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Reggiani C, Marcucci L. A controversial issue: Can mitochondria modulate cytosolic calcium and contraction of skeletal muscle fibers? J Gen Physiol 2022; 154:213356. [PMID: 35849108 PMCID: PMC9297197 DOI: 10.1085/jgp.202213167] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Mitochondria are characterized by a high capacity to accumulate calcium thanks to the electrochemical gradient created by the extrusion of protons in the respiratory chain. Thereby calcium can enter crossing the inner mitochondrial membrane via MCU complex, a high-capacity, low-affinity transport mechanism. Calcium uptake serves numerous purposes, among them the regulation of three dehydrogenases of the citric cycle, apoptosis via permeability transition, and, in some cell types, modulation of cytosolic calcium transients. This Review is focused on mitochondrial calcium uptake in skeletal muscle fibers and aims to reanalyze its functional impact. In particular, we ask whether mitochondrial calcium uptake is relevant for the control of cytosolic calcium transients and therefore of contractile performance. Recent data suggest that this may be the case, at least in particular conditions, as modified expression of MCU complex subunits or of proteins involved in mitochondrial dynamics and ablation of the main cytosolic calcium buffer, parvalbumin.
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Affiliation(s)
- Carlo Reggiani
- Department of Biomedical Sciences, University of Padova, Padova, Italy,Science and Research Center Koper, Institute for Kinesiology Research, Koper, Slovenia,Correspondence to Carlo Reggiani:
| | - Lorenzo Marcucci
- Department of Biomedical Sciences, University of Padova, Padova, Italy,Center for Biosystems Dynamics Research, RIKEN, Suita, Japan
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2
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Gherardi G, De Mario A, Mammucari C. The mitochondrial calcium homeostasis orchestra plays its symphony: Skeletal muscle is the guest of honor. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2021; 362:209-259. [PMID: 34253296 DOI: 10.1016/bs.ircmb.2021.03.005] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/03/2023]
Abstract
Skeletal muscle mitochondria are placed in close proximity of the sarcoplasmic reticulum (SR), the main intracellular Ca2+ store. During muscle activity, excitation of sarcolemma and of T-tubule triggers the release of Ca2+ from the SR initiating myofiber contraction. The rise in cytosolic Ca2+ determines the opening of the mitochondrial calcium uniporter (MCU), the highly selective channel of the inner mitochondrial membrane (IMM), causing a robust increase in mitochondrial Ca2+ uptake. The Ca2+-dependent activation of TCA cycle enzymes increases the synthesis of ATP required for SERCA activity. Thus, Ca2+ is transported back into the SR and cytosolic [Ca2+] returns to resting levels eventually leading to muscle relaxation. In recent years, thanks to the molecular identification of MCU complex components, the role of mitochondrial Ca2+ uptake in the pathophysiology of skeletal muscle has been uncovered. In this chapter, we will introduce the reader to a general overview of mitochondrial Ca2+ accumulation. We will tackle the key molecular players and the cellular and pathophysiological consequences of mitochondrial Ca2+ dyshomeostasis. In the second part of the chapter, we will discuss novel findings on the physiological role of mitochondrial Ca2+ uptake in skeletal muscle. Finally, we will examine the involvement of mitochondrial Ca2+ signaling in muscle diseases.
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Affiliation(s)
- Gaia Gherardi
- Department of Biomedical Sciences, University of Padua, Padua, Italy
| | - Agnese De Mario
- Department of Biomedical Sciences, University of Padua, Padua, Italy
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3
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Katti P, Rai M, Srivastava S, D'Silva P, Nongthomba U. Marf-mediated mitochondrial fusion is imperative for the development and functioning of indirect flight muscles (IFMs) in drosophila. Exp Cell Res 2021; 399:112486. [PMID: 33450208 DOI: 10.1016/j.yexcr.2021.112486] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2020] [Revised: 01/07/2021] [Accepted: 01/09/2021] [Indexed: 11/15/2022]
Abstract
Dynamic changes in mitochondrial shape and size are vital for mitochondrial health and for tissue development and function. Adult Drosophila indirect flight muscles contain densely packed mitochondria. We show here that mitochondrial fusion is critical during early muscle development (in pupa) and that silencing of the outer mitochondrial membrane fusion gene, Marf, in muscles results in smaller mitochondria that are functionally defective. This leads to abnormal muscle development resulting in muscle dysfunction in adult flies. However, post-developmental silencing of Marf has no obvious effects on mitochondrial and muscle phenotype in adult flies, indicating the importance of mitochondrial fusion during early muscle development.
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Affiliation(s)
- Prasanna Katti
- Department of Molecular Reproduction, Development and Genetics, Indian Institute of Science, Bangalore, 560 012, India.
| | - Mamta Rai
- Department of Molecular Reproduction, Development and Genetics, Indian Institute of Science, Bangalore, 560 012, India
| | - Shubhi Srivastava
- Department of Biochemistry, Indian Institute of Science, Bangalore, 560012, India
| | - Patrick D'Silva
- Department of Biochemistry, Indian Institute of Science, Bangalore, 560012, India
| | - Upendra Nongthomba
- Department of Molecular Reproduction, Development and Genetics, Indian Institute of Science, Bangalore, 560 012, India.
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4
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Gherardi G, Monticelli H, Rizzuto R, Mammucari C. The Mitochondrial Ca 2+ Uptake and the Fine-Tuning of Aerobic Metabolism. Front Physiol 2020; 11:554904. [PMID: 33117189 PMCID: PMC7575740 DOI: 10.3389/fphys.2020.554904] [Citation(s) in RCA: 48] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2020] [Accepted: 09/14/2020] [Indexed: 12/13/2022] Open
Abstract
Recently, the role of mitochondrial activity in high-energy demand organs and in the orchestration of whole-body metabolism has received renewed attention. In mitochondria, pyruvate oxidation, ensured by efficient mitochondrial pyruvate entry and matrix dehydrogenases activity, generates acetyl CoA that enters the TCA cycle. TCA cycle activity, in turn, provides reducing equivalents and electrons that feed the electron transport chain eventually producing ATP. Mitochondrial Ca2+ uptake plays an essential role in the control of aerobic metabolism. Mitochondrial Ca2+ accumulation stimulates aerobic metabolism by inducing the activity of three TCA cycle dehydrogenases. In detail, matrix Ca2+ indirectly modulates pyruvate dehydrogenase via pyruvate dehydrogenase phosphatase 1, and directly activates isocitrate and α-ketoglutarate dehydrogenases. Here, we will discuss the contribution of mitochondrial Ca2+ uptake to the metabolic homeostasis of organs involved in systemic metabolism, including liver, skeletal muscle, and adipose tissue. We will also tackle the role of mitochondrial Ca2+ uptake in the heart, a high-energy consuming organ whose function strictly depends on appropriate Ca2+ signaling.
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Affiliation(s)
- Gaia Gherardi
- Department of Biomedical Sciences, University of Padua, Padua, Italy
| | | | - Rosario Rizzuto
- Department of Biomedical Sciences, University of Padua, Padua, Italy
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5
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Vicente M, Salgado-Almario J, Soriano J, Burgos M, Domingo B, Llopis J. Visualization of Mitochondrial Ca 2+ Signals in Skeletal Muscle of Zebrafish Embryos with Bioluminescent Indicators. Int J Mol Sci 2019; 20:ijms20215409. [PMID: 31671636 PMCID: PMC6862566 DOI: 10.3390/ijms20215409] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2019] [Revised: 10/25/2019] [Accepted: 10/28/2019] [Indexed: 01/16/2023] Open
Abstract
Mitochondria are believed to play an important role in shaping the intracellular Ca2+ transients during skeletal muscle contraction. There is discussion about whether mitochondrial matrix Ca2+ dynamics always mirror the cytoplasmic changes and whether this happens in vivo in whole organisms. In this study, we characterized cytosolic and mitochondrial Ca2+ signals during spontaneous skeletal muscle contractions in zebrafish embryos expressing bioluminescent GFP-aequorin (GA, cytoplasm) and mitoGFP-aequorin (mitoGA, trapped in the mitochondrial matrix). The Ca2+ transients measured with GA and mitoGA reflected contractions of the trunk observed by transmitted light. The mitochondrial uncoupler FCCP and the inhibitor of the mitochondrial calcium uniporter (MCU), DS16570511, abolished mitochondrial Ca2+ transients whereas they increased the frequency of cytosolic Ca2+ transients and muscle contractions, confirming the subcellular localization of mitoGA. Mitochondrial Ca2+ dynamics were also determined with mitoGA and were found to follow closely cytoplasmic changes, with a slower decay. Cytoplasmic Ca2+ kinetics and propagation along the trunk and tail were characterized with GA and with the genetically encoded fluorescent Ca2+ indicator, Twitch-4. Although fluorescence provided a better spatio-temporal resolution, GA was able to resolve the same kinetic parameters while allowing continuous measurements for hours.
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Affiliation(s)
- Manuel Vicente
- Physiology and Cell Dynamics Group, Centro Regional de Investigaciones Biomédicas (CRIB) and Facultad de Medicina de Albacete, Universidad de Castilla-La Mancha, C/Almansa 14, 02006 Albacete, Spain.
| | - Jussep Salgado-Almario
- Physiology and Cell Dynamics Group, Centro Regional de Investigaciones Biomédicas (CRIB) and Facultad de Medicina de Albacete, Universidad de Castilla-La Mancha, C/Almansa 14, 02006 Albacete, Spain.
| | - Joaquim Soriano
- Physiology and Cell Dynamics Group, Centro Regional de Investigaciones Biomédicas (CRIB) and Facultad de Medicina de Albacete, Universidad de Castilla-La Mancha, C/Almansa 14, 02006 Albacete, Spain.
| | - Miguel Burgos
- Physiology and Cell Dynamics Group, Centro Regional de Investigaciones Biomédicas (CRIB) and Facultad de Medicina de Albacete, Universidad de Castilla-La Mancha, C/Almansa 14, 02006 Albacete, Spain.
| | - Beatriz Domingo
- Physiology and Cell Dynamics Group, Centro Regional de Investigaciones Biomédicas (CRIB) and Facultad de Medicina de Albacete, Universidad de Castilla-La Mancha, C/Almansa 14, 02006 Albacete, Spain.
| | - Juan Llopis
- Physiology and Cell Dynamics Group, Centro Regional de Investigaciones Biomédicas (CRIB) and Facultad de Medicina de Albacete, Universidad de Castilla-La Mancha, C/Almansa 14, 02006 Albacete, Spain.
