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Lukyanenko V, Muriel J, Garman D, Breydo L, Bloch RJ. Elevated Ca2+ at the triad junction underlies dysregulation of Ca2+ signaling in dysferlin-null skeletal muscle. Front Physiol 2022; 13:1032447. [PMID: 36406982 PMCID: PMC9669649 DOI: 10.3389/fphys.2022.1032447] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2022] [Accepted: 10/14/2022] [Indexed: 11/05/2022] Open
Abstract
Dysferlin-null A/J myofibers generate abnormal Ca2+ transients that are slightly reduced in amplitude compared to controls. These are further reduced in amplitude by hypoosmotic shock and often appear as Ca2+ waves (Lukyanenko et al., J. Physiol., 2017). Ca2+ waves are typically associated with Ca2+-induced Ca2+ release, or CICR, which can be myopathic. We tested the ability of a permeable Ca2+ chelator, BAPTA-AM, to inhibit CICR in injured dysferlin-null fibers and found that 10–50 nM BAPTA-AM suppressed all Ca2+ waves. The same concentrations of BAPTA-AM increased the amplitude of the Ca2+ transient in A/J fibers to wild type levels and protected transients against the loss of amplitude after hypoosmotic shock, as also seen in wild type fibers. Incubation with 10 nM BAPTA-AM led to intracellular BAPTA concentrations of ∼60 nM, as estimated with its fluorescent analog, Fluo-4AM. This should be sufficient to restore intracellular Ca2+ to levels seen in wild type muscle. Fluo-4AM was ∼10-fold less effective than BAPTA-AM, however, consistent with its lower affinity for Ca2+. EGTA, which has an affinity for Ca2+ similar to BAPTA, but with much slower kinetics of binding, was even less potent when introduced as the -AM derivative. By contrast, a dysferlin variant with GCaMP6fu in place of its C2A domain accumulated at triad junctions, like wild type dysferlin, and suppressed all abnormal Ca2+ signaling. GCaMP6fu introduced as a Venus chimera did not accumulate at junctions and failed to suppress abnormal Ca2+ signaling. Our results suggest that leak of Ca2+ into the triad junctional cleft underlies dysregulation of Ca2+ signaling in dysferlin-null myofibers, and that dysferlin’s C2A domain suppresses abnormal Ca2+ signaling and protects muscle against injury by binding Ca2+ in the cleft.
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Affiliation(s)
- Valeriy Lukyanenko
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD, United States
| | - Joaquin Muriel
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD, United States
| | - Daniel Garman
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD, United States
- Program in Biochemistry and Molecular Biology, University of Maryland, Baltimore, MD, United States
| | - Leonid Breydo
- Formulation Development, Regeneron Pharmaceuticals, Tarrytown, NY, United States
| | - Robert J. Bloch
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD, United States
- *Correspondence: Robert J. Bloch,
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The Splicing of the Mitochondrial Calcium Uniporter Genuine Activator MICU1 Is Driven by RBFOX2 Splicing Factor during Myogenic Differentiation. Int J Mol Sci 2022; 23:ijms23052517. [PMID: 35269658 PMCID: PMC8909990 DOI: 10.3390/ijms23052517] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2022] [Revised: 02/17/2022] [Accepted: 02/22/2022] [Indexed: 02/04/2023] Open
Abstract
Alternative splicing, the process by which exons within a pre-mRNA transcript are differentially joined or skipped, is crucial in skeletal muscle since it is required both during myogenesis and in post-natal life to reprogram the transcripts of contractile proteins, metabolic enzymes, and transcription factors in functionally distinct muscle fiber types. The importance of such events is underlined by the numerosity of pathological conditions caused by alternative splicing aberrations. Importantly, many skeletal muscle Ca2+ homeostasis genes are also regulated by alternative splicing mechanisms, among which is the Mitochondrial Ca2+ Uniporter (MCU) genuine activator MICU1 which regulates MCU opening upon cell stimulation. We have previously shown that murine skeletal muscle MICU1 is subjected to alternative splicing, thereby generating a splice variant-which was named MICU1.1-that confers unique properties to the mitochondrial Ca2+ uptake and ensuring sufficient ATP production for muscle contraction. Here we extended the analysis of MICU1 alternative splicing to human tissues, finding two additional splicing variants that were characterized by their ability to regulate mitochondrial Ca2+ uptake. Furthermore, we found that MICU1 alternative splicing is induced during myogenesis by the splicing factor RBFOX2. These results highlight the complexity of the alternative splicing mechanisms in skeletal muscle and the regulation of mitochondrial Ca2+ among tissues.
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A Comparative Perspective on Functionally-Related, Intracellular Calcium Channels: The Insect Ryanodine and Inositol 1,4,5-Trisphosphate Receptors. Biomolecules 2021; 11:biom11071031. [PMID: 34356655 PMCID: PMC8301844 DOI: 10.3390/biom11071031] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2021] [Revised: 07/08/2021] [Accepted: 07/10/2021] [Indexed: 02/03/2023] Open
Abstract
Calcium (Ca2+) homeostasis is vital for insect development and metabolism, and the endoplasmic reticulum (ER) is a major intracellular reservoir for Ca2+. The inositol 1,4,5- triphosphate receptor (IP3R) and ryanodine receptor (RyR) are large homotetrameric channels associated with the ER and serve as two major actors in ER-derived Ca2+ supply. Most of the knowledge on these receptors derives from mammalian systems that possess three genes for each receptor. These studies have inspired work on synonymous receptors in insects, which encode a single IP3R and RyR. In the current review, we focus on a fundamental, common question: “why do insect cells possess two Ca2+ channel receptors in the ER?”. Through a comparative approach, this review covers the discovery of RyRs and IP3Rs, examines their structures/functions, the pathways that they interact with, and their potential as target sites in pest control. Although insects RyRs and IP3Rs share structural similarities, they are phylogenetically distinct, have their own structural organization, regulatory mechanisms, and expression patterns, which explains their functional distinction. Nevertheless, both have great potential as target sites in pest control, with RyRs currently being targeted by commercial insecticide, the diamides.
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Santoro M, Piacentini R, Perna A, Pisano E, Severino A, Modoni A, Grassi C, Silvestri G. Resveratrol corrects aberrant splicing of RYR1 pre-mRNA and Ca 2+ signal in myotonic dystrophy type 1 myotubes. Neural Regen Res 2020; 15:1757-1766. [PMID: 32209783 PMCID: PMC7437583 DOI: 10.4103/1673-5374.276336] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Myotonic dystrophy type 1 (DM1) is a spliceopathy related to the mis-splicing of several genes caused by sequestration of nuclear transcriptional RNA-binding factors from non-coding CUG repeats of DMPK pre-mRNAs. Dysregulation of ryanodine receptor 1 (RYR1), sarcoplasmatic/endoplasmatic Ca2+-ATPase (SERCA) and α1S subunit of voltage-gated Ca2+ channels (Cav1.1) is related to Ca2+ homeostasis and excitation-contraction coupling impairment. Though no pharmacological treatment for DM1 exists, aberrant splicing correction represents one major therapeutic target for this disease. Resveratrol (RES, 3,5,4′-trihydroxy-trans-stilbene) is a promising pharmacological tools for DM1 treatment for its ability to directly bind the DNA and RNA influencing gene expression and alternative splicing. Herein, we analyzed the therapeutic effects of RES in DM1 myotubes in a pilot study including cultured myotubes from two DM1 patients and two healthy controls. Our results indicated that RES treatment corrected the aberrant splicing of RYR1, and this event appeared associated with restoring of depolarization-induced Ca2+ release from RYR1 dependent on the electro-mechanical coupling between RYR1 and Cav1.1. Interestingly, immunoblotting studies showed that RES treatment was associated with a reduction in the levels of CUGBP Elav-like family member 1, while RYR1, Cav1.1 and SERCA1 protein levels were unchanged. Finally, RES treatment did not induce any major changes either in the amount of ribonuclear foci or sequestration of muscleblind-like splicing regulator 1. Overall, the results of this pilot study would support RES as an attractive compound for future clinical trials in DM1. Ethical approval was obtained from the Ethical Committee of IRCCS Fondazione Policlinico Universitario A. Gemelli, Rome, Italy (rs9879/14) on May 20, 2014.
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Affiliation(s)
| | - Roberto Piacentini
- Department of Neuroscience, Università Cattolica del Sacro Cuore; Fondazione Policlinico Universitario A. Gemelli IRCCS, Rome, Italy
| | - Alessia Perna
- Department of Neuroscience, Università Cattolica del Sacro Cuore, Rome, Italy
| | - Eugenia Pisano
- Department of Cardiovascular and Thoracic Sciences, Università Cattolica del Sacro Cuore; Fondazione Policlinico Universitario A. Gemelli IRCCS, Rome, Italy
| | - Anna Severino
- Department of Cardiovascular and Thoracic Sciences, Università Cattolica del Sacro Cuore, Rome, Italy
| | - Anna Modoni
- Fondazione Policlinico Universitario A. Gemelli IRCCS, Rome, Italy
| | - Claudio Grassi
- Department of Neuroscience, Università Cattolica del Sacro Cuore; Fondazione Policlinico Universitario A. Gemelli IRCCS, Rome, Italy
| | - Gabriella Silvestri
- Department of Neuroscience, Università Cattolica del Sacro Cuore; Fondazione Policlinico Universitario A. Gemelli IRCCS, Rome, Italy
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Nakka K, Ghigna C, Gabellini D, Dilworth FJ. Diversification of the muscle proteome through alternative splicing. Skelet Muscle 2018; 8:8. [PMID: 29510724 PMCID: PMC5840707 DOI: 10.1186/s13395-018-0152-3] [Citation(s) in RCA: 52] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2017] [Accepted: 02/15/2018] [Indexed: 12/16/2022] Open
Abstract
Background Skeletal muscles express a highly specialized proteome that allows the metabolism of energy sources to mediate myofiber contraction. This muscle-specific proteome is partially derived through the muscle-specific transcription of a subset of genes. Surprisingly, RNA sequencing technologies have also revealed a significant role for muscle-specific alternative splicing in generating protein isoforms that give specialized function to the muscle proteome. Main body In this review, we discuss the current knowledge with respect to the mechanisms that allow pre-mRNA transcripts to undergo muscle-specific alternative splicing while identifying some of the key trans-acting splicing factors essential to the process. The importance of specific splicing events to specialized muscle function is presented along with examples in which dysregulated splicing contributes to myopathies. Though there is now an appreciation that alternative splicing is a major contributor to proteome diversification, the emergence of improved “targeted” proteomic methodologies for detection of specific protein isoforms will soon allow us to better appreciate the extent to which alternative splicing modifies the activity of proteins (and their ability to interact with other proteins) in the skeletal muscle. In addition, we highlight a continued need to better explore the signaling pathways that contribute to the temporal control of trans-acting splicing factor activity to ensure specific protein isoforms are expressed in the proper cellular context. Conclusions An understanding of the signal-dependent and signal-independent events driving muscle-specific alternative splicing has the potential to provide us with novel therapeutic strategies to treat different myopathies. Electronic supplementary material The online version of this article (10.1186/s13395-018-0152-3) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Kiran Nakka
- Sprott Centre for Stem Cell Research, Regenerative Medicine Program, Ottawa Hospital Research Institute, Ottawa, ON, K1H 8L6, Canada
| | - Claudia Ghigna
- Istituto di Genetica Molecolare-Consiglio Nazionale delle Ricerche (IGM-CNR), Pavia, Italy
| | - Davide Gabellini
- Unit of Gene Expression and Muscular Dystrophy, Division of Genetics and Cell Biology, IRCCS San Raffaele Scientific Institute, DIBIT2, 5A3-44, via Olgettina 58, 20132, Milan, Italy.
| | - F Jeffrey Dilworth
- Sprott Centre for Stem Cell Research, Regenerative Medicine Program, Ottawa Hospital Research Institute, Ottawa, ON, K1H 8L6, Canada. .,Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, ON, K1H 8M5, Canada. .,Sprott Centre for Stem Cell Research, Ottawa Hospital Research Institute, 501 Smyth Rd, Mailbox 511, Ottawa, ON, K1H 8L6, Canada.
