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Franzini-Armstrong C. An updated view of the structural basis for dihydropyridine receptors-ryanodine receptors direct molecular interaction in skeletal muscle. Eur J Transl Myol 2024; 34:12476. [PMID: 38516838 PMCID: PMC11017163 DOI: 10.4081/ejtm.2024.12476] [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: 03/14/2024] [Accepted: 03/14/2024] [Indexed: 03/23/2024] Open
Abstract
This presentation reviews images of electron micrographs from various skeletal muscles identifying a consistent association of diydropyridine receptors (DHPR) tetrads with alternate ryanodine receptors. Imaging of the junctional gap in triads from various sources provide direct evidence for the association of four diydropyridine receptors (DHPRs), clustered into tetrads, with alternate ryanodine receptors (RyRs). It is not clear whether firing of all four components of a tetrad is necessary to fully activate the opening of the RyR channel.
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Affiliation(s)
- Clara Franzini-Armstrong
- Department of Cell and Developmental Biology, University of Pennsylvania School of Medicine, Philadelphia, PA.
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2
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Raisch T, Raunser S. The modes of action of ion-channel-targeting neurotoxic insecticides: lessons from structural biology. Nat Struct Mol Biol 2023; 30:1411-1427. [PMID: 37845413 DOI: 10.1038/s41594-023-01113-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2022] [Accepted: 08/31/2023] [Indexed: 10/18/2023]
Abstract
Insecticides are indispensable tools for plant protection in modern agriculture. Despite having highly heterogeneous structures, many neurotoxic insecticides use similar principles to inhibit or deregulate neuronal ion channels. Insecticides targeting pentameric ligand-gated channels are structural mimetics of neurotransmitters or manipulate and deregulate the proteins. Those binding to (pseudo-)tetrameric voltage-gated(-like) channels, on the other hand, are natural or synthetic compounds that directly block the ion-conducting pore or prevent conformational changes in the transmembrane domain necessary for opening and closing the pore. The use of a limited number of inhibition mechanisms can be problematic when resistances arise and become more widespread. Therefore, there is a rising interest in the development of insecticides with novel mechanisms that evade resistance and are pest-insect-specific. During the last decade, most known insecticide targets, many with bound compounds, have been structurally characterized, bringing the rational design of novel classes of agrochemicals within closer reach than ever before.
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Affiliation(s)
- Tobias Raisch
- Department of Structural Biochemistry, Max Planck Institute of Molecular Physiology, Dortmund, Germany.
| | - Stefan Raunser
- Department of Structural Biochemistry, Max Planck Institute of Molecular Physiology, Dortmund, Germany.
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3
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Murzilli S, Serano M, Pietrangelo L, Protasi F, Paolini C. Structural Adaptation of the Excitation-Contraction Coupling Apparatus in Calsequestrin1-Null Mice during Postnatal Development. BIOLOGY 2023; 12:1064. [PMID: 37626950 PMCID: PMC10452101 DOI: 10.3390/biology12081064] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/30/2023] [Revised: 07/21/2023] [Accepted: 07/26/2023] [Indexed: 08/27/2023]
Abstract
The precise arrangement and peculiar interaction of transverse tubule (T-tubule) and sarcoplasmic reticulum (SR) membranes efficiently guarantee adequate contractile properties of skeletal muscle fibers. Fast muscle fibers from mice lacking calsequestrin 1 (CASQ1) are characterized by the profound ultrastructural remodeling of T-tubule/SR junctions. This study investigates the role of CASQ1, an essential component of calcium release units (CRUs), in the postnatal development of muscle fibers. By using CASQ1-knockout mice, we examined the maturation of CRUs and the involvement of different junctional proteins in the juxtaposition of the membrane system. Our morphological investigation of both wild-type (WT) and CASQ1-null extensor digitorum longus (EDL) fibers, from 1 week to 4 months of age, yielded noteworthy findings. Firstly, we observed that the absence of CASQ1 hindered the full maturation of CRUs, despite the correct localization of key junctional components (ryanodine receptor, dihydropyridine receptor, and triadin) to the junctional SR in adult animals. Furthermore, analysis of protein expression profiles related to T-tubule biogenesis and organization (junctophilin 1, amphiphysin 2, caveolin 3, and mitsugumin 29) demonstrated delayed progression in their expression during postnatal development in the absence of CASQ1, suggesting the impaired maturation of CRUs. The absence of CASQ1 directly impacts the proper assembly of CRUs during development and influences the expression and coordination of other proteins involved in T-tubule biogenesis and organization.
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Affiliation(s)
- Stefania Murzilli
- Department of Neuroscience, Imaging and Clinical Sciences (DNISC), Center for Advanced Studies and Technology (CAST), University G. d’Annunzio of Chieti-Pescara, 66100 Chieti, Italy;
| | - Matteo Serano
- Department of Medicine and Aging Sciences (DMSI), Center for Advanced Studies and Technology (CAST), University G. d’Annunzio of Chieti-Pescara, 66100 Chieti, Italy; (M.S.); (L.P.); (F.P.)
| | - Laura Pietrangelo
- Department of Medicine and Aging Sciences (DMSI), Center for Advanced Studies and Technology (CAST), University G. d’Annunzio of Chieti-Pescara, 66100 Chieti, Italy; (M.S.); (L.P.); (F.P.)
| | - Feliciano Protasi
- Department of Medicine and Aging Sciences (DMSI), Center for Advanced Studies and Technology (CAST), University G. d’Annunzio of Chieti-Pescara, 66100 Chieti, Italy; (M.S.); (L.P.); (F.P.)
| | - Cecilia Paolini
- Department of Neuroscience, Imaging and Clinical Sciences (DNISC), Center for Advanced Studies and Technology (CAST), University G. d’Annunzio of Chieti-Pescara, 66100 Chieti, Italy;
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4
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Protasi F, Girolami B, Roccabianca S, Rossi D. Store-operated calcium entry: From physiology to tubular aggregate myopathy. Curr Opin Pharmacol 2023; 68:102347. [PMID: 36608411 DOI: 10.1016/j.coph.2022.102347] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2022] [Revised: 11/30/2022] [Accepted: 12/04/2022] [Indexed: 01/06/2023]
Abstract
Store-Operated Ca2+ entry (SOCE) is recognized as a key mechanism in muscle physiology necessary to refill intracellular Ca2+ stores during sustained muscle activity. For many years the cell structures expected to mediate SOCE in skeletal muscle fibres remained unknown. Recently, the identification of Ca2+ Entry Units (CEUs) in exercised muscle fibres opened new insights into the role of extracellular Ca2+ in muscle contraction and, more generally, in intracellular Ca2+ homeostasis. Accordingly, intracellular Ca2+ unbalance due to alterations in SOCE strictly correlates with muscle disfunction and disease. Mutations in proteins involved in SOCE (STIM1, ORAI1, and CASQ1) have been linked to tubular aggregate myopathy (TAM), a disease that causes muscle weakness and myalgia and is characterized by a typical accumulation of highly ordered and packed membrane tubules originated from the sarcoplasmic reticulum (SR). Achieving a full understanding of the molecular pathways activated by alterations in Ca2+ entry mechanisms is a necessary step to design effective therapies for human SOCE-related disorders.
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Affiliation(s)
- Feliciano Protasi
- CAST, Center for Advanced Studies and Technology; University G. d'Annunzio of Chieti-Pescara, I-66100, Italy; DMSI, Department of Medicine and Aging Sciences; University G. d'Annunzio of Chieti-Pescara, I-66100, Italy
| | - Barbara Girolami
- CAST, Center for Advanced Studies and Technology; University G. d'Annunzio of Chieti-Pescara, I-66100, Italy; DMSI, Department of Medicine and Aging Sciences; University G. d'Annunzio of Chieti-Pescara, I-66100, Italy
| | - Sara Roccabianca
- DMMS, Department of Molecular and Developmental Medicine; University of Siena, I-53100, Siena Italy
| | - Daniela Rossi
- DMMS, Department of Molecular and Developmental Medicine; University of Siena, I-53100, Siena Italy.
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5
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Brooks SV, Guzman SD, Ruiz LP. Skeletal muscle structure, physiology, and function. HANDBOOK OF CLINICAL NEUROLOGY 2023; 195:3-16. [PMID: 37562874 DOI: 10.1016/b978-0-323-98818-6.00013-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/12/2023]
Abstract
Contractions of skeletal muscles provide the stability and power for all body movements. Consequently, any impairment in skeletal muscle function results in some degree of instability or immobility. Factors that influence skeletal muscle structure and function are therefore of great interest scientifically and clinically. Injury, neuromuscular disease, and old age are among the factors that commonly contribute to impairments in skeletal muscle function. The goal of this chapter is to summarize the fundamentals of skeletal muscle structure and function to provide foundational knowledge for this Handbook volume. We examine the molecular interactions that provide the basis for the generation of force and movement, discuss mechanisms of the regulation of contraction at the level of myofibers, and introduce concepts of the activation and control of muscle function in vivo. Where appropriate, the chapter updates the emerging science that will increase understanding of muscle function.
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Affiliation(s)
- Susan V Brooks
- Department of Molecular & Integrative Physiology, University of Michigan, Ann Arbor, MI, United States; Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, United States.
| | - Steve D Guzman
- Department of Molecular & Integrative Physiology, University of Michigan, Ann Arbor, MI, United States
| | - Lloyd P Ruiz
- Department of Molecular & Integrative Physiology, University of Michigan, Ann Arbor, MI, United States
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6
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Protasi F, Girolami B, Serano M, Pietrangelo L, Paolini C. Ablation of Calsequestrin-1, Ca 2+ unbalance, and susceptibility to heat stroke. Front Physiol 2022; 13:1033300. [PMID: 36311237 PMCID: PMC9598425 DOI: 10.3389/fphys.2022.1033300] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2022] [Accepted: 09/20/2022] [Indexed: 12/05/2022] Open
Abstract
Introduction: Ca2+ levels in adult skeletal muscle fibers are mainly controlled by excitation-contraction (EC) coupling, a mechanism that translates action potentials in release of Ca2+ from the sarcoplasmic reticulum (SR) release channels, i.e. the ryanodine receptors type-1 (RyR1). Calsequestrin (Casq) is a protein that binds large amounts of Ca2+ in the lumen of the SR terminal cisternae, near sites of Ca2+ release. There is general agreement that Casq is not only important for the SR ability to store Ca2+, but also for modulating the opening probability of the RyR Ca2+ release channels. The initial studies: About 20 years ago we generated a mouse model lacking Casq1 (Casq1-null mice), the isoform predominantly expressed in adult fast twitch skeletal muscle. While the knockout was not lethal as expected, lack of Casq1 caused a striking remodeling of membranes of SR and of transverse tubules (TTs), and mitochondrial damage. Functionally, CASQ1-knockout resulted in reduced SR Ca2+ content, smaller Ca2+ transients, and severe SR depletion during repetitive stimulation. The myopathic phenotype of Casq1-null mice: After the initial studies, we discovered that Casq1-null mice were prone to sudden death when exposed to halogenated anaesthetics, heat and even strenuous exercise. These syndromes are similar to human malignant hyperthermia susceptibility (MHS) and environmental-exertional heat stroke (HS). We learned that mechanisms underlying these syndromes involved excessive SR Ca2+ leak and excessive production of oxidative species: indeed, mortality and mitochondrial damage were significantly prevented by administration of antioxidants and reduction of oxidative stress. Though, how Casq1-null mice could survive without the most important SR Ca2+ binding protein was a puzzling issue that was not solved. Unravelling the mystery: The mystery was finally solved in 2020, when we discovered that in Casq1-null mice the SR undergoes adaptations that result in constitutively active store-operated Ca2+ entry (SOCE). SOCE is a mechanism that allows skeletal fibers to use external Ca2+ when SR stores are depleted. The post-natal compensatory mechanism that allows Casq1-null mice to survive involves the assembly of new SR-TT junctions (named Ca2+ entry units) containing Stim1 and Orai1, the two proteins that mediate SOCE.
