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Nayak AR, Rangubpit W, Will AH, Hu Y, Castro-Hartmann P, Lobo JJ, Dryden K, Lamb GD, Sompornpisut P, Samsó M. Interplay between Mg 2+ and Ca 2+ at multiple sites of the ryanodine receptor. Nat Commun 2024; 15:4115. [PMID: 38750013 PMCID: PMC11096358 DOI: 10.1038/s41467-024-48292-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2023] [Accepted: 04/26/2024] [Indexed: 05/18/2024] Open
Abstract
RyR1 is an intracellular Ca2+ channel important in excitable cells such as neurons and muscle fibers. Ca2+ activates it at low concentrations and inhibits it at high concentrations. Mg2+ is the main physiological RyR1 inhibitor, an effect that is overridden upon activation. Despite the significance of Mg2+-mediated inhibition, the molecular-level mechanisms remain unclear. In this work we determined two cryo-EM structures of RyR1 with Mg2+ up to 2.8 Å resolution, identifying multiple Mg2+ binding sites. Mg2+ inhibits at the known Ca2+ activating site and we propose that the EF hand domain is an inhibitory divalent cation sensor. Both divalent cations bind to ATP within a crevice, contributing to the precise transmission of allosteric changes within the enormous channel protein. Notably, Mg2+ inhibits RyR1 by interacting with the gating helices as validated by molecular dynamics. This structural insight enhances our understanding of how Mg2+ inhibition is overcome during excitation.
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Affiliation(s)
- Ashok R Nayak
- Department of Physiology and Biophysics, Virginia Commonwealth University, Richmond, VA, USA
| | - Warin Rangubpit
- Department of Chemistry, Faculty of Science, Chulalongkorn University, Bangkok, Thailand
| | - Alex H Will
- Department of Physiology and Biophysics, Virginia Commonwealth University, Richmond, VA, USA
| | - Yifan Hu
- Department of Physiology and Biophysics, Virginia Commonwealth University, Richmond, VA, USA
| | - Pablo Castro-Hartmann
- Department of Physiology and Biophysics, Virginia Commonwealth University, Richmond, VA, USA
- ThermoFisher Scientific, Cambridge, UK
| | - Joshua J Lobo
- Department of Physiology and Biophysics, Virginia Commonwealth University, Richmond, VA, USA
| | - Kelly Dryden
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, VA, USA
- Department of Chemistry and Biochemistry, UC Santa Barbara, Santa Barbara, CA, USA
| | - Graham D Lamb
- Department of Microbiology, Anatomy, Physiology and Pharmacology, La Trobe University, Melbourne, VIC, Australia
| | - Pornthep Sompornpisut
- Department of Chemistry, Faculty of Science, Chulalongkorn University, Bangkok, Thailand.
| | - Montserrat Samsó
- Department of Physiology and Biophysics, Virginia Commonwealth University, Richmond, VA, USA.
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2
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Woll KA, Van Petegem F. Calcium Release Channels: Structure and Function of IP3 Receptors and Ryanodine Receptors. Physiol Rev 2021; 102:209-268. [PMID: 34280054 DOI: 10.1152/physrev.00033.2020] [Citation(s) in RCA: 79] [Impact Index Per Article: 26.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Ca2+-release channels are giant membrane proteins that control the release of Ca2+ from the endoplasmic and sarcoplasmic reticulum. The two members, ryanodine receptors (RyRs) and inositol-1,4,5-trisphosphate Receptors (IP3Rs), are evolutionarily related and are both activated by cytosolic Ca2+. They share a common architecture, but RyRs have evolved additional modules in the cytosolic region. Their massive size allows for the regulation by tens of proteins and small molecules, which can affect the opening and closing of the channels. In addition to Ca2+, other major triggers include IP3 for the IP3Rs, and depolarization of the plasma membrane for a particular RyR subtype. Their size has made them popular targets for study via electron microscopic methods, with current structures culminating near 3Å. The available structures have provided many new mechanistic insights int the binding of auxiliary proteins and small molecules, how these can regulate channel opening, and the mechanisms of disease-associated mutations. They also help scrutinize previously proposed binding sites, as some of these are now incompatible with the structures. Many questions remain around the structural effects of post-translational modifications, additional binding partners, and the higher-order complexes these channels can make in situ. This review summarizes our current knowledge about the structures of Ca2+-release channels and how this informs on their function.
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Affiliation(s)
- Kellie A Woll
- Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, BC, Canada
| | - Filip Van Petegem
- Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, BC, Canada
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3
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Zheng W, Wen H. Investigating dual Ca 2+ modulation of the ryanodine receptor 1 by molecular dynamics simulation. Proteins 2020; 88:1528-1539. [PMID: 32557910 DOI: 10.1002/prot.25971] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2019] [Revised: 05/26/2020] [Accepted: 06/14/2020] [Indexed: 11/09/2022]
Abstract
The ryanodine receptors (RyR) are essential to calcium signaling in striated muscles. A deep understanding of the complex Ca2+ -activation/inhibition mechanism of RyRs requires detailed structural and dynamic information for RyRs in different functional states (eg, with Ca2+ bound to activating or inhibitory sites). Recently, high-resolution structures of the RyR isoform 1 (RyR1) were solved by cryo-electron microscopy, revealing the location of a Ca2+ binding site for activation. Toward elucidating the Ca2+ -modulation mechanism of RyR1, we performed extensive molecular dynamics simulation of the core RyR1 structure in the presence and absence of activating and solvent Ca2+ (total simulation time is >5 μs). In the presence of solvent Ca2+ , Ca2+ binding to the activating site enhanced dynamics of RyR1 with higher inter-subunit flexibility, asymmetric inter-subunit motions, outward domain motions and partial pore dilation, which may prime RyR1 for subsequent channel opening. In contrast, the solvent Ca2+ alone reduced dynamics of RyR1 and led to inward domain motions and pore contraction, which may cause inhibition. Combining our simulation with the map of disease mutation sites in RyR1, we constructed a wiring diagram of key domains coupled via specific hydrogen bonds involving the mutation sites, some of which were modulated by Ca2+ binding. The structural and dynamic information gained from this study will inform future mutational and functional studies of RyR1 activation and inhibition by Ca2+ .
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Affiliation(s)
- Wenjun Zheng
- Department of Physics, University at Buffalo, Buffalo, New York, USA
| | - Han Wen
- Department of Physics, University at Buffalo, Buffalo, New York, USA
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4
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Lawal TA, Wires ES, Terry NL, Dowling JJ, Todd JJ. Preclinical model systems of ryanodine receptor 1-related myopathies and malignant hyperthermia: a comprehensive scoping review of works published 1990-2019. Orphanet J Rare Dis 2020; 15:113. [PMID: 32381029 PMCID: PMC7204063 DOI: 10.1186/s13023-020-01384-x] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2019] [Accepted: 04/14/2020] [Indexed: 02/07/2023] Open
Abstract
BACKGROUND Pathogenic variations in the gene encoding the skeletal muscle ryanodine receptor (RyR1) are associated with malignant hyperthermia (MH) susceptibility, a life-threatening hypermetabolic condition and RYR1-related myopathies (RYR1-RM), a spectrum of rare neuromuscular disorders. In RYR1-RM, intracellular calcium dysregulation, post-translational modifications, and decreased protein expression lead to a heterogenous clinical presentation including proximal muscle weakness, contractures, scoliosis, respiratory insufficiency, and ophthalmoplegia. Preclinical model systems of RYR1-RM and MH have been developed to better understand underlying pathomechanisms and test potential therapeutics. METHODS We conducted a comprehensive scoping review of scientific literature pertaining to RYR1-RM and MH preclinical model systems in accordance with the PRISMA Scoping Reviews Checklist and the framework proposed by Arksey and O'Malley. Two major electronic databases (PubMed and EMBASE) were searched without language restriction for articles and abstracts published between January 1, 1990 and July 3, 2019. RESULTS Our search yielded 5049 publications from which 262 were included in this review. A majority of variants tested in RYR1 preclinical models were localized to established MH/central core disease (MH/CCD) hot spots. A total of 250 unique RYR1 variations were reported in human/rodent/porcine models with 95% being missense substitutions. The most frequently reported RYR1 variant was R614C/R615C (human/porcine total n = 39), followed by Y523S/Y524S (rabbit/mouse total n = 30), I4898T/I4897T/I4895T (human/rabbit/mouse total n = 20), and R163C/R165C (human/mouse total n = 18). The dyspedic mouse was utilized by 47% of publications in the rodent category and its RyR1-null (1B5) myotubes were transfected in 23% of publications in the cellular model category. In studies of transfected HEK-293 cells, 57% of RYR1 variations affected the RyR1 channel and activation core domain. A total of 15 RYR1 mutant mouse strains were identified of which ten were heterozygous, three were compound heterozygous, and a further two were knockout. Porcine, avian, zebrafish, C. elegans, canine, equine, and drosophila model systems were also reported. CONCLUSIONS Over the past 30 years, there were 262 publications on MH and RYR1-RM preclinical model systems featuring more than 200 unique RYR1 variations tested in a broad range of species. Findings from these studies have set the foundation for therapeutic development for MH and RYR1-RM.