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6
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Salizzato V, Zanin S, Borgo C, Lidron E, Salvi M, Rizzuto R, Pallafacchina G, Donella-Deana A. Protein kinase CK2 subunits exert specific and coordinated functions in skeletal muscle differentiation and fusogenic activity. FASEB J 2019; 33:10648-10667. [PMID: 31268746 PMCID: PMC6766657 DOI: 10.1096/fj.201801833rr] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2018] [Accepted: 06/04/2019] [Indexed: 01/01/2023]
Abstract
Casein kinase 2 (CK2) is a tetrameric protein kinase composed of 2 catalytic (α and α') and 2 regulatory β subunits. Our study provides the first molecular and cellular characterization of the different CK2 subunits, highlighting their individual roles in skeletal muscle specification and differentiation. Analysis of C2C12 cell knockout for each CK2 subunit reveals that: 1) CK2β is mandatory for the expression of the muscle master regulator myogenic differentiation 1 in proliferating myoblasts, thus controlling both myogenic commitment and subsequent muscle-specific gene expression and myotube formation; 2) CK2α is involved in the activation of the muscle-specific gene program; and 3) CK2α' activity regulates myoblast fusion by mediating plasma membrane translocation of fusogenic proteins essential for membrane coalescence, like myomixer. Accordingly, CK2α' overexpression in C2C12 cells and in mouse regenerating muscle is sufficient to increase myofiber size and myonuclei content via enhanced satellite cell fusion. Consistent with these results, pharmacological inhibition of CK2 activity substantially blocks the expression of myogenic markers and muscle cell fusion both in vitro in C2C12 and primary myoblasts and in vivo in mouse regenerating muscle and zebrafish development. Overall, our work describes the specific and coordinated functions of CK2 subunits in orchestrating muscle differentiation and fusogenic activity, highlighting CK2 relevance in the physiopathology of skeletal muscle tissue.-Salizzato, V., Zanin, S., Borgo, C., Lidron, E., Salvi, M., Rizzuto, R., Pallafacchina, G., Donella-Deana, A. Protein kinase CK2 subunits exert specific and coordinated functions in skeletal muscle differentiation and fusogenic activity.
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Affiliation(s)
- Valentina Salizzato
- Department of Biomedical Sciences, University of Padua, Padua, Italy
- Italian National Research Council (CNR) Neuroscience Institute, Padua, Italy
| | - Sofia Zanin
- Department of Medicine, University of Padua, Padua, Italy
| | - Christian Borgo
- Department of Biomedical Sciences, University of Padua, Padua, Italy
| | - Elisa Lidron
- Department of Biomedical Sciences, University of Padua, Padua, Italy
| | - Mauro Salvi
- Department of Biomedical Sciences, University of Padua, Padua, Italy
| | - Rosario Rizzuto
- Department of Biomedical Sciences, University of Padua, Padua, Italy
| | - Giorgia Pallafacchina
- Department of Biomedical Sciences, University of Padua, Padua, Italy
- Italian National Research Council (CNR) Neuroscience Institute, Padua, Italy
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7
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High-Throughput Screening Using Photoluminescence Probe to Measure Intracellular Calcium Levels. Methods Mol Biol 2019; 1925:1-14. [PMID: 30674012 DOI: 10.1007/978-1-4939-9018-4_1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/25/2023]
Abstract
Aequorin, a 22 kDa protein produced by the jellyfish Aequorea victoria, was the first probe used to measure Ca2+ concentrations ([Ca2+]) of specific intracellular organelles in intact cells. After the binding of Ca2+ to three high-affinity binding sites, an irreversible reaction occurs leading to the emission of photons that is proportional to [Ca2+]. While native aequorin is suitable for measuring cytosolic [Ca2+] after cell stimulation in a range from 0.5 to 10 μM, it cannot be used in organelles where [Ca2+] is much higher, such as in the lumen of endoplasmic/sarcoplasmic reticulum (ER/SR) and mitochondria. However, some modifications made on aequorin itself or on coelenterazine, its lipophilic prosthetic luminophore, and the addition of targeting sequences or the fusion with resident proteins allowed the specific organelle localization and the measurements of intra-organelle Ca2+ levels. In the last years, the development of multiwell plate readers has opened the possibility to perform aequorin-based high-throughput screenings and has overcome some limitation of the standard method. Here we present the procedure for expressing, targeting, and reconstituting aequorin in intact cells and for measuring Ca2+ in the bulk cytosol, mitochondria, and ER by a high-throughput screening system.
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8
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Ex Vivo Measurements of Ca 2+ Transients in Intracellular Compartments of Skeletal Muscle Fibers by Means of Genetically Encoded Probes. Methods Mol Biol 2019; 1925:103-109. [PMID: 30674020 DOI: 10.1007/978-1-4939-9018-4_9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
We report a method for ex vivo measurements of Ca2+ transients in skeletal muscle fibers, both in the sarcoplasma and into the mitochondria. These measurements are based on the use of genetically encoded probes. Addition of targeting DNA sequences, in frame with the probe encoding sequence, ensures protein expression in specific compartments. The use of probes with different excitation spectra allows the simultaneous determination of cytosolic and mitochondrial Ca2+ transients in the same fiber. Probe encoding plasmids are expressed in flexor digitorum brevis (FDB) muscles by means of the in vivo electroporation technique. Measurements are then performed ex vivo in isolated single myofibers.
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9
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SICT: automated detection and supervised inspection of fast Ca 2+ transients. Sci Rep 2018; 8:15523. [PMID: 30341397 PMCID: PMC6195629 DOI: 10.1038/s41598-018-33847-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2018] [Accepted: 10/05/2018] [Indexed: 02/06/2023] Open
Abstract
Recent advances in live Ca2+ imaging with increasing spatial and temporal resolution offer unprecedented opportunities, but also generate an unmet need for data processing. Here we developed SICT, a MATLAB program that automatically identifies rapid Ca2+ rises in time-lapse movies with low signal-to-noise ratios, using fluorescent indicators. A graphical user interface allows visual inspection of automatically detected events, reducing manual labour to less than 10% while maintaining quality control. The detection performance was tested using synthetic data with various signal-to-noise ratios. The event inspection phase was evaluated by four human observers. Reliability of the method was demonstrated in a direct comparison between manual and SICT-aided analysis. As a test case in cultured neurons, SICT detected an increase in frequency and duration of spontaneous Ca2+ transients in the presence of caffeine. This new method speeds up the analysis of elementary Ca2+ transients.
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10
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Mammucari C, Raffaello A, Vecellio Reane D, Gherardi G, De Mario A, Rizzuto R. Mitochondrial calcium uptake in organ physiology: from molecular mechanism to animal models. Pflugers Arch 2018. [PMID: 29541860 PMCID: PMC6060757 DOI: 10.1007/s00424-018-2123-2] [Citation(s) in RCA: 111] [Impact Index Per Article: 18.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Mitochondrial Ca2+ is involved in heterogeneous functions, ranging from the control of metabolism and ATP production to the regulation of cell death. In addition, mitochondrial Ca2+ uptake contributes to cytosolic [Ca2+] shaping thus impinging on specific Ca2+-dependent events. Mitochondrial Ca2+ concentration is controlled by influx and efflux pathways: the former controlled by the activity of the mitochondrial Ca2+ uniporter (MCU), the latter by the Na+/Ca2+ exchanger (NCLX) and the H+/Ca2+ (mHCX) exchanger. The molecular identities of MCU and of NCLX have been recently unraveled, thus allowing genetic studies on their physiopathological relevance. After a general framework on the significance of mitochondrial Ca2+ uptake, this review discusses the structure of the MCU complex and the regulation of its activity, the importance of mitochondrial Ca2+ signaling in different physiological settings, and the consequences of MCU modulation on organ physiology.
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Affiliation(s)
| | - Anna Raffaello
- Department of Biomedical Sciences, University of Padova, Padua, Italy
| | | | - Gaia Gherardi
- Department of Biomedical Sciences, University of Padova, Padua, Italy
| | - Agnese De Mario
- Department of Biomedical Sciences, University of Padova, Padua, Italy
| | - Rosario Rizzuto
- Department of Biomedical Sciences, University of Padova, Padua, Italy.
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11
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Sharifian S, Homaei A, Hemmati R, B Luwor R, Khajeh K. The emerging use of bioluminescence in medical research. Biomed Pharmacother 2018; 101:74-86. [PMID: 29477474 DOI: 10.1016/j.biopha.2018.02.065] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2018] [Revised: 02/13/2018] [Accepted: 02/15/2018] [Indexed: 01/01/2023] Open
Abstract
Bioluminescence is the light produced by a living organism and is commonly emitted by sea life with Ca2+-regulated photoproteins being the most responsible for bioluminescence emission. Marine coelenterates provide important functions involved in essential purposes such as defense, feeding, and breeding. In this review, the main characteristics of marine photoproteins including aequorin, clytin, obelin, berovin, pholasin and symplectin from different marine organisms will be discussed. We will focused on the recent use of recombinant photoproteins in different biomedical research fields including the measurement of Ca2+ in different intracellular compartments of animal cells, as labels in the design and development of binding assays. This review will also outline how bioluminescent photoproteins have been used in a plethora of analytical methods including ultra-sensitive assays and in vivo imaging of cellular processes. Due to their unique properties including elective intracellular distribution, wide dynamic range, high signal-to-noise ratio and low Ca2+-buffering effect, recombinant photoproteins represent a promising future analytical tool in several in vitro and in vivo experiments.
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Affiliation(s)
- Sana Sharifian
- Department of Marine Biology, Faculty of Sciences, University of Hormozgan, Bandar Abbas, Iran
| | - Ahmad Homaei
- Department of Biochemistry, Faculty of Sciences, University of Hormozgan, Bandar Abbas, Iran.
| | - Roohullah Hemmati
- Department of Biology, Faculty of Basic Sciences, Shahrekord University, Shahrekord, Iran
| | - Rodney B Luwor
- Department of Surgery, Level 5, Clinical Sciences Building, The University of Melbourne, The Royal Melbourne Hospital, Grattan Street, Parkville, VIC 3050, Australia
| | - Khosro Khajeh
- Department of Biochemistry, Faculty of Biological Sciences, Tarbiat Modares University, Tehran, Iran
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12
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Zampieri S, Mammucari C, Romanello V, Barberi L, Pietrangelo L, Fusella A, Mosole S, Gherardi G, Höfer C, Löfler S, Sarabon N, Cvecka J, Krenn M, Carraro U, Kern H, Protasi F, Musarò A, Sandri M, Rizzuto R. Physical exercise in aging human skeletal muscle increases mitochondrial calcium uniporter expression levels and affects mitochondria dynamics. Physiol Rep 2017; 4:4/24/e13005. [PMID: 28039397 PMCID: PMC5210373 DOI: 10.14814/phy2.13005] [Citation(s) in RCA: 60] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2016] [Revised: 09/26/2016] [Accepted: 09/26/2016] [Indexed: 01/04/2023] Open
Abstract
Age‐related sarcopenia is characterized by a progressive loss of muscle mass with decline in specific force, having dramatic consequences on mobility and quality of life in seniors. The etiology of sarcopenia is multifactorial and underlying mechanisms are currently not fully elucidated. Physical exercise is known to have beneficial effects on muscle trophism and force production. Alterations of mitochondrial Ca2+ homeostasis regulated by mitochondrial calcium uniporter (MCU) have been recently shown to affect muscle trophism in vivo in mice. To understand the relevance of MCU‐dependent mitochondrial Ca2+ uptake in aging and to investigate the effect of physical exercise on MCU expression and mitochondria dynamics, we analyzed skeletal muscle biopsies from 70‐year‐old subjects 9 weeks trained with either neuromuscular electrical stimulation (ES) or leg press. Here, we demonstrate that improved muscle function and structure induced by both trainings are linked to increased protein levels of MCU. Ultrastructural analyses by electron microscopy showed remodeling of mitochondrial apparatus in ES‐trained muscles that is consistent with an adaptation to physical exercise, a response likely mediated by an increased expression of mitochondrial fusion protein OPA1. Altogether these results indicate that the ES‐dependent physiological effects on skeletal muscle size and force are associated with changes in mitochondrial‐related proteins involved in Ca2+ homeostasis and mitochondrial shape. These original findings in aging human skeletal muscle confirm the data obtained in mice and propose MCU and mitochondria‐related proteins as potential pharmacological targets to counteract age‐related muscle loss.
