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Calcium Handling in Inherited Cardiac Diseases: A Focus on Catecholaminergic Polymorphic Ventricular Tachycardia and Hypertrophic Cardiomyopathy. Int J Mol Sci 2023; 24:ijms24043365. [PMID: 36834774 PMCID: PMC9963263 DOI: 10.3390/ijms24043365] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2023] [Revised: 02/02/2023] [Accepted: 02/04/2023] [Indexed: 02/10/2023] Open
Abstract
Calcium (Ca2+) is the major mediator of cardiac contractile function. It plays a key role in regulating excitation-contraction coupling and modulating the systolic and diastolic phases. Defective handling of intracellular Ca2+ can cause different types of cardiac dysfunction. Thus, the remodeling of Ca2+ handling has been proposed to be a part of the pathological mechanism leading to electrical and structural heart diseases. Indeed, to ensure appropriate electrical cardiac conduction and contraction, Ca2+ levels are regulated by several Ca2+-related proteins. This review focuses on the genetic etiology of cardiac diseases related to calcium mishandling. We will approach the subject by focalizing on two clinical entities: catecholaminergic polymorphic ventricular tachycardia (CPVT) as a cardiac channelopathy and hypertrophic cardiomyopathy (HCM) as a primary cardiomyopathy. Further, this review will illustrate the fact that despite the genetic and allelic heterogeneity of cardiac defects, calcium-handling perturbations are the common pathophysiological mechanism. The newly identified calcium-related genes and the genetic overlap between the associated heart diseases are also discussed in this review.
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2
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Rossi D, Pierantozzi E, Amadsun DO, Buonocore S, Rubino EM, Sorrentino V. The Sarcoplasmic Reticulum of Skeletal Muscle Cells: A Labyrinth of Membrane Contact Sites. Biomolecules 2022; 12:488. [PMID: 35454077 PMCID: PMC9026860 DOI: 10.3390/biom12040488] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2022] [Revised: 03/14/2022] [Accepted: 03/18/2022] [Indexed: 12/17/2022] Open
Abstract
The sarcoplasmic reticulum of skeletal muscle cells is a highly ordered structure consisting of an intricate network of tubules and cisternae specialized for regulating Ca2+ homeostasis in the context of muscle contraction. The sarcoplasmic reticulum contains several proteins, some of which support Ca2+ storage and release, while others regulate the formation and maintenance of this highly convoluted organelle and mediate the interaction with other components of the muscle fiber. In this review, some of the main issues concerning the biology of the sarcoplasmic reticulum will be described and discussed; particular attention will be addressed to the structure and function of the two domains of the sarcoplasmic reticulum supporting the excitation-contraction coupling and Ca2+-uptake mechanisms.
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Affiliation(s)
- Daniela Rossi
- Department of Molecular and Developmental Medicine, University of Siena, Via Aldo Moro 2, 53100 Siena, Italy; (E.P.); (D.O.A.); (S.B.); (E.M.R.); (V.S.)
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3
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Quantification of the calcium signaling deficit in muscles devoid of triadin. PLoS One 2022; 17:e0264146. [PMID: 35213584 PMCID: PMC8880904 DOI: 10.1371/journal.pone.0264146] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2021] [Accepted: 02/03/2022] [Indexed: 11/24/2022] Open
Abstract
Triadin, a protein of the sarcoplasmic reticulum (SR) of striated muscles, anchors the calcium-storing protein calsequestrin to calcium release RyR channels at the junction with t-tubules, and modulates these channels by conformational effects. Triadin ablation induces structural SR changes and alters the expression of other proteins. Here we quantify alterations of calcium signaling in single skeletal myofibers of constitutive triadin-null mice. We find higher resting cytosolic and lower SR-luminal [Ca2+], 40% lower calsequestrin expression, and more CaV1.1, RyR1 and SERCA1. Despite the increased CaV1.1, the mobile intramembrane charge was reduced by ~20% in Triadin-null fibers. The initial peak of calcium release flux by pulse depolarization was minimally altered in the null fibers (revealing an increase in peak calcium permeability). The “hump” phase that followed, attributable to calcium detaching from calsequestrin, was 25% lower, a smaller change than expected from the reduced calsequestrin content and calcium saturation. The exponential decay rate of calcium transients was 25% higher, consistent with the higher SERCA1 content. Recovery of calcium flux after a depleting depolarization was faster in triadin-null myofibers, consistent with the increased uptake rate and lower SR calsequestrin content. In sum, the triadin knockout determines an increased RyR1 channel openness, which depletes the SR, a substantial loss of calsequestrin and gains in other couplon proteins. Powerful functional compensations ensue: activation of SOCE that increases [Ca2+]cyto; increased SERCA1 activity, which limits the decrease in [Ca2+]SR and a restoration of SR calcium storage of unknown substrate. Together, they effectively limit the functional loss in skeletal muscles.
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4
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Generation of a Triadin KnockOut Syndrome Zebrafish Model. Int J Mol Sci 2021; 22:ijms22189720. [PMID: 34575879 PMCID: PMC8471218 DOI: 10.3390/ijms22189720] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2021] [Revised: 08/31/2021] [Accepted: 09/03/2021] [Indexed: 11/17/2022] Open
Abstract
Different forms of sudden cardiac death have been described, including a recently identified form of genetic arrhythmogenic disorder, named “Triadin KnockOut Syndrome” (TKOS). TKOS is associated with recessive mutations in the TRDN gene, encoding for TRIADIN, but the pathogenic mechanism underlying the malignant phenotype has yet to be completely defined. Moreover, patients with TKOS are often refractory to conventional treatment, substantiating the need to identify new therapeutic strategies in order to prevent or treat cardiac events. The zebrafish (Danio rerio) heart is highly comparable to the human heart in terms of functions, signal pathways and ion channels, representing a good model to study cardiac disorders. In this work, we generated the first zebrafish model for trdn loss-of-function, by means of trdn morpholino injections, and characterized its phenotype. Although we did not observe any gross cardiac morphological defect between trdn loss-of-function embryos and controls, we found altered cardiac rhythm that was recovered by the administration of arrhythmic drugs. Our model will provide a suitable platform to study the effect of TRDN mutations and to perform drug screening to identify new pharmacological strategies for patients carrying TRDN mutations.
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T-tubule remodeling in human hypertrophic cardiomyopathy. J Muscle Res Cell Motil 2020; 42:305-322. [PMID: 33222034 PMCID: PMC8332592 DOI: 10.1007/s10974-020-09591-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2020] [Accepted: 10/22/2020] [Indexed: 11/17/2022]
Abstract
The highly organized transverse T-tubule membrane system represents the ultrastructural substrate for excitation–contraction coupling in ventricular myocytes. While the architecture and function of T-tubules have been well described in animal models, there is limited morpho-functional data on T-tubules in human myocardium. Hypertrophic cardiomyopathy (HCM) is a primary disease of the heart muscle, characterized by different clinical presentations at the various stages of its progression. Most HCM patients, indeed, show a compensated hypertrophic disease (“non-failing hypertrophic phase”), with preserved left ventricular function, and only a small subset of individuals evolves into heart failure (“end stage HCM”). In terms of T-tubule remodeling, the “end-stage” disease does not differ from other forms of heart failure. In this review we aim to recapitulate the main structural features of T-tubules during the “non-failing hypertrophic stage” of human HCM by revisiting data obtained from human myectomy samples. Moreover, by comparing pathological changes observed in myectomy samples with those introduced by acute (experimentally induced) detubulation, we discuss the role of T-tubular disruption as a part of the complex excitation–contraction coupling remodeling process that occurs during disease progression. Lastly, we highlight how T-tubule morpho-functional changes may be related to patient genotype and we discuss the possibility of a primitive remodeling of the T-tubule system in rare HCM forms associated with genes coding for proteins implicated in T-tubule structural integrity, formation and maintenance.
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Protasi F, Pietrangelo L, Boncompagni S. Calcium entry units (CEUs): perspectives in skeletal muscle function and disease. J Muscle Res Cell Motil 2020; 42:233-249. [PMID: 32812118 PMCID: PMC8332569 DOI: 10.1007/s10974-020-09586-3] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2020] [Accepted: 08/03/2020] [Indexed: 12/28/2022]
Abstract
In the last decades the term Store-operated Ca2+ entry (SOCE) has been used in the scientific literature to describe an ubiquitous cellular mechanism that allows recovery of calcium (Ca2+) from the extracellular space. SOCE is triggered by a reduction of Ca2+ content (i.e. depletion) in intracellular stores, i.e. endoplasmic or sarcoplasmic reticulum (ER and SR). In skeletal muscle the mechanism is primarily mediated by a physical interaction between stromal interaction molecule-1 (STIM1), a Ca2+ sensor located in the SR membrane, and ORAI1, a Ca2+-permeable channel of external membranes, located in transverse tubules (TTs), the invaginations of the plasma membrane (PM) deputed to propagation of action potentials. It is generally accepted that in skeletal muscle SOCE is important to limit muscle fatigue during repetitive stimulation. We recently discovered that exercise promotes the assembly of new intracellular junctions that contains colocalized STIM1 and ORAI1, and that the presence of these new junctions increases Ca2+ entry via ORAI1, while improving fatigue resistance during repetitive stimulation. Based on these findings we named these new junctions Ca2+ Entry Units (CEUs). CEUs are dynamic organelles that assemble during muscle activity and disassemble during recovery thanks to the plasticity of the SR (containing STIM1) and the elongation/retraction of TTs (bearing ORAI1). Interestingly, similar structures described as SR stacks were previously reported in different mouse models carrying mutations in proteins involved in Ca2+ handling (calsequestrin-null mice; triadin and junctin null mice, etc.) or associated to microtubules (MAP6 knockout mice). Mutations in Stim1 and Orai1 (and calsequestrin-1) genes have been associated to tubular aggregate myopathy (TAM), a muscular disease characterized by: (a) muscle pain, cramping, or weakness that begins in childhood and worsens over time, and (b) the presence of large accumulations of ordered SR tubes (tubular aggregates, TAs) that do not contain myofibrils, mitochondria, nor TTs. Interestingly, TAs are also present in fast twitch muscle fibers of ageing mice. Several important issues remain un-answered: (a) the molecular mechanisms and signals that trigger the remodeling of membranes and the functional activation of SOCE during exercise are unclear; and (b) how dysfunctional SOCE and/or mutations in Stim1, Orai1 and calsequestrin (Casq1) genes lead to the formation of tubular aggregates (TAs) in aging and disease deserve investigation.
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Affiliation(s)
- Feliciano Protasi
- CAST, Center for Advanced Studies and Technology, University G. d'Annunzio of Chieti-Pescara, 66100, Chieti, Italy.
