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Marinella G, Orsini A, Scacciati M, Costa E, Santangelo A, Astrea G, Frosini S, Pasquariello R, Rubegni A, Sgherri G, Corsi M, Bonuccelli A, Battini R. Congenital Myopathy as a Phenotypic Expression of CACNA1S Gene Mutation: Case Report and Systematic Review of the Literature. Genes (Basel) 2023; 14:1363. [PMID: 37510268 PMCID: PMC10379235 DOI: 10.3390/genes14071363] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2023] [Revised: 06/17/2023] [Accepted: 06/22/2023] [Indexed: 07/30/2023] Open
Abstract
BACKGROUND Congenital myopathies are a group of clinically, genetically, and histologically heterogeneous diseases caused by mutations in a large group of genes. One of these is CACNA1S, which is recognized as the cause of Dihydropyridine Receptor Congenital Myopathy. METHODS To better characterize the phenotypic spectrum of CACNA1S myopathy, we conducted a systematic review of cases in the literature through three electronic databases following the PRISMA guidelines. We selected nine articles describing 23 patients with heterozygous, homozygous, or compound heterozygous mutations in CACNA1S and we added one patient with a compound heterozygous mutation in CACNA1S (c.1394-2A>G; c.1724T>C, p.L575P) followed at our Institute. We collected clinical and genetic data, muscle biopsies, and muscle MRIs when available. RESULTS The phenotype of this myopathy is heterogeneous, ranging from more severe forms with a lethal early onset and mild-moderate forms with a better clinical course. CONCLUSIONS Our patient presented a phenotype compatible with the mild-moderate form, although she presented peculiar features such as a short stature, myopia, mild sensorineural hearing loss, psychiatric symptoms, and posterior-anterior impairment gradient on thigh muscle MRI.
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Affiliation(s)
- Gemma Marinella
- Department of Neuroscience, IRCCS Stella Maris Foundation, 56128 Pisa, Italy; (G.M.); (G.A.); (S.F.); (R.P.); (A.R.); (G.S.)
| | - Alessandro Orsini
- Pediatric Neurology, Pediatric University Department, Azienda Ospedaliera Universitaria Pisana, University of Pisa, 56100 Pisa, Italy; (A.O.); (M.S.); (A.S.); (A.B.)
| | - Massimo Scacciati
- Pediatric Neurology, Pediatric University Department, Azienda Ospedaliera Universitaria Pisana, University of Pisa, 56100 Pisa, Italy; (A.O.); (M.S.); (A.S.); (A.B.)
- Department of Clinical and Experimental Medicine, University of Pisa, 56126 Pisa, Italy
| | - Elisa Costa
- Pediatric Neurology, Pediatric University Department, Azienda Ospedaliera Universitaria Pisana, University of Pisa, 56100 Pisa, Italy; (A.O.); (M.S.); (A.S.); (A.B.)
- Department of Clinical and Experimental Medicine, University of Pisa, 56126 Pisa, Italy
| | - Andrea Santangelo
- Pediatric Neurology, Pediatric University Department, Azienda Ospedaliera Universitaria Pisana, University of Pisa, 56100 Pisa, Italy; (A.O.); (M.S.); (A.S.); (A.B.)
- Department of Clinical and Experimental Medicine, University of Pisa, 56126 Pisa, Italy
| | - Guja Astrea
- Department of Neuroscience, IRCCS Stella Maris Foundation, 56128 Pisa, Italy; (G.M.); (G.A.); (S.F.); (R.P.); (A.R.); (G.S.)
| | - Silvia Frosini
- Department of Neuroscience, IRCCS Stella Maris Foundation, 56128 Pisa, Italy; (G.M.); (G.A.); (S.F.); (R.P.); (A.R.); (G.S.)
| | - Rosa Pasquariello
- Department of Neuroscience, IRCCS Stella Maris Foundation, 56128 Pisa, Italy; (G.M.); (G.A.); (S.F.); (R.P.); (A.R.); (G.S.)
| | - Anna Rubegni
- Department of Neuroscience, IRCCS Stella Maris Foundation, 56128 Pisa, Italy; (G.M.); (G.A.); (S.F.); (R.P.); (A.R.); (G.S.)
| | - Giada Sgherri
- Department of Neuroscience, IRCCS Stella Maris Foundation, 56128 Pisa, Italy; (G.M.); (G.A.); (S.F.); (R.P.); (A.R.); (G.S.)
| | - Martina Corsi
- Department of Preventive and Occupational Medicine, Azienda Ospedaliera Universitaria Pisana, University of Pisa, 56126 Pisa, Italy;
| | - Alice Bonuccelli
- Pediatric Neurology, Pediatric University Department, Azienda Ospedaliera Universitaria Pisana, University of Pisa, 56100 Pisa, Italy; (A.O.); (M.S.); (A.S.); (A.B.)
| | - Roberta Battini
- Department of Neuroscience, IRCCS Stella Maris Foundation, 56128 Pisa, Italy; (G.M.); (G.A.); (S.F.); (R.P.); (A.R.); (G.S.)
- Department of Clinical and Experimental Medicine, University of Pisa, 56126 Pisa, Italy
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Campiglio M, Dyrda A, Tuinte WE, Török E. Ca V1.1 Calcium Channel Signaling Complexes in Excitation-Contraction Coupling: Insights from Channelopathies. Handb Exp Pharmacol 2023; 279:3-39. [PMID: 36592225 DOI: 10.1007/164_2022_627] [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] [Indexed: 01/03/2023]
Abstract
In skeletal muscle, excitation-contraction (EC) coupling relies on the mechanical coupling between two ion channels: the L-type voltage-gated calcium channel (CaV1.1), located in the sarcolemma and functioning as the voltage sensor of EC coupling, and the ryanodine receptor 1 (RyR1), located on the sarcoplasmic reticulum serving as the calcium release channel. To this day, the molecular mechanism by which these two ion channels are linked remains elusive. However, recently, skeletal muscle EC coupling could be reconstituted in heterologous cells, revealing that only four proteins are essential for this process: CaV1.1, RyR1, and the cytosolic proteins CaVβ1a and STAC3. Due to the crucial role of these proteins in skeletal muscle EC coupling, any mutation that affects any one of these proteins can have devastating consequences, resulting in congenital myopathies and other pathologies.Here, we summarize the current knowledge concerning these four essential proteins and discuss the pathophysiology of the CaV1.1, RyR1, and STAC3-related skeletal muscle diseases with an emphasis on the molecular mechanisms. Being part of the same signalosome, mutations in different proteins often result in congenital myopathies with similar symptoms or even in the same disease.
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Affiliation(s)
- Marta Campiglio
- Institute of Physiology, Medical University Innsbruck, Innsbruck, Austria.
| | - Agnieszka Dyrda
- Institute of Physiology, Medical University Innsbruck, Innsbruck, Austria
| | - Wietske E Tuinte
- Institute of Physiology, Medical University Innsbruck, Innsbruck, Austria
| | - Enikő Török
- Institute of Physiology, Medical University Innsbruck, Innsbruck, Austria
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3
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El Ghaleb Y, Ortner NJ, Posch W, Fernández-Quintero ML, Tuinte WE, Monteleone S, Draheim HJ, Liedl KR, Wilflingseder D, Striessnig J, Tuluc P, Flucher BE, Campiglio M. Calcium current modulation by the γ1 subunit depends on alternative splicing of CaV1.1. J Gen Physiol 2022; 154:e202113028. [PMID: 35349630 PMCID: PMC9037348 DOI: 10.1085/jgp.202113028] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2021] [Accepted: 03/08/2022] [Indexed: 01/01/2023] Open
Abstract
The skeletal muscle voltage-gated calcium channel (CaV1.1) primarily functions as a voltage sensor for excitation-contraction coupling. Conversely, its ion-conducting function is modulated by multiple mechanisms within the pore-forming α1S subunit and the auxiliary α2δ-1 and γ1 subunits. In particular, developmentally regulated alternative splicing of exon 29, which inserts 19 amino acids in the extracellular IVS3-S4 loop of CaV1.1a, greatly reduces the current density and shifts the voltage dependence of activation to positive potentials outside the physiological range. We generated new HEK293 cell lines stably expressing α2δ-1, β3, and STAC3. When the adult (CaV1.1a) and embryonic (CaV1.1e) splice variants were expressed in these cells, the difference in the voltage dependence of activation observed in muscle cells was reproduced, but not the reduced current density of CaV1.1a. Only when we further coexpressed the γ1 subunit was the current density of CaV1.1a, but not that of CaV1.1e, reduced by >50%. In addition, γ1 caused a shift of the voltage dependence of inactivation to negative voltages in both variants. Thus, the current-reducing effect of γ1, unlike its effect on inactivation, is specifically dependent on the inclusion of exon 29 in CaV1.1a. Molecular structure modeling revealed several direct ionic interactions between residues in the IVS3-S4 loop and the γ1 subunit. However, substitution of these residues by alanine, individually or in combination, did not abolish the γ1-dependent reduction of current density, suggesting that structural rearrangements in CaV1.1a induced by inclusion of exon 29 may allosterically empower the γ1 subunit to exert its inhibitory action on CaV1.1 calcium currents.
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Affiliation(s)
- Yousra El Ghaleb
- Institute of Physiology, Department of Physiology and Medical Physics, Medical University Innsbruck, Innsbruck, Austria
| | - Nadine J. Ortner
- Department of Pharmacology and Toxicology, Center for Molecular Biosciences Innsbruck, University of Innsbruck, Innsbruck, Austria
| | - Wilfried Posch
- Institute of Hygiene and Medical Microbiology, Medical University of Innsbruck, Innsbruck, Austria
| | | | - Wietske E. Tuinte
- Institute of Physiology, Department of Physiology and Medical Physics, Medical University Innsbruck, Innsbruck, Austria
| | - Stefania Monteleone
- Institute of General, Inorganic and Theoretical Chemistry, University of Innsbruck, Innsbruck, Austria
| | - Henning J. Draheim
- Boehringer Ingelheim Pharma GmbH & Co KG, CNS Research, Biberach an der Riss, Germany
| | - Klaus R. Liedl
- Institute of General, Inorganic and Theoretical Chemistry, University of Innsbruck, Innsbruck, Austria
| | - Doris Wilflingseder
- Institute of Hygiene and Medical Microbiology, Medical University of Innsbruck, Innsbruck, Austria
| | - Jörg Striessnig
- Department of Pharmacology and Toxicology, Center for Molecular Biosciences Innsbruck, University of Innsbruck, Innsbruck, Austria
| | - Petronel Tuluc
- Department of Pharmacology and Toxicology, Center for Molecular Biosciences Innsbruck, University of Innsbruck, Innsbruck, Austria
| | - Bernhard E. Flucher
- Institute of Physiology, Department of Physiology and Medical Physics, Medical University Innsbruck, Innsbruck, Austria
| | - Marta Campiglio
- Institute of Physiology, Department of Physiology and Medical Physics, Medical University Innsbruck, Innsbruck, Austria
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Shishmarev D, Rowland E, Aditya S, Sundararaj S, Oakley AJ, Dulhunty AF, Casarotto MG. Molecular interactions of
STAC
proteins with skeletal muscle dihydropyridine receptor and excitation‐contraction coupling. Protein Sci 2022; 31:e4311. [PMID: 35481653 PMCID: PMC9019556 DOI: 10.1002/pro.4311] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2021] [Revised: 03/20/2022] [Accepted: 04/01/2022] [Indexed: 01/06/2023]
Abstract
Excitation‐contraction coupling (ECC) is the physiological process in which an electrical signal originating from the central nervous system is converted into muscle contraction. In skeletal muscle tissue, the key step in the molecular mechanism of ECC initiated by the muscle action potential is the cooperation between two Ca2+ channels, dihydropyridine receptor (DHPR; voltage‐dependent L‐type calcium channel) and ryanodine receptor 1 (RyR1). These two channels were originally postulated to communicate with each other via direct mechanical interactions; however, the molecular details of this cooperation have remained ambiguous. Recently, it has been proposed that one or more supporting proteins are in fact required for communication of DHPR with RyR1 during the ECC process. One such protein that is increasingly believed to play a role in this interaction is the SH3 and cysteine‐rich domain‐containing protein 3 (STAC3), which has been proposed to bind a cytosolic portion of the DHPR α1S subunit known as the II–III loop. In this work, we present direct evidence for an interaction between a small peptide sequence of the II–III loop and several residues within the SH3 domains of STAC3 as well as the neuronal isoform STAC2. Differences in this interaction between STAC3 and STAC2 suggest that STAC3 possesses distinct biophysical features that are potentially important for its physiological interactions with the II–III loop. Therefore, this work demonstrates an isoform‐specific interaction between STAC3 and the II–III loop of DHPR and provides novel insights into a putative molecular mechanism behind this association in the skeletal muscle ECC process.