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Affiliation(s)
- Tokunbor A Lawal
- National Institute of Nursing Research, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Emily S Wires
- National Institute on Drug Abuse, National Institutes of Health, Baltimore, MD, USA
| | - Nancy L Terry
- National Institutes of Health Library, National Institutes of Health, Bethesda, MD, USA
| | - James J Dowling
- Program for Genetics and Genome Biology, Hospital for Sick Children, Toronto, Ontario, Canada
| | - Joshua J Todd
- National Institute of Nursing Research, National Institutes of Health, Bethesda, MD, 20892, USA.
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Yamaguchi N. Molecular Insights into Calcium Dependent Regulation of Ryanodine Receptor Calcium Release Channels. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2019; 1131:321-336. [DOI: 10.1007/978-3-030-12457-1_13] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
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6
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Meissner G. The structural basis of ryanodine receptor ion channel function. J Gen Physiol 2017; 149:1065-1089. [PMID: 29122978 PMCID: PMC5715910 DOI: 10.1085/jgp.201711878] [Citation(s) in RCA: 147] [Impact Index Per Article: 21.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2017] [Accepted: 10/12/2017] [Indexed: 01/25/2023] Open
Abstract
Large-conductance Ca2+ release channels known as ryanodine receptors (RyRs) mediate the release of Ca2+ from an intracellular membrane compartment, the endo/sarcoplasmic reticulum. There are three mammalian RyR isoforms: RyR1 is present in skeletal muscle; RyR2 is in heart muscle; and RyR3 is expressed at low levels in many tissues including brain, smooth muscle, and slow-twitch skeletal muscle. RyRs form large protein complexes comprising four 560-kD RyR subunits, four ∼12-kD FK506-binding proteins, and various accessory proteins including calmodulin, protein kinases, and protein phosphatases. RyRs share ∼70% sequence identity, with the greatest sequence similarity in the C-terminal region that forms the transmembrane, ion-conducting domain comprising ∼500 amino acids. The remaining ∼4,500 amino acids form the large regulatory cytoplasmic "foot" structure. Experimental evidence for Ca2+, ATP, phosphorylation, and redox-sensitive sites in the cytoplasmic structure have been described. Exogenous effectors include the two Ca2+ releasing agents caffeine and ryanodine. Recent work describing the near atomic structures of mammalian skeletal and cardiac muscle RyRs provides a structural basis for the regulation of the RyRs by their multiple effectors.
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Affiliation(s)
- Gerhard Meissner
- Department of Biochemistry and Biophysics, School of Medicine, University of North Carolina, Chapel Hill, NC
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7
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Abstract
Ca2+ is a ubiquitous intracellular messenger that controls diverse cellular functions but can become toxic and cause cell death. Selective control of specific targets depends on spatiotemporal patterning of the calcium signal and decoding it by multiple, tunable, and often strategically positioned Ca2+-sensing elements. Ca2+ is detected by specialized motifs on proteins that have been biochemically characterized decades ago. However, the field of Ca2+ sensing has been reenergized by recent progress in fluorescent technology, genetics, and cryo-EM. These approaches exposed local Ca2+-sensing mechanisms inside organelles and at the organellar interfaces, revealed how Ca2+ binding might work to open some channels, and identified human mutations and disorders linked to a variety of Ca2+-sensing proteins. Here we attempt to place these new developments in the context of intracellular calcium homeostasis and signaling.
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Affiliation(s)
- Rafaela Bagur
- MitoCare Center for Mitochondrial Imaging Research and Diagnostics and Department of Pathology, Anatomy and Cell Biology, Thomas Jefferson University, Philadelphia, PA 19107, USA
| | - György Hajnóczky
- MitoCare Center for Mitochondrial Imaging Research and Diagnostics and Department of Pathology, Anatomy and Cell Biology, Thomas Jefferson University, Philadelphia, PA 19107, USA.
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8
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Sárközi S, Komáromi I, Jóna I, Almássy J. Lanthanides Report Calcium Sensor in the Vestibule of Ryanodine Receptor. Biophys J 2017; 112:2127-2137. [PMID: 28538150 DOI: 10.1016/j.bpj.2017.03.023] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2016] [Revised: 03/11/2017] [Accepted: 03/23/2017] [Indexed: 02/07/2023] Open
Abstract
Ca2+ regulates ryanodine receptor's (RyR) activity through an activating and an inhibiting Ca2+-binding site located on the cytoplasmic side of the RyR channel. Their altered sensitivity plays an important role in the pathology of malignant hyperthermia and heart failure. We used lanthanide ions (Ln3+) as probes to investigate the Ca2+ sensors of RyR, because they specifically bind to Ca2+-binding proteins and they are impermeable to the channel. Eu3+'s and Sm3+'s action was tested on single RyR1 channels reconstituted into planar lipid bilayers. When the activating binding site was saturated by 50 μM Ca2+, Ln3+ potently inhibited RyR's open probability (Kd Eu3+ = 167 ± 5 nM and Kd Sm3+ = 63 ± 3 nM), but in nominally 0 [Ca2+], low [Eu3+] activated the channel. These results suggest that Ln3+ acts as an agonist of both Ca2+-binding sites. More importantly, the voltage-dependent characteristics of Ln3+'s action led to the conclusion that the activating Ca2+ binding site is located within the electrical field of the channel (in the vestibule). This idea was tested by applying the pore blocker toxin maurocalcine on the cytoplasmic side of RyR. These experiments showed that RyR lost reactivity to changing cytosolic [Ca2+] from 50 μM to 100 nM when the toxin occupied the vestibule. These results suggest that maurocalcine mechanically prevented Ca2+ from dissociating from its binding site and support our vestibular Ca2+ sensor-model further.
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Affiliation(s)
- Sándor Sárközi
- Department of Physiology, Faculty of Medicine, Department of Laboratory Medicine, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - István Komáromi
- Division of Clinical Laboratory Science, Department of Laboratory Medicine, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - István Jóna
- Department of Physiology, Faculty of Medicine, Department of Laboratory Medicine, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - János Almássy
- Department of Physiology, Faculty of Medicine, Department of Laboratory Medicine, Faculty of Medicine, University of Debrecen, Debrecen, Hungary.
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9
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Zalk R, Marks AR. Ca 2+ Release Channels Join the 'Resolution Revolution'. Trends Biochem Sci 2017; 42:543-555. [PMID: 28499500 PMCID: PMC5875148 DOI: 10.1016/j.tibs.2017.04.005] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2017] [Revised: 04/02/2017] [Accepted: 04/13/2017] [Indexed: 01/22/2023]
Abstract
Ryanodine receptors (RyRs) are calcium release channels expressed in the sarcoendoplasmic reticula of many cell types including cardiac and skeletal muscle cells. In recent years Ca2+ leak through RyRs has been implicated as a major contributor to the development of diseases including heart failure, muscle myopathies, Alzheimer's disease, and diabetes, making it an important therapeutic target. Recent mammalian RyR1 cryoelectron microscopy (cryo-EM) structures of multiple functional states have clarified longstanding questions including the architecture of the transmembrane (TM) pore and cytoplasmic domains, the location and architecture of the channel gate, ligand-binding sites, and the gating mechanism. As we advance toward complete models of RyRs this new information enables the determination of domain-domain interfaces and the location and structural effects of disease-causing RyR mutations.
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Affiliation(s)
- Ran Zalk
- The National Institute for Biotechnology in the Negev, Ben-Gurion University of the Negev, Beer Sheva 84105, Israel
| | - Andrew R Marks
- Department of Physiology and Cellular Biophysics, College of Physicians and Surgeons, Columbia University, New York, NY 10032, USA; Department of Medicine, College of Physicians and Surgeons, Columbia University, New York, NY 10032, USA; Wu Center for Molecular Cardiology, College of Physicians and Surgeons, Columbia University, New York, NY 10032, USA.