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Affiliation(s)
- Feliciano Protasi
- Center for Advanced Studies and Technology, University G. d’Annunzio of Chieti-Pescara, Chieti, Italy
- Department of Medicine and Aging Sciences, University G. d’Annunzio of Chieti-Pescara, Chieti, Italy
| | - Barbara Girolami
- Center for Advanced Studies and Technology, University G. d’Annunzio of Chieti-Pescara, Chieti, Italy
- Department of Medicine and Aging Sciences, University G. d’Annunzio of Chieti-Pescara, Chieti, Italy
| | - Matteo Serano
- Center for Advanced Studies and Technology, University G. d’Annunzio of Chieti-Pescara, Chieti, Italy
- Department of Medicine and Aging Sciences, University G. d’Annunzio of Chieti-Pescara, Chieti, Italy
| | - Laura Pietrangelo
- Center for Advanced Studies and Technology, University G. d’Annunzio of Chieti-Pescara, Chieti, Italy
- Department of Medicine and Aging Sciences, University G. d’Annunzio of Chieti-Pescara, Chieti, Italy
| | - Cecilia Paolini
- Center for Advanced Studies and Technology, University G. d’Annunzio of Chieti-Pescara, Chieti, Italy
- Department of Neuroscience, Imaging and Clinical Sciences, University G. d’Annunzio of Chieti-Pescara, Chieti, Italy
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Dixon RE, Navedo MF, Binder MD, Santana LF. Mechanisms and Physiological Implications of Cooperative Gating of Ion Channels Clusters. Physiol Rev 2021; 102:1159-1210. [PMID: 34927454 DOI: 10.1152/physrev.00022.2021] [Citation(s) in RCA: 33] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Ion channels play a central role in the regulation of nearly every cellular process. Dating back to the classic 1952 Hodgkin-Huxley model of the generation of the action potential, ion channels have always been thought of as independent agents. A myriad of recent experimental findings exploiting advances in electrophysiology, structural biology, and imaging techniques, however, have posed a serious challenge to this long-held axiom as several classes of ion channels appear to open and close in a coordinated, cooperative manner. Ion channel cooperativity ranges from variable-sized oligomeric cooperative gating in voltage-gated, dihydropyridine-sensitive Cav1.2 and Cav1.3 channels to obligatory dimeric assembly and gating of voltage-gated Nav1.5 channels. Potassium channels, transient receptor potential channels, hyperpolarization cyclic nucleotide-activated channels, ryanodine receptors (RyRs), and inositol trisphosphate receptors (IP3Rs) have also been shown to gate cooperatively. The implications of cooperative gating of these ion channels range from fine tuning excitation-contraction coupling in muscle cells to regulating cardiac function and vascular tone, to modulation of action potential and conduction velocity in neurons and cardiac cells, and to control of pace-making activity in the heart. In this review, we discuss the mechanisms leading to cooperative gating of ion channels, their physiological consequences and how alterations in cooperative gating of ion channels may induce a range of clinically significant pathologies.
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Affiliation(s)
- Rose Ellen Dixon
- Department of Physiology and Membrane Biology, University of California, Davis, CA, United States
| | - Manuel F Navedo
- Department of Pharmacology, University of California, Davis, CA, United States
| | - Marc D Binder
- Department of Physiology and Biophysics, University of Washington, Seattle, WA, United States
| | - L Fernando Santana
- Department of Physiology and Membrane Biology, University of California, Davis, CA, United States
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8
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Kobayashi T, Kurebayashi N, Murayama T. The Ryanodine Receptor as a Sensor for Intracellular Environments in Muscles. Int J Mol Sci 2021; 22:ijms221910795. [PMID: 34639137 PMCID: PMC8509754 DOI: 10.3390/ijms221910795] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2021] [Revised: 10/02/2021] [Accepted: 10/04/2021] [Indexed: 01/12/2023] Open
Abstract
The ryanodine receptor (RyR) is a Ca2+ release channel in the sarcoplasmic reticulum of skeletal and cardiac muscles and plays a key role in excitation-contraction coupling. The activity of the RyR is regulated by the changes in the level of many intracellular factors, such as divalent cations (Ca2+ and Mg2+), nucleotides, associated proteins, and reactive oxygen species. Since these intracellular factors change depending on the condition of the muscle, e.g., exercise, fatigue, or disease states, the RyR channel activity will be altered accordingly. In this review, we describe how the RyR channel is regulated under various conditions and discuss the possibility that the RyR acts as a sensor for changes in the intracellular environments in muscles.
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9
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Iyer R, Franzini-Armstrong C. The location of InsP3 receptors in Purkinje cells of murine cerebellum does not supports a direct interaction in the transfer of calcium ions between ER and mitochondria. Eur J Transl Myol 2021; 31. [PMID: 34498451 PMCID: PMC8495361 DOI: 10.4081/ejtm.2021.9935] [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: 06/23/2021] [Accepted: 08/06/2021] [Indexed: 11/23/2022] Open
Abstract
The inositol-3-phosphate receptors (IP3Rs) of cerebellar Purkinje cells are located in abundant, large stacks of endoplasmic reticulum (ER) cisternae. Using thin section electron microscopy, we identify very frequent associations of the ER stacks with mitochondria. The associations have two components: a single, close ER-mitochondria contact on one side to the stack, and multiple layers of ER cisternae decorated by IP3Rs receptors on the side away from the mitochondria. Due to their location in the stacks, IP3Rs are never in contact with the mitochondria, although they are in their vicinity. We conclude that transfer of Ca2+ between ER and mitochondria is not directly mediated by IP3Rs, but is based on mitochondrial Ca2+ uptake from the local cytoplasmic spikes during IP3Rs’ activity.
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Affiliation(s)
- Ramesh Iyer
- Division of Cardiology, Children Hospital of Philadelphia, Philadelphia, PA.
| | - Clara Franzini-Armstrong
- Department of Cell and Developmental Biology, School of Medicine, University of Pennsylvania, Philadelphia, PA.
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10
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Protasi F, Pietrangelo L, Boncompagni S. Improper Remodeling of Organelles Deputed to Ca 2+ Handling and Aerobic ATP Production Underlies Muscle Dysfunction in Ageing. Int J Mol Sci 2021; 22:6195. [PMID: 34201319 PMCID: PMC8228829 DOI: 10.3390/ijms22126195] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2021] [Revised: 06/01/2021] [Accepted: 06/02/2021] [Indexed: 12/28/2022] Open
Abstract
Proper skeletal muscle function is controlled by intracellular Ca2+ concentration and by efficient production of energy (ATP), which, in turn, depend on: (a) the release and re-uptake of Ca2+ from sarcoplasmic-reticulum (SR) during excitation-contraction (EC) coupling, which controls the contraction and relaxation of sarcomeres; (b) the uptake of Ca2+ into the mitochondrial matrix, which stimulates aerobic ATP production; and finally (c) the entry of Ca2+ from the extracellular space via store-operated Ca2+ entry (SOCE), a mechanism that is important to limit/delay muscle fatigue. Abnormalities in Ca2+ handling underlie many physio-pathological conditions, including dysfunction in ageing. The specific focus of this review is to discuss the importance of the proper architecture of organelles and membrane systems involved in the mechanisms introduced above for the correct skeletal muscle function. We reviewed the existing literature about EC coupling, mitochondrial Ca2+ uptake, SOCE and about the structural membranes and organelles deputed to those functions and finally, we summarized the data collected in different, but complementary, projects studying changes caused by denervation and ageing to the structure and positioning of those organelles: a. denervation of muscle fibers-an event that contributes, to some degree, to muscle loss in ageing (known as sarcopenia)-causes misplacement and damage: (i) of membrane structures involved in EC coupling (calcium release units, CRUs) and (ii) of the mitochondrial network; b. sedentary ageing causes partial disarray/damage of CRUs and of calcium entry units (CEUs, structures involved in SOCE) and loss/misplacement of mitochondria; c. functional electrical stimulation (FES) and regular exercise promote the rescue/maintenance of the proper architecture of CRUs, CEUs, and of mitochondria in both denervation and ageing. All these structural changes were accompanied by related functional changes, i.e., loss/decay in function caused by denervation and ageing, and improved function following FES or exercise. These data suggest that the integrity and proper disposition of intracellular organelles deputed to Ca2+ handling and aerobic generation of ATP is challenged by inactivity (or reduced activity); modifications in the architecture of these intracellular membrane systems may contribute to muscle dysfunction in ageing and sarcopenia.
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Affiliation(s)
- Feliciano Protasi
- CAST, Center for Advanced Studies and Technology, University G. d’Annunzio of Chieti-Pescara, I-66100 Chieti, Italy; (L.P.); (S.B.)
- DMSI, Department of Medicine and Aging Sciences, University G. d’Annunzio of Chieti-Pescara, I-66100 Chieti, Italy
| | - Laura Pietrangelo
- CAST, Center for Advanced Studies and Technology, University G. d’Annunzio of Chieti-Pescara, I-66100 Chieti, Italy; (L.P.); (S.B.)
- DMSI, Department of Medicine and Aging Sciences, University G. d’Annunzio of Chieti-Pescara, I-66100 Chieti, Italy
| | - Simona Boncompagni
- CAST, Center for Advanced Studies and Technology, University G. d’Annunzio of Chieti-Pescara, I-66100 Chieti, Italy; (L.P.); (S.B.)
- DNICS, Department of Neuroscience and Clinical Sciences, University G. d’Annunzio of Chieti-Pescara, I-66100 Chieti, Italy
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11
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Zhang SS, Zhou S, Crowley-McHattan ZJ, Wang RY, Li JP. A Review of the Role of Endo/Sarcoplasmic Reticulum-Mitochondria Ca 2+ Transport in Diseases and Skeletal Muscle Function. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2021; 18:ijerph18083874. [PMID: 33917091 PMCID: PMC8067840 DOI: 10.3390/ijerph18083874] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/21/2021] [Revised: 03/23/2021] [Accepted: 03/24/2021] [Indexed: 02/07/2023]
Abstract
The physical contact site between a mitochondrion and endoplasmic reticulum (ER), named the mitochondria-associated membrane (MAM), has emerged as a fundamental platform for regulating the functions of the two organelles and several cellular processes. This includes Ca2+ transport from the ER to mitochondria, mitochondrial dynamics, autophagy, apoptosis signalling, ER stress signalling, redox reaction, and membrane structure maintenance. Consequently, the MAM is suggested to be involved in, and as a possible therapeutic target for, some common diseases and impairment in skeletal muscle function, such as insulin resistance and diabetes, obesity, neurodegenerative diseases, Duchenne muscular dystrophy, age-related muscle atrophy, and exercise-induced muscle damage. In the past decade, evidence suggests that alterations in Ca2+ transport from the ER to mitochondria, mediated by the macromolecular complex formed by IP3R, Grp75, and VDAC1, may be a universal mechanism for how ER-mitochondria cross-talk is involved in different physiological/pathological conditions mentioned above. A better understanding of the ER (or sarcoplasmic reticulum in muscle)-mitochondria Ca2+ transport system may provide a new perspective for exploring the mechanism of how the MAM is involved in the pathology of diseases and skeletal muscle dysfunction. This review provides a summary of recent research findings in this area.
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Affiliation(s)
- Shuang-Shuang Zhang
- School of Sport Science, Beijing Sport University, Beijing 100084, China; (S.-S.Z.); (J.-P.L.)
