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Hagiwara H, Watanabe M, Fujioka Y, Kadosaka T, Koizumi T, Koya T, Nakao M, Kamada R, Temma T, Okada K, Moreno JA, Kwon O, Sabe H, Ohba Y, Anzai T. Stimulation of the mitochondrial calcium uniporter mitigates chronic heart failure-associated ventricular arrhythmia in mice. Heart Rhythm 2022; 19:1725-1735. [PMID: 35660475 PMCID: PMC10746330 DOI: 10.1016/j.hrthm.2022.05.034] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/13/2021] [Revised: 05/02/2022] [Accepted: 05/24/2022] [Indexed: 11/15/2022]
Abstract
BACKGROUND An aberrant increase in the diastolic calcium concentration ([Ca2+]i) level is a hallmark of heart failure (HF) and the cause of delayed afterdepolarization and ventricular arrhythmia (VA). Although mitochondria play a role in regulating [Ca2+]i, whether they can compensate for the [Ca2+]i abnormality in ventricular myocytes is unknown. OBJECTIVE The purpose of this study was to investigate whether enhanced Ca2+ uptake of mitochondria may compensate for an abnormal increase in the [Ca2+]i of ventricular myocytes in HF to effectively mitigate VA. METHODS We used a HF mouse model in which myocardial infarction was induced by permanent left anterior descending coronary artery ligation. The mitochondrial Ca2+ uniporter was stimulated by kaempferol. Ca2+ dynamics and membrane potential were measured using an epifluorescence microscope, a confocal microscope, and the perforated patch-clamp technique. VA was induced in Langendorff-perfused hearts, and hemodynamic parameters were measured using a microtip transducer catheter. RESULTS Protein expression of the mitochondrial Ca2+ uniporter, as assessed by its subunit expression, did not change between HF and sham mice. Treatment of cardiomyocytes with kaempferol, isolated from HF mice 28 days after coronary ligation, reduced the appearance of aberrant diastolic [Ca2+]i waves and sparks and spontaneous action potentials. Kaempferol effectively reduced VA occurring in Langendorff-perfused hearts. Intravenous administration of kaempferol did not markedly affect left ventricular hemodynamic parameters. CONCLUSION The effects of kaempferol in HF of mice implied that mitochondria may have the potential to compensate for abnormal [Ca2+]i. Mechanisms involved in mitochondrial Ca2+ uptake may provide novel targets for treatment of HF-associated VA.
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Affiliation(s)
- Hikaru Hagiwara
- Department of Cardiovascular Medicine, Faculty of Medicine and Graduate School of Medicine, Hokkaido University, Sapporo, Japan
| | - Masaya Watanabe
- Department of Cardiovascular Medicine, Faculty of Medicine and Graduate School of Medicine, Hokkaido University, Sapporo, Japan.
| | - Yoichiro Fujioka
- Department of Cell Physiology, Faculty of Medicine and Graduate School of Medicine, Hokkaido University, Sapporo, Japan
| | - Takahide Kadosaka
- Department of Cardiovascular Medicine, Faculty of Medicine and Graduate School of Medicine, Hokkaido University, Sapporo, Japan
| | - Takuya Koizumi
- Department of Cardiovascular Medicine, Faculty of Medicine and Graduate School of Medicine, Hokkaido University, Sapporo, Japan
| | - Taro Koya
- Department of Cardiovascular Medicine, Faculty of Medicine and Graduate School of Medicine, Hokkaido University, Sapporo, Japan
| | - Motoki Nakao
- Department of Cardiovascular Medicine, Faculty of Medicine and Graduate School of Medicine, Hokkaido University, Sapporo, Japan
| | - Rui Kamada
- Department of Cardiovascular Medicine, Faculty of Medicine and Graduate School of Medicine, Hokkaido University, Sapporo, Japan
| | - Taro Temma
- Department of Cardiovascular Medicine, Faculty of Medicine and Graduate School of Medicine, Hokkaido University, Sapporo, Japan
| | - Kazufumi Okada
- Data Science Center, Promotion Unit, Institute of Health Science Innovation for Medical Care, Hokkaido University Hospital, Sapporo, Japan
| | - Jose Antonio Moreno
- Department of Chemistry and Biochemistry, University of California Los Angeles, Los Angeles, California
| | - Ohyun Kwon