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Affiliation(s)
- Dmitry Shishmarev
- John Curtin School of Medical Research Australian National University Canberra Australia
- Research School of Biology Australian National University Canberra Australia
| | - Emily Rowland
- John Curtin School of Medical Research Australian National University Canberra Australia
- Division of Structural Biology, Wellcome Centre for Human Genetics University of Oxford Oxford UK
| | - Shouvik Aditya
- John Curtin School of Medical Research Australian National University Canberra Australia
- Research School of Biology Australian National University Canberra Australia
| | - Srinivasan Sundararaj
- John Curtin School of Medical Research Australian National University Canberra Australia
| | - Aaron J. Oakley
- School of Chemistry & Molecular Bioscience and Molecular Horizons University of Wollongong Wollongong Australia
| | - Angela F. Dulhunty
- John Curtin School of Medical Research Australian National University Canberra Australia
| | - Marco G. Casarotto
- Research School of Biology Australian National University Canberra Australia
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5
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Sahu G, Turner RW. The Molecular Basis for the Calcium-Dependent Slow Afterhyperpolarization in CA1 Hippocampal Pyramidal Neurons. Front Physiol 2022; 12:759707. [PMID: 35002757 PMCID: PMC8730529 DOI: 10.3389/fphys.2021.759707] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2021] [Accepted: 11/01/2021] [Indexed: 12/02/2022] Open
Abstract
Neuronal signal transmission depends on the frequency, pattern, and timing of spike output, each of which are shaped by spike afterhyperpolarizations (AHPs). There are classically three post-spike AHPs of increasing duration categorized as fast, medium and slow AHPs that hyperpolarize a cell over a range of 10 ms to 30 s. Intensive early work on CA1 hippocampal pyramidal cells revealed that all three AHPs incorporate activation of calcium-gated potassium channels. The ionic basis for a fAHP was rapidly attributed to the actions of big conductance (BK) and the mAHP to small conductance (SK) or Kv7 potassium channels. In stark contrast, the ionic basis for a prominent slow AHP of up to 30 s duration remained an enigma for over 30 years. Recent advances in pharmacological, molecular, and imaging tools have uncovered the expression of a calcium-gated intermediate conductance potassium channel (IK, KCa3.1) in central neurons that proves to contribute to the slow AHP in CA1 hippocampal pyramidal cells. Together the data show that the sAHP arises in part from a core tripartite complex between Cav1.3 (L-type) calcium channels, ryanodine receptors, and IK channels at endoplasmic reticulum-plasma membrane junctions. Work on the sAHP in CA1 pyramidal neurons has again quickened pace, with identified contributions by both IK channels and the Na-K pump providing answers to several mysteries in the pharmacological properties of the sAHP.
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Affiliation(s)
- Giriraj Sahu
- National Institute of Pharmaceutical Education and Research Ahmedabad, Ahmedabad, India
| | - Ray W Turner
- Department Cell Biology & Anatomy, Cumming School of Medicine, Hotchkiss Brain Institute, University of Calgary, Calgary, AB, Canada
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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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7
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Rufenach B, Van Petegem F. Structure and function of STAC proteins: Calcium channel modulators and critical components of muscle excitation-contraction coupling. J Biol Chem 2021; 297:100874. [PMID: 34129875 PMCID: PMC8258685 DOI: 10.1016/j.jbc.2021.100874] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2020] [Revised: 06/02/2021] [Accepted: 06/11/2021] [Indexed: 12/26/2022] Open
Abstract
In skeletal muscle tissue, an intriguing mechanical coupling exists between two ion channels from different membranes: the L-type voltage-gated calcium channel (CaV1.1), located in the plasma membrane, and ryanodine receptor 1 (RyR1) located in the sarcoplasmic reticulum membrane. Excitable cells rely on Cavs to initiate Ca2+ entry in response to action potentials. RyRs can amplify this signal by releasing Ca2+ from internal stores. Although this process can be mediated through Ca2+ as a messenger, an overwhelming amount of evidence suggests that RyR1 has recruited CaV1.1 directly as its voltage sensor. The exact mechanisms that underlie this coupling have been enigmatic, but a recent wave of reports have illuminated the coupling protein STAC3 as a critical player. Without STAC3, the mechanical coupling between Cav1.1 and RyR1 is lost, and muscles fail to contract. Various sequence variants of this protein have been linked to congenital myopathy. Other STAC isoforms are expressed in the brain and may serve as regulators of L-type CaVs. Despite the short length of STACs, several points of contacts have been proposed between them and CaVs. However, it is currently unclear whether STAC3 also forms direct interactions with RyR1, and whether this modulates RyR1 function. In this review, we discuss the 3D architecture of STAC proteins, the biochemical evidence for their interactions, the relevance of these connections for functional modulation, and their involvement in myopathy.
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Affiliation(s)
- Britany Rufenach
- Department of Biochemistry and Molecular Biology, Life Sciences Institute, University of British Columbia, Vancouver, Canada
| | - Filip Van Petegem
- Department of Biochemistry and Molecular Biology, Life Sciences Institute, University of British Columbia, Vancouver, Canada.
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8
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Protasi F, Pietrangelo L, Boncompagni S. Improper Remodeling of Organelles Deputed to Ca 2+ Handling and Aerobic ATP Production Underlies Muscle Dysfunction in Ageing. Int J Mol Sci 2021; 22:6195. [PMID: 34201319 PMCID: PMC8228829 DOI: 10.3390/ijms22126195] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2021] [Revised: 06/01/2021] [Accepted: 06/02/2021] [Indexed: 12/28/2022] Open
Abstract
Proper skeletal muscle function is controlled by intracellular Ca2+ concentration and by efficient production of energy (ATP), which, in turn, depend on: (a) the release and re-uptake of Ca2+ from sarcoplasmic-reticulum (SR) during excitation-contraction (EC) coupling, which controls the contraction and relaxation of sarcomeres; (b) the uptake of Ca2+ into the mitochondrial matrix, which stimulates aerobic ATP production; and finally (c) the entry of Ca2+ from the extracellular space via store-operated Ca2+ entry (SOCE), a mechanism that is important to limit/delay muscle fatigue. Abnormalities in Ca2+ handling underlie many physio-pathological conditions, including dysfunction in ageing. The specific focus of this review is to discuss the importance of the proper architecture of organelles and membrane systems involved in the mechanisms introduced above for the correct skeletal muscle function. We reviewed the existing literature about EC coupling, mitochondrial Ca2+ uptake, SOCE and about the structural membranes and organelles deputed to those functions and finally, we summarized the data collected in different, but complementary, projects studying changes caused by denervation and ageing to the structure and positioning of those organelles: a. denervation of muscle fibers-an event that contributes, to some degree, to muscle loss in ageing (known as sarcopenia)-causes misplacement and damage: (i) of membrane structures involved in EC coupling (calcium release units, CRUs) and (ii) of the mitochondrial network; b. sedentary ageing causes partial disarray/damage of CRUs and of calcium entry units (CEUs, structures involved in SOCE) and loss/misplacement of mitochondria; c. functional electrical stimulation (FES) and regular exercise promote the rescue/maintenance of the proper architecture of CRUs, CEUs, and of mitochondria in both denervation and ageing. All these structural changes were accompanied by related functional changes, i.e., loss/decay in function caused by denervation and ageing, and improved function following FES or exercise. These data suggest that the integrity and proper disposition of intracellular organelles deputed to Ca2+ handling and aerobic generation of ATP is challenged by inactivity (or reduced activity); modifications in the architecture of these intracellular membrane systems may contribute to muscle dysfunction in ageing and sarcopenia.
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Affiliation(s)
- Feliciano Protasi
- CAST, Center for Advanced Studies and Technology, University G. d’Annunzio of Chieti-Pescara, I-66100 Chieti, Italy; (L.P.); (S.B.)
- DMSI, Department of Medicine and Aging Sciences, University G. d’Annunzio of Chieti-Pescara, I-66100 Chieti, Italy
| | - Laura Pietrangelo
- CAST, Center for Advanced Studies and Technology, University G. d’Annunzio of Chieti-Pescara, I-66100 Chieti, Italy; (L.P.); (S.B.)
- DMSI, Department of Medicine and Aging Sciences, University G. d’Annunzio of Chieti-Pescara, I-66100 Chieti, Italy
| | - Simona Boncompagni
- CAST, Center for Advanced Studies and Technology, University G. d’Annunzio of Chieti-Pescara, I-66100 Chieti, Italy; (L.P.); (S.B.)
- DNICS, Department of Neuroscience and Clinical Sciences, University G. d’Annunzio of Chieti-Pescara, I-66100 Chieti, Italy
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Abstract
Neuropeptides are important for regulating numerous neural functions and behaviors. Release of neuropeptides requires long-lasting, high levels of cytosolic Ca2+ However, the molecular regulation of neuropeptide release remains to be clarified. Recently, Stac3 was identified as a key regulator of L-type Ca2+ channels (CaChs) and excitation-contraction coupling in vertebrate skeletal muscles. There is a small family of stac genes in vertebrates with other members expressed by subsets of neurons in the central nervous system. The function of neural Stac proteins, however, is poorly understood. Drosophila melanogaster contain a single stac gene, Dstac, which is expressed by muscles and a subset of neurons, including neuropeptide-expressing motor neurons. Here, genetic manipulations, coupled with immunolabeling, Ca2+ imaging, electrophysiology, and behavioral analysis, revealed that Dstac regulates L-type CaChs (Dmca1D) in Drosophila motor neurons and this, in turn, controls the release of neuropeptides.
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10
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Rufenach B, Christy D, Flucher BE, Bui JM, Gsponer J, Campiglio M, Van Petegem F. Multiple Sequence Variants in STAC3 Affect Interactions with CaV1.1 and Excitation-Contraction Coupling. Structure 2020; 28:922-932.e5. [DOI: 10.1016/j.str.2020.05.005] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2019] [Revised: 04/03/2020] [Accepted: 05/11/2020] [Indexed: 10/24/2022]
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Huerlimann R, Maes GE, Maxwell MJ, Mobli M, Launikonis BS, Jerry DR, Wade NM. Multi-species transcriptomics reveals evolutionary diversity in the mechanisms regulating shrimp tail muscle excitation-contraction coupling. Gene 2020; 752:144765. [PMID: 32413480 DOI: 10.1016/j.gene.2020.144765] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2020] [Revised: 04/17/2020] [Accepted: 05/11/2020] [Indexed: 11/30/2022]
Abstract
The natural flight response in shrimp is powered by rapid contractions of the abdominal muscle fibres to propel themselves backwards away from perceived danger. This muscle contraction is dependent on repetitive depolarization of muscle plasma membrane, triggering tightly spaced cytoplasmic [Ca2+] transients and rapidly rising tetanic force responses. To achieve such high amplitude and high frequency of Ca2+ transients requires a high abundance of sarcoplasmic/endoplasmic reticulum Ca2+ ATPase (SERCA) to rapidly clear cytoplasmic Ca2+ between each transient and an efficient Ca2+ release system consisting of the Ryanodine Receptor (RyR), and voltage gated Ca2+ channels (CaVs). With the aim to expand our knowledge of muscle gene function and identify orthologous genes regulating muscle excitation-contraction (EC) coupling, this study assembled nine Penaeid shrimp muscle transcriptomes. On average, the nine transcriptomes contained 27,000 contigs, with an annotation rate of 36% and a BUSCO completeness of 70%. Despite maintaining their function, the crustacean RyR and CaV proteins showed evidence of significant diversification from mammalian orthologs, while SERCA remained more conserved. Several key components of protein interaction were conserved, while others showed distinct crustacean specific evolutionary adaptations. Lastly, this study revealed approximately 1,000 orthologous genes involved in muscle specific processes present across all nine species.
