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Xu J, Liao C, Yin CC, Li G, Zhu Y, Sun F. In situ structural insights into the excitation-contraction coupling mechanism of skeletal muscle. SCIENCE ADVANCES 2024; 10:eadl1126. [PMID: 38507485 PMCID: PMC10954225 DOI: 10.1126/sciadv.adl1126] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/28/2023] [Accepted: 02/12/2024] [Indexed: 03/22/2024]
Abstract
Excitation-contraction coupling (ECC) is a fundamental mechanism in control of skeletal muscle contraction and occurs at triad junctions, where dihydropyridine receptors (DHPRs) on transverse tubules sense excitation signals and then cause calcium release from the sarcoplasmic reticulum via coupling to type 1 ryanodine receptors (RyR1s), inducing the subsequent contraction of muscle filaments. However, the molecular mechanism remains unclear due to the lack of structural details. Here, we explored the architecture of triad junction by cryo-electron tomography, solved the in situ structure of RyR1 in complex with FKBP12 and calmodulin with the resolution of 16.7 Angstrom, and found the intact RyR1-DHPR supercomplex. RyR1s arrange into two rows on the terminal cisternae membrane by forming right-hand corner-to-corner contacts, and tetrads of DHPRs bind to RyR1s in an alternating manner, forming another two rows on the transverse tubule membrane. This unique arrangement is important for synergistic calcium release and provides direct evidence of physical coupling in ECC.
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Affiliation(s)
- Jiashu Xu
- Key Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Chenyi Liao
- Laboratory of Molecular Modeling and Design, State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China
| | - Chang-Cheng Yin
- Department of Biophysics, The Health Science Center, Peking University, Beijing 100191, China
- Electron Microscopy Analysis Laboratory, The Health Science Center, Peking University, Beijing 100191, China
- Center for Protein Science, Peking University, Beijing 100871, China
| | - Guohui Li
- Laboratory of Molecular Modeling and Design, State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China
| | - Yun Zhu
- Key Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
| | - Fei Sun
- Key Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
- University of Chinese Academy of Sciences, Beijing 100049, China
- Center for Biological Imaging, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
- Bioland Laboratory (Guangzhou Regenerative Medicine and Health Guangdong Laboratory), Guangzhou, Guangdong, 510005, China
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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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The distal C terminus of the dihydropyridine receptor β 1a subunit is essential for tetrad formation in skeletal muscle. Proc Natl Acad Sci U S A 2022; 119:e2201136119. [PMID: 35507876 PMCID: PMC9171810 DOI: 10.1073/pnas.2201136119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
SignificanceVertebrate skeletal muscle excitation-contraction coupling (ECC) is based on Ca2+-influx-independent interchannel cross-talk between DHPR and RyR1. The skeletal muscle DHPR complex consists of the main, voltage-sensing, and pore-forming α1S subunit, the auxiliary β1a, α2δ-1, γ1 subunits, and Stac3. The DHPRβ1a subunit plays an essential role in full triad targeting of DHPRα1S, voltage sensing, and tetrad formation (grouping of four DHPRs)-the three prerequisites for skeletal muscle ECC. Hence, a lack of DHPRβ1a results in a lethal phenotype in both β1-null mice and zebrafish. Here, we identified the nonconserved, distal C terminus of DHPRβ1a as playing a pivotal role in the formation of DHPR tetrads, and thus allosteric DHPR-RyR1 coupling, essential for proper skeletal muscle ECC.
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Vergnol A, Traoré M, Pietri-Rouxel F, Falcone S. New Insights in CaVβ Subunits: Role in the Regulation of Gene Expression and Cellular Homeostasis. Front Cell Dev Biol 2022; 10:880441. [PMID: 35465309 PMCID: PMC9019481 DOI: 10.3389/fcell.2022.880441] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2022] [Accepted: 03/16/2022] [Indexed: 11/23/2022] Open
Abstract
The voltage-gated calcium channels (CaVs or VGCCs) are fundamental regulators of intracellular calcium homeostasis. When electrical activity induces their activation, the influx of calcium that they mediate or their interaction with intracellular players leads to changes in intracellular Ca2+ levels which regulate many processes such as contraction, secretion and gene expression, depending on the cell type. The essential component of the pore channel is the CaVα1 subunit. However, the fine-tuning of Ca2+-dependent signals is guaranteed by the modulatory role of the auxiliary subunits β, α2δ, and γ of the CaVs. In particular, four different CaVβ proteins (CaVβ1, CaVβ2, CaVβ3, and CaVβ4) are encoded by four different genes in mammalians, each of them displaying several splice variants. Some of these isoforms have been described in regulating CaVα1 docking and stability at the membrane and controlling the channel complex’s conformational changes. In addition, emerging evidences have highlighted other properties of the CaVβ subunits, independently of α1 and non-correlated to its channel or voltage sensing functions. This review summarizes the recent findings reporting novel roles of the auxiliary CaVβ subunits and in particular their direct or indirect implication in regulating gene expression in different cellular contexts.
