Cardiovascular Research Advance Access first published online on November 7, 2008
This version [Corrected Proof] published online on November 23, 2008
Cardiovascular Research, doi:10.1093/cvr/cvn303
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Defective domain–domain interactions within the ryanodine receptor as a critical cause of diastolic Ca2+ leak in failing hearts
1 Division of Cardiology, Department of Medicine and Clinical Science, Yamaguchi University Graduate School of Medicine, 1-1-1 Minamikogushi, Ube, Yamaguchi 755-8505, Japan
2 Boston Biomedical Research Institute, Watertown, MA 02472, USA
3 Department of Neurology, Harvard Medical School, Boston, MA 02115, USA
* Corresponding author. Tel: +81 836 22 2248; fax: +81 836 22 2246. E-mail address: yanoma{at}yamaguchi-u.ac.jp
Aims: A domain peptide (DP) matching the Gly2460–Pro2495 region of the cardiac type-2 ryanodine receptor (RyR2), DPc10, is known to mimic channel dysfunction associated with catecholaminergic polymorphic ventricular tachycardia (CPVT), owing to its interference in a normal interaction of the N-terminal (1–600) and central (2000–2500) domains (viz. domain unzipping). Using DPc10 and two other DPs harboring different mutation sites, we investigated the underlying mechanism of abnormal Ca2+ cycling in failing hearts.
Methods and results: Sarcoplasmic reticulum (SR) vesicles and cardiomyocytes were isolated from dog left ventricular muscles for Ca2+ leak and spark assays. The RyR2 moiety of the SR was fluorescently labelled with methylcoumarin acetate (MCA) using DPs corresponding to the 163–195 and 4090–4123 regions of RyR2 (DP163–195 and DP4090–4123, respectively) as site-directed carriers. Both DPs mediated a specific MCA fluorescence labelling of RyR2. Addition of either DP to the MCA-labelled SR induced domain unzipping, as evidenced by an increased accessibility of the bound MCA to a large-size fluorescence quencher. Both SR Ca2+ leak and Ca2+ spark frequency (SpF) were markedly increased in failing cardiomyocytes. Upon introduction of DP163–195 or DP4090–4123 into normal SR or cardiomyocytes, both Ca2+ leak and SpF increased to the levels comparable with those of failing myocytes. K201 (JTV519) suppressed all of the effects induced by DP163–195 (domain unzipping and increased Ca2+ leak and SpF) or those in failing cardiomyocytes, but did not suppress the effects induced by DP4090–4123.
Conclusion: Defective inter-domain interaction between N-terminal and central domains induces diastolic Ca2+ leak, leading to heart failure and lethal arrhythmia. Mutation at the C-terminal region seen in CPVT does not seem to communicate with the aforementioned N-terminal and central inter-domain interaction, although spontaneous Ca2+ leak is similarly induced.
KEYWORDS Calcium (cellular); Heart failure; Ion channels; SR (function)
Time for primary review: 22 days
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