- DMSI, Department of Medicine and Aging Sciences, University G. d'Annunzio of Chieti-Pescara, 66100, Chieti, Italy.
| | - Laura Pietrangelo
- CAST, Center for Advanced Studies and Technology, University G. d'Annunzio of Chieti-Pescara, 66100, Chieti, Italy
- DMSI, Department of Medicine and Aging Sciences, University G. d'Annunzio of Chieti-Pescara, 66100, Chieti, Italy
| | - Simona Boncompagni
- CAST, Center for Advanced Studies and Technology, University G. d'Annunzio of Chieti-Pescara, 66100, Chieti, Italy
- DNICS, Department of Neuroscience, Imaging and Clinical Sciences, University G. d'Annunzio of Chieti-Pescara, 66100, Chieti, Italy
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Ali N, Rezvani HR, Motei D, Suleman S, Mahfouf W, Marty I, Ronkainen VP, Vainio SJ. Trisk 95 as a novel skin mirror for normal and diabetic systemic glucose level. Sci Rep 2020; 10:12246. [PMID: 32699238 PMCID: PMC7376074 DOI: 10.1038/s41598-020-68972-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2019] [Accepted: 07/03/2020] [Indexed: 11/21/2022] Open
Abstract
Developing trustworthy, cost effective, minimally or non-invasive glucose sensing strategies is of great need for diabetic patients. In this study, we used an experimental type I diabetic mouse model to examine whether the skin would provide novel means for identifying biomarkers associated with blood glucose level. We first showed that skin glucose levels are rapidly influenced by blood glucose concentrations. We then conducted a proteomic screen of murine skin using an experimental in vivo model of type I diabetes and wild-type controls. Among the proteins that increased expression in response to high blood glucose, Trisk 95 expression was significantly induced independently of insulin signalling. A luciferase reporter assay demonstrated that the induction of Trisk 95 expression occurs at a transcriptional level and is associated with a marked elevation in the Fluo-4AM signal, suggesting a role for intracellular calcium changes in the signalling cascade. Strikingly, these changes lead concurrently to fragmentation of the mitochondria. Moreover, Trisk 95 knockout abolishes both the calcium flux and the mitochondrial phenotype changes indicating dependency of glucose flux in the skin on Trisk 95 function. The data demonstrate that the skin reacts robustly to systemic blood changes, and that Trisk 95 is a promising biomarker for a glucose monitoring assembly.
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Affiliation(s)
- Nsrein Ali
- Laboratory of Developmental Biology, Faculty of Biochemistry and Molecular Medicine, Biocenter Oulu, University of Oulu, Aapistie 5A, 90220, Oulu, Finland. .,Infotech Oulu, University of Oulu, 90220, Oulu, Finland.
| | - Hamid Reza Rezvani
- Inserm, BMGIC, UMR 1035, University of Bordeaux, Bordeaux, France.,Centre de Référence pour les Maladies Rares de la Peau, CHU de Bordeaux, Bordeaux, France
| | - Diana Motei
- Laboratory of Developmental Biology, Faculty of Biochemistry and Molecular Medicine, Biocenter Oulu, University of Oulu, Aapistie 5A, 90220, Oulu, Finland
| | - Sufyan Suleman
- Laboratory of Developmental Biology, Faculty of Biochemistry and Molecular Medicine, Biocenter Oulu, University of Oulu, Aapistie 5A, 90220, Oulu, Finland
| | - Walid Mahfouf
- Inserm, BMGIC, UMR 1035, University of Bordeaux, Bordeaux, France
| | - Isabelle Marty
- Inserm U1216, Grenoble Institut des Neurosciences, University Grenoble, La Tronche, France
| | | | - Seppo J Vainio
- Laboratory of Developmental Biology, Faculty of Biochemistry and Molecular Medicine, Biocenter Oulu, University of Oulu, Aapistie 5A, 90220, Oulu, Finland.,Infotech Oulu, University of Oulu, 90220, Oulu, Finland.,Borealis Biobank of Northern Finland, Oulu University Hospital, Oulu, Finland
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8
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Sarquella-Brugada G, Fernandez-Falgueras A, Cesar S, Arbelo E, Jordà P, García-Álvarez A, Cruzalegui JC, Merchan EF, Fiol V, Brugada J, Brugada R, Campuzano O. Pediatric Malignant Arrhythmias Caused by Rare Homozygous Genetic Variants in TRDN: A Comprehensive Interpretation. Front Pediatr 2020; 8:601708. [PMID: 33692971 PMCID: PMC7938306 DOI: 10.3389/fped.2020.601708] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/01/2020] [Accepted: 10/14/2020] [Indexed: 12/19/2022] Open
Abstract
Aim: To perform a comprehensive phenotype-genotype correlation of all rare variants in Triadin leading to malignant arrhythmias in pediatrics. Methods: Triadin knockout syndrome is a rare entity reported in pediatric population. This syndrome is caused by rare variants in the TRDN gene. Malignant ventricular arrhythmias and sudden cardiac death can be a primary manifestation of disease. Although pharmacological measures are effective, some patients require an implantable defibrillator due to high risk of arrhythmogenic episodes. Main Results: Fourteen rare genetic alterations in TRDN have been reported to date. All of these potentially pathogenic alterations are located in a specific area of TRDN, highlighting this hot spot as an arrhythmogenic gene region. Conclusions: Early recognition and comprehensive interpretation of alterations in Triadin are crucial to adopt preventive measures and avoid malignant arrhythmogenic episodes in pediatric population.
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Affiliation(s)
- Georgia Sarquella-Brugada
- Arrhythmias Unit, Hospital Sant Joan de Déu, University of Barcelona, Barcelona, Spain.,Medical Science Department, School of Medicine, University of Girona, Girona, Spain
| | | | - Sergi Cesar
- Arrhythmias Unit, Hospital Sant Joan de Déu, University of Barcelona, Barcelona, Spain
| | - Elena Arbelo
- Arrhythmias Unit, Hospital Clinic, University of Barcelona-IDIBAPS, Barcelona, Spain.,Centro de Investigación Biomédica en Red. Enfermedades Cardiovasculares (CIBERCV), Madrid, Spain
| | - Paloma Jordà
- Arrhythmias Unit, Hospital Clinic, University of Barcelona-IDIBAPS, Barcelona, Spain.,Centro de Investigación Biomédica en Red. Enfermedades Cardiovasculares (CIBERCV), Madrid, Spain
| | - Ana García-Álvarez
- Arrhythmias Unit, Hospital Clinic, University of Barcelona-IDIBAPS, Barcelona, Spain.,Centro de Investigación Biomédica en Red. Enfermedades Cardiovasculares (CIBERCV), Madrid, Spain
| | | | | | - Victoria Fiol
- Arrhythmias Unit, Hospital Sant Joan de Déu, University of Barcelona, Barcelona, Spain
| | - Josep Brugada
- Arrhythmias Unit, Hospital Sant Joan de Déu, University of Barcelona, Barcelona, Spain.,Arrhythmias Unit, Hospital Clinic, University of Barcelona-IDIBAPS, Barcelona, Spain.,Centro de Investigación Biomédica en Red. Enfermedades Cardiovasculares (CIBERCV), Madrid, Spain
| | - Ramon Brugada
- Medical Science Department, School of Medicine, University of Girona, Girona, Spain.,Cardiovascular Genetics Center, University of Girona-IDIBGI, Girona, Spain.,Centro de Investigación Biomédica en Red. Enfermedades Cardiovasculares (CIBERCV), Madrid, Spain.,Cardiology Service, Hospital Josep Trueta, University of Girona, Girona, Spain
| | - Oscar Campuzano
- Medical Science Department, School of Medicine, University of Girona, Girona, Spain.,Cardiovascular Genetics Center, University of Girona-IDIBGI, Girona, Spain.,Centro de Investigación Biomédica en Red. Enfermedades Cardiovasculares (CIBERCV), Madrid, Spain
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Cacheux M, Fauconnier J, Thireau J, Osseni A, Brocard J, Roux-Buisson N, Brocard J, Fauré J, Lacampagne A, Marty I. Interplay between Triadin and Calsequestrin in the Pathogenesis of CPVT in the Mouse. Mol Ther 2019; 28:171-179. [PMID: 31607542 DOI: 10.1016/j.ymthe.2019.09.012] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2019] [Revised: 08/28/2019] [Accepted: 09/06/2019] [Indexed: 01/07/2023] Open
Abstract
Recessive forms of catecholaminergic polymorphic ventricular tachycardia (CPVT) are induced by mutations in genes encoding triadin or calsequestrin, two proteins that belong to the Ca2+ release complex, responsible for intracellular Ca2+ release triggering cardiac contractions. To better understand the mechanisms of triadin-induced CPVT and to assay multiple therapeutic interventions, we used a triadin knockout mouse model presenting a CPVT-like phenotype associated with a decrease in calsequestrin protein level. We assessed different approaches to rescue protein expression and to correct intracellular Ca2+ release and cardiac function: pharmacological treatment with kifunensine or a viral gene transfer-based approach, using adeno-associated virus serotype 2/9 (AAV2/9) encoding the triadin or calsequestrin. We observed that the levels of triadin and calsequestrin are intimately linked, and that reduction of both proteins contributes to the CPVT phenotype. Different combinations of triadin and calsequestrin expression level were obtained using these therapeutic approaches. A full expression of each is not necessary to correct the phenotype; a fine-tuning of the relative re-expression of both triadin and calsequestrin is required to correct the CPVT phenotype and rescue the cardiac function. AAV-mediated gene delivery of calsequestrin or triadin and treatment with kifunensine are potential treatments for recessive forms of CPVT due to triadin mutations.
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Affiliation(s)
- Marine Cacheux
- Grenoble Institut Neurosciences, INSERM, Grenoble Alpes University, U1216, CHU Grenoble Alpes, 38700 La Tronche, France
| | - Jérémy Fauconnier
- University of Montpellier, INSERM U1046, CNRS 9214, CHU Montpellier, 34295 Montpellier, France
| | - Jérôme Thireau
- University of Montpellier, INSERM U1046, CNRS 9214, CHU Montpellier, 34295 Montpellier, France
| | - Alexis Osseni
- Grenoble Institut Neurosciences, INSERM, Grenoble Alpes University, U1216, CHU Grenoble Alpes, 38700 La Tronche, France
| | - Jacques Brocard
- Grenoble Institut Neurosciences, INSERM, Grenoble Alpes University, U1216, CHU Grenoble Alpes, 38700 La Tronche, France
| | - Nathalie Roux-Buisson
- Grenoble Institut Neurosciences, INSERM, Grenoble Alpes University, U1216, CHU Grenoble Alpes, 38700 La Tronche, France
| | - Julie Brocard
- Grenoble Institut Neurosciences, INSERM, Grenoble Alpes University, U1216, CHU Grenoble Alpes, 38700 La Tronche, France
| | - Julien Fauré
- Grenoble Institut Neurosciences, INSERM, Grenoble Alpes University, U1216, CHU Grenoble Alpes, 38700 La Tronche, France
| | - Alain Lacampagne
- University of Montpellier, INSERM U1046, CNRS 9214, CHU Montpellier, 34295 Montpellier, France.
| | - Isabelle Marty
- Grenoble Institut Neurosciences, INSERM, Grenoble Alpes University, U1216, CHU Grenoble Alpes, 38700 La Tronche, France.
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10
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Schiaffino S. Knockout of human muscle genes revealed by large scale whole-exome studies. Mol Genet Metab 2018; 123:411-415. [PMID: 29452748 DOI: 10.1016/j.ymgme.2018.02.003] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/29/2017] [Revised: 02/06/2018] [Accepted: 02/06/2018] [Indexed: 12/22/2022]
Abstract
Large scale whole-exome sequence studies have revealed that a number of individuals from different populations have predicted loss-of-function of different genes due to nonsense, frameshift, or canonical splice-site mutations. Surprisingly, many of these mutations do not apparently show the deleterious phenotypic consequences expected from gene knockout. These homozygous null mutations, when confirmed, can provide insight into human gene function and suggest novel approaches to correct gene dysfunction, as the lack of the expected disease phenotype may reflect the existence of modifier genes that reveal potential therapeutic targets. Human knockouts complement the information derived from mouse knockouts, which are not always good models of human disease. We have examined human knockout datasets searching for genes expressed exclusively or predominantly in striated muscle. A number of well-known muscle genes was found in one or more datasets, including genes coding for sarcomeric myosins, components of the sarcomeric cytoskeleton, sarcoplasmic reticulum and plasma membrane, and enzymes involved in muscle metabolism. The surprising absence of phenotype in some of these human knockouts is critically discussed, focusing on the comparison with the corresponding mouse knockouts.
