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Marabelli C, Santiago DJ, Priori SG. The Structural-Functional Crosstalk of the Calsequestrin System: Insights and Pathological Implications. Biomolecules 2023; 13:1693. [PMID: 38136565 PMCID: PMC10741413 DOI: 10.3390/biom13121693] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2023] [Revised: 11/14/2023] [Accepted: 11/21/2023] [Indexed: 12/24/2023] Open
Abstract
Calsequestrin (CASQ) is a key intra-sarcoplasmic reticulum Ca2+-handling protein that plays a pivotal role in the contraction of cardiac and skeletal muscles. Its Ca2+-dependent polymerization dynamics shape the translation of electric excitation signals to the Ca2+-induced contraction of the actin-myosin architecture. Mutations in CASQ are linked to life-threatening pathological conditions, including tubular aggregate myopathy, malignant hyperthermia, and Catecholaminergic Polymorphic Ventricular Tachycardia (CPVT). The variability in the penetrance of these phenotypes and the lack of a clear understanding of the disease mechanisms associated with CASQ mutations pose a major challenge to the development of effective therapeutic strategies. In vitro studies have mainly focused on the polymerization and Ca2+-buffering properties of CASQ but have provided little insight into the complex interplay of structural and functional changes that underlie disease. In this review, the biochemical and structural natures of CASQ are explored in-depth, while emphasizing their direct and indirect consequences for muscle Ca2+ physiology. We propose a novel functional classification of CASQ pathological missense mutations based on the structural stability of the monomer, dimer, or linear polymer conformation. We also highlight emerging similarities between polymeric CASQ and polyelectrolyte systems, emphasizing the potential for the use of this paradigm to guide further research.
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Affiliation(s)
- Chiara Marabelli
- Department of Molecular Medicine, University of Pavia, 27100 Pavia, Italy;
- Laboratory of Molecular Cardiology, IRCCS ICS Maugeri, 27100 Pavia, Italy
- Centro Nacional de Investigaciones Cardiovasculares Carlos III (CNIC), 28029 Madrid, Spain;
| | - Demetrio J. Santiago
- Centro Nacional de Investigaciones Cardiovasculares Carlos III (CNIC), 28029 Madrid, Spain;
| | - Silvia G. Priori
- Department of Molecular Medicine, University of Pavia, 27100 Pavia, Italy;
- Laboratory of Molecular Cardiology, IRCCS ICS Maugeri, 27100 Pavia, Italy
- Centro Nacional de Investigaciones Cardiovasculares Carlos III (CNIC), 28029 Madrid, Spain;
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2
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Eisner D, Neher E, Taschenberger H, Smith G. Physiology of intracellular calcium buffering. Physiol Rev 2023; 103:2767-2845. [PMID: 37326298 DOI: 10.1152/physrev.00042.2022] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2022] [Revised: 05/08/2023] [Accepted: 06/11/2023] [Indexed: 06/17/2023] Open
Abstract
Calcium signaling underlies much of physiology. Almost all the Ca2+ in the cytoplasm is bound to buffers, with typically only ∼1% being freely ionized at resting levels in most cells. Physiological Ca2+ buffers include small molecules and proteins, and experimentally Ca2+ indicators will also buffer calcium. The chemistry of interactions between Ca2+ and buffers determines the extent and speed of Ca2+ binding. The physiological effects of Ca2+ buffers are determined by the kinetics with which they bind Ca2+ and their mobility within the cell. The degree of buffering depends on factors such as the affinity for Ca2+, the Ca2+ concentration, and whether Ca2+ ions bind cooperatively. Buffering affects both the amplitude and time course of cytoplasmic Ca2+ signals as well as changes of Ca2+ concentration in organelles. It can also facilitate Ca2+ diffusion inside the cell. Ca2+ buffering affects synaptic transmission, muscle contraction, Ca2+ transport across epithelia, and the killing of bacteria. Saturation of buffers leads to synaptic facilitation and tetanic contraction in skeletal muscle and may play a role in inotropy in the heart. This review focuses on the link between buffer chemistry and function and how Ca2+ buffering affects normal physiology and the consequences of changes in disease. As well as summarizing what is known, we point out the many areas where further work is required.