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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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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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7
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Velázquez-Marrero C, Custer EE, Marrero H, Ortiz-Miranda S, Lemos JR. Voltage-induced Ca 2+ release by ryanodine receptors causes neuropeptide secretion from nerve terminals. J Neuroendocrinol 2020; 32:e12840. [PMID: 32227430 DOI: 10.1111/jne.12840] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/14/2019] [Revised: 02/21/2020] [Accepted: 02/24/2020] [Indexed: 11/28/2022]
Abstract
Depolarisation-secretion coupling is assumed to be dependent only on extracellular calcium ([Ca2+ ]o ). Ryanodine receptor (RyR)-sensitive stores in hypothalamic neurohypophysial system (HNS) terminals produce sparks of intracellular calcium ([Ca2+ ]i ) that are voltage-dependent. We hypothesised that voltage-elicited increases in intraterminal calcium are crucial for neuropeptide secretion from presynaptic terminals, whether from influx through voltage-gated calcium channels and/or from such voltage-sensitive ryanodine-mediated calcium stores. Increases in [Ca2+ ]i upon depolarisation in the presence of voltage-gated calcium channel blockers, or in the absence of [Ca2+ ]o , still give rise to neuropeptide secretion from HNS terminals. Even in 0 [Ca2+ ]o , there was nonetheless an increase in capacitance suggesting exocytosis upon depolarisation. This was blocked by antagonist concentrations of ryanodine, as was peptide secretion elicited by high K+ in 0 [Ca2+ ]o . Furthermore, such depolarisations lead to increases in [Ca2+ ]i . Pre-incubation with BAPTA-AM resulted in > 50% inhibition of peptide secretion elicited by high K+ in 0 [Ca2+ ]o . Nifedipine but not nicardipine inhibited both the high K+ response for neuropeptide secretion and intraterminal calcium, suggesting the involvement of CaV1.1 type channels as sensors in voltage-induced calcium release. Importantly, RyR antagonists also modulate neuropeptide release under normal physiological conditions. In conclusion, our results indicate that depolarisation-induced neuropeptide secretion is present in the absence of external calcium, and calcium release from ryanodine-sensitive internal stores is a significant physiological contributor to neuropeptide secretion from HNS terminals.
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Affiliation(s)
| | - Edward E Custer
- Departments of Microbiology and Physiological Systems, Neurobiology & Program in Neuroscience, University of Massachusetts Medical School, Worcester, MA, USA
| | - Héctor Marrero
- Institute of Neurobiology, University of Puerto Rico, San Juan, PR, USA
| | - Sonia Ortiz-Miranda
- Departments of Microbiology and Physiological Systems, Neurobiology & Program in Neuroscience, University of Massachusetts Medical School, Worcester, MA, USA
| | - José R Lemos
- Departments of Microbiology and Physiological Systems, Neurobiology & Program in Neuroscience, University of Massachusetts Medical School, Worcester, MA, USA
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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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9
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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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10
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Traoré M, Gentil C, Benedetto C, Hogrel JY, De la Grange P, Cadot B, Benkhelifa-Ziyyat S, Julien L, Lemaitre M, Ferry A, Piétri-Rouxel F, Falcone S. An embryonic CaVβ1 isoform promotes muscle mass maintenance via GDF5 signaling in adult mouse. Sci Transl Med 2019; 11:11/517/eaaw1131. [DOI: 10.1126/scitranslmed.aaw1131] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2018] [Revised: 07/17/2019] [Accepted: 09/30/2019] [Indexed: 12/15/2022]
Abstract
Deciphering the mechanisms that govern skeletal muscle plasticity is essential to understand its pathophysiological processes, including age-related sarcopenia. The voltage-gated calcium channel CaV1.1 has a central role in excitation-contraction coupling (ECC), raising the possibility that it may also initiate the adaptive response to changes during muscle activity. Here, we revealed the existence of a gene transcription switch of the CaV1.1 β subunit (CaVβ1) that is dependent on the innervation state of the muscle in mice. In a mouse model of sciatic denervation, we showed increased expression of an embryonic isoform of the subunit that we called CaVβ1E. CaVβ1E boosts downstream growth differentiation factor 5 (GDF5) signaling to counteract muscle loss after denervation in mice. We further reported that aged mouse muscle expressed lower quantity of CaVβ1E compared with young muscle, displaying an altered GDF5-dependent response to denervation. Conversely, CaVβ1E overexpression improved mass wasting in aging muscle in mice by increasing GDF5 expression. We also identified the human CaVβ1E analogous and show a correlation between CaVβ1E expression in human muscles and age-related muscle mass decline. These results suggest that strategies targeting CaVβ1E or GDF5 might be effective in reducing muscle mass loss in aging.
