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Molecular, Subcellular, and Arrhythmogenic Mechanisms in Genetic RyR2 Disease. Biomolecules 2022; 12:biom12081030. [PMID: 35892340 PMCID: PMC9394283 DOI: 10.3390/biom12081030] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2022] [Revised: 07/22/2022] [Accepted: 07/24/2022] [Indexed: 11/17/2022] Open
Abstract
The ryanodine receptor (RyR2) has a critical role in controlling Ca2+ release from the sarcoplasmic reticulum (SR) throughout the cardiac cycle. RyR2 protein has multiple functional domains with specific roles, and four of these RyR2 protomers are required to form the quaternary structure that comprises the functional channel. Numerous mutations in the gene encoding RyR2 protein have been identified and many are linked to a wide spectrum of arrhythmic heart disease. Gain of function mutations (GoF) result in a hyperactive channel that causes excessive spontaneous SR Ca2+ release. This is the predominant cause of the inherited syndrome catecholaminergic polymorphic ventricular tachycardia (CPVT). Recently, rare hypoactive loss of function (LoF) mutations have been identified that produce atypical effects on cardiac Ca2+ handling that has been termed calcium release deficiency syndrome (CRDS). Aberrant Ca2+ release resulting from both GoF and LoF mutations can result in arrhythmias through the Na+/Ca2+ exchange mechanism. This mini-review discusses recent findings regarding the role of RyR2 domains and endogenous regulators that influence RyR2 gating normally and with GoF/LoF mutations. The arrhythmogenic consequences of GoF/LoF mutations will then be discussed at the macromolecular and cellular level.
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2
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Seidel M, de Meritens CR, Johnson L, Parthimos D, Bannister M, Thomas NL, Ozekhome-Mike E, Lai FA, Zissimopoulos S. Identification of an amino-terminus determinant critical for ryanodine receptor/Ca2+ release channel function. Cardiovasc Res 2020; 117:780-791. [PMID: 32077934 PMCID: PMC7898959 DOI: 10.1093/cvr/cvaa043] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/16/2019] [Revised: 12/05/2019] [Accepted: 02/17/2020] [Indexed: 01/12/2023] Open
Abstract
AIMS The cardiac ryanodine receptor (RyR2), which mediates intracellular Ca2+ release to trigger cardiomyocyte contraction, participates in development of acquired and inherited arrhythmogenic cardiac disease. This study was undertaken to characterize the network of inter- and intra-subunit interactions regulating the activity of the RyR2 homotetramer. METHODS AND RESULTS We use mutational investigations combined with biochemical assays to identify the peptide sequence bridging the β8 with β9 strand as the primary determinant mediating RyR2 N-terminus self-association. The negatively charged side chains of two aspartate residues (D179 and D180) within the β8-β9 loop are crucial for the N-terminal inter-subunit interaction. We also show that the RyR2 N-terminus domain interacts with the C-terminal channel pore region in a Ca2+-independent manner. The β8-β9 loop is required for efficient RyR2 subunit oligomerization but it is dispensable for N-terminus interaction with C-terminus. Deletion of the β8-β9 sequence produces unstable tetrameric channels with subdued intracellular Ca2+ mobilization implicating a role for this domain in channel opening. The arrhythmia-linked R176Q mutation within the β8-β9 loop decreases N-terminus tetramerization but does not affect RyR2 subunit tetramerization or the N-terminus interaction with C-terminus. RyR2R176Q is a characteristic hypersensitive channel displaying enhanced intracellular Ca2+ mobilization suggesting an additional role for the β8-β9 domain in channel closing. CONCLUSION These results suggest that efficient N-terminus inter-subunit communication mediated by the β8-β9 loop may constitute a primary regulatory mechanism for both RyR2 channel activation and suppression.
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Affiliation(s)
- Monika Seidel
- Department of Cardiology, School of Medicine, Wales Heart Research Institute, Cardiff University, Heath Park, Cardiff CF14 4XN, UK.,Swansea University Medical School, Institute of Life Science, Swansea SA2 8PP, UK
| | - Camille Rabesahala de Meritens
- Department of Cardiology, School of Medicine, Wales Heart Research Institute, Cardiff University, Heath Park, Cardiff CF14 4XN, UK.,Swansea University Medical School, Institute of Life Science, Swansea SA2 8PP, UK
| | - Louisa Johnson
- Department of Cardiology, School of Medicine, Wales Heart Research Institute, Cardiff University, Heath Park, Cardiff CF14 4XN, UK.,Swansea University Medical School, Institute of Life Science, Swansea SA2 8PP, UK
| | - Dimitris Parthimos
- Department of Cardiology, School of Medicine, Wales Heart Research Institute, Cardiff University, Heath Park, Cardiff CF14 4XN, UK.,Division of Cancer & Genetics, School of Medicine, Cardiff University, Cardiff CF14 4XN, UK
| | - Mark Bannister
- Department of Cardiology, School of Medicine, Wales Heart Research Institute, Cardiff University, Heath Park, Cardiff CF14 4XN, UK.,Swansea University Medical School, Institute of Life Science, Swansea SA2 8PP, UK
| | - Nia Lowri Thomas
- Department of Cardiology, School of Medicine, Wales Heart Research Institute, Cardiff University, Heath Park, Cardiff CF14 4XN, UK.,School of Pharmacy & Pharmaceutical Sciences, Cardiff University, Cardiff CF10 3NB, UK
| | - Esizaze Ozekhome-Mike
- Department of Cardiology, School of Medicine, Wales Heart Research Institute, Cardiff University, Heath Park, Cardiff CF14 4XN, UK.,Swansea University Medical School, Institute of Life Science, Swansea SA2 8PP, UK
| | - Francis Anthony Lai
- College of Medicine, QU Health, and Biomedical Research Centre, Qatar University, Doha, Qatar
| | - Spyros Zissimopoulos
- Department of Cardiology, School of Medicine, Wales Heart Research Institute, Cardiff University, Heath Park, Cardiff CF14 4XN, UK.,Swansea University Medical School, Institute of Life Science, Swansea SA2 8PP, UK
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3
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Bauer JA, Borko Ľ, Pavlović J, Kutejová E, Bauerová-Hlinková V. Disease-associated mutations alter the dynamic motion of the N-terminal domain of the human cardiac ryanodine receptor. J Biomol Struct Dyn 2019; 38:1054-1070. [PMID: 30909845 DOI: 10.1080/07391102.2019.1600027] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The human cardiac ryanodine receptor (hRyR2), the ion channel responsible for the release of Ca2+ ions from the sarcoplasmic reticulum into the cytosol, plays an important role in cardiac muscle contraction. Mutations to this channel are associated with inherited cardiac arrhythmias. These mutations appear to cluster in distinct parts of the N-terminal, central and C-terminal areas of the channel. Here, we used molecular dynamics simulation to examine the effects three disease-associated mutations to the N-terminal region, R414L, I419F and R420W, have on the dynamics of a model of residues 1-655 of hRyR2. We find that the R414L and I419F mutations diminish the overall amplitude of motion without greatly changing the direction of motion of the individual domains, whereas R420W both enhances the amplitude and changes the direction of motion. Based on these results, we hypothesize that R414L and I419F hinder channel closing, whereas R420W may enhance channel opening. Overall, it appears that the wild-type protein possesses a moderate level of flexibility which allows the gate to close and not easily open without an opening signal. These mutations, however, disrupt this balance by making the gate either too rigid or too loose, causing closing to become difficult or less effective. Small-angle X-ray scattering studies of the same 1-655 residue fragment are in agreement with the molecular dynamics results and also suggest that the rest of the protein is needed to keep the entire domain properly folded.Communicated by Ramaswamy H. Sarma.