- Department of Chemistry and Biochemistry, University of California Los Angeles, Los Angeles, California
| | - Hisakata Sabe
- Department of Molecular Biology, Faculty of Medicine and Graduate School of Medicine, Hokkaido University, Sapporo, Japan
| | - Yusuke Ohba
- Department of Cell Physiology, Faculty of Medicine and Graduate School of Medicine, Hokkaido University, Sapporo, Japan
| | - Toshihisa Anzai
- Department of Cardiovascular Medicine, Faculty of Medicine and Graduate School of Medicine, Hokkaido University, Sapporo, Japan
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Han S, Zhao F, Hsia J, Ma X, Liu Y, Torres S, Fujioka H, Zhu X. The role of Mfn2 in the structure and function of endoplasmic reticulum-mitochondrial tethering in vivo. J Cell Sci 2021; 134:269077. [PMID: 34110411 DOI: 10.1242/jcs.253443] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2020] [Accepted: 05/17/2021] [Indexed: 12/12/2022] Open
Abstract
Mitochondria-endoplasmic reticulum contacts (MERCs) play an essential role in multiple cell physiological processes. Although Mfn2 was the first protein implicated in the formation of MERCs, there is debate as to whether it acts as a tether or antagonizer, largely based on in vitro studies. To understand the role of Mfn2 in MERCs in vivo, we characterized ultrastructural and biochemical changes of MERCs in pyramidal neurons of hippocampus in Mfn2 conditional knockout mice and in Mfn2 overexpressing mice, and found that Mfn2 ablation caused reduced close contacts, whereas Mfn2 overexpression caused increased close contacts between the endoplasmic reticulum (ER) and mitochondria in vivo. Functional studies on SH-SY5Y cells with Mfn2 knockout or overexpression demonstrating similar biochemical changes found that mitochondrial calcium uptake along with IP3R3-Grp75 interaction was decreased in Mfn2 knockout cells but increased in Mfn2 overexpressing cells. Lastly, we found Mfn2 knockout decreased and Mfn2 overexpression increased the interaction between the ER-mitochondria tethering pair of VAPB-PTPIP51. In conclusion, our study supports the notion that Mfn2 plays a critical role in ER-mitochondrial tethering and the formation of close contacts in neuronal cells in vivo.
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Affiliation(s)
- Song Han
- Department of Pathology, Case Western Reserve University, Cleveland, OH 44106, USA.,Department of Pathophysiology, School of Basic Medical Sciences, Wuhan University, Wuhan, Hubei 430072, China
| | - Fanpeng Zhao
- Department of Pathology, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Jeffrey Hsia
- Department of Pathology, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Xiaopin Ma
- Department of Pathology, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Yi Liu
- Department of Pathology, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Sandy Torres
- Department of Pathology, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Hisashi Fujioka
- Cryo-Electron Microscopy Core Facility, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Xiongwei Zhu
- Department of Pathology, Case Western Reserve University, Cleveland, OH 44106, USA
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3
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De Mario A, Gherardi G, Rizzuto R, Mammucari C. Skeletal muscle mitochondria in health and disease. Cell Calcium 2021; 94:102357. [PMID: 33550207 DOI: 10.1016/j.ceca.2021.102357] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2020] [Revised: 01/07/2021] [Accepted: 01/07/2021] [Indexed: 12/28/2022]
Abstract
Mitochondrial activity warrants energy supply to oxidative myofibres to sustain endurance workload. The maintenance of mitochondrial homeostasis is ensured by the control of fission and fusion processes and by the mitophagic removal of aberrant organelles. Many diseases are due to or characterized by dysfunctional mitochondria, and altered mitochondrial dynamics or turnover trigger myopathy per se. In this review, we will tackle the role of mitochondrial dynamics, turnover and metabolism in skeletal muscle, both in health and disease.