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Narasimhan A, Greiner R, Bathe OF, Baracos V, Damaraju S. Differentially expressed alternatively spliced genes in skeletal muscle from cancer patients with cachexia. J Cachexia Sarcopenia Muscle 2018; 9:60-70. [PMID: 28984045 PMCID: PMC5803615 DOI: 10.1002/jcsm.12235] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/10/2017] [Revised: 07/20/2017] [Accepted: 08/03/2017] [Indexed: 01/02/2023] Open
Abstract
BACKGROUND Alternative splicing (AS) is a post-transcriptional gene regulatory mechanism that contributes to proteome diversity. Aberrant splicing mechanisms contribute to various cancers and muscle-related conditions such as Duchenne muscular dystrophy. However, dysregulation of AS in cancer cachexia (CC) remains unexplored. Our objectives were (i) to profile alternatively spliced genes (ASGs) on a genome-wide scale and (ii) to identify differentially expressed alternatively spliced genes (DASGs) associated with CC. METHODS Rectus abdominis muscle biopsies obtained from cancer patients were stratified into cachectic cases (n = 21, classified based on International consensus diagnostic framework for CC) and non-cachectic controls (n = 19, weight stable cancer patients). Human transcriptome array 2.0 was used for profiling ASGs using the total RNA isolated from muscle biopsies. Representative DASG signatures were validated using semi-quantitative RT-PCR. RESULTS We identified 8960 ASGs, of which 922 DASGs (772 up-regulated and 150 down-regulated) were identified at ≥1.4 fold-change and P < 0.05. Representative DASGs validated by semi-quantitative RT-PCR confirmed the primary findings from the human transcriptome arrays. Identified DASGs were associated with myogenesis, adipogenesis, protein ubiquitination, and inflammation. Up to 10% of the DASGs exhibited cassette exon (exon included or skipped) as a predominant form of AS event. We also observed other forms of AS events such as intron retention, alternate promoters. CONCLUSIONS Overall, we have, for the first time, conducted global profiling of muscle tissue to identify DASGs associated with CC. The mechanistic roles of the identified DASGs in CC pathophysiology using model systems is warranted, as well as replication of findings in independent cohorts.
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Affiliation(s)
- Ashok Narasimhan
- Department of Laboratory Medicine and PathologyUniversity of AlbertaEdmontonABT6G 1Z2Canada
| | - Russell Greiner
- Department of Computing SciencesUniversity of AlbertaEdmontonABT6G 2E8Canada
| | - Oliver F. Bathe
- Departments of Surgery and OncologyUniversity of CalgaryCalgaryABT2N 1N4Canada
| | - Vickie Baracos
- Department of OncologyUniversity of AlbertaEdmontonABT6G 1Z2Canada
- Cross Cancer InstituteEdmontonABT6G 1Z2Canada
| | - Sambasivarao Damaraju
- Department of Laboratory Medicine and PathologyUniversity of AlbertaEdmontonABT6G 1Z2Canada
- Cross Cancer InstituteEdmontonABT6G 1Z2Canada
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Dulhunty AF, Wei-LaPierre L, Casarotto MG, Beard NA. Core skeletal muscle ryanodine receptor calcium release complex. Clin Exp Pharmacol Physiol 2017; 44:3-12. [PMID: 27696487 DOI: 10.1111/1440-1681.12676] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2016] [Revised: 09/27/2016] [Accepted: 09/27/2016] [Indexed: 12/15/2022]
Abstract
The core skeletal muscle ryanodine receptor (RyR1) calcium release complex extends through three compartments of the muscle fibre, linking the extracellular environment through the cytoplasmic junctional gap to the lumen of the internal sarcoplasmic reticulum (SR) calcium store. The protein complex is essential for skeletal excitation-contraction (EC)-coupling and skeletal muscle function. Its importance is highlighted by perinatal death if any one of the EC-coupling components are missing and by myopathies associated with mutation of any of the proteins. The proteins essential for EC-coupling include the DHPR α1S subunit in the transverse tubule membrane, the DHPR β1a subunit in the cytosol and the RyR1 ion channel in the SR membrane. The other core proteins are triadin and junctin and calsequestrin, associated mainly with SR. These SR proteins are not essential for survival but exert structural and functional influences that modify the gain of EC-coupling and maintain normal muscle function. This review summarises our current knowledge of the individual protein/protein interactions within the core complex and their overall contribution to EC-coupling. We highlight significant areas that provide a continuing challenge for the field. Additional important components of the Ca2+ release complex, such as FKBP12, calmodulin, S100A1 and Stac3 are identified and reviewed elsewhere.
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Affiliation(s)
- Angela F Dulhunty
- John Curtin School of Medical Research, Australian National University, Canberra, ACT, Australia
| | - Lan Wei-LaPierre
- Department of Physiology and Pharmacology, University of Rochester Medical Center, Rochester, NY, USA
| | - Marco G Casarotto
- John Curtin School of Medical Research, Australian National University, Canberra, ACT, Australia
| | - Nicole A Beard
- Health Research Institute, University of Canberra, Canberra, ACT, Australia
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Tykocki NR, Boerman EM, Jackson WF. Smooth Muscle Ion Channels and Regulation of Vascular Tone in Resistance Arteries and Arterioles. Compr Physiol 2017; 7:485-581. [PMID: 28333380 DOI: 10.1002/cphy.c160011] [Citation(s) in RCA: 212] [Impact Index Per Article: 30.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Vascular tone of resistance arteries and arterioles determines peripheral vascular resistance, contributing to the regulation of blood pressure and blood flow to, and within the body's tissues and organs. Ion channels in the plasma membrane and endoplasmic reticulum of vascular smooth muscle cells (SMCs) in these blood vessels importantly contribute to the regulation of intracellular Ca2+ concentration, the primary determinant of SMC contractile activity and vascular tone. Ion channels provide the main source of activator Ca2+ that determines vascular tone, and strongly contribute to setting and regulating membrane potential, which, in turn, regulates the open-state-probability of voltage gated Ca2+ channels (VGCCs), the primary source of Ca2+ in resistance artery and arteriolar SMCs. Ion channel function is also modulated by vasoconstrictors and vasodilators, contributing to all aspects of the regulation of vascular tone. This review will focus on the physiology of VGCCs, voltage-gated K+ (KV) channels, large-conductance Ca2+-activated K+ (BKCa) channels, strong-inward-rectifier K+ (KIR) channels, ATP-sensitive K+ (KATP) channels, ryanodine receptors (RyRs), inositol 1,4,5-trisphosphate receptors (IP3Rs), and a variety of transient receptor potential (TRP) channels that contribute to pressure-induced myogenic tone in resistance arteries and arterioles, the modulation of the function of these ion channels by vasoconstrictors and vasodilators, their role in the functional regulation of tissue blood flow and their dysfunction in diseases such as hypertension, obesity, and diabetes. © 2017 American Physiological Society. Compr Physiol 7:485-581, 2017.
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Affiliation(s)
- Nathan R Tykocki
- Department of Pharmacology, University of Vermont, Burlington, Vermont, USA
| | - Erika M Boerman
- Department of Medical Pharmacology and Physiology, University of Missouri, Columbia, Missouri, USA
| | - William F Jackson
- Department of Pharmacology and Toxicology, Michigan State University, East Lansing, Michigan, USA
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Beqollari D, Romberg CF, Dobrowolny G, Martini M, Voss AA, Musarò A, Bannister RA. Progressive impairment of CaV1.1 function in the skeletal muscle of mice expressing a mutant type 1 Cu/Zn superoxide dismutase (G93A) linked to amyotrophic lateral sclerosis. Skelet Muscle 2016; 6:24. [PMID: 27340545 PMCID: PMC4918102 DOI: 10.1186/s13395-016-0094-6] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2015] [Accepted: 06/03/2016] [Indexed: 11/24/2022] Open
Abstract
Background Amyotrophic lateral sclerosis (ALS) is an adult-onset neurodegenerative disorder that is typically fatal within 3–5 years of diagnosis. While motoneuron death is the defining characteristic of ALS, the events that underlie its pathology are not restricted to the nervous system. In this regard, ALS muscle atrophies and weakens significantly before presentation of neurological symptoms. Since the skeletal muscle L-type Ca2+ channel (CaV1.1) is a key regulator of both mass and force, we investigated whether CaV1.1 function is impaired in the muscle of two distinct mouse models carrying an ALS-linked mutation. Methods We recorded L-type currents, charge movements, and myoplasmic Ca2+ transients from dissociated flexor digitorum brevis (FDB) fibers to assess CaV1.1 function in two mouse models expressing a type 1 Cu/Zn superoxide dismutase mutant (SOD1G93A). Results In FDB fibers obtained from “symptomatic” global SOD1G93A mice, we observed a substantial reduction of SR Ca2+ release in response to depolarization relative to fibers harvested from age-matched control mice. L-type current and charge movement were both reduced by ~40 % in symptomatic SOD1G93A fibers when compared to control fibers. Ca2+ transients were not significantly reduced in similar experiments performed with FDB fibers obtained from “early-symptomatic” SOD1G93A mice, but L-type current and charge movement were decreased (~30 and ~20 %, respectively). Reductions in SR Ca2+ release (~35 %), L-type current (~20 %), and charge movement (~15 %) were also observed in fibers obtained from another model where SOD1G93A expression was restricted to skeletal muscle. Conclusions We report reductions in EC coupling, L-type current density, and charge movement in FDB fibers obtained from symptomatic global SOD1G93A mice. Experiments performed with FDB fibers obtained from early-symptomatic SOD1G93A and skeletal muscle autonomous MLC/SOD1G93A mice support the idea that events occurring locally in the skeletal muscle contribute to the impairment of CaV1.1 function in ALS muscle independently of innervation status. Electronic supplementary material The online version of this article (doi:10.1186/s13395-016-0094-6) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Donald Beqollari
- Department of Medicine-Cardiology Division, University of Colorado School of Medicine, 12700 East 19th Avenue, B-139, Aurora, CO 80045 USA
| | - Christin F Romberg
- Department of Medicine-Cardiology Division, University of Colorado School of Medicine, 12700 East 19th Avenue, B-139, Aurora, CO 80045 USA
| | - Gabriella Dobrowolny
- Institute Pasteur Cenci-Bolognetti, DAHFMO-Unit of Histology and Medical Embryology, La Sapienza University, Via A. Scarpa, 14, 00161 Rome, Italy ; Center for Life Nano Science@Sapienza, Istituto Italiano di Tecnologia, Rome, Italy
| | - Martina Martini
- Institute Pasteur Cenci-Bolognetti, DAHFMO-Unit of Histology and Medical Embryology, La Sapienza University, Via A. Scarpa, 14, 00161 Rome, Italy ; Center for Life Nano Science@Sapienza, Istituto Italiano di Tecnologia, Rome, Italy
| | - Andrew A Voss
- Department of Biological Sciences, College of Science and Mathematics, Wright State University, 235A Biological Sciences, 3640 Colonel Glenn Highway, Dayton, OH 45435 USA
| | - Antonio Musarò
- Institute Pasteur Cenci-Bolognetti, DAHFMO-Unit of Histology and Medical Embryology, La Sapienza University, Via A. Scarpa, 14, 00161 Rome, Italy ; Center for Life Nano Science@Sapienza, Istituto Italiano di Tecnologia, Rome, Italy
| | - Roger A Bannister
- Department of Medicine-Cardiology Division, University of Colorado School of Medicine, 12700 East 19th Avenue, B-139, Aurora, CO 80045 USA
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Willemse H, Theodoratos A, Smith PN, Dulhunty AF. Unexpected dependence of RyR1 splice variant expression in human lower limb muscles on fiber-type composition. Pflugers Arch 2015; 468:269-78. [PMID: 26438192 DOI: 10.1007/s00424-015-1738-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2015] [Revised: 09/14/2015] [Accepted: 09/29/2015] [Indexed: 10/23/2022]
Abstract
The skeletal muscle ryanodine receptor Ca(2+) release channel (RyR1), essential for excitation-contraction (EC) coupling, demonstrates a known developmentally regulated alternative splicing in the ASI region. We now find unexpectedly that the expression of the splice variants is closely related to fiber type in adult human lower limb muscles. We examined the distribution of myosin heavy chain isoforms and ASI splice variants in gluteus minimus, gluteus medius and vastus medialis from patients aged 45 to 85 years. There was a strong positive correlation between ASI(+)RyR1 and the percentage of type 2 fibers in the muscles (r = 0.725), and a correspondingly strong negative correlation between the percentages of ASI(+)RyR1 and percentage of type 1 fibers. When the type 2 fiber data were separated into type 2X and type 2A, the correlation with ASI(+)RyR1 was stronger in type 2X fibers (r = 0.781) than in type 2A fibers (r = 0.461). There was no significant correlation between age and either fiber-type composition or ASI(+)RyR1/ASI(-)RyR1 ratio. The results suggest that the reduced expression of ASI(-)RyR1 during development may reflect a reduction in type 1 fibers during development. Preferential expression of ASI(-) RyR1, having a higher gain of in Ca(2+) release during EC coupling than ASI(+)RyR1, may compensate for the reduced terminal cisternae volume, fewer junctional contacts and reduced charge movement in type 1 fibers.