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Abstract
During the complex series of events leading to muscle contraction, the initial electric signal coming from motor neurons is transformed into an increase in calcium concentration that triggers sliding of myofibrils. This process, referred to as excitation-contraction coupling, is reliant upon the calcium-release complex, which is restricted spatially to a sub-compartment of muscle cells ("the triad") and regulated precisely. Any dysfunction in the calcium-release complex leads to muscle impairment and myopathy. Various causes can lead to alterations in excitation-contraction coupling and to muscle diseases. The latter are reviewed and classified into four categories: (i) mutation in a protein of the calcium-release complex; (ii) alteration in triad structure; (iii) modification of regulation of channels; (iv) modification in calcium stores within the muscle. Current knowledge of the pathophysiologic mechanisms in each category is described and discussed.
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Affiliation(s)
- Isabelle Marty
- University Grenoble Alpes, Grenoble Institut des Neurosciences, GIN, F-38000 Grenoble, France.,INSERM, U1216, F-38000 Grenoble, France
| | - Julien Fauré
- University Grenoble Alpes, Grenoble Institut des Neurosciences, GIN, F-38000 Grenoble, France.,INSERM, U1216, F-38000 Grenoble, France.,CHU de Grenoble, F-38000 Grenoble, France
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12
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Zhang L, Salgado-Somoza A, Vausort M, Leszek P, Devaux Y. A heart-enriched antisense long non-coding RNA regulates the balance between cardiac and skeletal muscle triadin. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2017; 1865:247-258. [PMID: 29126880 DOI: 10.1016/j.bbamcr.2017.11.002] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/03/2017] [Revised: 11/02/2017] [Accepted: 11/03/2017] [Indexed: 12/20/2022]
Abstract
Non-coding RNAs play major roles in cardiac pathophysiology. Recent studies reported that long non-coding RNAs (lncRNAs) are dysregulated in the failing heart, but how they contribute to heart failure development is unclear. In this study, we aimed to identify heart-enriched lncRNAs and investigate their regulation and function in the failing heart. RESULTS Analysis of a RNA-seq dataset of 15 Caucasian tissues allowed the identification of 415 heart-enriched lncRNAs. Fifty-three lncRNAs were located on the genome in close vicinity to protein-coding genes associated with cardiac function and disease. Analysis of a second RNA-seq dataset of 16 failing human hearts highlighted one lncRNA which we arbitrarily named TRDN-AS due to its localisation in the antisense position of the gene encoding triadin (TRDN). Expression of TRDN-AS and cardiac TRDN was up-regulated in biopsies from failing human hearts compared to control hearts. In failing hearts, TRDN-AS was positively correlated with a cardiac isoform of TRDN and negatively correlated with a skeletal muscle isoform of TRDN. A murine homolog of human TRDN-AS was identified and found to be enriched in the heart and localised in the nuclear compartment of cardiomyocytes. Trdn-AS expression as well as the ratio between cardiac and skeletal muscle isoforms were down-regulated after experimental myocardial infarction. In murine cardiomyocytes, activation of Trdn-AS transcription with the CRISPR/dCas9-VPR system enhanced the ratio between cardiac and skeletal isoforms of Trdn. CONCLUSION The lncRNA TRDN-AS regulates the balance between cardiac and skeletal isoforms of triadin. This finding may have implications for the treatment of heart failure.
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Affiliation(s)
- Lu Zhang
- Cardiovascular Research Unit, Luxembourg Health Institute, Luxembourg
| | | | - Melanie Vausort
- Cardiovascular Research Unit, Luxembourg Health Institute, Luxembourg
| | - Przemyslaw Leszek
- Heart Failure and Transplantology Department, Institute of Cardiology, Warsaw, Poland
| | - Yvan Devaux
- Cardiovascular Research Unit, Luxembourg Health Institute, Luxembourg.
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13
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Hancox JC, James AF, Walsh MA, Stuart AG. Triadin mutations - a cause of ventricular arrhythmias in children and young adults. JOURNAL OF CONGENITAL CARDIOLOGY 2017. [DOI: 10.1186/s40949-017-0011-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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14
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Dulhunty AF, Wei-LaPierre L, Casarotto MG, Beard NA. Core skeletal muscle ryanodine receptor calcium release complex. Clin Exp Pharmacol Physiol 2017; 44:3-12. [PMID: 27696487 DOI: 10.1111/1440-1681.12676] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2016] [Revised: 09/27/2016] [Accepted: 09/27/2016] [Indexed: 12/15/2022]
Abstract
The core skeletal muscle ryanodine receptor (RyR1) calcium release complex extends through three compartments of the muscle fibre, linking the extracellular environment through the cytoplasmic junctional gap to the lumen of the internal sarcoplasmic reticulum (SR) calcium store. The protein complex is essential for skeletal excitation-contraction (EC)-coupling and skeletal muscle function. Its importance is highlighted by perinatal death if any one of the EC-coupling components are missing and by myopathies associated with mutation of any of the proteins. The proteins essential for EC-coupling include the DHPR α1S subunit in the transverse tubule membrane, the DHPR β1a subunit in the cytosol and the RyR1 ion channel in the SR membrane. The other core proteins are triadin and junctin and calsequestrin, associated mainly with SR. These SR proteins are not essential for survival but exert structural and functional influences that modify the gain of EC-coupling and maintain normal muscle function. This review summarises our current knowledge of the individual protein/protein interactions within the core complex and their overall contribution to EC-coupling. We highlight significant areas that provide a continuing challenge for the field. Additional important components of the Ca2+ release complex, such as FKBP12, calmodulin, S100A1 and Stac3 are identified and reviewed elsewhere.
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Affiliation(s)
- Angela F Dulhunty
- John Curtin School of Medical Research, Australian National University, Canberra, ACT, Australia
| | - Lan Wei-LaPierre
- Department of Physiology and Pharmacology, University of Rochester Medical Center, Rochester, NY, USA
| | - Marco G Casarotto
- John Curtin School of Medical Research, Australian National University, Canberra, ACT, Australia
| | - Nicole A Beard
- Health Research Institute, University of Canberra, Canberra, ACT, Australia
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15
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Witherspoon JW, Meilleur KG. Review of RyR1 pathway and associated pathomechanisms. Acta Neuropathol Commun 2016; 4:121. [PMID: 27855725 PMCID: PMC5114830 DOI: 10.1186/s40478-016-0392-6] [Citation(s) in RCA: 50] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2016] [Accepted: 11/02/2016] [Indexed: 02/04/2023] Open
Abstract
Ryanodine receptor isoform-1 (RyR1) is a major calcium channel in skeletal muscle important for excitation-contraction coupling. Mutations in the RYR1 gene yield RyR1 protein dysfunction that manifests clinically as RYR1-related congenital myopathies (RYR1-RM) and/or malignant hyperthermia susceptibility (MHS). Individuals with RYR1-RM and/or MHS exhibit varying symptoms and severity. The symptoms impair quality of life and put patients at risk for early mortality, yet the cause of varying severity is not well understood. Currently, there is no Food and Drug Administration (FDA) approved treatment for RYR1-RM. Discovery of effective treatments is therefore critical, requiring knowledge of the RyR1 pathway. The purpose of this review is to compile work published to date on the RyR1 pathway and to implicate potential regions as targets for treatment. The RyR1 pathway is comprised of protein-protein interactions, protein-ligand interactions, and post-translational modifications, creating an activation/regulatory macromolecular complex. Given the complexity of this pathway, we divided these interactions and modifications into six regulatory groups. Three of several RyR1 interacting proteins, FK506-binding protein 12 (FKBP12), triadin, and calmodulin, were identified as playing important roles across all groups and may serve as promising target sites for treatment. Also, variability in disease severity may be influenced by prolongation or hyperactivity of post-translational modifications resulting from RyR1 dysfunction.
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16
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Osseni A, Sébastien M, Sarrault O, Baudet M, Couté Y, Fauré J, Fourest-Lieuvin A, Marty I. Triadin and CLIMP-63 form a link between triads and microtubules in muscle cells. J Cell Sci 2016; 129:3744-3755. [PMID: 27562070 DOI: 10.1242/jcs.188862] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2016] [Accepted: 08/18/2016] [Indexed: 01/20/2023] Open
Abstract
In skeletal muscle, the triad is a structure comprising a transverse (T)-tubule and sarcoplasmic reticulum (SR) cisternae. Triads constitute the basis of excitation-contraction coupling as the cradle of the Ca2+ release complex. We have shown previously that triadin, a member of this complex, has shaping properties on reticulum membrane and is indirectly involved in a link between triads and microtubules. We have identified here that CLIMP-63 (also known as CKAP4), as the partner of triadin, is responsible for this association of triads and microtubules. Triadin and CLIMP-63 interact through their respective luminal domains and the shaping properties of triadin depend on the capacity of CLIMP-63 to bind microtubules with its cytosolic portion. In skeletal muscle, CLIMP-63 is localized in the SR, including triads, and is associated with the Ca2+ release complex through its interaction with triadin. Knockout of triadin in muscles results in the delocalization of CLIMP-63 from triads, its dissociation from the Ca2+ release complex and a disorganization of the microtubule network. Our results suggest that the association of triadin and CLIMP-63 could be involved in the shaping of SR terminal cisternae and in the guidance of microtubules close to the triads.
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Affiliation(s)
- Alexis Osseni
- University Grenoble Alpes, Grenoble Institut des Neurosciences, GIN, Grenoble F-38000, France INSERM, U1216, Grenoble F-38000, France
| | - Muriel Sébastien
- University Grenoble Alpes, Grenoble Institut des Neurosciences, GIN, Grenoble F-38000, France INSERM, U1216, Grenoble F-38000, France
| | - Oriana Sarrault
- University Grenoble Alpes, Grenoble Institut des Neurosciences, GIN, Grenoble F-38000, France INSERM, U1216, Grenoble F-38000, France
| | - Mathieu Baudet
- University Grenoble Alpes, BIG-BGE, Grenoble F-38000, France CEA, BIG, BGE and GPC, Grenoble F-38000, France INSERM, BGE, Grenoble F-38000, France
| | - Yohann Couté
- University Grenoble Alpes, BIG-BGE, Grenoble F-38000, France CEA, BIG, BGE and GPC, Grenoble F-38000, France INSERM, BGE, Grenoble F-38000, France
| | - Julien Fauré
- University Grenoble Alpes, Grenoble Institut des Neurosciences, GIN, Grenoble F-38000, France INSERM, U1216, Grenoble F-38000, France CHU de Grenoble, Grenoble F-38000, France
| | - Anne Fourest-Lieuvin
- University Grenoble Alpes, Grenoble Institut des Neurosciences, GIN, Grenoble F-38000, France INSERM, U1216, Grenoble F-38000, France CEA, BIG, BGE and GPC, Grenoble F-38000, France
| | - Isabelle Marty
- University Grenoble Alpes, Grenoble Institut des Neurosciences, GIN, Grenoble F-38000, France INSERM, U1216, Grenoble F-38000, France
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17
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Ríos E, Figueroa L, Manno C, Kraeva N, Riazi S. The couplonopathies: A comparative approach to a class of diseases of skeletal and cardiac muscle. ACTA ACUST UNITED AC 2016; 145:459-74. [PMID: 26009541 PMCID: PMC4442791 DOI: 10.1085/jgp.201411321] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
A novel category of diseases of striated muscle is proposed, the couplonopathies, as those that affect components of the couplon and thereby alter its operation. Couplons are the functional units of intracellular calcium release in excitation–contraction coupling. They comprise dihydropyridine receptors, ryanodine receptors (Ca2+ release channels), and a growing list of ancillary proteins whose alteration may lead to disease. Within a generally similar plan, the couplons of skeletal and cardiac muscle show, in a few places, marked structural divergence associated with critical differences in the mechanisms whereby they fulfill their signaling role. Most important among these are the presence of a mechanical or allosteric communication between voltage sensors and Ca2+ release channels, exclusive to the skeletal couplon, and the smaller capacity of the Ca stores in cardiac muscle, which results in greater swings of store concentration during physiological function. Consideration of these structural and functional differences affords insights into the pathogenesis of several couplonopathies. The exclusive mechanical connection of the skeletal couplon explains differences in pathogenesis between malignant hyperthermia (MH) and catecholaminergic polymorphic ventricular tachycardia (CPVT), conditions most commonly caused by mutations in homologous regions of the skeletal and cardiac Ca2+ release channels. Based on mechanistic considerations applicable to both couplons, we identify the plasmalemma as a site of secondary modifications, typically an increase in store-operated calcium entry, that are relevant in MH pathogenesis. Similar considerations help explain the different consequences that mutations in triadin and calsequestrin have in these two tissues. As more information is gathered on the composition of cardiac and skeletal couplons, this comparative and mechanistic approach to couplonopathies should be useful to understand pathogenesis, clarify diagnosis, and propose tissue-specific drug development.