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Affiliation(s)
- Roger Huerlimann
- ARC Research Hub for Advanced Prawn Breeding, Australia; Centre for Sustainable Tropical Fisheries and Aquaculture, College of Science and Engineering, James Cook University, Townsville, QLD 4811, Australia; Centre for Tropical Bioinformatics and Molecular Biology, James Cook University, Townsville, QLD 4811, Australia.
| | - Gregory E Maes
- Centre for Sustainable Tropical Fisheries and Aquaculture, College of Science and Engineering, James Cook University, Townsville, QLD 4811, Australia; Laboratory of Biodiversity and Evolutionary Genomics, KU Leuven, Leuven 3000, Belgium; Centre for Human Genetics, KU Leuven, Leuven 3000, Belgium
| | - Michael J Maxwell
- Centre for Advanced Imaging, University of Queensland, Brisbane, QLD 4072, Australia
| | - Mehdi Mobli
- Centre for Advanced Imaging, University of Queensland, Brisbane, QLD 4072, Australia
| | - Bradley S Launikonis
- School of Biomedical Sciences, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Dean R Jerry
- ARC Research Hub for Advanced Prawn Breeding, Australia; Centre for Sustainable Tropical Fisheries and Aquaculture, College of Science and Engineering, James Cook University, Townsville, QLD 4811, Australia; Tropical Futures Institute, James Cook University, 149 Sims Drive, Singapore 387380, Singapore
| | - Nicholas M Wade
- ARC Research Hub for Advanced Prawn Breeding, Australia; CSIRO Agriculture and Food, Aquaculture Program, 306 Carmody Road, St Lucia, QLD 4067
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12
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Flucher BE. Skeletal muscle Ca V1.1 channelopathies. Pflugers Arch 2020; 472:739-754. [PMID: 32222817 PMCID: PMC7351834 DOI: 10.1007/s00424-020-02368-3] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2020] [Revised: 03/06/2020] [Accepted: 03/17/2020] [Indexed: 12/15/2022]
Abstract
CaV1.1 is specifically expressed in skeletal muscle where it functions as voltage sensor of skeletal muscle excitation-contraction (EC) coupling independently of its functions as L-type calcium channel. Consequently, all known CaV1.1-related diseases are muscle diseases and the molecular and cellular disease mechanisms relate to the dual functions of CaV1.1 in this tissue. To date, four types of muscle diseases are known that can be linked to mutations in the CACNA1S gene or to splicing defects. These are hypo- and normokalemic periodic paralysis, malignant hyperthermia susceptibility, CaV1.1-related myopathies, and myotonic dystrophy type 1. In addition, the CaV1.1 function in EC coupling is perturbed in Native American myopathy, arising from mutations in the CaV1.1-associated protein STAC3. Here, we first address general considerations concerning the possible roles of CaV1.1 in disease and then discuss the state of the art regarding the pathophysiology of the CaV1.1-related skeletal muscle diseases with an emphasis on molecular disease mechanisms.
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Affiliation(s)
- Bernhard E Flucher
- Department of Physiology and Medical Biophysics, Medical University Innsbruck, Schöpfstraße 41, A6020, Innsbruck, Austria.
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13
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Ogawa H, Kurebayashi N, Yamazawa T, Murayama T. Regulatory mechanisms of ryanodine receptor/Ca 2+ release channel revealed by recent advancements in structural studies. J Muscle Res Cell Motil 2020; 42:291-304. [PMID: 32040690 PMCID: PMC8332584 DOI: 10.1007/s10974-020-09575-6] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2019] [Accepted: 02/05/2020] [Indexed: 02/07/2023]
Abstract
Ryanodine receptors (RyRs) are huge homotetrameric Ca2+ release channels localized to the sarcoplasmic reticulum. RyRs are responsible for the release of Ca2+ from the SR during excitation–contraction coupling in striated muscle cells. Recent revolutionary advancements in cryo-electron microscopy have provided a number of near-atomic structures of RyRs, which have enabled us to better understand the architecture of RyRs. Thus, we are now in a new era understanding the gating, regulatory and disease-causing mechanisms of RyRs. Here we review recent advances in the elucidation of the structures of RyRs, especially RyR1 in skeletal muscle, and their mechanisms of regulation by small molecules, associated proteins and disease-causing mutations.
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Affiliation(s)
- Haruo Ogawa
- Institute for Quantitative Biosciences, The University of Tokyo, Tokyo, 113-0032, Japan.
| | - Nagomi Kurebayashi
- Department of Pharmacology, Juntendo University School of Medicine, Tokyo, 113-8421, Japan
| | - Toshiko Yamazawa
- Department of Molecular Physiology, The Jikei University School of Medicine, Tokyo, 105-8461, Japan
| | - Takashi Murayama
- Department of Pharmacology, Juntendo University School of Medicine, Tokyo, 113-8421, Japan
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14
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Shishmarev D. Excitation-contraction coupling in skeletal muscle: recent progress and unanswered questions. Biophys Rev 2020; 12:143-153. [PMID: 31950344 DOI: 10.1007/s12551-020-00610-x] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2019] [Accepted: 01/03/2020] [Indexed: 02/07/2023] Open
Abstract
Excitation-contraction coupling (ECC) is a physiological process that links excitation of muscles by the nervous system to their mechanical contraction. In skeletal muscle, ECC is initiated with an action potential, generated by the somatic nervous system, which causes a depolarisation of the muscle fibre membrane (sarcolemma). This leads to a rapid change in the transmembrane potential, which is detected by the voltage-gated Ca2+ channel dihydropyridine receptor (DHPR) embedded in the sarcolemma. DHPR transmits the contractile signal to another Ca2+ channel, ryanodine receptor (RyR1), embedded in the membrane of the sarcoplasmic reticulum (SR), which releases a large amount of Ca2+ ions from the SR that initiate muscle contraction. Despite the fundamental role of ECC in skeletal muscle function of all vertebrate species, the molecular mechanism underpinning the communication between the two key proteins involved in the process (DHPR and RyR1) is still largely unknown. The goal of this work is to review the recent progress in our understanding of ECC in skeletal muscle from the point of view of the structure and interactions of proteins involved in the process, and to highlight the unanswered questions in the field.
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Affiliation(s)
- Dmitry Shishmarev
- John Curtin School of Medical Research, The Australian National University, Canberra, ACT, 2601, Australia.
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15
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Ca 2+ Channels Mediate Bidirectional Signaling between Sarcolemma and Sarcoplasmic Reticulum in Muscle Cells. Cells 2019; 9:cells9010055. [PMID: 31878335 PMCID: PMC7016941 DOI: 10.3390/cells9010055] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2019] [Revised: 12/19/2019] [Accepted: 12/23/2019] [Indexed: 12/21/2022] Open
Abstract
The skeletal muscle and myocardial cells present highly specialized structures; for example, the close interaction between the sarcoplasmic reticulum (SR) and mitochondria—responsible for excitation-metabolism coupling—and the junction that connects the SR with T-tubules, critical for excitation-contraction (EC) coupling. The mechanisms that underlie EC coupling in these two cell types, however, are fundamentally distinct. They involve the differential expression of Ca2+ channel subtypes: CaV1.1 and RyR1 (skeletal), vs. CaV1.2 and RyR2 (cardiac). The CaV channels transform action potentials into elevations of cytosolic Ca2+, by activating RyRs and thus promoting SR Ca2+ release. The high levels of Ca2+, in turn, stimulate not only the contractile machinery but also the generation of mitochondrial reactive oxygen species (ROS). This forward signaling is reciprocally regulated by the following feedback mechanisms: Ca2+-dependent inactivation (of Ca2+ channels), the recruitment of Na+/Ca2+ exchanger activity, and oxidative changes in ion channels and transporters. Here, we summarize both well-established concepts and recent advances that have contributed to a better understanding of the molecular mechanisms involved in this bidirectional signaling.
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16
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17
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Ca 2+-independent but voltage-dependent quantal catecholamine secretion (CiVDS) in the mammalian sympathetic nervous system. Proc Natl Acad Sci U S A 2019; 116:20201-20209. [PMID: 31530723 DOI: 10.1073/pnas.1902444116] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Action potential-induced vesicular exocytosis is considered exclusively Ca2+ dependent in Katz's Ca2+ hypothesis on synaptic transmission. This long-standing concept gets an exception following the discovery of Ca2+-independent but voltage-dependent secretion (CiVDS) and its molecular mechanisms in dorsal root ganglion sensory neurons. However, whether CiVDS presents only in sensory cells remains elusive. Here, by combining multiple independent recordings, we report that [1] CiVDS robustly presents in the sympathetic nervous system, including sympathetic superior cervical ganglion neurons and slice adrenal chromaffin cells, [2] uses voltage sensors of Ca2+ channels (N-type and novel L-type), and [3] contributes to catecholamine release in both homeostatic and fight-or-flight like states; [4] CiVDS-mediated catecholamine release is faster than that of Ca2+-dependent secretion at the quantal level and [5] increases Ca2+ currents and contractility of cardiac myocytes. Together, CiVDS presents in the sympathetic nervous system with potential physiological functions, including cardiac muscle contractility.
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18
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Flucher BE, Campiglio M. STAC proteins: The missing link in skeletal muscle EC coupling and new regulators of calcium channel function. BIOCHIMICA ET BIOPHYSICA ACTA. MOLECULAR CELL RESEARCH 2019; 1866:1101-1110. [PMID: 30543836 DOI: 10.1016/j.bbamcr.2018.12.004] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/22/2018] [Revised: 12/04/2018] [Accepted: 12/05/2018] [Indexed: 01/19/2023]
Abstract
Excitation-contraction coupling is the signaling process by which action potentials control calcium release and consequently the force of muscle contraction. Until recently, three triad proteins were known to be essential for skeletal muscle EC coupling: the voltage-gated calcium channel CaV1.1 acting as voltage sensor, the SR calcium release channel RyR1 representing the only relevant calcium source, and the auxiliary CaV β1a subunit. Whether CaV1.1 and RyR1 are directly coupled or whether their interaction is mediated by another triad protein is still unknown. The recent identification of the adaptor protein STAC3 as fourth essential component of skeletal muscle EC coupling prompted vigorous research to reveal its role in this signaling process. Accumulating evidence supports its possible involvement in linking CaV1.1 and RyR1 in skeletal muscle EC coupling, but also indicates a second, much broader role of STAC proteins in the regulation of calcium/calmodulin-dependent feedback regulation of L-type calcium channels.
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Affiliation(s)
- Bernhard E Flucher
- Department of Physiology and Medical Physics, Medical University Innsbruck, Schöpfstraße 41, A6020 Innsbruck, Austria.
| | - Marta Campiglio
- Department of Physiology and Medical Physics, Medical University Innsbruck, Schöpfstraße 41, A6020 Innsbruck, Austria
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19
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Zaharieva IT, Sarkozy A, Munot P, Manzur A, O'Grady G, Rendu J, Malfatti E, Amthor H, Servais L, Urtizberea JA, Neto OA, Zanoteli E, Donkervoort S, Taylor J, Dixon J, Poke G, Foley AR, Holmes C, Williams G, Holder M, Yum S, Medne L, Quijano-Roy S, Romero NB, Fauré J, Feng L, Bastaki L, Davis MR, Phadke R, Sewry CA, Bönnemann CG, Jungbluth H, Bachmann C, Treves S, Muntoni F. STAC3 variants cause a congenital myopathy with distinctive dysmorphic features and malignant hyperthermia susceptibility. Hum Mutat 2018; 39:1980-1994. [PMID: 30168660 DOI: 10.1002/humu.23635] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2018] [Revised: 07/27/2018] [Accepted: 08/28/2018] [Indexed: 12/14/2022]
Abstract
SH3 and cysteine-rich domain-containing protein 3 (STAC3) is an essential component of the skeletal muscle excitation-contraction coupling (ECC) machinery, though its role and function are not yet completely understood. Here, we report 18 patients carrying a homozygous p.(Trp284Ser) STAC3 variant in addition to a patient compound heterozygous for the p.(Trp284Ser) and a novel splice site change (c.997-1G > T). Clinical severity ranged from prenatal onset with severe features at birth, to a milder and slowly progressive congenital myopathy phenotype. A malignant hyperthermia (MH)-like reaction had occurred in several patients. The functional analysis demonstrated impaired ECC. In particular, KCl-induced membrane depolarization resulted in significantly reduced sarcoplasmic reticulum Ca2+ release. Co-immunoprecipitation of STAC3 with CaV 1.1 in patients and control muscle samples showed that the protein interaction between STAC3 and CaV 1.1 was not significantly affected by the STAC3 variants. This study demonstrates that STAC3 gene analysis should be included in the diagnostic work up of patients of any ethnicity presenting with congenital myopathy, in particular if a history of MH-like episodes is reported. While the precise pathomechanism remains to be elucidated, our functional characterization of STAC3 variants revealed that defective ECC is not a result of CaV 1.1 sarcolemma mislocalization or impaired STAC3-CaV 1.1 interaction.