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Affiliation(s)
- David Eisner
- Division of Cardiovascular Sciences, University of Manchester, Manchester, United Kingdom
| | - Erwin Neher
- Membrane Biophysics Laboratory, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany
- Cluster of Excellence "Multiscale Bioimaging: from Molecular Machines to Networks of Excitable Cells" (MBExC), University of Göttingen, Göttingen, Germany
| | - Holger Taschenberger
- Department of Molecular Neurobiology, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany
| | - Godfrey Smith
- School of Cardiovascular and Metabolic Health, College of Medical, Veterinary, and Life Sciences, University of Glasgow, Glasgow, United Kingdom
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3
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Ryan T, Roberts JD. Emerging Targeted Therapies for Inherited Cardiomyopathies and Arrhythmias. Card Electrophysiol Clin 2023; 15:261-271. [PMID: 37558297 DOI: 10.1016/j.ccep.2023.04.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/11/2023]
Abstract
Inherited cardiomyopathy and arrhythmia syndromes are associated with significant morbidity and mortality, particularly in young people. Medical management of these conditions has primarily been limited to agents previously developed for more common forms of heart disease and not tailored to their distinct pathophysiology. As our understanding of their underlying genetics and disease mechanisms has improved, an era of targeted therapies for these rare conditions has begun to emerge. In recent years, several novel agents have been developed and tested in preclinical models and, in some cases, have advanced to both the clinical trial and clinical approval stages with exciting results. These new treatments are derived from multiple classes of therapeutics, including small molecules, antisense oligonucleotides, small interfering RNAs, adeno-associated virus-mediated gene therapies, and in vivo gene editing. Collectively, they carry the promise of revolutionizing management of affected patients and their families.
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Affiliation(s)
- Tammy Ryan
- McMaster University, Hamilton, Ontario, Canada; Department of Medicine, Division of Cardiology, DBCVSRI, Hamilton General Hospital, Room C3-121, 237 Barton Street East, Hamilton, Ontario L8L2X2, Canada
| | - Jason D Roberts
- McMaster University, Hamilton, Ontario, Canada; DBCVSRI, Room C3-111, 237 Barton Street East, Hamilton, Ontario L8L2X2, Canada; Population Health Research Institute and Hamilton Health Sciences, Hamilton, Ontario, Canada.
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4
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Pérez PR, Hylind RJ, Roston TM, Bezzerides VJ, Abrams DJ. Gene Therapy for Catecholaminergic Polymorphic Ventricular Tachycardia. Heart Lung Circ 2023; 32:790-797. [PMID: 37032191 DOI: 10.1016/j.hlc.2023.01.018] [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: 07/13/2022] [Revised: 10/13/2022] [Accepted: 01/04/2023] [Indexed: 04/11/2023]
Abstract
Over the last three decades, the genetic basis of various inherited arrhythmia syndromes has been elucidated, providing key insights into cardiomyocyte biology and various regulatory pathways associated with cellular excitation, contraction, and repolarisation. As varying techniques to manipulate genetic sequence, gene expression, and different cellular pathways have become increasingly defined and understood, the potential to apply various gene-based therapies to inherited arrhythmia has been explored. The promise of gene therapy has generated significant interest in the medical and lay press, providing hope for sufferers of seemingly incurable disorders to imagine a future without repeated medical intervention, and, in the case of various cardiac disorders, without the risk of sudden death. In this review, we focus on catecholaminergic polymorphic ventricular tachycardia (CPVT), discussing the clinical manifestations, genetic basis, and molecular biology, together with current avenues of research related to gene therapy.