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Affiliation(s)
- Agnese De Mario
- Department of Biomedical Sciences, University of Padua, Padua, Italy
| | - 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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4
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Holman SP, Lobo AS, Novorolsky RJ, Nichols M, Fiander MDJ, Konda P, Kennedy BE, Gujar S, Robertson GS. Neuronal mitochondrial calcium uniporter deficiency exacerbates axonal injury and suppresses remyelination in mice subjected to experimental autoimmune encephalomyelitis. Exp Neurol 2020; 333:113430. [PMID: 32745471 DOI: 10.1016/j.expneurol.2020.113430] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2020] [Revised: 07/05/2020] [Accepted: 07/28/2020] [Indexed: 12/11/2022]
Abstract
High-capacity mitochondrial calcium (Ca2+) uptake by the mitochondrial Ca2+ uniporter (MCU) is strategically positioned to support the survival and remyelination of axons in multiple sclerosis (MS) by undocking mitochondria, buffering Ca2+ and elevating adenosine triphosphate (ATP) synthesis at metabolically stressed sites. Respiratory chain deficits in MS are proposed to metabolically compromise axon survival and remyelination by suppressing MCU activity. In support of this hypothesis, clinical scores, mitochondrial dysfunction, myelin loss, axon damage and inflammation were elevated while remyelination was blocked in neuronal MCU deficient (Thy1-MCU Def) mice relative to Thy1 controls subjected to experimental autoimmune encephalomyelitis (EAE). At the first sign of walking deficits, mitochondria in EAE/Thy1 axons showed signs of activation. By contrast, cytoskeletal damage, fragmented mitochondria and large autophagosomes were seen in EAE/Thy1-MCU Def axons. As EAE severity increased, EAE/Thy1 axons were filled with massively swollen mitochondria with damaged cristae while EAE/Thy1-MCU Def axons were riddled with late autophagosomes. ATP concentrations and mitochondrial gene expression were suppressed while calpain activity, autophagy-related gene mRNA levels and autophagosome marker (LC3) co-localization in Thy1-expressing neurons were elevated in the spinal cords of EAE/Thy1-MCU Def compared to EAE/Thy1 mice. These findings suggest that MCU inhibition contributes to axonal damage that drives MS progression.
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Affiliation(s)
- Scott P Holman
- Department of Pharmacology, Brain Repair Centre, Dalhousie University, 1348 Summer Street, Life Sciences Research Institute, North Tower, Halifax B3H 4R2, Canada; Faculty of Medicine, Dalhousie University, 1348 Summer Street, Life Sciences Research Institute, North Tower, Halifax B3H 4R2, Canada
| | - Aurelio S Lobo
- Department of Pharmacology, Brain Repair Centre, Dalhousie University, 1348 Summer Street, Life Sciences Research Institute, North Tower, Halifax B3H 4R2, Canada; Faculty of Medicine, Dalhousie University, 1348 Summer Street, Life Sciences Research Institute, North Tower, Halifax B3H 4R2, Canada
| | - Robyn J Novorolsky
- Department of Pharmacology, Brain Repair Centre, Dalhousie University, 1348 Summer Street, Life Sciences Research Institute, North Tower, Halifax B3H 4R2, Canada; Faculty of Medicine, Dalhousie University, 1348 Summer Street, Life Sciences Research Institute, North Tower, Halifax B3H 4R2, Canada
| | - Matthew Nichols
- Department of Pharmacology, Brain Repair Centre, Dalhousie University, 1348 Summer Street, Life Sciences Research Institute, North Tower, Halifax B3H 4R2, Canada; Faculty of Medicine, Dalhousie University, 1348 Summer Street, Life Sciences Research Institute, North Tower, Halifax B3H 4R2, Canada
| | - Maximillian D J Fiander
- Department of Pharmacology, Brain Repair Centre, Dalhousie University, 1348 Summer Street, Life Sciences Research Institute, North Tower, Halifax B3H 4R2, Canada; Faculty of Medicine, Dalhousie University, 1348 Summer Street, Life Sciences Research Institute, North Tower, Halifax B3H 4R2, Canada
