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An EF-hand in the sodium channel couples intracellular calcium to cardiac excitability

Nature Structural & Molecular Biology volume 11, pages 219–225 (2004)Cite this article

Abstract

Sodium channels initiate the electrical cascade responsible for cardiac rhythm, and certain life-threatening arrhythmias arise from Na+ channel dysfunction. We propose a novel mechanism for modulation of Na+ channel function whereby calcium ions bind directly to the human cardiac Na+ channel (hH1) via an EF-hand motif in the C-terminal domain. A functional role for Ca2+ binding was identified electrophysiologically, by measuring Ca2+-induced modulation of hH1. A small hH1 fragment containing the EF-hand motif was shown to form a structured domain and to bind Ca2+ with affinity characteristic of calcium sensor proteins. Mutations in this domain reduce Ca2+ affinity in vitro and the inactivation gating effects of Ca2+ in electrophysiology experiments. These studies reveal the molecular basis for certain forms of long QT syndrome and other arrhythmia-producing syndromes, and suggest a potential pharmacological target for antiarrhythmic drug design.

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Figure 1: Structure-based sequence alignment and homology modeling of the proximal region of the hH1 C terminus.
Figure 2: Voltage-dependent availability of hH1 is Ca2+ sensitive.
Figure 3: Structural characterization and calcium binding to hH1-EF, and electrophysiological characterization of Ca2+-dependent inactivation effects caused by hH1 EF-hand mutations.

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Acknowledgements

We thank S. Stepanovic for invaluable technical assistance, L. Mizoue for providing pSV278 and N. Pokala (University of California Berkeley) for his generous gift of pSV272. This work was supported by operating grants (to M.E.A., T.P.L., W.J.C. and J.R.B.) from the US National Institutes of Health and a predoctoral fellowship from the American Heart Association.

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Author notes

  1. Tammy L Wingo and Vikas N Shah: These authors contributed equally to this work.

Authors and Affiliations

  1. Department of Pharmacology, Vanderbilt University, Nashville, 37232, Tennessee, USA

    Tammy L Wingo, Mark E Anderson, Terry P Lybrand & Jeffrey R Balser

  2. Department of Biochemistry, Vanderbilt University, Nashville, 37232, Tennessee, USA

    Vikas N Shah & Walter J Chazin

  3. Department of Medicine, Vanderbilt University, Nashville, 37232, Tennessee, USA

    Mark E Anderson

  4. Department of Chemistry, Vanderbilt University, Nashville, 37232, Tennessee, USA

    Terry P Lybrand

  5. Department of Physics, Vanderbilt University, Nashville, 37232, Tennessee, USA

    Walter J Chazin

  6. Department of Anesthesiology, Vanderbilt University, Nashville, 37232, Tennessee, USA

    Jeffrey R Balser

  7. Center for Structural Biology, Vanderbilt University, Nashville, 37232, Tennessee, USA

    Vikas N Shah, Terry P Lybrand & Walter J Chazin

Authors
  1. Tammy L Wingo
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Correspondence to Walter J Chazin or Jeffrey R Balser.

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Wingo, T., Shah, V., Anderson, M. et al. An EF-hand in the sodium channel couples intracellular calcium to cardiac excitability. Nat Struct Mol Biol 11, 219–225 (2004). https://doi.org/10.1038/nsmb737

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