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Guo W, Sun B, Estillore JP, Wang R, Chen SRW. The central domain of cardiac ryanodine receptor governs channel activation, regulation, and stability. J Biol Chem 2020; 295:15622-15635. [PMID: 32878990 DOI: 10.1074/jbc.ra120.013512] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2020] [Revised: 08/25/2020] [Indexed: 11/06/2022] Open
Abstract
Structural analyses identified the central domain of ryanodine receptor (RyR) as a transducer converting conformational changes in the cytoplasmic platform to the RyR gate. The central domain is also a regulatory hub encompassing the Ca2+-, ATP-, and caffeine-binding sites. However, the role of the central domain in RyR activation and regulation has yet to be defined. Here, we mutated five residues that form the Ca2+ activation site and 10 residues with negatively charged or oxygen-containing side chains near the Ca2+ activation site. We also generated eight disease-associated mutations within the central domain of RyR2. We determined the effect of these mutations on Ca2+, ATP, and caffeine activation and Mg2+ inhibition of RyR2. Mutating the Ca2+ activation site markedly reduced the sensitivity of RyR2 to Ca2+ and caffeine activation. Unexpectedly, Ca2+ activation site mutation E3848A substantially enhanced the Ca2+-independent basal activity of RyR2, suggesting that E3848A may also affect the stability of the closed state of RyR2. Mutations in the Ca2+ activation site also abolished the effect of ATP/caffeine on the Ca2+-independent basal activity, suggesting that the Ca2+ activation site is also a critical determinant of ATP/caffeine action. Mutating residues with negatively charged or oxygen-containing side chains near the Ca2+ activation site significantly altered Ca2+ and caffeine activation and reduced Mg2+ inhibition. Furthermore, disease-associated RyR2 mutations within the central domain significantly enhanced Ca2+ and caffeine activation and reduced Mg2+ inhibition. Our data demonstrate that the central domain plays an important role in channel activation, channel regulation, and closed state stability.
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Affiliation(s)
- Wenting Guo
- Department of Physiology and Pharmacology, Libin Cardiovascular Institute, University of Calgary, Calgary, Alberta, Canada; Department of Biochemistry and Molecular Biology, Libin Cardiovascular Institute, University of Calgary, Calgary, Alberta, Canada
| | - Bo Sun
- Department of Physiology and Pharmacology, Libin Cardiovascular Institute, University of Calgary, Calgary, Alberta, Canada; Department of Biochemistry and Molecular Biology, Libin Cardiovascular Institute, University of Calgary, Calgary, Alberta, Canada; Medical School, Kunming University of Science and Technology, Kunming, China
| | - John Paul Estillore
- Department of Physiology and Pharmacology, Libin Cardiovascular Institute, University of Calgary, Calgary, Alberta, Canada; Department of Biochemistry and Molecular Biology, Libin Cardiovascular Institute, University of Calgary, Calgary, Alberta, Canada
| | - Ruiwu Wang
- Department of Physiology and Pharmacology, Libin Cardiovascular Institute, University of Calgary, Calgary, Alberta, Canada; Department of Biochemistry and Molecular Biology, Libin Cardiovascular Institute, University of Calgary, Calgary, Alberta, Canada
| | - S R Wayne Chen
- Department of Physiology and Pharmacology, Libin Cardiovascular Institute, University of Calgary, Calgary, Alberta, Canada; Department of Biochemistry and Molecular Biology, Libin Cardiovascular Institute, University of Calgary, Calgary, Alberta, Canada.