| | - Prathyusha Konda
- Department of Pathology, Faculty of Medicine, Dalhousie University, 1348 Summer Street, Life Sciences Research Institute, North Tower, Halifax B3H 4R2, Canada
| | - Barry E Kennedy
- Department of Pathology, Faculty of Medicine, Dalhousie University, 1348 Summer Street, Life Sciences Research Institute, North Tower, Halifax B3H 4R2, Canada
| | - Shashi Gujar
- Department of Pathology, Faculty of Medicine, Dalhousie University, 1348 Summer Street, Life Sciences Research Institute, North Tower, Halifax B3H 4R2, Canada
| | - George S Robertson
- Department of Pharmacology, Brain Repair Centre, Dalhousie University, 1348 Summer Street, Life Sciences Research Institute, North Tower, Halifax B3H 4R2, Canada; Faculty of Medicine, Dalhousie University, 1348 Summer Street, Life Sciences Research Institute, North Tower, Halifax B3H 4R2, Canada; Department of Psychiatry, 5909 Veterans' Memorial Lane, 8th Floor, Abbie J. Lane Memorial Building, QEII Health Sciences Centre, Halifax B3H 2E2, Canada.
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5
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Ortiz-Jiménez DJ, López-Aquino CM, Flores-Herrera C, Preciado-Linares G, Gonzalez-Vizueth I, García-Arrazola R, Araiza-Olivera D, Gutiérrez-Aguilar M. A simple method for mitochondrial respiration and calcium uptake assessment in pollen tubes. MethodsX 2019; 6:1741-1746. [PMID: 31406686 PMCID: PMC6682373 DOI: 10.1016/j.mex.2019.07.023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2019] [Accepted: 07/19/2019] [Indexed: 11/19/2022] Open
Abstract
Key mitochondrial processes are known to be widely conserved throughout the eukaryotic domain. However, the scarce availability of working materials may restrict the assessment of such mitochondrial activities in several working models. Pollen tube mitochondrial studies represent one example of this, where tests have been often restricted due the physical impossibility of performing experiments with isolated mitochondria in enough quantities. Here we detail a method to measure in situ mitochondrial respiratory chain activity and calcium transport in tobacco pollen tubes. •Digitonin-mediated plasmalemma permeabilization allows efficient assessment of mitochondrial respiration and calcium uptake.•This method allows quick, reliable and portable measurements from low to high cellular densities, versus methods requiring intracellular calcium reporters.
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Affiliation(s)
- Diana J. Ortiz-Jiménez
- Departamento de Bioquímica, Facultad de Química, Universidad Nacional Autónoma de México, Ciudad Universitaria, 04510, México City, Mexico
| | - Casandra M. López-Aquino
- Departamento de Bioquímica, Facultad de Química, Universidad Nacional Autónoma de México, Ciudad Universitaria, 04510, México City, Mexico
| | - Cesar Flores-Herrera
- Departamento de Bioquímica, Facultad de Química, Universidad Nacional Autónoma de México, Ciudad Universitaria, 04510, México City, Mexico
| | - Gisela Preciado-Linares
- Departamento de Bioquímica, Facultad de Química, Universidad Nacional Autónoma de México, Ciudad Universitaria, 04510, México City, Mexico
| | - Israel Gonzalez-Vizueth
- Departamento de Bioquímica, Facultad de Química, Universidad Nacional Autónoma de México, Ciudad Universitaria, 04510, México City, Mexico
| | - Roeb García-Arrazola
- Departamento de Alimentos y Biotecnología, Facultad de Química, UNAM, Circuito Exterior, Ciudad Universitaria 04510. México City, Mexico
| | - Daniela Araiza-Olivera
- Instituto de Química, Universidad Nacional Autónoma de México, Circuito Exterior, Ciudad Universitaria 04510. México City, Mexico
| | - Manuel Gutiérrez-Aguilar
- Departamento de Bioquímica, Facultad de Química, Universidad Nacional Autónoma de México, Ciudad Universitaria, 04510, México City, Mexico
- Corresponding author.
