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Sampieri A, Padilla-Flores T, Thawani AR, Lam PY, Fuchter MJ, Peterson R, Vaca L. The conducting state of TRPA1 modulates channel lateral mobility. Cell Calcium 2023; 116:102800. [PMID: 37776645 DOI: 10.1016/j.ceca.2023.102800] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2023] [Revised: 09/04/2023] [Accepted: 09/16/2023] [Indexed: 10/02/2023]
Abstract
We have studied Danio rerio (Zebrafish) TRPA1 channel using a method that combines single channel electrophysiological and optical recordings to evaluate lateral mobility and channel gating simultaneously in single channels. TRPA1 channel activation by two distinct chemical ligands: allyl isothiocyanate (AITC) and TRPswitch B, results in substantial reduction of channel lateral mobility at the plasma membrane. Incubation with the cholesterol sequestering agent methyl-β-cyclodextrin (MβCD), prevents the reduction on lateral mobility induced by the two chemical agonists. This results strongly suggest that the open conformation of TRPA1 modulates channel lateral mobility probably by facilitating the insertion of the channel into cholesterol-enriched domains at the plasma membrane.
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Affiliation(s)
- Alicia Sampieri
- Instituto de Fisiología Celular. Departamento de Biología Celular y del desarrollo. Universidad Nacional Autónoma de México. México, CDMX 04510, Mexico
| | - Teresa Padilla-Flores
- Instituto de Fisiología Celular. Departamento de Biología Celular y del desarrollo. Universidad Nacional Autónoma de México. México, CDMX 04510, Mexico
| | - Aditya R Thawani
- Department of Chemistry, Molecular Sciences Research Hub, Imperial College London, White City Campus, London W12 OBZ, United Kingdom
| | - Pui-Ying Lam
- Department of Cell Biology, Neurobiology and Anatomy, Medical College of Wisconsin, 8701 West Watertown Plank Rd., Milwaukee, Wisconsin 53226, USA; Neuroscience Research Center, Medical College of Wisconsin, 8701 West Watertown Plank Rd., Milwaukee, Wisconsin, 53226, USA
| | - Matthew J Fuchter
- Department of Chemistry, Molecular Sciences Research Hub, Imperial College London, White City Campus, London W12 OBZ, United Kingdom
| | - Randall Peterson
- College of Pharmacy, University of Utah, 30 South 2000 East, Salt Lake City, Utah, 84112, USA
| | - Luis Vaca
- Instituto de Fisiología Celular. Departamento de Biología Celular y del desarrollo. Universidad Nacional Autónoma de México. México, CDMX 04510, Mexico.
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2
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Wang YX, Reyes-García J, Di Mise A, Zheng YM. Role of ryanodine receptor 2 and FK506-binding protein 12.6 dissociation in pulmonary hypertension. J Gen Physiol 2023; 155:213798. [PMID: 36625865 PMCID: PMC9836826 DOI: 10.1085/jgp.202213100] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2022] [Revised: 07/29/2022] [Accepted: 12/19/2022] [Indexed: 01/11/2023] Open
Abstract
Pulmonary hypertension (PH) is a devastating disease characterized by a progressive increase in pulmonary arterial pressure leading to right ventricular failure and death. A major cellular response in this disease is the contraction of smooth muscle cells (SMCs) of the pulmonary vasculature. Cell contraction is determined by the increase in intracellular Ca2+ concentration ([Ca2+]i), which is generated and regulated by various ion channels. Several studies by us and others have shown that ryanodine receptor 2 (RyR2), a Ca2+-releasing channel in the sarcoplasmic reticulum (SR), is an essential ion channel for the control of [Ca2+]i in pulmonary artery SMCs (PASMCs), thereby mediating the sustained vasoconstriction seen in PH. FK506-binding protein 12.6 (FKBP12.6) strongly associates with RyR2 to stabilize its functional activity. FKBP12.6 can be dissociated from RyR2 by a hypoxic stimulus to increase channel function and Ca2+ release, leading to pulmonary vasoconstriction and PH. More specifically, dissociation of the RyR2-FKBP12.6 complex is a consequence of increased mitochondrial ROS generation mediated by the Rieske iron-sulfur protein (RISP) at the mitochondrial complex III after hypoxia. Overall, RyR2/FKBP12.6 dissociation and the corresponding signaling pathway may be an important factor in the development of PH. Novel drugs and biologics targeting RyR2, FKBP12.6, and related molecules may become unique effective therapeutics for PH.
