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O'Connor K, Spendiff S, Lochmüller H, Horvath R. Mitochondrial Mutations Can Alter Neuromuscular Transmission in Congenital Myasthenic Syndrome and Mitochondrial Disease. Int J Mol Sci 2023; 24:ijms24108505. [PMID: 37239850 DOI: 10.3390/ijms24108505] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2023] [Revised: 04/28/2023] [Accepted: 05/02/2023] [Indexed: 05/28/2023] Open
Abstract
Congenital myasthenic syndromes (CMS) are a group of rare, neuromuscular disorders that usually present in childhood or infancy. While the phenotypic presentation of these disorders is diverse, the unifying feature is a pathomechanism that disrupts neuromuscular transmission. Recently, two mitochondrial genes-SLC25A1 and TEFM-have been reported in patients with suspected CMS, prompting a discussion about the role of mitochondria at the neuromuscular junction (NMJ). Mitochondrial disease and CMS can present with similar symptoms, and potentially one in four patients with mitochondrial myopathy exhibit NMJ defects. This review highlights research indicating the prominent roles of mitochondria at both the pre- and postsynapse, demonstrating the potential for mitochondrial involvement in neuromuscular transmission defects. We propose the establishment of a novel subcategorization for CMS-mitochondrial CMS, due to unifying clinical features and the potential for mitochondrial defects to impede transmission at the pre- and postsynapse. Finally, we highlight the potential of targeting the neuromuscular transmission in mitochondrial disease to improve patient outcomes.
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Affiliation(s)
- Kaela O'Connor
- Children's Hospital of Eastern Ontario Research Institute, Ottawa, ON K1H 8L1, Canada
- Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, ON K1H 8M5, Canada
- Centre for Neuromuscular Disease, University of Ottawa Brain and Mind Research Institute, Ottawa, ON K1H 8M5, Canada
| | - Sally Spendiff
- Children's Hospital of Eastern Ontario Research Institute, Ottawa, ON K1H 8L1, Canada
| | - Hanns Lochmüller
- Children's Hospital of Eastern Ontario Research Institute, Ottawa, ON K1H 8L1, Canada
- Division of Neurology, Department of Medicine, The Ottawa Hospital, Ottawa, ON K1H 8L6, Canada
- Brain and Mind Research Institute, University of Ottawa, Ottawa, ON K1H 8M5, Canada
- Department of Neuropediatrics and Muscle Disorders, Faculty of Medicine, Medical Center-University of Freiburg, 79104 Freiburg, Germany
- Centro Nacional de Análisis Genómico (CNAG-CRG), Center for Genomic Regulation, Barcelona Institute of Science and Technology (BIST), 08028 Barcelona, Catalonia, Spain
| | - Rita Horvath
- Department of Clinical Neurosciences, University of Cambridge, Cambridge CB3 0FD, UK
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2
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Wang ZW, Riaz S, Niu L. Roles and Sources of Calcium in Synaptic Exocytosis. ADVANCES IN NEUROBIOLOGY 2023; 33:139-170. [PMID: 37615866 DOI: 10.1007/978-3-031-34229-5_6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/25/2023]
Abstract
Calcium ions (Ca2+) play a critical role in triggering neurotransmitter release. The rate of release is directly related to the concentration of Ca2+ at the presynaptic site, with a supralinear relationship. There are two main sources of Ca2+ that trigger synaptic vesicle fusion: influx through voltage-gated Ca2+ channels in the plasma membrane and release from the endoplasmic reticulum via ryanodine receptors. This chapter will cover the sources of Ca2+ at the presynaptic nerve terminal, the relationship between neurotransmitter release rate and Ca2+ concentration, and the mechanisms that achieve the necessary Ca2+ concentrations for triggering synaptic exocytosis at the presynaptic site.
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Affiliation(s)
- Zhao-Wen Wang
- Department of Neuroscience, University of Connecticut School of Medicine, Farmington, CT, USA.
| | - Sadaf Riaz
- Department of Neuroscience, University of Connecticut School of Medicine, Farmington, CT, USA
| | - Longgang Niu
- Department of Neuroscience, University of Connecticut School of Medicine, Farmington, CT, USA
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3
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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:e202213167. [PMID: 35849108 PMCID: PMC9297197 DOI: 10.1085/jgp.202213167] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [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
| | - Lorenzo Marcucci
- Department of Biomedical Sciences, University of Padova, Padova, Italy
- Center for Biosystems Dynamics Research, RIKEN, Suita, Japan
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4
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Lopez-Manzaneda M, Fuentes-Moliz A, Tabares L. Presynaptic Mitochondria Communicate With Release Sites for Spatio-Temporal Regulation of Exocytosis at the Motor Nerve Terminal. Front Synaptic Neurosci 2022; 14:858340. [PMID: 35645766 PMCID: PMC9133601 DOI: 10.3389/fnsyn.2022.858340] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2022] [Accepted: 04/07/2022] [Indexed: 11/13/2022] Open
Abstract
Presynaptic Ca2+ regulation is critical for accurate neurotransmitter release, vesicle reloading of release sites, and plastic changes in response to electrical activity. One of the main players in the regulation of cytosolic Ca2+ in nerve terminals is mitochondria, which control the size and spread of the Ca2+ wave during sustained electrical activity. However, the role of mitochondria in Ca2+ signaling during high-frequency short bursts of action potentials (APs) is not well known. Here, we studied spatial and temporal relationships between mitochondrial Ca2+ (mCa2+) and exocytosis by live imaging and electrophysiology in adult motor nerve terminals of transgenic mice expressing synaptophysin-pHluorin (SypHy). Our results show that hot spots of exocytosis and mitochondria are organized in subsynaptic functional regions and that mitochondria start to uptake Ca2+ after a few APs. We also show that mitochondria contribute to the regulation of the mode of fusion (synchronous and asynchronous) and the kinetics of release and replenishment of the readily releasable pool (RRP) of vesicles. We propose that mitochondria modulate the timing and reliability of neurotransmission in motor nerve terminals during brief AP trains.
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5
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Garbincius JF, Elrod JW. Mitochondrial calcium exchange in physiology and disease. Physiol Rev 2022; 102:893-992. [PMID: 34698550 PMCID: PMC8816638 DOI: 10.1152/physrev.00041.2020] [Citation(s) in RCA: 145] [Impact Index Per Article: 72.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2021] [Revised: 08/16/2021] [Accepted: 10/19/2021] [Indexed: 12/13/2022] Open
Abstract
The uptake of calcium into and extrusion of calcium from the mitochondrial matrix is a fundamental biological process that has critical effects on cellular metabolism, signaling, and survival. Disruption of mitochondrial calcium (mCa2+) cycling is implicated in numerous acquired diseases such as heart failure, stroke, neurodegeneration, diabetes, and cancer and is genetically linked to several inherited neuromuscular disorders. Understanding the mechanisms responsible for mCa2+ exchange therefore holds great promise for the treatment of these diseases. The past decade has seen the genetic identification of many of the key proteins that mediate mitochondrial calcium uptake and efflux. Here, we present an overview of the phenomenon of mCa2+ transport and a comprehensive examination of the molecular machinery that mediates calcium flux across the inner mitochondrial membrane: the mitochondrial uniporter complex (consisting of MCU, EMRE, MICU1, MICU2, MICU3, MCUB, and MCUR1), NCLX, LETM1, the mitochondrial ryanodine receptor, and the mitochondrial permeability transition pore. We then consider the physiological implications of mCa2+ flux and evaluate how alterations in mCa2+ homeostasis contribute to human disease. This review concludes by highlighting opportunities and challenges for therapeutic intervention in pathologies characterized by aberrant mCa2+ handling and by summarizing critical unanswered questions regarding the biology of mCa2+ flux.
