Abstract
Rationale: The cardiac sodium channel NaV1.5 has a fundamental role in excitability and conduction. Previous studies have shown that sodium channels cluster together in specific cellular subdomains. Their association with intracellular organelles in defined regions of the myocytes, and the functional consequences of that association, remain to be defined. Objective: To characterize a subcellular domain formed by sodium channel clusters in the crest region of the myocytes and the subjacent subsarcolemmal mitochondria. Methods and Results: Through a combination of imaging approaches including super-resolution microscopy and electron microscopy we identified, in adult cardiac myocytes, a NaV1.5 subpopulation in close proximity to subjacent subsarcolemmal mitochondria; we further found that subjacent subsarcolemmal mitochondria preferentially host the mitochondrial NCLX (Na+/Ca2+exchanger). This anatomic proximity led us to investigate functional changes in mitochondria resulting from sodium channel activity. Upon TTX (tetrodotoxin) exposure, mitochondria near NaV1.5 channels accumulated more Ca2+and showed increased reactive oxygen species production when compared with interfibrillar mitochondria. Finally, crosstalk between NaV1.5 channels and mitochondria was analyzed at a transcriptional level. We found that SCN5A (encoding NaV1.5) and SLC8B1 (which encode NaV1.5 and NCLX, respectively) are negatively correlated both in a human transcriptome data set (Genotype-Tissue Expression) and in human-induced pluripotent stem cell-derived cardiac myocytes deficient in SCN5A. Conclusions: We describe an anatomic hub (a couplon) formed by sodium channel clusters and subjacent subsarcolemmal mitochondria. Preferential localization of NCLX to this domain allows for functional coupling where the extrusion of Ca2+from the mitochondria is powered, at least in part, by the entry of sodium through NaV1.5 channels. These results provide a novel entry-point into a mechanistic understanding of the intersection between electrical and structural functions of the heart.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 419-432 |
| Number of pages | 14 |
| Journal | Circulation research |
| Volume | 128 |
| Issue number | 3 |
| DOIs | |
| State | Published - Feb 5 2021 |
Funding
Supported by National Institutes of Health (NIH) RO1-HL134328, RO1-HL136179, 5R01HL148609-02, and RO1-HL145911 (M. Delmar), the Wilton W. Webster Fellowship in Pediatric Electrophysiology from the Heart Rhythm Society (M. Pérez-Hernández), a Leducq Foundation Transatlantic network of Excellence (M. Delmar and P. Burridge) and the Swiss National Science Foundation P1BEP3_172237 (S. Vermij). Microscopy Laboratory is supported by NIH/NCI P30CA016087 and S10 ODO019974-01A1. We thank Chris Petzold for EM sample preparation and image acquisition. The GTEx Project was supported by the Common Fund of the Office of the Director of the National Institutes of Health, and by the National Cancer Institute (NCI), National Human Genome Research Institute (NHGRI), National Heart, Lung, and Blood Institute (NHLBI), National Institute on Drug Abuse (NIDA), National Institute of Mental Health (NIMH), and National Institute of Neurological Disorders and Stroke (NINDS).
Keywords
- cardiac myocytes
- mitochondria
- sodium channels
ASJC Scopus subject areas
- Physiology
- Cardiology and Cardiovascular Medicine