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Affiliation(s)
- Hermia Willemse
- John Curtin School of Medical Research, Australian National University, Acton, ACT, 2600, Australia.
| | - Angelo Theodoratos
- John Curtin School of Medical Research, Australian National University, Acton, ACT, 2600, Australia.
| | - Paul N Smith
- Trauma and Orthopaedic Research Unit, Canberra Hospital, Building 6, Level 1, P.O. Box 11, Woden, ACT, 2606, Australia.
| | - Angela F Dulhunty
- John Curtin School of Medical Research, Australian National University, Acton, ACT, 2600, Australia.
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Tian C, Shao CH, Padanilam C, Ezell E, Singh J, Kutty S, Bidasee KR. CCDI: a new ligand that modulates mammalian type 1 ryanodine receptor (RyR1). Br J Pharmacol 2014; 171:4097-111. [PMID: 24819467 DOI: 10.1111/bph.12764] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2013] [Revised: 04/21/2014] [Accepted: 04/29/2014] [Indexed: 02/04/2023] Open
Abstract
BACKGROUND AND PURPOSE Ryanodine receptors (RyRs) are Ca(2+)-release channels on the sarco(endo)plasmic reticulum that modulate a wide array of physiological functions. Three RyR isoforms are present in cells: RyR1, RyR2 and RyR3. To date, there are no reports on ligands that modulate RyR in an isoform-selective manner. Such ligands are not only valuable research tools, but could serve as intermediates for development of therapeutics. EXPERIMENTAL APPROACH Pyrrole-2-carboxylic acid and 1,3-dicyclohexylcarbodiimide were allowed to react in carbon tetrachloride for 24 h at low temperatures and pressures. The chemical structures of the two products isolated were elucidated using NMR spectrometry, mass spectrometry and elemental analyses. [(3) H]-ryanodine binding, lipid bilayer and time-lapsed confocal imaging were used to determine their effects on RyR isoforms. KEY RESULTS The major product, 2-cyclohexyl-3-cyclohexylimino-2, 3, dihydro-pyrrolo[1,2-c]imidazol-1-one (CCDI) dose-dependently potentiated Ca(2+)-dependent binding of [(3)H]-ryanodine to RyR1, with no significant effects on [(3)H]-ryanodine binding to RyR2 or RyR3. CCDI also reversibly increased the open probability (P(o)) of RyR1 with minimal effects on RyR2 and RyR3. CCDI induced Ca(2+) transients in C2C12 skeletal myotubes, but not in rat ventricular myocytes. This effect was blocked by pretreating cells with ryanodine. The minor product 2-cyclohexyl-pyrrolo[1,2-c]imidazole-1,3-dione had no effect on either [(3)H]-ryanodine binding or P(o) of RyR1, RyR2 and RyR3. CONCLUSIONS AND IMPLICATIONS A new ligand that preferentially modulates RyR1 was identified. In addition to being an important research tool, the pharmacophore of this small molecule could serve as a template for the synthesis of other isoform-selective modulators of RyRs.
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Affiliation(s)
- Chengju Tian
- Department of Pharmacology and Experimental Neuroscience, University of Nebraska Medical Center, Omaha, Nebraska, USA
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Wang J, Xie Z, Gao J, Liu Y, Wang W, Huang L, Wang J. Molecular cloning and characterization of a ryanodine receptor gene in brown planthopper (BPH), Nilaparvata lugens (Stål). PEST MANAGEMENT SCIENCE 2014; 70:790-797. [PMID: 23893901 DOI: 10.1002/ps.3616] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/19/2013] [Revised: 07/02/2013] [Accepted: 07/26/2013] [Indexed: 06/02/2023]
Abstract
BACKGROUND Ryanodine receptors (RyRs) are a distinct class of intracellular calcium (Ca(2+)) release channel. The recent discovery of diamide insecticides has prompted studies on insect RyRs. However, information about the structure and function of insect RyRs is still limited. In this study, we isolated and characterized a full-length RyR cDNA (named NlRyR) from the brown planthopper, Nilaparvata lugens (Stål) (Homoptera: Delphacidae), a serious rice pest throughout Asia. RESULTS The composite NlRyR gene contains an open reading frame of 15 423 bp encoding a protein of 5140 amino acid residues, which shares high sequence identity (78-81%) with other insect homologues, except for two regions (IDR1: 4379-4732; IDR2: 1307-1529) with markedly low identity (44-48 and 38-41%, respectively). All hallmarks of the RyR proteins are conserved in the NlRyR protein, including the RyR domain as well as mannosyltransferase, IP3 R and RyR (pfam02815) (MIR) and RyR and IP3 R homology (pfam01365) (RIH) domains. Expression analysis of NlRyR revealed significant differences in mRNA expression levels among N. lugens developmental stages. Furthermore, three alternative splicing sites were identified in NlRyR, one of which forms the mutually exclusive exons A/B and is conserved in various insect species. Diagnostic PCR assays showed that the splice variant containing exon A was predominantly detected in all developmental stages. CONCLUSION NlRyR may play an important role in the control of developmental processes of N. lugens. Alternative splicing may generate the functional diversity of NlRyR. The results provided the basis for further structural and functional characterization of NlRyR.
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Affiliation(s)
- Jian Wang
- College of Horticulture and Plant Protection, Yangzhou University, Yangzhou, China
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14
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Yuan GR, Shi WZ, Yang WJ, Jiang XZ, Dou W, Wang JJ. Molecular characteristics, mRNA expression, and alternative splicing of a ryanodine receptor gene in the oriental fruit fly, Bactrocera dorsalis (Hendel). PLoS One 2014; 9:e95199. [PMID: 24740254 PMCID: PMC3989282 DOI: 10.1371/journal.pone.0095199] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2014] [Accepted: 03/24/2014] [Indexed: 01/13/2023] Open
Abstract
Ryanodine receptors (RyRs) are a distinct class of ligand-gated channels controlling the release of calcium from intracellular stores. The emergence of diamide insecticides, which selectively target insect RyRs, has promoted the study of insect RyRs. In the present study, the full-length RyR cDNA (BdRyR) was cloned and characterized from the oriental fruit fly, Bactrocera dorsalis (Hendel), a serious pest of fruits and vegetables throughout East Asia and the Pacific Rim. The cDNA of BdRyR contains a 15,420-bp open reading frame encoding 5,140 amino acids with a predicted molecular weight of 582.4 kDa and an isoelectric point of 5.38. BdRyR shows a high level of amino acid sequence identity (78 to 97%) to other insect RyR isoforms. All common structural features of the RyRs are present in the BdRyR, including a well-conserved C-terminal domain containing consensus calcium-binding EF-hands and six transmembrane domains, and a large N-terminal domain. Quantitative real-time PCR analyses revealed that BdRyR was expressed at the lowest and highest levels in egg and adult, respectively, and that the BdRyR expression levels in the third instar larva, pupa and adult were 166.99-, 157.56- and 808.56-fold higher, respectively, than that in the egg. Among different adult body parts, the highest expression level was observed in the thorax compared with the head and abdomen. In addition, four alternative splice sites were identified in the BdRyR gene, with the first, ASI, being located in the central part of the predicted second spore lysis A/RyR domain. Diagnostic PCR analyses revealed that alternative splice variants were generated not only in a tissue-specific manner but also in a developmentally regulated manner. These results lay the foundation for further understanding the structural and functional properties of BdRyR, and the molecular mechanisms for target site resistance in B. dorsalis.
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Affiliation(s)
- Guo-Rui Yuan
- Key Laboratory of Entomology and Pest Control Engineering, College of Plant Protection, Southwest University, Chongqing, China
| | - Wen-Zhi Shi
- Key Laboratory of Entomology and Pest Control Engineering, College of Plant Protection, Southwest University, Chongqing, China
| | - Wen-Jia Yang
- Key Laboratory of Entomology and Pest Control Engineering, College of Plant Protection, Southwest University, Chongqing, China
| | - Xuan-Zhao Jiang
- Key Laboratory of Entomology and Pest Control Engineering, College of Plant Protection, Southwest University, Chongqing, China
| | - Wei Dou
- Key Laboratory of Entomology and Pest Control Engineering, College of Plant Protection, Southwest University, Chongqing, China
| | - Jin-Jun Wang
- Key Laboratory of Entomology and Pest Control Engineering, College of Plant Protection, Southwest University, Chongqing, China
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15
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Wang J, Liu Y, Gao J, Xie Z, Huang L, Wang W, Wang J. Molecular cloning and mRNA expression of a ryanodine receptor gene in the cotton bollworm, Helicoverpa armigera. PESTICIDE BIOCHEMISTRY AND PHYSIOLOGY 2013; 107:327-333. [PMID: 24267694 DOI: 10.1016/j.pestbp.2013.09.006] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/31/2013] [Revised: 09/11/2013] [Accepted: 09/17/2013] [Indexed: 06/02/2023]
Abstract
Ryanodine receptors (RyRs) are the targets of novel diamide insecticides. The cotton bollworm, Helicoverpa armigera, is one of the most important cotton pests in the world. In this study, we report the full-length RyR cDNA sequence (named as HaRyR) of H. armigera. The 16,083-bp contiguous sequence encoded 5, 142 amino acid residues, which shares 80% and 78% overall identities with its homologues in Nilaparvata lugens (NlRyR) and Drosophila melanogaster (DmRyR), respectively. All hallmarks of RyR proteins are conserved in the HaRyR, including the GXRXGGGXGD motif conserved in the Ca(2+) release channels and four copies of RyR domain unique to RyR channels. The previously identified seven lepidopteran-specific RyR residues were also found in HaRyR (N(4977), N(4979), N(4990), L(5005), L(5036), N(5068) and T(5119)). An amino acid sequence alignment showed that the N-terminal region of HaRyR (residues 188-295) shared high sequence identity with NlRyR (94%) and DmRyR (92%), and moderate sequence identity (47-50%) with three rabbit RyR isoforms, while the short segment of the C-terminal transmembrane region of HaRyR (residues 4632-4676) exhibited moderate sequence identity with NlRyR (69%) and DmRyR (67%), and low sequence identity (19-28%) with three rabbit RyR isoforms. In addition, expression analysis of HaRyR revealed that the mRNA expression level in eggs was significantly lower than in third instar larvae, pupae and adults, and anatomical regulation of HaRyR expression was also observed with the highest expression level in head compared with thorax and abdomen. Our results lay a foundation for comprehensive structural and functional characterization of HaRyR and for understanding of the molecular mechanisms of toxicity selectivity of diamide insecticides among different species.
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Affiliation(s)
- Jian Wang
- College of Horticulture and Plant Protection, Yangzhou University, Yangzhou 225009, PR China
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16
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Vihola A, Sirito M, Bachinski LL, Raheem O, Screen M, Suominen T, Krahe R, Udd B. Altered expression and splicing of Ca(2+) metabolism genes in myotonic dystrophies DM1 and DM2. Neuropathol Appl Neurobiol 2013; 39:390-405. [PMID: 22758909 DOI: 10.1111/j.1365-2990.2012.01289.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
AIMS Myotonic dystrophy types 1 and 2 (DM1 and DM2) are multisystem disorders caused by similar repeat expansion mutations, with similar yet distinct clinical features. Aberrant splicing of multiple effector genes, as well as dysregulation of transcription and translation, has been suggested to underlie different aspects of the complex phenotypes in DM1 and DM2. Ca(2+) plays a central role in both muscle contraction and control of gene expression, and recent expression profiling studies have indicated major perturbations of the Ca(2+) signalling pathways in DM. Here we have further investigated the expression of genes and proteins involved in Ca(2+) metabolism in DM patients, including Ca(2+) channels and Ca(2+) binding proteins. METHODS We used patient muscle biopsies to analyse mRNA expression and splicing of genes by microarray expression profiling and RT-PCR. We studied protein expression by immunohistochemistry and immunoblotting. RESULTS Most of the genes studied showed mRNA up-regulation in expression profiling. When analysed by immunohistochemistry the Ca(2+) release channel ryanodine receptor was reduced in DM1 and DM2, as was calsequestrin 2, a sarcoplasmic reticulum lumen Ca(2+) storage protein. Abnormal splicing of ATP2A1 was more pronounced in DM2 than DM1. CONCLUSIONS We observed abnormal mRNA and protein expression in DM affecting several proteins involved in Ca(2+) metabolism, with some differences between DM1 and DM2. Our protein expression studies are suggestive of a post-transcriptional defect(s) in the myotonic dystrophies.