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6
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Boyman L, Williams GSB, Wescott AP, Leach JB, Kao JPY, Lederer WJ. Real-time local oxygen measurements for high resolution cellular imaging. J Mol Cell Cardiol 2018; 127:97-104. [PMID: 30528909 DOI: 10.1016/j.yjmcc.2018.11.021] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/06/2018] [Revised: 11/04/2018] [Accepted: 11/29/2018] [Indexed: 12/31/2022]
Abstract
Single-cell metabolic investigations are hampered by the absence of flexible tools to measure local partial pressure of O2 (pO2) at high spatial-temporal resolution. To this end, we developed an optical sensor capable of measuring local pericellular pO2 for subcellular resolution measurements with confocal imaging while simultaneously carrying out electrophysiological and/or chemo-mechanical single cell experiments. Here we present the OxySplot optrode, a ratiometric fluorescent O2-micro-sensor created by adsorbing O2-sensitive and O2-insensitive fluorophores onto micro-particles of silica. To protect the OxySplot optrode from the components and reactants of liquid environment without compromising access to O2, the micro-particles are coated with an optically clear silicone polymer (PDMS, polydimethylsiloxane). The PDMS coated OxySplot micro-particles are used alone or in a thin (~50 μm) PDMS layer of arbitrary shape referred to as the OxyMat. Additional top coatings on the OxyMat (e.g., fibronectin, laminin, polylysine, special photoactivatable surfaces etc.) facilitate adherence of cells. The OxySplots report the cellular pO2 and micro-gradients of pO2 without disrupting the flow of extracellular solutions or interfering with patch-clamp pipettes, mechanical attachments, and micro-superfusion. Since OxySplots and a cell can be imaged and spatially resolved, calibrated changes of pO2 and intracellular events can be imaged simultaneously. In addition, the response-time (t0.5 = 0.7 s, 0-160 mmHg) of OxySplots is ~100 times faster than amperometric Clark-type polarization microelectrodes. Two usage example of OxySplots with cardiomyocytes show (1) OxySplots measuring pericellular pO2 while tetramethylrhodamine methyl-ester (TMRM) was used to measure mitochondrial membrane potential (ΔΨm); and (2) OxySplots measuring pO2 during ischemia and reperfusion while rhod-2 was used to measure cytosolic [Ca2+]i levels simultaneously. The OxySplot/OxyMat optrode system provides an affordable and highly adaptable optical sensor system for monitoring pO2 with a diverse array of imaging systems, including high-speed, high-resolution confocal microscopes while physiological features are measured simultaneously.
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Affiliation(s)
- Liron Boyman
- Center for Biomedical Engineering and Technology, University of Maryland School of Medicine, Baltimore, MD 21201, USA; Department of Physiology, University of Maryland School of Medicine, Baltimore, MD 21201, USA
| | - George S B Williams
- Center for Biomedical Engineering and Technology, University of Maryland School of Medicine, Baltimore, MD 21201, USA; Department of Physiology, University of Maryland School of Medicine, Baltimore, MD 21201, USA
| | - Andrew P Wescott
- Center for Biomedical Engineering and Technology, University of Maryland School of Medicine, Baltimore, MD 21201, USA; Department of Physiology, University of Maryland School of Medicine, Baltimore, MD 21201, USA
| | - Jennie B Leach
- Department of Chemical, Biochemical and Environmental Engineering, University of Maryland Baltimore County, Baltimore, MD 21250, USA
| | - Joseph P Y Kao
- Center for Biomedical Engineering and Technology, University of Maryland School of Medicine, Baltimore, MD 21201, USA; Department of Physiology, University of Maryland School of Medicine, Baltimore, MD 21201, USA
| | - W Jonathan Lederer
- Center for Biomedical Engineering and Technology, University of Maryland School of Medicine, Baltimore, MD 21201, USA; Department of Physiology, University of Maryland School of Medicine, Baltimore, MD 21201, USA.
