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Calpains mediate p53 activation and neuronal death evoked by DNA damage
Mary Sedarous1, Elizabeth Keramaris, Michael O'Hare
1Ottawa Health Research Institute, Neuroscience Group, University of Ottawa, Ottawa, Ontario K1H 8M5, Canada.
Abstract:
DNA damage is an initiator of neuronal death implicated in neuropathological conditions such as stroke. Previous evidence has shown that apoptotic death of embryonic cortical neurons treated with the DNA damaging agent camptothecin is dependent upon the tumor suppressor p53, an upstream death mediator, and more distal death effectors such as caspases. We show here that the calcium-regulated cysteine proteases, calpains, are activated during DNA damage induced by camptothecin treatment. Moreover, calpain deficiency, calpastatin expression, or pharmacological calpain inhibitors prevent the death of embryonic cortical neurons, indicating the important role of calpain in DNA damage-induced death. Calpain inhibition also significantly reduced and delayed the induction of p53. Consistent with the actions of calpains upstream of p53 and the proximal nature of p53 death signaling, calpain inhibition inhibited cytochrome c release and DEVD-AFC cleavage activity. Taken together, our results indicate that calpains are a key mediator of p53 induction and consequent caspase-dependent neuronal death due to DNA damage.
Insights
Calpains, calcium-regulated proteases, are activated by DNA damage and trigger neuronal death. Inhibiting calpains prevents this death and reduces p53 induction, revealing calpains as key mediators in DNA damage-induced neuronal apoptosis.
Area of Science:
- Neuroscience
- Molecular Biology
- Cell Death Research
Background:
- DNA damage initiates neuronal death, a process implicated in stroke and other neuropathologies.
- Apoptotic neuronal death involves the tumor suppressor p53 and caspases.
- The role of calcium-regulated proteases in DNA damage-induced neuronal death is not fully understood.
Purpose of the Study:
- To investigate the role of calpains in DNA damage-induced neuronal death.
- To determine the relationship between calpains, p53, and caspase activation in this process.
Main Methods:
- Treatment of embryonic cortical neurons with camptothecin (a DNA damaging agent).
- Assessment of calpain activation, neuronal survival, p53 induction, and caspase activity.
- Utilizing calpain deficiency, calpastatin expression, and pharmacological calpain inhibitors.
Main Results:
- Camptothecin treatment activated calpains in cortical neurons.
- Calpain inhibition (via deficiency, calpastatin, or inhibitors) prevented camptothecin-induced neuronal death.
- Calpain inhibition reduced and delayed p53 induction, cytochrome c release, and caspase activity.
Conclusions:
- Calpains are crucial mediators of DNA damage-induced neuronal death.
- Calpains act upstream of p53 induction, influencing subsequent caspase-dependent cell death pathways.
- Targeting calpains may offer a therapeutic strategy for conditions involving DNA damage-induced neuronal death, such as stroke.