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Affiliation(s)
- A Vihola
- Folkhälsan Institute of Genetics and Department of Medical Genetics, Haartman Institute, University of Helsinki, Helsinki, Finland.
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17
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Boyer JG, Murray LM, Scott K, De Repentigny Y, Renaud JM, Kothary R. Early onset muscle weakness and disruption of muscle proteins in mouse models of spinal muscular atrophy. Skelet Muscle 2013; 3:24. [PMID: 24119341 PMCID: PMC3852932 DOI: 10.1186/2044-5040-3-24] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2013] [Accepted: 09/26/2013] [Indexed: 11/12/2022] Open
Abstract
Background The childhood neuromuscular disease spinal muscular atrophy (SMA) is caused by mutations or deletions of the survival motor neuron (SMN1) gene. Although SMA has traditionally been considered a motor neuron disease, the muscle-specific requirement for SMN has never been fully defined. Therefore, the purpose of this study was to investigate muscle defects in mouse models of SMA. Methods We have taken advantage of two different mouse models of SMA, the severe Smn-/-;SMN2 mice and the less severe Smn2B/- mice. We have measured the maximal force produced from control muscles and those of SMA model mice by direct stimulation using an ex vivo apparatus. Immunofluorescence and immunoblot experiments were performed to uncover muscle defects in mouse models of SMA. Means from control and SMA model mice samples were compared using an analysis of variance test and Student’s t tests. Results We report that tibialis anterior (TA) muscles of phenotype stage Smn-/-;SMN2 mice generate 39% less maximal force than muscles from control mice, independently of aberrant motor neuron signal transmission. In addition, during muscle fatigue, the Smn-/-;SMN2 muscle shows early onset and increased unstimulated force compared with controls. Moreover, we demonstrate a significant decrease in force production in muscles from pre-symptomatic Smn-/-;SMN2 and Smn2B/- mice, indicating that muscle weakness is an early event occurring prior to any overt motor neuron loss and muscle denervation. Muscle weakness in mouse models of SMA was associated with a delay in the transition from neonatal to adult isoforms of proteins important for proper muscle contractions, such as ryanodine receptors and sodium channels. Immunoblot analyses of extracts from hindlimb skeletal muscle revealed aberrant levels of the sarcoplasmic reticulum Ca2+ ATPase. Conclusions The findings from this study reveal a delay in the appearance of mature isoforms of proteins important for muscle contractions, as well as muscle weakness early in the disease etiology, thus highlighting the contributions of skeletal muscle defects to the SMA phenotype.
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Affiliation(s)
- Justin G Boyer
- Ottawa Hospital Research Institute, Regenerative Medicine Program, 501 Smyth Road, Ottawa, ON K1H 8L6, Canada.
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18
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Botta A, Malena A, Loro E, Del Moro G, Suman M, Pantic B, Szabadkai G, Vergani L. Altered Ca2+ homeostasis and endoplasmic reticulum stress in myotonic dystrophy type 1 muscle cells. Genes (Basel) 2013; 4:275-92. [PMID: 24705164 PMCID: PMC3899969 DOI: 10.3390/genes4020275] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2013] [Revised: 05/03/2013] [Accepted: 05/16/2013] [Indexed: 12/15/2022] Open
Abstract
The pathogenesis of Myotonic Dystrophy type 1 (DM1) is linked to unstable CTG repeats in the DMPK gene which induce the mis-splicing to fetal/neonatal isoforms of many transcripts, including those involved in cellular Ca2+ homeostasis. Here we monitored the splicing of three genes encoding for Ca2+ transporters and channels (RyR1, SERCA1 and CACN1S) during maturation of primary DM1 muscle cells in parallel with the functionality of the Excitation-Contraction (EC) coupling machinery. At 15 days of differentiation, fetal isoforms of SERCA1 and CACN1S mRNA were significantly higher in DM1 myotubes compared to controls. Parallel functional studies showed that the cytosolic Ca2+ response to depolarization in DM1 myotubes did not increase during the progression of differentiation, in contrast to control myotubes. While we observed no differences in the size of intracellular Ca2+ stores, DM1 myotubes showed significantly reduced RyR1 protein levels, uncoupling between the segregated ER/SR Ca2+ store and the voltage-induced Ca2+ release machinery, parallel with induction of endoplasmic reticulum (ER) stress markers. In conclusion, our data suggest that perturbed Ca2+ homeostasis, via activation of ER stress, contributes to muscle degeneration in DM1 muscle cells likely representing a premature senescence phenotype.
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Affiliation(s)
- Annalisa Botta
- Department of Genetics, University "Tor Vergata", Roma 00133, Italy.
| | - Adriana Malena
- Department of Neurosciences SNPSRR, University of Padova, Padova 35100, Italy.
| | - Emanuele Loro
- Department of Physiology, Pennsylvania Muscle Institute, University of Pennsylvania, Philadelphia, PA 19104, USA.
| | - Giulia Del Moro
- Department of Neurosciences SNPSRR, University of Padova, Padova 35100, Italy.
| | - Matteo Suman
- Department of Biomedical Sciences, University of Padua and CNR Neuroscience Institute, Padua 35100, Italy.
| | - Boris Pantic
- Department of Neurosciences SNPSRR, University of Padova, Padova 35100, Italy.
| | - Gyorgy Szabadkai
- Department of Biomedical Sciences, University of Padua and CNR Neuroscience Institute, Padua 35100, Italy.
| | - Lodovica Vergani
- Department of Neurosciences SNPSRR, University of Padova, Padova 35100, Italy.
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19
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Huguet A, Medja F, Nicole A, Vignaud A, Guiraud-Dogan C, Ferry A, Decostre V, Hogrel JY, Metzger F, Hoeflich A, Baraibar M, Gomes-Pereira M, Puymirat J, Bassez G, Furling D, Munnich A, Gourdon G. Molecular, physiological, and motor performance defects in DMSXL mice carrying >1,000 CTG repeats from the human DM1 locus. PLoS Genet 2012; 8:e1003043. [PMID: 23209425 PMCID: PMC3510028 DOI: 10.1371/journal.pgen.1003043] [Citation(s) in RCA: 84] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2012] [Accepted: 09/05/2012] [Indexed: 11/22/2022] Open
Abstract
Myotonic dystrophy type 1 (DM1) is caused by an unstable CTG repeat expansion in the 3′UTR of the DM protein kinase (DMPK) gene. DMPK transcripts carrying CUG expansions form nuclear foci and affect splicing regulation of various RNA transcripts. Furthermore, bidirectional transcription over the DMPK gene and non-conventional RNA translation of repeated transcripts have been described in DM1. It is clear now that this disease may involve multiple pathogenic pathways including changes in gene expression, RNA stability and splicing regulation, protein translation, and micro–RNA metabolism. We previously generated transgenic mice with 45-kb of the DM1 locus and >300 CTG repeats (DM300 mice). After successive breeding and a high level of CTG repeat instability, we obtained transgenic mice carrying >1,000 CTG (DMSXL mice). Here we described for the first time the expression pattern of the DMPK sense transcripts in DMSXL and human tissues. Interestingly, we also demonstrate that DMPK antisense transcripts are expressed in various DMSXL and human tissues, and that both sense and antisense transcripts accumulate in independent nuclear foci that do not co-localize together. Molecular features of DM1-associated RNA toxicity in DMSXL mice (such as foci accumulation and mild missplicing), were associated with high mortality, growth retardation, and muscle defects (abnormal histopathology, reduced muscle strength, and lower motor performances). We have found that lower levels of IGFBP-3 may contribute to DMSXL growth retardation, while increased proteasome activity may affect muscle function. These data demonstrate that the human DM1 locus carrying very large expansions induced a variety of molecular and physiological defects in transgenic mice, reflecting DM1 to a certain extent. As a result, DMSXL mice provide an animal tool to decipher various aspects of the disease mechanisms. In addition, these mice can be used to test the preclinical impact of systemic therapeutic strategies on molecular and physiological phenotypes. Myotonic dystrophy type 1 (DM1) is caused by the abnormal expansion of a CTG repeat located in the DM protein kinase (DMPK) gene. DMPK transcripts carrying CUG expansions form toxic nuclear foci that affect other RNAs. DM1 involve multiple pathogenic pathways including changes in gene expression, RNA stability and splicing regulation, protein translation, and micro–RNA metabolism. We previously generated transgenic mice carrying the human DM1 locus and very large expansions >1,000 CTG (DMSXL mice). Here we described for the first time, the expression pattern of the DMPK sense transcripts in DMSXL and human tissues. We also demonstrate that DMPK antisense transcripts are expressed in various tissues from DMSXL mice and human. Both sense and antisense transcripts form nuclear foci. DMSXL mice showed molecular DM1 features such as foci and mild splicing defects as well as muscles defects, reduced muscle strength, and lower motor performances. These mice recapitulate some molecular features of DM1 leading to physiological abnormalities. DMSXL are not only a tool to decipher various mechanisms involved in DM1 but also to test the preclinical impact of systemic therapeutic strategies.
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Affiliation(s)
- Aline Huguet
- Inserm U781, Université Paris Descartes-Sorbonne Paris Cité, Institut Imagine, Hôpital Necker-Enfants Malades, Paris, France
| | - Fadia Medja
- Institut de Myologie, Université Paris 6 UMR S974, Inserm U974, CNRS UMR 7215, GH Pitié-Salpêtrière, Paris, France
| | - Annie Nicole
- Inserm U781, Université Paris Descartes-Sorbonne Paris Cité, Institut Imagine, Hôpital Necker-Enfants Malades, Paris, France
| | - Alban Vignaud
- Institut de Myologie, Université Paris 6 UMR S974, Inserm U974, CNRS UMR 7215, GH Pitié-Salpêtrière, Paris, France
- Généthon, Evry, France
| | - Céline Guiraud-Dogan
- Inserm U955, Département de Neurosciences, Faculté de Médecine, Université Paris XII, Créteil, France
| | - Arnaud Ferry
- Institut de Myologie, Université Paris 6 UMR S974, Inserm U974, CNRS UMR 7215, GH Pitié-Salpêtrière, Paris, France
- Université Paris Descartes-Sorbonne Paris Cité, Paris, France
| | - Valérie Decostre
- Institut de Myologie, Université Paris 6 UMR S974, Inserm U974, CNRS UMR 7215, GH Pitié-Salpêtrière, Paris, France
| | - Jean-Yves Hogrel
- Institut de Myologie, Université Paris 6 UMR S974, Inserm U974, CNRS UMR 7215, GH Pitié-Salpêtrière, Paris, France
| | - Friedrich Metzger
- F. Hoffmann-La Roche, CNS Pharma Research and Development, Basel, Switzerland
| | - Andreas Hoeflich
- Leibniz-Institute for Farm Animal Biology (FBN), Dummerstorf, Germany
| | - Martin Baraibar
- UPMC Univ Paris 06, UM 76, Institut de Myologie and Inserm, U974 and CNRS, UMR7215, Paris, France
| | - Mário Gomes-Pereira
- Inserm U781, Université Paris Descartes-Sorbonne Paris Cité, Institut Imagine, Hôpital Necker-Enfants Malades, Paris, France
| | - Jack Puymirat
- Human Genetics Research Unit, Laval University, Québec City, Québec, Canada
| | - Guillaume Bassez
- Inserm U955, Département de Neurosciences, Faculté de Médecine, Université Paris XII, Créteil, France
| | - Denis Furling
- Institut de Myologie, Université Paris 6 UMR S974, Inserm U974, CNRS UMR 7215, GH Pitié-Salpêtrière, Paris, France
| | - Arnold Munnich
- Inserm U781, Université Paris Descartes-Sorbonne Paris Cité, Institut Imagine, Hôpital Necker-Enfants Malades, Paris, France
| | - Geneviève Gourdon
- Inserm U781, Université Paris Descartes-Sorbonne Paris Cité, Institut Imagine, Hôpital Necker-Enfants Malades, Paris, France
- * E-mail:
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Mapping domains and mutations on the skeletal muscle ryanodine receptor channel. Trends Mol Med 2012; 18:644-57. [DOI: 10.1016/j.molmed.2012.09.006] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2012] [Revised: 08/14/2012] [Accepted: 09/19/2012] [Indexed: 11/20/2022]
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Mittendorf KF, Deatherage CL, Ohi MD, Sanders CR. Tailoring of membrane proteins by alternative splicing of pre-mRNA. Biochemistry 2012; 51:5541-56. [PMID: 22708632 DOI: 10.1021/bi3007065] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Alternative splicing (AS) of RNA is a key mechanism for diversification of the eukaryotic proteome. In this process, different mRNA transcripts can be produced through altered excision and/or inclusion of exons during processing of the pre-mRNA molecule. Since its discovery, AS has been shown to play roles in protein structure, function, and localization. Dysregulation of this process can result in disease phenotypes. Moreover, AS pathways are promising therapeutic targets for a number of diseases. Integral membrane proteins (MPs) represent a class of proteins that may be particularly amenable to regulation by alternative splicing because of the distinctive topological restraints associated with their folding, structure, trafficking, and function. Here, we review the impact of AS on MP form and function and the roles of AS in MP-related disorders such as Alzheimer's disease.