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7
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Wu G, Li S, Zong G, Liu X, Fei S, Shen L, Guan X, Yang X, Shen Y. Single channel recording of a mitochondrial calcium uniporter. Biochem Biophys Res Commun 2018; 496:127-132. [PMID: 29307826 DOI: 10.1016/j.bbrc.2018.01.010] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2017] [Accepted: 01/02/2018] [Indexed: 01/13/2023]
Abstract
Mitochondrial calcium uniporter (MCU) is the pore-forming subunit of the entire uniporter complex and plays an important role in mitochondrial calcium uptake. However, the single channel recording of MCU remains controversial. Here, we expressed and purified different MCU proteins and then reconstituted them into planar lipid bilayers for single channel recording. We showed that MCU alone from Pyronema omphalodes (pMCU) is active with prominent single channel Ca2+ currents. In sharp contrast, MCU alone from Homo sapiens (hMCU) is inactive. The essential MCU regulator (EMRE) activates hMCU, and therefore, the complex (hMCU-hEMRE) shows prominent single channel Ca2+ currents. These single channel currents are sensitive to the specific MCU inhibitor Ruthenium Red. Our results clearly demonstrate that active MCU can conduct large amounts of calcium into the mitochondria.
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Affiliation(s)
- Guangyan Wu
- State Key Laboratory of Medicinal Chemical Biology and College of Life Sciences, Nankai University, 94 Weijin Road, Tianjin 300071, China
| | - Shunjin Li
- State Key Laboratory of Medicinal Chemical Biology and College of Life Sciences, Nankai University, 94 Weijin Road, Tianjin 300071, China
| | - Guangning Zong
- State Key Laboratory of Medicinal Chemical Biology and College of Life Sciences, Nankai University, 94 Weijin Road, Tianjin 300071, China; College of Pharmacy, Nankai University, 38 Tongyan Road, Tianjin 300350, China
| | - Xiaofen Liu
- State Key Laboratory of Medicinal Chemical Biology and College of Life Sciences, Nankai University, 94 Weijin Road, Tianjin 300071, China
| | - Shuang Fei
- College of Pharmacy, Nankai University, 38 Tongyan Road, Tianjin 300350, China
| | - Linda Shen
- Tianjin Nankai High School, 22 Nankaisima Road, Tianjin 300100, China
| | - Xiangchen Guan
- State Key Laboratory of Medicinal Chemical Biology and College of Life Sciences, Nankai University, 94 Weijin Road, Tianjin 300071, China
| | - Xue Yang
- State Key Laboratory of Medicinal Chemical Biology and College of Life Sciences, Nankai University, 94 Weijin Road, Tianjin 300071, China.
| | - Yuequan Shen
- State Key Laboratory of Medicinal Chemical Biology and College of Life Sciences, Nankai University, 94 Weijin Road, Tianjin 300071, China; Synergetic Innovation Center of Chemical Science and Engineering, 94 Weijin Road, Tianjin 300071, China.
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8
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Mammucari C, Raffaello A, Vecellio Reane D, Rizzuto R. Molecular structure and pathophysiological roles of the Mitochondrial Calcium Uniporter. Biochim Biophys Acta 2016; 1863:2457-64. [PMID: 26968367 DOI: 10.1016/j.bbamcr.2016.03.006] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/10/2015] [Revised: 02/24/2016] [Accepted: 03/01/2016] [Indexed: 01/21/2023]
Abstract
Mitochondrial Ca(2+) uptake regulates a wide array of cell functions, from stimulation of aerobic metabolism and ATP production in physiological settings, to induction of cell death in pathological conditions. The molecular identity of the Mitochondrial Calcium Uniporter (MCU), the highly selective channel responsible for Ca(2+) entry through the IMM, has been described less than five years ago. Since then, research has been conducted to clarify the modulation of its activity, which relies on the dynamic interaction with regulatory proteins, and its contribution to the pathophysiology of organs and tissues. Particular attention has been placed on characterizing the role of MCU in cardiac and skeletal muscles. In this review we summarize the molecular structure and regulation of the MCU complex in addition to its pathophysiological role, with particular attention to striated muscle tissues. This article is part of a Special Issue entitled: Mitochondrial Channels edited by Pierre Sonveaux, Pierre Maechler and Jean-Claude Martinou.