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Affiliation(s)
- Yong-Xiao Wang
- Department of Molecular and Cellular Physiology, Albany Medical College, Albany, NY, USA,Correspondence to Yong-Xiao Wang:
| | - Jorge Reyes-García
- Department of Molecular and Cellular Physiology, Albany Medical College, Albany, NY, USA,Departamento de Farmacología, Facultad de Medicina, Universidad Nacional Autónoma de México,Ciudad de México, México
| | - Annarita Di Mise
- Department of Molecular and Cellular Physiology, Albany Medical College, Albany, NY, USA,Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari, Bari, Italy
| | - Yun-Min Zheng
- Department of Molecular and Cellular Physiology, Albany Medical College, Albany, NY, USA,Yun-Min Zheng:
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Bolaños P, Calderón JC. Excitation-contraction coupling in mammalian skeletal muscle: Blending old and last-decade research. Front Physiol 2022; 13:989796. [PMID: 36117698 PMCID: PMC9478590 DOI: 10.3389/fphys.2022.989796] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2022] [Accepted: 08/08/2022] [Indexed: 11/13/2022] Open
Abstract
The excitation–contraction coupling (ECC) in skeletal muscle refers to the Ca2+-mediated link between the membrane excitation and the mechanical contraction. The initiation and propagation of an action potential through the membranous system of the sarcolemma and the tubular network lead to the activation of the Ca2+-release units (CRU): tightly coupled dihydropyridine and ryanodine (RyR) receptors. The RyR gating allows a rapid, massive, and highly regulated release of Ca2+ from the sarcoplasmic reticulum (SR). The release from triadic places generates a sarcomeric gradient of Ca2+ concentrations ([Ca2+]) depending on the distance of a subcellular region from the CRU. Upon release, the diffusing Ca2+ has multiple fates: binds to troponin C thus activating the contractile machinery, binds to classical sarcoplasmic Ca2+ buffers such as parvalbumin, adenosine triphosphate and, experimentally, fluorescent dyes, enters the mitochondria and the SR, or is recycled through the Na+/Ca2+ exchanger and store-operated Ca2+ entry (SOCE) mechanisms. To commemorate the 7th decade after being coined, we comprehensively and critically reviewed “old”, historical landmarks and well-established concepts, and blended them with recent advances to have a complete, quantitative-focused landscape of the ECC. We discuss the: 1) elucidation of the CRU structures at near-atomic resolution and its implications for functional coupling; 2) reliable quantification of peak sarcoplasmic [Ca2+] using fast, low affinity Ca2+ dyes and the relative contributions of the Ca2+-binding mechanisms to the whole concert of Ca2+ fluxes inside the fibre; 3) articulation of this novel quantitative information with the unveiled structural details of the molecular machinery involved in mitochondrial Ca2+ handing to understand how and how much Ca2+ enters the mitochondria; 4) presence of the SOCE machinery and its different modes of activation, which awaits understanding of its magnitude and relevance in situ; 5) pharmacology of the ECC, and 6) emerging topics such as the use and potential applications of super-resolution and induced pluripotent stem cells (iPSC) in ECC. Blending the old with the new works better!
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Affiliation(s)
- Pura Bolaños
- Laboratory of Cellular Physiology, Centre of Biophysics and Biochemistry, Venezuelan Institute for Scientific Research (IVIC), Caracas, Venezuela
| | - Juan C. Calderón
- Physiology and Biochemistry Research Group-PHYSIS, Faculty of Medicine, University of Antioquia, Medellín, Colombia
- *Correspondence: Juan C. Calderón,
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Lilliu E, Koenig S, Koenig X, Frieden M. Store-Operated Calcium Entry in Skeletal Muscle: What Makes It Different? Cells 2021; 10:cells10092356. [PMID: 34572005 PMCID: PMC8468011 DOI: 10.3390/cells10092356] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2021] [Revised: 09/03/2021] [Accepted: 09/04/2021] [Indexed: 01/26/2023] Open
Abstract
Current knowledge on store-operated Ca2+ entry (SOCE) regarding its localization, kinetics, and regulation is mostly derived from studies performed in non-excitable cells. After a long time of relative disinterest in skeletal muscle SOCE, this mechanism is now recognized as an essential contributor to muscle physiology, as highlighted by the muscle pathologies that are associated with mutations in the SOCE molecules STIM1 and Orai1. This review mainly focuses on the peculiar aspects of skeletal muscle SOCE that differentiate it from its counterpart found in non-excitable cells. This includes questions about SOCE localization and the movement of respective proteins in the highly organized skeletal muscle fibers, as well as the diversity of expressed STIM isoforms and their differential expression between muscle fiber types. The emerging evidence of a phasic SOCE, which is activated during EC coupling, and its physiological implication is described as well. The specific issues related to the use of SOCE modulators in skeletal muscles are discussed. This review highlights the complexity of SOCE activation and its regulation in skeletal muscle, with an emphasis on the most recent findings and the aim to reach a current picture of this mesmerizing phenomenon.
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Affiliation(s)
- Elena Lilliu
- Center for Physiology and Pharmacology, Department of Neurophysiology and Pharmacology, Medical University of Vienna, 1090 Vienna, Austria;
| | - Stéphane Koenig
- Department of Cell Physiology and Metabolism, University of Geneva, 1201 Geneva, Switzerland;
| | - Xaver Koenig
- Center for Physiology and Pharmacology, Department of Neurophysiology and Pharmacology, Medical University of Vienna, 1090 Vienna, Austria;
- Correspondence: (X.K.); (M.F.)
| | - Maud Frieden
- Department of Cell Physiology and Metabolism, University of Geneva, 1201 Geneva, Switzerland;
- Correspondence: (X.K.); (M.F.)
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Choi JH, Jeong SY, Oh MR, Allen PD, Lee EH. TRPCs: Influential Mediators in Skeletal Muscle. Cells 2020; 9:cells9040850. [PMID: 32244622 PMCID: PMC7226745 DOI: 10.3390/cells9040850] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2020] [Revised: 03/31/2020] [Accepted: 03/31/2020] [Indexed: 02/07/2023] Open
Abstract
Ca2+ itself or Ca2+-dependent signaling pathways play fundamental roles in various cellular processes from cell growth to death. The most representative example can be found in skeletal muscle cells where a well-timed and adequate supply of Ca2+ is required for coordinated Ca2+-dependent skeletal muscle functions, such as the interactions of contractile proteins during contraction. Intracellular Ca2+ movements between the cytosol and sarcoplasmic reticulum (SR) are strictly regulated to maintain the appropriate Ca2+ supply in skeletal muscle cells. Added to intracellular Ca2+ movements, the contribution of extracellular Ca2+ entry to skeletal muscle functions and its significance have been continuously studied since the early 1990s. Here, studies on the roles of channel proteins that mediate extracellular Ca2+ entry into skeletal muscle cells using skeletal myoblasts, myotubes, fibers, tissue, or skeletal muscle-originated cell lines are reviewed with special attention to the proposed functions of transient receptor potential canonical proteins (TRPCs) as store-operated Ca2+ entry (SOCE) channels under normal conditions and the potential abnormal properties of TRPCs in muscle diseases such as Duchenne muscular dystrophy (DMD).