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Affiliation(s)
| | - Christel Gentil
- Sorbonne Université, Centre de Recherche en Myologie, UM76, INSERM U974, Institut de Myologie, F-75013, Paris, France
| | - Chiara Benedetto
- Sorbonne Université, Centre de Recherche en Myologie, UM76, INSERM U974, Institut de Myologie, F-75013, Paris, France
| | - Jean-Yves Hogrel
- Institut de Myologie, GH Pitié-Salpêtrière, F-75013 Paris, France
| | | | - Bruno Cadot
- Sorbonne Université, Centre de Recherche en Myologie, UM76, INSERM U974, Institut de Myologie, F-75013, Paris, France
| | - Sofia Benkhelifa-Ziyyat
- Sorbonne Université, Centre de Recherche en Myologie, UM76, INSERM U974, Institut de Myologie, F-75013, Paris, France
| | - Laura Julien
- Sorbonne Université, Centre de Recherche en Myologie, UM76, INSERM U974, Institut de Myologie, F-75013, Paris, France
| | | | - Arnaud Ferry
- Sorbonne Université, Centre de Recherche en Myologie, UM76, INSERM U974, Institut de Myologie, F-75013, Paris, France
| | - France Piétri-Rouxel
- Sorbonne Université, Centre de Recherche en Myologie, UM76, INSERM U974, Institut de Myologie, F-75013, Paris, France
| | - Sestina Falcone
- Sorbonne Université, Centre de Recherche en Myologie, UM76, INSERM U974, Institut de Myologie, F-75013, Paris, France
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11
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Hernández-Ochoa EO, Schneider MF. Voltage sensing mechanism in skeletal muscle excitation-contraction coupling: coming of age or midlife crisis? Skelet Muscle 2018; 8:22. [PMID: 30025545 PMCID: PMC6053751 DOI: 10.1186/s13395-018-0167-9] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2018] [Accepted: 06/26/2018] [Indexed: 11/10/2022] Open
Abstract
The process by which muscle fiber electrical depolarization is linked to activation of muscle contraction is known as excitation-contraction coupling (ECC). Our understanding of ECC has increased enormously since the early scientific descriptions of the phenomenon of electrical activation of muscle contraction by Galvani that date back to the end of the eighteenth century. Major advances in electrical and optical measurements, including muscle fiber voltage clamp to reveal membrane electrical properties, in conjunction with the development of electron microscopy to unveil structural details provided an elegant view of ECC in skeletal muscle during the last century. This surge of knowledge on structural and biophysical aspects of the skeletal muscle was followed by breakthroughs in biochemistry and molecular biology, which allowed for the isolation, purification, and DNA sequencing of the muscle fiber membrane calcium channel/transverse tubule (TT) membrane voltage sensor (Cav1.1) for ECC and of the muscle ryanodine receptor/sarcoplasmic reticulum Ca2+ release channel (RyR1), two essential players of ECC in skeletal muscle. In regard to the process of voltage sensing for controlling calcium release, numerous studies support the concept that the TT Cav1.1 channel is the voltage sensor for ECC, as well as also being a Ca2+ channel in the TT membrane. In this review, we present early and recent findings that support and define the role of Cav1.1 as a voltage sensor for ECC.
