Glycogen synthase kinase-3 is activated by matrix metalloproteinase-2 mediated proteolysis in cardiomyoblasts
Bibliographic record
Abstract
AIMS: Matrix metalloproteinase (MMP)-2 contributes to myocardial oxidative stress injury by degrading sarcomeric and cytoskeletal proteins in cardiomyocytes. Glycogen synthase kinase (GSK)-3beta is dysregulated during oxidative stress and is susceptible to proteolytic cleavage. Here we determined whether GSK-3beta is a MMP-2 substrate as a result of oxidative stress. METHODS AND RESULTS: MMP-2 and GSK-3beta were incubated and the cleavage fragments were identified by immunoblotting and silver stain. The intact protein and its primary cleavage fragment were subjected to trypsin digestion and the resultant peptides were analysed by LC-MS/MS. GSK-3beta kinase activity was measured using a peptide substrate and [gamma-(32)P]-ATP. Oxidative stress in H9c2 cardiomyoblasts was induced by H(2)O(2) and the levels and activities of MMP-2 and GSK-3beta were measured. Incubation of 47 kDa GSK-3beta with MMP-2 resulted in the time- and concentration-dependant cleavage of GSK-3beta as seen by appearance of an approximately 30 kDa fragment. MS analysis and Mascot database search yielded a peptide with an amino acid sequence of GSK-3beta lacking the N-terminal region. GSK-3beta kinase activity was significantly increased upon incubation with MMP-2 which was abrogated by the MMP inhibitor GM-6001. H(2)O(2) challenge of H9c2 cardiomyoblasts significantly increased the activity and level of MMP-2, reduced the level of GSK-3beta, and significantly increased GSK-3beta kinase activity. Both the loss of intact GSK-3beta and increase in its kinase activity were reduced with MMP inhibitors. MMP-2 pull-down assays in H9c2 cell lysates showed the association of MMP-2 with GSK-3beta. CONCLUSION: GSK-3beta may be a target of MMP-2 and its cleavage by MMP-2 enhances its kinase activity. MMP-2 may cleave off the N-terminal of GSK-3beta where the inhibitory phosphorylation of serine-9 occurs. MMP-2-mediated augmentation of GSK-3beta kinase activity may contribute to cardiac injury resulting from enhanced oxidative stress.
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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 | 0.001 |
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".