Extensive autolytic fragmentation of membranous versus cytosolic calpain following myocardial ischemia–reperfusion
Bibliographic record
Abstract
We investigated calpain activation in the heart during ischemia-reperfusion (I-R) by immunologically mapping the fragmentation patterns of calpain and selected calpain substrates. Western blots showed the intact 78 kDa large subunit of membrane-associated calpain was autolytically fragmented to 56 and 43 kDa signature immunopeptides following I-R. Under these conditions, the 78 kDa calpain large subunit from crude cytosolic fractions was markedly less fragmented, with only weakly stained autolytic peptides detected at higher molecular weights (70 and 64 kDa). Western blots also showed corresponding calpain-like degradation products (150 and 145 kDa) of membrane-associated alpha-fodrin (240 kDa) following I-R, but in crude myofibrils alpha-fodrin degradation occurred in a manner uncharacteristic of calpain. For control hearts perfused in the absence of ischemia, autolytic fragmentation of calpain and calpain-like alpha-fodrin degradation were completely absent from most subcellular fractions. The exception was sarcolemma-enriched membranes, where significant calpain autolysis and calpain-like alpha-fodrin degradation were detected. In purified sarcoplasmic reticulum membranes, RyR2 and SERCA2 proteins were also highly degraded, but for RyR2 this did not occur in a manner characteristic of calpain. When I-R-treated hearts were perfused with peptidyl calpain inhibitors (ALLN or ALLM; 25 micromol/L), calpain autolysis and calpain-like degradation of alpha-fodrin were equally attenuated by each inhibitor. However, only ALLN protected against early loss of developed pressure in hearts following I-R, with no functionally protective effect of ALLM observed. Our studies suggest calpain is preferentially activated at membranes following I-R, possibly contributing to impaired ion channel function implicated by others in I-R injury.
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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 | 0.000 | 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".