Intersection of chronic contractile activity and lysosomal defects in mediating lysosomal adaptations in skeletal muscle cells
Bibliographic record
Abstract
Mitophagy is the cellular process that serves to degrade mitochondria when these organelles lose their potential for ATP production, generate excessive reactive oxygen species, and exhibit a reduced membrane potential. The terminal step of mitophagy is mediated by the lysosome, the organelle that degrades defective cellular cargos. Electron microscopy evidence shows that lysosomes become defective in aging muscle, as well as in lysosomal storage diseases, ultimately leading to cellular pathology. Recent research has shown that chronic contractile activity can induce rapid increases in lysosomal gene and protein expression in muscle. Our objective is to investigate whether this adaptation leads to greater lysosomal content and function, thus enhancing the capacity to degrade defective mitochondria. This result would suggest that reduced lysosomal function in muscle could be rescued by exercise. However, the underlying mechanisms mediating lysosomal turnover and function are not clear. To study this, we simulated lysosomal dysfunction in C2C12 myotubes using short-interfering RNA targeting the lysosomal calcium channel mucolipin-1 (MCOLN1) or the autophagosome-lysosome fusion protein, lysosomal-associated membrane protein 2 (LAMP2). We achieved a 60-70% knockdown, as well as a 40-50% knockdown, after a 24-hour transfection, in each lysosomal marker, respectively. The cells were then subjected to four days of electrical stimulation-induced chronic contractile activity. Changes in gene expression were measured via qPCR, while protein content was measured via western blotting techniques, in addition to lysosomal content and functional assessments via confocal microscopy and flow cytometry. Silencing of MCOLN1 or LAMP2 both resulted in a compensatory increase in the transcript and protein levels of lysosomal genes, including the lysosomal transcription factors TFEB, TFE3, as well as lysosomal cathepsins B and D. Interestingly, contractile activity superimposed on the MCOLN1 or LAMP2 knockdown did not further enhance these compensatory increases. This suggests that contractile activity and the cellular signaling that arises from lysosomal defects, operate similarly to initiate the biogenesis of lysosomes as a negative feedback mechanism to enhance lysosomal degradation capacity. The nature of these signaling pathways, potentially involving changes in lysosome-derived intracellular calcium driving organelle synthesis, recycling, or degradation represent novel avenues for upcoming research investigating skeletal muscle phenotypic adaptations. This work is supported by NSERC. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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".