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Affiliation(s)
- Joanne F Garbincius
- Center for Translational Medicine, Lewis Katz School of Medicine at Temple University, Philadelphia, Pennsylvania
| | - John W Elrod
- Center for Translational Medicine, Lewis Katz School of Medicine at Temple University, Philadelphia, Pennsylvania
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6
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Lopez-Manzaneda M, Franco-Espin J, Tejero R, Cano R, Tabares L. Calcium is reduced in presynaptic mitochondria of motor nerve terminals during neurotransmission in SMA mice. Hum Mol Genet 2021; 30:629-643. [PMID: 33693569 PMCID: PMC8127408 DOI: 10.1093/hmg/ddab065] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2020] [Revised: 02/21/2021] [Accepted: 02/23/2021] [Indexed: 01/17/2023] Open
Abstract
Spinal muscular atrophy (SMA) is an autosomal recessive degenerative motor neuron disease characterized by symmetrical muscle weakness and atrophy of limb and trunk muscles being the most severe genetic disease in children. In SMA mouse models, motor nerve terminals display neurotransmitter release reduction, endocytosis decrease and mitochondria alterations. The relationship between these changes is, however, not well understood. In the present study, we investigated whether the endocytosis impairment could be related to the functional alteration of the presynaptic mitochondria during action potential (AP) firing. To this aim, we generated a Synaptophysin-pHluorin (SypHy) transgenic mouse, crossed it with Taiwanese SMA mice, and recorded exo- and endocytosis and mitochondria Ca2+ signaling in real-time at ex vivo motor nerve terminals of Taiwanese-SypHy mice. The experiments were performed at the beginning of the motor symptoms to get an integrated view of the nerve terminal’s functional state before degeneration. Our electrophysiological and live imaging results demonstrated that the mitochondria’s capacity to increase matrix-free Ca2+ in SMA mice was significantly limited during nerve AP firing, except when the rate of Ca2+ entry to the cytosol was considerably reduced. These results indicate that both the mitochondrial Ca2+ signaling alterations and the secretion machinery defects are significant players in the dysfunction of the presynaptic terminal in SMA.
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Affiliation(s)
- Mario Lopez-Manzaneda
- Department of Medical Physiology and Biophysics, School of Medicine, University of Seville, 41009 Seville, Spain
| | - Julio Franco-Espin
- Department of Medical Physiology and Biophysics, School of Medicine, University of Seville, 41009 Seville, Spain
| | - Rocio Tejero
- Department of Medical Physiology and Biophysics, School of Medicine, University of Seville, 41009 Seville, Spain
| | - Raquel Cano
- Department of Medical Physiology and Biophysics, School of Medicine, University of Seville, 41009 Seville, Spain
| | - Lucia Tabares
- Department of Medical Physiology and Biophysics, School of Medicine, University of Seville, 41009 Seville, Spain
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7
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Lithium chloride enhances serotonin induced calcium activity in EGFP-GnIH neurons. Sci Rep 2020; 10:13876. [PMID: 32807874 PMCID: PMC7431857 DOI: 10.1038/s41598-020-70710-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2020] [Accepted: 07/20/2020] [Indexed: 11/10/2022] Open
Abstract
Neurons synthesizing gonadotropin-inhibitory hormone (GnIH) have been implicated in the control of reproduction, food intake and stress. Serotonin (5-HT) receptors have been shown in GnIH neurons; however, their functional role in the regulation of GnIH neurons remains to be elucidated. In this study, we measured intracellular calcium ion levels following 5-HT treatment to hypothalamic primary cultures of enhanced fluorescent green protein-tagged GnIH (EGFP-GnIH) neurons from Wistar rat pups of mixed sex. Three days after initial seeding of the primary cultures, the test groups were pre-treated with lithium chloride to selectively inhibit glycogen synthase kinase 3 beta to promote intracellular calcium levels, whereas the control groups received culture medium with no lithium chloride treatment. 24 h later, the cultures were incubated with rhodamine-2AM (rhod-2AM) calcium indicator dye for one hour prior to imaging. 5-HT was added to the culture dishes 5 min after commencement of imaging. Analysis of intracellular calcium levels in EGFP-GnIH neurons showed that pre-treatment with lithium chloride before 5-HT treatment resulted in significant increase in intracellular calcium levels, two times higher than the baseline. This suggests that lithium chloride enhances the responsiveness of GnIH neurons to 5-HT.
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8
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Mancini A, Mazzocchetti P, Sciaccaluga M, Megaro A, Bellingacci L, Beccano-Kelly DA, Di Filippo M, Tozzi A, Calabresi P. From Synaptic Dysfunction to Neuroprotective Strategies in Genetic Parkinson's Disease: Lessons From LRRK2. Front Cell Neurosci 2020; 14:158. [PMID: 32848606 PMCID: PMC7399363 DOI: 10.3389/fncel.2020.00158] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2020] [Accepted: 05/12/2020] [Indexed: 12/11/2022] Open
Abstract
The pathogenesis of Parkinson’s disease (PD) is thought to rely on a complex interaction between the patient’s genetic background and a variety of largely unknown environmental factors. In this scenario, the investigation of the genetic bases underlying familial PD could unveil key molecular pathways to be targeted by new disease-modifying therapies, still currently unavailable. Mutations in the leucine-rich repeat kinase 2 (LRRK2) gene are responsible for the majority of inherited familial PD cases and can also be found in sporadic PD, but the pathophysiological functions of LRRK2 have not yet been fully elucidated. Here, we will review the evidence obtained in transgenic LRRK2 experimental models, characterized by altered striatal synaptic transmission, mitochondrial dysfunction, and α-synuclein aggregation. Interestingly, the processes triggered by mutant LRRK2 might represent early pathological phenomena in the pathogenesis of PD, anticipating the typical neurodegenerative features characterizing the late phases of the disease. A comprehensive view of LRRK2 neuronal pathophysiology will support the possible clinical application of pharmacological compounds targeting this protein, with potential therapeutic implications for patients suffering from both familial and sporadic PD.
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Affiliation(s)
- Andrea Mancini
- Section of Neurology, Department of Medicine, University of Perugia, Perugia, Italy
| | - Petra Mazzocchetti
- Section of Neurology, Department of Medicine, University of Perugia, Perugia, Italy
| | - Miriam Sciaccaluga
- Section of Neurology, Department of Medicine, University of Perugia, Perugia, Italy
| | - Alfredo Megaro
- Section of Neurology, Department of Medicine, University of Perugia, Perugia, Italy
| | - Laura Bellingacci
- Section of Physiology and Biochemistry, Department of Experimental Medicine, University of Perugia, Perugia, Italy
| | - Dayne A Beccano-Kelly
- Oxford Parkinson's Disease Centre, Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
| | | | - Alessandro Tozzi
- Section of Physiology and Biochemistry, Department of Experimental Medicine, University of Perugia, Perugia, Italy
| | - Paolo Calabresi
- Neurologia, Fondazione Policlinico Universitario Agostino Gemelli IRCCS, Rome, Italy.,Neuroscience Department, Università Cattolica del Sacro Cuore, Rome, Italy
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9
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Calió ML, Henriques E, Siena A, Bertoncini CRA, Gil-Mohapel J, Rosenstock TR. Mitochondrial Dysfunction, Neurogenesis, and Epigenetics: Putative Implications for Amyotrophic Lateral Sclerosis Neurodegeneration and Treatment. Front Neurosci 2020; 14:679. [PMID: 32760239 PMCID: PMC7373761 DOI: 10.3389/fnins.2020.00679] [Citation(s) in RCA: 39] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2020] [Accepted: 06/03/2020] [Indexed: 12/11/2022] Open
Abstract
Amyotrophic lateral sclerosis (ALS) is a progressive and devastating multifactorial neurodegenerative disorder. Although the pathogenesis of ALS is still not completely understood, numerous studies suggest that mitochondrial deregulation may be implicated in its onset and progression. Interestingly, mitochondrial deregulation has also been associated with changes in neural stem cells (NSC) proliferation, differentiation, and migration. In this review, we highlight the importance of mitochondrial function for neurogenesis, and how both processes are correlated and may contribute to the pathogenesis of ALS; we have focused primarily on preclinical data from animal models of ALS, since to date no studies have evaluated this link using human samples. As there is currently no cure and no effective therapy to counteract ALS, we have also discussed how improving neurogenic function by epigenetic modulation could benefit ALS. In support of this hypothesis, changes in histone deacetylation can alter mitochondrial function, which in turn might ameliorate cellular proliferation as well as neuronal differentiation and migration. We propose that modulation of epigenetics, mitochondrial function, and neurogenesis might provide new hope for ALS patients, and studies exploring these new territories are warranted in the near future.