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Affiliation(s)
- Eduardo Ríos
- Section of Cellular Signaling, Department of Molecular Biophysics and Physiology, Rush University, Chicago, IL 60612
| | - Lourdes Figueroa
- Section of Cellular Signaling, Department of Molecular Biophysics and Physiology, Rush University, Chicago, IL 60612
| | - Carlo Manno
- Section of Cellular Signaling, Department of Molecular Biophysics and Physiology, Rush University, Chicago, IL 60612
| | - Natalia Kraeva
- Malignant Hyperthermia Investigation Unit, University Health Network, Toronto General Hospital, Toronto, Ontario M5G 2C4, Canada
| | - Sheila Riazi
- Malignant Hyperthermia Investigation Unit, University Health Network, Toronto General Hospital, Toronto, Ontario M5G 2C4, Canada
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18
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Ladd AN. New Insights Into the Role of RNA-Binding Proteins in the Regulation of Heart Development. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2016; 324:125-85. [PMID: 27017008 DOI: 10.1016/bs.ircmb.2015.12.009] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The regulation of gene expression during development takes place both at the transcriptional and posttranscriptional levels. RNA-binding proteins (RBPs) regulate pre-mRNA processing, mRNA localization, stability, and translation. Many RBPs are expressed in the heart and have been implicated in heart development, function, or disease. This chapter will review the current knowledge about RBPs in the developing heart, focusing on those that regulate posttranscriptional gene expression. The involvement of RBPs at each stage of heart development will be considered in turn, including the establishment of specific cardiac cell types and formation of the primitive heart tube, cardiac morphogenesis, and postnatal maturation and aging. The contributions of RBPs to cardiac birth defects and heart disease will also be considered in these contexts. Finally, the interplay between RBPs and other regulatory factors in the developing heart, such as transcription factors and miRNAs, will be discussed.
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Affiliation(s)
- A N Ladd
- Department of Cellular and Molecular Medicine, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, United States of America.
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19
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Cacheux M, Blum A, Sébastien M, Wozny AS, Brocard J, Mamchaoui K, Mouly V, Roux-Buisson N, Rendu J, Monnier N, Krivosic R, Allen P, Lacour A, Lunardi J, Fauré J, Marty I. Functional Characterization of a Central Core Disease RyR1 Mutation (p.Y4864H) Associated with Quantitative Defect in RyR1 Protein. J Neuromuscul Dis 2015; 2:421-432. [PMID: 27858745 PMCID: PMC5240544 DOI: 10.3233/jnd-150073] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Background: Central Core Disease (CCD) is a congenital myopathy often resulting from a mutation in RYR1 gene. Mutations in RyR1 can increase or decrease channel activity, or induce a reduction in the amount of protein. The consequences of a single mutation are sometimes multiple and the analysis of the functional effects is complex. Objective: The consequences of the p.Y4864H mutation identified in a CCD patient have been studied regarding both RyR1 function and amount. Methods: The amount of RyR1 in human and mouse muscles was evaluated using qRT-PCR and quantitative Western blot, and calcium release was studied using calcium imaging on primary cultures. The results were compared between human and mouse. Results: The p.Y4864H mutation induced an alteration of calcium release, and in addition was associated to a reduction in the amount of RyR1 in the patient’s muscle. This suggests two possible pathophysiological mechanisms: the alteration of calcium release could result from a modification of the channel properties of RyR1 or from a RyR1 reduction. In order to discriminate between the two hypotheses, we used the heterozygous RyR1 knockout (RyR1+/–) mouse model showing a comparable RyR1 protein reduction. No reduction in calcium release was observed in primary muscle culture from these mice, and no muscle weakness was measured. Conclusions: Because the reduction in the amount of RyR1 protein has no functional consequences in the murine model, the muscle weakness observed in the patient is most likely the result of a modification of the calcium channel function of RyR1 due to the p.Y4864H mutation.
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Affiliation(s)
- Marine Cacheux
- INSERM U836, Grenoble Institut des Neurosciences, Equipe Muscle et Pathologies, Grenoble, France.,Université Joseph Fourier, Grenoble, France
| | - Ariane Blum
- INSERM U836, Grenoble Institut des Neurosciences, Equipe Muscle et Pathologies, Grenoble, France.,Université Joseph Fourier, Grenoble, France
| | - Muriel Sébastien
- INSERM U836, Grenoble Institut des Neurosciences, Equipe Muscle et Pathologies, Grenoble, France.,Université Joseph Fourier, Grenoble, France
| | - Anne Sophie Wozny
- INSERM U836, Grenoble Institut des Neurosciences, Equipe Muscle et Pathologies, Grenoble, France.,Université Joseph Fourier, Grenoble, France.,Centre Hospitalier Régional Universitaire de Grenoble, Hôpital Michallon, Biochimie Génétique et Moléculaire, Grenoble, France
| | - Julie Brocard
- INSERM U836, Grenoble Institut des Neurosciences, Equipe Muscle et Pathologies, Grenoble, France.,Université Joseph Fourier, Grenoble, France
| | - Kamel Mamchaoui
- UMRS974 Inserm, UMR7215 CNRS, Institut de Myologie, GH PitiéSalpétrière, 47 bd de l'hôpital, Paris, France
| | - Vincent Mouly
- UMRS974 Inserm, UMR7215 CNRS, Institut de Myologie, GH PitiéSalpétrière, 47 bd de l'hôpital, Paris, France
| | - Nathalie Roux-Buisson
- INSERM U836, Grenoble Institut des Neurosciences, Equipe Muscle et Pathologies, Grenoble, France.,Université Joseph Fourier, Grenoble, France.,Centre Hospitalier Régional Universitaire de Grenoble, Hôpital Michallon, Biochimie Génétique et Moléculaire, Grenoble, France
| | - John Rendu
- INSERM U836, Grenoble Institut des Neurosciences, Equipe Muscle et Pathologies, Grenoble, France.,Université Joseph Fourier, Grenoble, France.,Centre Hospitalier Régional Universitaire de Grenoble, Hôpital Michallon, Biochimie Génétique et Moléculaire, Grenoble, France
| | - Nicole Monnier
- INSERM U836, Grenoble Institut des Neurosciences, Equipe Muscle et Pathologies, Grenoble, France.,Université Joseph Fourier, Grenoble, France.,Centre Hospitalier Régional Universitaire de Grenoble, Hôpital Michallon, Biochimie Génétique et Moléculaire, Grenoble, France
| | - Renée Krivosic
- Département Anesthésie-Réanimation, Hôpital Roger Salengro, CHRU de Lille, Lille, France
| | - Paul Allen
- Department of Molecular Biosciences, School of Veterinary Medicine, University of California at Davis, Davis CA, USA
| | - Arnaud Lacour
- Service de Neurologie, Hôpital Roger Salengro, CHRU de Lille, Lille, France
| | - Joël Lunardi
- INSERM U836, Grenoble Institut des Neurosciences, Equipe Muscle et Pathologies, Grenoble, France.,Université Joseph Fourier, Grenoble, France.,Centre Hospitalier Régional Universitaire de Grenoble, Hôpital Michallon, Biochimie Génétique et Moléculaire, Grenoble, France
| | - Julien Fauré
- INSERM U836, Grenoble Institut des Neurosciences, Equipe Muscle et Pathologies, Grenoble, France.,Université Joseph Fourier, Grenoble, France.,Centre Hospitalier Régional Universitaire de Grenoble, Hôpital Michallon, Biochimie Génétique et Moléculaire, Grenoble, France
| | - Isabelle Marty
- INSERM U836, Grenoble Institut des Neurosciences, Equipe Muscle et Pathologies, Grenoble, France.,Université Joseph Fourier, Grenoble, France
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20
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Desmond PF, Muriel J, Markwardt ML, Rizzo MA, Bloch RJ. Identification of Small Ankyrin 1 as a Novel Sarco(endo)plasmic Reticulum Ca2+-ATPase 1 (SERCA1) Regulatory Protein in Skeletal Muscle. J Biol Chem 2015; 290:27854-67. [PMID: 26405035 DOI: 10.1074/jbc.m115.676585] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2015] [Indexed: 01/06/2023] Open
Abstract
Small ankyrin 1 (sAnk1) is a 17-kDa transmembrane (TM) protein that binds to the cytoskeletal protein, obscurin, and stabilizes the network sarcoplasmic reticulum in skeletal muscle. We report that sAnk1 shares homology in its TM amino acid sequence with sarcolipin, a small protein inhibitor of the sarco(endo)plasmic reticulum Ca(2+)-ATPase (SERCA). Here we investigate whether sAnk1 and SERCA1 interact. Our results indicate that sAnk1 interacts specifically with SERCA1 in sarcoplasmic reticulum vesicles isolated from rabbit skeletal muscle, and in COS7 cells transfected to express these proteins. This interaction was demonstrated by co-immunoprecipitation and an anisotropy-based FRET method. Binding was reduced ~2-fold by the replacement of all of the TM amino acids of sAnk1 with leucines by mutagenesis. This suggests that, like sarcolipin, sAnk1 interacts with SERCA1 at least in part via its TM domain. Binding of the cytoplasmic domain of sAnk1 to SERCA1 was also detected in vitro. ATPase activity assays show that co-expression of sAnk1 with SERCA1 leads to a reduction of the apparent Ca(2+) affinity of SERCA1 but that the effect of sAnk1 is less than that of sarcolipin. The sAnk1 TM mutant has no effect on SERCA1 activity. Our results suggest that sAnk1 interacts with SERCA1 through its TM and cytoplasmic domains to regulate SERCA1 activity and modulate sequestration of Ca(2+) in the sarcoplasmic reticulum lumen. The identification of sAnk1 as a novel regulator of SERCA1 has significant implications for muscle physiology and the development of therapeutic approaches to treat heart failure and muscular dystrophies linked to Ca(2+) misregulation.