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Affiliation(s)
- Kathleen F Mittendorf
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
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22
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Wang J, Li Y, Han Z, Zhu Y, Xie Z, Wang J, Liu Y, Li X. Molecular characterization of a ryanodine receptor gene in the rice leaffolder, Cnaphalocrocis medinalis (Guenée). PLoS One 2012; 7:e36623. [PMID: 22567170 PMCID: PMC3342285 DOI: 10.1371/journal.pone.0036623] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2012] [Accepted: 04/03/2012] [Indexed: 11/25/2022] Open
Abstract
Ryanodine receptors (RyRs) are the targets of two novel classes of synthetic insecticidal chemicals, phthalic acid diamides and anthranilic diamides. Isolation of full-length RyR cDNAs is a critical step towards the structural and functional characterization of insect RyRs and an understanding of the molecular mechanisms underlying the species selective toxicity of diamide insecticides. However, there has been little research on the insect RyR genes due to the high molecular weight of the RyR proteins. In this study, we isolated a full-length RyR cDNA (named as CmRyR) from Cnaphalocrocis medinalis, an important rice pest throughout Southeast Asia. The composite CmRyR gene contains an ORF of 15264 bp encoding a protein of 5087 amino acid residues, which shares 79% overall identity with its Drosophila melanogaster homologue. All hallmarks of the RyR proteins are conserved in the CmRyR protein, suggesting that CmRyR is a structural and functional analogue of known RyRs. A multiple sequence alignment illustrates that the insect RyRs share high levels of amino acid sequence identity at the the COOH-terminal region. However, the amino acid residues analogous to the CmRyR residues N4922, N4924, N4935, L4950, L4981, N5013 and T5064 are unique to lepidopteran RyRs compared with non-lepidopteran insect RyRs. This finding suggests that these residues may be involved in the differences in channel properties between lepidopteran and non-lepidopteran insect RyRs and in the species selective toxicity of diamide insecticides. Furthermore, two alternative splicing sites were identified in the CmRyR gene, one of which was located in the central part of the predicted second SPRY domain. Diagnostic PCR showed that the inclusion frequencies of two mutually exclusive exons (a/b) and one optional exon (c) differed between developmental stages or adult anatomical regions. Our results imply that alternative splicing may be a major means of generating functional diversity in C. medinalis RyR channel.
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Affiliation(s)
- Jianjun Wang
- College of Horticulture and Plant Protection, Yangzhou University, Yangzhou, China.
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23
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Ca2+-signaling, alternative splicing and endoplasmic reticulum stress responses. Neurochem Res 2011; 36:1198-211. [PMID: 21365449 DOI: 10.1007/s11064-011-0431-4] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/18/2011] [Indexed: 01/01/2023]
Abstract
Ca(2+)-signaling, alternative splicing, and stress responses by the endoplasmic reticulum are three important cellular activities which can be strongly interconnected to alter the expression of protein isoforms in a tissue dependent manner or during development depending on the environmental conditions. This integrated network of signaling pathways permits a high degree of versatility and adaptation to metabolic, developmental and stress processes. Defects in its regulation may lead to cellular malfunction.
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Tae H, Wei L, Willemse H, Mirza S, Gallant EM, Board PG, Dirksen RT, Casarotto MG, Dulhunty A. The elusive role of the SPRY2 domain in RyR1. Channels (Austin) 2011; 5:148-60. [PMID: 21239886 DOI: 10.4161/chan.5.2.14407] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
The second of three SPRY domains (SPRY2, S1085 -V1208) located in the skeletal muscle ryanodine receptor (RyR1) is contained within regions of RyR1 that influence EC coupling and bind to imperatoxin A, a toxin probe of RyR1 channel gating. We examined the binding of the F loop (P1107-A1121) in SPRY2 to the ASI/basic region in RyR1 (T3471-G3500, containing both alternatively spliced (ASI) residues and neighboring basic amino acids). We then investigated the possible influence of this interaction on excitation contraction (EC) coupling. A peptide with the F loop sequence and an antibody to the SPRY2 domain each enhanced RyR1 activity at low concentrations and inhibited at higher concentrations. A peptide containing the ASI/basic sequence bound to SPRY2 and binding decreased ~10-fold following mutation or structural disruption of the basic residues. Binding was abolished by mutation of three critical acidic F loop residues. Together these results suggest that the ASI/basic and SPRY2 domains interact in an F loop regulatory module. Although a region that includes the SPRY2 domain influences EC coupling, as does the ASI/basic region, Ca2+ release during ligand- and depolarization-induced RyR1 activation were not altered by mutation of the three critical F loop residues following expression of mutant RyR1 in RyR1-null myotubes. Therefore the electrostatic regulatory interaction between the SPRY2 F loop residues (that bind to imperatoxin A) and the ASI/basic residues of RyR1 does not influence bi-directional DHPR-RyR1 signaling during skeletal EC coupling, possibly because the interaction is interrupted by the influence of factors present in intact muscle cells.
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Affiliation(s)
- HanShen Tae
- Howard Florey Institute, Parkville, Victoria, Australia
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Takasawa S, Kuroki M, Nata K, Noguchi N, Ikeda T, Yamauchi A, Ota H, Itaya-Hironaka A, Sakuramoto-Tsuchida S, Takahashi I, Yoshikawa T, Shimosegawa T, Okamoto H. A novel ryanodine receptor expressed in pancreatic islets by alternative splicing from type 2 ryanodine receptor gene. Biochem Biophys Res Commun 2010; 397:140-5. [PMID: 20471962 DOI: 10.1016/j.bbrc.2010.05.051] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2010] [Accepted: 05/07/2010] [Indexed: 12/13/2022]
Abstract
Cyclic ADP-ribose (cADPR), a potent Ca(2+) mobilizing intracellular messenger synthesized by CD38, regulates the opening of ryanodine receptors (RyRs). Increases in intracellular Ca(2+) concentrations in pancreatic islets, resulting from Ca(2+) mobilization from RyRs as well as Ca(2+) influx from extracellular sources, are important in insulin secretion by glucose. In the present study, by screening a rat islet cDNA library, we isolated a novel RyR cDNA (the islet-type RyR), which is generated from the RyR2 gene by alternative splicing of exons 4 and 75. When the expression vectors for the islet-type and the authentic RyRs were transfected into HEK293 cells, the islet-type RyR2 as well as the authentic one showed high affinity [(3)H]ryanodine binding. Intracellular Ca(2+) release in the islet-type RyR2-transfected cells was enhanced in the presence of cADPR but not in the authentic RyR2-transfected cells. The islet-type RyR2 mRNA was expressed in a variety of tissues such as in pancreatic islets, cerebrum, and cerebellum, whereas the authentic RyR2 mRNA was predominantly expressed in heart and aorta. These results suggest that the islet-type RyR2 may be an intracellular target for cADPR signaling.
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Affiliation(s)
- Shin Takasawa
- Department of Biochemistry, Nara Medical University, Kashihara 634-8521, Japan
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Junctin and triadin each activate skeletal ryanodine receptors but junctin alone mediates functional interactions with calsequestrin. Int J Biochem Cell Biol 2009; 41:2214-24. [PMID: 19398037 DOI: 10.1016/j.biocel.2009.04.017] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2008] [Revised: 04/12/2009] [Accepted: 04/20/2009] [Indexed: 11/23/2022]
Abstract
Normal Ca(2+) signalling in skeletal muscle depends on the membrane associated proteins triadin and junctin and their ability to mediate functional interactions between the Ca(2+) binding protein calsequestrin and the type 1 ryanodine receptor in the lumen of the sarcoplasmic reticulum. This important mechanism conserves intracellular Ca(2+) stores, but is poorly understood. Triadin and junctin share similar structures and are lumped together in models of interactions between skeletal muscle calsequestrin and ryanodine receptors, however their individual roles have not been examined at a molecular level. We show here that purified skeletal ryanodine receptors are similarly activated by purified triadin or purified junctin added to their luminal side, although a lack of competition indicated that the proteins act at independent sites. Surprisingly, triadin and junctin differed markedly in their ability to transmit information between skeletal calsequestrin and ryanodine receptors. Purified calsequestrin inhibited junctin/triadin-associated, or junctin-associated, ryanodine receptors and the calsequestrin re-associated channel complexes were further inhibited when luminal Ca(2+) fell from 1mM to <or=100 microM, as seen with native channels (containing endogenous calsequestrin/triadin/junctin). In contrast, skeletal calsequestrin had no effect on the triadin/ryanodine receptor complex and the channel activity of this complex increased when luminal Ca(2+) fell, as seen with purified channels prior to triadin/calsequestrin re-association. Therefore in this cell free system, junctin alone mediates signals between luminal Ca(2+), skeletal calsequestrin and skeletal ryanodine receptors and may curtail resting Ca(2+) leak from the sarcoplasmic reticulum. We suggest that triadin serves a different function which may dominate during excitation-contraction coupling.
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Kimura T, Lueck JD, Harvey PJ, Pace SM, Ikemoto N, Casarotto MG, Dirksen RT, Dulhunty AF. Alternative splicing of RyR1 alters the efficacy of skeletal EC coupling. Cell Calcium 2009; 45:264-74. [PMID: 19131108 DOI: 10.1016/j.ceca.2008.11.005] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2008] [Revised: 11/05/2008] [Accepted: 11/13/2008] [Indexed: 11/16/2022]
Abstract
Alternative splicing of ASI residues (Ala(3481)-Gln(3485)) in the skeletal muscle ryanodine receptor (RyR1) is developmentally regulated: the residues are present in adult ASI(+)RyR1, but absent in the juvenile ASI(-)RyR1 which is over-expressed in adult myotonic dystrophy type 1 (DM1). Although this splicing switch may influence RyR1 function in developing muscle and DM1, little is known about the properties of the splice variants. We examined excitation-contraction (EC) coupling and the structure and interactions of the ASI domain (Thr(3471)-Gly(3500)) in the splice variants. Depolarisation-dependent Ca(2+) release was enhanced by >50% in myotubes expressing ASI(-)RyR1 compared with ASI(+)RyR1, although DHPR L-type currents and SR Ca(2+) content were unaltered, while ASI(-)RyR1 channel function was actually depressed. The effect on EC coupling did not depend on changes in ASI domain secondary structure. Probing RyR1 function with peptides possessing the ASI domain sequence indicated that the domain contributes to an inhibitory module in RyR1. The action of the peptide depended on a sequence of basic residues and their alignment in an alpha-helix adjacent to the ASI splice site. This is the first evidence that the ASI residues contribute to an inhibitory module in RyR1 that influences EC coupling. Implications for development and DM1 are discussed.
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Affiliation(s)
- Takashi Kimura
- Hyogo College of Medicine, 1-1 Mukogawa-cho Nishinomiya, Hyogo 663-8501, Japan
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Chiang W, Yoon HJ, Linz JE, Airey JA, Strasburg GM. Divergent mechanisms in generating molecular variations of αRYR and βRYR in turkey skeletal muscle. J Muscle Res Cell Motil 2008; 28:343-54. [DOI: 10.1007/s10974-008-9130-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2007] [Accepted: 02/20/2008] [Indexed: 10/22/2022]
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Monnier N, Marty I, Faure J, Castiglioni C, Desnuelle C, Sacconi S, Estournet B, Ferreiro A, Romero N, Laquerriere A, Lazaro L, Martin JJ, Morava E, Rossi A, Van der Kooi A, de Visser M, Verschuuren C, Lunardi J. Null mutations causing depletion of the type 1 ryanodine receptor (RYR1) are commonly associated with recessive structural congenital myopathies with cores. Hum Mutat 2008; 29:670-8. [DOI: 10.1002/humu.20696] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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30
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Abstract
Ryanodine receptors (RyRs)/Ca2+ release channels, on the endoplasmic and sarcoplasmic reticulum of most cell types, are required for intracellular Ca2+ release involved in diverse cellular functions, including muscle contraction and neurotransmitter release. The large cytoplasmic domain of the RyR serves as a scaffold for proteins that bind to and modulate the channel's function and that comprise a macromolecular signaling complex. These proteins include calstabins [FK506-binding proteins (FKBPs)], calmodulin (CaM), phosphodiesterase, kinases, phosphatases, and their cognate targeting proteins. This review focuses on recent progress in the understanding of RyR regulation and disease mechanisms that are associated with channel dysfunction.
