Role of poly(ADP-ribose) polymerase in rapid intracellular acidification induced by alkylating DNA damage
Bibliographic record
Abstract
In response to high levels of DNA damage, catalytic activation of the nuclear enzyme poly(ADP-ribose) polymerase (PARP) triggers necrotic death because of rapid consumption of its substrate beta-nicotinamide adenine dinucleotide and consequent depletion of ATP. We examined whether there are other consequences of PARP activation that could contribute to cell death. Here, we show that PARP activation reaction in vitro becomes acidic with release of protons during hydrolysis of beta-nicotinamide adenine dinucleotide. In the cellular context, we show that Molt 3 cells respond to DNA damage by the alkylating agent N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) with a dose-dependent acidification within 30 min. Whereas acidification by 0.15 pH units induced by 10 microM MNNG is reversed within 1 h, 100 , microinduced acidification by 0.5-0.6 pH units is persistent up to 7 h. Acidification is a general DNA damage response because H(2)O(2) exposure also acidifies Molt 3 cells, and MNNG causes acidification in Jurkat, U937, or HL-60 leukemia cells and in PARP(+/+) fibroblasts. Acidification is significantly decreased in the presence of PARP inhibitors or in PARP(-/-) fibroblasts, suggesting a major role for PARP activation in acidification. Inhibition of proton export through ATP-dependent Na(+)/H(+) exchanger is another major cause of acidification. Using the pH clamp method to either suppress or introduce changes in cellular pH, we show that brief acidification by 0.5-0.6 pH units may be a negative regulator of apoptosis while permitting necrotic death of cells with extensively damaged DNA.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| 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 | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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 source (direct Gemma or distilled Codex), 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".