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Affiliation(s)
- Jacob A Bauer
- Department of Biochemistry and Structural Biology, Institute of Molecular Biology, Slovak Academy of Sciences, Bratislava, Slovakia
| | - Ľubomír Borko
- Department of Biochemistry and Structural Biology, Institute of Molecular Biology, Slovak Academy of Sciences, Bratislava, Slovakia
| | - Jelena Pavlović
- Department of Biochemistry and Structural Biology, Institute of Molecular Biology, Slovak Academy of Sciences, Bratislava, Slovakia
| | - Eva Kutejová
- Department of Biochemistry and Structural Biology, Institute of Molecular Biology, Slovak Academy of Sciences, Bratislava, Slovakia
| | - Vladena Bauerová-Hlinková
- Department of Biochemistry and Structural Biology, Institute of Molecular Biology, Slovak Academy of Sciences, Bratislava, Slovakia
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4
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Polster A, Perni S, Filipova D, Moua O, Ohrtman JD, Bichraoui H, Beam KG, Papadopoulos S. Junctional trafficking and restoration of retrograde signaling by the cytoplasmic RyR1 domain. J Gen Physiol 2017; 150:293-306. [PMID: 29284662 PMCID: PMC5806685 DOI: 10.1085/jgp.201711879] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2017] [Accepted: 12/07/2017] [Indexed: 11/20/2022] Open
Abstract
The type 1 ryanodine receptor (RyR1) in skeletal muscle is a homotetrameric protein that releases Ca2+ from the sarcoplasmic reticulum (SR) in response to an "orthograde" signal from the dihydropyridine receptor (DHPR) in the plasma membrane (PM). Additionally, a "retrograde" signal from RyR1 increases the amplitude of the Ca2+ current produced by CaV1.1, the principle subunit of the DHPR. This bidirectional signaling is thought to depend on physical links, of unknown identity, between the DHPR and RyR1. Here, we investigate whether the isolated cytoplasmic domain of RyR1 can interact structurally or functionally with CaV1.1 by producing an N-terminal construct (RyR11:4300) that lacks the C-terminal membrane domain. In CaV1.1-null (dysgenic) myotubes, RyR11:4300 is diffusely distributed, but in RyR1-null (dyspedic) myotubes it localizes in puncta at SR-PM junctions containing endogenous CaV1.1. Fluorescence recovery after photobleaching indicates that diffuse RyR11:4300 is mobile, whereas resistance to being washed out with a large-bore micropipette indicates that the punctate RyR11:4300 stably associates with PM-SR junctions. Strikingly, expression of RyR11:4300 in dyspedic myotubes causes an increased amplitude, and slowed activation, of Ca2+ current through CaV1.1, which is almost identical to the effects of full-length RyR1. Fast protein liquid chromatography indicates that ∼25% of RyR11:4300 in diluted cytosolic lysate of transfected tsA201 cells is present in complexes larger in size than the monomer, and intermolecular fluorescence resonance energy transfer implies that RyR11:4300 is significantly oligomerized within intact tsA201 cells and dyspedic myotubes. A large fraction of these oligomers may be homotetramers because freeze-fracture electron micrographs reveal that the frequency of particles arranged like DHPR tetrads is substantially increased by transfecting RyR-null myotubes with RyR11:4300 In summary, the RyR1 cytoplasmic domain, separated from its SR membrane anchor, retains a tendency toward oligomerization/tetramerization, binds to SR-PM junctions in myotubes only if CaV1.1 is also present and is fully functional in retrograde signaling to CaV1.1.
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Affiliation(s)
- Alexander Polster
- Department of Physiology and Biophysics, University of Colorado Denver Anschutz Medical Campus, Denver, CO
| | - Stefano Perni
- Department of Physiology and Biophysics, University of Colorado Denver Anschutz Medical Campus, Denver, CO
| | - Dilyana Filipova
- Institute of Vegetative Physiology, University Hospital of Cologne, Cologne, Germany
| | - Ong Moua
- Department of Physiology and Biophysics, University of Colorado Denver Anschutz Medical Campus, Denver, CO
| | - Joshua D Ohrtman
- Department of Physiology and Biophysics, University of Colorado Denver Anschutz Medical Campus, Denver, CO
| | - Hicham Bichraoui
- Department of Physiology and Biophysics, University of Colorado Denver Anschutz Medical Campus, Denver, CO
| | - Kurt G Beam
- Department of Physiology and Biophysics, University of Colorado Denver Anschutz Medical Campus, Denver, CO
| | - Symeon Papadopoulos
- Institute of Vegetative Physiology, University Hospital of Cologne, Cologne, Germany
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5
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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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6
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Stanczyk PJ, Lai FA, Zissimopoulos S. Genetic and Biochemical Approaches for In Vivo and In Vitro Assessment of Protein Oligomerization: The Ryanodine Receptor Case Study. J Vis Exp 2016. [PMID: 27500320 PMCID: PMC5065051 DOI: 10.3791/54271] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Oligomerization is often a structural requirement for proteins to accomplish their specific cellular function. For instance, tetramerization of the ryanodine receptor (RyR) is necessary for the formation of a functional Ca2+ release channel pore. Here, we describe detailed protocols for the assessment of protein self-association, including yeast two-hybrid (Y2H), co-immunoprecipitation (co-IP) and chemical cross-linking assays. In the Y2H system, protein self-interaction is detected by β-galactosidase assay in yeast co-expressing GAL4 bait and target fusions of the test protein. Protein self-interaction is further assessed by co-IP using HA- and cMyc-tagged fusions of the test protein co-expressed in mammalian HEK293 cells. The precise stoichiometry of the protein homo-oligomer is examined by cross-linking and SDS-PAGE analysis following expression in HEK293 cells. Using these different but complementary techniques, we have consistently observed the self-association of the RyR N-terminal domain and demonstrated its intrinsic ability to form tetramers. These methods can be applied to protein-protein interaction and homo-oligomerization studies of other mammalian integral membrane proteins.