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10
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Xu L, Gomez AC, Pasek DA, Meissner G, Yamaguchi N. Two EF-hand motifs in ryanodine receptor calcium release channels contribute to isoform-specific regulation by calmodulin. Cell Calcium 2017; 66:62-70. [PMID: 28807150 DOI: 10.1016/j.ceca.2017.05.013] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2017] [Revised: 05/08/2017] [Accepted: 05/24/2017] [Indexed: 01/03/2023]
Abstract
The mammalian ryanodine receptor Ca2+ release channel (RyR) has a single conserved high affinity calmodulin (CaM) binding domain. However, the skeletal muscle RyR1 is activated and cardiac muscle RyR2 is inhibited by CaM at submicromolar Ca2+. This suggests isoform-specific domains are involved in RyR regulation by CaM. To gain insight into the differential regulation of cardiac and skeletal muscle RyRs by CaM, RyR1/RyR2 chimeras and mutants were expressed in HEK293 cells, and their single channel activities were measured using a lipid bilayer method. All RyR1/RyR2 chimeras and mutants were inhibited by CaM at 2μM Ca2+, consistent with CaM inhibition of RyR1 and RyR2 at micromolar Ca2+ concentrations. An RyR1/RyR2 chimera with RyR1 N-terminal amino acid residues (aa) 1-3725 and RyR2 C-terminal aa 3692-4968 were inhibited by CaM at <1μM Ca2+ similar to RyR2. In contrast, RyR1/RyR2 chimera with RyR1 aa 1-4301 and RyR2 4254-4968 was activated at <1μM Ca2+ similar to RyR1. Replacement of RyR1 aa 3726-4298 with corresponding residues from RyR2 conferred CaM inhibition at <1μM Ca2+, which suggests RyR1 aa 3726-4298 are required for activation by CaM. Characterization of additional RyR1/RyR2 chimeras and mutants in two predicted Ca2+ binding motifs in RyR1 aa 4081-4092 (EF1) and aa 4116-4127 (EF2) suggests that both EF-hand motifs and additional sequences in the large N-terminal regions are required for isoform-specific RyR1 and RyR2 regulation by CaM at submicromolar Ca2+ concentrations.
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Affiliation(s)
- Le Xu
- Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, NC 27599-7260, United States
| | - Angela C Gomez
- Department of Regenerative Medicine and Cell Biology, Medical University of South Carolina, Charleston, SC 29425, United States; Cardiac Signaling Center, University of South Carolina, Medical University of South Carolina and Clemson University, Charleston, SC 29425, United States
| | - Daniel A Pasek
- Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, NC 27599-7260, United States
| | - Gerhard Meissner
- Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, NC 27599-7260, United States
| | - Naohiro Yamaguchi
- Department of Regenerative Medicine and Cell Biology, Medical University of South Carolina, Charleston, SC 29425, United States; Cardiac Signaling Center, University of South Carolina, Medical University of South Carolina and Clemson University, Charleston, SC 29425, United States.
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11
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Zheng W, Liu Z. Investigating the inter-subunit/subdomain interactions and motions relevant to disease mutations in the N-terminal domain of ryanodine receptors by molecular dynamics simulation. Proteins 2017; 85:1633-1644. [PMID: 28508509 DOI: 10.1002/prot.25318] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2017] [Revised: 04/28/2017] [Accepted: 05/08/2017] [Indexed: 11/12/2022]
Abstract
The ryanodine receptors (RyR) are essential to calcium signaling in striated muscles, and numerous disease mutations have been identified in two RyR isoforms, RyR1 in skeletal muscle and RyR2 in cardiac muscle. A deep understanding of the activation/regulation mechanisms of RyRs has been hampered by the shortage of high-resolution structures and dynamic information for this giant tetrameric complex in different functional states. Toward elucidating the molecular mechanisms of disease mutations in RyRs, we performed molecular dynamics simulation of the N-terminal domain (NTD) which is not only the best-resolved structural component of RyRs, but also a hotspot of disease mutations. First, we simulated the tetrameric NTD of wild-type RyR1 and three disease mutants (K155E, R157Q, and R164Q) that perturb the inter-subunit interfaces. Our simulations identified a dynamic network of salt bridges involving charged residues at the inter-subunit/subdomain interfaces and disease-mutation sites. By perturbing this key network, the above three mutations result in greater flexibility with the highest inter-subunit opening probability for R157Q. Next, we simulated the monomeric NTD of RyR2 in the presence or absence of a central Cl- anion which is known to stabilize the interfaces between the three NTD subdomains (A, B, and C). We found that the loss of Cl- restructures the salt-bridge network near the Cl- -binding site, leading to rotations of subdomain A/B relative to subdomain C and enhanced mobility between the subdomains. This finding supports a mechanism for disease mutations in the NTD of RyR2 via perturbation of the Cl- binding. The rich structural and dynamic information gained from this study will guide future mutational and functional studies of the NTD of RyRs. Proteins 2017; 85:1633-1644. © 2017 Wiley Periodicals, Inc.
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Affiliation(s)
- Wenjun Zheng
- Department of Physics, University at Buffalo, Buffalo, New York, 14260
| | - Zheng Liu
- Department of Cardiology, Shanghai Tenth People's Hospital and Pan-Vascular Research Institute, Heart, Lung, and Blood Center, Tongji University School of Medicine, Shanghai, China
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12
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Gaburjakova M, Gaburjakova J. Insight towards the identification of cytosolic Ca 2+ -binding sites in ryanodine receptors from skeletal and cardiac muscle. Acta Physiol (Oxf) 2017; 219:757-767. [PMID: 27543850 DOI: 10.1111/apha.12772] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2016] [Revised: 07/13/2016] [Accepted: 08/12/2016] [Indexed: 11/30/2022]
Abstract
Ca2+ plays a critical role in several processes involved in skeletal and cardiac muscle contraction. One key step in cardiac excitation-contraction (E-C) coupling is the activation of the cardiac ryanodine receptor (RYR2) by cytosolic Ca2+ elevations. Although this process is not critical for skeletal E-C coupling, the activation and inhibition of the skeletal ryanodine receptor (RYR1) seem to be important for overall muscle function. The RYR1 and RYR2 channels fall within the large category of Ca2+ -binding proteins that harbour highly selective Ca2+ -binding sites to receive and translate the various Ca2+ signals into specific functional responses. However, little is known about the precise localization of these sites within the cytosolic assembly of both RYR isoforms, although several experimental lines of evidence have highlighted their EF-hand nature. EF-hand proteins share a common helix-loop-helix structural motif with highly conserved residues involved in Ca2+ coordination. The first step in predicting EF-hand positive regions is to compare the primary protein structure with the EF-hand motif by employing available bioinformatics tools. Although this simple method narrows down search regions, it does not provide solid evidence regarding which regions bind Ca2+ in both RYR isoforms. In this review, we seek to highlight the key findings and experimental approaches that should strengthen our future efforts to identify the cytosolic Ca2+ -binding sites responsible for activation and inhibition in the RYR1 channel, as much less work has been conducted on the RYR2 channel.
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Affiliation(s)
- M. Gaburjakova
- Institute of Molecular Physiology and Genetics; Slovak Academy of Sciences; Bratislava Slovak Republic
| | - J. Gaburjakova
- Institute of Molecular Physiology and Genetics; Slovak Academy of Sciences; Bratislava Slovak Republic
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13
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des Georges A, Clarke OB, Zalk R, Yuan Q, Condon KJ, Grassucci RA, Hendrickson WA, Marks AR, Frank J. Structural Basis for Gating and Activation of RyR1. Cell 2016; 167:145-157.e17. [PMID: 27662087 DOI: 10.1016/j.cell.2016.08.075] [Citation(s) in RCA: 256] [Impact Index Per Article: 32.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2016] [Revised: 06/08/2016] [Accepted: 08/30/2016] [Indexed: 10/21/2022]
Abstract
The type-1 ryanodine receptor (RyR1) is an intracellular calcium (Ca(2+)) release channel required for skeletal muscle contraction. Here, we present cryo-EM reconstructions of RyR1 in multiple functional states revealing the structural basis of channel gating and ligand-dependent activation. Binding sites for the channel activators Ca(2+), ATP, and caffeine were identified at interdomain interfaces of the C-terminal domain. Either ATP or Ca(2+) alone induces conformational changes in the cytoplasmic assembly ("priming"), without pore dilation. In contrast, in the presence of all three activating ligands, high-resolution reconstructions of open and closed states of RyR1 were obtained from the same sample, enabling analyses of conformational changes associated with gating. Gating involves global conformational changes in the cytosolic assembly accompanied by local changes in the transmembrane domain, which include bending of the S6 transmembrane segment and consequent pore dilation, displacement, and deformation of the S4-S5 linker and conformational changes in the pseudo-voltage-sensor domain.
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Affiliation(s)
- Amédée des Georges
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA; Howard Hughes Medical Institute, Columbia University, New York, NY 10032, USA
| | - Oliver B Clarke
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA
| | - Ran Zalk
- Department of Physiology and Cellular Biophysics, Columbia University, New York, NY 10032, USA
| | - Qi Yuan
- Department of Physiology and Cellular Biophysics, Columbia University, New York, NY 10032, USA
| | - Kendall J Condon
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA; Howard Hughes Medical Institute, Columbia University, New York, NY 10032, USA
| | - Robert A Grassucci
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA; Howard Hughes Medical Institute, Columbia University, New York, NY 10032, USA
| | - Wayne A Hendrickson
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA; Department of Physiology and Cellular Biophysics, Columbia University, New York, NY 10032, USA.
| | - Andrew R Marks
- Department of Physiology and Cellular Biophysics, Columbia University, New York, NY 10032, USA; Department of Medicine, Columbia University, New York, NY 10032, USA; Wu Center for Molecular Cardiology, College of Physicians and Surgeons, Columbia University, New York, NY 10032, USA.
| | - Joachim Frank
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA; Howard Hughes Medical Institute, Columbia University, New York, NY 10032, USA; Department of Biological Sciences, Columbia University, New York, NY 10032, USA.