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Affiliation(s)
- Paloma Remior Pérez
- Center for Cardiovascular Genetics, Boston Children's Hospital, Harvard Medical School, Boston MA, USA; Department of Cardiology, Hospital Universitario Puerta de Hierro, Madrid, Spain
| | - Robyn J Hylind
- Center for Cardiovascular Genetics, Boston Children's Hospital, Harvard Medical School, Boston MA, USA
| | - Thomas M Roston
- Center for Cardiovascular Genetics, Boston Children's Hospital, Harvard Medical School, Boston MA, USA; Clinician Investigator Program, The University of British Columbia, Vancouver, Canada
| | - Vassilios J Bezzerides
- Center for Cardiovascular Genetics, Boston Children's Hospital, Harvard Medical School, Boston MA, USA.
| | - Dominic J Abrams
- Center for Cardiovascular Genetics, Boston Children's Hospital, Harvard Medical School, Boston MA, USA.
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Paudel R, Jafri MS, Ullah A. Pacing Dynamics Determines the Arrhythmogenic Mechanism of the CPVT2-Causing CASQ2 G112+5X Mutation in a Guinea Pig Ventricular Myocyte Computational Model. Genes (Basel) 2022; 14:23. [PMID: 36672764 PMCID: PMC9858930 DOI: 10.3390/genes14010023] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2022] [Revised: 12/05/2022] [Accepted: 12/20/2022] [Indexed: 12/25/2022] Open
Abstract
Calsequestrin Type 2 (CASQ2) is a high-capacity, low-affinity, Ca2+-binding protein expressed in the sarcoplasmic reticulum (SR) of the cardiac myocyte. Mutations in CASQ2 have been linked to the arrhythmia catecholaminergic polymorphic ventricular tachycardia (CPVT2) that occurs with acute emotional stress or exercise can result in sudden cardiac death (SCD). CASQ2G112+5X is a 16 bp (339-354) deletion CASQ2 mutation that prevents the protein expression due to premature stop codon. Understanding the subcellular mechanisms of CPVT2 is experimentally challenging because the occurrence of arrhythmia is rare. To obtain an insight into the characteristics of this rare disease, simulation studies using a local control stochastic computational model of the Guinea pig ventricular myocyte investigated how the mutant CASQ2s may be responsible for the development of an arrhythmogenic episode under the condition of β-adrenergic stimulation or in the slowing of heart rate afterward once β-adrenergic stimulation ceases. Adjustment of the computational model parameters based upon recent experiments explore the functional changes caused by the CASQ2 mutation. In the simulation studies under rapid pacing (6 Hz), electromechanically concordant cellular alternans appeared under β-adrenergic stimulation in the CPVT mutant but not in the wild-type nor in the non-β-stimulated mutant. Similarly, the simulations of accelerating pacing from slow to rapid and back to the slow pacing did not display alternans but did generate early afterdepolarizations (EADs) during the period of second slow pacing subsequent acceleration of rapid pacing.