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Lieve KVV, Verhagen JMA, Wei J, Bos JM, van der Werf C, Rosés I Noguer F, Mancini GMS, Guo W, Wang R, van den Heuvel F, Frohn-Mulder IME, Shimizu W, Nogami A, Horigome H, Roberts JD, Leenhardt A, Crijns HJG, Blank AC, Aiba T, Wiesfeld ACP, Blom NA, Sumitomo N, Till J, Ackerman MJ, Chen SRW, van de Laar IMBH, Wilde AAM. Linking the heart and the brain: Neurodevelopmental disorders in patients with catecholaminergic polymorphic ventricular tachycardia. Heart Rhythm 2018; 16:220-228. [PMID: 30170228 DOI: 10.1016/j.hrthm.2018.08.025] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/17/2018] [Indexed: 11/25/2022]
Abstract
BACKGROUND Catecholaminergic polymorphic ventricular tachycardia (CPVT) is an uncommon inherited arrhythmia disorder characterized by adrenergically evoked ventricular arrhythmias. Mutations in the cardiac calcium release channel/ryanodine receptor gene (RYR2) are identified in the majority of patients with CPVT. RyR2 is also the major RyR isoform expressed in the brain. OBJECTIVE The purpose of this study was to estimate the prevalence of intellectual disability (ID) and other neurodevelopmental disorders (NDDs) in RYR2-associated CPVT (CPVT1) and to study the characteristics of these patients. METHODS We reviewed the medical records of all CPVT1 patients from 12 international centers and analyzed the characteristics of all CPVT1 patients with concomitant NDDs. We functionally characterized the mutations to assess their response to caffeine activation. We did not correct for potential confounders. RESULTS Among 421 CPVT1 patients, we identified 34 patients with ID (8%; 95% confidence interval 6%-11%). Median age at diagnosis was 9.3 years (interquartile range 7.0-14.5). Parents for 24 of 34 patients were available for genetic testing, and 13 of 24 (54%) had a de novo mutation. Severity of ID ranged from mild to severe and was accompanied by other NDDs in 9 patients (26%). Functionally, the ID-associated mutations showed a markedly enhanced response of RyR2 to activation by caffeine. Seventeen patients (50%) also had supraventricular arrhythmias. During median follow-up of 8.4 years (interquartile range 1.8-12.4), 15 patients (45%) experienced an arrhythmic event despite adequate therapy. CONCLUSION Our study indicates that ID is more prevalent among CPVT1 patients (8%) than in the general population (1%-3%). This subgroup of CPVT1 patients reveals a malignant cardiac phenotype with marked supraventricular and ventricular arrhythmias.
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Affiliation(s)
- Krystien V V Lieve
- AMC Heart Center, Department of Clinical and Experimental Cardiology, Academic Medical Center, Amsterdam, The Netherlands
| | - Judith M A Verhagen
- Department of Clinical Genetics, Erasmus MC, University Medical Center Rotterdam, Rotterdam, The Netherlands
| | - Jinhong Wei
- The Libin Cardiovascular Institute of Alberta, Department of Physiology and Pharmacology, University of Calgary, Calgary, Alberta, Canada
| | - J Martijn Bos
- Department of Cardiovascular Diseases, Division of Heart Rhythm Services, Mayo Clinic, Rochester, Minnesota, Department of Pediatric and Adolescent Medicine, Division of Pediatric Cardiology, Mayo Clinic, Rochester, Minnesota, and Department of Molecular Pharmacology & Experimental Therapeutics, Windland Smith Rice Sudden Death Genomics Laboratory, Mayo Clinic, Rochester, Minnesota
| | - Christian van der Werf
- AMC Heart Center, Department of Clinical and Experimental Cardiology, Academic Medical Center, Amsterdam, The Netherlands
