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Chiang DY, Li N, Wang Q, Alsina KM, Quick AP, Reynolds JO, Wang G, Skapura D, Voigt N, Dobrev D, Wehrens XHT. Impaired local regulation of ryanodine receptor type 2 by protein phosphatase 1 promotes atrial fibrillation. Cardiovasc Res 2014; 103:178-87. [PMID: 24812280 DOI: 10.1093/cvr/cvu123] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
AIMS Altered Ca(2+) handling in atrial fibrillation (AF) has been associated with dysregulated protein phosphatase 1 (PP1) and subcellular heterogeneities in protein phosphorylation, but the underlying mechanisms remain unclear. This is due to a lack of investigation into the local, rather than global, regulation of PP1 on different subcellular targets such as ryanodine receptor type 2 (RyR2), especially in AF. METHODS AND RESULTS We tested the hypothesis that impaired local regulation of PP1 causes RyR2 hyperphosphorylation thereby promoting AF susceptibility. To specifically disrupt PP1's local regulation of RyR2, we used the spinophilin knockout (Sp(-/-)) mice (Mus musculus) since PP1 is targeted to RyR2 via spinophilin. Without spinophilin, the interaction between PP1 and RyR2 was reduced by 64%, while RyR2 phosphorylation was increased by 43% at serine (S)2814 but unchanged at S2808. Lipid bilayer experiments revealed that single RyR2 channels isolated from Sp(-/-) hearts had an increased open probability. Likewise, Ca(2+) spark frequency normalized to sarcoplasmic reticulum Ca(2+) content was also enhanced in Sp(-/-) atrial myocytes, but normalized by Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) inhibitors KN-93 and AIP and also by genetic inhibition of RyR2 S2814 phosphorylation. Finally, Sp(-/-) mice exhibited increased atrial ectopy and susceptibility to pacing-induced AF, both of which were also prevented by the RyR2 S2814A mutation. CONCLUSION PP1 regulates RyR2 locally by counteracting CaMKII phosphorylation of RyR2. Decreased local PP1 regulation of RyR2 contributes to RyR2 hyperactivity and promotes AF susceptibility. This represents a novel mechanism for subcellular modulation of calcium channels and may represent a potential drug target of AF.
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Affiliation(s)
- David Y Chiang
- Cardiovascular Research Institute, Baylor College of Medicine, Houston, TX, USA Department of Molecular Physiology and Biophysics, Baylor College of Medicine, Houston, TX, USA Interdepartmental Program in Translational Biology and Molecular Medicine, Baylor College of Medicine, Houston, TX, USA
| | - Na Li
- Cardiovascular Research Institute, Baylor College of Medicine, Houston, TX, USA Department of Molecular Physiology and Biophysics, Baylor College of Medicine, Houston, TX, USA
| | - Qiongling Wang
- Cardiovascular Research Institute, Baylor College of Medicine, Houston, TX, USA Department of Molecular Physiology and Biophysics, Baylor College of Medicine, Houston, TX, USA
| | - Katherina M Alsina
- Cardiovascular Research Institute, Baylor College of Medicine, Houston, TX, USA Department of Molecular Physiology and Biophysics, Baylor College of Medicine, Houston, TX, USA
| | - Ann P Quick
- Cardiovascular Research Institute, Baylor College of Medicine, Houston, TX, USA Department of Molecular Physiology and Biophysics, Baylor College of Medicine, Houston, TX, USA
| | - Julia O Reynolds
- Cardiovascular Research Institute, Baylor College of Medicine, Houston, TX, USA Department of Molecular Physiology and Biophysics, Baylor College of Medicine, Houston, TX, USA
| | - Guoliang Wang
- Cardiovascular Research Institute, Baylor College of Medicine, Houston, TX, USA
| | - Darlene Skapura
- Cardiovascular Research Institute, Baylor College of Medicine, Houston, TX, USA Department of Molecular Physiology and Biophysics, Baylor College of Medicine, Houston, TX, USA
| | - Niels Voigt
- Institute of Pharmacology, Faculty of Medicine, University Duisburg-Essen, Essen, Germany
| | - Dobromir Dobrev
- Institute of Pharmacology, Faculty of Medicine, University Duisburg-Essen, Essen, Germany
| | - Xander H T Wehrens
- Cardiovascular Research Institute, Baylor College of Medicine, Houston, TX, USA Department of Molecular Physiology and Biophysics, Baylor College of Medicine, Houston, TX, USA Department of Medicine (Cardiology), Baylor College of Medicine, Houston, TX, USA