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Affiliation(s)
- Irina T Zaharieva
- Dubowitz Neuromuscular Centre, UCL Great Ormond Street Institute of Child Health, London, UK
| | - Anna Sarkozy
- Dubowitz Neuromuscular Centre, UCL Great Ormond Street Institute of Child Health, London, UK.,Great Ormond Street Hospital, London, UK
| | - Pinki Munot
- Dubowitz Neuromuscular Centre, UCL Great Ormond Street Institute of Child Health, London, UK.,Great Ormond Street Hospital, London, UK
| | - Adnan Manzur
- Dubowitz Neuromuscular Centre, UCL Great Ormond Street Institute of Child Health, London, UK.,Great Ormond Street Hospital, London, UK
| | - Gina O'Grady
- Institute of Neuroscience and Muscle Research, Children's Hospital at Westmead, Sydney, New South Wales, Australia.,Discipline of Paediatrics and Child Health Clinical School, University of Sydney, Sydney, New South Wales, Australia
| | - John Rendu
- UFR de Médecine, Centre Hospitalier Universitaire Grenoble Alpes, Université Grenoble Alpes, Grenoble, France
| | - Eduardo Malfatti
- Neuromuscular Morphology Unit and Neuromuscular Pathology Reference Center Paris-Est, Center for Research in Myology, Groupe Hospitalier Universitaire La Pitié-Salpêtrière, Paris, France
| | - Helge Amthor
- UFR des sciences de la santé, Versailles Saint-Quentin-en-Yvelines University, Montigny-le-Bretonneux, France.,Service de Pédiatrie, Centre Hospitalier Universitaire Raymond Poincaré, Garches, France
| | | | - J Andoni Urtizberea
- Centre de Compétence Neuromusculaire, FILNEMUS, Hôpital Marin, Hendaye, France
| | - Osorio Abath Neto
- Departamento de Neurologia, Faculdade de Medicina da Universidade de São Paulo (FMUSP), São Paulo, Brazil.,Neuromuscular and Neurogenetic Disorders of Childhood Section, National Institutes of Health, Bethesda, Maryland, USA
| | - Edmar Zanoteli
- Departamento de Neurologia, Faculdade de Medicina da Universidade de São Paulo (FMUSP), São Paulo, Brazil
| | - Sandra Donkervoort
- Neuromuscular and Neurogenetic Disorders of Childhood Section, National Institutes of Health, Bethesda, Maryland, USA
| | - Juliet Taylor
- Genetic Health Service New Zealand, Auckland, New Zealand
| | - Joanne Dixon
- Genetic Health Service New Zealand, Christchurch, New Zealand
| | - Gemma Poke
- Genetic Health Service New Zealand, Wellington, New Zealand
| | - A Reghan Foley
- Neuromuscular and Neurogenetic Disorders of Childhood Section, National Institutes of Health, Bethesda, Maryland, USA
| | | | | | - Muriel Holder
- Department of Clinical Genetics, Guy's Hospital, London, UK
| | - Sabrina Yum
- Division of Neurology, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania
| | - Livija Medne
- Division of Human Genetics, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania
| | - Susana Quijano-Roy
- Service de Pédiatrie, Centre Hospitalier Universitaire Raymond Poincaré, Garches, France.,Centre de Référence Neuromusculaire GNMH, FILNEMUS, Université de Versailles, Versailles, France
| | - Norma B Romero
- Neuromuscular Morphology Unit and Neuromuscular Pathology Reference Center Paris-Est, Center for Research in Myology, Groupe Hospitalier Universitaire La Pitié-Salpêtrière, Paris, France
| | - Julien Fauré
- UFR de Médecine, Centre Hospitalier Universitaire Grenoble Alpes, Université Grenoble Alpes, Grenoble, France
| | - Lucy Feng
- Dubowitz Neuromuscular Centre, UCL Great Ormond Street Institute of Child Health, London, UK
| | - Laila Bastaki
- Kuwait Medical Genetics Centre, Maternity Hospital, Kuwait City, Kuwait
| | - Mark R Davis
- Department of Diagnostic Genomics, Pathwest Laboratory Medicine, QEII Medical Centre, Nedlands, Western Australia, Australia
| | - Rahul Phadke
- Dubowitz Neuromuscular Centre, UCL Great Ormond Street Institute of Child Health, London, UK.,Great Ormond Street Hospital, London, UK
| | - Caroline A Sewry
- Dubowitz Neuromuscular Centre, UCL Great Ormond Street Institute of Child Health, London, UK.,Wolfson Centre for Inherited Neuromuscular Diseases, RJAH Orthopaedic Hospital, Oswestry, UK
| | - Carsten G Bönnemann
- Neuromuscular and Neurogenetic Disorders of Childhood Section, National Institutes of Health, Bethesda, Maryland, USA
| | - Heinz Jungbluth
- Randall Division for Cell and Molecular Biophysics, Muscle Signaling Section, King's College London, London, UK.,Department of Basic and Clinical Neuroscience, IoPPN, King's College London, London, UK.,Department of Anesthesia and Biomedicine, University Hospital Basel, Basel, Switzerland
| | - Christoph Bachmann
- Department of Anesthesia and Biomedicine, University Hospital Basel, Basel, Switzerland
| | - Susan Treves
- Department of Anesthesia and Biomedicine, University Hospital Basel, Basel, Switzerland.,Department of Life Sciences, University of Ferrara, Ferrara, Italy
| | - Francesco Muntoni
- Dubowitz Neuromuscular Centre, UCL Great Ormond Street Institute of Child Health, London, UK.,Great Ormond Street Hospital, London, UK.,NIHR Great Ormond Street Hospital Biomedical Research Centre, London, UK
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20
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Abstract
Our textbook image of organelles has changed. Instead of revealing isolated cellular compartments, the picture now emerging shows organelles as largely interdependent structures that can communicate through membrane contact sites (MCSs). MCSs are sites where opposing organelles are tethered but do not fuse. MCSs provide a hybrid location where the tool kits of two different organelles can work together to perform vital cellular functions, such as lipid and ion transfer, signaling, and organelle division. Here, we focus on MCSs involving the endoplasmic reticulum (ER), an organelle forming an extensive network of cisternae and tubules. We highlight how the dynamic ER network regulates a plethora of cellular processes through MCSs with various organelles and with the plasma membrane.
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Affiliation(s)
- Haoxi Wu
- Department of Molecular, Cellular and Developmental Biology, University of Colorado, Boulder, CO 80309, USA
| | - Pedro Carvalho
- Sir William Dunn School of Pathology, University of Oxford, Oxford, England, UK.
| | - Gia K Voeltz
- Department of Molecular, Cellular and Developmental Biology, University of Colorado, Boulder, CO 80309, USA.
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21
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Polster A, Nelson BR, Papadopoulos S, Olson EN, Beam KG. Stac proteins associate with the critical domain for excitation-contraction coupling in the II-III loop of Ca V1.1. J Gen Physiol 2018; 150:613-624. [PMID: 29467163 PMCID: PMC5881444 DOI: 10.1085/jgp.201711917] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2017] [Revised: 01/05/2018] [Accepted: 01/17/2018] [Indexed: 12/11/2022] Open
Abstract
In skeletal muscle, residues 720-764/5 within the CaV1.1 II-III loop form a critical domain that plays an essential role in transmitting the excitation-contraction (EC) coupling Ca2+ release signal to the type 1 ryanodine receptor (RyR1) in the sarcoplasmic reticulum. However, the identities of proteins that interact with the loop and its critical domain and the mechanism by which the II-III loop regulates RyR1 gating remain unknown. Recent work has shown that EC coupling in skeletal muscle of fish and mice depends on the presence of Stac3, an adaptor protein that is highly expressed only in skeletal muscle. Here, by using colocalization as an indicator of molecular interactions, we show that Stac3, as well as Stac1 and Stac2 (predominantly neuronal Stac isoforms), interact with the II-III loop of CaV1.1. Further, we find that these Stac proteins promote the functional expression of CaV1.1 in tsA201 cells and support EC coupling in Stac3-null myotubes and that Stac3 is the most effective. Coexpression in tsA201 cells reveals that Stac3 interacts only with II-III loop constructs containing the majority of the CaV1.1 critical domain residues. By coexpressing Stac3 in dysgenic (CaV1.1-null) myotubes together with CaV1 constructs whose chimeric II-III loops had previously been tested for functionality, we reveal that the ability of Stac3 to interact with them parallels the ability of these constructs to mediate skeletal type EC coupling. Based on coexpression in tsA201 cells, the interaction of Stac3 with the II-III loop critical domain does not require the presence of the PKC C1 domain in Stac3, but it does require the first of the two SH3 domains. Collectively, our results indicate that activation of RyR1 Ca2+ release by CaV1.1 depends on Stac3 being bound to critical domain residues in the II-III loop.
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Affiliation(s)
- Alexander Polster
- Department of Physiology and Biophysics, University of Colorado Denver, Aurora, CO
| | - Benjamin R Nelson
- Department of Molecular Biology, Hamon Center for Regenerative Science and Medicine, UT Southwestern Medical Center, Dallas, TX
| | - Symeon Papadopoulos
- Institute of Vegetative Physiology, University Hospital of Cologne, Cologne, Germany
| | - Eric N Olson
- Department of Molecular Biology, Hamon Center for Regenerative Science and Medicine, UT Southwestern Medical Center, Dallas, TX
| | - Kurt G Beam
- Department of Physiology and Biophysics, University of Colorado Denver, Aurora, CO
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22
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Structural insights into binding of STAC proteins to voltage-gated calcium channels. Proc Natl Acad Sci U S A 2017; 114:E9520-E9528. [PMID: 29078335 PMCID: PMC5692558 DOI: 10.1073/pnas.1708852114] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Excitation-contraction (EC) coupling in skeletal muscle requires functional and mechanical coupling between L-type voltage-gated calcium channels (CaV1.1) and the ryanodine receptor (RyR1). Recently, STAC3 was identified as an essential protein for EC coupling and is part of a group of three proteins that can bind and modulate L-type voltage-gated calcium channels. Here, we report crystal structures of tandem-SH3 domains of different STAC isoforms up to 1.2-Å resolution. These form a rigid interaction through a conserved interdomain interface. We identify the linker connecting transmembrane repeats II and III in two different CaV isoforms as a binding site for the SH3 domains and report a crystal structure of the complex with the STAC2 isoform. The interaction site includes the location for a disease variant in STAC3 that has been linked to Native American myopathy (NAM). Introducing the mutation does not cause misfolding of the SH3 domains, but abolishes the interaction. Disruption of the interaction via mutations in the II-III loop perturbs skeletal muscle EC coupling, but preserves the ability of STAC3 to slow down inactivation of CaV1.2.
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23
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Flucher BE, Tuluc P. How and why are calcium currents curtailed in the skeletal muscle voltage-gated calcium channels? J Physiol 2017; 595:1451-1463. [PMID: 27896815 PMCID: PMC5330888 DOI: 10.1113/jp273423] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2016] [Accepted: 11/24/2016] [Indexed: 01/09/2023] Open
Abstract
Voltage‐gated calcium channels represent the sole mechanism converting electrical signals of excitable cells into cellular functions such as contraction, secretion and gene regulation. Specific voltage‐sensing domains detect changes in membrane potential and control channel gating. Calcium ions entering through the channel function as second messengers regulating cell functions, with the exception of skeletal muscle, where CaV1.1 essentially does not function as a channel but activates calcium release from intracellular stores. It has long been known that calcium currents are dispensable for skeletal muscle contraction. However, the questions as to how and why the channel function of CaV1.1 is curtailed remained obscure until the recent discovery of a developmental CaV1.1 splice variant with normal channel functions. This discovery provided new means to study the molecular mechanisms regulating the channel gating and led to the understanding that in skeletal muscle, calcium currents need to be restricted to allow proper regulation of fibre type specification and to prevent mitochondrial damage.