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Affiliation(s)
| | - Elisandra Henriques
- Department of Physiological Science, Santa Casa de São Paulo School of Medical Science, São Paulo, Brazil
| | - Amanda Siena
- Department of Physiological Science, Santa Casa de São Paulo School of Medical Science, São Paulo, Brazil
| | - Clélia Rejane Antonio Bertoncini
- CEDEME, Center of Development of Experimental Models for Medicine and Biology, Federal University of São Paulo, São Paulo, Brazil
| | - Joana Gil-Mohapel
- Division of Medical Sciences, Faculty of Medicine, University of Victoria and Island Medical Program, University of British Columbia, Victoria, BC, Canada
| | - Tatiana Rosado Rosenstock
- Department of Physiological Science, Santa Casa de São Paulo School of Medical Science, São Paulo, Brazil
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10
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Steen K, Chen D, Wang F, Majumdar R, Chen S, Kumar S, Lombard DB, Weigert R, Zieman AG, Parent CA, Coulombe PA. A role for keratins in supporting mitochondrial organization and function in skin keratinocytes. Mol Biol Cell 2020; 31:1103-1111. [PMID: 32213122 PMCID: PMC7353162 DOI: 10.1091/mbc.e19-10-0565] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Mitochondria fulfill essential roles in ATP production, metabolic regulation, calcium signaling, generation of reactive oxygen species (ROS), and additional determinants of cellular health. Recent studies have highlighted a role for mitochondria during cell differentiation, including in skin epidermis. The observation of oxidative stress in keratinocytes from Krt16 null mouse skin, a model for pachyonychia congenita (PC)–associated palmoplantar keratoderma, prompted us to examine the role of Keratin (K) 16 protein and its partner K6 in regulating the structure and function of mitochondria. Electron microscopy revealed major anomalies in mitochondrial ultrastructure in late stage, E18.5, Krt6a/Krt6b null embryonic mouse skin. Follow-up studies utilizing biochemical, metabolic, and live imaging readouts showed that, relative to controls, skin keratinocytes null for Krt6a/Krt6b or Krt16 exhibit elevated ROS, reduced mitochondrial respiration, intracellular distribution differences, and altered movement of mitochondria within the cell. These findings highlight a novel role for K6 and K16 in regulating mitochondrial morphology, dynamics, and function and shed new light on the causes of oxidative stress observed in PC and related keratin-based skin disorders.
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Affiliation(s)
- Kaylee Steen
- Department of Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI 48109
| | - Desu Chen
- Laboratory for Cellular and Molecular Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892
| | - Fengrong Wang
- Department of Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI 48109
| | - Ritankar Majumdar
- Department of Pharmacology, University of Michigan Medical School, Ann Arbor, MI 48109
| | - Song Chen
- Department of Pharmacology, University of Michigan Medical School, Ann Arbor, MI 48109
| | - Surinder Kumar
- Department of Pathology, University of Michigan, Ann Arbor, MI 48109
| | - David B Lombard
- Department of Pathology, University of Michigan, Ann Arbor, MI 48109.,Rogel Cancer Center, University of Michigan, Ann Arbor, MI 48109
| | - Roberto Weigert
- Laboratory for Cellular and Molecular Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892
| | - Abigail G Zieman
- Department of Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI 48109
| | - Carole A Parent
- Department of Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI 48109.,Department of Pharmacology, University of Michigan Medical School, Ann Arbor, MI 48109.,Rogel Cancer Center, University of Michigan, Ann Arbor, MI 48109
| | - Pierre A Coulombe
- Department of Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI 48109.,Department of Dermatology, University of Michigan Medical School, Ann Arbor, MI 48109.,Rogel Cancer Center, University of Michigan, Ann Arbor, MI 48109
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11
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Devine MJ, Kittler JT. Mitochondria at the neuronal presynapse in health and disease. Nat Rev Neurosci 2019; 19:63-80. [PMID: 29348666 DOI: 10.1038/nrn.2017.170] [Citation(s) in RCA: 346] [Impact Index Per Article: 69.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Synapses enable neurons to communicate with each other and are therefore a prerequisite for normal brain function. Presynaptically, this communication requires energy and generates large fluctuations in calcium concentrations. Mitochondria are optimized for supplying energy and buffering calcium, and they are actively recruited to presynapses. However, not all presynapses contain mitochondria; thus, how might synapses with and without mitochondria differ? Mitochondria are also increasingly recognized to serve additional functions at the presynapse. Here, we discuss the importance of presynaptic mitochondria in maintaining neuronal homeostasis and how dysfunctional presynaptic mitochondria might contribute to the development of disease.
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Affiliation(s)
- Michael J Devine
- Department of Neuroscience, Physiology and Pharmacology, University College London, London WC1E 6BT, UK
| | - Josef T Kittler
- Department of Neuroscience, Physiology and Pharmacology, University College London, London WC1E 6BT, UK
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12
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Fettiplace R, Nam JH. Tonotopy in calcium homeostasis and vulnerability of cochlear hair cells. Hear Res 2018; 376:11-21. [PMID: 30473131 DOI: 10.1016/j.heares.2018.11.002] [Citation(s) in RCA: 62] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/23/2018] [Revised: 11/05/2018] [Accepted: 11/08/2018] [Indexed: 12/18/2022]
Abstract
Ototoxicity, noise overstimulation, or aging, can all produce hearing loss with similar properties, in which outer hair cells (OHCs), principally those at the high-frequency base of the cochlea, are preferentially affected. We suggest that the differential vulnerability may partly arise from differences in Ca2+ balance among cochlear locations. Homeostasis is determined by three factors: Ca2+ influx mainly via mechanotransducer (MET) channels; buffering by calcium-binding proteins and organelles like mitochondria; and extrusion by the plasma membrane CaATPase pump. We review quantification of these parameters and use our experimentally-determined values to model changes in cytoplasmic and mitochondrial Ca2+ during Ca2+ influx through the MET channels. We suggest that, in OHCs, there are two distinct micro-compartments for Ca2+ handling, one in the hair bundle and the other in the cell soma. One conclusion of the modeling is that there is a tonotopic gradient in the ability of OHCs to handle the Ca2+ load, which correlates with their vulnerability to environmental challenges. High-frequency basal OHCs are the most susceptible because they have much larger MET currents and have smaller dimensions than low-frequency apical OHCs.
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Affiliation(s)
- Robert Fettiplace
- Department of Neuroscience, University of Wisconsin, Madison, WI, 53706, USA.
| | - Jong-Hoon Nam
- Departments of Mechanical Engineering and Biomedical Engineering, University of Rochester, Rochester, NY, 14627, USA
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13
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Xing X, Wu CF. Inter-relationships among physical dimensions, distal-proximal rank orders, and basal GCaMP fluorescence levels in Ca 2+ imaging of functionally distinct synaptic boutons at Drosophila neuromuscular junctions. J Neurogenet 2018; 32:195-208. [PMID: 30322321 DOI: 10.1080/01677063.2018.1504043] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
GCaMP imaging is widely employed for investigating neuronal Ca2+ dynamics. The Drosophila larval neuromuscular junction (NMJ) consists of three distinct types of motor terminals (type Ib, Is and II). We investigated whether variability in synaptic bouton sizes and GCaMP expression levels confound interpretations of GCaMP readouts, in inferring the intrinsic Ca2+ handling properties among these functionally distinct synapses. Analysis of large data sets accumulated over years established the wide ranges of bouton sizes and GCaMP baseline fluorescence, with large overlaps among synaptic categories. We showed that bouton size and GCaMP baseline fluorescence were not confounding factors in determining the characteristic frequency responses among type Ib, Is and II synapses. More importantly, the drastic phenotypes that hyperexcitability mutations manifest preferentially in particular synaptic categories, were not obscured by bouton heterogeneity in physical size and GCaMP expression level. Our data enabled an extensive analysis of the distal-proximal gradient of GCaMP responses upon genetic and pharmacological manipulations. The results illustrate the conditions that disrupt or enhance the distal-proximal gradients. For example, stimulus frequencies just above the threshold level produced the steepest gradient in low Ca2+ (0.1 mM) saline, while supra-threshold stimulation flattened the gradient. Moreover, membrane hyperexcitability mutations (eag1 Sh120 and parabss1) and mitochondrial inhibition by dinitrophenol (DNP) disrupted the gradient. However, a novel distal-proximal gradient of decay kinetics appeared after long-term DNP incubation. We performed focal recording to assess the failure rates in transmission at low Ca2+ levels, which yielded indications of a mild distal-proximal gradient in release probability.