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Affiliation(s)
- Erick O. Hernández-Ochoa
- Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, 108 N. Greene Street, Baltimore, MD 21201 USA
| | - Martin F. Schneider
- Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, 108 N. Greene Street, Baltimore, MD 21201 USA
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Perez CF, Eltit JM, Lopez JR, Bodnár D, Dulhunty AF, Aditya S, Casarotto MG. Functional and structural characterization of a novel malignant hyperthermia-susceptible variant of DHPR-β 1a subunit (CACNB1). Am J Physiol Cell Physiol 2017; 314:C323-C333. [PMID: 29212769 DOI: 10.1152/ajpcell.00187.2017] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Malignant hyperthermia (MH) susceptibility has been recently linked to a novel variant of β1a subunit of the dihydropyridine receptor (DHPR), a channel essential for Ca2+ regulation in skeletal muscle. Here we evaluate the effect of the mutant variant V156A on the structure/function of DHPR β1a subunit and assess its role on Ca2+ metabolism of cultured myotubes. Using differential scanning fluorimetry, we show that mutation V156A causes a significant reduction in thermal stability of the Src homology 3/guanylate kinase core domain of β1a subunit. Expression of the variant subunit in β1-null mouse myotubes resulted in increased sensitivity to caffeine stimulation. Whole cell patch-clamp analysis of β1a-V156A-expressing myotubes revealed a -2 mV shift in voltage dependence of channel activation, but no changes in Ca2+ conductance, current kinetics, or sarcoplasmic reticulum Ca2+ load were observed. Measurement of resting free Ca2+ and Na+ concentrations shows that both cations were significantly elevated in β1a-V156A-expressing myotubes and that these changes were linked to increased rates of plasmalemmal Ca2+ entry through Na+/Ca2+ exchanger and/or transient receptor potential canonical channels. Overall, our data show that mutant variant V156A results in instability of protein subdomains of β1a subunit leading to a phenotype of Ca2+ dysregulation that partly resembles that of other MH-linked mutations of DHPR α1S subunit. These data prove that homozygous expression of variant β1a-V156A has the potential to be a pathological variant, although it may require other gene defects to cause a full MH phenotype.
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Affiliation(s)
- Claudio F Perez
- Department of Anesthesiology, Brigham and Women's Hospital, Harvard Medical School , Boston, Massachusetts
| | - Jose M Eltit
- Department of Physiology and Biophysics, School of Medicine, Virginia Commonwealth University , Richmond, Virginia
| | - Jose R Lopez
- Department of Molecular Biosciences, University of California , Davis, California
| | - Dóra Bodnár
- Department of Anesthesiology, Brigham and Women's Hospital, Harvard Medical School , Boston, Massachusetts
| | - Angela F Dulhunty
- John Curtin School of Medical Research, Australian National University , Canberra , Australia
| | - Shouvik Aditya
- John Curtin School of Medical Research, Australian National University , Canberra , Australia
| | - Marco G Casarotto
- John Curtin School of Medical Research, Australian National University , Canberra , Australia
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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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14
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Norris NC, Joseph S, Aditya S, Karunasekara Y, Board PG, Dulhunty AF, Oakley AJ, Casarotto MG. Structural and biophysical analyses of the skeletal dihydropyridine receptor β subunit β 1a reveal critical roles of domain interactions for stability. J Biol Chem 2017; 292:8401-8411. [PMID: 28351836 DOI: 10.1074/jbc.m116.763896] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2016] [Revised: 03/16/2017] [Indexed: 01/02/2023] Open
Abstract
Excitation-contraction (EC) coupling in skeletal muscle requires a physical interaction between the voltage-gated calcium channel dihydropyridine receptor (DHPR) and the ryanodine receptor Ca2+ release channel. Although the exact molecular mechanism that initiates skeletal EC coupling is unresolved, it is clear that both the α1 and β subunits of DHPR are essential for this process. Here, we employed a series of techniques, including size-exclusion chromatography-multi-angle light scattering, differential scanning fluorimetry, and isothermal calorimetry, to characterize various biophysical properties of the skeletal DHPR β subunit β1a Removal of the intrinsically disordered N and C termini and the hook region of β1a prevented oligomerization, allowing for its structural determination by X-ray crystallography. The structure had a topology similar to that of previously determined β isoforms, which consist of SH3 and guanylate kinase domains. However, transition melting temperatures derived from the differential scanning fluorimetry experiments indicated a significant difference in stability of ∼2-3 °C between the β1a and β2a constructs, and the addition of the DHPR α1s I-II loop (α-interaction domain) peptide stabilized both β isoforms by ∼6-8 °C. Similar to other β isoforms, β1a bound with nanomolar affinity to the α-interaction domain, but binding affinities were influenced by amino acid substitutions in the adjacent SH3 domain. These results suggest that intramolecular interactions between the SH3 and guanylate kinase domains play a role in the stability of β1a while also providing a conduit for allosteric signaling events.
