Cyclin-Dependent Kinases and P53 Pathways Are Activated Independently and Mediate Bax Activation in Neurons after DNA Damage

Abstract

DNA damage has been implicated as one important initiator of cell death in neuropathological conditions such as stroke. Accordingly, it is important to understand the signaling processes that control neuronal death induced by this stimulus. Previous evidence has shown that the death of embryonic cortical neurons treated with the DNA-damaging agent camptothecin is dependent on the tumor suppressor p53 and cyclin-dependent kinase (CDK) activity and that the inhibition of either pathway alone leads to enhanced and prolonged survival. We presently show that p53 and CDKs are activated independently on parallel pathways. An increase in p53 protein levels, nuclear localization, and DNA binding that result from DNA damage are not affected by the inhibition of CDK activity. Conversely, no decrease in retinoblastoma protein (pRb) phosphorylation was observed in p53-deficient neurons that were treated with camptothecin. However, either p53 deficiency or the inhibition of CDK activity alone inhibited Bax translocation, cytochrome c release, and caspase-3-like activation. Taken together, our results indicate that p53 and CDK are activated independently and then act in concert to control Bax-mediated apoptosis.

p53, Apaf-1, caspase-3, and -9 are dispensable for Cdk5 activation during cell death

“…53 CPT inhibits DNA topoisomerase I. 54 All lead to apoptosis in a variety of cells. [55][56][57][58] Death induced in C8 and A9 cells after exposure to EtOH (2.5%), CHX (25 mg/ml), or CPT (20 mM) for 18 h was determined by trypan blue (TB) exclusion assay.…”

“…54,59,60 To evaluate the cell death induced under our conditions, we employed several markers to characterize apoptotic cell death, including examination of DNA fragmentation both by gel electrophoresis and in situ detection of fragmented DNA by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL), measurement of nuclear fragmentation by Hoechst staining, and activation of caspase-3 and cleavage of poly (ADP ribose) polymerase (PARP).…”

Ataxia Telangiectasia-mutated Protein Can Regulate p53 and Neuronal Death Independent of Chk2 in Response to DNA Damage

“…This genome surveillance function of p53 is also critical in neurons (10 -13). In this regard, p53 is activated and required for neuronal injury induced by DNA-damaging agents (14,15), excitotoxicity (11,16) dopaminergic toxins (4), and ischemia (12). Although this evidence exemplifies the importance of p53 in neuronal death, the signals that link DNA damage to p53 induction and activation are not clear.…”

“…We have previously reported that cortical neurons exposed to the DNA-damaging agents such as camptothecin display increased p53 levels and a requirement for p53 in death (14,31). However the mechanism by which this occurs is unknown.…”

Origin licensing and programmed cell death: a hypothesis

“…9 However, other studies provide equally compelling evidence that CDK activation occurs upstream of caspases and/or the mitochondrial events that often trigger caspase activation. 17,33 The fact that Cdc6 is destroyed by either proteasome or caspase-dependent pathways depending on the apoptotic trigger may shed some light here. The proteasome-dependent pathway that responds to a DNA damaging drug clearly occurs either upstream of, or parallel to, caspase activation.…”