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7
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Abstract
The ryanodine receptor/Ca2+ release channel plays a pivotal role in skeletal and cardiac muscle excitation-contraction coupling. Defective regulation leads to neuromuscular disorders and arrhythmogenic cardiac disease. This mini-review focuses on channel regulation through structural intra- and inter-subunit interactions and their implications in ryanodine receptor pathophysiology.
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8
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Seidel M, Thomas NL, Williams AJ, Lai FA, Zissimopoulos S. Dantrolene rescues aberrant N-terminus intersubunit interactions in mutant pro-arrhythmic cardiac ryanodine receptors. Cardiovasc Res 2014; 105:118-28. [PMID: 25411383 DOI: 10.1093/cvr/cvu240] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
AIMS The ryanodine receptor (RyR2) is an intracellular Ca(2+) release channel essential for cardiac excitation-contraction coupling. Abnormal RyR2 channel function results in the generation of arrhythmias and sudden cardiac death. The present study was undertaken to investigate the mechanistic basis of RyR2 dysfunction in inherited arrhythmogenic cardiac disease. METHODS AND RESULTS We present several lines of complementary evidence, indicating that the arrhythmia-associated L433P mutation disrupts RyR2 N-terminus self-association. A combination of yeast two-hybrid, co-immunoprecipitation, and chemical cross-linking assays collectively demonstrate that a RyR2 N-terminal fragment carrying the L433P mutation displays substantially reduced self-interaction compared with wild type. Moreover, sucrose density gradient centrifugation reveals that the L433P mutation impairs tetramerization of the full-length channel. [(3)H]Ryanodine-binding assays demonstrate that disrupted N-terminal intersubunit interactions within RyR2(L433P) confer an altered sensitivity to Ca(2+) activation. Calcium imaging of RyR2(L433P)-expressing cells reveals substantially prolonged Ca(2+) transients and reduced Ca(2+) store content indicating defective channel closure. Importantly, dantrolene treatment reverses the L433P mutation-induced impairment and restores channel function. CONCLUSION The N-terminus domain constitutes an important structural determinant for the functional oligomerization of RyR2. Our findings are consistent with defective N-terminus self-association as a molecular mechanism underlying RyR2 channel deregulation in inherited arrhythmogenic cardiac disease. Significantly, the therapeutic action of dantrolene may occur via the restoration of normal RyR2 N-terminal intersubunit interactions.
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Affiliation(s)
- Monika Seidel
- Wales Heart Research Institute, Institute of Molecular and Experimental Medicine, Cardiff University School of Medicine, Cardiff CF14 4XN, UK
| | - N Lowri Thomas
- Wales Heart Research Institute, Institute of Molecular and Experimental Medicine, Cardiff University School of Medicine, Cardiff CF14 4XN, UK
| | - Alan J Williams
- Wales Heart Research Institute, Institute of Molecular and Experimental Medicine, Cardiff University School of Medicine, Cardiff CF14 4XN, UK
| | - F Anthony Lai
- Wales Heart Research Institute, Institute of Molecular and Experimental Medicine, Cardiff University School of Medicine, Cardiff CF14 4XN, UK
| | - Spyros Zissimopoulos
- Wales Heart Research Institute, Institute of Molecular and Experimental Medicine, Cardiff University School of Medicine, Cardiff CF14 4XN, UK
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9
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Borko Ľ, Bauerová-Hlinková V, Hostinová E, Gašperík J, Beck K, Lai FA, Zahradníková A, Ševčík J. Structural insights into the human RyR2 N-terminal region involved in cardiac arrhythmias. ACTA CRYSTALLOGRAPHICA. SECTION D, BIOLOGICAL CRYSTALLOGRAPHY 2014; 70:2897-912. [PMID: 25372681 PMCID: PMC4220973 DOI: 10.1107/s1399004714020343] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/20/2014] [Accepted: 09/10/2014] [Indexed: 01/11/2023]
Abstract
Human ryanodine receptor 2 (hRyR2) mediates calcium release from the sarcoplasmic reticulum, enabling cardiomyocyte contraction. The N-terminal region of hRyR2 (amino acids 1-606) is the target of >30 arrhythmogenic mutations and contains a binding site for phosphoprotein phosphatase 1. Here, the solution and crystal structures determined under near-physiological conditions, as well as a homology model of the hRyR2 N-terminal region, are presented. The N-terminus is held together by a unique network of interactions among its three domains, A, B and C, in which the central helix (amino acids 410-437) plays a prominent stabilizing role. Importantly, the anion-binding site reported for the mouse RyR2 N-terminal region is notably absent from the human RyR2. The structure concurs with the differential stability of arrhythmogenic mutations in the central helix (R420W, I419F and I419F/R420W) which are owing to disparities in the propensity of mutated residues to form energetically favourable or unfavourable contacts. In solution, the N-terminus adopts a globular shape with a prominent tail that is likely to involve residues 545-606, which are unresolved in the crystal structure. Docking the N-terminal domains into cryo-electron microscopy maps of the closed and open RyR1 conformations reveals C(α) atom movements of up to 8 Å upon channel gating, and predicts the location of the leucine-isoleucine zipper segment and the interaction site for spinophilin and phosphoprotein phosphatase 1 on the RyR surface.