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Affiliation(s)
- Sandra Zampieri
- Ludwig Boltzmann Institute of Electrical Stimulation and Physical Rehabilitation, Vienna, Austria .,Venetian Institute of Molecular Medicine, Padova, Italy.,Department of Biomedical Science, University of Padova, Padova, Italy
| | | | | | - Laura Barberi
- DAHFMO-Unit of Histology and Medical Embryology, IIM, Institute Pasteur Cenci-Bolognetti, Sapienza University of Rome, Rome, Italy
| | - Laura Pietrangelo
- Department of Neuroscience, Imaging and Clinical Sciences, CeSI-Met - Center for Research on Aging and Translational Medicine & DNICS University G. d'Annunzio, Chieti, Italy
| | - Aurora Fusella
- Department of Neuroscience, Imaging and Clinical Sciences, CeSI-Met - Center for Research on Aging and Translational Medicine & DNICS University G. d'Annunzio, Chieti, Italy
| | - Simone Mosole
- Department of Biomedical Science, University of Padova, Padova, Italy
| | - Gaia Gherardi
- Department of Biomedical Science, University of Padova, Padova, Italy
| | - Christian Höfer
- Ludwig Boltzmann Institute of Electrical Stimulation and Physical Rehabilitation, Vienna, Austria
| | - Stefan Löfler
- Ludwig Boltzmann Institute of Electrical Stimulation and Physical Rehabilitation, Vienna, Austria
| | - Nejc Sarabon
- Science and Research Centre, Institute for Kinesiology Research, University of Primorska, Koper, Slovenia
| | - Jan Cvecka
- Faculty of Physical Education and Sport, Comenius University, Bratislava, Slovakia
| | - Matthias Krenn
- Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria
| | - Ugo Carraro
- Institute of Electrodynamics, Microwave and Circuit Engineering, Vienna University of Technology, Vienna, Austria.,IRCCS Fondazione Ospedale San Camillo, Venezia, Italy
| | - Helmut Kern
- Ludwig Boltzmann Institute of Electrical Stimulation and Physical Rehabilitation, Vienna, Austria
| | - Feliciano Protasi
- Department of Neuroscience, Imaging and Clinical Sciences, CeSI-Met - Center for Research on Aging and Translational Medicine & DNICS University G. d'Annunzio, Chieti, Italy
| | - Antonio Musarò
- DAHFMO-Unit of Histology and Medical Embryology, IIM, Institute Pasteur Cenci-Bolognetti, Sapienza University of Rome, Rome, Italy.,Center for Life Nano Science at Sapienza, Istituto Italiano di Tecnologia, Rome, Italy
| | - Marco Sandri
- Venetian Institute of Molecular Medicine, Padova, Italy.,Department of Biomedical Science, University of Padova, Padova, Italy
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13
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Rimessi A, Pavan C, Ioannidi E, Nigro F, Morganti C, Brugnoli A, Longo F, Gardin C, Ferroni L, Morari M, Vindigni V, Zavan B, Pinton P. Protein Kinase C β: a New Target Therapy to Prevent the Long-Term Atypical Antipsychotic-Induced Weight Gain. Neuropsychopharmacology 2017; 42:1491-1501. [PMID: 28128334 PMCID: PMC5436118 DOI: 10.1038/npp.2017.20] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/08/2016] [Revised: 01/03/2017] [Accepted: 01/21/2017] [Indexed: 12/21/2022]
Abstract
Antipsychotic drugs are currently used in clinical practice for a variety of mental disorders. Among them, clozapine is the most effective medication for treatment-resistant schizophrenia and is most helpful in controlling aggression and the suicidal behavior in schizophrenia and schizoaffective disorder. Although clozapine is associated with a low likelihood of extrapyramidal symptoms and other neurological side effects, it is well known for the weight gain and metabolic side effects, which expose the patient to a greater risk of cardiovascular disorders and premature death, as well as psychosocial issues, leading to non-adherence to therapy. The mechanisms underlying these iatrogenic metabolic disorders are still controversial. We have therefore investigated the in vivo effects of the selective PKCβ inhibitor, ruboxistaurin (LY-333531), in a preclinical model of long-term clozapine-induced weight gain. Cell biology, biochemistry, and behavioral tests have been performed in wild-type and PKCβ knockout mice to investigate the contribution of endogenous PKCβ and its pharmacological inhibition to the psychomotor effects of clozapine. Finally, we also shed light on a novel aspect of the mechanism underlying the clozapine-induced weight gain, demonstrating that the clozapine-dependent PKCβ activation promotes the inhibition of the lipid droplet-selective autophagy process. This paves the way to new therapeutic approaches to this serious complication of clozapine therapy.
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Affiliation(s)
- Alessandro Rimessi
- Department of Morphology, Surgery and Experimental Medicine, Section of Pathology, Oncology and Experimental Biology, Laboratory for Technologies of Advanced Therapies (LTTA), University of Ferrara, Ferrara, Italy
| | - Chiara Pavan
- Unit of Psychiatry, Department of Neurosciences NPSRR, University of Padua, Padua, Italy
| | - Elli Ioannidi
- Department of Morphology, Surgery and Experimental Medicine, Section of Pathology, Oncology and Experimental Biology, Laboratory for Technologies of Advanced Therapies (LTTA), University of Ferrara, Ferrara, Italy
| | - Federica Nigro
- Department of Morphology, Surgery and Experimental Medicine, Section of Pathology, Oncology and Experimental Biology, Laboratory for Technologies of Advanced Therapies (LTTA), University of Ferrara, Ferrara, Italy
| | - Claudia Morganti
- Department of Morphology, Surgery and Experimental Medicine, Section of Pathology, Oncology and Experimental Biology, Laboratory for Technologies of Advanced Therapies (LTTA), University of Ferrara, Ferrara, Italy
| | - Alberto Brugnoli
- Department of Medical Sciences, Section of Pharmacology, Neuroscience Center and National Institute of Neuroscience, University of Ferrara, Ferrara, Italy
| | - Francesco Longo
- Department of Medical Sciences, Section of Pharmacology, Neuroscience Center and National Institute of Neuroscience, University of Ferrara, Ferrara, Italy
| | - Chiara Gardin
- Department of Biomedical Sciences, University of Padua, Padua, Italy
| | - Letizia Ferroni
- Department of Biomedical Sciences, University of Padua, Padua, Italy
| | - Michele Morari
- Department of Medical Sciences, Section of Pharmacology, Neuroscience Center and National Institute of Neuroscience, University of Ferrara, Ferrara, Italy
| | - Vincenzo Vindigni
- Unit of Plastic Surgery, Department of Neurosciences NPSRR, University of Padua, Padua, Italy
| | - Barbara Zavan
- Department of Biomedical Sciences, University of Padua, Padua, Italy
| | - Paolo Pinton
- Department of Morphology, Surgery and Experimental Medicine, Section of Pathology, Oncology and Experimental Biology, Laboratory for Technologies of Advanced Therapies (LTTA), University of Ferrara, Ferrara, Italy,Department of Morphology, Surgery and Experimental Medicine, Section of Pathology, Oncology and Experimental Biology, Laboratory for Technologies of Advanced Therapies (LTTA), University of Ferrara, Via Fossato di Mortara 70 (c/o CUBO), Ferrara 44121, Italy, Tel: +0039 0532455802, Fax: +0039 0532455351, E-mail:
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14
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Alonso MT, Rodríguez-Prados M, Navas-Navarro P, Rojo-Ruiz J, García-Sancho J. Using aequorin probes to measure Ca 2+ in intracellular organelles. Cell Calcium 2017; 64:3-11. [PMID: 28214023 DOI: 10.1016/j.ceca.2017.01.006] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2016] [Accepted: 01/11/2017] [Indexed: 11/28/2022]
Abstract
Aequorins are excellent tools for measuring intra-organellar Ca2+ and assessing its role in physiological and pathological functions. Here we review targeting strategies to express aequorins in various organelles. We address critical topics such as probe affinity tuning as well as normalization and calibration of the signal. We also focus on bioluminescent Ca2+ imaging in nucleus or mitochondria of living cells. Finally, recent advances with a new chimeric GFP-aequorin protein (GAP), which can be used either as luminescent or fluorescent Ca2+ probe, are presented. GAP is robustly expressed in transgenic flies and mice, where it has proven to be a suitable Ca2+ indicator for monitoring physiological Ca2+ signaling ex vivo and in vivo.
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Affiliation(s)
- María Teresa Alonso
- Instituto de Biología y Genética Molecular (IBGM), Universidad de Valladolid and Consejo Superior de Investigaciones Científicas (CSIC), c/Sanz y Forés 3, 47003 Valladolid, Spain.
| | - Macarena Rodríguez-Prados
- Instituto de Biología y Genética Molecular (IBGM), Universidad de Valladolid and Consejo Superior de Investigaciones Científicas (CSIC), c/Sanz y Forés 3, 47003 Valladolid, Spain
| | - Paloma Navas-Navarro
- Instituto de Biología y Genética Molecular (IBGM), Universidad de Valladolid and Consejo Superior de Investigaciones Científicas (CSIC), c/Sanz y Forés 3, 47003 Valladolid, Spain
| | - Jonathan Rojo-Ruiz
- Instituto de Biología y Genética Molecular (IBGM), Universidad de Valladolid and Consejo Superior de Investigaciones Científicas (CSIC), c/Sanz y Forés 3, 47003 Valladolid, Spain
| | - Javier García-Sancho
- Instituto de Biología y Genética Molecular (IBGM), Universidad de Valladolid and Consejo Superior de Investigaciones Científicas (CSIC), c/Sanz y Forés 3, 47003 Valladolid, Spain.