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Affiliation(s)
- Roshan Paudel
- School of Systems Biology, George Mason University, Fairfax, VA 22030, USA
- School of Computer, Mathematical, and Natural Sciences, Morgan State University, Baltimore, MD 21251, USA
| | - Mohsin Saleet Jafri
- School of Systems Biology, George Mason University, Fairfax, VA 22030, USA
- Center for Biomedical Engineering and Technology, University of Maryland School of Medicine, Baltimore, MD 20201, USA
| | - Aman Ullah
- School of Systems Biology, George Mason University, Fairfax, VA 22030, USA
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Wleklinski MJ, Kryshtal DO, Kim K, Parikh SS, Blackwell DJ, Marty I, Iyer VR, Knollmann BC. Impaired Dynamic Sarcoplasmic Reticulum Ca Buffering in Autosomal Dominant CPVT2. Circ Res 2022; 131:673-686. [PMID: 36102198 PMCID: PMC9529867 DOI: 10.1161/circresaha.121.320661] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
BACKGROUND Catecholaminergic polymorphic ventricular tachycardia (CPVT) is a potentially lethal cardiac arrhythmia syndrome triggered by catecholamines released during exercise, stress, or sudden emotion. Variants in the calsequestrin-2 gene (CASQ2), encoding the major calcium (Ca) binding protein in the sarcoplasmic reticulum (SR), are the second most common cause of CPVT. Recently, several CASQ2 gene variants, such as CASQ2-K180R, have been linked to an autosomal dominant form of Casq2-linked CPVT (CPVT2), but the underlying mechanism is not known. METHODS A K180R mouse model was generated using CRIPSR/Cas9. Heterozygous and homozygous K180R mice were studied using telemetry ECG recordings in vivo. Ventricular cardiomyocytes were isolated and studied using fluorescent Ca indicators and patch clamp. Expression levels and localization of SR Ca-handling proteins were evaluated using Western blotting and immunostaining. Intra-SR Ca kinetics were quantified using low-affinity Ca indicators. RESULTS K180R mice exhibit an autosomal dominant CPVT phenotype following exercise or catecholamine stress. Upon catecholamine stress, K180R ventricular cardiomyocytes exhibit increased spontaneous SR Ca release events, triggering delayed afterdepolarizations and spontaneous beats. K180R had no effect on levels of Casq2, Casq2 polymers, or other SR Ca-handling proteins. Intra-SR Ca measurements revealed that K180R impaired dynamic intra-SR Ca buffering, resulting in a more rapid rise of free Ca in the SR during diastole. Steady-state SR Ca buffering and total SR Ca content were not changed. Consistent with the reduced dynamic intra-SR buffering, K180R causes reduced SR Ca release refractoriness. CONCLUSIONS CASQ2-K180R causes CPVT2 via a heretofore unknown mechanism that differs from CASQ2 variants associated with autosomal recessive CPVT2. Unlike autosomal recessive CASQ2 variants, K180R impairs the dynamic buffering of Ca within the SR without affecting total SR Ca content or Casq2 protein levels. Our data provide insight into the molecular mechanism underlying autosomal dominant CPVT2.
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Affiliation(s)
- Matthew J Wleklinski
- Vanderbilt Center for Arrhythmia Research and Therapeutics, Division of Clinical Pharmacology, Vanderbilt University Medical Center, Nashville, TN (M.J.W., D.O.K., K.K., S.S.P., D.J.B., B.C.K.)
| | - Dmytro O Kryshtal
- Vanderbilt Center for Arrhythmia Research and Therapeutics, Division of Clinical Pharmacology, Vanderbilt University Medical Center, Nashville, TN (M.J.W., D.O.K., K.K., S.S.P., D.J.B., B.C.K.)
| | - Kyungsoo Kim
- Vanderbilt Center for Arrhythmia Research and Therapeutics, Division of Clinical Pharmacology, Vanderbilt University Medical Center, Nashville, TN (M.J.W., D.O.K., K.K., S.S.P., D.J.B., B.C.K.)
| | - Shan S Parikh
- Vanderbilt Center for Arrhythmia Research and Therapeutics, Division of Clinical Pharmacology, Vanderbilt University Medical Center, Nashville, TN (M.J.W., D.O.K., K.K., S.S.P., D.J.B., B.C.K.)
| | - Daniel J Blackwell
- Vanderbilt Center for Arrhythmia Research and Therapeutics, Division of Clinical Pharmacology, Vanderbilt University Medical Center, Nashville, TN (M.J.W., D.O.K., K.K., S.S.P., D.J.B., B.C.K.)
| | - Isabelle Marty
- University Grenoble Alpes, Inserm, U1216, Grenoble Institut Neurosciences, Grenoble, France (I.M.)
| | - V Ramesh Iyer
- Division of Cardiology, Children's Hospital of Philadelphia, Perelman School of Medicine at the University of Pennsylvania (V.R.I.)
| | - Bjӧrn C Knollmann
- Vanderbilt Center for Arrhythmia Research and Therapeutics, Division of Clinical Pharmacology, Vanderbilt University Medical Center, Nashville, TN (M.J.W., D.O.K., K.K., S.S.P., D.J.B., B.C.K.)