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Affiliation(s)
- Jun Hee Choi
- Department of Physiology, College of Medicine, The Catholic University of Korea, Seoul 06591, Korea
- Department of Biomedicine & Health Sciences, Graduate School, The Catholic University of Korea, Seoul 06591, Korea
| | - Seung Yeon Jeong
- Department of Physiology, College of Medicine, The Catholic University of Korea, Seoul 06591, Korea
- Department of Biomedicine & Health Sciences, Graduate School, The Catholic University of Korea, Seoul 06591, Korea
| | - Mi Ri Oh
- Department of Physiology, College of Medicine, The Catholic University of Korea, Seoul 06591, Korea
- Department of Biomedicine & Health Sciences, Graduate School, The Catholic University of Korea, Seoul 06591, Korea
| | - Paul D. Allen
- Leeds Institute of Biomedical & Clinical Sciences, St. James’s University Hospital, University of Leeds, Leeds LS97TF, UK
| | - Eun Hui Lee
- Department of Physiology, College of Medicine, The Catholic University of Korea, Seoul 06591, Korea
- Department of Biomedicine & Health Sciences, Graduate School, The Catholic University of Korea, Seoul 06591, Korea
- Correspondence: ; Tel.: +82-2-2258-7279
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Secondo A, Petrozziello T, Tedeschi V, Boscia F, Vinciguerra A, Ciccone R, Pannaccione A, Molinaro P, Pignataro G, Annunziato L. ORAI1/STIM1 Interaction Intervenes in Stroke and in Neuroprotection Induced by Ischemic Preconditioning Through Store-Operated Calcium Entry. Stroke 2019; 50:1240-1249. [DOI: 10.1161/strokeaha.118.024115] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Affiliation(s)
- Agnese Secondo
- From the Division of Pharmacology, Department of Neuroscience, Reproductive and Odontostomatological Sciences, School of Medicine, Federico II University of Naples, Italy (A.S., T.P., V.T., F.B., A.V., R.C., A.P., P.M., G.P.)
| | - Tiziana Petrozziello
- From the Division of Pharmacology, Department of Neuroscience, Reproductive and Odontostomatological Sciences, School of Medicine, Federico II University of Naples, Italy (A.S., T.P., V.T., F.B., A.V., R.C., A.P., P.M., G.P.)
| | - Valentina Tedeschi
- From the Division of Pharmacology, Department of Neuroscience, Reproductive and Odontostomatological Sciences, School of Medicine, Federico II University of Naples, Italy (A.S., T.P., V.T., F.B., A.V., R.C., A.P., P.M., G.P.)
| | - Francesca Boscia
- From the Division of Pharmacology, Department of Neuroscience, Reproductive and Odontostomatological Sciences, School of Medicine, Federico II University of Naples, Italy (A.S., T.P., V.T., F.B., A.V., R.C., A.P., P.M., G.P.)
| | - Antonio Vinciguerra
- From the Division of Pharmacology, Department of Neuroscience, Reproductive and Odontostomatological Sciences, School of Medicine, Federico II University of Naples, Italy (A.S., T.P., V.T., F.B., A.V., R.C., A.P., P.M., G.P.)
| | - Roselia Ciccone
- From the Division of Pharmacology, Department of Neuroscience, Reproductive and Odontostomatological Sciences, School of Medicine, Federico II University of Naples, Italy (A.S., T.P., V.T., F.B., A.V., R.C., A.P., P.M., G.P.)
| | - Anna Pannaccione
- From the Division of Pharmacology, Department of Neuroscience, Reproductive and Odontostomatological Sciences, School of Medicine, Federico II University of Naples, Italy (A.S., T.P., V.T., F.B., A.V., R.C., A.P., P.M., G.P.)
| | - Pasquale Molinaro
- From the Division of Pharmacology, Department of Neuroscience, Reproductive and Odontostomatological Sciences, School of Medicine, Federico II University of Naples, Italy (A.S., T.P., V.T., F.B., A.V., R.C., A.P., P.M., G.P.)
| | - Giuseppe Pignataro
- From the Division of Pharmacology, Department of Neuroscience, Reproductive and Odontostomatological Sciences, School of Medicine, Federico II University of Naples, Italy (A.S., T.P., V.T., F.B., A.V., R.C., A.P., P.M., G.P.)
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Kim J, Lee J, Kim S, Ryu HY, Cha KS, Sung DJ. Exercise-induced rhabdomyolysis mechanisms and prevention: A literature review. JOURNAL OF SPORT AND HEALTH SCIENCE 2016; 5:324-333. [PMID: 30356493 PMCID: PMC6188610 DOI: 10.1016/j.jshs.2015.01.012] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/28/2014] [Revised: 10/26/2014] [Accepted: 01/26/2015] [Indexed: 05/27/2023]
Abstract
Exercise-induced rhabdomyolysis (exRML), a pathophysiological condition of skeletal muscle cell damage that may cause acute renal failure and in some cases death. Increased Ca2+ level in cells along with functional degradation of cell signaling system and cell matrix have been suggested as the major pathological mechanisms associated with exRML. The onset of exRML may be exhibited in athletes as well as in general population. Previous studies have reported that possible causes of exRML were associated with excessive eccentric contractions in high temperature, abnormal electrolytes balance, and nutritional deficiencies possible genetic defects. However, the underlying mechanisms of exRML have not been clearly established among health professionals or sports medicine personnel. Therefore, we reviewed the possible mechanisms and correlated prevention of exRML, while providing useful and practical information for the athlete and general exercising population.