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Affiliation(s)
- Nicole C Norris
- John Curtin School of Medical Research, Australian National University, Canberra, Australian Capital Territory 2601, Australia
| | - Soumya Joseph
- John Curtin School of Medical Research, Australian National University, Canberra, Australian Capital Territory 2601, Australia
| | - Shouvik Aditya
- John Curtin School of Medical Research, Australian National University, Canberra, Australian Capital Territory 2601, Australia
| | - Yamuna Karunasekara
- John Curtin School of Medical Research, Australian National University, Canberra, Australian Capital Territory 2601, Australia
| | - Philip G Board
- John Curtin School of Medical Research, Australian National University, Canberra, Australian Capital Territory 2601, Australia
| | - Angela F Dulhunty
- John Curtin School of Medical Research, Australian National University, Canberra, Australian Capital Territory 2601, Australia
| | - Aaron J Oakley
- Department of Chemistry, University of Wollongong, Wollongong, New South Wales 2522, Australia
| | - Marco G Casarotto
- John Curtin School of Medical Research, Australian National University, Canberra, Australian Capital Territory 2601, Australia.
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15
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Dulhunty AF, Board PG, Beard NA, Casarotto MG. Physiology and Pharmacology of Ryanodine Receptor Calcium Release Channels. ADVANCES IN PHARMACOLOGY 2017; 79:287-324. [DOI: 10.1016/bs.apha.2016.12.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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16
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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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17
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Schrötter K, Dayal A, Grabner M. The mammalian skeletal muscle DHPR has larger Ca 2+ conductance and is phylogenetically ancient to the early ray-finned fish sterlet (Acipenser ruthenus). Cell Calcium 2016; 61:22-31. [PMID: 27793347 PMCID: PMC5538450 DOI: 10.1016/j.ceca.2016.10.002] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2016] [Revised: 10/21/2016] [Accepted: 10/21/2016] [Indexed: 01/01/2023]
Abstract
The L-type Ca2+ channel or dihydropyridine receptor (DHPR) in vertebrate skeletal muscle is responsible for sensing sarcolemmal depolarizations and transducing this signal to the sarcoplasmic Ca2+ release channel RyR1 via conformational coupling to initiate muscle contraction. During this excitation-contraction (EC) coupling process there is a slow Ca2+ current through the mammalian DHPR which is fully missing in euteleost fishes. In contrast to ancestral evolutionary stages where skeletal muscle EC coupling is still depended on Ca2+-induced Ca2+-release (CICR), it is possible that the DHPR Ca2+ conductivity during mammalian (conformational) EC coupling was retained as an evolutionary remnant (vestigiality). Here, we wanted to test the hypothesis that due to the lack of evolutionary pressure in post-CICR species skeletal muscle DHPR Ca2+ conductivity gradually reduced as evolution progressed. Interestingly, we identified that the DHPR of the early ray-finned fish sterlet (Acipenser ruthenus) is phylogenetically positioned above the mammalian rabbit DHPR which retained robust Ca2+ conductivity, but below the euteleost zebrafish DHPR which completely lost Ca2+ conductivity. Remarkably, our results revealed that sterlet DHPR still retained the Ca2+ conductivity but currents are significantly reduced compared to rabbit. This decrease is due to lower DHPR membrane expression similar to zebrafish, as well as due to reduced channel open probability (Po). In both these fish species the lower DHPR expression density is partially compensated by higher efficacy of DHPR-RyR1 coupling. The complete loss of Po in zebrafish and other euteleost species was presumably based on the teleost specific 3rd round of genome duplication (Ts3R). Ts3R headed into the appearance of two skeletal muscle DHPR isoforms which finally, together with the radiation of the euteleost clade, fully lost the Po.
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Affiliation(s)
- Kai Schrötter
- Department of Medical Genetics, Molecular and Clinical Pharmacology, Division of Biochemical Pharmacology, Medical University of Innsbruck, Peter Mayr Strasse 1, A-6020, Innsbruck, Austria
| | - Anamika Dayal
- Department of Medical Genetics, Molecular and Clinical Pharmacology, Division of Biochemical Pharmacology, Medical University of Innsbruck, Peter Mayr Strasse 1, A-6020, Innsbruck, Austria
| | - Manfred Grabner
- Department of Medical Genetics, Molecular and Clinical Pharmacology, Division of Biochemical Pharmacology, Medical University of Innsbruck, Peter Mayr Strasse 1, A-6020, Innsbruck, Austria.