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7
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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: 10] [Impact Index Per Article: 5.0] [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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8
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Pengelly RJ, Bakhtiar D, Borovská I, Královičová J, Vořechovský I. Exonic splicing code and protein binding sites for calcium. Nucleic Acids Res 2022; 50:5493-5512. [PMID: 35474482 PMCID: PMC9177970 DOI: 10.1093/nar/gkac270] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2022] [Revised: 04/01/2022] [Accepted: 04/05/2022] [Indexed: 11/12/2022] Open
Abstract
Auxilliary splicing sequences in exons, known as enhancers (ESEs) and silencers (ESSs), have been subject to strong selection pressures at the RNA and protein level. The protein component of this splicing code is substantial, recently estimated at ∼50% of the total information within ESEs, but remains poorly understood. The ESE/ESS profiles were previously associated with the Irving-Williams (I-W) stability series for divalent metals, suggesting that the ESE/ESS evolution was shaped by metal binding sites. Here, we have examined splicing activities of exonic sequences that encode protein binding sites for Ca2+, a weak binder in the I-W affinity order. We found that predicted exon inclusion levels for the EF-hand motifs and for Ca2+-binding residues in nonEF-hand proteins were higher than for average exons. For canonical EF-hands, the increase was centred on the EF-hand chelation loop and, in particular, on Ca2+-coordinating residues, with a 1>12>3∼5>9 hierarchy in the 12-codon loop consensus and usage bias at codons 1 and 12. The same hierarchy but a lower increase was observed for noncanonical EF-hands, except for S100 proteins. EF-hand loops preferentially accumulated exon splits in two clusters, one located in their N-terminal halves and the other around codon 12. Using splicing assays and published crosslinking and immunoprecipitation data, we identify candidate trans-acting factors that preferentially bind conserved GA-rich motifs encoding negatively charged amino acids in the loops. Together, these data provide evidence for the high capacity of codons for Ca2+-coordinating residues to be retained in mature transcripts, facilitating their exon-level expansion during eukaryotic evolution.
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Affiliation(s)
- Reuben J Pengelly
- University of Southampton, Faculty of Medicine, Southampton SO16 6YD, UK
| | - Dara Bakhtiar
- University of Southampton, Faculty of Medicine, Southampton SO16 6YD, UK
| | - Ivana Borovská
- Slovak Academy of Sciences, Centre of Biosciences, 840 05 Bratislava, Slovak Republic
| | - Jana Královičová
- University of Southampton, Faculty of Medicine, Southampton SO16 6YD, UK
- Slovak Academy of Sciences, Centre of Biosciences, 840 05 Bratislava, Slovak Republic
- Slovak Academy of Sciences, Institute of Zoology, 845 06 Bratislava, Slovak Republic
| | - Igor Vořechovský
- University of Southampton, Faculty of Medicine, Southampton SO16 6YD, UK
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Sarcoplasmic Reticulum Ca2+ Dysregulation in the Pathophysiology of Inherited Arrhythmia: An Update. Biochem Pharmacol 2022; 200:115059. [DOI: 10.1016/j.bcp.2022.115059] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2022] [Revised: 04/18/2022] [Accepted: 04/19/2022] [Indexed: 11/19/2022]
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10
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The function and regulation of calsequestrin-2: implications in calcium-mediated arrhythmias. Biophys Rev 2022; 14:329-352. [PMID: 35340602 PMCID: PMC8921388 DOI: 10.1007/s12551-021-00914-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2021] [Accepted: 11/14/2021] [Indexed: 01/09/2023] Open
Abstract