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Affiliation(s)
- Jooyoung Kim
- Health and Rehabilitation Major, College of Physical Education, Kookmin University, Seoul 136-702, Republic of Korea
| | - Joohyung Lee
- Health and Rehabilitation Major, College of Physical Education, Kookmin University, Seoul 136-702, Republic of Korea
| | - Sojung Kim
- Department of Physical Education, Global Campus, Kyung Hee University, Suwon 446-701, Republic of Korea
| | - Ho Young Ryu
- Division of Sport Science, College of Science and Technology, Konkuk University, Choong-Ju 380-702, Republic of Korea
| | - Kwang Suk Cha
- Division of Sport Science, College of Science and Technology, Konkuk University, Choong-Ju 380-702, Republic of Korea
| | - Dong Jun Sung
- Division of Sport Science, College of Science and Technology, Konkuk University, Choong-Ju 380-702, Republic of Korea
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Lin AHY, Sun H, Paudel O, Lin MJ, Sham JSK. Conformation of ryanodine receptor-2 gates store-operated calcium entry in rat pulmonary arterial myocytes. Cardiovasc Res 2016; 111:94-104. [PMID: 27013634 DOI: 10.1093/cvr/cvw067] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/28/2015] [Accepted: 03/18/2016] [Indexed: 12/31/2022] Open
Abstract
AIMS Store-operated Ca(2+) entry (SOCE) contributes to a multitude of physiological and pathophysiological functions in pulmonary vasculatures. SOCE attributable to inositol 1,4,5-trisphosphate receptor (InsP3R)-gated Ca(2+) store has been studied extensively, but the role of ryanodine receptor (RyR)-gated store in SOCE remains unclear. The present study aims to delineate the relationship between RyR-gated Ca(2+) stores and SOCE, and characterize the properties of RyR-gated Ca(2+) entry in pulmonary artery smooth muscle cells (PASMCs). METHODS AND RESULTS PASMCs were isolated from intralobar pulmonary arteries of male Wister rats. Application of the RyR1/2 agonist 4-chloro-m-cresol (4-CmC) activated robust Ca(2+) entry in PASMCs. It was blocked by Gd(3+) and the RyR2 modulator K201 but was unaffected by the RyR1/3 antagonist dantrolene and the InsP3R inhibitor xestospongin C, suggesting RyR2 is mainly involved in the process. siRNA knockdown of STIM1, TRPC1, and Orai1, or interruption of STIM1 translocation with ML-9 significantly attenuated the 4-CmC-induced SOCE, similar to SOCE induced by thapsigargin. However, depletion of RyR-gated store with caffeine failed to activate Ca(2+) entry. Inclusion of ryanodine, which itself did not cause Ca(2+) entry, uncovered caffeine-induced SOCE in a concentration-dependent manner, suggesting binding of ryanodine to RyR is permissive for the process. This Ca(2+) entry had the same molecular and pharmacological properties of 4-CmC-induced SOCE, and it persisted once activated even after caffeine washout. Measurement of Ca(2+) in sarcoplasmic reticulum (SR) showed that 4-CmC and caffeine application with or without ryanodine reduced SR Ca(2+) to similar extent, suggesting store-depletion was not the cause of the discrepancy. Moreover, caffeine/ryanodine and 4-CmC failed to initiate SOCE in cells transfected with the ryanodine-binding deficient mutant RyR2-I4827T. CONCLUSIONS RyR2-gated Ca(2+) store contributes to SOCE in PASMCs; however, store-depletion alone is insufficient but requires a specific RyR conformation modifiable by ryanodine binding to activate Ca(2+) entry.
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Affiliation(s)
- Amanda H Y Lin
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Johns Hopkins University School of Medicine, 5501 Hopkins Bayview Circle, Baltimore, MD 21224, USA
| | - Hui Sun
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Johns Hopkins University School of Medicine, 5501 Hopkins Bayview Circle, Baltimore, MD 21224, USA
| | - Omkar Paudel
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Johns Hopkins University School of Medicine, 5501 Hopkins Bayview Circle, Baltimore, MD 21224, USA
| | - Mo-Jun Lin
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Johns Hopkins University School of Medicine, 5501 Hopkins Bayview Circle, Baltimore, MD 21224, USA Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Fujian Medical University, Fuzhou, China
| | - James S K Sham
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Johns Hopkins University School of Medicine, 5501 Hopkins Bayview Circle, Baltimore, MD 21224, USA
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Bolaños P, Guillen A, Gámez A, Caputo C. Quantifying SOCE fluorescence measurements in mammalian muscle fibres. The effects of ryanodine and osmotic shocks. J Muscle Res Cell Motil 2013; 34:379-93. [PMID: 24129906 DOI: 10.1007/s10974-013-9360-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2013] [Accepted: 09/18/2013] [Indexed: 11/28/2022]
Abstract
We have quantified Ca(2+) entry through store operated calcium channels in mice muscle fibres, measuring the rates of change of myoplasmic [Ca(2+)], d[Ca(2+)](myo)/dt, and of Ca(2+) removal, d[Ca(2+)](Removal)/dt, turning store operated calcium entry (SOCE) ON, and OFF, by switching on or off external Ca(2+). In depleted fibres, poisoned with 10 μM cyclopiazonic acid SOCE influx was about 3 μM/s. Ryanodine (50 μM) caused a robust, nifedipine (50 μM) independent, increase in SOCE activation to 8.6 μM/s. Decreasing medium osmolarity from 300 to 220 mOsm/L, decreased SOCE to 0.9 μM/s, while increasing osmolarity from 220 to 400 mOsm/L potentiated SOCE to 43.6 μM/s. Ryanodine inhibited the effects of hypotonicity. Experiments using 2-aminoethoxydiphenyl borate, nifedipine, or Mn(2+) quenching, strongly suggest that the increased [Ca(2+)](myo) by ryanodine or hypertonic shock is mediated by potentiated SOCE activation. The Ca(2+) response decay, quantified by d[Ca(2+)](Removal)/dt, indicates a robust residual Ca(2+) removal mechanism in sarco-endoplasmic reticulum calcium ATPase poisoned fibres. SOCE high sensitivity to osmotic shocks, or to ryanodine receptor (RyR) binding, suggests its high dependency on the structural relationship between its molecular constituents, Orai1 and stromal interaction molecule and the sarcoplasmic reticulum and plasma membranes, in the triadic junctional region, where RyRs, are conspicuously present. This study demonstrates that SOCE machinery is highly sensitive to structural changes caused by binding of an agonist to its receptor or by imposed osmotical volume changes.