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14
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Samsó M. A guide to the 3D structure of the ryanodine receptor type 1 by cryoEM. Protein Sci 2016; 26:52-68. [PMID: 27671094 DOI: 10.1002/pro.3052] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2016] [Revised: 09/21/2016] [Accepted: 09/22/2016] [Indexed: 01/04/2023]
Abstract
Signal transduction by the ryanodine receptor (RyR) is essential in many excitable cells including all striated contractile cells and some types of neurons. While its transmembrane domain is a classic tetrameric, six-transmembrane cation channel, the cytoplasmic domain is uniquely large and complex, hosting a multiplicity of specialized domains. The overall outline and substructure readily recognizable by electron microscopy make RyR a geometrically well-behaved specimen. Hence, for the last two decades, the 3D structural study of the RyR has tracked closely the technological advances in electron microscopy, cryo-electron microscopy (cryoEM), and computerized 3D reconstruction. This review summarizes the progress in the structural determination of RyR by cryoEM and, bearing in mind the leap in resolution provided by the recent implementation of direct electron detection, analyzes the first near-atomic structures of RyR. These reveal a complex orchestration of domains controlling the channel's function, and help to understand how this could break down as a consequence of disease-causing mutations.
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Affiliation(s)
- Montserrat Samsó
- Department of Physiology and Biophysics, Virginia Commonwealth University, Richmond, Virginia
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Abstract
Ryanodine Receptors are large ion channels responsible for the release of Ca from the Endoplasmic and Sarcoplasmic Reticulum, a prerequisite for muscle contraction. Recent cryo-electron microscopy data have allowed a direct visualization of allosteric motions within these membrane protein giants.
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Affiliation(s)
- Filip Van Petegem
- University of British Columbia, Department of Biochemistry and Molecular Biology, 2350 Health Sciences Mall, V6T 1Z3 Vancouver, BC, Canada
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Wei R, Wang X, Zhang Y, Mukherjee S, Zhang L, Chen Q, Huang X, Jing S, Liu C, Li S, Wang G, Xu Y, Zhu S, Williams AJ, Sun F, Yin CC. Structural insights into Ca(2+)-activated long-range allosteric channel gating of RyR1. Cell Res 2016; 26:977-94. [PMID: 27573175 PMCID: PMC5034117 DOI: 10.1038/cr.2016.99] [Citation(s) in RCA: 74] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2016] [Revised: 07/31/2016] [Accepted: 08/03/2016] [Indexed: 12/12/2022] Open
Abstract
Ryanodine receptors (RyRs) are a class of giant ion channels with molecular mass over 2.2 mega-Daltons. These channels mediate calcium signaling in a variety of cells. Since more than 80% of the RyR protein is folded into the cytoplasmic assembly and the remaining residues form the transmembrane domain, it has been hypothesized that the activation and regulation of RyR channels occur through an as yet uncharacterized long-range allosteric mechanism. Here we report the characterization of a Ca2+-activated open-state RyR1 structure by cryo-electron microscopy. The structure has an overall resolution of 4.9 Å and a resolution of 4.2 Å for the core region. In comparison with the previously determined apo/closed-state structure, we observed long-range allosteric gating of the channel upon Ca2+ activation. In-depth structural analyses elucidated a novel channel-gating mechanism and a novel ion selectivity mechanism of RyR1. Our work not only provides structural insights into the molecular mechanisms of channel gating and regulation of RyRs, but also sheds light on structural basis for channel-gating and ion selectivity mechanisms for the six-transmembrane-helix cation channel family.
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Affiliation(s)
- Risheng Wei
- Department of Biophysics, The Health Science Center, Peking University, Beijing 100191, China
| | - Xue Wang
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China.,College of Life Science, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yan Zhang
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
| | - Saptarshi Mukherjee
- Wales Heart Research Institute, Cardiff University School of Medicine, Cardiff CF14 4XN, UK
| | - Lei Zhang
- Department of Biophysics, The Health Science Center, Peking University, Beijing 100191, China.,Electron Microscopy Analysis Laboratory, The Health Science Center, Peking University, Beijing 100191, China
| | - Qiang Chen
- Department of Biophysics, The Health Science Center, Peking University, Beijing 100191, China
| | - Xinrui Huang
- Department of Biophysics, The Health Science Center, Peking University, Beijing 100191, China
| | - Shan Jing
- Department of Biophysics, The Health Science Center, Peking University, Beijing 100191, China
| | - Congcong Liu
- Department of Biophysics, The Health Science Center, Peking University, Beijing 100191, China
| | - Shuang Li
- Department of Biophysics, The Health Science Center, Peking University, Beijing 100191, China
| | - Guangyu Wang
- Department of Biophysics, The Health Science Center, Peking University, Beijing 100191, China
| | - Yaofang Xu
- Department of Biophysics, The Health Science Center, Peking University, Beijing 100191, China
| | - Sujie Zhu
- Department of Biophysics, The Health Science Center, Peking University, Beijing 100191, China
| | - Alan J Williams
- Wales Heart Research Institute, Cardiff University School of Medicine, Cardiff CF14 4XN, UK
| | - Fei Sun
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China.,College of Life Science, University of Chinese Academy of Sciences, Beijing 100049, China.,Center for Biological Imaging, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
| | - Chang-Cheng Yin
- Department of Biophysics, The Health Science Center, Peking University, Beijing 100191, China.,Electron Microscopy Analysis Laboratory, The Health Science Center, Peking University, Beijing 100191, China.,Center for Protein Science, Peking University, Beijing 100871, China
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Gomez AC, Holford TW, Yamaguchi N. Malignant hyperthermia-associated mutations in the S2-S3 cytoplasmic loop of type 1 ryanodine receptor calcium channel impair calcium-dependent inactivation. Am J Physiol Cell Physiol 2016; 311:C749-C757. [PMID: 27558158 DOI: 10.1152/ajpcell.00134.2016] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2016] [Accepted: 08/19/2016] [Indexed: 11/22/2022]
Abstract
Channel activities of skeletal muscle ryanodine receptor (RyR1) are activated by micromolar Ca2+ and inactivated by higher (∼1 mM) Ca2+ To gain insight into a mechanism underlying Ca2+-dependent inactivation of RyR1 and its relationship with skeletal muscle diseases, we constructed nine recombinant RyR1 mutants carrying malignant hyperthermia or centronuclear myopathy-associated mutations and determined RyR1 channel activities by [3H]ryanodine binding assay. These mutations are localized in or near the RyR1 domains which are responsible for Ca2+-dependent inactivation of RyR1. Four RyR1 mutations (F4732D, G4733E, R4736W, and R4736Q) in the cytoplasmic loop between the S2 and S3 transmembrane segments (S2-S3 loop) greatly reduced Ca2+-dependent channel inactivation. Activities of these mutant channels were suppressed at 10-100 μM Ca2+, and the suppressions were relieved by 1 mM Mg2+ The Ca2+- and Mg2+-dependent regulation of S2-S3 loop RyR1 mutants are similar to those of the cardiac isoform of RyR (RyR2) rather than wild-type RyR1. Two mutations (T4825I and H4832Y) in the S4-S5 cytoplasmic loop increased Ca2+ affinities for channel activation and decreased Ca2+ affinities for inactivation, but impairment of Ca2+-dependent inactivation was not as prominent as those of S2-S3 loop mutants. Three mutations (T4082M, S4113L, and N4120Y) in the EF-hand domain showed essentially the same Ca2+-dependent channel regulation as that of wild-type RyR1. The results suggest that nine RyR1 mutants associated with skeletal muscle diseases were differently regulated by Ca2+ and Mg2+ Four malignant hyperthermia-associated RyR1 mutations in the S2-S3 loop conferred RyR2-type Ca2+- and Mg2+-dependent channel regulation.
