The Chk1/Cdc25A Pathway as Activators of the Cell Cycle in Neuronal Death Induced by Camptothecin
Bibliographic record
Abstract
Cell cycle regulators appear to play a paradoxical role in neuronal death. We have shown previously that cyclin-dependent kinases (CDKs), along with their downstream effectors, Rb (retinoblastoma) and E2F/DP1 (E2 promoter binding factor/deleted in polyposis 1), regulate neuronal death evoked by the DNA damaging agent camptothecin. However, the mechanism by which CDKs are activated in this model is unclear. The cell division cycle 25A (Cdc25A) phosphatase is a critical regulator of cell cycle CDKs in proliferating cells. In cortical neurons, we presently show that expression of Cdc25A promotes death even in the absence of DNA damage. Importantly, Cdc25A activity is rapidly increased during DNA damage treatment. Inhibition of Cdc25A blocks death and reduces cyclin D1-associated kinase activity and Rb phosphorylation. This indicates that endogenous Cdc25A activity is important for regulation of cell cycle-mediated neuronal death. We also examined how Cdc25A activity is regulated after DNA damage. Cultured embryonic cortical neurons have a significant basal activity of checkpoint kinase 1 (Chk1), a kinase that regulates cell cycle arrest. During camptothecin treatment of neurons, this activity is rapidly downregulated with a concomitant increase in Cdc25A activity. Importantly, expression of wild-type Chk1, but not kinase-dead Chk1, inhibits the camptothecin-induced increase in Cdc25A activity. In addition, Chk1 expression also promotes survival in the presence of the DNA-damaging agent. Together, our data suggest that a Chk1/Cdc25A activity participates in activation of a cell cycle pathway-mediated death signal in neurons. These data also define how a proliferative signal may be abnormally activated in a postmitotic environment.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".