimeric IL-2 induced apoptosis in oligodendrocytes, peaking at 16-24 hours.
- Commitment to cell death occurred within 3-4 hours.
- p53 translocated from cytoplasm to nucleus within 15 minutes of dimeric IL-2 exposure.
- Inhibition of p53 activity protected oligodendrocytes from apoptosis.
Conclusions:
- Dimeric IL-2 induces programmed cell death (apoptosis) in mature rat brain oligodendrocytes.
- The p53 tumor suppressor gene is directly involved in mediating this apoptotic process.
- p53 nuclear translocation is an early event in dimeric IL-2-induced oligodendrocyte apoptosis.