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Affiliation(s)
- Bernhard E Flucher
- Department of Physiology and Medical Physics, Medical University Innsbruck, Austria
| | - Petronel Tuluc
- Pharmacology and Toxicology, Institute of Pharmacy, University of Innsbruck, Austria
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24
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Dulhunty AF, Wei-LaPierre L, Casarotto MG, Beard NA. Core skeletal muscle ryanodine receptor calcium release complex. Clin Exp Pharmacol Physiol 2017; 44:3-12. [PMID: 27696487 DOI: 10.1111/1440-1681.12676] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2016] [Revised: 09/27/2016] [Accepted: 09/27/2016] [Indexed: 12/15/2022]
Abstract
The core skeletal muscle ryanodine receptor (RyR1) calcium release complex extends through three compartments of the muscle fibre, linking the extracellular environment through the cytoplasmic junctional gap to the lumen of the internal sarcoplasmic reticulum (SR) calcium store. The protein complex is essential for skeletal excitation-contraction (EC)-coupling and skeletal muscle function. Its importance is highlighted by perinatal death if any one of the EC-coupling components are missing and by myopathies associated with mutation of any of the proteins. The proteins essential for EC-coupling include the DHPR α1S subunit in the transverse tubule membrane, the DHPR β1a subunit in the cytosol and the RyR1 ion channel in the SR membrane. The other core proteins are triadin and junctin and calsequestrin, associated mainly with SR. These SR proteins are not essential for survival but exert structural and functional influences that modify the gain of EC-coupling and maintain normal muscle function. This review summarises our current knowledge of the individual protein/protein interactions within the core complex and their overall contribution to EC-coupling. We highlight significant areas that provide a continuing challenge for the field. Additional important components of the Ca2+ release complex, such as FKBP12, calmodulin, S100A1 and Stac3 are identified and reviewed elsewhere.
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Affiliation(s)
- Angela F Dulhunty
- John Curtin School of Medical Research, Australian National University, Canberra, ACT, Australia
| | - Lan Wei-LaPierre
- Department of Physiology and Pharmacology, University of Rochester Medical Center, Rochester, NY, USA
| | - Marco G Casarotto
- John Curtin School of Medical Research, Australian National University, Canberra, ACT, Australia
| | - Nicole A Beard
- Health Research Institute, University of Canberra, Canberra, ACT, Australia
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25
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The Ca 2+ influx through the mammalian skeletal muscle dihydropyridine receptor is irrelevant for muscle performance. Nat Commun 2017; 8:475. [PMID: 28883413 PMCID: PMC5589907 DOI: 10.1038/s41467-017-00629-x] [Citation(s) in RCA: 54] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2016] [Accepted: 07/14/2017] [Indexed: 01/01/2023] Open
Abstract
Skeletal muscle excitation-contraction (EC) coupling is initiated by sarcolemmal depolarization, which is translated into a conformational change of the dihydropyridine receptor (DHPR), which in turn activates sarcoplasmic reticulum (SR) Ca2+ release to trigger muscle contraction. During EC coupling, the mammalian DHPR embraces functional duality, as voltage sensor and L-type Ca2+ channel. Although its unique role as voltage sensor for conformational EC coupling is firmly established, the conventional function as Ca2+ channel is still enigmatic. Here we show that Ca2+ influx via DHPR is not necessary for muscle performance by generating a knock-in mouse where DHPR-mediated Ca2+ influx is eliminated. Homozygous knock-in mice display SR Ca2+ release, locomotor activity, motor coordination, muscle strength and susceptibility to fatigue comparable to wild-type controls, without any compensatory regulation of multiple key proteins of the EC coupling machinery and Ca2+ homeostasis. These findings support the hypothesis that the DHPR-mediated Ca2+ influx in mammalian skeletal muscle is an evolutionary remnant.In mammalian skeletal muscle, the DHPR functions as a voltage sensor to trigger muscle contraction and as a Ca2+ channel. Here the authors show that mice where Ca2+ influx through the DHPR is eliminated display no difference in skeletal muscle function, suggesting that the Ca2+ influx through this channel is vestigial.
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26
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Congenital myopathy results from misregulation of a muscle Ca2+ channel by mutant Stac3. Proc Natl Acad Sci U S A 2016; 114:E228-E236. [PMID: 28003463 DOI: 10.1073/pnas.1619238114] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Skeletal muscle contractions are initiated by an increase in Ca2+ released during excitation-contraction (EC) coupling, and defects in EC coupling are associated with human myopathies. EC coupling requires communication between voltage-sensing dihydropyridine receptors (DHPRs) in transverse tubule membrane and Ca2+ release channel ryanodine receptor 1 (RyR1) in the sarcoplasmic reticulum (SR). Stac3 protein (SH3 and cysteine-rich domain 3) is an essential component of the EC coupling apparatus and a mutation in human STAC3 causes the debilitating Native American myopathy (NAM), but the nature of how Stac3 acts on the DHPR and/or RyR1 is unknown. Using electron microscopy, electrophysiology, and dynamic imaging of zebrafish muscle fibers, we find significantly reduced DHPR levels, functionality, and stability in stac3 mutants. Furthermore, stac3NAM myofibers exhibited increased caffeine-induced Ca2+ release across a wide range of concentrations in the absence of altered caffeine sensitivity as well as increased Ca2+ in internal stores, which is consistent with increased SR luminal Ca2+ These findings define critical roles for Stac3 in EC coupling and human disease.
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Bannister RA, Sheridan DC, Beam KG. Distinct Components of Retrograde Ca(V)1.1-RyR1 Coupling Revealed by a Lethal Mutation in RyR1. Biophys J 2016; 110:912-21. [PMID: 26910427 DOI: 10.1016/j.bpj.2015.12.031] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2015] [Revised: 12/24/2015] [Accepted: 12/30/2015] [Indexed: 12/21/2022] Open
Abstract
The molecular basis for excitation-contraction coupling in skeletal muscle is generally thought to involve conformational coupling between the L-type voltage-gated Ca(2+) channel (CaV1.1) and the type 1 ryanodine receptor (RyR1). This coupling is bidirectional; in addition to the orthograde signal from CaV1.1 to RyR1 that triggers Ca(2+) release from the sarcoplasmic reticulum, retrograde signaling from RyR1 to CaV1.1 results in increased amplitude and slowed activation kinetics of macroscopic L-type Ca(2+) current. Orthograde coupling was previously shown to be ablated by a glycine for glutamate substitution at RyR1 position 4242. In this study, we investigated whether the RyR1-E4242G mutation affects retrograde coupling. L-type current in myotubes homozygous for RyR1-E4242G was substantially reduced in amplitude (∼80%) relative to that observed in myotubes from normal control (wild-type and/or heterozygous) myotubes. Analysis of intramembrane gating charge movements and ionic tail current amplitudes indicated that the reduction in current amplitude during step depolarizations was a consequence of both decreased CaV1.1 membrane expression (∼50%) and reduced channel Po (∼55%). In contrast, activation kinetics of the L-type current in RyR1-E4242G myotubes resembled those of normal myotubes, unlike dyspedic (RyR1 null) myotubes in which the L-type currents have markedly accelerated activation kinetics. Exogenous expression of wild-type RyR1 partially restored L-type current density. From these observations, we conclude that mutating residue E4242 affects RyR1 structures critical for retrograde communication with CaV1.1. Moreover, we propose that retrograde coupling has two distinct and separable components that are dependent on different structural elements of RyR1.
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Affiliation(s)
- Roger A Bannister
- Cardiology Division, Department of Medicine, University of Colorado School of Medicine, Aurora, Colorado.
| | - David C Sheridan
- Department of Biology and Earth Science, Otterbein University, Westerville, Ohio
| | - Kurt G Beam
- Department of Physiology and Biophysics, University of Colorado School of Medicine, Aurora, Colorado.
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Bannister RA. Bridging the myoplasmic gap II: more recent advances in skeletal muscle excitation-contraction coupling. ACTA ACUST UNITED AC 2016; 219:175-82. [PMID: 26792328 DOI: 10.1242/jeb.124123] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
In skeletal muscle, excitation-contraction (EC) coupling relies on the transmission of an intermolecular signal from the voltage-sensing regions of the L-type Ca(2+) channel (Ca(V)1.1) in the plasma membrane to the channel pore of the type 1 ryanodine receptor (RyR1) nearly 10 nm away in the membrane of the sarcoplasmic reticulum (SR). Even though the roles of Ca(V)1.1 and RyR1 as voltage sensor and SR Ca(2+) release channel, respectively, have been established for nearly 25 years, the mechanism underlying communication between these two channels remains undefined. In the course of this article, I will review current viewpoints on this topic with particular emphasis on recent studies.
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Affiliation(s)
- Roger A Bannister
- Department of Medicine-Cardiology Division, University of Colorado Denver-Anschutz Medical Campus, 12700 East 19th Avenue, Room 8006, B-139, Aurora, CO 80045, USA
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29
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Retrograde Coupling: Muscle's Orphan Signaling Pathway? Biophys J 2016; 110:870-1. [PMID: 26910422 DOI: 10.1016/j.bpj.2015.12.032] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2015] [Revised: 12/29/2015] [Accepted: 12/30/2015] [Indexed: 12/28/2022] Open
Abstract
In skeletal muscle excitation-contraction coupling, a voltage-gated calcium channel directly activates opening of the calcium release channel (RyR1) in the sarcoplasmic reticulum that supplies the calcium signal triggering contraction. In addition, a retrograde signal from the RyR1 facilitates gating of the voltage-gated calcium channel. Recent studies of RyR1 mutants, including the article by Bannister et al. in this issue of the Biophysical Journal, advance our understanding of the signaling mechanism, although the physiological significance of retrograde coupling remains elusive.
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Mahalingam M, Perez CF, Fessenden JD. Fluorescence Resonance Energy Transfer-based Structural Analysis of the Dihydropyridine Receptor α1S Subunit Reveals Conformational Differences Induced by Binding of the β1a Subunit. J Biol Chem 2016; 291:13762-70. [PMID: 27129199 DOI: 10.1074/jbc.m115.704049] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2015] [Indexed: 11/06/2022] Open
Abstract
The skeletal muscle dihydropyridine receptor α1S subunit plays a key role in skeletal muscle excitation-contraction coupling by sensing membrane voltage changes and then triggering intracellular calcium release. The cytoplasmic loops connecting four homologous α1S structural domains have diverse functions, but their structural arrangement is poorly understood. Here, we used a novel FRET-based method to characterize the relative proximity of these intracellular loops in α1S subunits expressed in intact cells. In dysgenic myotubes, energy transfer was observed from an N-terminal-fused YFP to a FRET acceptor, ReAsH (resorufin arsenical hairpin binder), targeted to each α1S intracellular loop, with the highest FRET efficiencies measured to the α1S II-III loop and C-terminal tail. However, in HEK-293T cells, FRET efficiencies from the α1S N terminus to the II-III and III-IV loops and the C-terminal tail were significantly lower, thus suggesting that these loop structures are influenced by the cellular microenvironment. The addition of the β1a dihydropyridine receptor subunit enhanced FRET to the II-III loop, thus indicating that β1a binding directly affects II-III loop conformation. This specific structural change required the C-terminal 36 amino acids of β1a, which are essential to support EC coupling. Direct FRET measurements between α1S and β1a confirmed that both wild type and truncated β1a bind similarly to α1S These results provide new insights into the role of muscle-specific proteins on the structural arrangement of α1S intracellular loops and point to a new conformational effect of the β1a subunit in supporting skeletal muscle excitation-contraction coupling.