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Affiliation(s)
- Patrick F Desmond
- From the Department of Physiology and Program in Biochemistry and Molecular Biology, University of Maryland, Baltimore, Maryland 21230
| | | | | | | | - Robert J Bloch
- From the Department of Physiology and Program in Biochemistry and Molecular Biology, University of Maryland, Baltimore, Maryland 21230
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21
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Organization of junctional sarcoplasmic reticulum proteins in skeletal muscle fibers. J Muscle Res Cell Motil 2015; 36:501-15. [DOI: 10.1007/s10974-015-9421-5] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2015] [Accepted: 09/08/2015] [Indexed: 01/24/2023]
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22
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Di Blasi C, Sansanelli S, Ruggieri A, Moriggi M, Vasso M, D'Adamo AP, Blasevich F, Zanotti S, Paolini C, Protasi F, Tezzon F, Gelfi C, Morandi L, Pessia M, Mora M. A CASQ1 founder mutation in three Italian families with protein aggregate myopathy and hyperCKaemia. J Med Genet 2015; 52:617-26. [PMID: 26136523 DOI: 10.1136/jmedgenet-2014-102882] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2014] [Accepted: 06/16/2015] [Indexed: 12/24/2022]
Abstract
BACKGROUND Protein aggregate myopathies are increasingly recognised conditions characterised by a surplus of endogenous proteins. The molecular and mutational background for many protein aggregate myopathies has been clarified with the discovery of several underlying mutations. Familial idiopathic hyperCKaemia is a benign genetically heterogeneous condition with autosomal dominant features in a high proportion of cases. METHODS In 10 patients from three Italian families with autosomal dominant benign vacuolar myopathy and hyperCKaemia, we performed linkage analysis and exome sequencing as well as morphological and biochemical investigations. RESULTS AND CONCLUSIONS We show, by Sanger and exome sequencing, that the protein aggregate myopathy with benign evolution and muscle inclusions composed of excess CASQ1, affecting three Italian families, is due to the D244G heterozygous missense mutation in the CASQ1 gene. Investigation of microsatellite markers revealed a common haplotype in the three families indicating consanguinity and a founder effect. Results from immunocytochemistry, electron microscopy, biochemistry and transfected cell line investigations contribute to our understanding of pathogenetic mechanisms underlining this defect. The mutation is common to other Italian patients and is likely to share a founder effect with them. HyperCKaemia in the CASQ1-related myopathy is common and sometimes the sole overt manifestation. It is likely that CASQ1 mutations may remain undiagnosed if a muscle biopsy is not performed, and the condition could be more common than supposed.
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Affiliation(s)
- Claudia Di Blasi
- Neuromuscular Diseases and Neuroimmunology Unit, Foundation IRCCS Neurological Institute C. Besta, Milano, Italy
| | - Serena Sansanelli
- Neuromuscular Diseases and Neuroimmunology Unit, Foundation IRCCS Neurological Institute C. Besta, Milano, Italy
| | - Alessandra Ruggieri
- Neuromuscular Diseases and Neuroimmunology Unit, Foundation IRCCS Neurological Institute C. Besta, Milano, Italy
| | - Manuela Moriggi
- Department of Biomedical Sciences for Health, University of Milano, Milano, Italy
| | - Michele Vasso
- Department of Biomedical Sciences for Health, University of Milano, Milano, Italy CNR-Institute of Bioimaging and Molecular Physiology, Milano, Italy
| | | | - Flavia Blasevich
- Neuromuscular Diseases and Neuroimmunology Unit, Foundation IRCCS Neurological Institute C. Besta, Milano, Italy
| | - Simona Zanotti
- Neuromuscular Diseases and Neuroimmunology Unit, Foundation IRCCS Neurological Institute C. Besta, Milano, Italy
| | - Cecilia Paolini
- CeSI, Center for Research on Ageing & Department of Neuroscience, Imaging, and Clinical Sciences, University G D'Annunzio of Chieti, Chieti, Italy
| | - Feliciano Protasi
- CeSI, Center for Research on Ageing & Department of Neuroscience, Imaging, and Clinical Sciences, University G D'Annunzio of Chieti, Chieti, Italy
| | - Frediano Tezzon
- Neurology Unit, F Tappeiner Hospital of Merano, Merano, Italy
| | - Cecilia Gelfi
- Department of Biomedical Sciences for Health, University of Milano, Milano, Italy CNR-Institute of Bioimaging and Molecular Physiology, Milano, Italy
| | - Lucia Morandi
- Neuromuscular Diseases and Neuroimmunology Unit, Foundation IRCCS Neurological Institute C. Besta, Milano, Italy
| | - Mauro Pessia
- Faculty of Medicine, Section of Physiology and Biochemistry, Department of Experimental Medicine, University of Perugia, Perugia, Italy
| | - Marina Mora
- Neuromuscular Diseases and Neuroimmunology Unit, Foundation IRCCS Neurological Institute C. Besta, Milano, Italy
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Takeshima H, Hoshijima M, Song LS. Ca²⁺ microdomains organized by junctophilins. Cell Calcium 2015; 58:349-56. [PMID: 25659516 PMCID: PMC5159448 DOI: 10.1016/j.ceca.2015.01.007] [Citation(s) in RCA: 67] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2014] [Revised: 01/15/2015] [Accepted: 01/16/2015] [Indexed: 11/21/2022]
Abstract
Excitable cells typically possess junctional membrane complexes (JMCs) constructed by the plasma membrane and the endo/sarcoplasmic reticulum (ER/SR) for channel crosstalk. These JMCs are termed triads in skeletal muscle, dyads in cardiac muscle, peripheral couplings in smooth and developing striated muscles, and subsurface cisterns in neurons. Junctophilin subtypes contribute to the formation and maintenance of JMCs by serving as a physical bridge between the plasma membrane and ER/SR membrane in different cell types. In muscle cells, junctophilin deficiency prevents JMC formation and functional crosstalk between cell-surface Ca2+ channels and ER/SR Ca2+ release channels. Human genetic mutations in junctophilin subtypes are linked to congenital hypertrophic cardiomyopathy and neurodegenerative diseases. Furthermore, growing evidence suggests that dysregulation of junctophilins induces pathological alterations in skeletal and cardiac muscle.
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Affiliation(s)
- Hiroshi Takeshima
- Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto 606-8501, Japan.
| | - Masahiko Hoshijima
- Department of Medicine and Center for Research in Biological Systems, University of California, San Diego, CA 92093, USA.
| | - Long-Sheng Song
- Department of Internal Medicine, University of Iowa Carver College of Medicine, Iowa City, IA 52242, USA.
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The disorders of the calcium release unit of skeletal muscles: what have we learned from mouse models? J Muscle Res Cell Motil 2014; 36:61-9. [PMID: 25424378 DOI: 10.1007/s10974-014-9396-7] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2014] [Accepted: 10/29/2014] [Indexed: 01/01/2023]
Abstract
Calcium storage, release, and reuptake are essential for normal physiological function of muscle. Several human skeletal muscle disorders can arise from dysfunction in the control and coordination of these three critical processes. The release from the Sarcoplasmic Reticulum stores (SR) is handled by a multiprotein complex called Calcium Release Unit and composed of DiHydroPyridine Receptor or DHPR, Ryanodine Receptor or RYR, Calsequestrin or CASQ, junctin, Triadin, Junctophilin and Mitsugumin 29. Malignant hyperthermia (MH), Central Core Disease (CCD), Exertional/environmental Heat Stroke (EHS) and Multiminicore disease (MmD) are inherited disorders of calcium homeostasis in skeletal muscles directly related to mutations of genes coding for proteins of the CRU, primarily ryanodine receptor (RYR1). To understand the pathophysiology of MH and CCD, four murine lines carrying point mutations of human RYR1 have been developed: Y524S, R163C, I4898T and T4826I. Mice carrying those mutations show a phenotype with the traits of MH and/or CCD. Interestingly, also ablation of skeletal muscle calsequestrin (CASQ1) leads to a phenotype with MH-like lethal episodes in response to halothane and heat stress and development of central cores. In this review, we aim to describe the murine lines with RYR mutations or CASQ ablation, which show a phenotype similar to human MH or CCD, to underline their specific phenotypes and their differences and to discuss their contribution to the understanding of the pathophysiology of the disorders and the development of therapeutic strategies.
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25
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Marty I. Triadin regulation of the ryanodine receptor complex. J Physiol 2014; 593:3261-6. [PMID: 26228554 DOI: 10.1113/jphysiol.2014.281147] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2014] [Accepted: 09/19/2014] [Indexed: 11/08/2022] Open
Abstract
The calcium release complex is the major player in excitation-contraction coupling, both in cardiac and skeletal muscle. The core of the complex is the ryanodine receptor, and triadin is a regulating protein. Nevertheless, the precise function of triadin is only partially understood. Besides its function in the anchoring of calsequestrin at the triad/dyad, our recent results allow us to propose hypotheses on new triadin scaffolding functions, based on the studies performed using different models, from triadin knockout mice to human patients, and expression in non-muscle cells, taking into account the presence of multiple triadin isoforms.
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Affiliation(s)
- Isabelle Marty
- Grenoble Institut des Neurosciences, Inserm U836, Université Joseph Fourier-Bat EJ Safra, Chemin Fortuné Ferrini, 38700, La Tronche, France
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Uzhachenko R, Ivanov SV, Yarbrough WG, Shanker A, Medzhitov R, Ivanova AV. Fus1/Tusc2 is a novel regulator of mitochondrial calcium handling, Ca2+-coupled mitochondrial processes, and Ca2+-dependent NFAT and NF-κB pathways in CD4+ T cells. Antioxid Redox Signal 2014; 20:1533-47. [PMID: 24328503 PMCID: PMC3942676 DOI: 10.1089/ars.2013.5437] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
AIMS Fus1 has been established as mitochondrial tumor suppressor, immunomodulator, and antioxidant protein, but molecular mechanism of these activities remained to be identified. Based on putative calcium-binding and myristoyl-binding domains that we identified in Fus1, we explored our hypothesis that Fus1 regulates mitochondrial calcium handling and calcium-coupled processes. RESULTS Fus1 loss resulted in reduced rate of mitochondrial calcium uptake in calcium-loaded epithelial cells, splenocytes, and activated CD4(+) T cells. The reduced rate of mitochondrial calcium uptake in Fus1-deficient cells correlated with cytosolic calcium increase and dysregulation of calcium-coupled mitochondrial parameters, such as reactive oxygen species production, ΔμH(+), mitochondrial permeability transition pore opening, and GSH content. Inhibition of calcium efflux via mitochondria, Na(+)/Ca(2+) exchanger significantly improved the mitochondrial calcium uptake in Fus1(-/-) cells. Ex vivo analysis of activated CD4(+) T cells showed Fus1-dependent changes in calcium-regulated processes, such as surface expression of CD4 and PD1/PD-L1, proliferation, and Th polarization. Fus1(-/-) T cells showed increased basal expression of calcium-dependent NF-κB and NFAT targets but were unable to fully activate these pathways after stimulation. INNOVATION Our results establish Fus1 as one of the few identified regulators of mitochondrial calcium handling. Our data support the idea that alterations in mitochondrial calcium dynamics could lead to the disruption of metabolic coupling in mitochondria that, in turn, may result in multiple cellular and systemic abnormalities. CONCLUSION Our findings suggest that Fus1 achieves its protective role in inflammation, autoimmunity, and cancer via the regulation of mitochondrial calcium and calcium-coupled parameters.
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Affiliation(s)
- Roman Uzhachenko
- 1 Department of Biochemistry and Cancer Biology, VICC, Meharry Medical College , Nashville, Tennessee
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Distinct regions of triadin are required for targeting and retention at the junctional domain of the sarcoplasmic reticulum. Biochem J 2014; 458:407-17. [DOI: 10.1042/bj20130719] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Three regions contribute to triadin localization to the junctional sarcoplasmic reticulum. Dynamics studies revealed that TR3 mediates triadin stability at junctional sites. The stable association of triadin at the junctional sites is facilitated by interactions with calsequestrin-1.