Cardiac arrhythmias are life-threatening events in which the heart develops an irregular rhythm. Mishandling of Ca2+ within the myocytes of the heart has been widely demonstrated to be an underlying mechanism of arrhythmogenesis. This includes altered function of the ryanodine receptor (RyR2)-the primary Ca2+ release channel located to the sarcoplasmic reticulum (SR). The spontaneous leak of SR Ca2+ via RyR2 is a well-established contributor in the development of arrhythmic contractions. This leak is associated with increased channel activity in response to changes in SR Ca2+ load. RyR2 activity can be regulated through several avenues, including interactions with numerous accessory proteins. One such protein is calsequestrin-2 (CSQ2), which is the primary Ca2+-buffering protein within the SR. The capacity of CSQ2 to buffer Ca2+ is tightly associated with the ability of the protein to polymerise in response to changing Ca2+ levels. CSQ2 can itself be regulated through phosphorylation and glycosylation modifications, which impact protein polymerisation and trafficking. Changes in CSQ2 modifications are implicated in cardiac pathologies, while mutations in CSQ2 have been identified in arrhythmic patients. Here, we review the role of CSQ2 in arrhythmogenesis including evidence for the indirect and direct regulation of RyR2 by CSQ2, and the consequences of a loss of functional CSQ2 in Ca2+ homeostasis and Ca2+-mediated arrhythmias. Supplementary Information The online version contains supplementary material available at 10.1007/s12551-021-00914-6.
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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: 87] [Impact Index Per Article: 29.0] [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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12
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Wleklinski MJ, Kannankeril PJ, Knollmann BC. Molecular and tissue mechanisms of catecholaminergic polymorphic ventricular tachycardia. J Physiol 2020; 598:2817-2834. [PMID: 32115705 DOI: 10.1113/jp276757] [Citation(s) in RCA: 74] [Impact Index Per Article: 18.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2019] [Accepted: 02/03/2020] [Indexed: 12/21/2022] Open
Abstract
Catecholaminergic polymorphic ventricular tachycardia (CPVT) is a stress-induced cardiac channelopathy that has a high mortality in untreated patients. Our understanding has grown tremendously since CPVT was first described as a clinical syndrome in 1995. It is now established that the deadly arrhythmias are caused by unregulated 'pathological' calcium release from the sarcoplasmic reticulum (SR), the major calcium storage organelle in striated muscle. Important questions remain regarding the molecular mechanisms that are responsible for the pathological calcium release, regarding the tissue origin of the arrhythmic beats that initiate ventricular tachycardia, and regarding optimal therapeutic approaches. At present, mutations in six genes involved in SR calcium release have been identified as the genetic cause of CPVT: RYR2 (encoding ryanodine receptor calcium release channel), CASQ2 (encoding cardiac calsequestrin), TRDN (encoding triadin), CALM1, CALM2 and CALM3 (encoding identical calmodulin protein). Here, we review each CPVT subtype and how CPVT mutations alter protein function, RyR2 calcium release channel regulation, and cellular calcium handling. We then discuss research and hypotheses surrounding the tissue mechanisms underlying CPVT, such as the pathophysiological role of sinus node dysfunction in CPVT, and whether the arrhythmogenic beats originate from the conduction system or the ventricular working myocardium. Finally, we review the treatments that are available for patients with CPVT, their efficacy, and how therapy could be improved in the future.
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Affiliation(s)
- Matthew J Wleklinski
- Vanderbilt Center for Arrhythmia Research and Therapeutics, Division of Clinical Pharmacology, Vanderbilt University Medical Center, Nashville, Tennessee, USA
| | - Prince J Kannankeril
- Vanderbilt Center for Arrhythmia Research and Therapeutics, Division of Clinical Pharmacology, Vanderbilt University Medical Center, Nashville, Tennessee, USA
| | - Bjӧrn C Knollmann
- Vanderbilt Center for Arrhythmia Research and Therapeutics, Division of Clinical Pharmacology, Vanderbilt University Medical Center, Nashville, Tennessee, USA
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