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Affiliation(s)
- Mohana Mahalingam
- From the Department of Anesthesia, Perioperative and Pain Medicine, Brigham and Women's Hospital, Boston, Massachusetts 02115
| | - Claudio F Perez
- From the Department of Anesthesia, Perioperative and Pain Medicine, Brigham and Women's Hospital, Boston, Massachusetts 02115
| | - James D Fessenden
- From the Department of Anesthesia, Perioperative and Pain Medicine, Brigham and Women's Hospital, Boston, Massachusetts 02115
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31
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Benedetti B, Tuluc P, Mastrolia V, Dlaska C, Flucher BE. Physiological and pharmacological modulation of the embryonic skeletal muscle calcium channel splice variant CaV1.1e. Biophys J 2016; 108:1072-80. [PMID: 25762319 PMCID: PMC4375451 DOI: 10.1016/j.bpj.2015.01.026] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2014] [Revised: 01/13/2015] [Accepted: 01/28/2015] [Indexed: 01/05/2023] Open
Abstract
CaV1.1e is the voltage-gated calcium channel splice variant of embryonic skeletal muscle. It differs from the adult CaV1.1a splice variant by the exclusion of exon 29 coding for 19 amino acids in the extracellular loop connecting transmembrane domains IVS3 and IVS4. Like the adult splice variant CaV1.1a, the embryonic CaV1.1e variant functions as voltage sensor in excitation-contraction coupling, but unlike CaV1.1a it also conducts sizable calcium currents. Consequently, physiological or pharmacological modulation of calcium currents may have a greater impact in CaV1.1e expressing muscle cells. Here, we analyzed the effects of L-type current modulators on whole-cell current properties in dysgenic (CaV1.1-null) myotubes reconstituted with either CaV1.1a or CaV1.1e. Furthermore, we examined the physiological current modulation by interactions with the ryanodine receptor using a chimeric CaV1.1e construct in which the cytoplasmic II-III loop, essential for skeletal muscle excitation-contraction coupling, has been replaced with the corresponding but nonfunctional loop from the Musca channel. Whereas the equivalent substitution in CaV1.1a had abolished the calcium currents, substitution of the II-III loop in CaV1.1e did not significantly reduce current amplitudes. This indicates that CaV1.1e is not subject to retrograde coupling with the ryanodine receptor and that the retrograde coupling mechanism in CaV1.1a operates by counteracting the limiting effects of exon 29 inclusion on the current amplitude. Pharmacologically, CaV1.1e behaves like other L-type calcium channels. Its currents are substantially increased by the calcium channel agonist Bay K 8644 and inhibited by the calcium channel blocker nifedipine in a dose-dependent manner. With an IC50 of 0.37 μM for current inhibition by nifedipine, CaV1.1e is a potential drug target for the treatment of myotonic dystrophy. It might block the excessive calcium influx resulting from the aberrant expression of the embryonic splice variant CaV1.1e in the skeletal muscles of myotonic dystrophy patients.
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MESH Headings
- 3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester/pharmacology
- Animals
- Calcium/metabolism
- Calcium Channel Blockers/pharmacology
- Calcium Channels, L-Type/drug effects
- Calcium Channels, L-Type/genetics
- Calcium Channels, L-Type/metabolism
- Cell Line, Tumor
- Excitation Contraction Coupling
- Muscle Fibers, Skeletal/drug effects
- Muscle Fibers, Skeletal/metabolism
- Muscle Fibers, Skeletal/physiology
- Nifedipine/pharmacology
- Protein Isoforms/drug effects
- Protein Isoforms/genetics
- Protein Isoforms/metabolism
- Rats
- Ryanodine Receptor Calcium Release Channel/metabolism
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Affiliation(s)
- Bruno Benedetti
- Department of Physiology and Medical Physics, Medical University Innsbruck, Innsbruck, Austria
| | - Petronel Tuluc
- Department of Physiology and Medical Physics, Medical University Innsbruck, Innsbruck, Austria; Pharmacology and Toxicology, Institute of Pharmacy, University of Innsbruck, Innsbruck, Austria
| | - Vincenzo Mastrolia
- Department of Physiology and Medical Physics, Medical University Innsbruck, Innsbruck, Austria
| | - Clemens Dlaska
- Department of Physiology and Medical Physics, Medical University Innsbruck, Innsbruck, Austria
| | - Bernhard E Flucher
- Department of Physiology and Medical Physics, Medical University Innsbruck, Innsbruck, Austria.
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32
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Affiliation(s)
- Bernhard E Flucher
- Section of Physiology, Medical University Innsbruck, 6020 Innsbruck, Austria
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33
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Zamponi GW, Striessnig J, Koschak A, Dolphin AC. The Physiology, Pathology, and Pharmacology of Voltage-Gated Calcium Channels and Their Future Therapeutic Potential. Pharmacol Rev 2015; 67:821-70. [PMID: 26362469 PMCID: PMC4630564 DOI: 10.1124/pr.114.009654] [Citation(s) in RCA: 704] [Impact Index Per Article: 78.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Voltage-gated calcium channels are required for many key functions in the body. In this review, the different subtypes of voltage-gated calcium channels are described and their physiologic roles and pharmacology are outlined. We describe the current uses of drugs interacting with the different calcium channel subtypes and subunits, as well as specific areas in which there is strong potential for future drug development. Current therapeutic agents include drugs targeting L-type Ca(V)1.2 calcium channels, particularly 1,4-dihydropyridines, which are widely used in the treatment of hypertension. T-type (Ca(V)3) channels are a target of ethosuximide, widely used in absence epilepsy. The auxiliary subunit α2δ-1 is the therapeutic target of the gabapentinoid drugs, which are of value in certain epilepsies and chronic neuropathic pain. The limited use of intrathecal ziconotide, a peptide blocker of N-type (Ca(V)2.2) calcium channels, as a treatment of intractable pain, gives an indication that these channels represent excellent drug targets for various pain conditions. We describe how selectivity for different subtypes of calcium channels (e.g., Ca(V)1.2 and Ca(V)1.3 L-type channels) may be achieved in the future by exploiting differences between channel isoforms in terms of sequence and biophysical properties, variation in splicing in different target tissues, and differences in the properties of the target tissues themselves in terms of membrane potential or firing frequency. Thus, use-dependent blockers of the different isoforms could selectively block calcium channels in particular pathologies, such as nociceptive neurons in pain states or in epileptic brain circuits. Of important future potential are selective Ca(V)1.3 blockers for neuropsychiatric diseases, neuroprotection in Parkinson's disease, and resistant hypertension. In addition, selective or nonselective T-type channel blockers are considered potential therapeutic targets in epilepsy, pain, obesity, sleep, and anxiety. Use-dependent N-type calcium channel blockers are likely to be of therapeutic use in chronic pain conditions. Thus, more selective calcium channel blockers hold promise for therapeutic intervention.
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Affiliation(s)
- Gerald W Zamponi
- Department of Physiology and Pharmacology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada (G.W.Z.); Department of Pharmacology and Toxicology, Institute of Pharmacy, Center for Molecular Biosciences, University of Innsbruck, Innsbruck, Austria (J.S., A.K.); and Department of Neuroscience, Physiology, and Pharmacology, Division of Biosciences, University College London, London, United Kingdom (A.C.D.)
| | - Joerg Striessnig
- Department of Physiology and Pharmacology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada (G.W.Z.); Department of Pharmacology and Toxicology, Institute of Pharmacy, Center for Molecular Biosciences, University of Innsbruck, Innsbruck, Austria (J.S., A.K.); and Department of Neuroscience, Physiology, and Pharmacology, Division of Biosciences, University College London, London, United Kingdom (A.C.D.)
| | - Alexandra Koschak
- Department of Physiology and Pharmacology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada (G.W.Z.); Department of Pharmacology and Toxicology, Institute of Pharmacy, Center for Molecular Biosciences, University of Innsbruck, Innsbruck, Austria (J.S., A.K.); and Department of Neuroscience, Physiology, and Pharmacology, Division of Biosciences, University College London, London, United Kingdom (A.C.D.)
| | - Annette C Dolphin
- Department of Physiology and Pharmacology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada (G.W.Z.); Department of Pharmacology and Toxicology, Institute of Pharmacy, Center for Molecular Biosciences, University of Innsbruck, Innsbruck, Austria (J.S., A.K.); and Department of Neuroscience, Physiology, and Pharmacology, Division of Biosciences, University College London, London, United Kingdom (A.C.D.)
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Campiglio M, Flucher BE. The role of auxiliary subunits for the functional diversity of voltage-gated calcium channels. J Cell Physiol 2015; 230:2019-31. [PMID: 25820299 PMCID: PMC4672716 DOI: 10.1002/jcp.24998] [Citation(s) in RCA: 66] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2015] [Accepted: 03/23/2015] [Indexed: 11/18/2022]
Abstract
Voltage-gated calcium channels (VGCCs) represent the sole mechanism to convert membrane depolarization into cellular functions like secretion, contraction, or gene regulation. VGCCs consist of a pore-forming α1 subunit and several auxiliary channel subunits. These subunits come in multiple isoforms and splice-variants giving rise to a stunning molecular diversity of possible subunit combinations. It is generally believed that specific auxiliary subunits differentially regulate the channels and thereby contribute to the great functional diversity of VGCCs. If auxiliary subunits can associate and dissociate from pre-existing channel complexes, this would allow dynamic regulation of channel properties. However, most auxiliary subunits modulate current properties very similarly, and proof that any cellular calcium channel function is indeed modulated by the physiological exchange of auxiliary subunits is still lacking. In this review we summarize available information supporting a differential modulation of calcium channel functions by exchange of auxiliary subunits, as well as experimental evidence in support of alternative functions of the auxiliary subunits. At the heart of the discussion is the concept that, in their native environment, VGCCs function in the context of macromolecular signaling complexes and that the auxiliary subunits help to orchestrate the diverse protein–protein interactions found in these calcium channel signalosomes. Thus, in addition to a putative differential modulation of current properties, differential subcellular targeting properties and differential protein–protein interactions of the auxiliary subunits may explain the need for their vast molecular diversity. J. Cell. Physiol. 999: 00–00, 2015. © 2015 The Authors. Journal of Cellular Physiology Published by Wiley Periodicals, Inc. J. Cell. Physiol. 230: 2019–2031, 2015. © 2015 Wiley Periodicals, Inc.
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Affiliation(s)
- Marta Campiglio
- Division of Physiology, Department of Physiology and Medical Physics, Medical University Innsbruck, Innsbruck, Austria
| | - Bernhard E Flucher
- Division of Physiology, Department of Physiology and Medical Physics, Medical University Innsbruck, Innsbruck, Austria
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35
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Ohrtman JD, Romberg CF, Moua O, Bannister RA, Levinson SR, Beam KG. Apparent lack of physical or functional interaction between CaV1.1 and its distal C terminus. ACTA ACUST UNITED AC 2015; 145:303-14. [PMID: 25779869 PMCID: PMC4380213 DOI: 10.1085/jgp.201411292] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The distal C-terminal domain of CaV1.1 is not required for depolarization-induced potentiation of L-type Ca2+ current in skeletal muscle. CaV1.1 acts as both the voltage sensor that triggers excitation–contraction coupling in skeletal muscle and as an L-type Ca2+ channel. It has been proposed that, after its posttranslational cleavage, the distal C terminus of CaV1.1 remains noncovalently associated with proximal CaV1.1, and that tethering of protein kinase A to the distal C terminus is required for depolarization-induced potentiation of L-type Ca2+ current in skeletal muscle. Here, we report that association of the distal C terminus with proximal CaV1.1 cannot be detected by either immunoprecipitation of mouse skeletal muscle or by colocalized fluorescence after expression in adult skeletal muscle fibers of a CaV1.1 construct labeled with yellow fluorescent protein (YFP) and cyan fluorescent protein on the N and C termini, respectively. We found that L-type Ca2+ channel activity was similar after expression of constructs that either did (YFP-CaV1.11860) or did not (YFP-CaV1.11666) contain coding sequence for the distal C-terminal domain in dysgenic myotubes null for endogenous CaV1.1. Furthermore, in response to strong (up to 90 mV) or long-lasting prepulses (up to 200 ms), tail current amplitudes and decay times were equally increased in dysgenic myotubes expressing either YFP-CaV1.11860 or YFP-CaV1.11666, suggesting that the distal C-terminal domain was not required for depolarization-induced potentiation. Thus, our experiments do not support the existence of either biochemical or functional interactions between proximal CaV1.1 and the distal C terminus.