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18
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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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19
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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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20
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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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21
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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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22
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Rebbeck RT, Willemse H, Groom L, Casarotto MG, Board PG, Beard NA, Dirksen RT, Dulhunty AF. Regions of ryanodine receptors that influence activation by the dihydropyridine receptor β1a subunit. Skelet Muscle 2015. [PMID: 26203350 PMCID: PMC4510890 DOI: 10.1186/s13395-015-0049-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Background Although excitation-contraction (EC) coupling in skeletal muscle relies on physical activation of the skeletal ryanodine receptor (RyR1) Ca2+ release channel by dihydropyridine receptors (DHPRs), the activation pathway between the DHPR and RyR1 remains unknown. However, the pathway includes the DHPR β1a subunit which is integral to EC coupling and activates RyR1. In this manuscript, we explore the isoform specificity of β1a activation of RyRs and the β1a binding site on RyR1. Methods We used lipid bilayers to measure single channel currents and whole cell patch clamp to measure L-type Ca2+ currents and Ca2+ transients in myotubes. Results We demonstrate that both skeletal RyR1 and cardiac RyR2 channels in phospholipid bilayers are activated by 10–100 nM of the β1a subunit. Activation of RyR2 by 10 nM β1a was less than that of RyR1, suggesting a reduced affinity of RyR2 for β1a. A reduction in activation was also observed when 10 nM β1a was added to the alternatively spliced (ASI(−)) isoform of RyR1, which lacks ASI residues (A3481-Q3485). It is notable that the equivalent region of RyR2 also lacks four of five ASI residues, suggesting that the absence of these residues may contribute to the reduced 10 nM β1a activation observed for both RyR2 and ASI(−)RyR1 compared to ASI(+)RyR1. We also investigated the influence of a polybasic motif (PBM) of RyR1 (K3495KKRRDGR3502) that is located immediately downstream from the ASI residues and has been implicated in EC coupling. We confirmed that neutralizing the basic residues in the PBM (RyR1 K-Q) results in an ~50 % reduction in Ca2+ transient amplitude following expression in RyR1-null (dyspedic) myotubes and that the PBM is also required for β1a subunit activation of RyR1 channels in lipid bilayers. These results suggest that the removal of β1a subunit interaction with the PBM in RyR1 could contribute directly to ~50 % of the Ca2+ release generated during skeletal EC coupling. Conclusions We conclude that the β1a subunit likely binds to a region that is largely conserved in RyR1 and RyR2 and that this region is influenced by the presence of the ASI residues and the PBM in RyR1. Electronic supplementary material The online version of this article (doi:10.1186/s13395-015-0049-3) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Robyn T Rebbeck
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN USA
| | - Hermia Willemse
- John Curtin School of Medical Research, Australian National University, Canberra, Australian Capital, PO Box 334, Canberra, ACT 2601 Australia
| | - Linda Groom
- 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, Australian Capital, PO Box 334, Canberra, ACT 2601 Australia
| | - Philip G Board
- John Curtin School of Medical Research, Australian National University, Canberra, Australian Capital, PO Box 334, Canberra, ACT 2601 Australia
| | - Nicole A Beard
- Discipline of Biomedical Sciences, Centre for Research in Therapeutic Solutions, University of Canberra, Canberra, ACT 2601 Australia
| | - Robert T Dirksen
- Department of Physiology and Pharmacology, University of Rochester Medical Center, Rochester, NY USA
| | - Angela F Dulhunty
- John Curtin School of Medical Research, Australian National University, Canberra, Australian Capital, PO Box 334, Canberra, ACT 2601 Australia
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23
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Kaur G, Pinggera A, Ortner NJ, Lieb A, Sinnegger-Brauns MJ, Yarov-Yarovoy V, Obermair GJ, Flucher BE, Striessnig J. A Polybasic Plasma Membrane Binding Motif in the I-II Linker Stabilizes Voltage-gated CaV1.2 Calcium Channel Function. J Biol Chem 2015; 290:21086-21100. [PMID: 26100638 PMCID: PMC4543666 DOI: 10.1074/jbc.m115.645671] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2015] [Indexed: 12/27/2022] Open
Abstract
L-type voltage-gated Ca(2+) channels (LTCCs) regulate many physiological functions like muscle contraction, hormone secretion, gene expression, and neuronal excitability. Their activity is strictly controlled by various molecular mechanisms. The pore-forming α1-subunit comprises four repeated domains (I-IV), each connected via an intracellular linker. Here we identified a polybasic plasma membrane binding motif, consisting of four arginines, within the I-II linker of all LTCCs. The primary structure of this motif is similar to polybasic clusters known to interact with polyphosphoinositides identified in other ion channels. We used de novo molecular modeling to predict the conformation of this polybasic motif, immunofluorescence microscopy and live cell imaging to investigate the interaction with the plasma membrane, and electrophysiology to study its role for Cav1.2 channel function. According to our models, this polybasic motif of the I-II linker forms a straight α-helix, with the positive charges facing the lipid phosphates of the inner leaflet of the plasma membrane. Membrane binding of the I-II linker could be reversed after phospholipase C activation, causing polyphosphoinositide breakdown, and was accelerated by elevated intracellular Ca(2+) levels. This indicates the involvement of negatively charged phospholipids in the plasma membrane targeting of the linker. Neutralization of four arginine residues eliminated plasma membrane binding. Patch clamp recordings revealed facilitated opening of Cav1.2 channels containing these mutations, weaker inhibition by phospholipase C activation, and reduced expression of channels (as quantified by ON-gating charge) at the plasma membrane. Our data provide new evidence for a membrane binding motif within the I-II linker of LTCC α1-subunits essential for stabilizing normal Ca(2+) channel function.
