Calcium‐dependent Nedd4‐2 upregulation mediates degradation of the cardiac sodium channel Nav1.5: implications for heart failure
Why this work is in the frame
A frame that forgets how it found something cannot be audited. These are the routes that admitted this work.
Bibliographic record
Abstract
Abstract Aim Reductions in voltage‐gated sodium channel (Nav1.5) function/expression provide a slowed‐conduction substrate for cardiac arrhythmias. Nedd4‐2, which is activated by calcium, post‐translationally modulates Nav1.5. We aim to investigate whether elevated intracellular calcium ([Ca 2+ ] i ) reduces Nav1.5 through Nedd4‐2 and its role in heart failure ( HF ). Methods Using a combination of biochemical, electrophysiological, cellular and in vivo methods, we tested the effect and mechanism of calcium on Nedd4‐2 and in turn Nav1.5. Results Increased [Ca 2+ ] i , following 24‐h ionomycin treatment, decreased sodium current ( I N a ) density and Nav1.5 protein without altering its mRNA in both neonatal rat cardiomyocytes ( NRCM s) and HEK 293 cells stably expressing Nav1.5. The calcium chelator BAPTA ‐ AM restored the reduced Nav1.5 and I N a in NRCM s pre‐treated by ionomycin. Nav1.5 was decreased by Nedd4‐2 transfection and further decreased by 6‐h ionomycin treatment. These effects were not observed in cells transfected with the catalytically inactive mutant, Nedd4‐2 C801S, or with Y1977A‐Nav1.5 mutant containing the impaired Nedd4‐2 binding motif. Furthermore, elevated [Ca 2+ ] i increased Nedd4‐2, the interaction between Nedd4‐2 and Nav1.5, and Nav1.5 ubiquitination. Nav1.5 protein is decreased, whereas Nedd4‐2 is increased in volume‐overload HF rat hearts, with increased co‐localization of Nav1.5 with ubiquitin or Nedd4‐2 as indicated by immunofluorescence staining. BAPTA ‐ AM rescued the reduced Nav1.5 protein, I N a and increased Nedd4‐2 in hypertrophied NRCM s induced by isoproterenol or angiotensin II . Conclusion Calcium‐mediated increases in Nedd4‐2 downregulate Nav1.5 by ubiquitination. Nav1.5 is downregulated and co‐localizes with Nedd4‐2 and ubiquitin in failing rat heart. These data suggest a role of Nedd4‐2 in Nav1.5 downregulation in HF .
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.
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 | 0.001 | 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 it