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Affiliation(s)
- Angela C Gomez
- Department of Regenerative Medicine and Cell Biology, Medical University of South Carolina, Charleston, South Carolina; and.,Cardiac Signaling Center of University of South Carolina, Medical University of South Carolina, and Clemson University, Charleston, South Carolina
| | - Timothy W Holford
- Department of Regenerative Medicine and Cell Biology, Medical University of South Carolina, Charleston, South Carolina; and.,Cardiac Signaling Center of University of South Carolina, Medical University of South Carolina, and Clemson University, Charleston, South Carolina
| | - Naohiro Yamaguchi
- Department of Regenerative Medicine and Cell Biology, Medical University of South Carolina, Charleston, South Carolina; and .,Cardiac Signaling Center of University of South Carolina, Medical University of South Carolina, and Clemson University, Charleston, South Carolina
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Yuchi Z, Van Petegem F. Ryanodine receptors under the magnifying lens: Insights and limitations of cryo-electron microscopy and X-ray crystallography studies. Cell Calcium 2016; 59:209-27. [DOI: 10.1016/j.ceca.2016.04.003] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2016] [Revised: 04/08/2016] [Accepted: 04/09/2016] [Indexed: 10/21/2022]
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Guo W, Sun B, Xiao Z, Liu Y, Wang Y, Zhang L, Wang R, Chen SRW. The EF-hand Ca2+ Binding Domain Is Not Required for Cytosolic Ca2+ Activation of the Cardiac Ryanodine Receptor. J Biol Chem 2015; 291:2150-60. [PMID: 26663082 DOI: 10.1074/jbc.m115.693325] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2015] [Indexed: 11/06/2022] Open
Abstract
Activation of the cardiac ryanodine receptor (RyR2) by elevating cytosolic Ca(2+) is a central step in the process of Ca(2+)-induced Ca(2+) release, but the molecular basis of RyR2 activation by cytosolic Ca(2+) is poorly defined. It has been proposed recently that the putative Ca(2+) binding domain encompassing a pair of EF-hand motifs (EF1 and EF2) in the skeletal muscle ryanodine receptor (RyR1) functions as a Ca(2+) sensor that regulates the gating of RyR1. Although the role of the EF-hand domain in RyR1 function has been studied extensively, little is known about the functional significance of the corresponding EF-hand domain in RyR2. Here we investigate the effect of mutations in the EF-hand motifs on the Ca(2+) activation of RyR2. We found that mutations in the EF-hand motifs or deletion of the entire EF-hand domain did not affect the Ca(2+)-dependent activation of [(3)H]ryanodine binding or the cytosolic Ca(2+) activation of RyR2. On the other hand, deletion of the EF-hand domain markedly suppressed the luminal Ca(2+) activation of RyR2 and spontaneous Ca(2+) release in HEK293 cells during store Ca(2+) overload or store overload-induced Ca(2+) release (SOICR). Furthermore, mutations in the EF2 motif, but not EF1 motif, of RyR2 raised the threshold for SOICR termination, whereas deletion of the EF-hand domain of RyR2 increased both the activation and termination thresholds for SOICR. These results indicate that, although the EF-hand domain is not required for RyR2 activation by cytosolic Ca(2+), it plays an important role in luminal Ca(2+) activation and SOICR.
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Affiliation(s)
- Wenting Guo
- From the Libin Cardiovascular Institute of Alberta, Departments of Physiology and Pharmacology and Biochemistry and Molecular Biology, University of Calgary, Calgary, Alberta T2N 4N1, Canada
| | - Bo Sun
- From the Libin Cardiovascular Institute of Alberta, Departments of Physiology and Pharmacology and Biochemistry and Molecular Biology, University of Calgary, Calgary, Alberta T2N 4N1, Canada
| | - Zhichao Xiao
- From the Libin Cardiovascular Institute of Alberta, Departments of Physiology and Pharmacology and Biochemistry and Molecular Biology, University of Calgary, Calgary, Alberta T2N 4N1, Canada
| | - Yingjie Liu
- From the Libin Cardiovascular Institute of Alberta, Departments of Physiology and Pharmacology and Biochemistry and Molecular Biology, University of Calgary, Calgary, Alberta T2N 4N1, Canada
| | - Yundi Wang
- From the Libin Cardiovascular Institute of Alberta, Departments of Physiology and Pharmacology and Biochemistry and Molecular Biology, University of Calgary, Calgary, Alberta T2N 4N1, Canada
| | - Lin Zhang
- From the Libin Cardiovascular Institute of Alberta, Departments of Physiology and Pharmacology and Biochemistry and Molecular Biology, University of Calgary, Calgary, Alberta T2N 4N1, Canada
| | - Ruiwu Wang
- From the Libin Cardiovascular Institute of Alberta, Departments of Physiology and Pharmacology and Biochemistry and Molecular Biology, University of Calgary, Calgary, Alberta T2N 4N1, Canada
| | - S R Wayne Chen
- From the Libin Cardiovascular Institute of Alberta, Departments of Physiology and Pharmacology and Biochemistry and Molecular Biology, University of Calgary, Calgary, Alberta T2N 4N1, Canada
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Zheng W. Toward decrypting the allosteric mechanism of the ryanodine receptor based on coarse-grained structural and dynamic modeling. Proteins 2015; 83:2307-18. [DOI: 10.1002/prot.24951] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2015] [Revised: 10/09/2015] [Accepted: 10/14/2015] [Indexed: 11/07/2022]
Affiliation(s)
- Wenjun Zheng
- Department of Physics; State University of New York at Buffalo; Buffalo New York 14260
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21
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Van Petegem F. Ryanodine Receptors: Allosteric Ion Channel Giants. J Mol Biol 2015; 427:31-53. [DOI: 10.1016/j.jmb.2014.08.004] [Citation(s) in RCA: 96] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2014] [Revised: 08/02/2014] [Accepted: 08/05/2014] [Indexed: 01/27/2023]
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Structure of the rabbit ryanodine receptor RyR1 at near-atomic resolution. Nature 2014; 517:50-55. [PMID: 25517095 PMCID: PMC4338550 DOI: 10.1038/nature14063] [Citation(s) in RCA: 327] [Impact Index Per Article: 32.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2014] [Accepted: 11/12/2014] [Indexed: 12/12/2022]
Abstract
The ryanodine receptors (RyRs) are high-conductance intracellular Ca2+ channels that play a pivotal role in the excitation-contraction coupling of skeletal and cardiac muscles. RyRs are the largest known ion channels, with a homotetrameric organization and approximately 5000 residues in each protomer. Here we report the structure of the rabbit RyR1 in complex with its modulator FKBP12 at an overall resolution of 3.8 Å, determined by single-particle electron cryo-microscopy. Three previously uncharacterized domains, named Central, Handle, and Helical domains, display the armadillo repeat fold. These domains, together with the amino-terminal domain, constitute a network of superhelical scaffold for binding and propagation of conformational changes. The channel domain exhibits the voltage-gated ion channel superfamily fold with distinct features. A negative charge-enriched hairpin loop connecting S5 and the pore helix is positioned above the entrance to the selectivity filter vestibule. The four elongated S6 segments form a right-handed helical bundle that closes the pore at the cytoplasmic border of the membrane. Allosteric regulation of the pore by the cytoplasmic domains is mediated through extensive interactions between the Central domains and the channel domain. These structural features explain high ion conductance by RyRs and the long-range allosteric regulation of channel activities.
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Efremov RG, Leitner A, Aebersold R, Raunser S. Architecture and conformational switch mechanism of the ryanodine receptor. Nature 2014; 517:39-43. [DOI: 10.1038/nature13916] [Citation(s) in RCA: 250] [Impact Index Per Article: 25.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2014] [Accepted: 10/06/2014] [Indexed: 12/11/2022]
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Gomez AC, Yamaguchi N. Two regions of the ryanodine receptor calcium channel are involved in Ca(2+)-dependent inactivation. Biochemistry 2014; 53:1373-9. [PMID: 24521037 PMCID: PMC3985739 DOI: 10.1021/bi401586h] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Skeletal (RyR1) and cardiac muscle (RyR2) isoforms of ryanodine receptor calcium channels are inhibited by millimollar Ca(2+), but the affinity of RyR2 for inhibitory Ca(2+) is ~10 times lower than that of RyR1. Previous studies demonstrated that the C-terminal quarter of RyR has critical domain(s) for Ca(2+) inactivation. To obtain further insights into the molecular basis of regulation of RyRs by Ca(2+), we constructed and expressed 18 RyR1-RyR2 chimeras in HEK293 cells and determined the Ca(2+) activation and inactivation affinities of these channels using the [(3)H]ryanodine binding assay. Replacing two distinct regions of RyR1 with corresponding RyR2 sequences reduced the affinity for Ca(2+) inactivation. The first region (RyR2 amino acids 4020-4250) contains two EF-hand Ca(2+) binding motifs (EF1, amino acids 4036-4047; EF2, amino acids 4071-4082), and the second region includes the putative second transmembrane segment (S2). A RyR1-backbone chimera containing only EF2 from RyR2 had a modest (not significant) change in Ca(2+) inactivation, whereas another chimera channel carrying only EF1 from RyR2 had a significantly reduced level of Ca(2+) inactivation. The results suggest that EF1 is a more critical determinant for RyR inactivation by Ca(2+). In addition, activities of the chimera carrying RyR2 EF-hands were suppressed at 10-100 μM Ca(2+), and the suppression was relieved by 1 mM Mg(2+). The same effects have been observed with wild-type RyR2. A mutant RyR1 carrying both regions replaced with RyR2 sequences (amino acids 4020-4250 and 4560-4618) showed a Ca(2+) inactivation affinity comparable to that of RyR2, indicating that these regions are sufficient to confer RyR2-type Ca(2+)-dependent inactivation on RyR1.