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Affiliation(s)
- Pura Bolaños
- Laboratorio de Fisiología Celular, Centro de Biofísica y Bioquímica, Instituto Venezolano de Investigaciones Científicas (IVIC), Caracas, Venezuela,
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10
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Gailly P. TRP channels in normal and dystrophic skeletal muscle. Curr Opin Pharmacol 2012; 12:326-34. [PMID: 22349418 DOI: 10.1016/j.coph.2012.01.018] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2011] [Revised: 01/31/2012] [Accepted: 01/31/2012] [Indexed: 01/29/2023]
Abstract
TRP proteins constitute non-selective cation-permeable ion channels, most of which are permeable to Ca²⁺. In skeletal muscle, several isoforms of the TRPC (Canonical), TRPV (Vanilloid) and TRPM (Melastatin) subfamilies are expressed. In particular, TRPC1, C3 and C6, TRPV2 and V4, TRPM4 and TRPM7 have been consistently found in cultured myoblasts or in adult muscles. These channels seem to directly or indirectly respond to membrane stretch or to Ca²⁺ stores depletion; some isoforms might also constitute unregulated Ca²⁺ leak channels. Their function is largely unknown. TRPC1 and C3 have been involved in muscle development, in particular in myoblasts migration and differentiation. TRPC1 and V4 might allow a basal influx of Ca²⁺ at rest. Their lack has consequences on muscle fatigue. TRPV2 seems to be stretch-sensitive. It localizes mainly in intracellular pools at rest, and translocates to the plasma membrane upon IGF-1 stimulation. TRP channels seem to be involved in the pathophysiology of muscle disorders. In particular in Duchenne muscular dystrophy, the lack of the cytoskeletal protein dystrophin induces a disregulation of several ion channels leading to an abnormal influx of Ca²⁺. We discuss here, the possible involvement of TRP channels in this abnormal influx of Ca²⁺.
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Affiliation(s)
- Philippe Gailly
- Laboratory of Cell Physiology, Institute of Neuroscience, Université catholique de Louvain, 55 av. Hippocrate, B1.55.12, 1200 Brussels, Belgium.
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Silswal N, Parelkar NK, Wacker MJ, Brotto M, Andresen J. Phosphatidylinositol 3,5-bisphosphate increases intracellular free Ca2+ in arterial smooth muscle cells and elicits vasocontraction. Am J Physiol Heart Circ Physiol 2011; 300:H2016-26. [PMID: 21421826 DOI: 10.1152/ajpheart.01011.2010] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Phosphoinositide (3,5)-bisphosphate [PI(3,5)P(2)] is a newly identified phosphoinositide that modulates intracellular Ca(2+) by activating ryanodine receptors (RyRs). Since the contractile state of arterial smooth muscle depends on the concentration of intracellular Ca(2+), we hypothesized that by mobilizing sarcoplasmic reticulum (SR) Ca(2+) stores PI(3,5)P(2) would increase intracellular Ca(2+) in arterial smooth muscle cells and cause vasocontraction. Using immunohistochemistry, we found that PI(3,5)P(2) was present in the mouse aorta and that exogenously applied PI(3,5)P(2) readily entered aortic smooth muscle cells. In isolated aortic smooth muscle cells, exogenous PI(3,5)P(2) elevated intracellular Ca(2+), and it also contracted aortic rings. Both the rise in intracellular Ca(2+) and the contraction caused by PI(3,5)P(2) were prevented by antagonizing RyRs, while the majority of the PI(3,5)P(2) response was intact after blockade of inositol (1,4,5)-trisphosphate receptors. Depletion of SR Ca(2+) stores with thapsigargin or caffeine and/or ryanodine blunted the Ca(2+) response and greatly attenuated the contraction elicited by PI(3,5)P(2). The removal of extracellular Ca(2+) or addition of verapamil to inhibit voltage-dependent Ca(2+) channels reduced but did not eliminate the Ca(2+) or contractile responses to PI(3,5)P(2). We also found that PI(3,5)P(2) depolarized aortic smooth muscle cells and that LaCl(3) inhibited those aspects of the PI(3,5)P(2) response attributable to extracellular Ca(2+). Thus, full and sustained aortic contractions to PI(3,5)P(2) required the release of SR Ca(2+), probably via the activation of RyR, and also extracellular Ca(2+) entry via voltage-dependent Ca(2+) channels.
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Affiliation(s)
- Neerupma Silswal
- Basic Medical Science Dept., Muscle Biology Research Group, School of Medicine, Univ. of Missouri, Kansas City, MO 64108, USA
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Woo JS, Cho CH, Kim DH, Lee EH. TRPC3 cation channel plays an important role in proliferation and differentiation of skeletal muscle myoblasts. Exp Mol Med 2011; 42:614-27. [PMID: 20644344 DOI: 10.3858/emm.2010.42.9.061] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
During membrane depolarization associated with skeletal excitation-contraction (EC) coupling, dihydropyridine receptor [DHPR, a L-type Ca(2+) channel in the transverse (t)-tubule membrane] undergoes conformational changes that are transmitted to ryanodine receptor 1 [RyR1, an internal Ca(2+)-release channel in the sarcoplasmic reticulum (SR) membrane] causing Ca(2+) release from the SR. Canonical-type transient receptor potential cation channel 3 (TRPC3), an extracellular Ca(2+)-entry channel in the t-tubule and plasma membrane, is required for full-gain of skeletal EC coupling. To examine additional role(s) for TRPC3 in skeletal muscle other than mediation of EC coupling, in the present study, we created a stable myoblast line with reduced TRPC3 expression and without alpha1((S))DHPR (MDG/TRPC3 KD myoblast) by knock-down of TRPC3 in alpha1((S))DHPR-null muscular dysgenic (MDG) myoblasts using retrovirus-delivered small interference RNAs in order to eliminate any DHPR-associated EC coupling-related events. Unlike wild-type or alpha1((S))DHPR-null MDG myoblasts, MDG/TRPC3 KD myoblasts exhibited dramatic changes in cellular morphology (e.g., unusual expansion of both cell volume and the plasma membrane, and multi-nuclei) and failed to differentiate into myotubes possibly due to increased Ca(2+) content in the SR. These results suggest that TRPC3 plays an important role in the maintenance of skeletal muscle myoblasts and myotubes.