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Affiliation(s)
- Xiaomin Xing
- a Department of Biology , University of Iowa , Iowa City , IA , USA
| | - Chun-Fang Wu
- a Department of Biology , University of Iowa , Iowa City , IA , USA
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14
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Wang P, Fernandez-Sanz C, Wang W, Sheu SS. Why don't mice lacking the mitochondrial Ca 2+ uniporter experience an energy crisis? J Physiol 2018; 598:1307-1326. [PMID: 30218574 DOI: 10.1113/jp276636] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2018] [Accepted: 08/28/2018] [Indexed: 01/15/2023] Open
Abstract
Current dogma holds that the heart balances energy demand and supply effectively and sustainably by sequestering enough Ca2+ into mitochondria during heartbeats to stimulate metabolic enzymes in the tricarboxylic acid (TCA) cycle and electron transport chain (ETC). This process is called excitation-contraction-bioenergetics (ECB) coupling. Recent breakthroughs in identifying the mitochondrial Ca2+ uniporter (MCU) and its associated proteins have opened up new windows for interrogating the molecular mechanisms of mitochondrial Ca2+ homeostasis regulation and its role in ECB coupling. Despite remarkable progress made in the past 7 years, it has been surprising, almost disappointing, that germline MCU deficiency in mice with certain genetic background yields viable pups, and knockout of the MCU in adult heart does not cause lethality. Moreover, MCU deficiency results in few adverse phenotypes, normal performance, and preserved bioenergetics in the heart at baseline. In this review, we briefly assess the existing literature on mitochondrial Ca2+ homeostasis regulation and then we consider possible explanations for why MCU-deficient mice are spared from energy crises under physiological conditions. We propose that MCU and/or mitochondrial Ca2+ may have limited ability to set ECB coupling, that other mitochondrial Ca2+ handling mechanisms may play a role, and that extra-mitochondrial Ca2+ may regulate ECB coupling. Since the heart needs to regenerate a significant amount of ATP to assure the perpetuation of heartbeats, multiple mechanisms are likely to work in concert to match energy supply with demand.
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Affiliation(s)
- Pei Wang
- Mitochondria and Metabolism Center, Department of Anesthesiology and Pain Medicine, University of Washington, Seattle, WA, 98109, USA
| | - Celia Fernandez-Sanz
- Center for Translational Medicine, Department of Medicine, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA, 19107, USA
| | - Wang Wang
- Mitochondria and Metabolism Center, Department of Anesthesiology and Pain Medicine, University of Washington, Seattle, WA, 98109, USA
| | - Shey-Shing Sheu
- Center for Translational Medicine, Department of Medicine, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA, 19107, USA
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Unraveling Synaptic GCaMP Signals: Differential Excitability and Clearance Mechanisms Underlying Distinct Ca 2+ Dynamics in Tonic and Phasic Excitatory, and Aminergic Modulatory Motor Terminals in Drosophila. eNeuro 2018; 5:eN-NWR-0362-17. [PMID: 29464198 PMCID: PMC5818553 DOI: 10.1523/eneuro.0362-17.2018] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2017] [Revised: 01/27/2018] [Accepted: 02/02/2018] [Indexed: 11/21/2022] Open
Abstract
GCaMP is an optogenetic Ca2+ sensor widely used for monitoring neuronal activities but the precise physiological implications of GCaMP signals remain to be further delineated among functionally distinct synapses. The Drosophila neuromuscular junction (NMJ), a powerful genetic system for studying synaptic function and plasticity, consists of tonic and phasic glutamatergic and modulatory aminergic motor terminals of distinct properties. We report a first simultaneous imaging and electric recording study to directly contrast the frequency characteristics of GCaMP signals of the three synapses for physiological implications. Different GCaMP variants were applied in genetic and pharmacological perturbation experiments to examine the Ca2+ influx and clearance processes underlying the GCaMP signal. Distinct mutational and drug effects on GCaMP signals indicate differential roles of Na+ and K+ channels, encoded by genes including paralytic (para), Shaker (Sh), Shab, and ether-a-go-go (eag), in excitability control of different motor terminals. Moreover, the Ca2+ handling properties reflected by the characteristic frequency dependence of the synaptic GCaMP signals were determined to a large extent by differential capacity of mitochondria-powered Ca2+ clearance mechanisms. Simultaneous focal recordings of synaptic activities further revealed that GCaMPs were ineffective in tracking the rapid dynamics of Ca2+ influx that triggers transmitter release, especially during low-frequency activities, but more adequately reflected cytosolic residual Ca2+ accumulation, a major factor governing activity-dependent synaptic plasticity. These results highlight the vast range of GCaMP response patterns in functionally distinct synaptic types and provide relevant information for establishing basic guidelines for the physiological interpretations of presynaptic GCaMP signals from in situ imaging studies.
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Greenberg JM, Lumbreras V, Pelaez D, Rajguru SM, Cheung HS. Neural Crest Stem Cells Can Differentiate to a Cardiomyogenic Lineage with an Ability to Contract in Response to Pulsed Infrared Stimulation. Tissue Eng Part C Methods 2017; 22:982-990. [PMID: 28192031 DOI: 10.1089/ten.tec.2016.0232] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
INTRODUCTION Cellular cardiomyoplasty has rapidly risen to prominence in the clinic following a myocardial infarction; however, low engraftment of transplanted cells limits the therapeutic benefit to these procedures. Recently, lineage-specific stem cells differentiated into cardiomyocytes have gained much attention to assist in the repair of an injured heart tissue; however, questions regarding the ideal cell source remain. In the present study, we have identified a source that is easy to extract stem cells from and show that the cells present have a high plasticity toward the cardiomyogenic lineage. We focused on the recently discovered neural crest stem cells residing in the periodontal ligament that can be easily obtained through dental procedures. MATERIALS AND METHODS Neural crest stem cells were obtained from human excised third molars and differentiated in culture using a protocol for directed differentiation into cardiomyocytes. Differentiation of cells was assessed through gene expression and immunostaining studies. Optical stimulation using pulsed infrared radiation (IR) (λ = 1863 nm) was delivered to cell aggregates to study their contractile ability. RESULTS We show that neural crest stem cells can be differentiated to a cardiomyogenic lineage, which was verified through immunostaining and gene expression. We observed a significant increase in cardiomyocyte-specific markers, NK2 homeobox 5 (NKX2.5) and troponin T type 2 (TNNT2), with positive changes in tropomyosin I (TPM1), gap junction protein alpha 1/Cx43 (GJA1/Cx43), and myocyte enhancement factor 2C (MEF2C). Furthermore, we were able to elicit and maintain pulse-by-pulse contractile responses in the derived cells, including in cardiospheres, with pulsed IR delivered at various radiant energies. The contractility in responses to IR could be maintained at different frequencies (0.25-2 Hz) and up to 10-min durations. While these cells did not maintain their contractility following cessation of IR, these cells demonstrated responses to the optical stimuli that are consistent with previous reports. We also found no evidence for irreversible mitochondrial depolarization in these cells following the long duration of infrared stimulation, suggesting the robustness of these cells. CONCLUSIONS Overall, these results suggest the merit of neural crest-derived stem cells for cardiomyogenic applications and a potential cell source for repair that should contribute to efforts to translate cell-based strategies to the clinic.