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Affiliation(s)
- Angela C Gomez
- Department of Regenerative Medicine and Cell Biology, Medical University of South Carolina , and Cardiac Signaling Center, University of South Carolina , Medical University of South Carolina , and Clemson University , Charleston, South Carolina 29425, United States
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Fritsch EB, Connon RE, Werner I, Davies RE, Beggel S, Feng W, Pessah IN. Triclosan impairs swimming behavior and alters expression of excitation-contraction coupling proteins in fathead minnow (Pimephales promelas). ENVIRONMENTAL SCIENCE & TECHNOLOGY 2013; 47:2008-17. [PMID: 23305567 PMCID: PMC3640625 DOI: 10.1021/es303790b] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Triclosan (TCS), a high volume chemical widely used in consumer products, is a known aquatic contaminant found in fish inhabiting polluted watersheds. Mammalian studies have recently demonstrated that TCS disrupts signaling between the ryanodine receptor (RyR) and the dihydropyridine receptor (DHPR), two proteins essential for excitation-contraction (EC) coupling in striated muscle. We investigated the swimming behavior and expression of EC coupling proteins in larval fathead minnows (Pimephales promelas) exposed to TCS for up to 7 days. Concentrations as low as 75 μg L(-1) significantly altered fish swimming activity after 1 day; which was consistent after 7 days of exposure. The mRNA transcription and protein levels of RyR and DHPR (subunit CaV1.1) isoforms changed in a dose and time dependent manner. Crude muscle homogenates from exposed larvae did not display any apparent changes in receptor affinity toward known radioligands. In nonexposed crude muscle homogenates, TCS decreased the binding of [(3)H]PN20-110 to the DHPR and decreased the binding of [(3)H]-ryanodine to the RyR, demonstrating a direct impact at the receptor level. These results support TCS's impact on muscle function in vertebrates further exemplifying the need to re-evaluate the risks this pollutant poses to aquatic environments.
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Affiliation(s)
- Erika B Fritsch
- Department of Molecular Biosciences, School of Veterinary Medicine, University of California, Davis, California 95616, USA.
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Abstract
Binding of IP3 (inositol 1,4,5-trisphosphate) to the IP3-binding core (residues 224–604) of IP3Rs (IP3 receptors) initiates opening of these ubiquitous intracellular Ca2+ channels. The mechanisms are unresolved, but require conformational changes to pass through the suppressor domain (residues 1–223). A calmodulin-binding peptide derived from myosin light chain kinase uncouples these events. We identified a similar conserved 1-8-14 calmodulin-binding motif within the suppressor domain of IP3R1 and, using peptides and mutagenesis, we demonstrate that it is essential for IP3R activation, whether assessed by IP3-evoked Ca2+ release or patch-clamp recoding of nuclear IP3R. Mimetic peptides specifically inhibit activation of IP3R by uncoupling the IP3-binding core from the suppressor domain. Mutations of key hydrophobic residues within the endogenous 1-8-14 motif mimic the peptides. Our results show that an endogenous 1-8-14 motif mediates conformational changes that are essential for IP3R activation. The inhibitory effects of calmodulin and related proteins may result from disruption of this essential interaction.
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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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Techniques and Methodologies to Study the Ryanodine Receptor at the Molecular, Subcellular and Cellular Level. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2012; 740:183-215. [DOI: 10.1007/978-94-007-2888-2_8] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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Ryanodine receptors, a family of intracellular calcium ion channels, are expressed throughout early vertebrate development. BMC Res Notes 2011; 4:541. [PMID: 22168922 PMCID: PMC3262159 DOI: 10.1186/1756-0500-4-541] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2011] [Accepted: 12/14/2011] [Indexed: 01/14/2023] Open
Abstract
BACKGROUND Calcium signals ([Ca2+]i) direct many aspects of embryo development but their regulation is not well characterised. Ryanodine receptors (RyRs) are a family of intracellular Ca2+ release channels that control the flux of Ca2+ from internal stores into the cytosol. RyRs are primarily known for their role in excitation-contraction coupling in adult striated muscle and ryr gene mutations are implicated in several human diseases. Current evidence suggests that RyRs do not have a major role to play prior to organogenesis but regulate tissue differentiation. FINDINGS The sequences of the five zebrafish ryr genes were confirmed, their evolutionary relationship established and the primary sequences compared to other vertebrates, including humans. RyRs are differentially expressed in slow (ryr1a), fast (ryr3) and both types (ryr1b) of developing skeletal muscle. There are two ryr2 genes (ryr2a and ryr2b) which are expressed exclusively in developing CNS and cardiac tissue, respectively. In addition, ryr3 and ryr2a mRNA is detectable in the initial stages of development, prior to embryonic axis formation. CONCLUSIONS Our work reveals that zebrafish ryr genes are differentially expressed throughout the developing embryo from cleavage onwards. The data suggests that RyR-regulated Ca2+ signals are associated with several aspects of embryonic development, from organogenesis through to the differentiation of the musculoskeletal, cardiovascular and nervous system. These studies will facilitate further work to explore the developmental function of RyRs in each of these tissue types.
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Affiliation(s)
- Susan L Hamilton
- Department of Molecular Physiology and Biophysics, Baylor College of Medicine, Houston, TX 77030, USA.
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Interaction of the Lys(3614)-Asn(3643) calmodulin-binding domain with the Cys(4114)-Asn(4142) region of the type 1 ryanodine receptor is involved in the mechanism of Ca2+/agonist-induced channel activation. Biochem J 2008; 411:415-23. [PMID: 18171325 DOI: 10.1042/bj20071375] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
In the present study we show that the interaction of the CaM (calmodulin)-binding domain (Lys(3614)-Asn(3643)) with the Cys(4114)-Asn(4142) region (a region included in the CaM-like domain) serves as an intrinsic regulator of the RyR1 (type-1 ryanodine receptor). We tested the effects of antibodies raised against the two putative key regions of RyR1 [anti-(Lys(3614)-Asn(3643)) and anti-(Cys(4114)-Asn(4142)) antibodies]. Both antibodies produced significant inhibition of [3H]ryanodine-binding activity of RyR1. This suggests that the inter-domain interaction between the two domains, Lys(3614)-Asn(3643) and Cys(4114)-Asn(4142), activates the channel, and that the binding of antibody to either side of the interacting domain pair interfered with the formation of a 'channel-activation link' between the two regions. In order to spectroscopically monitor the mode of interaction of these domains, the site of inter-domain interaction was fluorescently labelled with MCA [(7-methoxycoumarin-4-yl)acetyl] in a site-directed manner. The accessibility of the bound MCA to a large molecular mass fluorescence quencher, BSA-QSY (namely, the size of a gap between the interacting domains) decreased with an increase of [Ca2+] in a range of 0.03-2.0 microM, as determined by Stern-Volmer fluorescence quenching analysis. The Ca2+-dependent decrease in the quencher accessibility was more pronounced in the presence of 150 microM 4-CmC (4-chlorometacresol), and was reversed by 1 mM Mg2+ (a well-known inhibitor of Ca2+/agonist-induced channel activation). These results suggest that the Lys(3614)-Asn(3643) and Cys(4114)-Asn(4142) regions of RyR1 interact with each other in a Ca2+- and agonist-dependent manner, and this serves as a mechanism of Ca2+- and agonist-dependent activation of the RyR1 Ca2+ channel.
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Shoshan-Barmatz V, Zakar M, Shmuelivich F, Nahon E, Vardi N. Retina expresses a novel variant of the ryanodine receptor. Eur J Neurosci 2007; 26:3113-25. [PMID: 18005065 DOI: 10.1111/j.1460-9568.2007.05931.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Calcium released from intracellular stores via the ryanodine receptor (RyR) mediates a variety of signalling processes. We previously showed that retina expresses the three known types of RyR, but retinal membrane preparations exhibit unique characteristics such as Ca2+-independent [3H]ryanodine-binding and inhibition by caffeine. We have heretofore suggested that the major retinal RyR isoform is novel. The present study aimed to identify this receptor isoform and to localize RyR in mammalian retina. Immunoblotting with specific and pan-antibodies showed that the major retinal RyR has a mobility similar to that of RyR2 or RyR3. Real-time PCR revealed that the major type is RyR2, and RT-PCR followed by sequencing showed a transcript that encodes a protein with approximately 99% identity to RyR2, yet lacking two regions of seven and 12 amino acids and including an additional insertion of eight amino acids. An antibody against RyR2 localized this type to somas and primary dendrites of most retinal neurons. An antibody against RyR1 localized RyR to most somas but also revealed staining in photoreceptor outer segments, concentrated on the disk membranes at their rim. The ryanodine-binding properties and the electrophoretic mobility of RyR from the outer segments were similar to those of the whole retinal preparation. The results thus identify a novel variant of RyR2 which can contribute to regulating photoreceptor Ca2+ concentrations. The restricted localization of the outer segment RyR to the disk rim suggests that its activation mechanism involves a coupling between retinal RyR and the cGMP-gated channel.