- Faculty of Health, Southern Cross University, East Lismore, NSW 2480, Australia; (S.Z.); (Z.J.C.-M.)
| | - Shi Zhou
- Faculty of Health, Southern Cross University, East Lismore, NSW 2480, Australia; (S.Z.); (Z.J.C.-M.)
| | | | - Rui-Yuan Wang
- School of Sport Science, Beijing Sport University, Beijing 100084, China; (S.-S.Z.); (J.-P.L.)
- Correspondence:
| | - Jun-Ping Li
- School of Sport Science, Beijing Sport University, Beijing 100084, China; (S.-S.Z.); (J.-P.L.)
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12
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Balderas-Villalobos J, Steele TWE, Eltit JM. Physiological and Pathological Relevance of Selective and Nonselective Ca 2+ Channels in Skeletal and Cardiac Muscle. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2021; 1349:225-247. [PMID: 35138617 PMCID: PMC10683374 DOI: 10.1007/978-981-16-4254-8_11] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Contraction of the striated muscle is fundamental for human existence. The action of voluntary skeletal muscle enables activities such as breathing, establishing body posture, and diverse body movements. Additionally, highly precise motion empowers communication, artistic expression, and other activities that define everyday human life. The involuntary contraction of striated muscle is the core function of the heart and is essential for blood flow. Several ion channels are important in the transduction of action potentials to cytosolic Ca2+ signals that enable muscle contraction; however, other ion channels are involved in the progression of muscle pathologies that can impair normal life or threaten it. This chapter describes types of selective and nonselective Ca2+ permeable ion channels expressed in the striated muscle, their participation in different aspects of muscle excitation and contraction, and their relevance to the progression of some pathological states.
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Affiliation(s)
- Jaime Balderas-Villalobos
- Department of Physiology and Biophysics, School of Medicine, Virginia Commonwealth University, Richmond, VA, USA
| | - Tyler W E Steele
- Department of Physiology and Biophysics, School of Medicine, Virginia Commonwealth University, Richmond, VA, USA
| | - Jose M Eltit
- Department of Physiology and Biophysics, School of Medicine, Virginia Commonwealth University, Richmond, VA, USA.
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13
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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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14
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Velázquez-Marrero C, Custer EE, Marrero H, Ortiz-Miranda S, Lemos JR. Voltage-induced Ca 2+ release by ryanodine receptors causes neuropeptide secretion from nerve terminals. J Neuroendocrinol 2020; 32:e12840. [PMID: 32227430 DOI: 10.1111/jne.12840] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/14/2019] [Revised: 02/21/2020] [Accepted: 02/24/2020] [Indexed: 11/28/2022]
Abstract
Depolarisation-secretion coupling is assumed to be dependent only on extracellular calcium ([Ca2+ ]o ). Ryanodine receptor (RyR)-sensitive stores in hypothalamic neurohypophysial system (HNS) terminals produce sparks of intracellular calcium ([Ca2+ ]i ) that are voltage-dependent. We hypothesised that voltage-elicited increases in intraterminal calcium are crucial for neuropeptide secretion from presynaptic terminals, whether from influx through voltage-gated calcium channels and/or from such voltage-sensitive ryanodine-mediated calcium stores. Increases in [Ca2+ ]i upon depolarisation in the presence of voltage-gated calcium channel blockers, or in the absence of [Ca2+ ]o , still give rise to neuropeptide secretion from HNS terminals. Even in 0 [Ca2+ ]o , there was nonetheless an increase in capacitance suggesting exocytosis upon depolarisation. This was blocked by antagonist concentrations of ryanodine, as was peptide secretion elicited by high K+ in 0 [Ca2+ ]o . Furthermore, such depolarisations lead to increases in [Ca2+ ]i . Pre-incubation with BAPTA-AM resulted in > 50% inhibition of peptide secretion elicited by high K+ in 0 [Ca2+ ]o . Nifedipine but not nicardipine inhibited both the high K+ response for neuropeptide secretion and intraterminal calcium, suggesting the involvement of CaV1.1 type channels as sensors in voltage-induced calcium release. Importantly, RyR antagonists also modulate neuropeptide release under normal physiological conditions. In conclusion, our results indicate that depolarisation-induced neuropeptide secretion is present in the absence of external calcium, and calcium release from ryanodine-sensitive internal stores is a significant physiological contributor to neuropeptide secretion from HNS terminals.
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Affiliation(s)
| | - Edward E Custer
- Departments of Microbiology and Physiological Systems, Neurobiology & Program in Neuroscience, University of Massachusetts Medical School, Worcester, MA, USA
| | - Héctor Marrero
- Institute of Neurobiology, University of Puerto Rico, San Juan, PR, USA
| | - Sonia Ortiz-Miranda
- Departments of Microbiology and Physiological Systems, Neurobiology & Program in Neuroscience, University of Massachusetts Medical School, Worcester, MA, USA
| | - José R Lemos
- Departments of Microbiology and Physiological Systems, Neurobiology & Program in Neuroscience, University of Massachusetts Medical School, Worcester, MA, USA
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15
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Parker R, Schiemann AH, Langton E, Bulger T, Pollock N, Bjorksten A, Gillies R, Hutchinson D, Roxburgh R, Stowell KM. Functional Characterization of C-terminal Ryanodine Receptor 1 Variants Associated with Central Core Disease or Malignant Hyperthermia. J Neuromuscul Dis 2019; 4:147-158. [PMID: 28527222 PMCID: PMC5467713 DOI: 10.3233/jnd-170210] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Background: Central core disease and malignant hyperthermia are human disorders of skeletal muscle resulting from aberrant Ca2+ handling. Most malignant hyperthermia and central core disease cases are associated with amino acid changes in the type 1 ryanodine receptor (RyR1), the skeletal muscle Ca2+-release channel. Malignant hyperthermia exhibits a gain-of-function phenotype, and central core disease results from loss of channel function. For a variant to be classified as pathogenic, functional studies must demonstrate a correlation with the pathophysiology of malignant hyperthermia or central core disease. Objective: We assessed the pathogenicity of four C-terminal variants of the ryanodine receptor using functional analysis. The variants were identified in families affected by either malignant hyperthermia or central core disease. Methods: Four variants were introduced separately into human cDNA encoding the skeletal muscle ryanodine receptor. Following transient expression in HEK-293T cells, functional studies were carried out using calcium release assays in response to an agonist. Two previously characterized variants and wild-type skeletal muscle ryanodine receptor were used as controls. Results: The p.Met4640Ile variant associated with central core disease showed no difference in calcium release compared to wild-type. The p.Val4849Ile variant associated with malignant hyperthermia was more sensitive to agonist than wild-type but did not reach statistical significance and two variants (p.Phe4857Ser and p.Asp4918Asn) associated with central core disease were completely inactive. Conclusions: The p.Val4849Ile variant should be considered a risk factor for malignant hyperthermia, while the p.Phe4857Ser and p.Asp4918Asn variants should be classified as pathogenic for central core disease.
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Affiliation(s)
- Remai Parker
- Institute of Fundamental Sciences, Massey University, Palmerston North, New Zealand
| | - Anja H Schiemann
- Institute of Fundamental Sciences, Massey University, Palmerston North, New Zealand
| | | | - Terasa Bulger
- Department of Anaesthesia and Intensive Care, Palmerston North Hospital, Palmerston North, New Zealand
| | - Neil Pollock
- Department of Anaesthesia and Intensive Care, Palmerston North Hospital, Palmerston North, New Zealand
| | - Andrew Bjorksten
- Department of Anaesthesia and Pain Management, Royal Melbourne Hospital, Melbourne
| | - Robyn Gillies
- Department of Anaesthesia and Pain Management, Royal Melbourne Hospital, Melbourne
| | - David Hutchinson
- Department of Neurology, Auckland City Hospital, Auckland, New Zealand
| | - Richard Roxburgh
- Department of Neurology, Auckland City Hospital, Auckland, New Zealand
| | - Kathryn M Stowell
- Institute of Fundamental Sciences, Massey University, Palmerston North, New Zealand
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16
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OKAMURA Y, OKOCHI Y. Molecular mechanisms of coupling to voltage sensors in voltage-evoked cellular signals. PROCEEDINGS OF THE JAPAN ACADEMY. SERIES B, PHYSICAL AND BIOLOGICAL SCIENCES 2019; 95:111-135. [PMID: 30853698 PMCID: PMC6541726 DOI: 10.2183/pjab.95.010] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/24/2018] [Accepted: 01/07/2019] [Indexed: 06/09/2023]
Abstract
The voltage sensor domain (VSD) has long been studied as a unique domain intrinsic to voltage-gated ion channels (VGICs). Within VGICs, the VSD is tightly coupled to the pore-gate domain (PGD) in diverse ways suitable for its specific function in each physiological context, including action potential generation, muscle contraction and relaxation, hormone and neurotransmitter secretion, and cardiac pacemaking. However, some VSD-containing proteins lack a PGD. Voltage-sensing phosphatase contains a cytoplasmic phosphoinositide phosphatase with similarity to phosphatase and tensin homolog (PTEN). Hv1, a voltage-gated proton channel, also lacks a PGD. Within Hv1, the VSD operates as a voltage sensor, gate, and pore for both proton sensing and permeation. Hv1 has a C-terminal coiled coil that mediates dimerization for cooperative gating. Recent progress in the structural biology of VGICs and VSD proteins provides insights into the principles of VSD coupling conserved among these proteins as well as the hierarchy of protein organization for voltage-evoked cell signaling.
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Affiliation(s)
- Yasushi OKAMURA
- Department of Physiology, Graduate School of Medicine, Osaka University, Suita, Japan
- Graduate School of Frontier Bioscience, Osaka University, Suita, Japan
| | - Yoshifumi OKOCHI
- Department of Physiology, Graduate School of Medicine, Osaka University, Suita, Japan
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17
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Franzini-Armstrong C. Can the Arrangement of RyR2 in Cardiac Muscle Be Predicted? Biophys J 2018; 110:2563-2565. [PMID: 27332114 DOI: 10.1016/j.bpj.2016.04.051] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2016] [Accepted: 04/22/2016] [Indexed: 11/17/2022] Open
Affiliation(s)
- Clara Franzini-Armstrong
- Department of Cell and Developmental Biology, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania.
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18
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Lainé J, Skoglund G, Fournier E, Tabti N. Development of the excitation-contraction coupling machinery and its relation to myofibrillogenesis in human iPSC-derived skeletal myocytes. Skelet Muscle 2018; 8:1. [PMID: 29304851 PMCID: PMC5756430 DOI: 10.1186/s13395-017-0147-5] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2017] [Accepted: 12/08/2017] [Indexed: 01/25/2023] Open
Abstract
Background Human induced pluripotent stem cells-derived myogenic progenitors develop functional and ultrastructural features typical of skeletal muscle when differentiated in culture. Besides disease-modeling, such a system can be used to clarify basic aspects of human skeletal muscle development. In the present study, we focus on the development of the excitation-contraction (E-C) coupling, a process that is essential both in muscle physiology and as a tool to differentiate between the skeletal and cardiac muscle. The occurrence and maturation of E-C coupling structures (Sarcoplasmic Reticulum-Transverse Tubule (SR-TT) junctions), key molecular components, and Ca2+ signaling were examined, along with myofibrillogenesis. Methods Pax7+-myogenic progenitors were differentiated in culture, and developmental changes were examined from a few days up to several weeks. Ion channels directly involved in the skeletal muscle E-C coupling (RyR1 and Cav1.1 voltage-gated Ca2+ channels) were labeled using indirect immunofluorescence. Ultrastructural changes of differentiating cells were visualized by transmission electron microscopy. On the functional side, depolarization-induced intracellular Ca2+ transients mediating E-C coupling were recorded using Fura-2 ratiometric Ca2+ imaging, and myocyte contraction was captured by digital photomicrography. Results We show that the E-C coupling machinery occurs and operates within a few days post-differentiation, as soon as the myofilaments align. However, Ca2+ transients become effective in triggering myocyte contraction after 1 week of differentiation, when nascent myofibrils show alternate A-I bands. At later stages, myofibrils become fully organized into adult-like sarcomeres but SR-TT junctions do not reach their triadic structure and typical A-I location. This is mirrored by the absence of cross-striated distribution pattern of both RyR1 and Cav1.1 channels. Conclusions The E-C coupling machinery occurs and operates within the first week of muscle cells differentiation. However, while early development of SR-TT junctions is coordinated with that of nascent myofibrils, their respective maturation is not. Formation of typical triads requires other factors/conditions, and this should be taken into account when using in-vitro models to explore skeletal muscle diseases, especially those affecting E-C coupling. Electronic supplementary material The online version of this article (10.1186/s13395-017-0147-5) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Jeanne Lainé
- Département de Physiologie, Faculté de Médecine Pierre & Marie Curie site Pitié-Salpêtrière, UPMC, 91, Bd de l'Hôpital, 75013, Paris, France
| | - Gunnar Skoglund
- Département de Physiologie, Faculté de Médecine Pierre & Marie Curie site Pitié-Salpêtrière, UPMC, 91, Bd de l'Hôpital, 75013, Paris, France
| | - Emmanuel Fournier
- Département de Physiologie, Faculté de Médecine Pierre & Marie Curie site Pitié-Salpêtrière, UPMC, 91, Bd de l'Hôpital, 75013, Paris, France
| | - Nacira Tabti
- Département de Physiologie, Faculté de Médecine Pierre & Marie Curie site Pitié-Salpêtrière, UPMC, 91, Bd de l'Hôpital, 75013, Paris, France. .,UPEC, Créteil, France.