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Affiliation(s)
- Jordan M Greenberg
- 1 Department of Biomedical Engineering, College of Engineering, University of Miami , Coral Gables, Florida
| | - Vicente Lumbreras
- 1 Department of Biomedical Engineering, College of Engineering, University of Miami , Coral Gables, Florida
| | - Daniel Pelaez
- 2 Geriatric Research, Education and Clinical Center (GRECC), Miami Veterans Affairs Medical Center , Miami, Florida
| | - Suhrud M Rajguru
- 1 Department of Biomedical Engineering, College of Engineering, University of Miami , Coral Gables, Florida.,3 Department of Otolaryngology, Miller School of Medicine, University of Miami , Miami, Florida
| | - Herman S Cheung
- 1 Department of Biomedical Engineering, College of Engineering, University of Miami , Coral Gables, Florida.,2 Geriatric Research, Education and Clinical Center (GRECC), Miami Veterans Affairs Medical Center , Miami, Florida
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Yamamura H, Kawasaki K, Inagaki S, Suzuki Y, Imaizumi Y. Local Ca 2+ coupling between mitochondria and sarcoplasmic reticulum following depolarization in guinea pig urinary bladder smooth muscle cells. Am J Physiol Cell Physiol 2017; 314:C88-C98. [PMID: 29046294 DOI: 10.1152/ajpcell.00208.2017] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Spatiotemporal changes in cytosolic Ca2+ concentration ([Ca2+]c) trigger a number of physiological functions in smooth muscle cells (SMCs). We previously imaged Ca2+-induced Ca2+ release following membrane depolarization as local Ca2+ transients, Ca2+ hotspots, in subplasmalemmal regions. In this study, the physiological significance of mitochondria on local Ca2+ signaling was examined. Cytosolic and mitochondrial Ca2+ images following depolarization or action potentials were recorded in single SMCs from the guinea pig urinary bladder using a fast-scanning confocal fluorescent microscope. Depolarization- and action potential-induced [Ca2+]c transients occurred at several discrete sites in subplasmalemmal regions, peaked within 30 ms, and then spread throughout the whole-cell. In contrast, Ca2+ concentration in the mitochondria matrix ([Ca2+]m) increased after a delay of ~50 ms from the start of depolarization, and then peaked within 500 ms. Following repolarization, [Ca2+]c returned to the resting level with a half-decay time of ~500 ms, while [Ca2+]m recovered more slowly (∼1.5 s). Carbonyl cyanide 4-(trifluoromethoxy)phenylhydrazone, a mitochondrial uncoupler, abolished depolarization-induced [Ca2+]m elevations and slowed [Ca2+]c changes. Importantly, short depolarization-induced changes in [Ca2+]m and transmembrane potential in mitochondria coupled to Ca2+ hotspots were significantly larger than those in other mitochondria. Total internal reflection fluorescence imaging revealed that a subset of mitochondria closely localized with ryanodine receptors and voltage-dependent Ca2+ channels. These results indicate that particular mitochondria are functionally coupled to ion channels and sarcoplasmic reticulum fragments within the local Ca2+ microdomain, and thus, strongly contribute to [Ca2+]c regulation in SMCs.
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Affiliation(s)
- Hisao Yamamura
- Department of Molecular and Cellular Pharmacology, Graduate School of Pharmaceutical Sciences, Nagoya City University , Nagoya , Japan
| | - Keisuke Kawasaki
- Department of Molecular and Cellular Pharmacology, Graduate School of Pharmaceutical Sciences, Nagoya City University , Nagoya , Japan
| | - Sou Inagaki
- Department of Molecular and Cellular Pharmacology, Graduate School of Pharmaceutical Sciences, Nagoya City University , Nagoya , Japan
| | - Yoshiaki Suzuki
- Department of Molecular and Cellular Pharmacology, Graduate School of Pharmaceutical Sciences, Nagoya City University , Nagoya , Japan
| | - Yuji Imaizumi
- Department of Molecular and Cellular Pharmacology, Graduate School of Pharmaceutical Sciences, Nagoya City University , Nagoya , Japan
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18
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Intermediate Filaments as Organizers of Cellular Space: How They Affect Mitochondrial Structure and Function. Cells 2016; 5:cells5030030. [PMID: 27399781 PMCID: PMC5040972 DOI: 10.3390/cells5030030] [Citation(s) in RCA: 49] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2016] [Revised: 06/24/2016] [Accepted: 06/30/2016] [Indexed: 12/17/2022] Open
Abstract
Intermediate filaments together with actin filaments and microtubules form the cytoskeleton, which is a complex and highly dynamic 3D network. Intermediate filaments are the major mechanical stress protectors but also affect cell growth, differentiation, signal transduction, and migration. Using intermediate filament-mitochondrial crosstalk as a prominent example, this review emphasizes the importance of intermediate filaments as crucial organizers of cytoplasmic space to support these functions. We summarize observations in different mammalian cell types which demonstrate how intermediate filaments influence mitochondrial morphology, subcellular localization, and function through direct and indirect interactions and how perturbations of these interactions may lead to human diseases.
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19
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Slater CR. The functional organization of motor nerve terminals. Prog Neurobiol 2015; 134:55-103. [DOI: 10.1016/j.pneurobio.2015.09.004] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2015] [Revised: 08/28/2015] [Accepted: 09/05/2015] [Indexed: 12/19/2022]
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20
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Lumbreras V, Bas E, Gupta C, Rajguru SM. Pulsed infrared radiation excites cultured neonatal spiral and vestibular ganglion neurons by modulating mitochondrial calcium cycling. J Neurophysiol 2014; 112:1246-55. [PMID: 24920028 DOI: 10.1152/jn.00253.2014] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Cochlear implants are currently the most effective solution for profound sensorineural hearing loss, and vestibular prostheses are under development to treat bilateral vestibulopathies. Electrical current spread in these neuroprostheses limits channel independence and, in some cases, may impair their performance. In comparison, optical stimuli that are spatially confined may result in a significant functional improvement. Pulsed infrared radiation (IR) has previously been shown to elicit responses in neurons. This study analyzes the response of neonatal rat spiral and vestibular ganglion neurons in vitro to IR (wavelength = 1,863 nm) using Ca(2+) imaging. Both types of neurons responded consistently with robust intracellular Ca(2+) ([Ca(2+)]i) transients that matched the low-frequency IR pulses applied (4 ms, 0.25-1 pps). Radiant exposures of ∼637 mJ/cm(2) resulted in continual neuronal activation. Temperature or [Ca(2+)] variations in the media did not alter the IR-evoked transients, ruling out extracellular Ca(2+) involvement or primary mediation by thermal effects on the plasma membrane. While blockage of Na(+), K(+), and Ca(2+) plasma membrane channels did not alter the IR-evoked response, blocking of mitochondrial Ca(2+) cycling with CGP-37157 or ruthenium red reversibly inhibited the IR-evoked [Ca(2+)]i transients. Additionally, the magnitude of the IR-evoked transients was dependent on ryanodine and cyclopiazonic acid-dependent Ca(2+) release. These results suggest that IR modulation of intracellular calcium cycling contributes to stimulation of spiral and vestibular ganglion neurons. As a whole, the results suggest selective excitation of neurons in the IR beam path and the potential of IR stimulation in future auditory and vestibular prostheses.