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Affiliation(s)
- Joshua D Ohrtman
- Department of Physiology and Biophysics and Department of Medicine-Cardiology Division, University of Colorado, Denver, Aurora, CO 80045
| | - Christin F Romberg
- Department of Physiology and Biophysics and Department of Medicine-Cardiology Division, University of Colorado, Denver, Aurora, CO 80045
| | - Ong Moua
- Department of Physiology and Biophysics and Department of Medicine-Cardiology Division, University of Colorado, Denver, Aurora, CO 80045
| | - Roger A Bannister
- Department of Physiology and Biophysics and Department of Medicine-Cardiology Division, University of Colorado, Denver, Aurora, CO 80045
| | - S Rock Levinson
- Department of Physiology and Biophysics and Department of Medicine-Cardiology Division, University of Colorado, Denver, Aurora, CO 80045
| | - Kurt G Beam
- Department of Physiology and Biophysics and Department of Medicine-Cardiology Division, University of Colorado, Denver, Aurora, CO 80045
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36
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Hu H, Wang Z, Wei R, Fan G, Wang Q, Zhang K, Yin CC. The molecular architecture of dihydropyrindine receptor/L-type Ca2+ channel complex. Sci Rep 2015; 5:8370. [PMID: 25667046 PMCID: PMC4322351 DOI: 10.1038/srep08370] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2014] [Accepted: 01/12/2015] [Indexed: 11/28/2022] Open
Abstract
Dihydropyridine receptor (DHPR), an L-type Ca2+ channel complex, plays an essential role in muscle contraction, secretion, integration of synaptic input in neurons and synaptic transmission. The molecular architecture of DHPR complex remains elusive. Here we present a 15-Å resolution cryo-electron microscopy structure of the skeletal DHPR/L-type Ca2+ channel complex. The DHPR has an asymmetrical main body joined by a hook-like extension. The main body is composed of a “trapezoid” and a “tetrahedroid”. Homologous crystal structure docking and site-specific antibody labelling revealed that the α1 and α2 subunits are located in the “trapezoid” and the β subunit is located in the “tetrahedroid”. This structure revealed the molecular architecture of a eukaryotic Ca2+ channel complex. Furthermore, this structure provides structural insights into the key elements of DHPR involved in physical coupling with the RyR/Ca2+ release channel and shed light onto the mechanism of excitation-contraction coupling.
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Affiliation(s)
- Hongli Hu
- Department of Biophysics, Peking University Health Science Centre, Peking University, 38 College Road, Beijing 100191, China
| | - Zhao Wang
- Department of Biophysics, Peking University Health Science Centre, Peking University, 38 College Road, Beijing 100191, China
| | - Risheng Wei
- Department of Biophysics, Peking University Health Science Centre, Peking University, 38 College Road, Beijing 100191, China
| | - Guizhen Fan
- Department of Biophysics, Peking University Health Science Centre, Peking University, 38 College Road, Beijing 100191, China
| | - Qiongling Wang
- Department of Biophysics, Peking University Health Science Centre, Peking University, 38 College Road, Beijing 100191, China
| | - Kaiming Zhang
- Department of Biophysics, Peking University Health Science Centre, Peking University, 38 College Road, Beijing 100191, China
| | - Chang-Cheng Yin
- Department of Biophysics, Peking University Health Science Centre, Peking University, 38 College Road, Beijing 100191, China
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37
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Eltit JM, Franzini-Armstrong C, Perez CF. Amino acid residues 489-503 of dihydropyridine receptor (DHPR) β1a subunit are critical for structural communication between the skeletal muscle DHPR complex and type 1 ryanodine receptor. J Biol Chem 2014; 289:36116-24. [PMID: 25384984 DOI: 10.1074/jbc.m114.615526] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The β1a subunit is a cytoplasmic component of the dihydropyridine receptor (DHPR) complex that plays an essential role in skeletal muscle excitation-contraction (EC) coupling. Here we investigate the role of the C-terminal end of this auxiliary subunit in the functional and structural communication between the DHPR and the Ca(2+) release channel (RyR1). Progressive truncation of the β1a C terminus showed that deletion of amino acid residues Gln(489) to Trp(503) resulted in a loss of depolarization-induced Ca(2+) release, a severe reduction of L-type Ca(2+) currents, and a lack of tetrad formation as evaluated by freeze-fracture analysis. However, deletion of this domain did not affect expression/targeting or density (Qmax) of the DHPR-α1S subunit to the plasma membrane. Within this motif, triple alanine substitution of residues Leu(496), Leu(500), and Trp(503), which are thought to mediate direct β1a-RyR1 interactions, weakened EC coupling but did not replicate the truncated phenotype. Therefore, these data demonstrate that an amino acid segment encompassing sequence (489)QVQVLTSLRRNLSFW(503) of β1a contains critical determinant(s) for the physical link of DHPR and RyR1, further confirming a direct correspondence between DHPR positioning and DHPR/RyR functional interactions. In addition, our data strongly suggest that the motif Leu(496)-Leu(500)-Trp(503) within the β1a C-terminal tail plays a nonessential role in the bidirectional DHPR/RyR1 signaling that supports skeletal-type EC coupling.
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Affiliation(s)
- Jose M Eltit
- the Department of Physiology and Biophysics, School of Medicine, Virginia Commonwealth University, Richmond, Virgina 23298, and
| | - Clara Franzini-Armstrong
- the Department of Cell and Developmental Biology, University of Pennsylvania, Philadelphia, Pennsylvania 19104
| | - Claudio F Perez
- From the Department of Anesthesiology Perioperative and Pain Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts 02115,
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38
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Rebbeck RT, Karunasekara Y, Board PG, Beard NA, Casarotto MG, Dulhunty AF. Skeletal muscle excitation–contraction coupling: Who are the dancing partners? Int J Biochem Cell Biol 2014; 48:28-38. [DOI: 10.1016/j.biocel.2013.12.001] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2013] [Revised: 11/29/2013] [Accepted: 12/04/2013] [Indexed: 01/15/2023]
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39
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Atlas D. Voltage-gated calcium channels function as Ca2+-activated signaling receptors. Trends Biochem Sci 2014; 39:45-52. [PMID: 24388968 DOI: 10.1016/j.tibs.2013.12.005] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2013] [Revised: 11/24/2013] [Accepted: 12/09/2013] [Indexed: 02/06/2023]
Abstract
Voltage-gated calcium channels (VGCCs) are transmembrane cell surface proteins responsible for multifunctional signals. In response to voltage, VGCCs trigger synaptic transmission, drive muscle contraction, and regulate gene expression. Voltage perturbations open VGCCs enabling Ca(2+) binding to the low affinity Ca(2+) binding site of the channel pore. Subsequent to permeation, Ca(2+) targets selective proteins to activate diverse signaling pathways. It is becoming apparent that the Ca(2+)-bound channel triggers secretion in excitable cells and drives contraction in cardiomyocytes prior to Ca(2+) permeation. Here, I highlight recent data implicating receptor-like function of the Ca(2+)-bound channel in converting external Ca(2+) into an intracellular signal. The two sequential mechanistic perspectives of VGCC function are discussed in the context of the prevailing and long-standing current models of depolarization-evoked secretion and cardiac contraction.
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Affiliation(s)
- Daphne Atlas
- Department of Biological Chemistry, The Alexander Silverman Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem, 91904 Israel.
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Ca2+ channel and Na+/Ca2+ exchange localization in cardiac myocytes. J Mol Cell Cardiol 2013; 58:22-31. [DOI: 10.1016/j.yjmcc.2012.11.022] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/21/2012] [Revised: 11/20/2012] [Accepted: 11/28/2012] [Indexed: 01/01/2023]
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Campiglio M, Di Biase V, Tuluc P, Flucher BE. Stable incorporation versus dynamic exchange of β subunits in a native Ca2+ channel complex. J Cell Sci 2013; 126:2092-101. [PMID: 23447673 DOI: 10.1242/jcs.jcs124537] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Voltage-gated Ca(2+) channels are multi-subunit membrane proteins that transduce depolarization into cellular functions such as excitation-contraction coupling in muscle or neurotransmitter release in neurons. The auxiliary β subunits function in membrane targeting of the channel and modulation of its gating properties. However, whether β subunits can reversibly interact with, and thus differentially modulate, channels in the membrane is still unresolved. In the present study we applied fluorescence recovery after photobleaching (FRAP) of GFP-tagged α1 and β subunits expressed in dysgenic myotubes to study the relative dynamics of these Ca(2+) channel subunits for the first time in a native functional signaling complex. Identical fluorescence recovery rates of both subunits indicate stable interactions, distinct recovery rates indicate dynamic interactions. Whereas the skeletal muscle β1a isoform formed stable complexes with CaV1.1 and CaV1.2, the non-skeletal muscle β2a and β4b isoforms dynamically interacted with both α1 subunits. Neither replacing the I-II loop of CaV1.1 with that of CaV2.1, nor deletions in the proximal I-II loop, known to change the orientation of β relative to the α1 subunit, altered the specific dynamic properties of the β subunits. In contrast, a single residue substitution in the α interaction pocket of β1aM293A increased the FRAP rate threefold. Taken together, these findings indicate that in skeletal muscle triads the homologous β1a subunit forms a stable complex, whereas the heterologous β2a and β4b subunits form dynamic complexes with the Ca(2+) channel. The distinct binding properties are not determined by differences in the I-II loop sequences of the α1 subunits, but are intrinsic properties of the β subunit isoforms.
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Affiliation(s)
- Marta Campiglio
- Department of Physiology and Medical Physics, Medical University Innsbruck, A-6020 Innsbruck, Austria
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Dantrolene-induced inhibition of skeletal L-type Ca2+ current requires RyR1 expression. BIOMED RESEARCH INTERNATIONAL 2012; 2013:390493. [PMID: 23509717 PMCID: PMC3591246 DOI: 10.1155/2013/390493] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/20/2012] [Revised: 06/06/2012] [Accepted: 06/06/2012] [Indexed: 11/23/2022]
Abstract
Malignant hyperthermia (MH) is a pharmacogenetic disorder most often linked to mutations in the type 1 ryanodine receptor (RyR1) or the skeletal L-type Ca2+ channel (CaV1.1). The only effective treatment for an MH crisis is administration of the hydantoin derivative Dantrolene. In addition to reducing voltage induced Ca2+ release from the sarcoplasmic reticulum, Dantrolene was recently found to inhibit L-type currents in developing myotubes by shifting the voltage-dependence of CaV1.1 channel activation to more depolarizing potentials. Thus, the purpose of this study was to obtain information regarding the mechanism of Dantrolene-induced inhibition of CaV1.1. A mechanism involving a general depression of plasma membrane excitability was excluded because the biophysical properties of skeletal muscle Na+ current in normal mouse myotubes were largely unaffected by exposure to Dantrolene. However, a role for RyR1 was evident as Dantrolene failed to alter the amplitude, voltage dependence and inactivation kinetics of L-type currents recorded from dyspedic (RyR1 null) myotubes. Taken together, these results suggest that the mechanism of Dantrolene-induced inhibition of the skeletal muscle L-type Ca2+ current is related to altered communication between CaV1.1 and RyR1.
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Szpyt J, Lorenzon N, Perez CF, Norris E, Allen PD, Beam KG, Samsó M. Three-dimensional localization of the α and β subunits and of the II-III loop in the skeletal muscle L-type Ca2+ channel. J Biol Chem 2012; 287:43853-61. [PMID: 23118233 DOI: 10.1074/jbc.m112.419283] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The L-type Ca(2+) channel (dihydropyridine receptor (DHPR) in skeletal muscle acts as the voltage sensor for excitation-contraction coupling. To better resolve the spatial organization of the DHPR subunits (α(1s) or Ca(V)1.1, α(2), β(1a), δ1, and γ), we created transgenic mice expressing a recombinant β(1a) subunit with YFP and a biotin acceptor domain attached to its N- and C- termini, respectively. DHPR complexes were purified from skeletal muscle, negatively stained, imaged by electron microscopy, and subjected to single-particle image analysis. The resulting 19.1-Å resolution, three-dimensional reconstruction shows a main body of 17 × 11 × 8 nm with five corners along its perimeter. Two protrusions emerge from either face of the main body: the larger one attributed to the α(2)-δ1 subunit that forms a flexible hook-shaped feature and a smaller protrusion on the opposite side that corresponds to the II-III loop of Ca(V)1.1 as revealed by antibody labeling. Novel features discernible in the electron density accommodate the atomic coordinates of a voltage-gated sodium channel and of the β subunit in a single docking possibility that defines the α1-β interaction. The β subunit appears more closely associated to the membrane than expected, which may better account for both its role in localizing the α(1s) subunit to the membrane and its suggested role in excitation-contraction coupling.