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19
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Polster A, Perni S, Filipova D, Moua O, Ohrtman JD, Bichraoui H, Beam KG, Papadopoulos S. Junctional trafficking and restoration of retrograde signaling by the cytoplasmic RyR1 domain. J Gen Physiol 2017; 150:293-306. [PMID: 29284662 PMCID: PMC5806685 DOI: 10.1085/jgp.201711879] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2017] [Accepted: 12/07/2017] [Indexed: 11/20/2022] Open
Abstract
The type 1 ryanodine receptor (RyR1) in skeletal muscle is a homotetrameric protein that releases Ca2+ from the sarcoplasmic reticulum (SR) in response to an "orthograde" signal from the dihydropyridine receptor (DHPR) in the plasma membrane (PM). Additionally, a "retrograde" signal from RyR1 increases the amplitude of the Ca2+ current produced by CaV1.1, the principle subunit of the DHPR. This bidirectional signaling is thought to depend on physical links, of unknown identity, between the DHPR and RyR1. Here, we investigate whether the isolated cytoplasmic domain of RyR1 can interact structurally or functionally with CaV1.1 by producing an N-terminal construct (RyR11:4300) that lacks the C-terminal membrane domain. In CaV1.1-null (dysgenic) myotubes, RyR11:4300 is diffusely distributed, but in RyR1-null (dyspedic) myotubes it localizes in puncta at SR-PM junctions containing endogenous CaV1.1. Fluorescence recovery after photobleaching indicates that diffuse RyR11:4300 is mobile, whereas resistance to being washed out with a large-bore micropipette indicates that the punctate RyR11:4300 stably associates with PM-SR junctions. Strikingly, expression of RyR11:4300 in dyspedic myotubes causes an increased amplitude, and slowed activation, of Ca2+ current through CaV1.1, which is almost identical to the effects of full-length RyR1. Fast protein liquid chromatography indicates that ∼25% of RyR11:4300 in diluted cytosolic lysate of transfected tsA201 cells is present in complexes larger in size than the monomer, and intermolecular fluorescence resonance energy transfer implies that RyR11:4300 is significantly oligomerized within intact tsA201 cells and dyspedic myotubes. A large fraction of these oligomers may be homotetramers because freeze-fracture electron micrographs reveal that the frequency of particles arranged like DHPR tetrads is substantially increased by transfecting RyR-null myotubes with RyR11:4300 In summary, the RyR1 cytoplasmic domain, separated from its SR membrane anchor, retains a tendency toward oligomerization/tetramerization, binds to SR-PM junctions in myotubes only if CaV1.1 is also present and is fully functional in retrograde signaling to CaV1.1.
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Affiliation(s)
- Alexander Polster
- Department of Physiology and Biophysics, University of Colorado Denver Anschutz Medical Campus, Denver, CO
| | - Stefano Perni
- Department of Physiology and Biophysics, University of Colorado Denver Anschutz Medical Campus, Denver, CO
| | - Dilyana Filipova
- Institute of Vegetative Physiology, University Hospital of Cologne, Cologne, Germany
| | - Ong Moua
- Department of Physiology and Biophysics, University of Colorado Denver Anschutz Medical Campus, Denver, CO
| | - Joshua D Ohrtman
- Department of Physiology and Biophysics, University of Colorado Denver Anschutz Medical Campus, Denver, CO
| | - Hicham Bichraoui
- Department of Physiology and Biophysics, University of Colorado Denver Anschutz Medical Campus, Denver, CO
| | - Kurt G Beam
- Department of Physiology and Biophysics, University of Colorado Denver Anschutz Medical Campus, Denver, CO
| | - Symeon Papadopoulos
- Institute of Vegetative Physiology, University Hospital of Cologne, Cologne, Germany
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20
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De novo reconstitution reveals the proteins required for skeletal muscle voltage-induced Ca 2+ release. Proc Natl Acad Sci U S A 2017; 114:13822-13827. [PMID: 29229815 DOI: 10.1073/pnas.1716461115] [Citation(s) in RCA: 56] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Skeletal muscle contraction is triggered by Ca2+ release from the sarcoplasmic reticulum (SR) in response to plasma membrane (PM) excitation. In vertebrates, this depends on activation of the RyR1 Ca2+ pore in the SR, under control of conformational changes of CaV1.1, located ∼12 nm away in the PM. Over the last ∼30 y, gene knockouts have revealed that CaV1.1/RyR1 coupling requires additional proteins, but leave open the possibility that currently untested proteins are also necessary. Here, we demonstrate the reconstitution of conformational coupling in tsA201 cells by expression of CaV1.1, β1a, Stac3, RyR1, and junctophilin2. As in muscle, depolarization evokes Ca2+ transients independent of external Ca2+ entry and having amplitude with a saturating dependence on voltage. Moreover, freeze-fracture electron microscopy indicates that the five identified proteins are sufficient to establish physical links between CaV1.1 and RyR1. Thus, these proteins constitute the key elements essential for excitation-contraction coupling in skeletal muscle.
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21
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Cabra V, Murayama T, Samsó M. Ultrastructural Analysis of Self-Associated RyR2s. Biophys J 2017; 110:2651-2662. [PMID: 27332123 DOI: 10.1016/j.bpj.2016.05.013] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2016] [Revised: 04/28/2016] [Accepted: 05/09/2016] [Indexed: 10/21/2022] Open
Abstract
In heart, type-2 ryanodine receptor (RyR2) forms discrete supramolecular clusters in the sarcoplasmic reticulum known as calcium release units (CRUs), which are responsible for most of the Ca(2+) released for muscle contraction. To learn about the substructure of the CRU, we sought to determine whether RyR2s have the ability to self-associate in the absence of other factors and if so, whether they do it in a specific manner. Purified RyR2 was negatively stained and imaged on the transmission electron microscope, and RyR2 particles closely associated were further analyzed using bias-free multivariate statistical analysis and classification. The resulting two-dimensional averages show that RyR2s can interact in two rigid, reproducible configurations: "adjoining", with two RyR2s alongside each other, and "oblique", with two partially overlapped RyR2s forming an angle of 12°. The two configurations are nearly identical under two extreme physiological Ca(2+) concentrations. Pseudo-atomic models for these two interactions indicate that the adjoining interaction involves contacts between the P1, SPRY1 and the helical domains. The oblique interaction is mediated by extensive contacts between the SPRY1 domains (domains 9) and P1 domains (domains 10) of both RyR2s and not through domain 6 as previously thought; in addition its asymmetric interface imposes steric constrains that inhibit the growth of RyR2 as a checkerboard, which is the configuration usually assumed, and generates new configurations, i.e., "branched" and "interlocked". This first, to our knowledge, structural detailed analysis of the inter-RyR2 interactions helps to understand important morphological and functional aspects of the CRU in the context of cardiac EC coupling.
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Affiliation(s)
- Vanessa Cabra
- Department of Physiology and Biophysics, Virginia Commonwealth University, Richmond, Virginia
| | - Takashi Murayama
- Department of Pharmacology, Juntendo University School of Medicine, Tokyo, Japan
| | - Montserrat Samsó
- Department of Physiology and Biophysics, Virginia Commonwealth University, Richmond, Virginia.
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22
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Dhindwal S, Lobo J, Cabra V, Santiago DJ, Nayak AR, Dryden K, Samsó M. A cryo-EM–based model of phosphorylation- and FKBP12.6-mediated allosterism of the cardiac ryanodine receptor. Sci Signal 2017; 10:10/480/eaai8842. [DOI: 10.1126/scisignal.aai8842] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
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23
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Samsó M. A guide to the 3D structure of the ryanodine receptor type 1 by cryoEM. Protein Sci 2016; 26:52-68. [PMID: 27671094 DOI: 10.1002/pro.3052] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2016] [Revised: 09/21/2016] [Accepted: 09/22/2016] [Indexed: 01/04/2023]
Abstract
Signal transduction by the ryanodine receptor (RyR) is essential in many excitable cells including all striated contractile cells and some types of neurons. While its transmembrane domain is a classic tetrameric, six-transmembrane cation channel, the cytoplasmic domain is uniquely large and complex, hosting a multiplicity of specialized domains. The overall outline and substructure readily recognizable by electron microscopy make RyR a geometrically well-behaved specimen. Hence, for the last two decades, the 3D structural study of the RyR has tracked closely the technological advances in electron microscopy, cryo-electron microscopy (cryoEM), and computerized 3D reconstruction. This review summarizes the progress in the structural determination of RyR by cryoEM and, bearing in mind the leap in resolution provided by the recent implementation of direct electron detection, analyzes the first near-atomic structures of RyR. These reveal a complex orchestration of domains controlling the channel's function, and help to understand how this could break down as a consequence of disease-causing mutations.
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Affiliation(s)
- Montserrat Samsó
- Department of Physiology and Biophysics, Virginia Commonwealth University, Richmond, Virginia
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24
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Carlo C, Pura B, Magaly R, Marino D. Differential effects of contractile potentiators on action potential-induced Ca 2+ transients of frog and mouse skeletal muscle fibres. J Muscle Res Cell Motil 2016; 37:169-180. [PMID: 27590123 DOI: 10.1007/s10974-016-9455-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2016] [Accepted: 08/22/2016] [Indexed: 10/21/2022]
Abstract
Muscle fibres, isolated from frog tibialis anterior and mouse flexor digitorum brevis (FDB) were loaded with the fast dye MagFluo-4 to study the effects of potentiators caffeine, nitrate, Zn2+ and perchlorate on Ca2+ transients elicited by single action potentials. Overall, the potentiators doubled the transients amplitude and prolonged by about 1.5-fold their decay time. In contrast, as shown here for the first time, nitrate and Zn2+, but not caffeine, activated a late, secondary component of the transient rising phase of frog but not mouse, fibres. The rise time was increased from 1.9 ms in normal solution (NR) to 3.3 ms (nitrate) and 4.4 ms (Zn2+). In NR, a single exponential, fitted the rising phase of calcium transients of frog (τ1 = 0.47 ms) and mouse (τ1 = 0.28 ms). In nitrate and Zn2+ only frog transients showed a secondary exponential component, τ2 = 0.72 ms (nitrate) and 0.94 ms, (Zn2+). We suggest that nitrate and Zn2+ activate a late slower component of the ΔF/F signals of frog but not of mouse fibres, possibly promoting Ca2+ induced Ca2+ release at level of the RyR3, that in frog muscle fibres are localized in the para-junctional region of the triads and are absent in mouse FDB muscle fibres.