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Demonbreun AR, Rossi AE, Alvarez MG, Swanson KE, Deveaux HK, Earley JU, Hadhazy M, Vohra R, Walter GA, Pytel P, McNally EM. Dysferlin and myoferlin regulate transverse tubule formation and glycerol sensitivity. THE AMERICAN JOURNAL OF PATHOLOGY 2013; 184:248-59. [PMID: 24177035 DOI: 10.1016/j.ajpath.2013.09.009] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/02/2013] [Revised: 09/11/2013] [Accepted: 09/16/2013] [Indexed: 11/28/2022]
Abstract
Dysferlin is a membrane-associated protein implicated in muscular dystrophy and vesicle movement and function in muscles. The precise role of dysferlin has been debated, partly because of the mild phenotype in dysferlin-null mice (Dysf). We bred Dysf mice to mice lacking myoferlin (MKO) to generate mice lacking both myoferlin and dysferlin (FER). FER animals displayed progressive muscle damage with myofiber necrosis, internalized nuclei, and, at older ages, chronic remodeling and increasing creatine kinase levels. These changes were most prominent in proximal limb and trunk muscles and were more severe than in Dysf mice. Consistently, FER animals had reduced ad libitum activity. Ultrastructural studies uncovered progressive dilation of the sarcoplasmic reticulum and ectopic and misaligned transverse tubules in FER skeletal muscle. FER muscle, and Dysf- and MKO-null muscle, exuded lipid, and serum glycerol levels were elevated in FER and Dysf mice. Glycerol injection into muscle is known to induce myopathy, and glycerol exposure promotes detachment of transverse tubules from the sarcoplasmic reticulum. Dysf, MKO, and FER muscles were highly susceptible to glycerol exposure in vitro, demonstrating a dysfunctional sarcotubule system, and in vivo glycerol exposure induced severe muscular dystrophy, especially in FER muscle. Together, these findings demonstrate the importance of dysferlin and myoferlin for transverse tubule function and in the genesis of muscular dystrophy.
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Affiliation(s)
| | - Ann E Rossi
- Department of Medicine, The University of Chicago, Chicago, Illinois
| | - Manuel G Alvarez
- Department of Pathology, The University of Chicago, Chicago, Illinois
| | - Kaitlin E Swanson
- Department of Pathology, The University of Chicago, Chicago, Illinois
| | - H Kieran Deveaux
- Department of Medicine, The University of Chicago, Chicago, Illinois
| | - Judy U Earley
- Department of Medicine, The University of Chicago, Chicago, Illinois
| | - Michele Hadhazy
- Department of Medicine, The University of Chicago, Chicago, Illinois
| | - Ravneet Vohra
- Department of Physiology and Functional Genomics, University of Florida, Gainesville, Florida
| | - Glenn A Walter
- Department of Physiology and Functional Genomics, University of Florida, Gainesville, Florida
| | - Peter Pytel
- Department of Pathology, The University of Chicago, Chicago, Illinois
| | - Elizabeth M McNally
- Department of Medicine, The University of Chicago, Chicago, Illinois; Department of Human Genetics, The University of Chicago, Chicago, Illinois.
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29
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Lee YS, Liu OZ, Hwang HS, Knollmann BC, Sobie EA. Parameter sensitivity analysis of stochastic models provides insights into cardiac calcium sparks. Biophys J 2013; 104:1142-50. [PMID: 23473497 DOI: 10.1016/j.bpj.2012.12.055] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2012] [Revised: 12/02/2012] [Accepted: 12/31/2012] [Indexed: 01/14/2023] Open
Abstract
We present a parameter sensitivity analysis method that is appropriate for stochastic models, and we demonstrate how this analysis generates experimentally testable predictions about the factors that influence local Ca(2+) release in heart cells. The method involves randomly varying all parameters, running a single simulation with each set of parameters, running simulations with hundreds of model variants, then statistically relating the parameters to the simulation results using regression methods. We tested this method on a stochastic model, containing 18 parameters, of the cardiac Ca(2+) spark. Results show that multivariable linear regression can successfully relate parameters to continuous model outputs such as Ca(2+) spark amplitude and duration, and multivariable logistic regression can provide insight into how parameters affect Ca(2+) spark triggering (a probabilistic process that is all-or-none in a single simulation). Benchmark studies demonstrate that this method is less computationally intensive than standard methods by a factor of 16. Importantly, predictions were tested experimentally by measuring Ca(2+) sparks in mice with knockout of the sarcoplasmic reticulum protein triadin. These mice exhibit multiple changes in Ca(2+) release unit structures, and the regression model both accurately predicts changes in Ca(2+) spark amplitude (30% decrease in model, 29% decrease in experiments) and provides an intuitive and quantitative understanding of how much each alteration contributes to the result. This approach is therefore an effective, efficient, and predictive method for analyzing stochastic mathematical models to gain biological insight.
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Affiliation(s)
- Young-Seon Lee
- Department of Pharmacology and Systems Therapeutics, Mount Sinai School of Medicine, New York, New York, USA
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30
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Blech-Hermoni Y, Ladd AN. RNA binding proteins in the regulation of heart development. Int J Biochem Cell Biol 2013; 45:2467-78. [PMID: 23973289 DOI: 10.1016/j.biocel.2013.08.008] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2013] [Revised: 08/09/2013] [Accepted: 08/13/2013] [Indexed: 11/28/2022]
Abstract
In vivo, RNA molecules are constantly accompanied by RNA binding proteins (RBPs), which are intimately involved in every step of RNA biology, including transcription, editing, splicing, transport and localization, stability, and translation. RBPs therefore have opportunities to shape gene expression at multiple levels. This capacity is particularly important during development, when dynamic chemical and physical changes give rise to complex organs and tissues. This review discusses RBPs in the context of heart development. Since the targets and functions of most RBPs--in the heart and at large--are not fully understood, this review focuses on the expression and roles of RBPs that have been implicated in specific stages of heart development or developmental pathology. RBPs are involved in nearly every stage of cardiogenesis, including the formation, morphogenesis, and maturation of the heart. A fuller understanding of the roles and substrates of these proteins could ultimately provide attractive targets for the design of therapies for congenital heart defects, cardiovascular disease, or cardiac tissue repair.
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Affiliation(s)
- Yotam Blech-Hermoni
- Department of Cellular and Molecular Medicine, Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44195, USA; Program in Cell Biology, Department of Molecular Biology and Microbiology, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA
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31
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Chopra N, Knollmann BC. Triadin regulates cardiac muscle couplon structure and microdomain Ca(2+) signalling: a path towards ventricular arrhythmias. Cardiovasc Res 2013; 98:187-91. [PMID: 23396608 DOI: 10.1093/cvr/cvt023] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Since the discovery of triadin >20 years ago as one of the major proteins located in the junctional sarcoplasmic reticulum, the field has come a long way in understanding the pivotal role of triadin in orchestrating sarcoplasmic reticulum Ca(2+)-release and hence excitation-contraction (EC) coupling. Building on the information gathered from earlier lipid bilayer and myocyte overexpression studies, the gene-targeted ablation of Trdn demonstrated triadin's indispensable role for maintaining the structural integrity of the couplon. More recently, the discovery of inherited and acquired diseases displaying altered expression and function of triadin has further emphasized the role of triadin in health and disease. Novel therapeutic approaches could be aimed at correcting the loss of triadin in diseased hearts, and thereby correcting the sub-cellular EC coupling defect. This review summarizes current concepts of the impact of triadin on cardiac EC coupling with a focus towards triadin's role for ventricular arrhythmia.
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Affiliation(s)
- Nagesh Chopra
- Division of Cardiovascular Medicine, Arrhythmia Unit, Brigham and Women's Hospital, Boston, MA, USA
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32
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A skeletal muscle ryanodine receptor interaction domain in triadin. PLoS One 2012; 7:e43817. [PMID: 22937102 PMCID: PMC3427183 DOI: 10.1371/journal.pone.0043817] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2012] [Accepted: 07/26/2012] [Indexed: 11/19/2022] Open
Abstract
Excitation-contraction coupling in skeletal muscle depends, in part, on a functional interaction between the ligand-gated ryanodine receptor (RyR1) and integral membrane protein Trisk 95, localized to the sarcoplasmic reticulum membrane. Various domains on Trisk 95 can associate with RyR1, yet the domain responsible for regulating RyR1 activity has remained elusive. We explored the hypothesis that a luminal Trisk 95 KEKE motif (residues 200-232), known to promote RyR1 binding, may also form the RyR1 activation domain. Peptides corresponding to Trisk 95 residues 200-232 or 200-231 bound to RyR1 and increased the single channel activity of RyR1 by 1.49 ± 0.11-fold and 1.8 ± 0.15-fold respectively, when added to its luminal side. A similar increase in [(3)H]ryanodine binding, which reflects open probability of the channels, was also observed. This RyR1 activation is similar to activation induced by full length Trisk 95. Circular dichroism showed that both peptides were intrinsically disordered, suggesting a defined secondary structure is not necessary to mediate RyR1 activation. These data for the first time demonstrate that Trisk 95's 200-231 region is responsible for RyR1 activation. Furthermore, it shows that no secondary structure is required to achieve this activation, the Trisk 95 residues themselves are critical for the Trisk 95-RyR1 interaction.
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33
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Boncompagni S, Thomas M, Lopez JR, Allen PD, Yuan Q, Kranias EG, Franzini-Armstrong C, Perez CF. Triadin/Junctin double null mouse reveals a differential role for Triadin and Junctin in anchoring CASQ to the jSR and regulating Ca(2+) homeostasis. PLoS One 2012; 7:e39962. [PMID: 22768324 PMCID: PMC3388061 DOI: 10.1371/journal.pone.0039962] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2012] [Accepted: 05/31/2012] [Indexed: 11/17/2022] Open
Abstract
Triadin (Tdn) and Junctin (Jct) are structurally related transmembrane proteins thought to be key mediators of structural and functional interactions between calsequestrin (CASQ) and ryanodine receptor (RyRs) at the junctional sarcoplasmic reticulum (jSR). However, the specific contribution of each protein to the jSR architecture and to excitation-contraction (e-c) coupling has not been fully established. Here, using mouse models lacking either Tdn (Tdn-null), Jct (Jct-null) or both (Tdn/Jct-null), we identify Tdn as the main component of periodically located anchors connecting CASQ to the RyR-bearing jSR membrane. Both proteins proved to be important for the structural organization of jSR cisternae and retention of CASQ within them, but with different degrees of impact. Our results also suggest that the presence of CASQ is responsible for the wide lumen of the jSR cisternae. Using Ca(2+) imaging and Ca(2+) selective microelectrodes we found that changes in e-c coupling, SR Ca(2+)content and resting [Ca(2+)] in Jct, Tdn and Tdn/Jct-null muscles are directly correlated to the effect of each deletion on CASQ content and its organization within the jSR. These data suggest that in skeletal muscle the disruption of Tdn/CASQ link has a more profound effect on jSR architecture and myoplasmic Ca(2+) regulation than Jct/CASQ association.
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Affiliation(s)
- Simona Boncompagni
- DNI-Department of Neuroscience and Imaging, CeSI-Center for Research on Ageing, University of G. D'Annunzio, Chieti, Italy.