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Affiliation(s)
| | - Anna Raffaello
- Department of Biomedical Sciences, University of Padua, 35131, Italy.
| | | | - Rosario Rizzuto
- Department of Biomedical Sciences, University of Padua, 35131, Italy; Neuroscience Institute, National Research Council, Padua 35131, Italy.
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9
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Ainbinder A, Boncompagni S, Protasi F, Dirksen RT. Role of Mitofusin-2 in mitochondrial localization and calcium uptake in skeletal muscle. Cell Calcium 2015; 57:14-24. [PMID: 25477138 DOI: 10.1016/j.ceca.2014.11.002] [Citation(s) in RCA: 77] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2014] [Accepted: 11/04/2014] [Indexed: 12/21/2022]
Abstract
As muscle contraction requires ATP and Ca(2+), skeletal muscle function is highly dependent on communication between two major intracellular organelles: mitochondria and sarcoplasmic reticulum (SR). In adult skeletal muscle, mitochondria located within the I-band of the sarcomere are connected to the SR by small ∼10 nm electron dense tethers that bridge the outer mitochondrial membrane to the region of SR that is ∼130 nm from the site of Ca(2+) release. However, the molecular composition of tethers and their precise impact on mitochondrial Ca(2+) uptake in skeletal muscle is unclear. Mitofusin-2 (Mfn2) is a transmembrane GTPase present in both mitochondria and ER/SR membranes that forms trans-dimers and participates in mitochondrial fusion. Here we evaluated the role Mfn2 plays in mitochondrial morphology, localization, and functional SR-mitochondrial Ca(2+) crosstalk in adult skeletal muscle. Compared to a non-targeting (CTRL) siRNA, in vivo electroporation of 400 nM Mfn2 siRNA (Mfn2 KD) into mouse footpads resulted in a marked acute reduction (67±3%) in Mfn2 protein levels in flexor digitorum brevis (FDB) muscles that occurred without a change in other key Ca(2+) regulatory proteins. Electron microscopy analyses revealed that Mfn2 knockdown resulted in a change in mitochondria morphology and mis-localization of some mitochondria from the I-band to the A-band region of the sarcomere. To assess the role of Mfn2 in SR-mitochondrial crosstalk, we measured mitochondrial Ca(2+) uptake and myoplasmic Ca(2+) transients with rhod-2 and mag-fluo-4, respectively, during repetitive high frequency tetanic stimulation (5×100 Hz tetani, 500 ms/tetani, 0.2 duty cycle) in CTRL and Mfn2 KD fibers. Mitochondrial Ca(2+) uptake during repetitive tetanic stimulation was significantly reduced (40%) in Mfn2 KD FDB fibers, which was accompanied by a parallel elevation in the global electrically evoked myoplasmic Ca(2+) transient. Mfn2 KD also resulted in a reduction of the mitochondrial membrane potential, which contributed to the observed decrease in activity-dependent mitochondrial Ca(2+) uptake. Consistent with this idea, a similar decrease in mitochondrial Ca(2+) uptake was also observed in wild type fibers following a comparable reduction in mitochondrial membrane potential induced by acute exposure to a low concentration (50 nM) of carbonylcyanide-p-trifluoromethoxyphenylhydrazone (FCCP). In addition, both global and mitochondrial Ca(2+) transients during repetitive tetanic stimulation were similarly reduced by both slow (EGTA) and fast (BAPTA) Ca(2+) chelating agents. Together, these results indicate that Mfn2 promotes proper mitochondrial morphology, localization, and membrane potential required for optimal activity-dependent mitochondrial Ca(2+) uptake and buffering of the global myoplasmic Ca(2+) transient in adult skeletal muscle.