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15
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A MICU1 Splice Variant Confers High Sensitivity to the Mitochondrial Ca 2+ Uptake Machinery of Skeletal Muscle. Mol Cell 2016; 64:760-773. [PMID: 27818145 DOI: 10.1016/j.molcel.2016.10.001] [Citation(s) in RCA: 82] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2016] [Revised: 09/06/2016] [Accepted: 09/30/2016] [Indexed: 01/28/2023]
Abstract
Skeletal muscle is a dynamic organ, characterized by an incredible ability to rapidly increase its rate of energy consumption to sustain activity. Muscle mitochondria provide most of the ATP required for contraction via oxidative phosphorylation. Here we found that skeletal muscle mitochondria express a unique MCU complex containing an alternative splice isoform of MICU1, MICU1.1, characterized by the addition of a micro-exon that is sufficient to greatly modify the properties of the MCU. Indeed, MICU1.1 binds Ca2+ one order of magnitude more efficiently than MICU1 and, when heterodimerized with MICU2, activates MCU current at lower Ca2+ concentrations than MICU1-MICU2 heterodimers. In skeletal muscle in vivo, MICU1.1 is required for sustained mitochondrial Ca2+ uptake and ATP production. These results highlight a novel mechanism of the molecular plasticity of the MCU Ca2+ uptake machinery that allows skeletal muscle mitochondria to be highly responsive to sarcoplasmic [Ca2+] responses.
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16
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Calcium-insensitive splice variants of mammalian E1 subunit of 2-oxoglutarate dehydrogenase complex with tissue-specific patterns of expression. Biochem J 2016; 473:1165-78. [PMID: 26936970 DOI: 10.1042/bcj20160135] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2016] [Accepted: 03/01/2016] [Indexed: 01/17/2023]
Abstract
The 2-oxoglutarate dehydrogenase (OGDH) complex is an important control point in vertebrate mitochondrial oxidative metabolism, including in the citrate cycle and catabolism of alternative fuels including glutamine. It is subject to allosteric regulation by NADH and the ATP/ADP ratio, and by Ca(2+) through binding to the E1 subunit. The latter involves a unique Ca(2+)-binding site which includes D(114)ADLD (site 1). Here, we describe three splice variants of E1 in which either the exon expressing this site is replaced with another exon (loss of site 1, LS1) or an additional exon is expressed leading to the insertion of 15 amino acids just downstream of site 1 (Insert), or both changes occur together (LS1/Insert). We show that all three variants are essentially Ca(2+)-insensitive. Comparison of massive parallel sequence (RNA-Seq) databases demonstrates predominant expression of the Ca(2+)-sensitive archetype form in heart and skeletal muscle, but substantial expression of the Ca(2+)-insensitive variants in brain, pancreatic islets and other tissues. Detailed proteomic and activity studies comparing OGDH complexes from rat heart and brain confirmed the substantial difference in expression between these tissues. The evolution of OGDH variants was explored using bioinformatics, and this indicated that Ca(2+)-sensitivity arose with the emergence of chordates. In all species examined, this was associated with the co-emergence of Ca(2+)-insensitive variants suggesting a retained requirement for the latter in some settings. Tissue-specific expression of OGDH splice variants may thus provide a mechanism that tunes the control of the enzyme to the specialized metabolic and signalling needs of individual cell types.
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17
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Grinstead K, Joel S, Zingg JM, Dikici E, Daunert S. Enabling Aequorin for Biotechnology Applications Through Genetic Engineering. ADVANCES IN BIOCHEMICAL ENGINEERING/BIOTECHNOLOGY 2015:149-179. [PMID: 26475468 DOI: 10.1007/10_2015_336] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
In recent years, luminescent proteins have been studied for their potential application in a variety of detection systems. Bioluminescent proteins, which do not require an external excitation source, are especially well-suited as reporters in analytical detection. The photoprotein aequorin is a bioluminescent protein that can be engineered for use as a molecular reporter under a wide range of conditions while maintaining its sensitivity. Herein, the characteristics of aequorin as well as the engineering and production of aequorin variants and their impact on signal detection in biological systems are presented. The structural features and activity of aequorin, its benefits as a label for sensing and applications in highly sensitive detection, as well as in gaining insight into biological processes are discussed. Among those, focus has been placed on the highly sensitive calcium detection in vivo, in vitro DNA and small molecule sensing, and development of in vivo imaging technologies. Graphical Abstract.
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Affiliation(s)
- Kristen Grinstead
- Department of Biochemistry and Molecular Biology, Miller School of Medicine, University of Miami, Miami, FL, 33136, USA
| | - Smita Joel
- Department of Biochemistry and Molecular Biology, Miller School of Medicine, University of Miami, Miami, FL, 33136, USA
| | - Jean-Marc Zingg
- Department of Biochemistry and Molecular Biology, Miller School of Medicine, University of Miami, Miami, FL, 33136, USA
| | - Emre Dikici
- Department of Biochemistry and Molecular Biology, Miller School of Medicine, University of Miami, Miami, FL, 33136, USA
| | - Sylvia Daunert
- Department of Biochemistry and Molecular Biology, Miller School of Medicine, University of Miami, Miami, FL, 33136, USA.
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18
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Primary Murine Myotubes as a Model for Investigating Muscular Dystrophy. BIOMED RESEARCH INTERNATIONAL 2015; 2015:594751. [PMID: 26380282 PMCID: PMC4561302 DOI: 10.1155/2015/594751] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/31/2014] [Accepted: 03/11/2015] [Indexed: 11/18/2022]
Abstract
Muscular dystrophies caused by defects in various genes are often associated with impairment of calcium homeostasis. Studies of calcium currents are hampered because of the lack of a robust cellular model. Primary murine myotubes, formed upon satellite cell fusion, were examined for their utilization as a model of adult skeletal muscle. We enzymatically isolated satellite cells and induced them to differentiation to myotubes. Myotubes displayed morphological and physiological properties resembling adult muscle fibers. Desmin and myosin heavy chain immunoreactivity in the differentiated myotubes were similar to the mature muscle cross-striated pattern. The myotubes responded to electrical and chemical stimulations with sarcoplasmic reticulum calcium release. Presence of L-type calcium channels in the myotubes sarcolemma was confirmed via whole-cell patch-clamp technique. To assess the use of myotubes for studying functional mutation effects lentiviral transduction was applied. Satellite cells easily underwent transduction and were able to retain a positive expression of lentivirally encoded GFP up to and after the formation of myotubes, without changes in their physiological and morphological properties. Thus, we conclude that murine myotubes may serve as a fruitful cell model for investigating calcium homeostasis in muscular dystrophy and the effects of gene modifications can be assessed due to lentiviral transduction.
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Mammucari C, Gherardi G, Zamparo I, Raffaello A, Boncompagni S, Chemello F, Cagnin S, Braga A, Zanin S, Pallafacchina G, Zentilin L, Sandri M, De Stefani D, Protasi F, Lanfranchi G, Rizzuto R. The mitochondrial calcium uniporter controls skeletal muscle trophism in vivo. Cell Rep 2015; 10:1269-79. [PMID: 25732818 DOI: 10.1016/j.celrep.2015.01.056] [Citation(s) in RCA: 135] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2014] [Revised: 12/23/2014] [Accepted: 01/24/2015] [Indexed: 12/18/2022] Open
Abstract
Muscle atrophy contributes to the poor prognosis of many pathophysiological conditions, but pharmacological therapies are still limited. Muscle activity leads to major swings in mitochondrial [Ca(2+)], which control aerobic metabolism, cell death, and survival pathways. We investigated in vivo the effects of mitochondrial Ca(2+) homeostasis in skeletal muscle function and trophism by overexpressing or silencing the mitochondrial calcium uniporter (MCU). The results demonstrate that in both developing and adult muscles, MCU-dependent mitochondrial Ca(2+) uptake has a marked trophic effect that does not depend on aerobic control but impinges on two major hypertrophic pathways of skeletal muscle, PGC-1α4 and IGF1-Akt/PKB. In addition, MCU overexpression protects from denervation-induced atrophy. These data reveal a novel Ca(2+)-dependent organelle-to-nucleus signaling route that links mitochondrial function to the control of muscle mass and may represent a possible pharmacological target in conditions of muscle loss.
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Affiliation(s)
- Cristina Mammucari
- Department of Biomedical Sciences, University of Padua, Padua 35131, Italy.
| | - Gaia Gherardi
- Department of Biomedical Sciences, University of Padua, Padua 35131, Italy
| | - Ilaria Zamparo
- Department of Biomedical Sciences, University of Padua, Padua 35131, Italy
| | - Anna Raffaello
- Department of Biomedical Sciences, University of Padua, Padua 35131, Italy
| | - Simona Boncompagni
- Ce.S.I. (Center for Research on Ageing) and D.N.I.C.S. (Department of Neuroscience, Imaging and Clinical Sciences), University "G. D'Annunzio" of Chieti, Chieti 66100, Italy
| | - Francesco Chemello
- Department of Biology and CRIBI Biotechnology Center, University of Padua, Padua 35131, Italy
| | - Stefano Cagnin
- Department of Biology and CRIBI Biotechnology Center, University of Padua, Padua 35131, Italy
| | - Alessandra Braga
- Department of Biomedical Sciences, University of Padua, Padua 35131, Italy
| | - Sofia Zanin
- Department of Biomedical Sciences, University of Padua, Padua 35131, Italy
| | - Giorgia Pallafacchina
- Department of Biomedical Sciences, University of Padua, Padua 35131, Italy; Neuroscience Institute, National Research Council, Padua 35131, Italy
| | - Lorena Zentilin
- International Centre for Genetic Engineering and Biotechnology (ICGEB), Trieste 34159, Italy
| | - Marco Sandri
- Department of Biomedical Sciences, University of Padua, Padua 35131, Italy; Neuroscience Institute, National Research Council, Padua 35131, Italy; Dulbecco Telethon Institute at Venetian Institute of Molecular Medicine, Padua 35129, Italy; Telethon Institute of Genetics and Medicine (TIGEM), Naples 80131, Italy
| | - Diego De Stefani
- Department of Biomedical Sciences, University of Padua, Padua 35131, Italy
| | - Feliciano Protasi
- Ce.S.I. (Center for Research on Ageing) and D.N.I.C.S. (Department of Neuroscience, Imaging and Clinical Sciences), University "G. D'Annunzio" of Chieti, Chieti 66100, Italy
| | - Gerolamo Lanfranchi
- Department of Biology and CRIBI Biotechnology Center, University of Padua, Padua 35131, Italy
| | - Rosario Rizzuto
- Department of Biomedical Sciences, University of Padua, Padua 35131, Italy; Neuroscience Institute, National Research Council, Padua 35131, Italy.