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Affiliation(s)
- Caputo Carlo
- Laboratorio de Fisiología Celular, Centro de Biofísica y Bioquímica, Instituto Venezolano de Investigaciones Científicas, IVIC, Apartado 21827, Caracas, 1020, Venezuela.
| | - Bolaños Pura
- Laboratorio de Fisiología Celular, Centro de Biofísica y Bioquímica, Instituto Venezolano de Investigaciones Científicas, IVIC, Apartado 21827, Caracas, 1020, Venezuela
| | - Ramos Magaly
- Laboratorio de Fisiología Celular, Centro de Biofísica y Bioquímica, Instituto Venezolano de Investigaciones Científicas, IVIC, Apartado 21827, Caracas, 1020, Venezuela
| | - DiFranco Marino
- Department of Physiology, David Geffen School of Medicine, UCLA, Los Angeles, CF, USA
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25
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Wei R, Wang X, Zhang Y, Mukherjee S, Zhang L, Chen Q, Huang X, Jing S, Liu C, Li S, Wang G, Xu Y, Zhu S, Williams AJ, Sun F, Yin CC. Structural insights into Ca(2+)-activated long-range allosteric channel gating of RyR1. Cell Res 2016; 26:977-94. [PMID: 27573175 PMCID: PMC5034117 DOI: 10.1038/cr.2016.99] [Citation(s) in RCA: 74] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2016] [Revised: 07/31/2016] [Accepted: 08/03/2016] [Indexed: 12/12/2022] Open
Abstract
Ryanodine receptors (RyRs) are a class of giant ion channels with molecular mass over 2.2 mega-Daltons. These channels mediate calcium signaling in a variety of cells. Since more than 80% of the RyR protein is folded into the cytoplasmic assembly and the remaining residues form the transmembrane domain, it has been hypothesized that the activation and regulation of RyR channels occur through an as yet uncharacterized long-range allosteric mechanism. Here we report the characterization of a Ca2+-activated open-state RyR1 structure by cryo-electron microscopy. The structure has an overall resolution of 4.9 Å and a resolution of 4.2 Å for the core region. In comparison with the previously determined apo/closed-state structure, we observed long-range allosteric gating of the channel upon Ca2+ activation. In-depth structural analyses elucidated a novel channel-gating mechanism and a novel ion selectivity mechanism of RyR1. Our work not only provides structural insights into the molecular mechanisms of channel gating and regulation of RyRs, but also sheds light on structural basis for channel-gating and ion selectivity mechanisms for the six-transmembrane-helix cation channel family.
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Affiliation(s)
- Risheng Wei
- Department of Biophysics, The Health Science Center, Peking University, Beijing 100191, China
| | - Xue Wang
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China.,College of Life Science, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yan Zhang
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
| | - Saptarshi Mukherjee
- Wales Heart Research Institute, Cardiff University School of Medicine, Cardiff CF14 4XN, UK
| | - Lei Zhang
- Department of Biophysics, The Health Science Center, Peking University, Beijing 100191, China.,Electron Microscopy Analysis Laboratory, The Health Science Center, Peking University, Beijing 100191, China
| | - Qiang Chen
- Department of Biophysics, The Health Science Center, Peking University, Beijing 100191, China
| | - Xinrui Huang
- Department of Biophysics, The Health Science Center, Peking University, Beijing 100191, China
| | - Shan Jing
- Department of Biophysics, The Health Science Center, Peking University, Beijing 100191, China
| | - Congcong Liu
- Department of Biophysics, The Health Science Center, Peking University, Beijing 100191, China
| | - Shuang Li
- Department of Biophysics, The Health Science Center, Peking University, Beijing 100191, China
| | - Guangyu Wang
- Department of Biophysics, The Health Science Center, Peking University, Beijing 100191, China
| | - Yaofang Xu
- Department of Biophysics, The Health Science Center, Peking University, Beijing 100191, China
| | - Sujie Zhu
- Department of Biophysics, The Health Science Center, Peking University, Beijing 100191, China
| | - Alan J Williams
- Wales Heart Research Institute, Cardiff University School of Medicine, Cardiff CF14 4XN, UK
| | - Fei Sun
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China.,College of Life Science, University of Chinese Academy of Sciences, Beijing 100049, China.,Center for Biological Imaging, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
| | - Chang-Cheng Yin
- Department of Biophysics, The Health Science Center, Peking University, Beijing 100191, China.,Electron Microscopy Analysis Laboratory, The Health Science Center, Peking University, Beijing 100191, China.,Center for Protein Science, Peking University, Beijing 100871, China
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Clarke OB, Hendrickson WA. Structures of the colossal RyR1 calcium release channel. Curr Opin Struct Biol 2016; 39:144-152. [PMID: 27687475 PMCID: PMC5419430 DOI: 10.1016/j.sbi.2016.09.002] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2016] [Accepted: 09/05/2016] [Indexed: 01/19/2023]
Abstract
Ryanodine receptors (RyRs) are intracellular cation channels that mediate the rapid and voluminous release of Ca2+ from the sarcoplasmic reticulum (SR) as required for excitation-contraction coupling in cardiac and skeletal muscle. Understanding of the architecture and gating of RyRs has advanced dramatically over the past two years, due to the publication of high resolution cryo-electron microscopy (cryoEM) reconstructions and associated atomic models of multiple functional states of the skeletal muscle receptor, RyR1. Here we review recent advances in our understanding of RyR architecture and gating, and highlight remaining gaps in understanding which we anticipate will soon be filled.
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Affiliation(s)
- Oliver B Clarke
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA
| | - Wayne A Hendrickson
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA.
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27
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Intensity matters: Ryanodine receptor regulation during exercise. Proc Natl Acad Sci U S A 2015; 112:15271-2. [PMID: 26631747 DOI: 10.1073/pnas.1521051112] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
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28
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Zalk R, Clarke OB, des Georges A, Grassucci RA, Reiken S, Mancia F, Hendrickson WA, Frank J, Marks AR. Structure of a mammalian ryanodine receptor. Nature 2014; 517:44-9. [PMID: 25470061 PMCID: PMC4300236 DOI: 10.1038/nature13950] [Citation(s) in RCA: 290] [Impact Index Per Article: 29.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2014] [Accepted: 10/08/2014] [Indexed: 12/11/2022]
Abstract
Ryanodine receptors (RyRs) mediate rapid release of calcium (Ca2+) from intracellular stores into the cytosol, which is essential for numerous cellular functions including excitation-contraction coupling in muscle. Lack of sufficient structural detail has impeded understanding of RyR gating and regulation. Here, we report the closed-state structure of the 2.3 MDa complex of the rabbit skeletal muscle type 1 RyR (RyR1), solved by single-particle cryo-electron microscopy at an overall resolution of 4.8 Å. We fitted a polyalanine-level model to all 3939 ordered residues in each protomer, defining the transmembrane pore in unprecedented detail and placing all cytosolic domains as tertiary folds. The cytosolic assembly is built on an extended α-solenoid scaffold connecting key regulatory domains to the pore. The RyR1 pore architecture places it in the six-transmembrane (6TM) ion channel superfamily. A unique domain inserted between the second and third transmembrane helices interacts intimately with paired EF-hands originating from the α-solenoid scaffold, suggesting a mechanism for channel gating by Ca2+.
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Affiliation(s)
- Ran Zalk
- Department of Physiology and Cellular Biophysics, Columbia University, New York, New York 10032, USA
| | - Oliver B Clarke
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, New York 10032, USA
| | - Amédée des Georges
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, New York 10032, USA
| | - Robert A Grassucci
- 1] Department of Biochemistry and Molecular Biophysics, Columbia University, New York, New York 10032, USA [2] Howard Hughes Medical Institute, Columbia University, New York, New York 10032, USA
| | - Steven Reiken
- Department of Physiology and Cellular Biophysics, Columbia University, New York, New York 10032, USA
| | - Filippo Mancia
- Department of Physiology and Cellular Biophysics, Columbia University, New York, New York 10032, USA
| | - Wayne A Hendrickson
- 1] Department of Physiology and Cellular Biophysics, Columbia University, New York, New York 10032, USA [2] Department of Biochemistry and Molecular Biophysics, Columbia University, New York, New York 10032, USA
| | - Joachim Frank
- 1] Department of Biochemistry and Molecular Biophysics, Columbia University, New York, New York 10032, USA [2] Howard Hughes Medical Institute, Columbia University, New York, New York 10032, USA [3] Department of Biological Sciences, Columbia University, New York, New York 10027, USA
| | - Andrew R Marks
- 1] Department of Physiology and Cellular Biophysics, Columbia University, New York, New York 10032, USA [2] Department of Medicine, Columbia University, New York, New York 10032, USA [3] Wu Center for Molecular Cardiology, College of Physicians and Surgeons of Columbia University, New York, New York 10032, USA
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29
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Eltit JM, Franzini-Armstrong C, Perez CF. Amino acid residues 489-503 of dihydropyridine receptor (DHPR) β1a subunit are critical for structural communication between the skeletal muscle DHPR complex and type 1 ryanodine receptor. J Biol Chem 2014; 289:36116-24. [PMID: 25384984 DOI: 10.1074/jbc.m114.615526] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The β1a subunit is a cytoplasmic component of the dihydropyridine receptor (DHPR) complex that plays an essential role in skeletal muscle excitation-contraction (EC) coupling. Here we investigate the role of the C-terminal end of this auxiliary subunit in the functional and structural communication between the DHPR and the Ca(2+) release channel (RyR1). Progressive truncation of the β1a C terminus showed that deletion of amino acid residues Gln(489) to Trp(503) resulted in a loss of depolarization-induced Ca(2+) release, a severe reduction of L-type Ca(2+) currents, and a lack of tetrad formation as evaluated by freeze-fracture analysis. However, deletion of this domain did not affect expression/targeting or density (Qmax) of the DHPR-α1S subunit to the plasma membrane. Within this motif, triple alanine substitution of residues Leu(496), Leu(500), and Trp(503), which are thought to mediate direct β1a-RyR1 interactions, weakened EC coupling but did not replicate the truncated phenotype. Therefore, these data demonstrate that an amino acid segment encompassing sequence (489)QVQVLTSLRRNLSFW(503) of β1a contains critical determinant(s) for the physical link of DHPR and RyR1, further confirming a direct correspondence between DHPR positioning and DHPR/RyR functional interactions. In addition, our data strongly suggest that the motif Leu(496)-Leu(500)-Trp(503) within the β1a C-terminal tail plays a nonessential role in the bidirectional DHPR/RyR1 signaling that supports skeletal-type EC coupling.