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Affiliation(s)
- Varda Shoshan-Barmatz
- Department of Life Sciences, Ben Gurion University of the Negev, Beer Sheva, 84105, Israel.
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Winslow RL, Tanskanen A, Chen M, Greenstein JL. Multiscale modeling of calcium signaling in the cardiac dyad. Ann N Y Acad Sci 2007; 1080:362-75. [PMID: 17132795 DOI: 10.1196/annals.1380.027] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Calcium (Ca(2+))-induced Ca(2+)-release (CICR) takes place in spatially restricted microdomains known as dyads. The length scale over which CICR occurs is on the order of nanometers and relevant time scales range from micro- to milliseconds. Quantitative understanding of CICR therefore requires development of models that are applicable over a range of spatio-temporal scales. We will present several new approaches for multiscale modeling of CICR. First, we present a model of dyad Ca(2+) dynamics in which the Fokker-Planck equation (FPE) is solved for the probability P(x, t) that a Ca(2+) ion is located at dyad position x at time t. Using this model, we demonstrate that (a) Ca(2+) signaling in the dyad is mediated by approximately tens of Ca(2+) ions; (b) these signaling events are noisy due to the small number of ions involved; and (c) the geometry of the RyR (ryanodine receptors) protein may function to restrict the diffusion of and to "funnel" Ca(2+) ions to activation-binding sites on the RyR, thus increasing RyR open probability and excitation-contraction (EC) coupling gain. Simplification of this model to one in which the dyadic space is represented using a single compartment yields the stochastic local-control model of CICR developed previously. We have shown that this model captures fundamental properties of CICR, such as graded release and voltage-dependent gain, may be integrated within a model of the myocyte and may be simulated in reasonable times using a combination of efficient numerical methods and parallel computing, but remains too complex for general use in cell simulations. To address this problem, we show how separation of time scales may be used to formulate a model in which nearby L-type Ca(2+) channels (LCCs) and RyRs gate as a coupled system that may be described using low-dimensional systems of ordinary differential equations, thus reducing computational complexity while capturing fundamentally important properties of CICR. The simplified model may be solved many orders of magnitude faster than can either of the more detailed models, thus enabling incorporation into tissue-level simulations.
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Affiliation(s)
- Raimond L Winslow
- Institute for Computational Medicine and Center for Cardiovascular Bioinformatics & Modeling, The Johns Hopkins University School of Medicine and Whiting School of Engineering, Baltimore, MD 21218, USA.
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Hamada T, Bannister ML, Ikemoto N. Peptide probe study of the role of interaction between the cytoplasmic and transmembrane domains of the ryanodine receptor in the channel regulation mechanism. Biochemistry 2007; 46:4272-9. [PMID: 17361990 DOI: 10.1021/bi061557f] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Ryanodine receptor (RyR) mutations linked with some congenital skeletal and cardiac diseases are localized to three easily definable regions: region 1 (N-terminal domain), region 2 (central domain), and a rather broad region 3 containing the channel pore. As shown in our recent studies, the interdomain interaction between regions 1 and 2 plays a critical role in channel regulation and pathogenesis. Here we present evidence that within region 3 there is a similar channel regulation mechanism mediated by an interdomain interaction. DP15, a peptide corresponding to RyR1 residues 4820-4841, produced significant activation of [3H]ryanodine binding above threshold Ca2+ concentrations (>or=0.3 microM), but MH mutations (L4823P or L4837V) made in DP15 almost completely abolished its channel activating function. To identify the DP15 binding site(s) within RyR1, DP15 (labeled with a fluorescent probe Alexa Fluor 680 and a photoaffinity cross-linker APG) was cross-linked to RyR1, and the site of cross-linking was identified by gel analysis of fluorescently labeled proteolytic fragments with the aid of Western blotting with site-specific antibodies. The shortest fluorescently labeled band was a 96 kDa fragment which was stained with an antibody directed to the region of residues 4114-4142 of RyR1, indicating that the interaction between the region of residues 4820-4841 adjacent to the channel pore and the 96 kDa segment containing the region of residues 4114-4142 is involved in the mechanism of Ca2+-dependent channel regulation. In further support of this concept, anti-DP15 antibody and cardiac counterpart of DP15 produced channel activation similar to that of DP15.
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Affiliation(s)
- Tomoyo Hamada
- Boston Biomedical Research Institute, Watertown, Massachusetts 02472, USA
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Tanskanen AJ, Greenstein JL, Chen A, Sun SX, Winslow RL. Protein geometry and placement in the cardiac dyad influence macroscopic properties of calcium-induced calcium release. Biophys J 2007; 92:3379-96. [PMID: 17325016 PMCID: PMC1853149 DOI: 10.1529/biophysj.106.089425] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
In cardiac ventricular myocytes, events crucial to excitation-contraction coupling take place in spatially restricted microdomains known as dyads. The movement and dynamics of calcium (Ca2+) ions in the dyad have often been described by assigning continuously valued Ca2+ concentrations to one or more dyadic compartments. However, even at its peak, the estimated number of free Ca2+ ions present in a single dyad is small (approximately 10-100 ions). This in turn suggests that modeling dyadic calcium dynamics using laws of mass action may be inappropriate. In this study, we develop a model of stochastic molecular signaling between L-type Ca2+ channels (LCCs) and ryanodine receptors (RyR2s) that describes: a), known features of dyad geometry, including the space-filling properties of key dyadic proteins; and b), movement of individual Ca2+ ions within the dyad, as driven by electrodiffusion. The model enables investigation of how local Ca2+ signaling is influenced by dyad structure, including the configuration of key proteins within the dyad, the location of Ca2+ binding sites, and membrane surface charges. Using this model, we demonstrate that LCC-RyR2 signaling is influenced by both the stochastic dynamics of Ca2+ ions in the dyad as well as the shape and relative positioning of dyad proteins. Results suggest the hypothesis that the relative placement and shape of the RyR2 proteins helps to "funnel" Ca2+ ions to RyR2 binding sites, thus increasing excitation-contraction coupling gain.
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Affiliation(s)
- Antti J Tanskanen
- The Institute for Computational Medicine, Center for Cardiovascular Bioinformatics and Modeling, The Johns Hopkins University School of Medicine and Whiting School of Engineering, Baltimore, Maryland, USA
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George CH, Jundi H, Thomas NL, Fry DL, Lai FA. Ryanodine receptors and ventricular arrhythmias: emerging trends in mutations, mechanisms and therapies. J Mol Cell Cardiol 2006; 42:34-50. [PMID: 17081562 DOI: 10.1016/j.yjmcc.2006.08.115] [Citation(s) in RCA: 130] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/07/2006] [Accepted: 08/30/2006] [Indexed: 11/25/2022]
Abstract
It has been six years since the first reported link between mutations in the cardiac ryanodine receptor Ca(2+) release channel (RyR2) and catecholaminergic polymorphic ventricular tachycardia (CPVT), a malignant stress-induced arrhythmia. In this time, rapid advances have been made in identifying new mutations, and in understanding how these mutations disrupt normal channel function to cause VT that frequently degenerates into ventricular fibrillation (VF) and sudden death. Functional characterisation of these RyR2 Ca(2+) channelopathies suggests that mutations alter the ability of RyR2 to sense its intracellular environment, and that channel modulation via covalent modification, Ca(2+)- and Mg(2+)-dependent regulation and structural feedback mechanisms are catastrophically disturbed. This review reconciles the current status of RyR2 mutation-linked etiopathology, the significance of mutational clustering within the RyR2 polypeptide and the mechanisms underlying channel dysfunction. We will also review new data that explores the link between abnormal Ca(2+) release and the resultant cardiac electrical instability in VT and VF, and how these recent developments impact on novel anti-arrhythmic therapies. Finally, we evaluate the concept that mechanistic differences between CPVT and other arrhythmogenic disorders may preclude a common therapeutic strategy to normalise RyR2 function in cardiac disease.
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Affiliation(s)
- Christopher H George
- Department of Cardiology, Wales Heart Research Institute, Cardiff University School of Medicine, Heath Park, Cardiff CF14 4XN, UK.