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Affiliation(s)
- Jin Seok Woo
- Department of Physiology, College of Medicine, The Catholic University of Korea, Seoul 137-701, Korea
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13
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Lee EH. Ca2+ channels and skeletal muscle diseases. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2010; 103:35-43. [DOI: 10.1016/j.pbiomolbio.2010.05.003] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/21/2009] [Revised: 03/09/2010] [Accepted: 05/19/2010] [Indexed: 11/29/2022]
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14
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Homer and the ryanodine receptor. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2009; 39:91-102. [PMID: 19513708 DOI: 10.1007/s00249-009-0494-1] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/23/2009] [Revised: 05/15/2009] [Accepted: 05/18/2009] [Indexed: 10/20/2022]
Abstract
Homer proteins have recently been identified as novel high-affinity ligands that modulate ryanodine receptor (RyR) Ca(2+) release channels in heart and skeletal muscle, through an EVH1 domain which binds to proline-rich regions in target proteins. Many Homer proteins can also self-associate through a coiled-coil domain that allows their multimerisation. In other tissues, especially neurons, Homer anchors proteins embedded in the surface membrane to the Ca(2+) release channel in the endoplasmic reticulum and can anchor membrane or cytosolic proteins to the cytoskeleton. Although this anchoring aspect of Homer function has not been extensively investigated in muscle, there are consensus sequences for Homer binding in the RyR and on many of the proteins that it interacts with in the massive RyR ion channel complex. In this review we explore the potential of Homer to contribute to a variety of cell processes in muscle and neurons that also involve RyR channels.
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15
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Abstract
Malignant hyperthermia (MH) is a pharmacogenetic disorder triggered by volatile anesthetics or depolarizing muscle relaxants in predisposed individuals. Exercise or stress-induced MH episodes, in the absence of any obvious pharmacological trigger, have been reported, but these are rare. A considerable effort has taken place over the last two decades to identify mutations associated with MH and characterize their functional effects. A number of different, but complementary systems, have been developed and implemented to this end. The results of such studies have identified commonalities in functional affects of mutations, and also uncovered unexpected complexities in both the structure and function of the skeletal muscle calcium-release channel. The following review is an attempt to provide a summary of the background to current MH research, and highlight some recent advances in our knowledge of the molecular basis of the phenotypic expression of this disorder.
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Affiliation(s)
- Kathryn M Stowell
- Institute of Molecular Biosciences, Massey University, Palmerston North, New Zealand.
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16
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Lyfenko AD, Dirksen RT. Differential dependence of store-operated and excitation-coupled Ca2+ entry in skeletal muscle on STIM1 and Orai1. J Physiol 2008; 586:4815-24. [PMID: 18772199 DOI: 10.1113/jphysiol.2008.160481] [Citation(s) in RCA: 134] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
In non-excitable cells, agonist-induced depletion of intracellular Ca(2+) stores triggers Ca(2+) influx via a process termed store-operated Ca(2+) entry (SOCE). In T-lymphocytes, stromal interaction molecule 1 (STIM1) acts as the intra-store Ca(2+) sensor and Orai1 functions as the Ca(2+)-permeable SOCE channel activated by STIM1 following store depletion. Two functionally distinct Ca(2+) entry pathways exist in skeletal muscle; one activated by store depletion (SOCE) and a second by sustained/repetitive depolarization that does not require store depletion (excitation-coupled Ca(2+) entry, ECCE). However, the role of STIM1 and Orai1 in coordinating SOCE and ECCE activity in skeletal muscle and whether these two Ca(2+) entry pathways represent distinct molecular entities or two different activation mechanisms of the same channel complex is unknown. Here we address these issues using siRNA-mediated STIM1 knockdown, dominant-negative Orai1, and permeation-defective Orai1 to determine the role of STIM1 and Orai1 in store-operated and excitation-coupled Ca(2+) entry in skeletal myotubes. SOCE and ECCE activity were quantified from both intracellular Ca(2+) measurements and Mn(2+) quench assays. We found that STIM1 siRNA reduced STIM1 protein by more than 90% and abolished SOCE activity, while expression of siRNA-resistant hSTIM1 fully restored SOCE. SOCE was also abolished by dominant-negative Orai1 (E106Q) and markedly reduced by expression of a permeation-defective Orai1 (E190Q). In contrast, ECCE was unaffected by STIM1 knockdown, E106Q expression or E190Q expression. These results are the first to demonstrate that SOCE in skeletal muscle requires both STIM1 and Orai1 and that SOCE and ECCE represent two distinct molecular entities.
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Affiliation(s)
- Alla D Lyfenko
- Department of Physiology and Pharmacology, University of Rochester, Rochester, NY 14642, USA
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17
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Jiang D, Chen W, Xiao J, Wang R, Kong H, Jones PP, Zhang L, Fruen B, Chen SRW. Reduced threshold for luminal Ca2+ activation of RyR1 underlies a causal mechanism of porcine malignant hyperthermia. J Biol Chem 2008; 283:20813-20. [PMID: 18505726 DOI: 10.1074/jbc.m801944200] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Naturally occurring mutations in the skeletal muscle Ca(2+) release channel/ryanodine receptor RyR1 are linked to malignant hyperthermia (MH), a life-threatening complication of general anesthesia. Although it has long been recognized that MH results from uncontrolled or spontaneous Ca(2+) release from the sarcoplasmic reticulum, how MH RyR1 mutations render the sarcoplasmic reticulum susceptible to volatile anesthetic-induced spontaneous Ca(2+) release is unclear. Here we investigated the impact of the porcine MH mutation, R615C, the human equivalent of which also causes MH, on the intrinsic properties of the RyR1 channel and the propensity for spontaneous Ca(2+) release during store Ca(2+) overload, a process we refer to as store overload-induced Ca(2+) release (SOICR). Single channel analyses revealed that the R615C mutation markedly enhanced the luminal Ca(2+) activation of RyR1. Moreover, HEK293 cells expressing the R615C mutant displayed a reduced threshold for SOICR compared with cells expressing wild type RyR1. Furthermore, the MH-triggering agent, halothane, potentiated the response of RyR1 to luminal Ca(2+) and SOICR. Conversely, dantrolene, an effective treatment for MH, suppressed SOICR in HEK293 cells expressing the R615C mutant, but not in cells expressing an RyR2 mutant. These data suggest that the R615C mutation confers MH susceptibility by reducing the threshold for luminal Ca(2+) activation and SOICR, whereas volatile anesthetics trigger MH by further reducing the threshold, and dantrolene suppresses MH by increasing the SOICR threshold. Together, our data support a view in which altered luminal Ca(2+) regulation of RyR1 represents a primary causal mechanism of MH.