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Affiliation(s)
- Jose M Eltit
- the Department of Physiology and Biophysics, School of Medicine, Virginia Commonwealth University, Richmond, Virgina 23298, and
| | - Clara Franzini-Armstrong
- the Department of Cell and Developmental Biology, University of Pennsylvania, Philadelphia, Pennsylvania 19104
| | - Claudio F Perez
- From the Department of Anesthesiology Perioperative and Pain Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts 02115,
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30
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Ruchala I, Cabra V, Solis E, Glennon RA, De Felice LJ, Eltit JM. Electrical coupling between the human serotonin transporter and voltage-gated Ca(2+) channels. Cell Calcium 2014; 56:25-33. [PMID: 24854234 DOI: 10.1016/j.ceca.2014.04.003] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2014] [Revised: 04/18/2014] [Accepted: 04/19/2014] [Indexed: 10/25/2022]
Abstract
Monoamine transporters have been implicated in dopamine or serotonin release in response to abused drugs such as methamphetamine or ecstasy (MDMA). In addition, monoamine transporters show substrate-induced inward currents that may modulate excitability and Ca(2+) mobilization, which could also contribute to neurotransmitter release. How monoamine transporters modulate Ca(2+) permeability is currently unknown. We investigate the functional interaction between the human serotonin transporter (hSERT) and voltage-gated Ca(2+) channels (CaV). We introduce an excitable expression system consisting of cultured muscle cells genetically engineered to express hSERT. Both 5HT and S(+)MDMA depolarize these cells and activate the excitation-contraction (EC)-coupling mechanism. However, hSERT substrates fail to activate EC-coupling in CaV1.1-null muscle cells, thus implicating Ca(2+) channels. CaV1.3 and CaV2.2 channels are natively expressed in neurons. When these channels are co-expressed with hSERT in HEK293T cells, only cells expressing the lower-threshold L-type CaV1.3 channel show Ca(2+) transients evoked by 5HT or S(+)MDMA. In addition, the electrical coupling between hSERT and CaV1.3 takes place at physiological 5HT concentrations. The electrical coupling between monoamine neurotransmitter transporters and Ca(2+) channels such as CaV1.3 is a novel mechanism by which endogenous substrates (neurotransmitters) or exogenous substrates (like ecstasy) could modulate Ca(2+)-driven signals in excitable cells.
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Affiliation(s)
- Iwona Ruchala
- Department of Physiology and Biophysics, School of Medicine, Virginia Commonwealth University, Richmond, VA 23298, United States
| | - Vanessa Cabra
- Department of Physiology and Biophysics, School of Medicine, Virginia Commonwealth University, Richmond, VA 23298, United States
| | - Ernesto Solis
- Department of Physiology and Biophysics, School of Medicine, Virginia Commonwealth University, Richmond, VA 23298, United States
| | - Richard A Glennon
- Department of Medicinal Chemistry, School of Pharmacy, Virginia Commonwealth University, Richmond, VA 23298, United States
| | - Louis J De Felice
- Department of Physiology and Biophysics, School of Medicine, Virginia Commonwealth University, Richmond, VA 23298, United States
| | - Jose M Eltit
- Department of Physiology and Biophysics, School of Medicine, Virginia Commonwealth University, Richmond, VA 23298, United States.
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31
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The α2δ subunits of voltage-gated calcium channels. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2013. [DOI: 10.1016/j.bbamem.2012.11.019] [Citation(s) in RCA: 155] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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32
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Hollingworth S, Baylor SM. Comparison of myoplasmic calcium movements during excitation-contraction coupling in frog twitch and mouse fast-twitch muscle fibers. J Gen Physiol 2013; 141:567-83. [PMID: 23630340 PMCID: PMC3639574 DOI: 10.1085/jgp.201310961] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2013] [Accepted: 03/25/2013] [Indexed: 01/26/2023] Open
Abstract
Single twitch fibers from frog leg muscles were isolated by dissection and micro-injected with furaptra, a rapidly responding fluorescent Ca(2+) indicator. Indicator resting fluorescence (FR) and the change evoked by an action potential (ΔF) were measured at long sarcomere length (16°C); ΔF/FR was scaled to units of ΔfCaD, the change in fraction of the indicator in the Ca(2+)-bound form. ΔfCaD was simulated with a multicompartment model of the underlying myoplasmic Ca(2+) movements, and the results were compared with previous measurements and analyses in mouse fast-twitch fibers. In frog fibers, sarcoplasmic reticulum (SR) Ca(2+) release evoked by an action potential appears to be the sum of two components. The time course of the first component is similar to that of the entire Ca(2+) release waveform in mouse fibers, whereas that of the second component is severalfold slower; the fractional release amounts are ~0.8 (first component) and ~0.2 (second component). Similar results were obtained in frog simulations with a modified model that permitted competition between Mg(2+) and Ca(2+) for occupancy of the regulatory sites on troponin. An anatomical basis for two release components in frog fibers is the presence of both junctional and parajunctional SR Ca(2+) release channels (ryanodine receptors [RyRs]), whereas mouse fibers (usually) have only junctional RyRs. Also, frog fibers have two RyR isoforms, RyRα and RyRβ, whereas the mouse fibers (usually) have only one, RyR1. Our simulations suggest that the second release component in frog fibers functions to supply extra Ca(2+) to activate troponin, which, in mouse fibers, is not needed because of the more favorable location of their triadic junctions (near the middle of the thin filament). We speculate that, in general, parajunctional RyRs permit increased myofilament activation in fibers whose triadic junctions are located at the z-line.
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Affiliation(s)
- Stephen Hollingworth
- Department of Physiology, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA
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33
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Tian X, Liu Y, Liu Y, Wang R, Wagenknecht T, Liu Z, Chen SRW. Ligand-dependent conformational changes in the clamp region of the cardiac ryanodine receptor. J Biol Chem 2012; 288:4066-75. [PMID: 23258540 DOI: 10.1074/jbc.m112.427864] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Global conformational changes in the three-dimensional structure of the Ca(2+) release channel/ryanodine receptor (RyR) occur upon ligand activation. A number of ligands are able to activate the RyR channel, but whether these structurally diverse ligands induce the same or different conformational changes in the channel is largely unknown. Here we constructed a fluorescence resonance energy transfer (FRET)-based probe by inserting a CFP after residue Ser-2367 and a YFP after residue Tyr-2801 in the cardiac RyR (RyR2) to yield a CFP- and YFP-dual labeled RyR2 (RyR2(Ser-2367-CFP/Tyr-2801-YFP)). Both of these insertion sites have previously been mapped to the "clamp" region in the four corners of the square-shaped cytoplasmic assembly of the three-dimensional structure of RyR2. Using this novel FRET probe, we monitored the extent of conformational changes in the clamp region of RyR2(Ser-2367-CFP/Tyr-2801-YFP) induced by various ligands. We also monitored the extent of Ca(2+) release induced by the same ligands in HEK293 cells expressing RyR2(Ser-2367-CFP/Tyr-2801-YFP). We detected conformational changes in the clamp region for the ligands caffeine, aminophylline, theophylline, ATP, and ryanodine but not for Ca(2+) or 4-chloro-m-cresol, although they all induced Ca(2+) release. Interestingly, caffeine is able to induce further conformational changes in the clamp region of the ryanodine-modified channel, suggesting that ryanodine does not lock RyR in a fixed conformation. Our data demonstrate that conformational changes in the clamp region of RyR are ligand-dependent and suggest the existence of multiple ligand dependent RyR activation mechanisms associated with distinct conformational changes.
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Affiliation(s)
- Xixi Tian
- Libin Cardiovascular Institute of Alberta, Department of Physiology and Pharmacology and Department of Biochemistry and Molecular Biology, University of Calgary, Calgary, Alberta T2N 4N1, Canada
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Dantrolene-induced inhibition of skeletal L-type Ca2+ current requires RyR1 expression. BIOMED RESEARCH INTERNATIONAL 2012; 2013:390493. [PMID: 23509717 PMCID: PMC3591246 DOI: 10.1155/2013/390493] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/20/2012] [Revised: 06/06/2012] [Accepted: 06/06/2012] [Indexed: 11/23/2022]
Abstract
Malignant hyperthermia (MH) is a pharmacogenetic disorder most often linked to mutations in the type 1 ryanodine receptor (RyR1) or the skeletal L-type Ca2+ channel (CaV1.1). The only effective treatment for an MH crisis is administration of the hydantoin derivative Dantrolene. In addition to reducing voltage induced Ca2+ release from the sarcoplasmic reticulum, Dantrolene was recently found to inhibit L-type currents in developing myotubes by shifting the voltage-dependence of CaV1.1 channel activation to more depolarizing potentials. Thus, the purpose of this study was to obtain information regarding the mechanism of Dantrolene-induced inhibition of CaV1.1. A mechanism involving a general depression of plasma membrane excitability was excluded because the biophysical properties of skeletal muscle Na+ current in normal mouse myotubes were largely unaffected by exposure to Dantrolene. However, a role for RyR1 was evident as Dantrolene failed to alter the amplitude, voltage dependence and inactivation kinetics of L-type currents recorded from dyspedic (RyR1 null) myotubes. Taken together, these results suggest that the mechanism of Dantrolene-induced inhibition of the skeletal muscle L-type Ca2+ current is related to altered communication between CaV1.1 and RyR1.
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35
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Super-resolution imaging of EC coupling protein distribution in the heart. J Mol Cell Cardiol 2012; 58:32-40. [PMID: 23159441 DOI: 10.1016/j.yjmcc.2012.11.004] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/30/2012] [Revised: 11/05/2012] [Accepted: 11/05/2012] [Indexed: 11/20/2022]
Abstract
The cardiac ryanodine receptor (RyR) plays a central role in the control of contractile function of the heart. In cardiac ventricular myocytes RyRs and associated Ca(2+) handling proteins, including membrane Ca(2+) channels, Ca(2+) pumps and other sarcolemmal and sarcoplasmic reticulum proteins interact to set the time course and amplitude of the electrically triggered cytosolic Ca(2+) transient. It has become increasingly clear that protein distribution and clustering on the nanometer scale is critical in determining the interaction of these proteins and the resulting properties of cardiac Ca(2+) handling. Such intricate near-molecular scale detail cannot be visualized with conventional fluorescence microscopy techniques (e.g. confocal microscopy) but it has recently become accessible with optical super-resolution techniques. These techniques retain the advantages of fluorescent marker technology, i.e. high specificity and excellent contrast, but have a spatial resolution approaching 10nm, i.e. objects not much further apart than 10nm can be distinguished, previously only attainable with electron microscopy. We review the use of these novel imaging techniques for the study of protein distribution in cardiac ventricular myocytes and discuss technical considerations as well as recent findings using super-resolution imaging. An emphasis is on single molecule localization based super-resolution approaches and their use to reveal the complexity of RyR cluster morphology, placement and relationship to other excitation-contraction coupling proteins. Super-resolution imaging approaches have already demonstrated their utility for the study of cardiac structure-function relationships and we anticipate that their use will rapidly increase and help improve our understanding of cardiac Ca(2+) regulation.
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36
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Popova OB, Baker MR, Tran TP, Le T, Serysheva II. Identification of ATP-binding regions in the RyR1 Ca²⁺ release channel. PLoS One 2012; 7:e48725. [PMID: 23144945 PMCID: PMC3492408 DOI: 10.1371/journal.pone.0048725] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2012] [Accepted: 09/28/2012] [Indexed: 12/11/2022] Open
Abstract
ATP is an important modulator of gating in type 1 ryanodine receptor (RyR1), also known as a Ca2+ release channel in skeletal muscle cells. The activating effect of ATP on this channel is achieved by directly binding to one or more sites on the RyR1 protein. However, the number and location of these sites have yet to be determined. To identify the ATP-binding regions within RyR1 we used 2N3ATP-2′,3′-Biotin-LC-Hydrazone (BioATP-HDZ), a photo-reactive ATP analog to covalently label the channel. We found that BioATP-HDZ binds RyR1 specifically with an IC50 = 0.6±0.2 mM, comparable with the reported EC50 for activation of RyR1 with ATP. Controlled proteolysis of labeled RyR1 followed by sequence analysis revealed three fragments with apparent molecular masses of 95, 45 and 70 kDa that were crosslinked by BioATP-HDZ and identified as RyR1 sequences. Our analysis identified four glycine-rich consensus motifs that can potentially constitute ATP-binding sites and are located within the N-terminal 95-kDa fragment. These putative nucleotide-binding sequences include amino acids 699–704, 701–706, 1081–1084 and 1195–1200, which are conserved among the three RyR isoforms. Located next to the N-terminal disease hotspot region in RyR1, these sequences may communicate the effects of ATP-binding to channel function by tuning conformational motions within the neighboring cytoplasmic regulatory domains. Two other labeled fragments lack ATP-binding consensus motifs and may form non-canonical ATP-binding sites. Based on domain topology in the 3D structure of RyR1 it is also conceivable that the identified ATP-binding regions, despite their wide separation in the primary sequence, may actually constitute the same non-contiguous ATP-binding pocket within the channel tetramer.