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20
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Ottolini D, Calì T, Brini M. Methods to measure intracellular Ca(2+) fluxes with organelle-targeted aequorin-based probes. Methods Enzymol 2015; 543:21-45. [PMID: 24924126 DOI: 10.1016/b978-0-12-801329-8.00002-7] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The photoprotein aequorin generates blue light upon binding of Ca(2+) ions. Together with its very low Ca(2+)-buffering capacity and the possibility to add specific targeting sequences, this property has rendered aequorin particularly suitable to monitor Ca(2+) concentrations in specific subcellular compartments. Recently, a new generation of genetically encoded Ca(2+) probes has been developed by fusing Ca(2+)-responsive elements with the green fluorescent protein (GFP). Aequorin has also been employed to this aim, resulting in an aequorin-GFP chimera with the Ca(2+) sensitivity of aequorin and the fluorescent properties of GFP. This setup has actually solved the major limitation of aequorin, for example, its poor ability to emit light, which rendered it inappropriate for the monitoring of Ca(2+) waves at the single-cell level by imaging. In spite of the numerous genetically encoded Ca(2+) indicators that are currently available, aequorin-based probes remain the method of election when an accurate quantification of Ca(2+) levels is required. Here, we describe currently available aequorin variants and their use for monitoring Ca(2+) waves in specific subcellular compartments. Among various applications, this method is relevant for the study of the alterations of Ca(2+) homeostasis that accompany oncogenesis, tumor progression, and response to therapy.
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Affiliation(s)
- Denis Ottolini
- Department of Biology, University of Padova, Padova, Italy
| | - Tito Calì
- Department of Biology, University of Padova, Padova, Italy
| | - Marisa Brini
- Department of Biology, University of Padova, Padova, Italy.
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21
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Studies on the regulation of the human E1 subunit of the 2-oxoglutarate dehydrogenase complex, including the identification of a novel calcium-binding site. Biochem J 2014; 459:369-81. [PMID: 24495017 DOI: 10.1042/bj20131664] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The regulation of the 2-oxoglutarate dehydrogenase complex is central to intramitochondrial energy metabolism. In the present study, the active full-length E1 subunit of the human complex has been expressed and shown to be regulated by Ca2+, adenine nucleotides and NADH, with NADH exerting a major influence on the K0.5 value for Ca2+. We investigated two potential Ca2+-binding sites on E1, which we term site 1 (D114ADLD) and site 2 (E139SDLD). Comparison of sequences from vertebrates with those from Ca2+-insensitive non-vertebrate complexes suggest that site 1 may be the more important. Consistent with this view, a mutated form of E1, D114A, shows a 6-fold decrease in sensitivity for Ca2+, whereas variant ∆site1 (in which the sequence of site 1 is replaced by A114AALA) exhibits an almost complete loss of Ca2+ activation. Variant ∆site2 (in which the sequence is replaced with A139SALA) shows no measurable change in Ca2+ sensitivity. We conclude that site 1, but not site 2, forms part of a regulatory Ca2+-binding site, which is distinct from other previously described Ca2+-binding sites.
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22
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Eisner V, Lenaers G, Hajnóczky G. Mitochondrial fusion is frequent in skeletal muscle and supports excitation-contraction coupling. ACTA ACUST UNITED AC 2014; 205:179-95. [PMID: 24751540 PMCID: PMC4003250 DOI: 10.1083/jcb.201312066] [Citation(s) in RCA: 113] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Mitochondrial fusion is frequent in skeletal muscle, and its disruption jeopardizes excitation–contraction coupling and may contribute to the pathology of myopathies. Genetic targeting experiments indicate a fundamental role for mitochondrial fusion proteins in mammalian physiology. However, owing to the multiple functions of fusion proteins, their related phenotypes are not necessarily caused by altered mitochondrial fusion. Perhaps the biggest mystery is presented by skeletal muscle, where mostly globular-shaped mitochondria are densely packed into the narrow intermyofilamental space, limiting the interorganellar interactions. We show here that mitochondria form local networks and regularly undergo fusion events to share matrix content in skeletal muscle fibers. However, fusion events are less frequent and more stable in the fibers than in nondifferentiated myoblasts. Complementation among muscle mitochondria was suppressed by both in vivo genetic perturbations and chronic alcohol consumption that cause myopathy. An Mfn1-dependent pathway is revealed whereby fusion inhibition weakens the metabolic reserve of mitochondria to cause dysregulation of calcium oscillations during prolonged stimulation. Thus, fusion dynamically connects skeletal muscle mitochondria and its prolonged loss jeopardizes bioenergetics and excitation–contraction coupling, providing a potential pathomechanism contributing to myopathies.
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Affiliation(s)
- Verónica Eisner
- MitoCare Center, Department of Pathology, Anatomy, and Cell Biology, Thomas Jefferson University, Philadelphia, PA 19107
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23
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Granatiero V, Patron M, Tosatto A, Merli G, Rizzuto R. Using targeted variants of aequorin to measure Ca2+ levels in intracellular organelles. Cold Spring Harb Protoc 2014; 2014:86-93. [PMID: 24371314 DOI: 10.1101/pdb.prot072843] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Aequorin is a Ca(2+)-sensitive photoprotein isolated from the jellyfish Aequorea victoria. It is an ideal probe for measuring Ca(2+) concentration ([Ca(2+)]) in intracellular organelles because it can be modified to include specific targeting sequences. On the binding of Ca(2+) to three high-affinity sites in aequorin, an irreversible reaction occurs in which the prosthetic group coelenterazine is released and a photon is emitted. This protocol presents procedures for expressing, targeting, and reconstituting aequorin in intact and permeabilized mammalian cells and describes how to use this photoprotein to measure intracellular [Ca(2+)] in various subcellular compartments.
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Affiliation(s)
- Veronica Granatiero
- Department of Biomedical Sciences, University of Padua and CNR Neuroscience Institute, 35131 Padua, Italy
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24
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Granatiero V, Patron M, Tosatto A, Merli G, Rizzuto R. The use of aequorin and its variants for Ca2+ measurements. Cold Spring Harb Protoc 2014; 2014:9-16. [PMID: 24371311 DOI: 10.1101/pdb.top066118] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Ca(2+)-sensitive photoproteins are ideal agents for measuring the Ca(2+) concentration ([Ca(2+)]) in intracellular organelles because they can be modified to include specific targeting sequences. Aequorin was the first Ca(2+)-sensitive photoprotein probe used to measure the [Ca(2+)] inside specific intracellular organelles in intact cells. Aequorin is a 22-kDa protein produced by the jellyfish Aequorea victoria. On the binding of Ca(2+) to three high-affinity sites in aequorin, an irreversible reaction occurs in which the prosthetic group is released and a photon is emitted. Aequorin has become widely used for intracellular Ca(2+) measurements because it offers many advantages: For example, it can be targeted with precision, functions over a wide range of [Ca(2+)], and shows low buffering capacity. In this article we describe the main characteristics of the aequorin probe and review the reasons why it is widely used to measure intracellular [Ca(2+)].
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Affiliation(s)
- Veronica Granatiero
- Department of Biomedical Sciences, University of Padua and CNR Neuroscience Institute, 35131 Padua, Italy
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25
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Subcellular calcium measurements in mammalian cells using jellyfish photoprotein aequorin-based probes. Nat Protoc 2013; 8:2105-18. [DOI: 10.1038/nprot.2013.127] [Citation(s) in RCA: 130] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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26
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Eisner V, Csordás G, Hajnóczky G. Interactions between sarco-endoplasmic reticulum and mitochondria in cardiac and skeletal muscle - pivotal roles in Ca²⁺ and reactive oxygen species signaling. J Cell Sci 2013; 126:2965-78. [PMID: 23843617 DOI: 10.1242/jcs.093609] [Citation(s) in RCA: 156] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Mitochondria are strategically and dynamically positioned in the cell to spatially coordinate ATP production with energy needs and to allow the local exchange of material with other organelles. Interactions of mitochondria with the sarco-endoplasmic reticulum (SR/ER) have been receiving much attention owing to emerging evidence on the role these sites have in cell signaling, dynamics and biosynthetic pathways. One of the most important physiological and pathophysiological paradigms for SR/ER-mitochondria interactions is in cardiac and skeletal muscle. The contractile activity of these tissues has to be matched by mitochondrial ATP generation that is achieved, at least in part, by propagation of Ca(2+) signals from SR to mitochondria. However, the muscle has a highly ordered structure, providing only limited opportunity for mitochondrial dynamics and interorganellar interactions. This Commentary focuses on the latest advances in the structure, function and disease relevance of the communication between SR/ER and mitochondria in muscle. In particular, we discuss the recent demonstration of SR/ER-mitochondria tethers that are formed by multiple proteins, and local Ca(2+) transfer between SR/ER and mitochondria.
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Affiliation(s)
- Verónica Eisner
- Department of Pathology, Anatomy and Cell Biology, Thomas Jefferson University, Philadelphia, PA 19107, USA.
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27
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Botta A, Malena A, Loro E, Del Moro G, Suman M, Pantic B, Szabadkai G, Vergani L. Altered Ca2+ homeostasis and endoplasmic reticulum stress in myotonic dystrophy type 1 muscle cells. Genes (Basel) 2013; 4:275-92. [PMID: 24705164 PMCID: PMC3899969 DOI: 10.3390/genes4020275] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2013] [Revised: 05/03/2013] [Accepted: 05/16/2013] [Indexed: 12/15/2022] Open
Abstract
The pathogenesis of Myotonic Dystrophy type 1 (DM1) is linked to unstable CTG repeats in the DMPK gene which induce the mis-splicing to fetal/neonatal isoforms of many transcripts, including those involved in cellular Ca2+ homeostasis. Here we monitored the splicing of three genes encoding for Ca2+ transporters and channels (RyR1, SERCA1 and CACN1S) during maturation of primary DM1 muscle cells in parallel with the functionality of the Excitation-Contraction (EC) coupling machinery. At 15 days of differentiation, fetal isoforms of SERCA1 and CACN1S mRNA were significantly higher in DM1 myotubes compared to controls. Parallel functional studies showed that the cytosolic Ca2+ response to depolarization in DM1 myotubes did not increase during the progression of differentiation, in contrast to control myotubes. While we observed no differences in the size of intracellular Ca2+ stores, DM1 myotubes showed significantly reduced RyR1 protein levels, uncoupling between the segregated ER/SR Ca2+ store and the voltage-induced Ca2+ release machinery, parallel with induction of endoplasmic reticulum (ER) stress markers. In conclusion, our data suggest that perturbed Ca2+ homeostasis, via activation of ER stress, contributes to muscle degeneration in DM1 muscle cells likely representing a premature senescence phenotype.
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Affiliation(s)
- Annalisa Botta
- Department of Genetics, University "Tor Vergata", Roma 00133, Italy.
| | - Adriana Malena
- Department of Neurosciences SNPSRR, University of Padova, Padova 35100, Italy.
| | - Emanuele Loro
- Department of Physiology, Pennsylvania Muscle Institute, University of Pennsylvania, Philadelphia, PA 19104, USA.
| | - Giulia Del Moro
- Department of Neurosciences SNPSRR, University of Padova, Padova 35100, Italy.
| | - Matteo Suman
- Department of Biomedical Sciences, University of Padua and CNR Neuroscience Institute, Padua 35100, Italy.
| | - Boris Pantic
- Department of Neurosciences SNPSRR, University of Padova, Padova 35100, Italy.
| | - Gyorgy Szabadkai
- Department of Biomedical Sciences, University of Padua and CNR Neuroscience Institute, Padua 35100, Italy.
| | - Lodovica Vergani
- Department of Neurosciences SNPSRR, University of Padova, Padova 35100, Italy.