| | | | - Grazia M S Mancini
- Department of Clinical Genetics, Erasmus MC, University Medical Center Rotterdam, Rotterdam, The Netherlands
| | - Wenting Guo
- The Libin Cardiovascular Institute of Alberta, Department of Physiology and Pharmacology, University of Calgary, Calgary, Alberta, Canada
| | - Ruiwu Wang
- The Libin Cardiovascular Institute of Alberta, Department of Physiology and Pharmacology, University of Calgary, Calgary, Alberta, Canada
| | - Freek van den Heuvel
- Department of Pediatric Cardiology, Beatrix Children's Hospital, University Medical Center Groningen, Groningen, The Netherlands
| | - Ingrid M E Frohn-Mulder
- Department of Pediatric Cardiology, Sophia Children's Hospital, Erasmus University Medical Center, Rotterdam, The Netherlands
| | - Wataru Shimizu
- Department of Cardiovascular Medicine, Nippon Medical School, Tokyo, Japan; Department of Cardiovascular Medicine, National Cerebral and Cardiovascular Center, Suita, Japan
| | - Akihiko Nogami
- Cardiovascular Division, Faculty of Medicine, University of Tsukuba, Tsukuba, Japan
| | - Hitoshi Horigome
- Cardiovascular Division, Faculty of Medicine, University of Tsukuba, Tsukuba, Japan
| | - Jason D Roberts
- Section of Cardiac Electrophysiology, Division of Cardiology, Department of Medicine, Western University, London, Ontario, Canada
| | - Antoine Leenhardt
- CNMR Maladies Cardiaques Héréditaires Rares, Hôpital Bichat, Université Paris Diderot, Sorbonne Paris Cité, Paris, France, and AP-HP, Service de Cardiologie, Hôpital Bichat, Paris, France
| | - Harry J G Crijns
- Department of Cardiology, CARIM School for Cardiovascular Diseases, Faculty of Health, Medicine, and Life Sciences, Maastricht University, Maastricht, The Netherlands
| | - Andreas C Blank
- Department of Pediatric Cardiology, Wilhelmina Children's Hospital, University Medical Center, Utrecht, The Netherlands
| | - Takeshi Aiba
- Department of Cardiovascular Medicine, National Cerebral and Cardiovascular Center, Suita, Japan
| | - Ans C P Wiesfeld
- Department of Cardiology, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands
| | - Nico A Blom
- AMC Heart Center, Department of Clinical and Experimental Cardiology, Academic Medical Center, Amsterdam, The Netherlands; Department of Pediatric Cardiology, Leiden University Medical Center, Leiden, The Netherlands
| | - Naokata Sumitomo
- Department of Pediatric Cardiology, Saitama Medical University International Medical Center, Saitama, Japan
| | - Jan Till
- Department of Cardiology, Royal Brompton Hospital, London, United Kingdom
| | - Michael J Ackerman
- Department of Cardiovascular Diseases, Division of Heart Rhythm Services, Mayo Clinic, Rochester, Minnesota, Department of Pediatric and Adolescent Medicine, Division of Pediatric Cardiology, Mayo Clinic, Rochester, Minnesota, and Department of Molecular Pharmacology & Experimental Therapeutics, Windland Smith Rice Sudden Death Genomics Laboratory, Mayo Clinic, Rochester, Minnesota
| | - S R Wayne Chen
- The Libin Cardiovascular Institute of Alberta, Department of Physiology and Pharmacology, University of Calgary, Calgary, Alberta, Canada
| | - Ingrid M B H van de Laar
- Department of Clinical Genetics, Erasmus MC, University Medical Center Rotterdam, Rotterdam, The Netherlands
| | - Arthur A M Wilde
- AMC Heart Center, Department of Clinical and Experimental Cardiology, Academic Medical Center, Amsterdam, The Netherlands; Princess Al-Jawhara Al-Brahim Centre of Excellence in Research of Hereditary Disorders, Jeddah, Kingdom of Saudi Arabia.
