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Deficient ryanodine receptor S-nitrosylation increases sarcoplasmic reticulum calcium leak and arrhythmogenesis in cardiomyocytes

Gonzalez, Daniel R., Beigi, Farideh, Treuer, Adriana V., Hare, Joshua M.
Proceedings of the National Academy of Sciences of the United States of America 2007 v.104 no.51 pp. 20612-20617
calcium, cardiomyocytes, heart diseases, homeostasis, neuronal nitric oxide synthase, oxidation, phenotype, phosphorylation, sarcoplasmic reticulum, stoichiometry, thiols
Altered Ca²⁺ homeostasis is a salient feature of heart disease, where the calcium release channel ryanodine receptor (RyR) plays a major role. Accumulating data support the notion that neuronal nitric oxide synthase (NOS1) regulates the cardiac RyR via S-nitrosylation. We tested the hypothesis that NOS1 deficiency impairs RyR S-nitrosylation, leading to altered Ca²⁺ homeostasis. Diastolic Ca²⁺ levels are elevated in NOS1⁻/⁻ and NOS1/NOS3⁻/⁻ but not NOS3⁻/⁻ myocytes compared with wild-type (WT), suggesting diastolic Ca²⁺ leakage. Measured leak was increased in NOS1⁻/⁻ and NOS1/NOS3⁻/⁻ but not in NOS3⁻/⁻ myocytes compared with WT. Importantly, NOS1⁻/⁻ and NOS1/NOS3⁻/⁻ myocytes also exhibited spontaneous calcium waves. Whereas the stoichiometry and binding of FK-binding protein 12.6 to RyR and the degree of RyR phosphorylation were not altered in NOS1⁻/⁻ hearts, RyR2 S-nitrosylation was substantially decreased, and the level of thiol oxidation increased. Together, these findings demonstrate that NOS1 deficiency causes RyR2 hyponitrosylation, leading to diastolic Ca²⁺ leak and a proarrhythmic phenotype. NOS1 dysregulation may be a proximate cause of key phenotypes associated with heart disease.