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28
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Ottolini D, Calì T, Brini M. Measurements of Ca²⁺ concentration with recombinant targeted luminescent probes. Methods Mol Biol 2013; 937:273-91. [PMID: 23007593 DOI: 10.1007/978-1-62703-086-1_17] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
In the last two decades the study of Ca(2+) homeostasis in living cells has been enhanced by the explosive development of genetically encoded Ca(2+)-indicators. The cloning of the Ca(2+)-sensitive photoprotein aequorin and of the green fluorescent protein (GFP) from the jellyfish Aequorea victoria has been enormously advantageous. As polypeptides, aequorin and GFP allow their endogenous production in cell systems as diverse as bacteria, yeast, slime molds, plants, and mammalian cells. Moreover, it is possible to specifically localize them within the cell by including defined targeting signals in the amino acid sequence. These two proteins have been extensively engineered to obtain several recombinant probes for different biological parameters, among which Ca(2+) concentration reporters are probably the most relevant. The GFP-based Ca(2+) probes and aequorin are widely employed in the study of intracellular Ca(2+) homeostasis. The new generation of bioluminescent probes that couple the Ca(2+) sensitivity of aequorin to GFP fluorescence emission allows real-time measurements of subcellular Ca(2+) changes in single cell imaging experiments and the video-imaging of Ca(2+) concentrations changes in live transgenic animals that express GFP-aequorin bifunctional probes.
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Affiliation(s)
- Denis Ottolini
- Department of Biomedical Sciences, University of Padova, Padova, Italy
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29
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Yi M, Weaver D, Eisner V, Várnai P, Hunyady L, Ma J, Csordás G, Hajnóczky G. Switch from ER-mitochondrial to SR-mitochondrial calcium coupling during muscle differentiation. Cell Calcium 2012; 52:355-65. [PMID: 22784666 DOI: 10.1016/j.ceca.2012.05.012] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2012] [Revised: 05/25/2012] [Accepted: 05/28/2012] [Indexed: 11/26/2022]
Abstract
Emerging evidence indicates that mitochondria are locally coupled to endoplasmic reticulum (ER) Ca2+ release in myoblasts and to sarcoplasmic reticulum (SR) Ca2+ release in differentiated muscle fibers in order to regulate cytoplasmic calcium dynamics and match metabolism with cell activity. However, the mechanism of the developmental transition from ER to SR coupling remains unclear. We have studied mitochondrial sensing of IP3 receptor (IP3R)- and ryanodine receptor (RyR)-mediated Ca2+ signals in H9c2 myoblasts and differentiating myotubes, as well as the attendant changes in mitochondrial morphology. Mitochondria in myoblasts were largely elongated, luminally connected and relatively few in number, whereas the myotubes were densely packed with globular mitochondria that displayed limited luminal continuity. Vasopressin, an IP3-linked agonist, evoked a large cytoplasmic Ca2+ ([Ca2+]c) increase in myoblasts, whereas it elicited a smaller response in myotubes. Conversely, RyR-mediated Ca2+ release induced by caffeine, was not observed in myoblasts, but triggered a large [Ca2+]c signal in myotubes. Both the IP3R and the RyR-mediated [Ca2+]c rise was closely associated with a mitochondrial matrix Ca2+ ([Ca2+]m) signal. Every myotube that showed a [Ca2+]c spike also displayed a [Ca2+]m response. Addition of IP3 to permeabilized myoblasts and caffeine to permeabilized myotubes also resulted in a rapid [Ca2+]m rise, indicating that Ca2+ was delivered via local coupling of the ER/SR and mitochondria. Thus, as RyRs are expressed during muscle differentiation, the local connection between RyR and mitochondrial Ca2+ uptake sites also appears. When RyR1 was exogenously introduced to myoblasts by overexpression, the [Ca2+]m signal appeared together with the [Ca2+]c signal, however the mitochondrial morphology remained unchanged. Thus, RyR expression alone is sufficient to induce the steps essential for their alignment with mitochondrial Ca2+ uptake sites, whereas the mitochondrial proliferation and reshaping utilize either downstream or alternative pathways.
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Affiliation(s)
- Muqing Yi
- Department of Pathology, Anatomy and Cell Biology, Thomas Jefferson University, Philadelphia, PA 19107, USA
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Lee EJ, Lee HJ, Kamli MR, Pokharel S, Bhat AR, Lee YH, Choi BH, Chun T, Kang SW, Lee YS, Kim JW, Schnabel RD, Taylor JF, Choi I. Depot-specific gene expression profiles during differentiation and transdifferentiation of bovine muscle satellite cells, and differentiation of preadipocytes. Genomics 2012; 100:195-202. [PMID: 22728265 DOI: 10.1016/j.ygeno.2012.06.005] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2011] [Revised: 05/18/2012] [Accepted: 06/13/2012] [Indexed: 01/22/2023]
Abstract
We report a systematic study of gene expression during myogenesis and transdifferentiation in four bovine muscle tissues and of adipogenesis in three bovine fat tissues using DNA microarray analysis. One hundred hybridizations were performed and 7245 genes of known and unknown function were identified as being differentially expressed. Supervised hierarchical cluster analysis of gene expression patterns revealed the tissue specificity of genes. A close relationship in global gene expression observed for adipocyte-like cells derived from muscle and adipocytes derived from intramuscular fat suggests a common origin for these cells. The role of transthyretin in myogenesis is a novel finding. Different genes were highly induced during the transdifferentiation of myogenic satellite cells and in the adipogenesis of preadipocytes, indicating the involvement of different molecular mechanisms in these processes. Induction of CD36 and FABP4 expression in adipocyte-like cells and adipocytes may share a common pathway.
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Affiliation(s)
- Eun Ju Lee
- School of Biotechnology, Yeungnam University, Gyeongsan, Republic of Korea
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Glancy B, Balaban RS. Role of mitochondrial Ca2+ in the regulation of cellular energetics. Biochemistry 2012; 51:2959-73. [PMID: 22443365 DOI: 10.1021/bi2018909] [Citation(s) in RCA: 446] [Impact Index Per Article: 37.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Calcium is an important signaling molecule involved in the regulation of many cellular functions. The large free energy in the Ca(2+) ion membrane gradients makes Ca(2+) signaling inherently sensitive to the available cellular free energy, primarily in the form of ATP. In addition, Ca(2+) regulates many cellular ATP-consuming reactions such as muscle contraction, exocytosis, biosynthesis, and neuronal signaling. Thus, Ca(2+) becomes a logical candidate as a signaling molecule for modulating ATP hydrolysis and synthesis during changes in numerous forms of cellular work. Mitochondria are the primary source of aerobic energy production in mammalian cells and also maintain a large Ca(2+) gradient across their inner membrane, providing a signaling potential for this molecule. The demonstrated link between cytosolic and mitochondrial Ca(2+) concentrations, identification of transport mechanisms, and the proximity of mitochondria to Ca(2+) release sites further supports the notion that Ca(2+) can be an important signaling molecule in the energy metabolism interplay of the cytosol with the mitochondria. Here we review sites within the mitochondria where Ca(2+) plays a role in the regulation of ATP generation and potentially contributes to the orchestration of cellular metabolic homeostasis. Early work on isolated enzymes pointed to several matrix dehydrogenases that are stimulated by Ca(2+), which were confirmed in the intact mitochondrion as well as cellular and in vivo systems. However, studies in these intact systems suggested a more expansive influence of Ca(2+) on mitochondrial energy conversion. Numerous noninvasive approaches monitoring NADH, mitochondrial membrane potential, oxygen consumption, and workloads suggest significant effects of Ca(2+) on other elements of NADH generation as well as downstream elements of oxidative phosphorylation, including the F(1)F(O)-ATPase and the cytochrome chain. These other potential elements of Ca(2+) modification of mitochondrial energy conversion will be the focus of this review. Though most specific molecular mechanisms have yet to be elucidated, it is clear that Ca(2+) provides a balanced activation of mitochondrial energy metabolism that exceeds the alteration of dehydrogenases alone.
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Affiliation(s)
- Brian Glancy
- Laboratory of Cardiac Energetics, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, Maryland 20817, USA
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Hernández-Ochoa EO, Schneider MF. Voltage clamp methods for the study of membrane currents and SR Ca(2+) release in adult skeletal muscle fibres. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2012; 108:98-118. [PMID: 22306655 DOI: 10.1016/j.pbiomolbio.2012.01.001] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/07/2011] [Revised: 01/14/2012] [Accepted: 01/17/2012] [Indexed: 01/03/2023]
Abstract
Skeletal muscle excitation-contraction (E-C)(1) coupling is a process composed of multiple sequential stages, by which an action potential triggers sarcoplasmic reticulum (SR)(2) Ca(2+) release and subsequent contractile activation. The various steps in the E-C coupling process in skeletal muscle can be studied using different techniques. The simultaneous recordings of sarcolemmal electrical signals and the accompanying elevation in myoplasmic Ca(2+), due to depolarization-initiated SR Ca(2+) release in skeletal muscle fibres, have been useful to obtain a better understanding of muscle function. In studying the origin and mechanism of voltage dependency of E-C coupling a variety of different techniques have been used to control the voltage in adult skeletal fibres. Pioneering work in muscles isolated from amphibians or crustaceans used microelectrodes or 'high resistance gap' techniques to manipulate the voltage in the muscle fibres. The development of the patch clamp technique and its variant, the whole-cell clamp configuration that facilitates the manipulation of the intracellular environment, allowed the use of the voltage clamp techniques in different cell types, including skeletal muscle fibres. The aim of this article is to present an historical perspective of the voltage clamp methods used to study skeletal muscle E-C coupling as well as to describe the current status of using the whole-cell patch clamp technique in studies in which the electrical and Ca(2+) signalling properties of mouse skeletal muscle membranes are being investigated.
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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 St., Baltimore, MD 21201, USA.