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Affiliation(s)
- Ran Zalk
- Department of Physiology and Cellular Biophysics, Columbia University College of Physicians and Surgeons, New York, New York 10032, USA.
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31
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Kimura T, Pace SM, Wei L, Beard NA, Dirksen RT, Dulhunty AF. A variably spliced region in the type 1 ryanodine receptor may participate in an inter-domain interaction. Biochem J 2007; 401:317-24. [PMID: 16989644 PMCID: PMC1698670 DOI: 10.1042/bj20060686] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The aim of the present study was to examine residues that are variably spliced in the juvenile and adult isoforms of the skeletal-muscle RyR1 (type 1 ryanodine receptor). The juvenile ASI(-) splice variant is less active than the adult ASI(+) variant and is overexpressed in patients with DM (myotonic dystrophy) [Kimura, Nakamori, Lueck, Pouliquin, Aoike, Fujimura, Dirksen, Takahashi, Dulhunty and Sakoda (2005) Hum. Mol. Genet. 14, 2189-2200]. In the present study, we explore the ASI region using synthetic peptides corresponding to rabbit RyR1 residues Thr3471-Gly3500 either containing [PASI(+)] or lacking [PASI(-)] the ASI residues. Both peptides increased [3H]ryanodine binding to rabbit RyR1s, increased Ca2+ release from sarcoplasmic reti-culum vesicles and increased single RyR1 channel activity. The peptide PASI(-) was more active in each case than PASI(+). [3H]Ryanodine binding to recombinant ASI(+)RyR1 or ASI(-)-RyR1 was enhanced more by PASI(-) than PASI(+), with the greatest increase seen when PASI(-) was added to ASI(-)RyR1. The activation of the RyR channels is consistent with the hypo-thesis that the peptides interrupt an inhibitory inter-domain inter-action and that PASI(-) is more effective at interrupting this interaction than PASI(+). We therefore suggest that the ASI(-) sequence interacts more tightly than the ASI(+) sequence with its binding partner, so that the ASI(-)RyR1 is more strongly inhibited (less active) than the ASI(+)RyR1. Thus the affinity of the binding partners in this inter-domain interaction may deter-mine the activities of the mature and juvenile isoforms of RyR1 and the stronger inhibition in the juvenile isoform may contribute to the myopathy in DM.
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Affiliation(s)
- Takashi Kimura
- Division of Molecular Bioscience, JCSMR (John Curtin School of Medical Research), Australian National University, P.O. Box 334, Canberra, ACT 2601, Australia.
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Robinson R, Carpenter D, Shaw MA, Halsall J, Hopkins P. Mutations inRYR1in malignant hyperthermia and central core disease. Hum Mutat 2006; 27:977-89. [PMID: 16917943 DOI: 10.1002/humu.20356] [Citation(s) in RCA: 337] [Impact Index Per Article: 18.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The RYR1 gene encodes the skeletal muscle isoform ryanodine receptor and is fundamental to the process of excitation-contraction coupling and skeletal muscle calcium homeostasis. Mapping to chromosome 19q13.2, the gene comprises 106 exons and encodes a protein of 5,038 amino acids. Mutations in the gene have been found in association with several diseases: the pharmacogenetic disorder, malignant hyperthermia (MH); and three congenital myopathies, including central core disease (CCD), multiminicore disease (MmD), and in an isolated case of a congenital myopathy characterized on histology by cores and rods. The majority of gene mutations reported are missense changes identified in cases of MH and CCD. In vitro analysis has confirmed that alteration of normal calcium homeostasis is a functional consequence of some of these changes. Genotype-phenotype correlation studies performed using data from MH and CCD patients have also suggested that mutations may be associated with a range of disease severity phenotypes. This review aims to summarize the current understanding of RYR1 mutations reported in association with MH and CCD and the present viewpoint on the use of mutation data to aid clinical diagnosis of these conditions.
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Affiliation(s)
- Rachel Robinson
- Malignant Hyperthermia Investigation Unit, St James' University Hospital, Leeds, United Kingdom.
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33
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Dulhunty AF, Beard NA, Pouliquin P, Kimura T. Novel regulators of RyR Ca2+ release channels: insight into molecular changes in genetically-linked myopathies. J Muscle Res Cell Motil 2006; 27:351-65. [PMID: 16909197 DOI: 10.1007/s10974-006-9086-1] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2006] [Accepted: 06/26/2006] [Indexed: 10/24/2022]
Abstract
There are many mutations in the ryanodine receptor (RyR) Ca2+ release channel that are implicated in skeletal muscle disorders and cardiac arrhythmias. More than 80 mutations in the skeletal RyR1 have been identified and linked to malignant hyperthermia, central core disease or multi-minicore disease, while more than 40 mutations in the cardiac RyR2 lead to ventricular arrhythmias and sudden cardiac death in patients with structurally normal hearts. These RyR mutations cause diverse changes in RyR activity which either excessively activate or block the channel in a manner that disrupts Ca2+ signalling in the muscle fibres. In a different myopathy, myotonic dystrophy (DM), a juvenile isoform of the skeletal RyR is preferentially expressed in adults. There are two regions of RyR1 that are variably spiced and developmentally regulated (ASI and ASII). The juvenile isoform (ASI(-)) is less active than the adult isoform (ASI(+)) and its over-expression in adults with DM may contribute to functional changes. Finally, mutations in an important regulator of the RyR, the Ca2+ binding protein calsequestrin (CSQ), have been linked to a disruption of Ca2+ homeostasis in cardiac myocytes that results in arrhythmias. We discuss evidence supporting the hypothesis that mutations in each of these situations alter protein/protein interactions within the RyR complex or between the RyR and its associated proteins. The disruption of these protein-protein interactions can lead either to excess Ca2+ release or reduced Ca2+ release and thus to abnormal Ca2+ homeostasis. Much of the evidence for disruption of protein-protein interactions has been provided by the actions of a group of novel RyR regulators, domain peptides with sequences that correspond to sequences within the RyR and which compete with the endogenous residues for their interaction sites.
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Affiliation(s)
- A F Dulhunty
- Division of Molecular Bioscience, JCSMR and RSC, ANU, Canberra, ACT, 2601, Australia.
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Ghelardoni S, Frascarelli S, Carnicelli V, Ronca-Testoni S, Zucchi R. Modulation of cardiac sarcoplasmic reticulum calcium release by aenosine: a protein kinase C- dependent pathway. Mol Cell Biochem 2006; 288:59-64. [PMID: 16583139 DOI: 10.1007/s11010-006-9118-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2005] [Accepted: 01/05/2006] [Indexed: 11/27/2022]
Abstract
We have already reported that A(3) adenosine receptor stimulation reduces [(3)H]-ryanodine binding and sarcoplasmic reticulum Ca(2+) release in rat heart. In the present work we have investigated the transduction pathway responsible for this effect. Isolated rat hearts were perfused for 20 min in the presence of the following substances: 100 nM N(6)-(iodobenzyl)-adenosine-5'-N-methyluronamide (IB-MECA), an A(3) adenosine agonist; 10 muM U-73122, a phospholipase C inhibitor; 2 muM chelerythrine, a protein kinase C inhibitor. At the end of perfusion, the hearts were homogenized and [(3)H]-ryanodine binding was assayed. IB-MECA produced a significant decrease in ryanodine binding, which was abolished in the presence of chelerythrine but not in the presence of U-73122. RT-PCR experiments showed that ryanodine receptor gene expression was not affected by IB-MECA. In Western blot experiments, ryanodine receptor phosphorylation on serine 2809 was not modified after perfusion with IB-MECA. We conclude that modulation of SR Ca(2+) release channel by IB-MECA is dependent on protein kinase C activation. However, in this model protein kinase C activation is not due to phospholipase C activation. In addition, changes in ryanodine receptor gene expression or direct phosphorylation of the ryanodine receptor on serine 2809 residue do not appear to occur.
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Affiliation(s)
- Sandra Ghelardoni
- Dipartimento di Scienze dell'Uomo e dell'Ambiente, University of Pisa, Pisa, Italy
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35
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Kimura T, Nakamori M, Lueck JD, Pouliquin P, Aoike F, Fujimura H, Dirksen RT, Takahashi MP, Dulhunty AF, Sakoda S. Altered mRNA splicing of the skeletal muscle ryanodine receptor and sarcoplasmic/endoplasmic reticulum Ca2+-ATPase in myotonic dystrophy type 1. Hum Mol Genet 2005; 14:2189-200. [PMID: 15972723 DOI: 10.1093/hmg/ddi223] [Citation(s) in RCA: 195] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Myotonic dystrophy type 1 (DM1) is a debilitating multisystemic disorder caused by a CTG repeat expansion in the DMPK gene. Aberrant splicing of several genes has been reported to contribute to some symptoms of DM1, but the cause of muscle weakness in DM1 and elevated Ca2+ concentrations in cultured DM muscle cells is unknown. Here, we investigated the alternative splicing of mRNAs of two major proteins of the sarcoplasmic reticulum, the ryanodine receptor 1 (RyR1) and sarcoplasmic/endoplasmic reticulum Ca2+-ATPase (SERCA) 1 or 2. The fetal variants, ASI(-) of RyR1 which lacks residue 3481-3485, and SERCA1b which differs at the C-terminal were significantly increased in skeletal muscles from DM1 patients and the transgenic mouse model of DM1 (HSA(LR)). In addition, a novel variant of SERCA2 was significantly decreased in DM1 patients. The total amount of mRNA for RyR1, SERCA1 and SERCA2 in DM1 and the expression levels of their proteins in HSA(LR) mice were not significantly different. However, heterologous expression of ASI(-) in cultured cells showed decreased affinity for [3H]ryanodine but similar Ca2+ dependency, and decreased channel activity in single-channel recording when compared with wild-type (WT) RyR1. In support of this, RyR1-knockout myotubes expressing ASI(-) exhibited a decreased incidence of Ca2+ oscillations during caffeine exposure compared with that observed for myotubes expressing WT-RyR1. We suggest that aberrant splicing of RyR1 and SERCA1 mRNAs might contribute to impaired Ca2+ homeostasis in DM1 muscle.
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Affiliation(s)
- Takashi Kimura
- Division of Molecular Bioscience, John Curtin School of Medical Research, Australian National University, PO Box 334, Canberra ACT 2601, Australia
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36
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Abstract
Intracellular calcium release channels are present on sarcoplasmic and endoplasmic reticuli (SR, ER) of all cell types. There are two classes of these channels: ryanodine receptors (RyR) and inositol 1,4,5-trisphosphate receptors (IP3R). RyRs are required for excitation-contraction (EC) coupling in striated (cardiac and skeletal) muscles. RyRs are made up of macromolecular signaling complexes that contain large cytoplasmic domains, which serve as scaffolds for proteins that regulate the function of the channel. These regulatory proteins include calstabin1/calstabin2 (FKBP12/FKBP12.6), a 12/12.6 kDa subunit that stabilizes the closed state of the channel and prevents aberrant calcium leak from the SR. Kinases and phosphatases are targeted to RyR2 channels and modulate RyR2 function in response to extracellular signals. In the classic fight or flight stress response, phosphorylation of RyR channels by protein kinase A reduces the affinity for calstabin and activates the channels leading to increased SR calcium release. In heart failure, a cardiac insult causes a mismatch between blood supply and metabolic demands of organs. The chronically activated fight or flight response leads to leaky channels, altered calcium signaling, and contractile dysfunction and cardiac arrhythmias.
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Affiliation(s)
- Xander H T Wehrens
- Department of Physiology and Cellular Biophysics, Center for Molecular Cardiology, Department of Medicine, Columbia University College of Physicians and Surgeons, New York 10032, USA.