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Affiliation(s)
- Ľubomír Borko
- Department of Biochemistry and Structural Biology, Institute of Molecular Biology, Slovak Academy of Sciences, Dúbravská cesta 21, 845 51 Bratislava, Slovakia
| | - Vladena Bauerová-Hlinková
- Department of Biochemistry and Structural Biology, Institute of Molecular Biology, Slovak Academy of Sciences, Dúbravská cesta 21, 845 51 Bratislava, Slovakia
| | - Eva Hostinová
- Department of Biochemistry and Structural Biology, Institute of Molecular Biology, Slovak Academy of Sciences, Dúbravská cesta 21, 845 51 Bratislava, Slovakia
| | - Juraj Gašperík
- Department of Biochemistry and Structural Biology, Institute of Molecular Biology, Slovak Academy of Sciences, Dúbravská cesta 21, 845 51 Bratislava, Slovakia
| | - Konrad Beck
- Cardiff University School of Dentistry, Heath Park, Cardiff CF14 4XY, Wales
| | - F. Anthony Lai
- Department of Cardiology, Wales Heart Research Institute, Cardiff University School of Medicine, Cardiff CF14 4XN, Wales
| | - Alexandra Zahradníková
- Department of Biochemistry and Structural Biology, Institute of Molecular Biology, Slovak Academy of Sciences, Dúbravská cesta 21, 845 51 Bratislava, Slovakia
- Department of Muscle Cell Research, Institute of Molecular Physiology and Genetics, Slovak Academy of Sciences, Vlárska 5, 833 34 Bratislava, Slovakia
| | - Jozef Ševčík
- Department of Biochemistry and Structural Biology, Institute of Molecular Biology, Slovak Academy of Sciences, Dúbravská cesta 21, 845 51 Bratislava, Slovakia
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10
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Abstract
Oligomerization of all three mammalian ryanodine receptor isoforms, a structural requirement for normal intracellular Ca2+ release channel function, is displayed by the discrete N-terminal domain which assembles into homo- and hetero-tetramers. This is demonstrated in yeast, mammalian cells and native tissue by complementary yeast two-hybrid, chemical cross-linking and co-immunoprecipitation assays. The IP3 (inositol 1,4,5-trisphosphate) receptor N-terminus (residues 1–667) similarly exhibits tetrameric association as indicated by chemical cross-linking and co-immunoprecipitation assays. The presence of either a 15-residue splice insertion or of the cognate ligand IP3 did not affect tetramerization of the IP3 receptor N-terminus. Thus N-terminus tetramerization appears to be an essential intrinsic property that is conserved in both the ryanodine receptor and IP3 receptor families of mammalian intracellular Ca2+ release channels. Intracellular Ca2+ channels are of paramount importance for numerous cellular processes. In the present paper we report on a novel N-terminus intersubunit interaction, an essential structure–function parameter, which is conserved in both families of intracellular Ca2+ channels.
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11
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Zissimopoulos S, Viero C, Seidel M, Cumbes B, White J, Cheung I, Stewart R, Jeyakumar LH, Fleischer S, Mukherjee S, Thomas NL, Williams AJ, Lai FA. N-terminus oligomerization regulates the function of cardiac ryanodine receptors. J Cell Sci 2013; 126:5042-51. [PMID: 23943880 DOI: 10.1242/jcs.133538] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The ryanodine receptor (RyR) is an ion channel composed of four identical subunits mediating calcium efflux from the endo/sarcoplasmic reticulum of excitable and non-excitable cells. We present several lines of evidence indicating that the RyR2 N-terminus is capable of self-association. A combination of yeast two-hybrid screens, co-immunoprecipitation analysis, chemical crosslinking and gel filtration assays collectively demonstrate that a RyR2 N-terminal fragment possesses the intrinsic ability to oligomerize, enabling apparent tetramer formation. Interestingly, N-terminus tetramerization mediated by endogenous disulfide bond formation occurs in native RyR2, but notably not in RyR1. Disruption of N-terminal inter-subunit interactions within RyR2 results in dysregulation of channel activation at diastolic Ca(2+) concentrations from ryanodine binding and single channel measurements. Our findings suggest that the N-terminus interactions mediating tetramer assembly are involved in RyR channel closure, identifying a crucial role for this structural association in the dynamic regulation of intracellular Ca(2+) release.
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Affiliation(s)
- Spyros Zissimopoulos
- Wales Heart Research Institute, Cardiff University School of Medicine, Cardiff CF14 4XN, UK
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12
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Kimlicka L, Lau K, Tung CC, Van Petegem F. Disease mutations in the ryanodine receptor N-terminal region couple to a mobile intersubunit interface. Nat Commun 2013; 4:1506. [PMID: 23422674 PMCID: PMC3586727 DOI: 10.1038/ncomms2501] [Citation(s) in RCA: 72] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2012] [Accepted: 01/15/2013] [Indexed: 11/14/2022] Open
Abstract
Ryanodine receptors are large channels that release Ca(2+) from the endoplasmic and sarcoplasmic reticulum. Hundreds of RyR mutations can cause cardiac and skeletal muscle disorders, yet detailed mechanisms explaining their effects have been lacking. Here we compare pseudo-atomic models and propose that channel opening coincides with widening of a cytoplasmic vestibule formed by the N-terminal region, thus altering an interface targeted by 20 disease mutations. We solve crystal structures of several disease mutants that affect intrasubunit domain-domain interfaces. Mutations affecting intrasubunit ionic pairs alter relative domain orientations, and thus couple to surrounding interfaces. Buried disease mutations cause structural changes that also connect to the intersubunit contact area. These results suggest that the intersubunit contact region between N-terminal domains is a prime target for disease mutations, direct or indirect, and we present a model whereby ryanodine receptors and inositol-1,4,5-trisphosphate receptors are activated by altering domain arrangements in the N-terminal region.