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Affiliation(s)
- John Szpyt
- Department of Anesthesia, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts 02115, USA
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Polster A, Ohrtman JD, Beam KG, Papadopoulos S. Fluorescence resonance energy transfer (FRET) indicates that association with the type I ryanodine receptor (RyR1) causes reorientation of multiple cytoplasmic domains of the dihydropyridine receptor (DHPR) α(1S) subunit. J Biol Chem 2012; 287:41560-8. [PMID: 23071115 DOI: 10.1074/jbc.m112.404194] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The skeletal muscle dihydropyridine receptor (DHPR) in the t-tubular membrane serves as the Ca(2+) channel and voltage sensor for excitation-contraction (EC) coupling, triggering Ca(2+) release via the type 1 ryanodine receptor (RyR1) in the sarcoplasmic reticulum (SR). The two proteins appear to be physically linked, and both the α(1S) and β(1a) subunits of the DHPR are essential for EC coupling. Within α(1S), cytoplasmic domains of importance include the I-II loop (to which β(1a) binds), the II-III and III-IV loops, and the C terminus. However, the spatial relationship of these domains to one another has not been established. Here, we have taken the approach of measuring FRET between fluorescent proteins inserted into pairs of α(1S) cytoplasmic domains. Expression of these constructs in dyspedic (RyR1 null) and dysgenic (α(1S) null) myotubes was used to test for function and targeting to plasma membrane/SR junctions and to test whether the presence of RyR1 caused altered FRET. We found that in the absence of RyR1, measureable FRET occurred between the N terminus and C terminus (residue 1636), and between the II-III loop (residue 626) and both the N and C termini; the I-II loop (residue 406) showed weak FRET with the II-III loop but not with the N terminus. Association with RyR1 caused II-III loop FRET to decrease with the C terminus and increase with the N terminus and caused I-II loop FRET to increase with both the II-III loop and N terminus. Overall, RyR1 appears to cause a substantial reorientation of the cytoplasmic α(1S) domains consistent with their becoming more closely packed.
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Affiliation(s)
- Alexander Polster
- Department of Vegetative Physiology, University of Cologne, D-50931 Cologne, Germany
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Bannister RA, Beam KG. Ca(V)1.1: The atypical prototypical voltage-gated Ca²⁺ channel. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2012; 1828:1587-97. [PMID: 22982493 DOI: 10.1016/j.bbamem.2012.09.007] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/04/2012] [Revised: 09/04/2012] [Accepted: 09/05/2012] [Indexed: 11/28/2022]
Abstract
Ca(V)1.1 is the prototype for the other nine known Ca(V) channel isoforms, yet it has functional properties that make it truly atypical of this group. Specifically, Ca(V)1.1 is expressed solely in skeletal muscle where it serves multiple purposes; it is the voltage sensor for excitation-contraction coupling and it is an L-type Ca²⁺ channel which contributes to a form of activity-dependent Ca²⁺ entry that has been termed Excitation-coupled Ca²⁺ entry. The ability of Ca(V)1.1 to serve as voltage-sensor for excitation-contraction coupling appears to be unique among Ca(V) channels, whereas the physiological role of its more conventional function as a Ca²⁺ channel has been a matter of uncertainty for nearly 50 years. In this chapter, we discuss how Ca(V)1.1 supports excitation-contraction coupling, the possible relevance of Ca²⁺ entry through Ca(V)1.1 and how alterations of Ca(V)1.1 function can have pathophysiological consequences. This article is part of a Special Issue entitled: Calcium channels.
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Affiliation(s)
- Roger A Bannister
- Department of Medicine, Cardiology Division, University of Colorado Denver-Anschutz Medical Campus, Aurora, CO 80045, USA.
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The IQ motif is crucial for Cav1.1 function. J Biomed Biotechnol 2011; 2011:504649. [PMID: 22162637 PMCID: PMC3228397 DOI: 10.1155/2011/504649] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2011] [Revised: 08/19/2011] [Accepted: 08/22/2011] [Indexed: 11/17/2022] Open
Abstract
Ca2+-dependent modulation via calmodulin, with consensus CaM-binding IQ motif playing a key role, has been documented for most high-voltage-activated Ca2+ channels. The skeletal muscle Cav1.1 also exhibits Ca2+-/CaM-dependent modulation. Here, whole-cell Ca2+ current, Ca2+ transient, and maximal, immobilization-resistant charge movement (Qmax) recordings were obtained from cultured mouse myotubes, to test a role of IQ motif in function of Cav1.1. The effect of introducing mutation (IQ to AA) of IQ motif into Cav1.1 was examined. In dysgenic myotubes expressing YFP-Cav1.1AA, neither Ca2+ currents nor evoked Ca2+ transients were detectable. The loss of Ca2+ current and excitation-contraction coupling did not appear to be a consequence of defective trafficking to the sarcolemma. The Qmax in dysgenic myotubes expressing YFP-Cav1.1AA was similar to that of normal myotubes. These findings suggest that the IQ motif of the Cav1.1 may be an unrecognized site of structural and functional coupling between DHPR and RyR.
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Tuluc P, Flucher BE. Divergent biophysical properties, gating mechanisms, and possible functions of the two skeletal muscle Ca(V)1.1 calcium channel splice variants. J Muscle Res Cell Motil 2011; 32:249-56. [PMID: 22057633 DOI: 10.1007/s10974-011-9270-9] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2011] [Accepted: 10/12/2011] [Indexed: 11/29/2022]
Abstract
Voltage-gated calcium channels are multi-subunit protein complexes that specifically allow calcium ions to enter the cell in response to membrane depolarization. But, for many years it seemed that the skeletal muscle calcium channel Ca(V)1.1 is the exception. The classical splice variant Ca(V)1.1a activates slowly, has a very small current amplitude and poor voltage sensitivity. In fact adult muscle fibers work perfectly well even in the absence of calcium influx. Recently a new splice variant of the skeletal muscle calcium channel Ca(V)1.1e has been characterized. The lack of the 19 amino acid exon 29 in this splice variant results in a rapidly activating calcium channel with high current amplitude and good voltage sensitivity. Ca(V)1.1e is the dominant channel in embryonic muscle, where the expression of this high calcium-conducting Ca(V)1.1 isoform readily explains developmental processes depending on L-type calcium currents. Moreover, the availability of these two structurally similar but functionally distinct channel variants facilitates the analysis of the molecular mechanisms underlying the unique current properties of the classical Ca(V)1.1a channel.
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Affiliation(s)
- Petronel Tuluc
- Department of Physiology and Medical Physics, Medical University Innsbruck, Fritz-Pregl-Str. 3, 6020, Innsbruck, Austria.
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Huang CLH, Pedersen TH, Fraser JA. Reciprocal dihydropyridine and ryanodine receptor interactions in skeletal muscle activation. J Muscle Res Cell Motil 2011; 32:171-202. [PMID: 21993921 DOI: 10.1007/s10974-011-9262-9] [Citation(s) in RCA: 110] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2011] [Accepted: 09/12/2011] [Indexed: 11/25/2022]
Abstract
Dihydropyridine (DHPR) and ryanodine receptors (RyRs) are central to transduction of transverse (T) tubular membrane depolarisation initiated by surface action potentials into release of sarcoplasmic reticular (SR) Ca2+ in skeletal muscle excitation-contraction coupling. Electronmicroscopic methods demonstrate an orderly positioning of such tubular DHPRs relative to RyRs in the SR at triad junctions where their membranes come into close proximity. Biochemical and genetic studies associated expression of specific, DHPR and RyR, isoforms with the particular excitation-contraction coupling processes and related elementary Ca2+ release events found respectively in skeletal and cardiac muscle. Physiological studies of intramembrane charge movements potentially related to voltage triggering of Ca2+ release demonstrated a particular qγ charging species identifiable with DHPRs through its T-tubular localization, pharmacological properties, and steep voltage-dependence paralleling Ca2+ release. Its nonlinear kinetics implicated highly co-operative conformational events in its transitions in response to voltage change. The effects of DHPR and RyR agonists and antagonists upon this intramembrane charge in turn implicated reciprocal rather than merely unidirectional DHPR-RyR interactions in these complex reactions. Thus, following membrane potential depolarization, an orthograde qγ-DHPR-RyR signaling likely initiates conformational alterations in the RyR with which it makes contact. The latter changes could then retrogradely promote further qγ-DHPR transitions through reciprocal co-operative allosteric interactions between receptors. These would relieve the resting constraints on both further, delayed, nonlinear qγ-DHPR charge transfers and on RyR-mediated Ca2+ release. They would also explain the more rapid charging and recovery qγ transients following larger depolarizations and membrane potential repolarization to the resting level.
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Affiliation(s)
- Christopher L-H Huang
- Physiological Laboratory, Department of Biochemistry, University of Cambridge, Cambridge, CB2 3EG, UK.
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Reduced gain of excitation-contraction coupling in triadin-null myotubes is mediated by the disruption of FKBP12/RyR1 interaction. Cell Calcium 2011; 49:128-35. [PMID: 21310482 DOI: 10.1016/j.ceca.2011.01.005] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2010] [Revised: 01/10/2011] [Accepted: 01/12/2011] [Indexed: 02/01/2023]
Abstract
Several studies have suggested that triadin (Tdn) may be a critical component of skeletal EC-coupling. However, using Tdn-null mice we have shown that triadin ablation results in no significant disruption of skeletal EC-coupling. To analyze the role of triadin in EC-coupling signaling here we used whole-cell voltage clamp and simultaneous recording of intracellular Ca²+ release to characterize the retrograde and orthograde signaling between RyR1 and DHPR in cultured myotubes. DHPR Ca²+ currents elicited by depolarization of Wt and Tdn-null myotubes displayed similar current densities and voltage dependence. However, kinetic analysis of the Ca²+ current shows that activation time constant of the slow component was slightly decreased in Tdn-null cells. Voltage-evoked Ca²+ transient of Tdn-null myotubes showed small but significant reduction in peak fluorescence amplitude but no differences in voltage dependence. This difference in Ca²+ amplitude was averted by over-expression of FKBP12.6. Our results show that bi-directional signaling between DHPR and RyR1 is preserved nearly intact in Tdn-null myotubes and that the effect of triadin ablation on Ca²+ transients appears to be secondary to the reduced FKBP12 binding capacity of RyR1 in Tdn-null myotubes. These data suggest that skeletal triadins do not play a direct role in skeletal EC-coupling.
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50
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Tae HS, Cui Y, Karunasekara Y, Board PG, Dulhunty AF, Casarotto MG. Cyclization of the intrinsically disordered α1S dihydropyridine receptor II-III loop enhances secondary structure and in vitro function. J Biol Chem 2011; 286:22589-99. [PMID: 21525002 DOI: 10.1074/jbc.m110.205476] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
A key component of excitation contraction (EC) coupling in skeletal muscle is the cytoplasmic linker (II-III loop) between the second and third transmembrane repeats of the α(1S) subunit of the dihydropyridine receptor (DHPR). The II-III loop has been previously examined in vitro using a linear II-III loop with unrestrained N- and C-terminal ends. To better reproduce the loop structure in its native environment (tethered to the DHPR transmembrane domains), we have joined the N and C termini using intein-mediated technology. Circular dichroism and NMR spectroscopy revealed a structural shift in the cyclized loop toward a protein with increased α-helical and β-strand structure in a region of the loop implicated in its in vitro function and also in a critical region for EC coupling. The affinity of binding of the II-III loop binding to the SPRY2 domain of the skeletal ryanodine receptor (RyR1) increased 4-fold, and its ability to activate RyR1 channels in lipid bilayers was enhanced 3-fold by cyclization. These functional changes were predicted consequences of the structural enhancement. We suggest that tethering the N and C termini stabilized secondary structural elements in the DHPR II-III loop and may reflect structural and dynamic characteristics of the loop that are inherent in EC coupling.
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Affiliation(s)
- Han-Shen Tae
- John Curtin School of Medical Research, Australian National University, PO Box 334, Canberra, Australian Capital Territory 2601, Australia
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