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Affiliation(s)
- Vicente Lumbreras
- Department of Biomedical Engineering, University of Miami, Miami, Florida; and
| | - Esperanza Bas
- Department of Otolaryngology, University of Miami, Miami, Florida
| | - Chhavi Gupta
- Department of Otolaryngology, University of Miami, Miami, Florida
| | - Suhrud M Rajguru
- Department of Biomedical Engineering, University of Miami, Miami, Florida; and Department of Otolaryngology, University of Miami, Miami, Florida
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21
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22
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Redpath CJ, Bou Khalil M, Drozdzal G, Radisic M, McBride HM. Mitochondrial hyperfusion during oxidative stress is coupled to a dysregulation in calcium handling within a C2C12 cell model. PLoS One 2013; 8:e69165. [PMID: 23861961 PMCID: PMC3704522 DOI: 10.1371/journal.pone.0069165] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2012] [Accepted: 06/11/2013] [Indexed: 01/04/2023] Open
Abstract
Atrial Fibrillation is the most common sustained cardiac arrhythmia worldwide harming millions of people every year. Atrial Fibrillation (AF) abruptly induces rapid conduction between atrial myocytes which is associated with oxidative stress and abnormal calcium handling. Unfortunately this new equilibrium promotes perpetuation of the arrhythmia. Recently, in addition to being the major source of oxidative stress within cells, mitochondria have been observed to fuse, forming mitochondrial networks and attach to intracellular calcium stores in response to cellular stress. We sought to identify a potential role for rapid stimulation, oxidative stress and mitochondrial hyperfusion in acute changes to myocyte calcium handling. In addition we hoped to link altered calcium handling to increased sarcoplasmic reticulum (SR)-mitochondrial contacts, the so-called mitochondrial associated membrane (MAM). We selected the C2C12 murine myotube model as it has previously been successfully used to investigate mitochondrial dynamics and has a myofibrillar system similar to atrial myocytes. We observed that rapid stimulation of C2C12 cells resulted in mitochondrial hyperfusion and increased mitochondrial colocalisation with calcium stores. Inhibition of mitochondrial fission by transfection of mutant DRP1K38E resulted in similar effects on mitochondrial fusion, SR colocalisation and altered calcium handling. Interestingly the effects of 'forced fusion' were reversed by co-incubation with the reducing agent N-Acetyl cysteine (NAC). Subsequently we demonstrated that oxidative stress resulted in similar reversible increases in mitochondrial fusion, SR-colocalisation and altered calcium handling. Finally, we believe we have identified that myocyte calcium handling is reliant on baseline levels of reactive oxygen species as co-incubation with NAC both reversed and retarded myocyte response to caffeine induced calcium release and re-uptake. Based on these results we conclude that the coordinate regulation of mitochondrial fusion and MAM contacts may form a point source for stress-induced arrhythmogenesis. We believe that the MAM merits further investigation as a therapeutic target in AF-induced remodelling.
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Affiliation(s)
- Calum J Redpath
- Cellular Electrophysiology Laboratory, University of Ottawa Heart Institute, University of Ottawa, Ottawa, ON, Canada.
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23
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Patron M, Raffaello A, Granatiero V, Tosatto A, Merli G, De Stefani D, Wright L, Pallafacchina G, Terrin A, Mammucari C, Rizzuto R. The mitochondrial calcium uniporter (MCU): molecular identity and physiological roles. J Biol Chem 2013; 288:10750-8. [PMID: 23400777 DOI: 10.1074/jbc.r112.420752] [Citation(s) in RCA: 117] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The direct measurement of mitochondrial [Ca(2+)] with highly specific probes demonstrated that major swings in organellar [Ca(2+)] parallel the changes occurring in the cytosol and regulate processes as diverse as aerobic metabolism and cell death by necrosis and apoptosis. Despite great biological relevance, insight was limited by the complete lack of molecular understanding. The situation has changed, and new perspectives have emerged following the very recent identification of the mitochondrial Ca(2+) uniporter, the channel allowing rapid Ca(2+) accumulation across the inner mitochondrial membrane.
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Affiliation(s)
- Maria Patron
- Department of Biomedical Sciences, University of Padua and the Institute of Neuroscience, Consiglio Nazionale delle Ricerche, 35131 Padua, Italy
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24
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Abstract
During the past two decades calcium (Ca(2+)) accumulation in energized mitochondria has emerged as a biological process of utmost physiological relevance. Mitochondrial Ca(2+) uptake was shown to control intracellular Ca(2+) signalling, cell metabolism, cell survival and other cell-type specific functions by buffering cytosolic Ca(2+) levels and regulating mitochondrial effectors. Recently, the identity of mitochondrial Ca(2+) transporters has been revealed, opening new perspectives for investigation and molecular intervention.
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25
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Mitochondria, calcium-dependent neuronal death and neurodegenerative disease. Pflugers Arch 2012; 464:111-21. [PMID: 22615071 PMCID: PMC3387496 DOI: 10.1007/s00424-012-1112-0] [Citation(s) in RCA: 138] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2012] [Revised: 04/29/2012] [Accepted: 05/02/2012] [Indexed: 11/18/2022]
Abstract
Understanding the mechanisms of neuronal dysfunction and death represents a major frontier in contemporary medicine, involving the acute cell death in stroke, and the attrition of the major neurodegenerative diseases, including Parkinson's, Alzheimer's, Huntington's and Motoneuron diseases. A growing body of evidence implicates mitochondrial dysfunction as a key step in the pathogenesis of all these diseases, with the promise that mitochondrial processes represent valuable potential therapeutic targets. Each disease is characterised by the loss of a specific vulnerable population of cells—dopaminergic neurons in Parkinson's disease, spinal motoneurons in Motoneuron disease, for example. We discuss the possible roles of cell type-specific calcium signalling mechanisms in defining the pathological phenotype of each of these major diseases and review central mechanisms of calcium-dependent mitochondrial-mediated cell death.
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26
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Rashed RM, El-Alfy SH. Ultrastructural organization of muscle fiber types and their distribution in the rat superior rectus extraocular muscle. Acta Histochem 2012; 114:217-25. [PMID: 21621253 DOI: 10.1016/j.acthis.2011.04.007] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2011] [Revised: 04/18/2011] [Accepted: 04/28/2011] [Indexed: 11/16/2022]
Abstract
Extraocular muscles (EOMs) are unique as they show greater variation in anatomical and physiological properties than any other skeletal muscles. To investigate the muscle fiber types and to understand better the structure-function correlation of the extraocular muscles, the present study examined the ultrastructural characteristics of the superior rectus muscle of rat. The superior rectus muscle is organized into two layers: a central global layer of mainly large-diameter fibers and an outer C-shaped orbital layer of principally small-diameter fibers. Six morphologically distinct fiber types were identified within the superior rectus muscle. Four muscle fiber types, three single innervated fibers (SIFs) and one multiple innervated fiber (MIF), were recognized in the global layer. The single innervated fibers included red, white and intermediate fibers. They differed from one another with respect to diameter, mitochondrial size and distribution, sarcoplasmic reticulum and myofibrillar size. The orbital layer contained two distinct MIFs in addition to the red and intermediate SIFs. The orbital MIFs were categorized into low oxidative and high oxidative types according to their mitochondrial content and distribution. The highly specialized function of the superior rectus extraocular muscle is reflected in the multiplicity of its fiber types, which exhibit unique structural features. The unique ultrastructural features of the extraocular muscles and their possible relation to muscle function are discussed.
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27
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Mitochondria in motor nerve terminals: function in health and in mutant superoxide dismutase 1 mouse models of familial ALS. J Bioenerg Biomembr 2012; 43:581-6. [PMID: 22089637 DOI: 10.1007/s10863-011-9392-1] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/15/2022]
Abstract
Mitochondria contribute to neuronal function not only via their ability to generate ATP, but also via their ability to buffer large Ca(2+) loads. This review summarizes evidence that mitochondrial Ca(2+) sequestration is especially important for sustaining the function of vertebrate motor nerve terminals during repetitive stimulation. Motor terminal mitochondria can sequester large amounts of Ca(2+) because they have mechanisms for limiting both the mitochondrial depolarization and the increase in matrix free [Ca(2+)] associated with Ca(2+) influx. In mice expressing mutations of human superoxide dismutase -1 (SOD1) that cause some cases of familial amyotrophic lateral sclerosis (fALS), motor terminals degenerate well before the death of motor neuron cell bodies. This review presents evidence for early and progressive mitochondrial dysfunction in motor terminals of mutant SOD1 mice (G93A, G85R). This dysfunction would impair mitochondrial ability to sequester stimulation-associated Ca(2+) loads, and thus likely contributes to the early degeneration of motor terminals.