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Affiliation(s)
- Dawei Jiang
- Libin Cardiovascular Institutes of Alberta, Department of Physiology, University of Calgary, Calgary, Alberta, Canada
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18
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Alfonso S, Benito O, Alicia S, Angélica Z, Patricia G, Diana K, Vaca L, Luis V. Regulation of the cellular localization and function of human transient receptor potential channel 1 by other members of the TRPC family. Cell Calcium 2007; 43:375-87. [PMID: 17850866 DOI: 10.1016/j.ceca.2007.07.004] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2007] [Revised: 07/06/2007] [Accepted: 07/09/2007] [Indexed: 12/23/2022]
Abstract
Members of the Canonical Transient Receptor Potential (TRPC) family of ionic channels are able to form homo- and heterotetrameric channels. Depending on the study, TRPC1 has been detected on both the surface and inside the cell, probably in the endoplasmic reticulum (ER). Likewise, TRPC1 has been described both as a store-operated channel and as one unable to function when forming a homotetramer. It is possible that the apparent differences in the expression and function of TRPC1 are due to its association with other proteins, possibly from the same TRPC family. In the present study we used confocal microscopy and a fluorescently tagged TRPC1 to examine the localization of this protein when co-expressed with other members of the TRPC family. Whole-cell and single channel electrophysiological recordings were conducted to study the function of TRPC1 expressed alone or co-expressed with other members of the TRPC family. A FRET-based calcium sensor fused to TRPC1 was used to assess the functionality of the intracellular TRPC1. Our results showed that TRPC4 and TRPC5 were able to increase the amount of membrane-expressed TRPC1 as evaluated by confocal microscopy and patch clamp recordings. The FRET-based calcium sensor fused to TRPC1 strongly suggests that this protein forms ER-expressed functional homotetrameric channels activated by agonists coupled to the IP(3) cascade. These results indicate that TRPC1 is a multifunctional protein able to form intracellular calcium release channels when expressed alone, and plasma membrane channels when co-expressed with TRPC4 or TRPC5, but not TRPC3 or TRPC6. Both (ER and plasma membrane) forms of the channel are activated upon addition of agonists coupled to the IP(3) cascade.
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Affiliation(s)
- Salgado Alfonso
- Department of Cell Biology, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, México CP 04510, D.F., Mexico
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19
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Abstract
This chapter reviews recent evidence indicating that canonical or classical transient receptor potential (TRPC) channels are directly or indirectly mechanosensitive (MS) and can therefore be designated as mechano-operated channels (MOCs). The MS functions of TRPCs may be mechanistically related to their better known functions as store-operated and receptor-operated channels (SOCs and ROCs). Mechanical forces may be conveyed to TRPC channels through the "conformational coupling" mechanism that transmits information regarding the status of internal Ca(2+) stores. All TRPCs are regulated by receptors coupled to phospholipases that are themselves MS and can regulate channels via lipidic second messengers. Accordingly, there may be several nonexclusive mechanisms by which mechanical forces may regulate TRPC channels, including direct sensitivity to bilayer mechanics, physical coupling to internal membranes and/or cytoskeletal proteins, and sensitivity to lipidic second messengers generated by MS enzymes. Various strategies that can be used for separating out different MS-gating mechanisms and their possible role in specific TRPCs are discussed.
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Affiliation(s)
- Owen P Hamill
- Department of Neuroscience and Cell Biology, University of Texas Medical Branch, Galveston, Texas 77555
| | - Rosario Maroto
- Department of Neuroscience and Cell Biology, University of Texas Medical Branch, Galveston, Texas 77555
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20
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Abstract
TRP channels, in particular the TRPC and TRPV subfamilies, have emerged as important constituents of the receptor-activated Ca2+ influx mechanism triggered by hormones, growth factors, and neurotransmitters through activation ofphospholipase C (PLC). Several TRPC channels are also activated by passive depletion of endoplasmic reticulum (ER) Ca2+. Although in several studies the native TRP channels faithfully reproduce the respective recombinant channels, more often the properties of Ca2+ entry and/or the store-operated current are strikingly different from that of the TRP channels expressed in the same cells. The present review aims to discuss this disparity in the context of interaction of TRPC channels with auxiliary proteins that may alter the permeation and regulation of TRPC channels.
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Affiliation(s)
- K Kiselyov
- Department of Biological Sciences University of Pittsburgh, Pittsburgh, PA 15260, USA
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21
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Abstract
Orchestrated ion fluctuations within pancreatic islets regulate hormone secretion and maybe essential to processes such as apoptosis. A diverse set of ion channels allows for islet cells to respond to a variety of signals and dynamically regulate hormone secretion and glucose homeostasis (reviewed by Houamed et al. 2004). This chapter focuses on transient receptor potential (TRP)-related channels found within the beta cells of the islet and reviews their roles in both insulin secretion and apoptosis.