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Affiliation(s)
- Gurjot Kaur
- Institute of Pharmacy, Department of Pharmacology and Toxicology, and Center for Molecular Biosciences, University of Innsbruck, A-6020 Innsbruck, Austria
| | - Alexandra Pinggera
- Institute of Pharmacy, Department of Pharmacology and Toxicology, and Center for Molecular Biosciences, University of Innsbruck, A-6020 Innsbruck, Austria
| | - Nadine J Ortner
- Institute of Pharmacy, Department of Pharmacology and Toxicology, and Center for Molecular Biosciences, University of Innsbruck, A-6020 Innsbruck, Austria
| | - Andreas Lieb
- Institute of Pharmacy, Department of Pharmacology and Toxicology, and Center for Molecular Biosciences, University of Innsbruck, A-6020 Innsbruck, Austria
| | - Martina J Sinnegger-Brauns
- Institute of Pharmacy, Department of Pharmacology and Toxicology, and Center for Molecular Biosciences, University of Innsbruck, A-6020 Innsbruck, Austria
| | - Vladimir Yarov-Yarovoy
- Department of Physiology and Membrane Biology, UC Davis School of Medicine, Davis, California 95616
| | - Gerald J Obermair
- Division of Physiology, Medical University of Innsbruck, A-6020 Innsbruck, Austria
| | - Bernhard E Flucher
- Division of Physiology, Medical University of Innsbruck, A-6020 Innsbruck, Austria
| | - Jörg Striessnig
- Institute of Pharmacy, Department of Pharmacology and Toxicology, and Center for Molecular Biosciences, University of Innsbruck, A-6020 Innsbruck, Austria.
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24
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Beqollari D, Romberg CF, Filipova D, Meza U, Papadopoulos S, Bannister RA. Rem uncouples excitation-contraction coupling in adult skeletal muscle fibers. ACTA ACUST UNITED AC 2015; 146:97-108. [PMID: 26078055 PMCID: PMC4485024 DOI: 10.1085/jgp.201411314] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2014] [Accepted: 05/18/2015] [Indexed: 12/14/2022]
Abstract
The RGK protein Rem uncouples the voltage sensors of CaV1.1 from RYR1-mediated sarcoplasmic reticulum Ca2+ release via its ability to interact with the auxiliary β1a subunit. In skeletal muscle, excitation–contraction (EC) coupling requires depolarization-induced conformational rearrangements in L-type Ca2+ channel (CaV1.1) to be communicated to the type 1 ryanodine-sensitive Ca2+ release channel (RYR1) of the sarcoplasmic reticulum (SR) via transient protein–protein interactions. Although the molecular mechanism that underlies conformational coupling between CaV1.1 and RYR1 has been investigated intensely for more than 25 years, the question of whether such signaling occurs via a direct interaction between the principal, voltage-sensing α1S subunit of CaV1.1 and RYR1 or through an intermediary protein persists. A substantial body of evidence supports the idea that the auxiliary β1a subunit of CaV1.1 is a conduit for this intermolecular communication. However, a direct role for β1a has been difficult to test because β1a serves two other functions that are prerequisite for conformational coupling between CaV1.1 and RYR1. Specifically, β1a promotes efficient membrane expression of CaV1.1 and facilitates the tetradic ultrastructural arrangement of CaV1.1 channels within plasma membrane–SR junctions. In this paper, we demonstrate that overexpression of the RGK protein Rem, an established β subunit–interacting protein, in adult mouse flexor digitorum brevis fibers markedly reduces voltage-induced myoplasmic Ca2+ transients without greatly affecting CaV1.1 targeting, intramembrane gating charge movement, or releasable SR Ca2+ store content. In contrast, a β1a-binding–deficient Rem triple mutant (R200A/L227A/H229A) has little effect on myoplasmic Ca2+ release in response to membrane depolarization. Thus, Rem effectively uncouples the voltage sensors of CaV1.1 from RYR1-mediated SR Ca2+ release via its ability to interact with β1a. Our findings reveal Rem-expressing adult muscle as an experimental system that may prove useful in the definition of the precise role of the β1a subunit in skeletal-type EC coupling.