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28
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Repetitive nerve stimulation transiently opens the mitochondrial permeability transition pore in motor nerve terminals of symptomatic mutant SOD1 mice. Neurobiol Dis 2011; 42:381-90. [PMID: 21310237 DOI: 10.1016/j.nbd.2011.01.031] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2010] [Revised: 12/17/2010] [Accepted: 01/28/2011] [Indexed: 11/20/2022] Open
Abstract
Mitochondria in motor nerve terminals temporarily sequester large Ca(2+) loads during repetitive stimulation. In wild-type mice this Ca(2+) uptake produces a small (<5 mV), transient depolarization of the mitochondrial membrane potential (Ψ(m), motor nerve stimulated at 100 Hz for 5s). We demonstrate that this stimulation-induced Ψ(m) depolarization attains much higher amplitudes in motor terminals of symptomatic mice expressing the G93A or G85R mutation of human superoxide dismutase 1 (SOD1), models of familial amyotrophic lateral sclerosis (fALS). These large Ψ(m) depolarizations decayed slowly and incremented with successive stimulus trains. Additional Ψ(m) depolarizations occurred that were not synchronized with stimulation. These large Ψ(m) depolarizations were reduced (a) by cyclosporin A (CsA, 1-2 μM), which inhibits opening of the mitochondrial permeability transition pore (mPTP), or (b) by replacing bath Ca(2+) with Sr(2+), which enters motor terminals and mitochondria but does not support mPTP opening. These results are consistent with the hypothesis that the large Ψ(m) depolarizations evoked by repetitive stimulation in motor terminals of symptomatic fALS mice result from mitochondrial dysfunction that increases the likelihood of transient mPTP opening during Ca(2+) influx. Such mPTP openings, a sign of mitochondrial stress, would disrupt motor terminal handling of Ca(2+) loads and might thereby contribute to motor terminal degeneration in fALS mice. Ψ(m) depolarizations resembling those in symptomatic fALS mice could be elicited in wild-type mice following a 0.5-1h exposure to diamide (200 μM), which produces an oxidative stress, but these depolarizations were not reduced by CsA.
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29
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Bonda DJ, Smith MA, Perry G, Lee HG, Wang X, Zhu X. The mitochondrial dynamics of Alzheimer's disease and Parkinson's disease offer important opportunities for therapeutic intervention. Curr Pharm Des 2011; 17:3374-80. [PMID: 21902671 PMCID: PMC3749822 DOI: 10.2174/138161211798072562] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2011] [Accepted: 08/17/2011] [Indexed: 11/22/2022]
Abstract
Mitochondrial dynamics play a crucial role in the pathobiology underlying Alzheimer's disease (AD) and Parkinson's disease (PD). Although a complete scientific understanding of these devastating conditions has yet to be realized, alterations in mitochondrial fission and fusion, and in the protein complexes that orchestrate mitochondrial fission and fusion, have been well established in AD- and PD-related neurodegeneration. Whether fission/fusion disruption in the brain is a causal agent in neuronal demise or a product of some other upstream disturbance is still a matter of debate; however, in both AD and PD, the potential for successful therapeutic amelioration of degeneration via mitochondrial protection is high. We here discuss the role of mitochondrial dynamics in AD and PD and assess the need for their therapeutic exploitation.
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Affiliation(s)
- David J. Bonda
- Department of Pathology Case Western Reserve University, Cleveland, Ohio, USA
| | - Mark A. Smith
- Department of Pathology Case Western Reserve University, Cleveland, Ohio, USA
| | - George Perry
- College of Sciences, University of Texas at San Antonio, San Antonio, Texas, USA
| | - Hyoung-gon Lee
- Department of Pathology Case Western Reserve University, Cleveland, Ohio, USA
| | - Xinglong Wang
- Department of Pathology Case Western Reserve University, Cleveland, Ohio, USA
| | - Xiongwei Zhu
- Department of Pathology Case Western Reserve University, Cleveland, Ohio, USA
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30
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Westerblad H, Place N, Yamada T. Mechanisms of skeletal muscle weakness. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2010; 682:279-96. [PMID: 20824532 DOI: 10.1007/978-1-4419-6366-6_16] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/29/2023]
Abstract
Skeletal muscle weakness is an important feature of numerous -pathological conditions and it may also be a component in normal ageing. Decreased muscular strength can be due to decreased muscle mass and/or intrinsic defects in the muscle cells. In this chapter we will discuss decreased force production due to mechanisms intrinsic to skeletal muscle cells. We will mainly use data from mouse disease models to exemplify defects at various sites in the cellular activation-contraction pathway. We will show that depending on the underlying problem, muscle weakness can be due decreased Ca²(+) release from the sarcoplasmic reticulum, reduced myofibrillar Ca²(+) sensitivity and/or decreased ability of the cross-bridges to generate force.
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Affiliation(s)
- Håkan Westerblad
- Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden.
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Presynaptic mitochondria in functionally different motor neurons exhibit similar affinities for Ca2+ but exert little influence as Ca2+ buffers at nerve firing rates in situ. J Neurosci 2010; 30:1869-81. [PMID: 20130196 DOI: 10.1523/jneurosci.4701-09.2010] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Mitochondria accumulate within nerve terminals and support synaptic function, most notably through ATP production. They can also sequester Ca(2+) during nerve stimulation, but it is unknown whether this limits presynaptic Ca(2+) levels at physiological nerve firing rates. Similarly, it is unclear whether mitochondrial Ca(2+) sequestration differs between functionally different nerve terminals. We addressed these questions using a combination of synthetic and genetically encoded Ca(2+) indicators to examine cytosolic and mitochondrial Ca(2+) levels in presynaptic terminals of tonic (MN13-Ib) and phasic (MNSNb/d-Is) motor neurons in Drosophila, which, as we determined, fire during fictive locomotion at approximately 42 Hz and approximately 8 Hz, respectively. Mitochondrial Ca(2+) sequestration starts in both terminals at approximately 250 nM, exhibits a similar Ca(2+)-uptake affinity (approximately 410 nM), and does not require Ca(2+) release from the endoplasmic reticulum. Nonetheless, mitochondrial Ca(2+) uptake in type Is terminals is more responsive to low-frequency nerve stimulation and this is due to higher cytosolic Ca(2+) levels. Since type Ib terminals have a higher mitochondrial density than Is terminals, it seemed possible that greater mitochondrial Ca(2+) sequestration may be responsible for the lower cytosolic Ca(2+) levels in Ib terminals. However, genetic and pharmacological manipulations of mitochondrial Ca(2+) uptake did not significantly alter nerve-stimulated elevations in cytosolic Ca(2+) levels in either terminal type within physiologically relevant rates of stimulation. Our findings indicate that presynaptic mitochondria have a similar affinity for Ca(2+) in functionally different nerve terminals, but do not limit cytosolic Ca(2+) levels within the range of motor neuron firing rates in situ.
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32
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Gellerich FN, Gizatullina Z, Trumbeckaite S, Nguyen HP, Pallas T, Arandarcikaite O, Vielhaber S, Seppet E, Striggow F. The regulation of OXPHOS by extramitochondrial calcium. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2010; 1797:1018-27. [PMID: 20144582 DOI: 10.1016/j.bbabio.2010.02.005] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/11/2009] [Revised: 02/01/2010] [Accepted: 02/02/2010] [Indexed: 11/29/2022]
Abstract
Despite extensive research, the regulation of mitochondrial function is still not understood completely. Ample evidence shows that cytosolic Ca2+ has a strategic task in co-ordinating the cellular work load and the regeneration of ATP by mitochondria. Currently, the paradigmatic view is that Cacyt2+ taken up by the Ca2+ uniporter activates the matrix enzymes pyruvate dehydrogenase, alpha-ketoglutarate dehydrogenase and isocitrate dehydrogenase. However, we have recently found that Ca2+ regulates the glutamate-dependent state 3 respiration by the supply of glutamate to mitochondria via aralar, a mitochondrial glutamate/aspartate carrier. Since this activation is not affected by ruthenium red, glutamate transport into mitochondria is controlled exclusively by extramitochondrial Ca2+. Therefore, this discovery shows that besides intramitochondrial also extramitochondrial Ca2+ regulates oxidative phosphorylation. This new mechanism acts as a mitochondrial "gas pedal", supplying the OXPHOS with substrate on demand. These results are in line with recent findings of Satrustegui and Palmieri showing that aralar as part of the malate-aspartate shuttle is involved in the Ca2+-dependent transport of reducing hydrogen equivalents (from NADH) into mitochondria. This review summarises results and evidence as well as hypothetical interpretations of data supporting the view that at the surface of mitochondria different regulatory Ca2+-binding sites exist and can contribute to cellular energy homeostasis. Moreover, on the basis of our own data, we propose that these surface Ca2+-binding sites may act as targets for neurotoxic proteins such as mutated huntingtin and others. The binding of these proteins to Ca2+-binding sites can impair the regulation by Ca2+, causing energetic depression and neurodegeneration.