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Jacobson AR, Moe ST, Allen PD, Fessenden JD. Structural Determinants of 4-Chloro-m-cresol Required for Activation of Ryanodine Receptor Type 1. Mol Pharmacol 2006; 70:259-66. [PMID: 16601083 DOI: 10.1124/mol.106.022491] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
4-Chloro-m-cresol (4-CmC) is a clinically relevant activator of the intracellular Ca2+ release channel, the ryanodine receptor isoform 1 (RyR1). In this study, the chemical moieties on the 4-CmC molecule required for its activation of RyR1 were determined using structure-activity relationship analysis with a set of commercially available 4-CmC analogs. Separate compounds each lacking one of the three functional groups of 4-CmC (1-hydroxyl, 3-methyl, or 4-chloro) were poor activators of RyR1. Substitution of different chemical groups for the 1-hydroxyl of 4-CmC resulted in compounds that were poor activators of RyR1, suggesting that the hydroxyl group is preferred at this position. Substitution of hydrophobic groups at the 3-position enhanced bioactivity of the compound relative to 4-CmC, whereas substitution with hydrophilic groups abolished bioactivity. Likewise, 4-CmC analogs with hydrophobic groups substituted into the 4-position enhanced bioactivity, whereas hydrophilic or charged groups diminished bioactivity. 4-CmC analogs containing a single hydrophobic group at either the 3- or 4-position as well as 3,5-disubstituted or 3,4,5-trisubstituted phenols were also effective activators of RyR1. These results indicate that the 1-hydroxyl group of 4-CmC is required for activation of RyR1 and that hydrophobic groups at the 3,4- and 5-positions are preferred. These findings suggest that the 4-CmC binding site on RyR1 most likely consists of a hydrophilic region to interact with the 1-hydroxyl as well as a hydrophobic region(s) to interact with chemical groups at the 3- and/or 4-positions of 4-CmC.
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Xiong L, Zhang JZ, He R, Hamilton SL. A Ca2+-binding domain in RyR1 that interacts with the calmodulin binding site and modulates channel activity. Biophys J 2005; 90:173-82. [PMID: 16227507 PMCID: PMC1367016 DOI: 10.1529/biophysj.105.066092] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
A fragment of RyR1 (amino acids 4064-4210) is predicted to fold to at least one lobe of calmodulin and to bind Ca(2+). This fragment of RyR1 (R4064-4210) was subcloned, expressed, refolded, and purified. Consistent with the predicted folding pattern, R4064-4210 was found to bind two molecules of Ca(2+) and undergo a structural change upon binding Ca(2+) that exposes hydrophobic amino acids. R4064-4210 also binds to RyR1, the L-type Ca(2+) channel (Cav(1.1)), and several synthetic calmodulin binding peptides. Both R4064-4210 and a peptide representing the calmodulin-binding region of RyR1 (R3614-3643) alter the Ca(2+) dependence of ((3)H)ryanodine binding to RyR1, suggesting that they may both be interfering with an intramolecular interaction between amino acids 4064-4210 and amino acids 3614-3643 in the native RyR1 to alter or regulate the response of the channel to changes in Ca(2+) concentration. The finding that a domain within RyR1 binds Ca(2+) and interacts with calmodulin-binding motifs may provide insights into the mechanism for calcium- and calmodulin-dependent regulation of this channel and perhaps for its regulation by the L-type Ca(2+) channel.
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Affiliation(s)
- Liangwen Xiong
- Department of Molecular Physiology and Biophysics, Baylor College of Medicine, Houston, Texas, USA
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40
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Ebbinghaus-Kintscher U, Luemmen P, Lobitz N, Schulte T, Funke C, Fischer R, Masaki T, Yasokawa N, Tohnishi M. Phthalic acid diamides activate ryanodine-sensitive Ca2+ release channels in insects. Cell Calcium 2005; 39:21-33. [PMID: 16219348 DOI: 10.1016/j.ceca.2005.09.002] [Citation(s) in RCA: 144] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2005] [Revised: 09/01/2005] [Accepted: 09/05/2005] [Indexed: 11/20/2022]
Abstract
Flubendiamide represents a novel chemical family of substituted phthalic acid diamides with potent insecticidal activity. So far, the molecular target and the mechanism of action were not known. Here we present for the first time evidence that phthalic acid diamides activate ryanodine-sensitive intracellular calcium release channels (ryanodine receptors, RyR) in insects. With Ca(2+) measurements, we showed that flubendiamide and related compounds induced ryanodine-sensitive cytosolic calcium transients that were independent of the extracellular calcium concentration in isolated neurons from the pest insect Heliothis virescens as well as in transfected CHO cells expressing the ryanodine receptor from Drosophila melanogaster. Binding studies on microsomal membranes from Heliothis flight muscles revealed that flubendiamide and related compounds interacted with a site distinct from the ryanodine binding site and disrupted the calcium regulation of ryanodine binding by an allosteric mechanism. This novel insecticide mode of action seems to be restricted to specific RyR subtypes because the phthalic acid diamides reported here had almost no effect on mammalian type 1 ryanodine receptors.
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Abstract
RyRs are large homotetrameric proteins that are approximately 4/5 cytoplasmic and approximately 1/5 transmembrane and luminal in mass. Mutations in RyRs produce human disease and many of these disease-causing mutations are in the cytoplasmic domains. To elucidate the mechanisms of a disease and to develop interventions, it is crucial to determine how the alterations in the cytoplasmic domains communicate with the transmembrane pore of this channel. One of the major activators of all three RyR isoforms is Ca2+ and some of the disease-causing mutations are thought to alter the sensitivity of the channels to Ca2+ activation. This review examines the current state of structural understanding of the RyR channel activation.
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Affiliation(s)
- Susan L Hamilton
- Department of Molecular Physiology and Biophysics, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA.
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Ranatunga KM, Moreno-King TM, Tanna B, Wang R, Chen SRW, Ruest L, Welch W, Williams AJ. The Gln4863Ala mutation within a putative, pore-lining trans-membrane helix of the cardiac ryanodine receptor channel alters both the kinetics of ryanoid interaction and the subsequent fractional conductance. Mol Pharmacol 2005; 68:840-6. [PMID: 15955866 DOI: 10.1124/mol.105.012807] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The specific, high-affinity interaction of the plant toxin ryanodine with its molecular target the ryanodine receptor channel (RyR) has been instrumental in RyR research. Alanine scanning of putative pore regions of mouse RyR2 has highlighted the amino acid Gln4863, predicted to lie within trans-membrane helix TM10, as an important determinant of ryanodine binding. We have investigated the effects of several ryanodine derivatives, guanidinopropionylryanodine, 21-p-nitrobenzoylamino-9alpha-hydroxyryanodine, 8beta-amino-9alpha-hydroxyryanodine, and 21-amino-9alpha-hydroxyryanodine, with the mouse Q4863A RyR2 mutant at the single-channel level. Our results demonstrate that the rate of dissociation of all ryanoids investigated is increased by the mutation. The modification of channel function after ryanoid binding is qualitatively similar for wild-type and mutant, but in several cases, single-channel conductances were increased with Q4863A. These novel findings have been interpreted within the framework of existing comparative molecular field analysis studies on ryanoids. We suggest that replacement of a glutamine by an alanine residue at position 4863 causes RyR2 to simultaneously alter interactions with both ends of the ryanoid molecule.
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Affiliation(s)
- Kishani M Ranatunga
- Myocardial Systems Biology Group, National Heart and Lung Institute, Guy Scadding Building, Imperial College London, London SW3 6LY, United Kingdom
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Thomas NL, Lai FA, George CH. Differential Ca2+ sensitivity of RyR2 mutations reveals distinct mechanisms of channel dysfunction in sudden cardiac death. Biochem Biophys Res Commun 2005; 331:231-8. [PMID: 15845383 DOI: 10.1016/j.bbrc.2005.02.194] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2005] [Indexed: 11/24/2022]
Abstract
Arrhythmogenic point mutations in RyR2 result in abnormal Ca(2+) release following cardiac stimulation, leading to sudden cardiac death (SCD). Recently, we have demonstrated that significant functional differences exist between SCD-linked RyR2 mutations. Here, we investigated the molecular basis of this heterogeneity and determined the sensitivity of mutant RyR2 channels to cytoplasmic [Ca(2+)] ([Ca(2+)](c)) in living cells. Using streptolysin-O permeabilised human embryonic kidney cells, [Ca(2+)](c) was clamped in cells expressing GFP-tagged wild-type (WT) or SCD-linked RyR2 mutants (L(433)P, N(2386)I, and R(176)Q/T(2504)M). Although resting [Ca(2+)](c) was comparable in all cells, RyR2 mutants were characterised by a profound loss of Ca(2+)-dependent inhibition following caffeine stimulation when compared with WT channels. The ER Ca(2+) store was not perturbed in these experiments. Our findings support the hypothesis that SCD-linked mutational loci may be an important mechanistic determinant of RyR2 dysfunction and indicate that there is unlikely to be a unifying mechanism for channel dysfunction in SCD.
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Affiliation(s)
- N Lowri Thomas
- Department of Cardiology, Wales Heart Research Institute, Cardiff University School of Medicine, Cardiff, Wales CF14 4XN, UK
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