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Affiliation(s)
- Lynn Kimlicka
- Department of Biochemistry and Molecular Biology, Life Sciences Institute, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z3
| | - Kelvin Lau
- Department of Biochemistry and Molecular Biology, Life Sciences Institute, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z3
| | - Ching-Chieh Tung
- Department of Biochemistry and Molecular Biology, Life Sciences Institute, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z3
| | - Filip Van Petegem
- Department of Biochemistry and Molecular Biology, Life Sciences Institute, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z3
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Bhanumathy C, da Fonseca PCA, Morris EP, Joseph SK. Identification of functionally critical residues in the channel domain of inositol trisphosphate receptors. J Biol Chem 2012; 287:43674-84. [PMID: 23086950 PMCID: PMC3527953 DOI: 10.1074/jbc.m112.415786] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
We have combined alanine mutagenesis and functional assays to identify amino acid residues in the channel domain that are critical for inositol 1,4,5-trisphosphate receptor (IP(3)R) channel function. The residues selected were highly conserved in all three IP(3)R isoforms and were located in the cytosolic end of the S6 pore-lining helix and proximal portion of the C-tail. Two adjacent hydrophobic amino acids (Ile-2588 and Ile-2589) at the putative cytosolic interface of the S6 helix inactivated channel function and could be candidates for the channel gate. Of five negatively charged residues mutated, none completely eliminated channel function. Of five positively charged residues mutated, only one inactivated the channel (Arg-2596). In addition to the previously identified role of a pair of cysteines in the C-tail (Cys-2610 and Cys-2613), a pair of highly conserved histidines (His-2630 and His-2635) were also essential for channel function. Expression of the H2630A and H2635A mutants (but not R2596A) produced receptors with destabilized interactions between the N-terminal fragment and the channel domain. A previously unrecognized association between the cytosolic C-tail and the TM 4,5-loop was demonstrated using GST pulldown assays. However, none of the mutations in the C-tail interfered with this interaction or altered the ability of the C-tail to assemble into dimers. Our present findings and recent information on IP(3)R structure from electron microscopy and crystallography are incorporated into a revised model of channel gating.
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MESH Headings
- Amino Acid Substitution
- Animals
- COS Cells
- Chlorocebus aethiops
- HEK293 Cells
- Humans
- Inositol 1,4,5-Trisphosphate Receptors/chemistry
- Inositol 1,4,5-Trisphosphate Receptors/genetics
- Inositol 1,4,5-Trisphosphate Receptors/metabolism
- Ion Channel Gating/physiology
- Models, Molecular
- Mutation, Missense
- Protein Multimerization/physiology
- Protein Structure, Secondary
- Protein Structure, Tertiary
- Rats
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Affiliation(s)
- Cunnigaiper Bhanumathy
- From the Department of Pathology and Cell Biology, Thomas Jefferson University, Philadelphia, Pennsylvania 19107 and
| | - Paula C. A. da Fonseca
- the Institute for Cancer Research, Chester Beatty Laboratories, London, SW3 6JB, United Kingdom
| | - Edward P. Morris
- the Institute for Cancer Research, Chester Beatty Laboratories, London, SW3 6JB, United Kingdom
| | - Suresh K. Joseph
- From the Department of Pathology and Cell Biology, Thomas Jefferson University, Philadelphia, Pennsylvania 19107 and
- To whom correspondence should be addressed: Dept. of Pathology & Cell Biology, Rm. 230A JAH, 1020 Locust St., Philadelphia, PA 19107. Tel.: 215-503-1222; E-mail:
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14
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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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15
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Jiang D, Jones PP, Davis DR, Gow R, Green MS, Birnie DH, Chen SRW, Gollob MH. Characterization of a novel mutation in the cardiac ryanodine receptor that results in catecholaminergic polymorphic ventricular tachycardia. Channels (Austin) 2010; 4:302-10. [PMID: 20676041 DOI: 10.4161/chan.4.4.12666] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Catecholaminergic polymorphic ventricular tachycardia (CPVT) is an arrhythmogenic disease that manifests as syncope or sudden death during high adrenergic tone in the absence of structural heart defects. It is primarily caused by mutations in the cardiac ryanodine receptor (RyR2). The mechanism by which these mutations cause arrhythmia remains controversial, with discrepant findings related to the role of the RyR2 binding protein FKBP12.6. The purpose of this study was to characterize a novel RyR2 mutation identified in a kindred with clinically diagnosed CPVT. Single-strand conformational polymorphism analysis and direct DNA sequencing were used to screen the RyR2 gene for mutations. Site-directed mutagenesis was employed to introduce the mutation into the mouse RyR2 cDNA. The impact of the mutation on the interaction between RyR2 and a 12.6 kDa FK506 binding protein (FKBP12.6) was determined by immunoprecipitation and immunoblotting and its effect on RyR2 function was characterized by single cell Ca(2+) imaging and [(3)H]ryanodine binding. A novel CPVT mutation, E189D, was identified. The E189D mutation does not alter the affinity of the channel for FKBP12.6, but it increases the propensity for store-overload-induced Ca(2+) release (SOICR). Furthermore, the E189D mutation enhances the basal channel activity of RyR2 and its sensitivity to activation by caffeine. The E189D RyR2 mutation is causative for CPVT and functionally increases the propensity for SOICR without altering the affinity for FKBP12.6. These observations strengthen the notion that enhanced SOICR, but not altered FKBP12.6 binding, is a common mechanism by which RyR2 mutations cause arrhythmias.
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Affiliation(s)
- Dawei Jiang
- Department of Physiology and Pharmacology, University of Calgary, Calgary, AB, Canada
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16
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Ghosh A, Nandy A, Nandy P. Computational analysis and determination of a highly conserved surface exposed segment in H5N1 avian flu and H1N1 swine flu neuraminidase. BMC STRUCTURAL BIOLOGY 2010; 10:6. [PMID: 20170556 PMCID: PMC2836360 DOI: 10.1186/1472-6807-10-6] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/07/2009] [Accepted: 02/22/2010] [Indexed: 01/30/2023]
Abstract
Background Catalytic activity of influenza neuraminidase (NA) facilitates elution of progeny virions from infected cells and prevents their self-aggregation mediated by the catalytic site located in the body region. Research on the active site of the molecule has led to development of effective inhibitors like oseltamivir, zanamivir etc, but the high rate of mutation and interspecies reassortment in viral sequences and the recent reports of oseltamivir resistant strains underlines the importance of determining additional target sites for developing future antiviral compounds. In a recent computational study of 173 H5N1 NA gene sequences we had identified a 50-base highly conserved region in 3'-terminal end of the NA gene. Results We extend the graphical and numerical analyses to a larger number of H5N1 NA sequences (514) and H1N1 swine flu sequences (425) accessed from GenBank. We use a 2D graphical representation model for the gene sequences and a Graphical Sliding Window Method (GSWM) for protein sequences scanning the sequences as a block of 16 amino acids at a time. Using a protein sequence descriptor defined in our model, the protein sliding scan method allowed us to compare the different strains for block level variability, which showed significant statistical correlation to average solvent accessibility of the residue blocks; single amino acid position variability results in no correlation, indicating the impact of stretch variability in chemical environment. Close to the C-terminal end the GSWM showed less descriptor-variability with increased average solvent accessibility (ASA) that is also supported by conserved predicted secondary structure of 3' terminal RNA and visual evidence from 3D crystallographic structure. Conclusion The identified terminal segment, strongly conserved in both RNA and protein sequences, is especially significant as it is surface exposed and structural chemistry reveals the probable role of this stretch in tetrameric stabilization. It could also participate in other biological processes associated with conserved surface residues. A RNA double hairpin secondary structure found in this segment in a majority of the H5N1 strains also supports this observation. In this paper we propose this conserved region as a probable site for designing inhibitors for broad-spectrum pandemic control of flu viruses with similar NA structure.
