A calcium sensor in the sodium channel modulates cardiac excitability

Hanno L. Tan, Sabina Kupershmidt, Rong Zhang, Svetlana Stepanovic, Dan M. Roden, Arthur A.M. Wilde, Mark E. Anderson, Jeffrey R. Balser

Research output: Contribution to journalArticlepeer-review

182 Scopus citations


Sodium channels are principal molecular determinants responsible for myocardial conduction and maintenance of the cardiac rhythm. Calcium ions (Ca2+) have a fundamental role in the coupling of cardiac myocyte excitation and contraction, yet mechanisms whereby intracellular Ca2+ may directly modulate Na channel function have yet to be identified. Here we show that calmodulin (CaM), a ubiquitous Ca2+-sensing protein, binds to the carboxy-terminal 'IQ' domains of the human cardiac Na channel (hH1) in a Ca2+-dependent manner. This binding interaction significantly enhances slow inactivation-a channel-gating process linked to life-threatening idiopathic ventricular arrhythmias2,3. Mutations targeted to the IQ domain disrupted CaM binding and eliminated Ca2+/CaM-dependent slow inactivation, whereas the gating effects of Ca2+/CaM were restored by intracellular application of a peptide modelled after the IQ domain. A naturally occurring mutation (A1924T) in the IQ domain altered hH1 function in a manner characteristic of the Brugada arrhythmia syndrome4,5, but at the same time inhibited slow inactivation induced by Ca2+/CaM, yielding a clinically benign (arrhythmia free) phenotype.

Original languageEnglish (US)
Pages (from-to)442-447
Number of pages6
Issue number6870
StatePublished - Jan 24 2002
Externally publishedYes

ASJC Scopus subject areas

  • General


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