Nuclear MMP‐2: presence and activity in cardiac myocytes
Bibliographic record
Abstract
MMP‐2 is expressed in almost all heart cells and is found in subcellular compartments including the nucleus. MMP‐2 can be directly activated by oxidative stress (as peroxynitrite). Its activity is further regulated by its phosphorylation. To better study nuclear MMP‐2 in the heart, we extracted the nuclear, cytosolic and membrane fractions from isolated rat hearts (briefly perfused to clear them of blood). Western Blots for lamin A/C (nucleus), GAPDH (cytosol) and VDAC/Porin (membrane) were used as specific markers to confirm fraction purity. Gelatin zymography of these fractions revealed MMP‐2 but not MMP‐9 activities and MMP‐2 activity was about 15 times higher in the cytoplasm than in the nucleus. Interestingly, Western blot analysis showed that MMP‐2 is present in similar amounts both in the nucleus and in the cytoplasm. In order to characterize possible regulators of MMP‐2 activity, we analyzed for the presence of tissue inhibitors of metalloproteases (TIMPs). Western blots revealed that all forms of TIMPs (1–4) are found in the cytoplasm, TIMP‐4 is also present in the membrane fraction, and no TIMP was detected in the nucleus. Our data suggest that myocardial MMP‐2 activity in the nucleus is regulated by a mechanism different from inhibition by TIMPs, possibly by its phosphorylation. Funding: Canadian Institutes of Health Research.
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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) | 0.002 | 0.001 |
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".