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Fourest-Lieuvin A, Rendu J, Osseni A, Pernet-Gallay K, Rossi D, Oddoux S, Brocard J, Sorrentino V, Marty I, Fauré J. Role of triadin in the organization of reticulum membrane at the muscle triad. J Cell Sci 2012; 125:3443-53. [PMID: 22505613 DOI: 10.1242/jcs.100958] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The terminal cisternae represent one of the functional domains of the skeletal muscle sarcoplasmic reticulum (SR). They are closely apposed to plasma membrane invaginations, the T-tubules, with which they form structures called triads. In triads, the physical interaction between the T-tubule-anchored voltage-sensing channel DHPR and the SR calcium channel RyR1 is essential because it allows the depolarization-induced calcium release that triggers muscle contraction. This interaction between DHPR and RyR1 is based on the peculiar membrane structures of both T-tubules and SR terminal cisternae. However, little is known about the molecular mechanisms governing the formation of SR terminal cisternae. We have previously shown that ablation of triadins, a family of SR transmembrane proteins that interact with RyR1, induced skeletal muscle weakness in knockout mice as well as a modification of the shape of triads. Here we explore the intrinsic molecular properties of the longest triadin isoform Trisk 95. We show that when ectopically expressed, Trisk 95 can modulate reticulum membrane morphology. The membrane deformations induced by Trisk 95 are accompanied by modifications of the microtubule network organization. We show that multimerization of Trisk 95 by disulfide bridges, together with interaction with microtubules, are responsible for the ability of Trisk 95 to structure reticulum membrane. When domains responsible for these molecular properties are deleted, anchoring of Trisk 95 to the triads in muscle cells is strongly decreased, suggesting that oligomers of Trisk 95 and microtubules contribute to the organization of the SR terminal cisternae in a triad.
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Affiliation(s)
- Anne Fourest-Lieuvin
- INSERM U836, Grenoble Institut des Neurosciences, Equipe Muscle et Pathologies, Grenoble 38042, France
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35
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Roux-Buisson N, Cacheux M, Fourest-Lieuvin A, Fauconnier J, Brocard J, Denjoy I, Durand P, Guicheney P, Kyndt F, Leenhardt A, Le Marec H, Lucet V, Mabo P, Probst V, Monnier N, Ray PF, Santoni E, Trémeaux P, Lacampagne A, Fauré J, Lunardi J, Marty I. Absence of triadin, a protein of the calcium release complex, is responsible for cardiac arrhythmia with sudden death in human. Hum Mol Genet 2012; 21:2759-67. [PMID: 22422768 PMCID: PMC3363337 DOI: 10.1093/hmg/dds104] [Citation(s) in RCA: 180] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Catecholaminergic polymorphic ventricular tachycardia (CPVT) is an inherited arrhythmogenic disease so far related to mutations in the cardiac ryanodine receptor (RYR2) or the cardiac calsequestrin (CASQ2) genes. Because mutations in RYR2 or in CASQ2 are not retrieved in all CPVT cases, we searched for mutations in the physiological protein partners of RyR2 and CSQ2 in a large cohort of CPVT patients with no detected mutation in these two genes. Based on a candidate gene approach, we focused our investigations on triadin and junctin, two proteins that link RyR2 and CSQ2. Mutations in the triadin (TRDN) and in the junctin (ASPH) genes were searched in a cohort of 97 CPVT patients. We identified three mutations in triadin which cosegregated with the disease on a recessive mode of transmission in two families, but no mutation was found in junctin. Two TRDN mutations, a 4 bp deletion and a nonsense mutation, resulted in premature stop codons; the third mutation, a p.T59R missense mutation, was further studied. Expression of the p.T59R mutant in COS-7 cells resulted in intracellular retention and degradation of the mutant protein. This was confirmed after in vivo expression of the mutant triadin in triadin knock-out mice by viral transduction. In this work, we identified TRDN as a new gene responsible for an autosomal recessive form of CPVT. The mutations identified in the two families lead to the absence of the protein, thereby demonstrating the importance of triadin for the normal function of the cardiac calcium release complex in humans.
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Affiliation(s)
- Nathalie Roux-Buisson
- INSERM U836, Grenoble Institut des Neurosciences, Equipe Muscle et Pathologies, Grenoble, France
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36
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Tomasi M, Canato M, Paolini C, Dainese M, Reggiani C, Volpe P, Protasi F, Nori A. Calsequestrin (CASQ1) rescues function and structure of calcium release units in skeletal muscles of CASQ1-null mice. Am J Physiol Cell Physiol 2011; 302:C575-86. [PMID: 22049211 DOI: 10.1152/ajpcell.00119.2011] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Amplitude of Ca(2+) transients, ultrastructure of Ca(2+) release units, and molecular composition of sarcoplasmic reticulum (SR) are altered in fast-twitch skeletal muscles of calsequestrin-1 (CASQ1)-null mice. To determine whether such changes are directly caused by CASQ1 ablation or are instead the result of adaptive mechanisms, here we assessed ability of CASQ1 in rescuing the null phenotype. In vivo reintroduction of CASQ1 was carried out by cDNA electro transfer in flexor digitorum brevis muscle of the mouse. Exogenous CASQ1 was found to be correctly targeted to the junctional SR (jSR), as judged by immunofluorescence and confocal microscopy; terminal cisternae (TC) lumen was filled with electron dense material and its width was significantly increased, as judged by electron microscopy; peak amplitude of Ca(2+) transients was significantly increased compared with null muscle fibers transfected only with green fluorescent protein (control); and finally, transfected fibers were able to sustain cytosolic Ca(2+) concentration during prolonged tetanic stimulation. Only the expression of TC proteins, such as calsequestrin 2, sarcalumenin, and triadin, was not rescued as judged by Western blot. Thus our results support the view that CASQ1 plays a key role in both Ca(2+) homeostasis and TC structure.
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Affiliation(s)
- Mirta Tomasi
- Dept. of Experimental Biomedical Sciences, Univ. of Padova, Italy
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37
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Perez CF. On the footsteps of Triadin and its role in skeletal muscle. World J Biol Chem 2011; 2:177-83. [PMID: 21909459 PMCID: PMC3165967 DOI: 10.4331/wjbc.v2.i8.177] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/23/2011] [Revised: 07/29/2011] [Accepted: 08/05/2011] [Indexed: 02/05/2023] Open
Abstract
Calcium is a crucial element for striated muscle function. As such, myoplasmic free Ca2+ concentration is delicately regulated through the concerted action of multiple Ca2+ pathways that relay excitation of the plasma membrane to the intracellular contractile machinery. In skeletal muscle, one of these major Ca2+ pathways is Ca2+ release from intracellular Ca2+ stores through type-1 ryanodine receptor/Ca2+ release channels (RyR1), which positions RyR1 in a strategic cross point to regulate Ca2+ homeostasis. This major Ca2+ traffic point appears to be highly sensitive to the intracellular environment, which senses through a plethora of chemical and protein-protein interactions. Among these modulators, perhaps one of the most elusive is Triadin, a muscle-specific protein that is involved in many crucial aspect of muscle function. This family of proteins mediates complex interactions with various Ca2+ modulators and seems poised to be a relevant modulator of Ca2+ signaling in cardiac and skeletal muscles. The purpose of this review is to examine the most recent evidence and current understanding of the role of Triadin in muscle function, in general, with particular emphasis on its contribution to Ca2+ homeostasis.
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Affiliation(s)
- Claudio F Perez
- Claudio F Perez, Department of Anesthesiology, Perioperative and Pain Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, United States
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Al-Qusairi L, Laporte J. T-tubule biogenesis and triad formation in skeletal muscle and implication in human diseases. Skelet Muscle 2011; 1:26. [PMID: 21797990 PMCID: PMC3156648 DOI: 10.1186/2044-5040-1-26] [Citation(s) in RCA: 115] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2011] [Accepted: 07/13/2011] [Indexed: 12/25/2022] Open
Abstract
In skeletal muscle, the excitation-contraction (EC) coupling machinery mediates the translation of the action potential transmitted by the nerve into intracellular calcium release and muscle contraction. EC coupling requires a highly specialized membranous structure, the triad, composed of a central T-tubule surrounded by two terminal cisternae from the sarcoplasmic reticulum. While several proteins located on these structures have been identified, mechanisms governing T-tubule biogenesis and triad formation remain largely unknown. Here, we provide a description of triad structure and plasticity and review the role of proteins that have been linked to T-tubule biogenesis and triad formation and/or maintenance specifically in skeletal muscle: caveolin 3, amphiphysin 2, dysferlin, mitsugumins, junctophilins, myotubularin, ryanodine receptor, and dihydhropyridine Receptor. The importance of these proteins in triad biogenesis and subsequently in muscle contraction is sustained by studies on animal models and by the direct implication of most of these proteins in human myopathies.
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Affiliation(s)
- Lama Al-Qusairi
- Department of Translational Medecine and Neurogenetics, IGBMC (Institut de Génétique et de Biologie Moléculaire et Cellulaire), 1 rue Laurent Fries, 67404 Illkirch, France.
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Ibrahim M, Gorelik J, Yacoub MH, Terracciano CM. The structure and function of cardiac t-tubules in health and disease. Proc Biol Sci 2011; 278:2714-23. [PMID: 21697171 DOI: 10.1098/rspb.2011.0624] [Citation(s) in RCA: 98] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The transverse tubules (t-tubules) are invaginations of the cell membrane rich in several ion channels and other proteins devoted to the critical task of excitation-contraction coupling in cardiac muscle cells (cardiomyocytes). They are thought to promote the synchronous activation of the whole depth of the cell despite the fact that the signal to contract is relayed across the external membrane. However, recent work has shown that t-tubule structure and function are complex and tightly regulated in healthy cardiomyocytes. In this review, we outline the rapidly accumulating knowledge of its novel roles and discuss the emerging evidence of t-tubule dysfunction in cardiac disease, especially heart failure. Controversy surrounds the t-tubules' regulatory elements, and we draw attention to work that is defining these elements from the genetic and the physiological levels. More generally, this field illustrates the challenges in the dissection of the complex relationship between cellular structure and function.
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Affiliation(s)
- Michael Ibrahim
- Harefield Heart Science Centre, Imperial College London, Harefield, Middlesex UB9 6JH, UK
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40
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Reduced gain of excitation-contraction coupling in triadin-null myotubes is mediated by the disruption of FKBP12/RyR1 interaction. Cell Calcium 2011; 49:128-35. [PMID: 21310482 DOI: 10.1016/j.ceca.2011.01.005] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2010] [Revised: 01/10/2011] [Accepted: 01/12/2011] [Indexed: 02/01/2023]
Abstract
Several studies have suggested that triadin (Tdn) may be a critical component of skeletal EC-coupling. However, using Tdn-null mice we have shown that triadin ablation results in no significant disruption of skeletal EC-coupling. To analyze the role of triadin in EC-coupling signaling here we used whole-cell voltage clamp and simultaneous recording of intracellular Ca²+ release to characterize the retrograde and orthograde signaling between RyR1 and DHPR in cultured myotubes. DHPR Ca²+ currents elicited by depolarization of Wt and Tdn-null myotubes displayed similar current densities and voltage dependence. However, kinetic analysis of the Ca²+ current shows that activation time constant of the slow component was slightly decreased in Tdn-null cells. Voltage-evoked Ca²+ transient of Tdn-null myotubes showed small but significant reduction in peak fluorescence amplitude but no differences in voltage dependence. This difference in Ca²+ amplitude was averted by over-expression of FKBP12.6. Our results show that bi-directional signaling between DHPR and RyR1 is preserved nearly intact in Tdn-null myotubes and that the effect of triadin ablation on Ca²+ transients appears to be secondary to the reduced FKBP12 binding capacity of RyR1 in Tdn-null myotubes. These data suggest that skeletal triadins do not play a direct role in skeletal EC-coupling.