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Lamboley CRH, Pape PC. The concentration of free Ca(2+) in the sarcoplasmic reticulum of frog cut twitch skeletal muscle fibers estimated with tetramethylmurexide. Cell Calcium 2011; 50:530-47. [PMID: 22036161 DOI: 10.1016/j.ceca.2011.09.001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2011] [Revised: 08/19/2011] [Accepted: 09/10/2011] [Indexed: 11/30/2022]
Abstract
One aim of this article was to determine the resting concentration of free Ca(2+) in the sarcoplasmic reticulum (SR) of frog cut skeletal muscle fibers ([Ca(2+)](SR,R)) using the calcium absorbance indicator dye tetramethylmurexide (TMX). Another was to determine the ratio of [Ca(2+)](SR,R) to TMX's apparent dissociation constant for Ca(2+) (K(app)) in order to establish the capability of monitoring [Ca(2+)](SR)(t) during SR Ca(2+) release - a signal needed to determine the Ca(2+) permeability of the SR. To reveal the properties of TMX in the SR, the surface membrane was rapidly permeabilized with saponin to rapidly dissipate myoplasmic TMX. Results indicated that the concentration of Ca-free TMX in the SR was 2.8-fold greater than that in the myoplasm apparently due to binding of TMX to sites in the SR. Taking into account that such binding might influence K(app) as well as a dependence of K(app) on TMX concentration, the results indicate an average [Ca(2+)](SR,R) ranging from 0.43 to 1.70mM. The ratio [Ca(2+)](SR,R)/K(app) averaged 0.256, a relatively low value which should not depend on factors influencing K(app). As a result, the time course of [Ca(2+)](SR)(t) in response to electrical stimulation is well determined by, and approximately linearly related to, the active TMX absorbance signal.
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Affiliation(s)
- Cédric R H Lamboley
- Département de physiologie et biophysique, Université de Sherbrooke, (Québec), Canada.
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Nitric oxide inhibition of Drp1-mediated mitochondrial fission is critical for myogenic differentiation. Cell Death Differ 2010; 17:1684-96. [PMID: 20467441 DOI: 10.1038/cdd.2010.48] [Citation(s) in RCA: 93] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
During myogenic differentiation the short mitochondria of myoblasts change into the extensively elongated network observed in myotubes. The functional relevance and the molecular mechanisms driving the formation of this mitochondrial network are unknown. We now show that mitochondrial elongation is required for myogenesis to occur and that this event depends on the cellular generation of nitric oxide (NO). Inhibition of NO synthesis in myogenic precursor cells leads to inhibition of mitochondrial elongation and of myogenic differentiation. This is due to the enhanced activity, translocation and docking of the pro-fission GTPase dynamin-related protein-1 (Drp1) to mitochondria, leading also to a latent mitochondrial dysfunction that increased sensitivity to apoptotic stimuli. These effects of NO inhibition were not observed in myogenic precursor cells containing a dominant-negative form of Drp1. Both NO-dependent repression of Drp1 action and maintenance of mitochondrial integrity and function were mediated through the soluble guanylate cyclase. These data uncover a novel level of regulation of differentiation linking mitochondrial morphology and function to myogenic differentiation.
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Lefaucheur L. A second look into fibre typing – Relation to meat quality. Meat Sci 2010; 84:257-70. [DOI: 10.1016/j.meatsci.2009.05.004] [Citation(s) in RCA: 206] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2009] [Revised: 04/16/2009] [Accepted: 05/03/2009] [Indexed: 12/25/2022]
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Webb SE, Rogers KL, Karplus E, Miller AL. The use of aequorins to record and visualize Ca(2+) dynamics: from subcellular microdomains to whole organisms. Methods Cell Biol 2010; 99:263-300. [PMID: 21035690 DOI: 10.1016/b978-0-12-374841-6.00010-4] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
In this chapter, we describe the practical aspects of measuring [Ca(2+)] transients that are generated in a particular cytoplasmic domain, or within a specific organelle or its periorganellar environment, using bioluminescent, genetically encoded and targeted Ca(2+) reporters, especially those based on apoaequorin. We also list examples of the organisms, tissues, and cells that have been transfected with apoaequorin or an apoaequorin-BRET complex, as well as of the organelles and subcellular domains that have been specifically targeted with these bioluminescent Ca(2+) reporters. In addition, we summarize the various techniques used to load the apoaequorin cofactor, coelenterazine, and its analogs into cells, tissues, and intact organisms, and we describe recent advances in the detection and imaging technologies that are currently being used to measure and visualize the luminescence generated by the aequorin-Ca(2+) reaction within these various cytoplasmic domains and subcellular compartments.
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Affiliation(s)
- Sarah E Webb
- Biochemistry and Cell Biology Section and State Key Laboratory of Molecular Neuroscience, Division of Life Science, HKUST, Clear Water Bay, Kowloon, Hong Kong, PR China
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Weight gain related to treatment with atypical antipsychotics is due to activation of PKC-β. THE PHARMACOGENOMICS JOURNAL 2009; 10:408-17. [PMID: 20029385 DOI: 10.1038/tpj.2009.67] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Atypical antipsychotics (APDs) are currently used in clinical practice for a variety of mental disorders such as schizophrenia, bipolar disorder and severe behavioral disturbances. A well-known disadvantage of using these compounds is a propensity for weight gain, resulting frequently in obesity. The mechanisms underlying pharmacologically induced weight gain are still controversial. The objective of this study was to evaluate in vitro the effects of different APDs on adipogenic events in cultured human pre-adipocytes and in rat muscle-derived stem cells (MDSCs), aiming to identify a common intracellular event contributable to these drugs. Culture behavior was evaluated in terms of cell proliferation, lipid accumulation, gene expression and morphological features. Results indicate that APDs influence adipogenic events through changes in the differentiation and proliferation of pre-adipocytes and MDSCs that are brought on by protein kinase C-β (PKC-β) activation. These data identify a signaling route that could be a potential target of pharmacological approaches for preventing the weight gain associated with APD treatment.
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Yue T, Fang Q, Yin J, Li D, Li W. S-adenosylmethionine stimulates fatty acid metabolism-linked gene expression in porcine muscle satellite cells. Mol Biol Rep 2009; 37:3143-9. [DOI: 10.1007/s11033-009-9893-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2009] [Accepted: 10/02/2009] [Indexed: 12/25/2022]
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Laude AJ, Simpson AWM. Compartmentalized signalling: Ca2+ compartments, microdomains and the many facets of Ca2+ signalling. FEBS J 2009; 276:1800-16. [PMID: 19243429 DOI: 10.1111/j.1742-4658.2009.06927.x] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Ca(2+) regulates a multitude of cellular processes and does so by partitioning its actions in space and time. In this review, we discuss how Ca(2+) responses are constructed from small quantal (elementary) events that have the potential to propagate to produce large pan-cellular responses. We review how Ca(2+) is compartmentalized both physically and functionally, and describe how each organelle has its own distinct Ca(2+)-handling properties. We explain how coordination of the movement of Ca(2+) between organelles is used to shape and hone Ca(2+) signals. Finally, we provide a number of specific examples of where compartmentation and localization of Ca(2+) are crucial to cell function.
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Affiliation(s)
- Alex J Laude
- Department Human Anatomy and Cell Biology, University of Liverpool, Liverpool, UK
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Brini M. Calcium-sensitive photoproteins. Methods 2008; 46:160-6. [DOI: 10.1016/j.ymeth.2008.09.011] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2008] [Accepted: 09/12/2008] [Indexed: 12/28/2022] Open
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Pozzan T, Rizzuto R. Imaging calcium dynamics using targeted recombinant aequorins. Cold Spring Harb Protoc 2008; 2008:pdb.top26. [PMID: 21356897 DOI: 10.1101/pdb.top26] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
INTRODUCTIONAequorin is a small protein produced by the genus Aequorea that was widely used in the 1960s and 1970s as a probe to measure Ca(2+) in living cells. The invention of the carboxylate Ca(2+) indicators, which are much simpler to load into intact living cells and to calibrate and image at the single-cell level, has led most groups to abandon aequorin. Yet, this latter Ca(2+) indicator still offers some advantages over the fluorescent probes. In particular, the use of molecular biological techniques for expressing recombinant aequorin in mammalian cells, thus eliminating the need for microinjection, has opened new possibilities for this probe. Among the new uses of aequorin, one of the most interesting is the potential for targeting it specifically to different cellular locations, thus opening the possibility of monitoring selectively the dynamics of [Ca(2+)] with unprecedented spatial resolution. This article briefly discusses the problems concerned with targeting aequorin to different locations, the advantages and disadvantages offered by the steep dependence of luminescence on [Ca(2+)], and the instruments needed to obtain reliable measurements.
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Gerasimenko O, Tepikin A. How to measure Ca2+ in cellular organelles? Cell Calcium 2008; 38:201-11. [PMID: 16102822 DOI: 10.1016/j.ceca.2005.06.025] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2005] [Accepted: 06/28/2005] [Indexed: 11/27/2022]
Abstract
The review will aim to briefly summarise information on calcium measurements in cellular organelles with emphases on studies conducted in live cells using optical probes. When appropriate we will try to compare the effectiveness of different indicators for intraorganellar calcium measurements. We will consider calcium measurements in endoplasmic reticulum, Golgi apparatus, endosomes/lysosomes, nucleoplasm, nuclear envelope, mitochondria and secretory granules.
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Affiliation(s)
- Oleg Gerasimenko
- The Physiological Laboratory, The University of Liverpool, Crown Street, P.O. Box 147, Liverpool L69 3BX, UK
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Angelin A, Bonaldo P, Bernardi P. Altered threshold of the mitochondrial permeability transition pore in Ullrich congenital muscular dystrophy. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2008; 1777:893-6. [PMID: 18435905 DOI: 10.1016/j.bbabio.2008.03.026] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/30/2008] [Revised: 03/20/2008] [Accepted: 03/25/2008] [Indexed: 11/30/2022]
Abstract
We have studied the effects of rotenone in myoblasts from healthy donors and from patients with Ullrich congenital muscular dystrophy (UCMD), a severe muscle disease due to mutations in the genes encoding the extracellular matrix protein collagen VI. Addition of rotenone to normal myoblasts caused a very limited mitochondrial depolarization because the membrane potential was maintained by the F1FO synthase, as indicated by full depolarization following the subsequent addition of oligomycin. In UCMD myoblasts rotenone instead caused complete mitochondrial depolarization, which was followed by faster ATP depletion than in healthy myoblasts. Mitochondrial depolarization could be prevented by treatment with cyclosporin A and intracellular Ca(2+) chelators, while it was worsened by depleting Ca(2+) stores with thapsigargin. Thus, in UCMD myoblasts rotenone-induced depolarization is due to opening of the permeability transition pore rather than to inhibition of electron flux as such. These findings indicate that in UCMD myoblasts the threshold for pore opening is very close to the resting membrane potential, so that even a small depolarization causes permeability transition pore opening and precipitates ATP depletion.