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Affiliation(s)
- Donald Beqollari
- Department of Medicine-Cardiology Division, University of Colorado Denver-Anschutz Medical Campus, Aurora, CO 80045
| | - Christin F Romberg
- Department of Medicine-Cardiology Division, University of Colorado Denver-Anschutz Medical Campus, Aurora, CO 80045
| | - Dilyana Filipova
- Institute of Vegetative Physiology, University Hospital of Köln, D-50931 Köln, Germany
| | - Ulises Meza
- Department of Medicine-Cardiology Division, University of Colorado Denver-Anschutz Medical Campus, Aurora, CO 80045 Departamento de Fisiología y Biofísica, Facultad de Medicina, Universidad Autónoma de San Luis Potosí, 78210 San Luis Potosí, Mexico
| | - Symeon Papadopoulos
- Institute of Vegetative Physiology, University Hospital of Köln, D-50931 Köln, Germany
| | - Roger A Bannister
- Department of Medicine-Cardiology Division, University of Colorado Denver-Anschutz Medical Campus, Aurora, CO 80045
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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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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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Hernández-Ochoa EO, Olojo RO, Rebbeck RT, Dulhunty AF, Schneider MF. β1a490-508, a 19-residue peptide from C-terminal tail of Cav1.1 β1a subunit, potentiates voltage-dependent calcium release in adult skeletal muscle fibers. Biophys J 2014; 106:535-47. [PMID: 24507594 DOI: 10.1016/j.bpj.2013.11.4503] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2013] [Revised: 11/11/2013] [Accepted: 11/13/2013] [Indexed: 10/25/2022] Open
Abstract
The α1 and β1a subunits of the skeletal muscle calcium channel, Cav1.1, as well as the Ca(2+) release channel, ryanodine receptor (RyR1), are essential for excitation-contraction coupling. RyR1 channel activity is modulated by the β1a subunit and this effect can be mimicked by a peptide (β1a490-524) corresponding to the 35-residue C-terminal tail of the β1a subunit. Protein-protein interaction assays confirmed a high-affinity interaction between the C-terminal tail of the β1a and RyR1. Based on previous results using overlapping peptides tested on isolated RyR1, we hypothesized that a 19-amino-acid residue peptide (β1a490-508) is sufficient to reproduce activating effects of β1a490-524. Here we examined the effects of β1a490-508 on Ca(2+) release and Ca(2+) currents in adult skeletal muscle fibers subjected to voltage-clamp and on RyR1 channel activity after incorporating sarcoplasmic reticulum vesicles into lipid bilayers. β1a490-508 (25 nM) increased the peak Ca(2+) release flux by 49% in muscle fibers. Considerably fewer activating effects were observed using 6.25, 100, and 400 nM of β1a490-508 in fibers. β1a490-508 also increased RyR1 channel activity in bilayers and Cav1.1 currents in fibers. A scrambled form of β1a490-508 peptide was used as negative control and produced negligible effects on Ca(2+) release flux and RyR1 activity. Our results show that the β1a490-508 peptide contains molecular components sufficient to modulate excitation-contraction coupling in adult muscle fibers.
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Affiliation(s)
- Erick O Hernández-Ochoa
- Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, Baltimore, Maryland
| | - Rotimi O Olojo
- Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, Baltimore, Maryland
| | - Robyn T Rebbeck
- John Curtin School of Medical Research, Australian National University, Canberra, Australia
| | - Angela F Dulhunty
- John Curtin School of Medical Research, Australian National University, Canberra, Australia
| | - Martin F Schneider
- Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, Baltimore, Maryland.
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Editors T. CIR-Myo News: Proceedings of the 2014 Spring Padua Muscle Days: Terme Euganee and Padova (Italy), April 3-5, 2014. Eur J Transl Myol 2014; 24:3299. [PMID: 26913130 PMCID: PMC4749006 DOI: 10.4081/ejtm.2014.3299] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Not available.
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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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