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Song DW, Lee JG, Youn HS, Eom SH, Kim DH. Ryanodine receptor assembly: A novel systems biology approach to 3D mapping. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2011; 105:145-61. [DOI: 10.1016/j.pbiomolbio.2010.09.021] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/31/2010] [Revised: 09/14/2010] [Accepted: 09/28/2010] [Indexed: 10/19/2022]
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42
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Tae HS, Cui Y, Karunasekara Y, Board PG, Dulhunty AF, Casarotto MG. Cyclization of the intrinsically disordered α1S dihydropyridine receptor II-III loop enhances secondary structure and in vitro function. J Biol Chem 2011; 286:22589-99. [PMID: 21525002 DOI: 10.1074/jbc.m110.205476] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
A key component of excitation contraction (EC) coupling in skeletal muscle is the cytoplasmic linker (II-III loop) between the second and third transmembrane repeats of the α(1S) subunit of the dihydropyridine receptor (DHPR). The II-III loop has been previously examined in vitro using a linear II-III loop with unrestrained N- and C-terminal ends. To better reproduce the loop structure in its native environment (tethered to the DHPR transmembrane domains), we have joined the N and C termini using intein-mediated technology. Circular dichroism and NMR spectroscopy revealed a structural shift in the cyclized loop toward a protein with increased α-helical and β-strand structure in a region of the loop implicated in its in vitro function and also in a critical region for EC coupling. The affinity of binding of the II-III loop binding to the SPRY2 domain of the skeletal ryanodine receptor (RyR1) increased 4-fold, and its ability to activate RyR1 channels in lipid bilayers was enhanced 3-fold by cyclization. These functional changes were predicted consequences of the structural enhancement. We suggest that tethering the N and C termini stabilized secondary structural elements in the DHPR II-III loop and may reflect structural and dynamic characteristics of the loop that are inherent in EC coupling.
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Affiliation(s)
- Han-Shen Tae
- John Curtin School of Medical Research, Australian National University, PO Box 334, Canberra, Australian Capital Territory 2601, Australia
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Novák P, Soukup T. Calsequestrin distribution, structure and function, its role in normal and pathological situations and the effect of thyroid hormones. Physiol Res 2011; 60:439-52. [PMID: 21401301 DOI: 10.33549/physiolres.931989] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
Calsequestrin is the main calcium binding protein of the sarcoplasmic reticulum, serving as an important regulator of Ca(2+). In mammalian muscles, it exists as a skeletal isoform found in fast- and slow-twitch skeletal muscles and a cardiac isoform expressed in the heart and slow-twitch muscles. Recently, many excellent reviews that summarised in great detail various aspects of the calsequestrin structure, localisation or function both in skeletal and cardiac muscle have appeared. The present review focuses on skeletal muscle: information on cardiac tissue is given, where differences between both tissues are functionally important. The article reviews the known multiple roles of calsequestrin including pathology in order to introduce this topic to the broader scientific community and to stimulate an interest in this protein. Newly we describe our results on the effect of thyroid hormones on skeletal and cardiac calsequestrin expression and discuss them in the context of available literary data on this topic.
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Affiliation(s)
- P Novák
- Institute of Physiology, Academy of Sciences of the Czech Republic, Prague, Czech Republic
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Excitation-contraction coupling and minor triadic proteins in low-frequency fatigue. Exerc Sport Sci Rev 2010; 38:135-42. [PMID: 20577062 DOI: 10.1097/jes.0b013e3181e3734d] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Low-frequency fatigue (LFF) is characterized by a proportionally greater loss of force at low compared with high activation frequencies and a prolonged recovery. Recent work suggests a calcium-induced uncoupling of excitation-contraction coupling underlies LFF. Here, newly characterized triadic proteins are described, and possible mechanisms by which they may contribute to LFF are suggested.
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Eltit JM, Feng W, Lopez JR, Padilla IT, Pessah IN, Molinski TF, Fruen BR, Allen PD, Perez CF. Ablation of skeletal muscle triadin impairs FKBP12/RyR1 channel interactions essential for maintaining resting cytoplasmic Ca2+. J Biol Chem 2010; 285:38453-62. [PMID: 20926377 DOI: 10.1074/jbc.m110.164525] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Previously, we have shown that lack of expression of triadins in skeletal muscle cells results in significant increase of myoplasmic resting free Ca(2+) ([Ca(2+)](rest)), suggesting a role for triadins in modulating global intracellular Ca(2+) homeostasis. To understand this mechanism, we study here how triadin alters [Ca(2+)](rest), Ca(2+) release, and Ca(2+) entry pathways using a combination of Ca(2+) microelectrodes, channels reconstituted in bilayer lipid membranes (BLM), Ca(2+), and Mn(2+) imaging analyses of myotubes and RyR1 channels obtained from triadin-null mice. Unlike WT cells, triadin-null myotubes had chronically elevated [Ca(2+)](rest) that was sensitive to inhibition with ryanodine, suggesting that triadin-null cells have increased basal RyR1 activity. Consistently, BLM studies indicate that, unlike WT-RyR1, triadin-null channels more frequently display atypical gating behavior with multiple and stable subconductance states. Accordingly, pulldown analysis and fluorescent FKBP12 binding studies in triadin-null muscles revealed a significant impairment of the FKBP12/RyR1 interaction. Mn(2+) quench rates under resting conditions indicate that triadin-null cells also have higher Ca(2+) entry rates and lower sarcoplasmic reticulum Ca(2+) load than WT cells. Overexpression of FKBP12.6 reverted the null phenotype, reducing resting Ca(2+) entry, recovering sarcoplasmic reticulum Ca(2+) content levels, and restoring near normal [Ca(2+)](rest). Exogenous FKBP12.6 also reduced the RyR1 channel P(o) but did not rescue subconductance behavior. In contrast, FKBP12 neither reduced P(o) nor recovered multiple subconductance gating. These data suggest that elevated [Ca(2+)](rest) in triadin-null myotubes is primarily driven by dysregulated RyR1 channel activity that results in part from impaired FKBP12/RyR1 functional interactions and a secondary increased Ca(2+) entry at rest.
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Affiliation(s)
- Jose M Eltit
- Department of Anesthesiology, Brigham and Women's Hospital, Boston, Massachusetts 02115, USA
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Vassilopoulos S, Oddoux S, Groh S, Cacheux M, Fauré J, Brocard J, Campbell KP, Marty I. Caveolin 3 is associated with the calcium release complex and is modified via in vivo triadin modification. Biochemistry 2010; 49:6130-5. [PMID: 20565104 PMCID: PMC2907096 DOI: 10.1021/bi100796v] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The triadin isoforms Trisk 95 and Trisk 51 are both components of the skeletal muscle calcium release complex. To investigate the specific role of Trisk 95 and Trisk 51 isoforms in muscle physiology, we overexpressed Trisk 95 or Trisk 51 using adenovirus-mediated gene transfer in skeletal muscle of newborn mice. Overexpression of either Trisk 95 or Trisk 51 alters the muscle fiber morphology, while leaving unchanged the expression of the ryanodine receptor, the dihydropyridine receptor, and calsequestrin. We also observe an aberrant expression of caveolin 3 in both Trisk 95- and Trisk 51-overexpressing skeletal muscles. Using a biochemical approach, we demonstrate that caveolin 3 is associated with the calcium release complex in skeletal muscle. Taking advantage of muscle and non-muscle cell culture models and triadin null mouse skeletal muscle, we further dissect the molecular organization of the caveolin 3-containing calcium release complex. Our data demonstrate that the association of caveolin 3 with the calcium release complex occurs via a direct interaction with the transmembrane domain of the ryanodine receptor. Taken together, these data suggest that caveolin 3-containing membrane domains and the calcium release complex are functionally linked and that Trisk 95 and Trisk 51 are instrumental to the regulation of this interaction, the integrity of which may be crucial for muscle physiology.
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Affiliation(s)
- Stéphane Vassilopoulos
- INSERM U836, Grenoble Institut des Neurosciences, Equipe Muscle et Pathologies, Grenoble, France
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Franzini-Armstrong C. RyRs: Their Disposition, Frequency, and Relationships with Other Proteins of Calcium Release Units. CURRENT TOPICS IN MEMBRANES 2010; 66:3-26. [PMID: 22353474 DOI: 10.1016/s1063-5823(10)66001-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/09/2022]
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Qin J, Valle G, Nani A, Chen H, Ramos-Franco J, Nori A, Volpe P, Fill M. Ryanodine receptor luminal Ca2+ regulation: swapping calsequestrin and channel isoforms. Biophys J 2009; 97:1961-70. [PMID: 19804727 DOI: 10.1016/j.bpj.2009.07.030] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2009] [Revised: 07/10/2009] [Accepted: 07/21/2009] [Indexed: 11/20/2022] Open
Abstract
Sarcoplasmic reticulum (SR) Ca(2+) release in striated muscle is mediated by a multiprotein complex that includes the ryanodine receptor (RyR) Ca(2+) channel and the intra-SR Ca(2+) buffering protein calsequestrin (CSQ). Besides its buffering role, CSQ is thought to regulate RyR channel function. Here, CSQ-dependent luminal Ca(2+) regulation of skeletal (RyR1) and cardiac (RyR2) channels is explored. Skeletal (CSQ1) or cardiac (CSQ2) calsequestrin were systematically added to the luminal side of single RyR1 or RyR2 channels. The luminal Ca(2+) dependence of open probability (Po) over the physiologically relevant range (0.05-1 mM Ca(2+)) was defined for each of the four RyR/CSQ isoform pairings. We found that the luminal Ca(2+) sensitivity of single RyR2 channels was substantial when either CSQ isoform was present. In contrast, no significant luminal Ca(2+) sensitivity of single RyR1 channels was detected in the presence of either CSQ isoform. We conclude that CSQ-dependent luminal Ca(2+) regulation of single RyR2 channels lacks CSQ isoform specificity, and that CSQ-dependent luminal Ca(2+) regulation in skeletal muscle likely plays a relatively minor (if any) role in regulating the RyR1 channel activity, indicating that the chief role of CSQ1 in this tissue is as an intra-SR Ca(2+) buffer.
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Affiliation(s)
- Jia Qin
- Department of Molecular Biophysics and Physiology, Rush University Medical Center, Chicago, Illinois, USA
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T-tubule disorganization and defective excitation-contraction coupling in muscle fibers lacking myotubularin lipid phosphatase. Proc Natl Acad Sci U S A 2009; 106:18763-8. [PMID: 19846786 DOI: 10.1073/pnas.0900705106] [Citation(s) in RCA: 144] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Skeletal muscle contraction is triggered by the excitation-contraction (E-C) coupling machinery residing at the triad, a membrane structure formed by the juxtaposition of T-tubules and sarcoplasmic reticulum (SR) cisternae. The formation and maintenance of this structure is key for muscle function but is not well characterized. We have investigated the mechanisms leading to X-linked myotubular myopathy (XLMTM), a severe congenital disorder due to loss of function mutations in the MTM1 gene, encoding myotubularin, a phosphoinositide phosphatase thought to have a role in plasma membrane homeostasis and endocytosis. Using a mouse model of the disease, we report that Mtm1-deficient muscle fibers have a decreased number of triads and abnormal longitudinally oriented T-tubules. In addition, SR Ca(2+) release elicited by voltage-clamp depolarizations is strongly depressed in myotubularin-deficient muscle fibers, with myoplasmic Ca(2+) removal and SR Ca(2+) content essentially unaffected. At the molecular level, Mtm1-deficient myofibers exhibit a 3-fold reduction in type 1 ryanodine receptor (RyR1) protein level. These data reveal a critical role of myotubularin in the proper organization and function of the E-C coupling machinery and strongly suggest that defective RyR1-mediated SR Ca(2+) release is responsible for the failure of muscle function in myotubular myopathy.
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Affiliation(s)
- Angela Dulhunty
- John Curtin School of Medical Research, Canberra City, ACT, Australia.
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