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Affiliation(s)
- Alessia Angelin
- Department of Biomedical Sciences and CNR Institute of Neuroscience, University of Padova, Italy
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High glucose induces adipogenic differentiation of muscle-derived stem cells. Proc Natl Acad Sci U S A 2008; 105:1226-31. [PMID: 18212116 DOI: 10.1073/pnas.0711402105] [Citation(s) in RCA: 209] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Regeneration of mesenchymal tissues depends on a resident stem cell population, that in most cases remains elusive in terms of cellular identity and differentiation signals. We here show that primary cell cultures derived from adipose tissue or skeletal muscle differentiate into adipocytes when cultured in high glucose. High glucose induces ROS production and PKCbeta activation. These two events appear crucial steps in this differentiation process that can be directly induced by oxidizing agents and inhibited by PKCbeta siRNA silencing. The differentiated adipocytes, when implanted in vivo, form viable and vascularized adipose tissue. Overall, the data highlight a previously uncharacterized differentiation route triggered by high glucose that drives not only resident stem cells of the adipose tissue but also uncommitted precursors present in muscle cells to form adipose depots. This process may represent a feed-forward cycle between the regional increase in adiposity and insulin resistance that plays a key role in the pathogenesis of diabetes mellitus.
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Fiorotto R, Spirlì C, Fabris L, Cadamuro M, Okolicsanyi L, Strazzabosco M. Ursodeoxycholic acid stimulates cholangiocyte fluid secretion in mice via CFTR-dependent ATP secretion. Gastroenterology 2007; 133:1603-13. [PMID: 17983806 DOI: 10.1053/j.gastro.2007.08.071] [Citation(s) in RCA: 93] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/26/2006] [Accepted: 07/26/2007] [Indexed: 12/02/2022]
Abstract
BACKGROUND & AIMS Cholangiopathies are characterized by impaired cholangiocyte secretion. Ursodeoxycholic acid (UDCA) is widely used for cholangiopathy treatment, but its effects on cholangiocyte secretory functions remain unclear and are the subject of this study. METHODS Polarized mouse cholangiocytes in tubular (isolated bile-duct units [IBDU]) or monolayer configuration were obtained from wild-type (WT) and B6-129-Cftr(tm1Kth) and Cftr(tm1Unc) mice that are defective in CFTR, an adenosine 3',5'-cyclic monophosphate (cAMP)-stimulated Cl(-) channel expressed in cholangiocytes. Fluid secretion was assessed by video-optical planimetry, Cl(-) and Ca(2+) efflux by microfluorimetry (6-methoxy-N-ethylquinolinium chloride, fura-2, and fluo-4), adenosine triphosphate (ATP) secretion by luciferin-luciferase assay, and protein kinase C (PKC) by Western blot. RESULTS UDCA stimulated fluid secretion and Cl(-) efflux in WT-IBDU but not in CFTR-KO-IBDU or in WT-IBDU exposed to CFTR inhibitors. UDCA did not affect intracellular cAMP levels but increased [Ca(2+)]i in WT and not in CFTR-KO cholangiocytes. UDCA stimulated apical ATP secretion in WT but not in CFTR-KO cholangiocytes. UDCA-stimulated [Ca(2+)]i increase was inhibited by suramin, a purinergic 2Y-receptor inhibitor. UDCA stimulated the translocation of PKC-alpha and PKC-epsilon to the plasma membrane. UDCA-stimulated secretion was inhibited by 2-bis(2-aminophenoxy)-ethane-N,N,N',N'-tetraacetic acid and by phospholipase C and PKC inhibitors. UDCA increased ATP output in isolated perfused livers from WT but not from CFTR-KO mice. CONCLUSIONS Our data indicate that UDCA stimulates a CFTR-dependent apical ATP release in cholangiocytes. Secreted ATP activates purinergic 2Y receptors, and, through [Ca(2+)]i increase and PKC activation stimulates Cl(-) efflux and fluid secretion. These data support the concept that CFTR plays a role in modulating purinergic signaling in secretory epithelia and suggest a novel mechanism explaining the choleretic effect of UDCA.
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Affiliation(s)
- Romina Fiorotto
- Department of Internal Medicine, Section of Digestive Diseases, Yale University School of Medicine and Liver Center, New Haven, Connecticut, USA
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Abstract
Major modifications in energy homeostasis occur in skeletal muscle during exercise. Emerging evidence suggests that changes in energy homeostasis take part in the regulation of gene expression and contribute to muscle plasticity. A number of energy-sensing molecules have been shown to sense variations in energy homeostasis and trigger regulation of gene expression. The AMP-activated protein kinase, hypoxia-inducible factor 1, peroxisome proliferator-activated receptors, and Sirt1 proteins all contribute to altering skeletal muscle gene expression by sensing changes in the concentrations of AMP, molecular oxygen, intracellular free fatty acids, and NAD+, respectively. These molecules may therefore sense information relating to the intensity, duration, and frequency of muscle exercise. Mitochondria also contribute to the overall response, both by modulating the response of energy-sensing molecules and by generating their own signals. This review seeks to examine our current understanding of the roles that energy-sensing molecules and mitochondria can play in the regulation of gene expression in skeletal muscle.
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Affiliation(s)
- Damien Freyssenet
- Unité Physiologie et Physiopathologie de l'Exercice et Handicap, EA3062, Université Jean Monnet, Saint-Etienne Cedex 2, France.
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Rutter GA, Tsuboi T, Ravier MA. Ca2+ microdomains and the control of insulin secretion. Cell Calcium 2006; 40:539-51. [PMID: 17030367 DOI: 10.1016/j.ceca.2006.08.015] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2006] [Accepted: 08/23/2006] [Indexed: 11/19/2022]
Abstract
Nutrient-induced increases in intracellular free Ca(2+) concentrations are the key trigger for insulin release from pancreatic islet beta-cells. These Ca(2+) changes are tightly regulated temporally, occurring as Ca(2+) influx-dependent baseline oscillations. We explore here the concept that locally high [Ca(2+)] concentrations (i.e. Ca(2+) microdomains) may control exocytosis via the recruitment of key effector proteins to sites of exocytosis. Importantly, recent advances in the development of organelle- and membrane-targeted green fluorescent protein (GFP-) or aequorin-based Ca(2+) indicators, as well as in rapid imaging techniques, are providing new insights into the potential role of these Ca(2+) microdomains in beta-cells. We summarise here some of the evidence indicating that Ca(2+) microdomains beneath the plasma membrane and at the surface of large dense core vesicles may be important in the normal regulation of insulin secretion, and may conceivably contribute to "ATP-sensitive K(+)-channel independent" effects of glucose. We also discuss evidence that, in contrast to certain non-excitable cells, direct transfer of Ca(2+) from the ER to mitochondria via localised physical contacts between these organelles is relatively less important for efficient mitochondrial Ca(2+) uptake in beta-cells. Finally, we discuss evidence from single cell imaging that increases in cytosolic Ca(2+) are not required for the upstroke of oscillations in mitochondrial redox state, but may underlie the reoxidation process.
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Affiliation(s)
- Guy A Rutter
- Department of Cell Biology, Division of Medicine, Imperial College London, Sir Alexander Fleming Building, London, UK.
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Rizzuto R, Pozzan T. Microdomains of intracellular Ca2+: molecular determinants and functional consequences. Physiol Rev 2006; 86:369-408. [PMID: 16371601 DOI: 10.1152/physrev.00004.2005] [Citation(s) in RCA: 876] [Impact Index Per Article: 48.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Calcium ions are ubiquitous and versatile signaling molecules, capable of decoding a variety of extracellular stimuli (hormones, neurotransmitters, growth factors, etc.) into markedly different intracellular actions, ranging from contraction to secretion, from proliferation to cell death. The key to this pleiotropic role is the complex spatiotemporal organization of the [Ca(2+)] rise evoked by extracellular agonists, which allows selected effectors to be recruited and specific actions to be initiated. In this review, we discuss the structural and functional bases that generate the subcellular heterogeneity in cellular Ca(2+) levels at rest and under stimulation. This complex choreography requires the concerted action of many different players; the central role is, of course, that of the calcium ion, with the main supporting characters being all the entities responsible for moving Ca(2+) between different compartments, while the cellular architecture provides a determining framework within which all the players have their exits and their entrances. In particular, we concentrate on the molecular mechanisms that lead to the generation of cytoplasmic Ca(2+) microdomains, focusing on their different subcellular location, mechanism of generation, and functional role.
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Affiliation(s)
- Rosario Rizzuto
- Department of Experimental and Diagnostic Medicine, and Interdisciplinary Center for the Study of Inflammation, University of Ferrara, Ferrara, Italy
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Shkryl VM, Shirokova N. Transfer and Tunneling of Ca2+ from Sarcoplasmic Reticulum to Mitochondria in Skeletal Muscle. J Biol Chem 2006; 281:1547-54. [PMID: 16216882 DOI: 10.1074/jbc.m505024200] [Citation(s) in RCA: 82] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The role of mitochondrial Ca2+ transport in regulating intracellular Ca2+ signaling and mitochondrial enzymes involved in energy metabolism is widely recognized in many tissues. However, the ability of skeletal muscle mitochondria to sequester Ca2+ released from the sarcoplasmic reticulum (SR) during the muscle contraction-relaxation cycle is still disputed. To assess the functional cross-talk of Ca2+ between SR and mitochondria, we examined the mutual relationship connecting cytosolic and mitochondrial Ca2+ dynamics in permeabilized skeletal muscle fibers. Cytosolic and mitochondrial Ca2+ transients were recorded with digital photometry and confocal microscopy using fura-2 and mag-rhod-2, respectively. In the presence of 0.5 mM slow Ca2+ buffer (EGTA (ethylene glycolbis(2-aminoethylether)-N,N,N',N'-tetraacetic acid)), application of caffeine induced a synchronized increase in both cytosolic and mitochondrial [Ca2+]. 5 mM fast Ca2+ buffer (BAPTA (1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid)) nearly eliminated caffeine-induced increases in [Ca2+]c but only partially decreased the amplitude of mitochondrial Ca2+ transients. Confocal imaging revealed that in EGTA, almost all mitochondria picked up Ca2+ released from the SR by caffeine, whereas only about 70% of mitochondria did so in BAPTA. Taken together, these results indicated that a subpopulation of mitochondria is in close functional and presumably structural proximity to the SR, giving rise to subcellular microdomains in which Ca2+ has preferential access to the juxtaposed organelles.
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Affiliation(s)
- Vyacheslav M Shkryl
- Department of Pharmacology and Physiology, University of Medicine and Dentistry of New Jersey, New Jersey Medical School, Newark, New Jersey 07103, USA
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Abstract
The development of targeted probes (based on the molecular engineering of luminescent or fluorescent proteins) has allowed the specific measurement of [Ca2+] in intracellular organelles or cytoplasmic subdomains. This approach gave novel information on different aspects of cellular Ca2+ homeostasis. Regarding mitochondria, it was possible to demonstrate that, upon physiological stimulation of cells, Ca2+ is rapidly accumulated in the matrix. We will discuss the basic characteristics of this process, its role in modulating physiological and pathological events, such as the regulation of aerobic metabolism and the induction of cell death, and new insight into the regulatory mechanisms operating in vivo.
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Affiliation(s)
- Sara Leo
- Department of Experimental and Diagnostic Medicine, Section of General Pathology, and Interdisciplinary Center for the Study of Inflammation (ICSI), University of Ferrara, Italy
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