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37
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Brini M. Ryanodine receptor defects in muscle genetic diseases. Biochem Biophys Res Commun 2004; 322:1245-55. [PMID: 15336972 DOI: 10.1016/j.bbrc.2004.08.029] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2004] [Indexed: 11/22/2022]
Abstract
Ryanodine receptor (RyR), a homotetrameric Ca2+ release channel, is one of the main actors in the generation of Ca2+ signals that trigger muscle contraction. Three genes encode three isoforms of RyRs, which have tissue-restricted distribution. RyR1 and RyR2 are typical of muscle cells, with RyR1 originally considered the skeletal muscle type and RyR2 the cardiac type. However, RyR1 and RyR2 have recently been found in numerous other cell types, including, for instance, peripheral B and T lymphocytes. In contrast, RyR3 is widely distributed among cells. RyR1 and RyR2 are localized in a specialized portion of the sarcoplasmic reticulum (SR), the terminal cisternae, which is the portion of the SR Ca2+ store that releases Ca2+ to control the process of muscle contraction. A specific role for RyR3 has not yet been established: probably, its co-expression with the other RyR isoforms contributes to qualitatively modulate Ca2+-dependent processes in muscle cells and in neurons. Several mutations in the genes encoding RyR1 and RyR2 have been identified in autosomal dominant diseases of skeletal and cardiac muscle, such as malignant hyperthermia (MH), central core disease (CCD), catecholaminergic polymorphic ventricular tachycardia (CPVT), and arrhythmogenic right ventricular dysplasia type 2 (ARVD2). More recently, CCD cases with recessive inheritance have also been described. MH is a pharmacogenetic disease, but the others manifest as congenital myopathies. Even if their clinical phenotypes are well established, particularly in skeletal muscle, the molecular mechanisms that generate the conditions are not clear. A number of studies on cellular models have attempted to elucidate the molecular defects associated with the different mutations, but the problem of understanding how mutations in the same gene generate such an array of diverse pathological traits and diseases of widely different degrees of severity is still open. This review will consider the molecular and cellular effects of RyR mutations, summarizing recent data in the literature on Ca2+ dysregulation, which may lead to a better understanding of the functioning of RyRs.
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Affiliation(s)
- Marisa Brini
- Department of Biochemistry and Department of Experimental Veterinary Sciences, University of Padua, Viale G. Colombo 3, 35121 Padua, Italy
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38
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Chiang W, Allison CP, Linz JE, Strasburg GM. Identification of two alphaRYR alleles and characterization of alphaRYR transcript variants in turkey skeletal muscle. Gene 2004; 330:177-84. [PMID: 15087137 DOI: 10.1016/j.gene.2004.01.023] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2003] [Revised: 01/13/2004] [Accepted: 01/26/2004] [Indexed: 11/16/2022]
Abstract
We hypothesized that a mutation in the turkey skeletal muscle ryanodine receptor alpha isoform (alphaRYR) underlies turkey meat quality problems which are strikingly similar to pale, soft, exudative (PSE) pork. RT-PCR analysis of turkey alphaRYR mRNA covering amino acids 376 to 615 (numbered according to the human sequence) revealed at least three transcript variants. One transcript was homologous to the mammalian skeletal muscle RYR1 sequence in this region. The second transcript variant (AS-81) was characterized by the absence of 81 bases located at the beginning of exon 13, while the third transcript variant (AS-193) carried a deletion of 193 bases, corresponding to the entire exon 13. Two alphaRYR genomic DNA alleles (alphaRYR-I and alphaRYR-II) carrying the region of deletions in the turkey cDNA sequences were identified. Nucleotide sequence analysis demonstrated that the two alleles are identical in exon sequences but different in intron sequences. Comparison of genomic and cDNA sequences indicated that both AS-81 and AS-193 transcript variants probably arose via alternative splicing. Consistent with this mechanism, the last eight nucleotides of the 81 bases form a consensus sequence for a splice acceptor site. Both alleles could give rise to the AS-81 and AS-193 transcript variants via alternative splicing. Birds homozygous for alphaRYR-II tended to have superior meat quality indicators including significantly higher muscle pH at 15-min post mortem and lower muscle exudate at 24-h post mortem, compared to birds homozygous for alphaRYR-I.
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Affiliation(s)
- Wen Chiang
- Department of Food Science and Human Nutrition, Michigan State University, R3365 Anthony Hall, East Lansing, MI 48824, USA.
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39
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Payne AM, Zheng Z, González E, Wang ZM, Messi ML, Delbono O. External Ca(2+)-dependent excitation--contraction coupling in a population of ageing mouse skeletal muscle fibres. J Physiol 2004; 560:137-55. [PMID: 15297570 PMCID: PMC1665204 DOI: 10.1113/jphysiol.2004.067322] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
In the present work, we investigate whether changes in excitation-contraction (EC) coupling mode occur in skeletal muscles from ageing mammals by examining the dependence of EC coupling on extracellular Ca(2+). Single intact muscle fibres from flexor digitorum brevis muscles from young (2-6 months) and old (23-30 months) mice were subjected to tetanic contractile protocols in the presence and absence of external Ca(2+). Contractile experiments in the absence of external Ca(2+) show that about half of muscle fibres from old mice are dependent upon external Ca(2+) for maintaining maximal tetanic force output, while young fibres are not. Decreased force in the absence of external Ca(2+) was not due to changes in charge movement as revealed by whole-cell patch-clamp experiments. Ca(2+) transients, measured by fluo-4 fluorescence, declined in voltage-clamped fibres from old mice in the absence of external Ca(2+). Similarly, Ca(2+) transients declined in parallel with tetanic contractile force in single intact fibres. Examination of inward Ca(2+) current and of mRNA and protein assays suggest that these changes in EC coupling mode are not due to shifts in dihydropyridine receptor (DHPR) and/or ryanodine receptor (RyR) isoforms. These results indicate that a change in EC coupling mode occurs in a population of fibres in ageing skeletal muscle, and is responsible for the age-related dependence on extracellular Ca(2+).
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Affiliation(s)
- Anthony Michael Payne
- Department of Physiology and Pharmacology, Wake Forest University School of Medicine, Medical Center Boulevard, Winston-Salem, NC 27157, USA.
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Dulhunty AF, Pouliquin P. What we don't know about the structure of ryanodine receptor calcium release channels. Clin Exp Pharmacol Physiol 2003; 30:713-23. [PMID: 14516409 DOI: 10.1046/j.1440-1681.2003.03904.x] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
1. The ryanodine receptor (RyR) is the Ca2+ release channel in the sarcoplamic reticulum of skeletal and cardiac muscle and is essential for respiration and heart beat. The RyR channel releases Ca2+ from intracellular stores in a variety of other cell types, where it normally coexists with the inositiol 1,4,5-trisphosphate receptor (IP3R). The RyR and IP3R, forming a superfamily of homotetrameric ligand-gated intracellular Ca2+ channels, serve discrete functions: they can be located in independent Ca2+ stores with different activation mechanisms and can be coupled to different signalling pathways. 2. Although functional characteristics of the RyR have been investigated intensely, there remain major gaps in our knowledge about the structure of the protein, its ion-conducting pore, its ligand-binding sites and sites supporting the many protein/protein interactions that underlie the in vivo function of the channel. 3. Of particular importance are the transmembrane segments that form the membrane-spanning domain of the protein and the pore, define the conductance and selectivity of the channel and dictate the cytoplasmic and luminal domains and the overall protein structure. Hydropathy profiles predict between four and 12 transmembrane segments. One popular model shows four transmembrane segments in the C-terminal one-tenth of the protein. However, there is substantial evidence for a larger number of membrane-spanning segments located in both the C-terminal and central parts of the protein. 4. A model of the RyR pore based on the Streptomyces lividans KcsA channel structure is presented. Protein/protein interactions between the RyR and other regulatory proteins, as well as within the RyR subunit, are discussed.
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Affiliation(s)
- Angela F Dulhunty
- The Muscle Research Group, John Curtin School of Medical Research, Australian National University, Canberra, Australian Capital Territory, Australia.
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Vasiliev AM, Vasilenko RN, Kulikova NL, Andreev SM, Chikileva IO, Puchkova GY, Kosarev IV, Khodyakova AV, Khlebnikov VS, Ptitsyn LR, Shcherbakov GY, Uversky VN, DuBuske LM, Abramov VM. Structural and functional properties of IL-4delta2, an alternative splice variant of human IL-4. J Proteome Res 2003; 2:273-81. [PMID: 12814267 DOI: 10.1021/pr025586y] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Structural and functional properties of recombinant IL-4delta2, a naturally occurring splice variant of human IL-4 with a deletion of the loop region 22-37, have been analyzed. IL-4delta2 has alpha-helical structure and most likely preserves the "up-up-down-down" topology typical of the four-helix-bundle cytokines. IL-4delta2 interacts specifically with the alpha chain of IL-4R and competes effectively with IL-4 for the common binding sites. Thus, IL-4delta2 may act as a regulator of the cytokine net, being the natural antagonist of IL-4.
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Affiliation(s)
- Anatoly M Vasiliev
- Institute of Immunological Engineering, 142380 Lyubuchany, Moscow Region, Russia
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42
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Abstract
The family of ryanodine receptor (RyR) genes encodes three highly related Ca(2+)-release channels: RyR1, RyR2 and RyR3. RyRs are known as the Ca(2+)-release channels that participate to the mechanism of excitation-contraction coupling in striated muscles, but they are also expressed in many other cell types. Actually, in several cells two or three RyR isoforms can be co-expressed and interactive feedbacks among them may be important for generation of intracellular Ca(2+) signals and regulation of specific cellular functions. Important developments have been obtained in understanding the biochemical complexity underlying the process of Ca(2+) release through RyRs. The 3-D structure of these large molecules has been obtained and some regulatory regions have been mapped within these 3-D reconstructions. Recent studies have clarified the role of protein kinases and phosphatases that, by physically interacting with RyRs, appear to play a role in the regulation of these Ca(2+)-release channels. These and other recent advancements in understanding RyR biology will be the object of this review.
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Affiliation(s)
- Daniela Rossi
- Molecular Medicine Section, Department of Neuroscience, University of Siena, via Aldo Moro 5, Siena, Italy
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43
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Abstract
The ryanodine receptors (RyRs) are a family of Ca2+ release channels found on intracellular Ca2+ storage/release organelles. The RyR channels are ubiquitously expressed in many types of cells and participate in a variety of important Ca2+ signaling phenomena (neurotransmission, secretion, etc.). In striated muscle, the RyR channels represent the primary pathway for Ca2+ release during the excitation-contraction coupling process. In general, the signals that activate the RyR channels are known (e.g., sarcolemmal Ca2+ influx or depolarization), but the specific mechanisms involved are still being debated. The signals that modulate and/or turn off the RyR channels remain ambiguous and the mechanisms involved unclear. Over the last decade, studies of RyR-mediated Ca2+ release have taken many forms and have steadily advanced our knowledge. This robust field, however, is not without controversial ideas and contradictory results. Controversies surrounding the complex Ca2+ regulation of single RyR channels receive particular attention here. In addition, a large body of information is synthesized into a focused perspective of single RyR channel function. The present status of the single RyR channel field and its likely future directions are also discussed.
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Affiliation(s)
- Michael Fill
- Department of Physiology, Loyola University Chicago, Maywood, Illinois 60153, USA
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44
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Dulhunty AF, Haarmann CS, Green D, Laver DR, Board PG, Casarotto MG. Interactions between dihydropyridine receptors and ryanodine receptors in striated muscle. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2002; 79:45-75. [PMID: 12225776 DOI: 10.1016/s0079-6107(02)00013-5] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Excitation-contraction coupling in both skeletal and cardiac muscle depends on structural and functional interactions between the voltage-sensing dihydropyridine receptor L-type Ca(2+) channels in the surface/transverse tubular membrane and ryanodine receptor Ca(2+) release channels in the sarcoplasmic reticulum membrane. The channels are targeted to either side of a narrow junctional gap that separates the external and internal membrane systems and are arranged so that bi-directional structural and functional coupling can occur between the proteins. There is strong evidence for a physical interaction between the two types of channel protein in skeletal muscle. This evidence is derived from studies of excitation-contraction coupling in intact myocytes and from experiments in isolated systems where fragments of the dihydropyridine receptor can bind to the ryanodine receptors in sarcoplasmic reticulum vesicles or in lipid bilayers and alter channel activity. Although micro-regions that participate in the functional interactions have been identified in each protein, the role of these regions and the molecular nature of the protein-protein interaction remain unknown. The trigger for Ca(2+) release through ryanodine receptors in cardiac muscle is a Ca(2+) influx through the L-type Ca(2+) channel. The Ca(2+) entering through the surface membrane Ca(2+) channels flows directly onto underlying ryanodine receptors and activates the channels. This was thought to be a relatively simple system compared with that in skeletal muscle. However, complexities are emerging and evidence has now been obtained for a bi-directional physical coupling between the proteins in cardiac as well as skeletal muscle. The molecular nature of this coupling remains to be elucidated.
