Ablation of triadin causes loss of cardiac Ca 2+ release units, impaired excitation-contraction coupling, and cardiac arrhythmias

Nagesh Chopra, Tao Yang, Parisa Asghari, Edwin D. Moore, Sabine Huke, Brandy Akin, Robert A. Cattolica, Claudio F. Perez, Thinn Hlaing, Barbara E C Knollmann-Ritschel, Larry R. Jones, Isaac N Pessah, Paul D. Allen, Clara Franzini-Armstrong, Björn C. Knollmann

Research output: Contribution to journalArticle

93 Scopus citations

Abstract

Heart muscle excitation-contraction (E-C) coupling is governed by Ca 2+ release units (CRUs) whereby Ca 2+ influx via L-type Ca 2+ channels (Cav1.2) triggers Ca 2+ release from juxtaposed Ca 2+ release channels (RyR2) located in junctional sarcoplasmic reticulum (jSR). Although studies suggest that the jSR protein triadin anchors cardiac calsequestrin (Casq2) to RyR2, its contribution to E-C coupling remains unclear. Here, we identify the role of triadin using mice with ablation of the Trdn gene (Trdn -/-). The structure and protein composition of the cardiac CRU is significantly altered in Trdn -/- hearts. jSR proteins (RyR2, Casq2, junctin, and juncto- philin 1 and 2) are significantly reduced in Trdn -/-hearts, whereas Cav1.2 and SERCA2a remain unchanged. Electron microscopy shows fragmentation and an overall 50% reduction in the contacts between jSR and T-tubules. Immunolabeling experiments show reduced colocalization of Cav1.2 with RyR2 and substantial Casq2 labeling outside of the jSR in Trdn -/-myocytes. CRU function is impaired in Trdn -/- myocytes, with reduced SR Ca 2+ release and impaired negative feedback of SR Ca 2+ release on Cav1.2 Ca 2+ currents (I Ca). Uninhibited Ca 2+ influx via I Ca likely contributes to Ca 2+ overload and results in spontaneous SR Ca 2+ releases upon β-adrenergic receptor stimulation with isoproterenol in Trdn -/- myocytes, and ventricular arrhythmias in Trdn -/- mice. We conclude that triadin is critically important for maintaining the structural and functional integrity of the cardiac CRU; triadin loss and the resulting alterations in CRU structure and protein composition impairs E-C coupling and renders hearts susceptible to ventricular arrhythmias.

Original languageEnglish (US)
Pages (from-to)7636-7641
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume106
Issue number18
DOIs
StatePublished - May 5 2009

Keywords

  • Calsequestrin
  • Cardiac muscle
  • Cav1.2
  • RyR2
  • Sarcoplasmic reticulum

ASJC Scopus subject areas

  • General

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    Chopra, N., Yang, T., Asghari, P., Moore, E. D., Huke, S., Akin, B., Cattolica, R. A., Perez, C. F., Hlaing, T., Knollmann-Ritschel, B. E. C., Jones, L. R., Pessah, I. N., Allen, P. D., Franzini-Armstrong, C., & Knollmann, B. C. (2009). Ablation of triadin causes loss of cardiac Ca 2+ release units, impaired excitation-contraction coupling, and cardiac arrhythmias. Proceedings of the National Academy of Sciences of the United States of America, 106(18), 7636-7641. https://doi.org/10.1073/pnas.0902919106