Hypoxia reduces mature hERG channels through calpain up‐regulation
Bibliographic record
Abstract
Human ether‐a‐go‐go‐related gene ( hERG ) encodes the pore‐forming subunit of the rapidly activating delayed rectifier potassium current (I Kr ) potassium channel, which is important for cardiac repolarization. Impairment of hERG function is the primary cause of acquired long QT syndrome, which predisposes individuals to cardiac arrhythmias and sudden death. Patients with hypoxia due to conditions such as cardiac ischemia or obstructive sleep apnea display increased incidence of cardiac arrhythmias and sudden death. We sought to understand the mechanisms that underlie hypoxia‐associated cardiac arrhythmias. Using cell biology and electro‐physiologic techniques, we found that hypoxic culture of hERG‐expressing human embryonic kidney (HEK) cells and neonatal rat cardiomyocytes reduced hERG current/ I Kr and mature ERG channel expression with a concomitant increase in calpain expression. Calpain was actively released into the extracellular milieu and degraded cell‐surface hERG. In contrast to hERG, the ether‐a‐go‐go (EAG) channel was not reduced by hypoxic culture. By making chimeric channels between hERG and EAG, we identified that hypoxia‐induced calpain degraded hERG by targeting its extracellular S5‐pore linker. The scorpion toxin BeKm‐1, which is known to selectively bind to the S5‐pore linker of hERG, prevented hypoxia‐induced hERG reduction. Our data provide novel information about hypoxia‐mediated hERG dysfunction and may have biological and clinical implications in hypoxia‐associated diseases.—Lamothe, S. M., Song, W., Guo, J., Li, W., Yang, T., Baranchuk, A., Graham, C. H., Zhang, S. Hypoxia reduces mature hERG channels through calpain up‐regulation. FASEB J. 31, 5068–5077 (2017). www.fasebj.org
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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 | 0.000 |
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 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".