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Affiliation(s)
- Ambarnil Ghosh
- Physics Department, Jadavpur University, Kolkata, India.
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17
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Bauerová-Hlinková V, Hostinová E, Gasperík J, Beck K, Borko L, Lai FA, Zahradníková A, Sevcík J. Bioinformatic mapping and production of recombinant N-terminal domains of human cardiac ryanodine receptor 2. Protein Expr Purif 2010; 71:33-41. [PMID: 20045464 PMCID: PMC2845809 DOI: 10.1016/j.pep.2009.12.014] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2009] [Revised: 12/18/2009] [Accepted: 12/29/2009] [Indexed: 12/17/2022]
Abstract
We report the domain analysis of the N-terminal region (residues 1-759) of the human cardiac ryanodine receptor (RyR2) that encompasses one of the discrete RyR2 mutation clusters associated with catecholaminergic polymorphic ventricular tachycardia (CPVT1) and arrhythmogenic right ventricular dysplasia (ARVD2). Our strategy utilizes a bioinformatics approach complemented by protein expression, solubility analysis and limited proteolytic digestion. Based on the bioinformatics analysis, we designed a series of specific RyR2 N-terminal fragments for cloning and overexpression in Escherichia coli. High yields of soluble proteins were achieved for fragments RyR2(1-606)xHis(6), RyR2(391-606)xHis(6), RyR2(409-606)xHis(6), Trx.RyR2(384-606)xHis(6), TrxxRyR2(391-606)xHis(6) and Trx.RyR2(409-606)xHis(6). The folding of RyR2(1-606)xHis(6) was analyzed by circular dichroism spectroscopy resulting in alpha-helix and beta-sheet content of approximately 23% and approximately 29%, respectively, at temperatures up to 35 degrees C, which is in agreement with sequence based secondary structure predictions. Tryptic digestion of the largest recombinant protein, RyR2(1-606)xHis(6), resulted in the appearance of two specific subfragments of approximately 40 and 25 kDa. The 25 kDa fragment exhibited greater stability. Hybridization with anti-His(6).Tag antibody indicated that RyR2(1-606)xHis(6) is cleaved from the N-terminus and amino acid sequencing of the proteolytic fragments revealed that digestion occurred after residues 259 and 384, respectively.
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Affiliation(s)
- Vladena Bauerová-Hlinková
- Department of Protein Structure and Function, Institute of Molecular Biology, Slovak Academy of Sciences, Dúbravská Cesta 21, 845 51 Bratislava, Slovakia
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18
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Homer and the ryanodine receptor. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2009; 39:91-102. [PMID: 19513708 DOI: 10.1007/s00249-009-0494-1] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/23/2009] [Revised: 05/15/2009] [Accepted: 05/18/2009] [Indexed: 10/20/2022]
Abstract
Homer proteins have recently been identified as novel high-affinity ligands that modulate ryanodine receptor (RyR) Ca(2+) release channels in heart and skeletal muscle, through an EVH1 domain which binds to proline-rich regions in target proteins. Many Homer proteins can also self-associate through a coiled-coil domain that allows their multimerisation. In other tissues, especially neurons, Homer anchors proteins embedded in the surface membrane to the Ca(2+) release channel in the endoplasmic reticulum and can anchor membrane or cytosolic proteins to the cytoskeleton. Although this anchoring aspect of Homer function has not been extensively investigated in muscle, there are consensus sequences for Homer binding in the RyR and on many of the proteins that it interacts with in the massive RyR ion channel complex. In this review we explore the potential of Homer to contribute to a variety of cell processes in muscle and neurons that also involve RyR channels.
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19
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Blayney LM, Lai FA. Ryanodine receptor-mediated arrhythmias and sudden cardiac death. Pharmacol Ther 2009; 123:151-77. [PMID: 19345240 PMCID: PMC2704947 DOI: 10.1016/j.pharmthera.2009.03.006] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2009] [Accepted: 03/03/2009] [Indexed: 12/25/2022]
Abstract
The cardiac ryanodine receptor-Ca2+ release channel (RyR2) is an essential sarcoplasmic reticulum (SR) transmembrane protein that plays a central role in excitation–contraction coupling (ECC) in cardiomyocytes. Aberrant spontaneous, diastolic Ca2+ leak from the SR due to dysfunctional RyR2 contributes to the formation of delayed after-depolarisations, which are thought to underlie the fatal arrhythmia that occurs in both heart failure (HF) and in catecholaminergic polymorphic ventricular tachycardia (CPVT). CPVT is an inherited disorder associated with mutations in either the RyR2 or a SR luminal protein, calsequestrin. RyR2 shows normal function at rest in CPVT but the RyR2 dysfunction is unmasked by physical exercise or emotional stress, suggesting abnormal RyR2 activation as an underlying mechanism. Several potential mechanisms have been advanced to explain the dysfunctional RyR2 observed in HF and CPVT, including enhanced RyR2 phosphorylation status, altered RyR2 regulation at luminal/cytoplasmic sites and perturbed RyR2 intra/inter-molecular interactions. This review considers RyR2 dysfunction in the context of the structural and functional modulation of the channel, and potential therapeutic strategies to stabilise RyR2 function in cardiac pathology.
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Affiliation(s)
- Lynda M Blayney
- Wales Heart Research Institute, Cardiff University School of Medicine, Cardiff CF144XN, UK.