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10
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Gong G, Liu X, Wang W. Regulation of metabolism in individual mitochondria during excitation-contraction coupling. J Mol Cell Cardiol 2014; 76:235-46. [PMID: 25252178 DOI: 10.1016/j.yjmcc.2014.09.012] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/09/2014] [Accepted: 09/11/2014] [Indexed: 01/03/2023]
Abstract
The heart is an excitable organ that undergoes spontaneous force generation and relaxation cycles driven by excitation-contraction (EC) coupling. A fraction of the oscillating cytosolic Ca(2+) during each heartbeat is taken up by mitochondria to stimulate mitochondrial metabolism, the major source of energy in the heart. Whether the mitochondrial metabolism is regulated individually during EC coupling and whether this heterogeneous regulation bears any physiological or pathological relevance have not been studied. Here, we developed a novel approach to determine the regulation of individual mitochondrial metabolism during cardiac EC coupling. Through monitoring superoxide flashes, which are stochastic and bursting superoxide production events arising from increased metabolism in individual mitochondria, we found that EC coupling stimulated the metabolism in individual mitochondria as indicated by significantly increased superoxide flash activity during electrical stimulation of the cultured intact myocytes or perfused heart. Mechanistically, cytosolic calcium transients promoted individual mitochondria to take up calcium via mitochondrial calcium uniporter, which subsequently triggered transient opening of the permeability transition pore and stimulated metabolism and bursting superoxide flash in that mitochondrion. The bursting superoxide, in turn, promoted local calcium release. In the early stage of heart failure, EC coupling regulation of superoxide flashes was compromised. This study highlights the heterogeneity in the regulation of cardiac mitochondrial metabolism, which may contribute to local redox signaling.
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Affiliation(s)
- Guohua Gong
- Mitochondria and Metabolism Center, Department of Anesthesiology and Pain Medicine, University of Washington, Seattle, WA 98109, USA
| | - Xiaoyun Liu
- Mitochondria and Metabolism Center, Department of Anesthesiology and Pain Medicine, University of Washington, Seattle, WA 98109, USA; Department of Neurology, Second Hospital of Hebei Medical University, Shijiazhuang, Hebei 050000, China
| | - Wang Wang
- Mitochondria and Metabolism Center, Department of Anesthesiology and Pain Medicine, University of Washington, Seattle, WA 98109, USA.
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He J, Shi W, Guo Y, Chai Z. ERp57 modulates mitochondrial calcium uptake through the MCU. FEBS Lett 2014; 588:2087-94. [PMID: 24815697 DOI: 10.1016/j.febslet.2014.04.041] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2014] [Revised: 04/23/2014] [Accepted: 04/24/2014] [Indexed: 10/25/2022]
Abstract
ERp57 participates in the regulation of calcium homeostasis. Although ERp57 modulates calcium flux across the plasma membrane and the endoplasmic reticulum membrane, its functions on mitochondria are largely unknown. Here, we found that ERp57 can regulate the expression of the mitochondrial calcium uniporter (MCU) and modulate mitochondrial calcium uptake. In ERp57-silenced HeLa cells, MCU was downregulated, and the mitochondrial calcium uptake was inhibited, consistent with the effect of MCU knockdown. When MCU was re-expressed in the ERp57 knockdown cells, mitochondrial calcium uptake was restored. Thus, ERp57 is a potent regulator of mitochondrial calcium homeostasis.
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Affiliation(s)
- Jingquan He
- State Key Laboratory of Biomembrane and Membrane Biotechnology, College of Life Sciences, Peking University, Beijing 100871, China
| | - Weikang Shi
- State Key Laboratory of Biomembrane and Membrane Biotechnology, College of Life Sciences, Peking University, Beijing 100871, China
| | - Yu Guo
- State Key Laboratory of Biomembrane and Membrane Biotechnology, College of Life Sciences, Peking University, Beijing 100871, China
| | - Zhen Chai
- State Key Laboratory of Biomembrane and Membrane Biotechnology, College of Life Sciences, Peking University, Beijing 100871, China.
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