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Affiliation(s)
- D A Jacobson
- Department of Medicine-Endocrinology Section, University of Chicago, 5841 S Maryland Ave, Chicago, IL, USA
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22
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Zhao X, Weisleder N, Han X, Pan Z, Parness J, Brotto M, Ma J. Azumolene inhibits a component of store-operated calcium entry coupled to the skeletal muscle ryanodine receptor. J Biol Chem 2006; 281:33477-86. [PMID: 16945924 DOI: 10.1074/jbc.m602306200] [Citation(s) in RCA: 80] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Dantrolene reduces the elevated myoplasmic Ca(2+) generated during malignant hyperthermia, a pharmacogenetic crisis triggered by volatile anesthetics. Although specific binding of dantrolene to the type 1 ryanodine receptor (RyR1), the Ca(2+) release channel of skeletal muscle sarcoplasmic reticulum, has been demonstrated, there is little evidence for direct dantrolene inhibition of RyR1 channel function. Recent studies suggest store-operated Ca(2+) entry (SOCE) contributes to skeletal muscle function, but the effect of dantrolene on this pathway has not been examined. Here we show that azumolene, an equipotent dantrolene analog, inhibits a component of SOCE coupled to activation of RyR1 by caffeine and ryanodine, whereas the SOCE component induced by thapsigargin is not affected. Our data suggest that azumolene distinguishes between two mechanisms of cellular signaling to SOCE in skeletal muscle, one that is coupled to and one independent from RyR1.
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Affiliation(s)
- Xiaoli Zhao
- Department of Physiology and Biophysics, University of Medicine and Dentistry of New Jersey, Piscataway, New Jersey 08854, USA
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23
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Vassilopoulos S, Brocard J, Garcia L, Marty I, Bouron A. Retrograde regulation of store-operated calcium channels by the ryanodine receptor-associated protein triadin 95 in rat skeletal myotubes. Cell Calcium 2006; 41:179-85. [PMID: 16889828 DOI: 10.1016/j.ceca.2006.06.003] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2006] [Revised: 04/21/2006] [Accepted: 06/06/2006] [Indexed: 11/28/2022]
Abstract
The 95kDa triadin (or T95), the main skeletal muscle triadin isoform, negatively regulates the mechanism of excitation-contraction coupling. T95 is a ryanodine receptor (RyR)-interacting protein but it also possesses a calsequestrin-interacting domain. RyR and calsequestrin are involved in Ca2+ signalling and, for instance, influence the activity of store-dependent Ca2+ channels (SOC). This work was undertaken to determine whether T95 was able to modulate the entry of Ca2+ through SOC. The experiments were carried out on differentiated rat myotubes over-expressing T95 or DsRed (control cells) by means of an adenovirus infection. Intracellular Ca2+ signals were analyzed using the Ca2+ indicator Fluo-4. The sarco-endoplasmic reticulum Ca2+-ATPase inhibitor thapsigargin was used to deplete intracellular Ca2+ stores. When applied in the presence of a Ca2+-free medium, thapsigargin elicited transient but long-lasting Fluo-4 responses by elevating the cytoplasmic concentration of Ca2+ ([Ca2+]i). The over-expression of T95 reduced the thapsigargin-dependent [Ca2+]i increase, with respect to control myotubes. Addition of extracellular Ca2+after the depletion of this Ca2+ pool was accompanied by a [Ca2+]i increase that was sensitive to the SOC blockers 2-APB, SKF-96365 and La3+. The over-expression of T95 reduced this Ca2+ influx, without changing its pharmacological properties, showing that T95 over-expression did not alter the properties of the SOC. In conclusion, the RyR-interacting molecule T95, recently shown to inhibit the excitation-contraction coupling, has also the ability to interfere with the skeletal muscle Ca2+ signalling by depressing thapsigargin-dependent Ca2+ release and influx.
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Lee EH, Cherednichenko G, Pessah IN, Allen PD. Functional coupling between TRPC3 and RyR1 regulates the expressions of key triadic proteins. J Biol Chem 2006; 281:10042-8. [PMID: 16484216 DOI: 10.1074/jbc.m600981200] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We have shown that TRPC3 (transient receptor potential channel canonical type 3) is sharply up-regulated during the early part of myotube differentiation and remains elevated in mature myotubes compared with myoblasts. To examine its functional roles in muscle, TRPC3 was "knocked down" in mouse primary skeletal myoblasts using retroviral-delivered small interference RNAs and single cell cloning. TRPC3 knockdown myoblasts (97.6 +/- 1.9% reduction in mRNA) were differentiated into myotubes (TRPC3 KD) and subjected to functional and biochemical assays. By measuring rates of Mn(2+) influx with Fura-2 and Ca(2+) transients with Fluo-4, we found that neither excitation-coupled Ca(2+) entry nor thapsigargin-induced store-operated Ca(2+) entry was significantly altered in TRPC3 KD, indicating that expression of TRPC3 is not required for engaging either Ca(2+) entry mechanism. In Ca(2+) imaging experiments, the gain of excitation-contraction coupling and the amplitude of the Ca(2+) release seen after direct RyR1 activation with caffeine was significantly reduced in TRPC3 KD. The decreased gain appears to be due to a decrease in RyR1 Ca(2+) release channel activity, because sarcoplasmic reticulum (SR) Ca(2+) content was not different between TRPC3 KD and wild-type myotubes. Immunoblot analysis demonstrated that TRPC1, calsequestrin, triadin, and junctophilin 1 were up-regulated (1.46 +/- 1.91-, 1.42 +/- 0.08-, 2.99 +/- 0.32-, and 1.91 +/- 0.26-fold, respectively) in TRPC3 KD. Based on these data, we conclude that expression of TRPC3 is tightly regulated during muscle cell differentiation and propose that functional interaction between TRPC3 and RyR1 may regulate the gain of SR Ca(2+) release independent of SR Ca(2+) load.
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Affiliation(s)
- Eun Hui Lee
- Laboratory of Calcium Communication, Department of Physiology, College of Medicine, The Catholic University of Korea, Seoul 137-701, Korea
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