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Affiliation(s)
- Olga B. Popova
- Department of Biochemistry and Molecular Biology, The University of Texas at Houston Medical School, Houston, Texas, United States of America
| | - Mariah R. Baker
- Department of Biochemistry and Molecular Biology, The University of Texas at Houston Medical School, Houston, Texas, United States of America
| | - Tina P. Tran
- Department of Biochemistry and Molecular Biology, The University of Texas at Houston Medical School, Houston, Texas, United States of America
| | - Tri Le
- Department of Biochemistry and Molecular Biology, The University of Texas at Houston Medical School, Houston, Texas, United States of America
| | - Irina I. Serysheva
- Department of Biochemistry and Molecular Biology, The University of Texas at Houston Medical School, Houston, Texas, United States of America
- * E-mail:
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37
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Szpyt J, Lorenzon N, Perez CF, Norris E, Allen PD, Beam KG, Samsó M. Three-dimensional localization of the α and β subunits and of the II-III loop in the skeletal muscle L-type Ca2+ channel. J Biol Chem 2012; 287:43853-61. [PMID: 23118233 DOI: 10.1074/jbc.m112.419283] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The L-type Ca(2+) channel (dihydropyridine receptor (DHPR) in skeletal muscle acts as the voltage sensor for excitation-contraction coupling. To better resolve the spatial organization of the DHPR subunits (α(1s) or Ca(V)1.1, α(2), β(1a), δ1, and γ), we created transgenic mice expressing a recombinant β(1a) subunit with YFP and a biotin acceptor domain attached to its N- and C- termini, respectively. DHPR complexes were purified from skeletal muscle, negatively stained, imaged by electron microscopy, and subjected to single-particle image analysis. The resulting 19.1-Å resolution, three-dimensional reconstruction shows a main body of 17 × 11 × 8 nm with five corners along its perimeter. Two protrusions emerge from either face of the main body: the larger one attributed to the α(2)-δ1 subunit that forms a flexible hook-shaped feature and a smaller protrusion on the opposite side that corresponds to the II-III loop of Ca(V)1.1 as revealed by antibody labeling. Novel features discernible in the electron density accommodate the atomic coordinates of a voltage-gated sodium channel and of the β subunit in a single docking possibility that defines the α1-β interaction. The β subunit appears more closely associated to the membrane than expected, which may better account for both its role in localizing the α(1s) subunit to the membrane and its suggested role in excitation-contraction coupling.
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Affiliation(s)
- John Szpyt
- Department of Anesthesia, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts 02115, USA
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38
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Liu D, Hewawasam R, Karunasekara Y, Casarotto MG, Dulhunty AF, Board PG. The inhibitory glutathione transferase M2-2 binding site is located in divergent region 3 of the cardiac ryanodine receptor. Biochem Pharmacol 2012; 83:1523-9. [PMID: 22406107 DOI: 10.1016/j.bcp.2012.02.020] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2011] [Revised: 02/19/2012] [Accepted: 02/21/2012] [Indexed: 10/28/2022]
Abstract
The muscle-specific glutathione transferase GSTM2-2 modulates the activity of ryanodine receptor (RyR) calcium release channels: it inhibits the activity of cardiac RyR (RyR2) channels with high affinity and activates skeletal RyR (RyR1) channels with low affinity. The C terminal domain of GSTM2-2 (GSTM2C) alone physically binds to RyR2 and inhibits its activity, but it does not bind to RyR1. We have now used yeast two-hybrid analysis, chemical cross-linking, intrinsic tryptophan fluorescence and Ca(2+) release studies to determine that the binding site for GSTM2C is in divergent region 3 (D3) of RyR2. The D3 region encompasses residues 1855-1890 in RyR2. Specific mutagenesis shows the binding primarily involves electrostatic interactions with residues K1875, K1886, R1887 and K1889, all residues that are present in RyR2, but not in RyR1. The significant sequence differences between the D3 regions of RyR2 and RyR1 explain why GSTM2-2 specifically inhibits RyR2. This specific inhibition of RyR2 could modulate Ca cycling and be useful for the treatment of heart failure. RyR2 inhibition during diastole may improve filling of the SR with Ca(2+) and improve contractility.
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Affiliation(s)
- Dan Liu
- John Curtin School of Medical Research, Australian National University, Canberra, Australia
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Boncompagni S, Protasi F, Franzini-Armstrong C. Sequential stages in the age-dependent gradual formation and accumulation of tubular aggregates in fast twitch muscle fibers: SERCA and calsequestrin involvement. AGE (DORDRECHT, NETHERLANDS) 2012; 34:27-41. [PMID: 21318331 PMCID: PMC3260353 DOI: 10.1007/s11357-011-9211-y] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/01/2010] [Accepted: 01/24/2011] [Indexed: 05/30/2023]
Abstract
Tubular aggregates (TAs), ordered arrays of elongated sarcoplasmic reticulum (SR) tubules, are present in skeletal muscle from patients with myopathies and are also experimentally induced by extreme anoxia. In wild-type mice TAs develop in a clear age-, sex- (male), and fiber type- (fast twitch) dependence. However, the events preceding the appearance of TAs have not been explored. We investigated the sequential stages leading to the initial appearance and maturation of TAs in EDL from male mice. TAs' formation requires two temporally distinct steps that operate via different mechanisms. Initially (before 1 year of age), the SR Ca(2+) binding protein calsequestrin (CASQ) accumulates specifically at the I band level causing swelling of free SR cisternae. In the second stage, the enlarged SR sacs at the I band level extend into multiple, longitudinally oriented tubules with a full complement of sarco(endo)plasmic reticulum Ca(2+) ATPases (SERCA) in the membrane and CASQ in the lumen. Tubules gradually acquire a regular cylindrical shape and uniform size apparently in concert with partial crystallization of SERCA. Multiple, small TAs associate to form fewer mature TAs of very large size. Interestingly, in fibers from CASQ1-knockout mice abnormal aggregates of SR tubules have different conformation and never develop into ordered aggregates of straight cylinders, possibly due to lack of CASQ accumulation. We conclude that TAs do not arise abruptly but are the final result of a gradually changing SR architecture and we suggest that the crystalline ATPase within the aggregates may be inactive.
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Affiliation(s)
- Simona Boncompagni
- IIM-Interuniversitary Institute of Myology, DNI-Department of Neuroscience and Imaging, CeSI-Centro Scienze dell'Invecchiamento, Università degli Studi G. d'Annunzio, 66013, Chieti, Italy.
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Perálvarez-Marín A, Tae H, Board PG, Casarotto MG, Dulhunty AF, Samsó M. 3D Mapping of the SPRY2 domain of ryanodine receptor 1 by single-particle cryo-EM. PLoS One 2011; 6:e25813. [PMID: 21998699 PMCID: PMC3187800 DOI: 10.1371/journal.pone.0025813] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2011] [Accepted: 09/11/2011] [Indexed: 01/26/2023] Open
Abstract
The type 1 skeletal muscle ryanodine receptor (RyR1) is principally responsible for Ca(2+) release from the sarcoplasmic reticulum and for the subsequent muscle contraction. The RyR1 contains three SPRY domains. SPRY domains are generally known to mediate protein-protein interactions, however the location of the three SPRY domains in the 3D structure of the RyR1 is not known. Combining immunolabeling and single-particle cryo-electron microscopy we have mapped the SPRY2 domain (S1085-V1208) in the 3D structure of RyR1 using three different antibodies against the SPRY2 domain. Two obstacles for the image processing procedure; limited amount of data and signal dilution introduced by the multiple orientations of the antibody bound in the tetrameric RyR1, were overcome by modifying the 3D reconstruction scheme. This approach enabled us to ascertain that the three antibodies bind to the same region, to obtain a 3D reconstruction of RyR1 with the antibody bound, and to map SPRY2 to the periphery of the cytoplasmic domain of RyR1. We report here the first 3D localization of a SPRY2 domain in any known RyR isoform.
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Affiliation(s)
- Alex Perálvarez-Marín
- Department of Anesthesia, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, United States of America
- Centre d'Estudis Biofísics, Universitat Autònoma de Barcelona, Barcelona, Spain
| | - HanShen Tae
- John Curtin School of Medical Research, Australian National University, Canberra, Australia
| | - Philip G. Board
- John Curtin School of Medical Research, Australian National University, Canberra, Australia
| | - Marco G. Casarotto
- John Curtin School of Medical Research, Australian National University, Canberra, Australia
| | - Angela F. Dulhunty
- John Curtin School of Medical Research, Australian National University, Canberra, Australia
| | - Montserrat Samsó
- Department of Anesthesia, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, United States of America
- Department of Physiology and Biophysics, Virginia Commonwealth University, Richmond, Virginia, United States of America
- * E-mail:
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Lee EH. Ca2+ channels and skeletal muscle diseases. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2010; 103:35-43. [DOI: 10.1016/j.pbiomolbio.2010.05.003] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/21/2009] [Revised: 03/09/2010] [Accepted: 05/19/2010] [Indexed: 11/29/2022]
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Wagenknecht TC, Liu Z. Electron microscopy of ryanodine receptors. CURRENT TOPICS IN MEMBRANES 2010; 66:27-47. [PMID: 22353475 DOI: 10.1016/s1063-5823(10)66002-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Affiliation(s)
- Terence C Wagenknecht
- Wadsworth Center, New York State Department of Health, Albany, New York, USA; Department of Biomedical Sciences, School of Public Health, State University of New York at Albany, Albany, New York, USA
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Grievink H, Stowell KM. Allele-specific differences in ryanodine receptor 1 mRNA expression levels may contribute to phenotypic variability in malignant hyperthermia. Orphanet J Rare Dis 2010; 5:10. [PMID: 20482855 PMCID: PMC2895584 DOI: 10.1186/1750-1172-5-10] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2010] [Accepted: 05/19/2010] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Malignant hyperthermia (MH) is a dominantly inherited skeletal muscle disorder that can cause a fatal hypermetabolic reaction to general anaesthetics. The primary locus of MH (MHS1 locus) in humans is linked to chromosome 19q13.1, the position of the gene encoding the ryanodine receptor skeletal muscle calcium release channel (RyR1). METHODS In this study, an inexpensive allele-specific PCR (AS-PCR) assay was designed that allowed the relative quantification of the two RyR1 transcripts in heterozygous samples found to be susceptible to MH (MHS). Allele-specific differences in RyR1 expression levels can provide insight into the observed variable penetrance and variations in MH phenotypes between individuals. The presence/absence of the H4833Y mutation in RYR1 transcripts was employed as a marker that allowed discrimination between the two alleles. RESULTS In four skeletal muscle samples and two lymphoblastoid cell lines (LCLs) from different MHS patients, the wild type allele was found to be expressed at higher levels than the mutant RyR1 allele. For both LCLs, the ratios between the wild type and mutant RYR1 alleles did not change after different incubation times with actinomycin D. This suggests that there are no allele-specific differences in RyR1 mRNA stability, at least in these cells. CONCLUSION The data presented here revealed for the first time allele-specific differences in RYR1 mRNA expression levels in heterozygous MHS samples, and can at least in part contribute to the observed variable penetrance and variations in MH clinical phenotypes.