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Jaffe DB, Brenner R. A computational model for how the fast afterhyperpolarization paradoxically increases gain in regularly firing neurons. J Neurophysiol 2018; 119:1506-1520. [PMID: 29357445 DOI: 10.1152/jn.00385.2017] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The gain of a neuron, the number and frequency of action potentials triggered in response to a given amount of depolarizing injection, is an important behavior underlying a neuron's function. Variations in action potential waveform can influence neuronal discharges by the differential activation of voltage- and ion-gated channels long after the end of a spike. One component of the action potential waveform, the afterhyperpolarization (AHP), is generally considered an inhibitory mechanism for limiting firing rates. In dentate gyrus granule cells (DGCs) expressing fast-gated BK channels, large fast AHPs (fAHP) are paradoxically associated with increased gain. In this article, we describe a mechanism for this behavior using a computational model. Hyperpolarization provided by the fAHP enhances activation of a dendritic inward current (a T-type Ca2+ channel is suggested) that, in turn, boosts rebound depolarization at the soma. The model suggests that the fAHP may both reduce Ca2+ channel inactivation and, counterintuitively, enhance its activation. The magnitude of the rebound depolarization, in turn, determines the activation of a subsequent, slower inward current (a persistent Na+ current is suggested) limiting the interspike interval. Simulations also show that the effect of AHP on gain is also effective for physiologically relevant stimulation; varying AHP amplitude affects interspike interval across a range of "noisy" stimulus frequency and amplitudes. The mechanism proposed suggests that small fAHPs in DGCs may contribute to their limited excitability. NEW & NOTEWORTHY The afterhyperpolarization (AHP) is canonically viewed as a major factor underlying the refractory period, serving to limit neuronal firing rate. We recently reported that enhancing the amplitude of the fast AHP (fAHP) in a relatively slowly firing neuron (vs. fast spiking neurons) expressing fast-gated BK channels augments neuronal excitability. In this computational study, we present a novel, quantitative hypothesis for how varying the amplitude of the fAHP can, paradoxically, influence a subsequent spike tens of milliseconds later.
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Affiliation(s)
- David B Jaffe
- Department of Biology, UTSA Neurosciences Institute, University of Texas at San Antonio , San Antonio, Texas
| | - Robert Brenner
- Department of Cell and Integrative Physiology, University of Texas Health Science Center at San Antonio , San Antonio, Texas
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Wang B, Bugay V, Ling L, Chuang HH, Jaffe DB, Brenner R. Knockout of the BK β4-subunit promotes a functional coupling of BK channels and ryanodine receptors that mediate a fAHP-induced increase in excitability. J Neurophysiol 2016; 116:456-65. [PMID: 27146987 PMCID: PMC4978790 DOI: 10.1152/jn.00857.2015] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2015] [Accepted: 05/03/2016] [Indexed: 01/24/2023] Open
Abstract
BK channels are large-conductance calcium- and voltage-activated potassium channels with diverse properties. Knockout of the accessory BK β4-subunit in hippocampus dentate gyrus granule neurons causes BK channels to change properties from slow-gated type II channels to fast-gated type I channels that sharpen the action potential, increase the fast afterhyperpolarization (fAHP) amplitude, and increase spike frequency. Here we studied the calcium channels that contribute to fast-gated BK channel activation and increased excitability of β4 knockout neurons. By using pharmacological blockers during current-clamp recording, we find that BK channel activation during the fAHP is dependent on ryanodine receptor activation. In contrast, L-type calcium channel blocker (nifedipine) affects the BK channel-dependent repolarization phase of the action potential but has no effect on the fAHP. Reducing BK channel activation during the repolarization phase with nifedipine, or during the fAHP with ryanodine, indicated that it is the BK-mediated increase of the fAHP that confers proexcitatory effects. The proexcitatory role of the fAHP was corroborated using dynamic current clamp. Increase or decrease of the fAHP amplitude during spiking revealed an inverse relationship between fAHP amplitude and interspike interval. Finally, we show that the seizure-prone ryanodine receptor gain-of-function (R2474S) knockin mice have an unaltered repolarization phase but larger fAHP and increased AP frequency compared with their control littermates. In summary, these results indicate that an important role of the β4-subunit is to reduce ryanodine receptor-BK channel functional coupling during the fAHP component of the action potential, thereby decreasing excitability of dentate gyrus neurons.