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20
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Rigoard P, Buffenoir K, Wager M, Bauche S, Giot JP, Lapierre F. [Molecular architecture of the sarcoplasmic reticulum and its role in the ECC]. Neurochirurgie 2009; 55 Suppl 1:S83-91. [PMID: 19233437 DOI: 10.1016/j.neuchi.2008.05.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2008] [Accepted: 05/09/2008] [Indexed: 11/16/2022]
Abstract
The sarcoplasmic reticulum (SR) plays a fundamental role in excitation-contraction coupling, which propagates the electric signal conversion along the muscle fiber's plasmic membrane to a mechanical event manifested as a muscle contraction. It plays a crucial role in calcium homeostasis and intracellular calcium storage control (storage, liberation and uptake) necessary for fiber muscle contraction and then relaxation. These functions take place at the triad, made up of individualized SR subdomains where the protein-specific organization provides efficient and fast coupling. Ryanodine receptors (RyR) and dihydropyridine receptors (DHPR) mainly act in calcium exchanges in the SR. This particular structural and molecular architecture must be correlated to its functional specificity.
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Affiliation(s)
- P Rigoard
- Service de neurochirurgie, CHU La Milétrie, 2, rue de la Milétrie, BP 577, 86021 Poitiers cedex, France.
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21
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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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22
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Katz G, Arad M, Eldar M. Catecholaminergic polymorphic ventricular tachycardia from bedside to bench and beyond. Curr Probl Cardiol 2009; 34:9-43. [PMID: 19068246 DOI: 10.1016/j.cpcardiol.2008.09.002] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Catecholaminergic polymorphic ventricular tachycardia (CPVT) is a primary electrical myocardial disease characterized by exercise- and stress-related ventricular tachycardia manifested as syncope and sudden death. The disease has a heterogeneous genetic basis, with mutations in the cardiac Ryanodine Receptor channel (RyR2) gene accounting for an autosomal-dominant form (CPVT1) in approximately 50% and mutations in the cardiac calsequestrin gene (CASQ2) accounting for an autosomal-recessive form (CPVT2) in up to 2% of CPVT cases. Both RyR2 and calsequestrin are important participants in the cardiac cellular calcium homeostasis. We review the physiology of the cardiac calcium homeostasis, including the cardiac excitation contraction coupling and myocyte calcium cycling. The pathophysiology of cardiac arrhythmias related to myocyte calcium handling and the effects of different modulators are discussed. The putative derangements in myocyte calcium homeostasis responsible for CPVT, as well as the clinical manifestations and therapeutic options available, are described.
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Mohamed U, Napolitano C, Priori SG. Molecular and Electrophysiological Bases of Catecholaminergic Polymorphic Ventricular Tachycardia. J Cardiovasc Electrophysiol 2007; 18:791-7. [PMID: 17578347 DOI: 10.1111/j.1540-8167.2007.00766.x] [Citation(s) in RCA: 99] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Catecholaminergic polymorphic ventricular tachycardia (CPVT) is an inherited arrhythmogenic disorder characterized by adrenergically mediated polymorphic ventricular tachyarrhythmias. Genetic investigations have identified two variants of the disease: an autosomal dominant form associated with mutations in the gene encoding the cardiac ryanodine receptor (RyR2) and a recessive form associated with homozygous mutations in the gene encoding the cardiac isoform of calsequestrin (CASQ2). Functional characterization of mutations identified in the RyR2 and CASQ2 genes has demonstrated that CPVT are caused by derangements of the control of intracellular calcium. Investigations in a knock-in mouse model have shown that CPVT arrhythmias are initiated by delayed afterdepolarizations and triggered activity. In the present article, we review clinical and molecular understanding of CPVT and discuss the most recent approaches to develop novel therapeutic strategies for the disease.
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Affiliation(s)
- Uwais Mohamed
- Division of Cardiology, Department of Medicine, London Health Science Centre, London, Canada
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24
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Rossi D, De Smet P, Lyfenko A, Galli L, Lorenzini S, Franci D, Petrioli F, Orrico A, Angelini C, Tegazzin V, Dirksen R, Sorrentino V. A truncation in the RYR1 gene associated with central core lesions in skeletal muscle fibres. J Med Genet 2007; 44:e67. [PMID: 17293538 PMCID: PMC2598062 DOI: 10.1136/jmg.2006.043794] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
A novel single-nucleotide deletion in exon 100 of the RYR1 gene, corresponding to deletion of nucleotide 14,510 in the human RyR1 mRNA (c14510delA), was identified in a man with malignant hyperthermia and in his two daughters who were normal for malignant hyperthermia. This deletion results in a RyR1 protein lacking the last 202 amino acid residues. All three subjects heterozygotic for the mutated allele presented with a prevalence of type 1 fibres with central cores, although none experienced clinical signs of myopathy. Expression of the truncated protein resulted in non-functional RYR1 calcium release channels. Expression of wild-type and RyR1(R4836fsX4838) proteins resulted in heterozygotic release channels with overall functional properties similar to those of wild-type RyR1 channels. Nevertheless, small differences in sensitivity to calcium and caffeine were observed in heterotetrameric channels, which also presented an altered assembly/stability in sucrose-gradient centrifugation analysis. Altogether, these data suggest that altered RYR1 tetramer assembly/stability coupled with subtle chronic changes in Ca2+ homoeostasis over the long term may contribute to the development of core lesions and incomplete malignant hyperthermia susceptibility penetrance in individuals carrying this novel RYR1 mutation.
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Affiliation(s)
- Daniela Rossi
- Molecular Medicine Section, Department of Neuroscience, University of Siena, Siena 53100, Italy.
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Zissimopoulos S, West DJ, Williams AJ, Lai FA. Ryanodine receptor interaction with the SNARE-associated protein snapin. J Cell Sci 2007; 119:2386-97. [PMID: 16723744 DOI: 10.1242/jcs.02936] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The ryanodine receptor (RyR) is a widely expressed intracellular calcium (Ca(2+))-release channel regulating processes such as muscle contraction and neurotransmission. Snapin, a ubiquitously expressed SNARE-associated protein, has been implicated in neurotransmission. Here, we report the identification of snapin as a novel RyR2-interacting protein. Snapin binds to a 170-residue predicted ryanodine receptor cytosolic loop (RyR2 residues 4596-4765), containing a hydrophobic segment required for snapin interaction. Ryanodine receptor binding of snapin is not isoform specific and is conserved in homologous RyR1 and RyR3 fragments. Consistent with peptide fragment studies, snapin interacts with the native ryanodine receptor from skeletal muscle, heart and brain. The snapin-RyR1 association appears to sensitise the channel to Ca(2+) activation in [(3)H]ryanodine-binding studies. Deletion analysis indicates that the ryanodine receptor interacts with the snapin C-terminus, the same region as the SNAP25-binding site. Competition experiments with native ryanodine receptor and SNAP25 suggest that these two proteins share an overlapping binding site on snapin. Thus, regulation of the association between ryanodine receptor and snapin might constitute part of the elusive molecular mechanism by which ryanodine-sensitive Ca(2+) stores modulate neurosecretion.