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Beavers DL, Wang W, Ather S, Voigt N, Garbino A, Dixit SS, Landstrom AP, Li N, Wang Q, Olivotto I, Dobrev D, Ackerman MJ, Wehrens XHT. Mutation E169K in junctophilin-2 causes atrial fibrillation due to impaired RyR2 stabilization. J Am Coll Cardiol 2013; 62:2010-9. [PMID: 23973696 DOI: 10.1016/j.jacc.2013.06.052] [Citation(s) in RCA: 148] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/15/2013] [Revised: 05/24/2013] [Accepted: 06/05/2013] [Indexed: 02/07/2023]
Abstract
OBJECTIVES This study sought to study the role of junctophilin-2 (JPH2) in atrial fibrillation (AF). BACKGROUND JPH2 is believed to have an important role in sarcoplasmic reticulum (SR) Ca(2+) handling and modulation of ryanodine receptor Ca(2+) channels (RyR2). Whereas defective RyR2-mediated Ca(2+) release contributes to the pathogenesis of AF, nothing is known about the potential role of JPH2 in atrial arrhythmias. METHODS Screening 203 unrelated hypertrophic cardiomyopathy patients uncovered a novel JPH2 missense mutation (E169K) in 2 patients with juvenile-onset paroxysmal AF (pAF). Pseudoknock-in (PKI) mouse models were generated to determine the molecular defects underlying the development of AF caused by this JPH2 mutation. RESULTS PKI mice expressing E169K mutant JPH2 exhibited a higher incidence of inducible AF than wild type (WT)-PKI mice, whereas A399S-PKI mice expressing a hypertrophic cardiomyopathy-linked JPH2 mutation not associated with atrial arrhythmias were not significantly different from WT-PKI. E169K-PKI but not A399A-PKI atrial cardiomyocytes showed an increased incidence of abnormal SR Ca(2+) release events. These changes were attributed to reduced binding of E169K-JPH2 to RyR2. Atrial JPH2 levels in WT-JPH2 transgenic, nontransgenic, and JPH2 knockdown mice correlated negatively with the incidence of pacing-induced AF. Ca(2+) spark frequency in atrial myocytes and the open probability of single RyR2 channels from JPH2 knockdown mice was significantly reduced by a small JPH2-mimicking oligopeptide. Moreover, patients with pAF had reduced atrial JPH2 levels per RyR2 channel compared to sinus rhythm patients and an increased frequency of spontaneous Ca(2+) release events. CONCLUSIONS Our data suggest a novel mechanism by which reduced JPH2-mediated stabilization of RyR2 due to loss-of-function mutation or reduced JPH2/RyR2 ratios can promote SR Ca(2+) leak and atrial arrhythmias, representing a potential novel therapeutic target for AF.
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Affiliation(s)
- David L Beavers
- Cardiovascular Research Institute, Dept of Molecular Physiology & Biophysics and Medicine (Cardiology), Baylor College of Medicine, Houston, TX
| | - Wei Wang
- Cardiovascular Research Institute, Dept of Molecular Physiology & Biophysics and Medicine (Cardiology), Baylor College of Medicine, Houston, TX
| | - Sameer Ather
- Cardiovascular Research Institute, Dept of Molecular Physiology & Biophysics and Medicine (Cardiology), Baylor College of Medicine, Houston, TX
| | - Niels Voigt
- Institute of Pharmacology, Faculty of Medicine, University of Duisburg-Essen, Essen, Germany
| | - Alejandro Garbino
- Cardiovascular Research Institute, Dept of Molecular Physiology & Biophysics and Medicine (Cardiology), Baylor College of Medicine, Houston, TX
| | - Sayali S Dixit
- Cardiovascular Research Institute, Dept of Molecular Physiology & Biophysics and Medicine (Cardiology), Baylor College of Medicine, Houston, TX
| | - Andrew P Landstrom
- Depts of Medicine, Pediatrics, and Molecular Pharmacology & Experimental Therapeutics/Divisions of Cardiovascular Diseases and Pediatric Cardiology; Windland Smith Rice Sudden Death Genomics Laboratory, Mayo Clinic, Rochester, MN
| | - Na Li
- Cardiovascular Research Institute, Dept of Molecular Physiology & Biophysics and Medicine (Cardiology), Baylor College of Medicine, Houston, TX
| | - Qiongling Wang
- Cardiovascular Research Institute, Dept of Molecular Physiology & Biophysics and Medicine (Cardiology), Baylor College of Medicine, Houston, TX
| | - Iacopo Olivotto
- Careggi University Hospital, University of Florence, Florence, Italy
| | - Dobromir Dobrev
- Institute of Pharmacology, Faculty of Medicine, University of Duisburg-Essen, Essen, Germany
| | - Michael J Ackerman
- Depts of Medicine, Pediatrics, and Molecular Pharmacology & Experimental Therapeutics/Divisions of Cardiovascular Diseases and Pediatric Cardiology; Windland Smith Rice Sudden Death Genomics Laboratory, Mayo Clinic, Rochester, MN
| | - Xander H T Wehrens
- Cardiovascular Research Institute, Dept of Molecular Physiology & Biophysics and Medicine (Cardiology), Baylor College of Medicine, Houston, TX
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