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Affiliation(s)
- Bin Wang
- Department of Physiology, The University of Texas Health Science Center at San Antonio, San Antonio, Texas; and
| | - Vladislav Bugay
- Department of Physiology, The University of Texas Health Science Center at San Antonio, San Antonio, Texas; and
| | - Ling Ling
- Department of Physiology, The University of Texas Health Science Center at San Antonio, San Antonio, Texas; and
| | - Hui-Hsui Chuang
- Department of Physiology, The University of Texas Health Science Center at San Antonio, San Antonio, Texas; and
| | - David B Jaffe
- Department of Biology, University of Texas at San Antonio, San Antonio, Texas
| | - Robert Brenner
- Department of Physiology, The University of Texas Health Science Center at San Antonio, San Antonio, Texas; and
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Hamdan FF, Srour M, Capo-Chichi JM, Daoud H, Nassif C, Patry L, Massicotte C, Ambalavanan A, Spiegelman D, Diallo O, Henrion E, Dionne-Laporte A, Fougerat A, Pshezhetsky AV, Venkateswaran S, Rouleau GA, Michaud JL. De novo mutations in moderate or severe intellectual disability. PLoS Genet 2014; 10:e1004772. [PMID: 25356899 PMCID: PMC4214635 DOI: 10.1371/journal.pgen.1004772] [Citation(s) in RCA: 295] [Impact Index Per Article: 29.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2014] [Accepted: 09/22/2014] [Indexed: 01/09/2023] Open
Abstract
Genetics is believed to have an important role in intellectual disability (ID). Recent studies have emphasized the involvement of de novo mutations (DNMs) in ID but the extent to which they contribute to its pathogenesis and the identity of the corresponding genes remain largely unknown. Here, we report a screen for DNMs in subjects with moderate or severe ID. We sequenced the exomes of 41 probands and their parents, and confirmed 81 DNMs affecting the coding sequence or consensus splice sites (1.98 DNMs/proband). We observed a significant excess of de novo single nucleotide substitutions and loss-of-function mutations in these cases compared to control subjects, suggesting that at least a subset of these variations are pathogenic. A total of 12 likely pathogenic DNMs were identified in genes previously associated with ID (ARID1B, CHD2, FOXG1, GABRB3, GATAD2B, GRIN2B, MBD5, MED13L, SETBP1, TBR1, TCF4, WDR45), resulting in a diagnostic yield of ∼29%. We also identified 12 possibly pathogenic DNMs in genes (HNRNPU, WAC, RYR2, SET, EGR1, MYH10, EIF2C1, COL4A3BP, CHMP2A, PPP1CB, VPS4A, PPP2R2B) that have not previously been causally linked to ID. Interestingly, no case was explained by inherited mutations. Protein network analysis indicated that the products of many of these known and candidate genes interact with each other or with products of other ID-associated genes further supporting their involvement in ID. We conclude that DNMs represent a major cause of moderate or severe ID.
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Affiliation(s)
| | - Myriam Srour
- CHU Sainte-Justine Research Center, Montreal, Canada
- Division of Pediatric Neurology, Montreal Children's Hospital, Montreal, Canada
| | | | - Hussein Daoud
- Montreal Neurological Institute, McGill University, Montreal, Canada
| | | | - Lysanne Patry
- CHU Sainte-Justine Research Center, Montreal, Canada
| | | | | | - Dan Spiegelman
- Montreal Neurological Institute, McGill University, Montreal, Canada
| | - Ousmane Diallo
- Montreal Neurological Institute, McGill University, Montreal, Canada
| | - Edouard Henrion
- Montreal Neurological Institute, McGill University, Montreal, Canada
| | | | - Anne Fougerat
- CHU Sainte-Justine Research Center, Montreal, Canada
| | | | | | - Guy A. Rouleau
- Montreal Neurological Institute, McGill University, Montreal, Canada
| | - Jacques L. Michaud
- CHU Sainte-Justine Research Center, Montreal, Canada
- Department of Pediatrics and Department of Neurosciences, University of Montreal, Montreal, Canada
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