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Affiliation(s)
- Spyros Zissimopoulos
- Wales Heart Research Institute, Department of Cardiology, Cardiff University School of Medicine, Heath Park, UK.
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26
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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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27
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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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Schug ZT, Joseph SK. The Role of the S4-S5 Linker and C-terminal Tail in Inositol 1,4,5-Trisphosphate Receptor Function. J Biol Chem 2006; 281:24431-40. [PMID: 16815846 DOI: 10.1074/jbc.m604190200] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In previous studies we have suggested that spatial proximity of the C- and N-terminal domains of inositol 1,4,5-trisphosphate receptors (IP(3)Rs) may be critical for the channel gating mechanism. In the present study we have examined the sites of C-N interaction in more detail. We report that deletion mutations within the S4-S5 linker (amino acids 2418-2437) prevent co-immunoprecipitation of the C- and N-terminal domains, inhibit channel activity and enhance IP(3) binding. We also show that a region of the C-terminal tail (amino acids 2694-2721), predicted to be a coiled-coil, is also required for channel activity. Circular dichroism spectroscopy and gel filtration studies confirm that this region has a helical structure with the ability to form tetramers. We propose a model in which IP(3)-induced conformational changes in the N-terminal domain are mechanically transmitted to the opening of the pore through an attachment to the S4-S5 linker. The coiled-coil domain in the C-terminal tail may play a critical role in maintaining the structural integrity of the channel.
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Affiliation(s)
- Zachary T Schug
- Department of Pathology, Cell Biology, and Anatomy, Thomas Jefferson University School of Medicine, Philadelphia, Pennsylvania 19107, USA
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29
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Pouliquin P, Pace SM, Curtis SM, Harvey PJ, Gallant EM, Zorzato F, Casarotto MG, Dulhunty AF. Effects of an alpha-helical ryanodine receptor C-terminal tail peptide on ryanodine receptor activity: modulation by Homer. Int J Biochem Cell Biol 2006; 38:1700-15. [PMID: 16725367 DOI: 10.1016/j.biocel.2006.03.020] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2005] [Revised: 03/22/2006] [Accepted: 03/29/2006] [Indexed: 11/30/2022]
Abstract
We have determined the structure of a domain peptide corresponding to the extreme 19 C-terminal residues of the ryanodine receptor Ca2+ release channel. We examined functional interactions between the peptide and the channel, in the absence and in the presence of the regulatory protein Homer. The peptide was partly alpha-helical and structurally homologous to the C-terminal end of the T1 domain of voltage-gated K+ channels. The peptide (0.1-10 microM) inhibited skeletal ryanodine receptor channels when the cytoplasmic Ca2+ concentration was 1 microM; but with 10 microM cytoplasmic Ca2+, skeletal ryanodine receptors were activated by < or = 1.0 microM peptide and inhibited by 10 microM peptide. Cardiac ryanodine receptors on the other hand were inhibited by all peptide concentrations, at both Ca2+ concentrations. When channels did open in the presence of the peptide, they were more likely to open to substate levels. The inhibition and increased fraction of openings to subconductance levels suggested that the domain peptide might destabilise inter-domain interactions that involve the C-terminal tail. We found that Homer 1b not only interacts with the channels, but reduces the inhibitory action of the C-terminal tail peptide, perhaps by stabilizing inter-domain interactions and preventing their disruption.
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Affiliation(s)
- Pierre Pouliquin
- Division of Molecular Bioscience, JCSMR and RSC, ANU, Canberra, ACT 2601, Australia
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Priori SG, Napolitano C. Cardiac and skeletal muscle disorders caused by mutations in the intracellular Ca2+ release channels. J Clin Invest 2005; 115:2033-8. [PMID: 16075044 PMCID: PMC1180555 DOI: 10.1172/jci25664] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Here we review the current knowledge about the mutations of the gene encoding the cardiac ryanodine receptor (RyR2) that cause cardiac arrhythmias. Similarities between the mutations identified in the RyR2 gene and those found in the gene RyR1 that cause malignant hyperthermia and central core disease are discussed. In vitro functional characterization of RyR1 and RyR2 mutants is reviewed, with a focus on the contribution that in vitro expression studies have made to our understanding of related human diseases.
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Affiliation(s)
- Silvia G Priori
- Molecular Cardiology, Istituto di Ricovero e Cura a Carattere Scientifico Fondazione Maugeri, Pavia, Italy.
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George CH, Jundi H, Thomas NL, Scoote M, Walters N, Williams AJ, Lai FA. Ryanodine receptor regulation by intramolecular interaction between cytoplasmic and transmembrane domains. Mol Biol Cell 2004; 15:2627-38. [PMID: 15047862 PMCID: PMC420088 DOI: 10.1091/mbc.e03-09-0688] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Ryanodine receptors (RyR) function as Ca(2+) channels that regulate Ca(2+) release from intracellular stores to control a diverse array of cellular processes. The massive cytoplasmic domain of RyR is believed to be responsible for regulating channel function. We investigated interaction between the transmembrane Ca(2+)-releasing pore and a panel of cytoplasmic domains of the human cardiac RyR in living cells. Expression of eGFP-tagged RyR constructs encoding distinct transmembrane topological models profoundly altered intracellular Ca(2+) handling and was refractory to modulation by ryanodine, FKBP12.6 and caffeine. The impact of coexpressing dsRed-tagged cytoplasmic domains of RyR2 on intracellular Ca(2+) phenotype was assessed using confocal microscopy coupled with parallel determination of in situ protein: protein interaction using fluorescence resonance energy transfer (FRET). Dynamic interactions between RyR cytoplasmic and transmembrane domains were mediated by amino acids 3722-4610 (Interacting or "I"-domain) which critically modulated intracellular Ca(2+) handling and restored RyR sensitivity to caffeine activation. These results provide compelling evidence that specific interaction between cytoplasmic and transmembrane domains is an important mechanism in the intrinsic modulation of RyR Ca(2+) release channels.
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Affiliation(s)
- Christopher H George
- Wales Heart Research Institute, Department of Cardiology, University of Wales College of Medicine, Cardiff, United Kingdom CF14 4XN.
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