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Affiliation(s)
- Hilbert Grievink
- Institute of Molecular BioSciences, Massey University, Private Bag 11-222, Palmerston North, New Zealand
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Cárdenas C, Escobar M, García A, Osorio-Reich M, Härtel S, Foskett JK, Franzini-Armstrong C. Visualization of inositol 1,4,5-trisphosphate receptors on the nuclear envelope outer membrane by freeze-drying and rotary shadowing for electron microscopy. J Struct Biol 2010; 171:372-81. [PMID: 20457258 DOI: 10.1016/j.jsb.2010.05.003] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2010] [Accepted: 05/04/2010] [Indexed: 01/27/2023]
Abstract
The receptors for the second messenger InsP(3) comprise a family of closely related ion channels that release Ca(2+) from intracellular stores, most prominently the endoplasmic reticulum and its extension into the nuclear envelope. The precise sub-cellular localization of InsP(3)Rs and the spatial relationships among them are important for the initiation, spatial and temporal properties and propagation of local and global Ca(2+) signals, but the spatial organization of InsP(3)Rs in Ca(2+) stores is poorly characterized. Using nuclei isolated from insect Sf9 cells and freeze-dry rotary shadowing, we have addressed this by directly visualizing the cytoplasmic domain of InsP(3)R located on the cytoplasmic side of the nuclear envelope. Identification of approximately 15 nm structures as the cytoplasmic domain of InsP(3)R was indirectly supported by a marked increase in their frequency after transient transfections with cDNAs for rat types 1 and 3 InsP(3)R, and directly confirmed by gold labeling either with heparin or a specific anti-InsP(3)R antibody. Over-expression of InsP(3)R did not result in the formation of arrays or clusters with channels touching each other. Gold-labeling suggests that the channel amino terminus resides near the center of the cytoplasmic tetrameric quaternary structure. The combination of nuclear isolation with freeze-drying and rotary shadow techniques allows direct visualization of InsP(3)Rs in native nuclear envelopes and can be used to determine their spatial distribution and density.
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Affiliation(s)
- Cesar Cárdenas
- Department of Physiology, University of Pennsylvania, Philadelphia, PA 19104-6085, USA
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Baddeley D, Jayasinghe ID, Lam L, Rossberger S, Cannell MB, Soeller C. Optical single-channel resolution imaging of the ryanodine receptor distribution in rat cardiac myocytes. Proc Natl Acad Sci U S A 2009; 106:22275-80. [PMID: 20018773 PMCID: PMC2799702 DOI: 10.1073/pnas.0908971106] [Citation(s) in RCA: 224] [Impact Index Per Article: 14.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2009] [Indexed: 11/18/2022] Open
Abstract
We have applied an optical super-resolution technique based on single-molecule localization to examine the peripheral distribution of a cardiac signaling protein, the ryanodine receptor (RyR), in rat ventricular myocytes. RyRs form clusters with a mean size of approximately 14 RyRs per cluster, which is almost an order of magnitude smaller than previously estimated. Clusters were typically not circular (as previously assumed) but elongated with an average aspect ratio of 1.9. Edge-to-edge distances between adjacent RyR clusters were often <50 nm, suggesting that peripheral RyR clusters may exhibit strong intercluster signaling. The wide variation of cluster size, which follows a near-exponential distribution, is compatible with a stochastic cluster assembly process. We suggest that calcium sparks may be the result of the concerted activation of several RyR clusters forming a functional "supercluster" whose gating is controlled by both cytosolic and sarcoplasmic reticulum luminal calcium levels.
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Affiliation(s)
- David Baddeley
- Department of Physiology, University of Auckland, Auckland 1142, New Zealand
| | - Isuru D. Jayasinghe
- Department of Physiology, University of Auckland, Auckland 1142, New Zealand
| | - Leo Lam
- Department of Physiology, University of Auckland, Auckland 1142, New Zealand
| | - Sabrina Rossberger
- Department of Physiology, University of Auckland, Auckland 1142, New Zealand
| | - Mark B. Cannell
- Department of Physiology, University of Auckland, Auckland 1142, New Zealand
| | - Christian Soeller
- Department of Physiology, University of Auckland, Auckland 1142, New Zealand
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Ikemoto T, Hosoya T, Takata K, Aoyama H, Hiramatsu T, Onoe H, Suzuki M, Endo M. Functional role of neuroendocrine-specific protein-like 1 in membrane translocation of GLUT4. Diabetes 2009; 58:2802-12. [PMID: 19720795 PMCID: PMC2780876 DOI: 10.2337/db09-0756] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
OBJECTIVE In skeletal muscles, dantrolene inhibits the exercise-induced membrane translocation of GLUT4. It has been postulated that the inhibitory action of dantrolene on Ca(2+) release from the sarcoplasmic reticulum (SR) causes inhibition of exercise-induced glucose uptake; however, the precise mechanism has not been adequately studied. RESEARCH DESIGN AND METHODS We discovered that dantrolene can bind to skeletal-type neuroendocrine-specific protein-like 1 (sk-NSPl1) with photoreactive dantrolene derivatives. In sk-NSPl1-deficient muscles, we examined the change in glucose uptake and the membrane translocation of GLUT4. In addition, we examined the change in blood glucose and also measured the glycogen level in both isolated and in situ skeletal muscles after electrical stimulation using our mutant mouse. RESULTS In sk-NSPl1-deficient muscles, exercise-induced glucose uptake was totally abolished with no change in insulin-induced glucose uptake. The Ca(2+) release mechanism and its inhibition by dantrolene were completely preserved in these muscles. The expression of GLUT4 in the mutant muscles also appeared unchanged. Confocal imaging and results using the membrane isolation method showed that exercise/contraction did not enhance GLUT4 translocation in these sk-NSPl1-deficient muscles under conditions of adequate muscle glycogen consumption. The blood glucose level in normal mice was reduced by electrical stimulation of the hind limbs, but that in mutant mice was unchanged. CONCLUSIONS sk-NSPl1 is a novel dantrolene receptor that plays an important role in membrane translocation of GLUT4 induced by contraction/exercise. The 23-kDa sk-NSPl1 may also be involved in the regulation of glucose levels in the whole body.
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Affiliation(s)
- Takaaki Ikemoto
- Functional Probe Research Laboratory, RIKEN Center for Molecular Imaging Science, Kobe, Japan.
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Treves S, Vukcevic M, Maj M, Thurnheer R, Mosca B, Zorzato F. Minor sarcoplasmic reticulum membrane components that modulate excitation-contraction coupling in striated muscles. J Physiol 2009; 587:3071-9. [PMID: 19403606 DOI: 10.1113/jphysiol.2009.171876] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
In striated muscle, activation of contraction is initiated by membrane depolarisation caused by an action potential, which triggers the release of Ca(2+) stored in the sarcoplasmic reticulum by a process called excitation-contraction coupling. Excitation-contraction coupling occurs via a highly sophisticated supramolecular signalling complex at the junction between the sarcoplasmic reticulum and the transverse tubules. It is generally accepted that the core components of the excitation-contraction coupling machinery are the dihydropyridine receptors, ryanodine receptors and calsequestrin, which serve as voltage sensor, Ca(2+) release channel, and Ca(2+) storage protein, respectively. Nevertheless, a number of additional proteins have been shown to be essential both for the structural formation of the machinery involved in excitation-contraction coupling and for its fine tuning. In this review we discuss the functional role of minor sarcoplasmic reticulum protein components. The definition of their roles in excitation-contraction coupling is important in order to understand how mutations in genes involved in Ca(2+) signalling cause neuromuscular disorders.
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Affiliation(s)
- Susan Treves
- Departments of Anesthesia and Biomedicine, Basel University Hospital, Switzerland
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Duke AM, Steele DS. The presence of a functional t-tubule network increases the sensitivity of RyR1 to agonists in skinned rat skeletal muscle fibres. Cell Calcium 2009; 44:411-21. [PMID: 19230144 PMCID: PMC2571965 DOI: 10.1016/j.ceca.2008.02.006] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Single mechanically skinned extensor digitorum Longus (EDL) rat fibres were used as a model to study the influence of functional t-tubules on the properties of RyR1 in adult skeletal muscle. Fibres were superfused with solutions approximating to the intracellular milieu. Following skinning, the t-tubules re-seal and repolarise, allowing the sarcoplasmic reticulum (SR) Ca2+ release to be activated by field stimulation. However, in the present study, some fibres exhibited localised regions where depolarisation-induced SR Ca2+ release was absent, due to failure of the t-tubules to re-seal. When these fibres were exposed to caffeine to directly activate RyR1, regions with re-sealed t-tubules exhibited greater sensitivity to submaximal (2-5 mM) levels of caffeine (n = 8), while the response to a supramaximal SR Ca2+ release stimulus was uniform (n = 8, p < 0.05). This difference in RyR1 sensitivity was unaffected by sustained depolarisation of the t-tubule network. However, after saponin permeabilization of the t-tubules or withdrawal of Ca2+ from the t-tubules before skinning, the difference in agonist sensitivity was abolished. These results suggest that in adult skeletal muscle fibres, the presence of a functional t-tubule network increases the sensitivity of RyR1 to agonists via a mechanism that involves binding of Ca2+ to an extracellular regulatory site.
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Affiliation(s)
- Adrian M Duke
- Institute of Membrane and Systems Biology, University of Leeds, Woodhouse Lane, Leeds LS29JT, United Kingdom
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Abstract
Malignant hyperthermia (MH) is a pharmacogenetic disorder triggered by volatile anesthetics or depolarizing muscle relaxants in predisposed individuals. Exercise or stress-induced MH episodes, in the absence of any obvious pharmacological trigger, have been reported, but these are rare. A considerable effort has taken place over the last two decades to identify mutations associated with MH and characterize their functional effects. A number of different, but complementary systems, have been developed and implemented to this end. The results of such studies have identified commonalities in functional affects of mutations, and also uncovered unexpected complexities in both the structure and function of the skeletal muscle calcium-release channel. The following review is an attempt to provide a summary of the background to current MH research, and highlight some recent advances in our knowledge of the molecular basis of the phenotypic expression of this disorder.
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Affiliation(s)
- Kathryn M Stowell
- Institute of Molecular Biosciences, Massey University, Palmerston North, New Zealand.
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Renken C, Hsieh CE, Marko M, Rath B, Leith A, Wagenknecht T, Frank J, Mannella CA. Structure of frozen-hydrated triad junctions: a case study in motif searching inside tomograms. J Struct Biol 2009; 165:53-63. [PMID: 19028586 PMCID: PMC2655133 DOI: 10.1016/j.jsb.2008.09.011] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2008] [Revised: 09/26/2008] [Accepted: 09/29/2008] [Indexed: 11/23/2022]
Abstract
We used tomographic reconstructions of frozen-hydrated triad junctions to determine the structure of the macromolecular complex associated with calcium release from the sarcoplasmic reticulum (SR), during excitation-contraction coupling. Using a rapid motif search algorithm with a reference motif of the ryanodine receptor (RyR) provided by single-particle cryo-electron microscopy, 49 receptors were located in five tomograms. Following co-alignment of the receptors and division into quadrants centered on the 4-fold symmetry axis, the receptors were classified using multivariate statistics. Global and class averages reveal that the SR membrane in the vicinity of the receptor is highly curved, creating an open vestibule with a gap of 4nm between the receptor pore and the calsequestrin layer in the SR lumen. The in-plane densities in the calsequestrin layer have paracrystalline order, consistent with the packing of calsequestrin dimers in the three-dimensional crystal structure. Faint densities ("tethers") extend to the calsequestrin layer from densities in the SR membrane located 15nm from the symmetry axis of the RyR. In a class average of RyRs with proximal transverse tubules (TT), a cytoplasmic density is observed near the receptor that could represent the most consistent location of tethers observed in tomograms between the SR and TT membranes.
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Affiliation(s)
- Christian Renken
- Wadsworth Center, New York State Department of Health, Empire State Plaza, Albany, NY 12201-0509, USA.
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