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Affiliation(s)
- A F Dulhunty
- John Curtin School of Medical Research, Australian National University, P.O. Box 334 2601 Canberra, Australia.
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45
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Münch G, Bölck B, Sugaru A, Brixius K, Bloch W, Schwinger RH. Increased expression of isoform 1 of the sarcoplasmic reticulum Ca(2+)-release channel in failing human heart. Circulation 2001; 103:2739-44. [PMID: 11390346 DOI: 10.1161/01.cir.103.22.2739] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND The sarcoplasmic reticulum (SR) Ca(2+)-release channel plays a key role in the excitation-contraction coupling of cardiac myocytes. Because respective alterations have been reported in human heart failure, we investigated isoform expression of the SR Ca(2+)-release channel in human hearts from patients with terminal heart failure (dilated cardiomyopathy [DCM], n=8) and nonfailing organ donors (NF, n=8). METHODS AND RESULTS Expression of mRNA of SR Ca(2+)-release channel isoforms in isolated human cardiomyocytes and myocardial tissue was analyzed by reverse-transcription polymerase chain reaction. Protein expression was quantified in myocardial tissue with [(3)H]-ryanodine binding and with Western blots, expressed as densitometric units per microgram of protein (DU), and cellular localization was visualized with immunohistochemistry. We found mRNA expression of isoforms 1, 2, and 3 in cardiomyocytes and myocardial tissue both in NF and DCM. Total SR Ca(2+)-release channel protein expression in NF (B(max) 2.16+/-0.43 pmol/mg protein) and in DCM (B(max) 2.33+/-0.22 pmol/mg protein) myocardium was unchanged. Expression of isoform 1 of the SR Ca(2+)-release channel was significantly (P=0.0037) increased in DCM myocardium (NF 1.97+/-0.25 versus DCM 3.37+/-0.31 DU), whereas protein expression of isoform 2 (NF 14.62+/-0.87 versus DCM 13.52+/-0.43 DU) and isoform 3 (NF 1.39+/-0.13 versus DCM 1.35+/-0.19 DU) was unchanged. All 3 isoforms of the protein could be localized in human ventricular myocytes with fluorescence immunohistochemistry. CONCLUSIONS All 3 isoforms of the SR Ca(2+)-release channel were determined in human ventricular cardiomyocytes. Increased expression of isoform 1 of the SR Ca(2+)-release channel could contribute to impaired excitation-contraction coupling in human heart failure.
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Affiliation(s)
- G Münch
- Laboratory of Muscle Research and Molecular Cardiology, Klinik III für Innere Medizin, University of Cologne, Cologne, Germany
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46
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Wild JS, Giri SN, Moore R, Pessah IN. Characterization of [(3)H]ryanodine binding sites in mammalian lung. Arch Biochem Biophys 2000; 379:109-18. [PMID: 10864448 DOI: 10.1006/abbi.2000.1850] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The ryanodine-sensitive calcium channels, also called ryanodine receptors, are intracellular Ca(2+)-release channels that have been shown to bind the neutral plant alkaloid ryanodine with nanomolar affinity. The activity of the skeletal muscle (RyR1), cardiac muscle (RyR2), and brain (RyR3) ryanodine receptor isoforms have been shown to be highly regulated by physiological factors including pH, temperature, and ionic strength; endogenous compounds including Ca(2+), Mg(2+), and adenosine triphosphate (ATP); and pharmacological agents including caffeine, ruthenium red, and neomycin. RyR3 is reportedly expressed in diverse tissues including lung; however, specific [(3)H]ryanodine binding sites in mammalian lung tissue have not been characterized. In this study, hamster lung ryanodine binding proteins were shown to specifically bind [(3)H]ryanodine with an affinity similar to that of RyR isoforms found in other tissues and this binding was shown to be sensitive to Ca(2+) concentration, stimulation by caffeine and spermine, and inhibition by Mg(2+), ruthenium red, and neomycin. The solubilized, intact ryanodine binding protein from hamster lung demonstrated approximately the same 30S sedimentation coefficient as RyR1 and RyR2, but a putative ryanodine receptor subunit from hamster lung was not found to cross-react with antibodies specific for the three known isoforms. We conclude that the hamster lung ryanodine binding protein demonstrates sedimentation and binding characteristics that are similar to those of the known RyR isoforms, but may exhibit antigenic dissimilarity from the typical RyR isoforms found in muscle and brain.
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Affiliation(s)
- J S Wild
- Department of Molecular Biosciences, School of Veterinary Medicine, Davis, California, 95616, USA
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47
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Palnitkar SS, Bin B, Jimenez LS, Morimoto H, Williams PG, Paul-Pletzer K, Parness J. [3H]Azidodantrolene: synthesis and use in identification of a putative skeletal muscle dantrolene binding site in sarcoplasmic reticulum. J Med Chem 1999; 42:1872-80. [PMID: 10354395 DOI: 10.1021/jm9805079] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Dantrolene sodium is a medically important hydantoin derivative that interferes with release of Ca2+ from intracellular stores of skeletal muscle by an unknown mechanism. Identification of the molecular target of dantrolene would greatly aid in understanding both the mechanism of action of the drug and the dynamics of intracellular Ca2+ release in muscle. [3H]Azidodantrolene was designed and synthesized as a photoaffinity analogue in order to identify a putative dantrolene receptor in skeletal muscle. Introduction of 1 mole-atom of tritium into aldehyde 5b was required during radioligand synthesis in order to ensure high enough specific activity for detection of photo-cross-linked proteins by fluorographic methods. This was accomplished by reduction of ester 3 with custom synthesized, 100% tritium-labeled lithium triethylborotritide, followed by oxidation to 5b by manganese(IV) oxide. Compound 6b was demonstrated to be >/=95% tritium-labeled at the imine position by NMR spectroscopy, and the specific radioactivity of [3H]azidodantrolene sodium was empirically determined by HPLC and liquid scintillation counting to be 24.4 Ci/mmol, approximately 85% of theoretical maximum. [3H]Azidodantrolene was found to be pharmacologically active in ligand-receptor binding studies with skeletal muscle sarcoplasmic reticulum membranes. Photo-cross-linking experiments analyzed by SDS-PAGE and tritium fluorography have identified a approximately 160-kDa specifically labeled protein as the putative, intracellular, skeletal muscle dantrolene receptor. This photolabeled protein comigrates with a protein in Western blots immunologically cross-reactive to a polyclonal anti-rabbit skeletal muscle ryanodine receptor antibody. Thus, the putative dantrolene receptor may be related to the skeletal muscle ryanodine receptor.
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Affiliation(s)
- S S Palnitkar
- Departments of Anesthesia, Pharmacology, and Pediatrics, UMDNJ-Robert Wood Johnson Medical School, New Brunswick, New Jersey 08901, USA. 08855, National Tritium Labelling Facil
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48
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Korte A, Möricke A, Beyermann B, Köchling J, Taube T, Kebelmann-Betzing C, Henze G, Seeger K. Extensive alternative splicing of interleukin-7 in malignant hematopoietic cells: implication of distinct isoforms in modulating IL-7 activity. J Interferon Cytokine Res 1999; 19:495-503. [PMID: 10386862 DOI: 10.1089/107999099313947] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Interleukin-7 (IL-7) plays a pivotal role in early stages of normal B and T cell development. In addition, IL-7 stimulates the proliferation of both antitumor reactive cells and a number of T and B cell malignancies, underlining its significance for leukemogenesis. However, its exact role in the process of pathologic maturation of lymphocytes and regulation of the immune response is not completely understood. As alternative splicing of pre-mRNA has been shown to be involved in the control of gene expression, and splicing-derived protein isoforms with antagonistic activity have been found, we assessed the mRNA-expression of IL-7 and its previously described alternative splice variant lacking exon 4, IL-7delta4, in leukemic cells from children with acute lymphoblastic leukemia (ALL). PCR of full-length IL-7 cDNA enabling the competitive amplification of both variants led to the amplification of diverse unexpected PCR products. The sequence data demonstrated the existence of three additional in-frame splice variants resulting from exon skipping of exon 3 or exon 5 or both in combination with exon 4. We named these IL-7delta3/4, IL-7delta4/5, and IL-7delta3/4/5. Furthermore, three out-of-frame splice variants were identified, IL-7(-56bpExon2), IL-7delta4(-56bpExon2), and IL-7delta3/4/5(-56bpExon2), in which, in addition to the aforementioned exon skipping, 56 bp of the 3' end of exon 2 are omitted. Our results led us to assume that splicing-derived IL-7 isoforms play a potential role in modulating IL-7-mediated biologic effects. Further studies are required to clarify the significance of the diverse IL-7 protein isoforms for the regulation of IL-7 function and the pathogenesis of leukemia.
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Affiliation(s)
- A Korte
- Department of Pediatric Oncology/Hematology, Charité Universitäsklinikum, Humboldt-University at Berlin, Germany.
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49
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Shoshan-Barmatz V, Ashley RH. The structure, function, and cellular regulation of ryanodine-sensitive Ca2+ release channels. INTERNATIONAL REVIEW OF CYTOLOGY 1998; 183:185-270. [PMID: 9666568 DOI: 10.1016/s0074-7696(08)60145-x] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
The fundamental biological process of Ca2+ signaling is known to be important in most eukaryotic cells, and inositol 1,2,5-trisphosphate and ryanodine receptors, intracellular Ca2+ release channels encoded by two distantly related gene families, are central to this phenomenon. Ryanodine receptors in the sarcoplasmic reticulum of skeletal and cardiac muscle have a predominant role in excitation-contraction coupling, but the channels are also present in the endoplasmic reticulum of noncontractile tissues including the central nervous system and the immune system. In all, three highly homologous ryanodine receptor isoforms have been identified, all very large proteins which assemble as (homo)tetramers of approximately 2 MDa. They contain large cytoplasmically disposed regulatory domains and are always associated with other structural or regulatory proteins, including calmodulin and immunophilins, which can have marked effects on channel function. The type 1 isoform in skeletal muscle is electromechanically coupled to surface membrane voltage sensors, whereas the remaining isoforms appear to be activated solely by endogenous cytoplasmic second messengers or other ligands, including Ca2+ itself ("Ca(2+)-induced Ca2+ release"). This review concentrates on ryanodine receptor structure-function relationships as probed by a variety of methods and on the molecular mechanisms of channel modulation at the cellular level (including evidence for the regulation of gene expression and transcription). It also touches on the relevance of ryanodine receptors to complex cellular functions and disease.
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Affiliation(s)
- V Shoshan-Barmatz
- Department of Life Sciences, Ben-Gurion University, Beer-Sheva, Israel
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50
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Martin C, Chapman KE, Seckl JR, Ashley RH. Partial cloning and differential expression of ryanodine receptor/calcium-release channel genes in human tissues including the hippocampus and cerebellum. Neuroscience 1998; 85:205-16. [PMID: 9607712 DOI: 10.1016/s0306-4522(97)00612-x] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Cellular Ca2+ signalling is an important factor in the control of neuronal metabolism and electrical activity. Although the roles of Ca2+-release channels are well established for skeletal and cardiac muscle, less is known about their expression and roles in the central nervous system, especially in the human brain. We have isolated partial complementary DNAs derived from the human ryanodine receptor Ca2+-release channel genes (ryr1, ryr2 and ryr3), and examined their expression in the human hippocampus and cerebellum. For comparison, we have included in our analysis an inositol trisphosphate Ca2+-release channel type I complementary RNA probe. All four messenger RNAs show widespread distribution in the human hippocampus, where ryr2 is the most abundant isoform, and all four are expressed in the human cerebellum. However, striking differences were seen between ryr and inositol trisphosphate Ca2+-release channel type I complementary RNA expression in the cerebellum, with inositol trisphosphate Ca2+-release channel type I messenger RNA being largely restricted to, and very highly expressed, in Purkinje cells, whereas ryr1, ryr2 and ryr3 were all expressed predominantly in the granular layer. The widespread expression of ryr isoforms in the human hippocampus and cerebellum suggests that ryanodine receptor proteins may have a central role in Ca2+ signalling and Ca2+ homeostasis in the human central nervous system. These may include roles in fundamental processes like synaptic plasticity. Furthermore, these Ca2+-release channels may be involved in pathogenic processes such as excitotoxicity, where excessive rises in intracellular Ca2+ concentration mediate neuronal cell death.
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Affiliation(s)
- C Martin
- Department of Biochemistry, University of Edinburgh, UK
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