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Affiliation(s)
- Frank N Gellerich
- KeyNeurotek Pharmaceuticals AG, ZENIT Technology Park, Leipziger Str. 44, D-39120 Magdeburg, Germany.
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Fernyhough P, Roy Chowdhury SK, Schmidt RE. Mitochondrial stress and the pathogenesis of diabetic neuropathy. Expert Rev Endocrinol Metab 2010; 5:39-49. [PMID: 20729997 PMCID: PMC2924887 DOI: 10.1586/eem.09.55] [Citation(s) in RCA: 89] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Diabetic neuropathy is a major complication of diabetes that affects the sensory and autonomic nervous systems and leads to significant morbidity and impact on quality of life of patients. Mitochondrial stress has been proposed as a major mediator of neurodegeneration in diabetes. This review briefly summarizes the nature of sensory and autonomic nerve dysfunction and presents these findings in the context of diabetes-induced nerve degeneration mediated by alterations in mitochondrial ultrastructure, physiology and trafficking. Diabetes-induced dysfunction in calcium homeostasis is discussed at length and causative associations with sub-optimal mitochondrial physiology are developed. It is clear that across a range of complications of diabetes that mitochondrial physiology is impaired, in general a reduction in electron transport chain capability is apparent. This abnormal activity may predispose mitochondria to generate elevated reactive oxygen species (ROS), although experimental proof remains lacking, but more importantly will deleteriously alter the bioenergetic status of neurons. It is proposed that the next five years of research should focus on identifying changes in mitochondrial phenotype and associated cellular impact, identifying sources of ROS in neurons and analyzing mitochondrial trafficking under diabetic conditions.
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Affiliation(s)
- Paul Fernyhough
- Division of Neurodegenerative Disorders, St Boniface Hospital Research Centre, R4046 - 351 Taché Avenue, Winnipeg, MB R2H 2A6, Canada and Department of Pharmacology & Therapeutics, University of Manitoba, Winnipeg, MB, Canada, Tel: (204) 235 3692
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Fernyhough P, Calcutt NA. Abnormal calcium homeostasis in peripheral neuropathies. Cell Calcium 2009; 47:130-9. [PMID: 20034667 DOI: 10.1016/j.ceca.2009.11.008] [Citation(s) in RCA: 101] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2009] [Accepted: 11/17/2009] [Indexed: 01/02/2023]
Abstract
Abnormal neuronal calcium (Ca2+) homeostasis has been implicated in numerous diseases of the nervous system. The pathogenesis of two increasingly common disorders of the peripheral nervous system, namely neuropathic pain and diabetic polyneuropathy, has been associated with aberrant Ca2+ channel expression and function. Here we review the current state of knowledge regarding the role of Ca2+ dyshomeostasis and associated mitochondrial dysfunction in painful and diabetic neuropathies. The central impact of both alterations of Ca2+ signalling at the plasma membrane and also intracellular Ca2+ handling on sensory neurone function is discussed and related to abnormal endoplasmic reticulum performance. We also present new data highlighting sub-optimal axonal Ca2+ signalling in diabetic neuropathy and discuss the putative role for this abnormality in the induction of axonal degeneration in peripheral neuropathies. The accumulating evidence implicating Ca2+ dysregulation in both painful and degenerative neuropathies, along with recent advances in understanding of regional variations in Ca2+ channel and pump structures, makes modulation of neuronal Ca2+ handling an increasingly viable approach for therapeutic interventions against the painful and degenerative aspects of many peripheral neuropathies.
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Affiliation(s)
- Paul Fernyhough
- Department of Pharmacology and Therapeutics, University of Manitoba, Winnipeg, Manitoba, Canada R3E0T6.
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Pozzan T, Rudolf R. Measurements of mitochondrial calcium in vivo. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2009; 1787:1317-23. [DOI: 10.1016/j.bbabio.2008.11.012] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/12/2008] [Revised: 11/20/2008] [Accepted: 11/21/2008] [Indexed: 12/21/2022]
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Gunter TE, Sheu SS. Characteristics and possible functions of mitochondrial Ca(2+) transport mechanisms. BIOCHIMICA ET BIOPHYSICA ACTA 2009; 1787:1291-308. [PMID: 19161975 PMCID: PMC2730425 DOI: 10.1016/j.bbabio.2008.12.011] [Citation(s) in RCA: 154] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/16/2008] [Revised: 12/22/2008] [Accepted: 12/29/2008] [Indexed: 02/07/2023]
Abstract
Mitochondria produce around 92% of the ATP used in the typical animal cell by oxidative phosphorylation using energy from their electrochemical proton gradient. Intramitochondrial free Ca(2+) concentration ([Ca(2+)](m)) has been found to be an important component of control of the rate of this ATP production. In addition, [Ca(2+)](m) also controls the opening of a large pore in the inner mitochondrial membrane, the permeability transition pore (PTP), which plays a role in mitochondrial control of programmed cell death or apoptosis. Therefore, [Ca(2+)](m) can control whether the cell has sufficient ATP to fulfill its functions and survive or is condemned to death. Ca(2+) is also one of the most important second messengers within the cytosol, signaling changes in cellular response through Ca(2+) pulses or transients. Mitochondria can also sequester Ca(2+) from these transients so as to modify the shape of Ca(2+) signaling transients or control their location within the cell. All of this is controlled by the action of four or five mitochondrial Ca(2+) transport mechanisms and the PTP. The characteristics of these mechanisms of Ca(2+) transport and a discussion of how they might function are described in this paper.
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Affiliation(s)
- Thomas E Gunter
- Department of Biochemistry and Biophysics and Mitochondrial Research and Innovation Group, University of Rochester School of Medicine and Dentistry, 601 Elmwood Avenue, Rochester, NY 14642, USA.
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Ouabain evokes exocytosis dependent on ryanodine and mitochondrial calcium stores that is not followed by compensatory endocytosis at the neuromuscular junction. Neurochem Int 2009; 55:406-13. [DOI: 10.1016/j.neuint.2009.04.009] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2009] [Accepted: 04/20/2009] [Indexed: 11/19/2022]
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Mann ZF, Duchen MR, Gale JE. Mitochondria modulate the spatio-temporal properties of intra- and intercellular Ca2+ signals in cochlear supporting cells. Cell Calcium 2009; 46:136-46. [PMID: 19631380 DOI: 10.1016/j.ceca.2009.06.005] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2009] [Revised: 06/12/2009] [Accepted: 06/28/2009] [Indexed: 10/20/2022]
Abstract
In the cochlea, cell damage triggers intercellular Ca2+ waves that propagate through the glial-like supporting cells that surround receptor hair cells. These Ca2+ waves are thought to convey information about sensory hair cell-damage to the surrounding supporting cells within the cochlear epithelium. Mitochondria are key regulators of cytoplasmic Ca2+ concentration ([Ca2+](cyt)), and yet little is known about their role during the propagation of such intercellular Ca2+ signalling. Using neonatal rat cochlear explants and fluorescence imaging techniques, we explore how mitochondria modulate supporting cell [Ca2+](cyt) signals that are triggered by ATP or by hair cell damage. ATP application (0.1-50 microM) caused a dose dependent increase in [Ca2+](cyt) which was accompanied by an increase in mitochondrial calcium. Blocking mitochondrial Ca2+ uptake by dissipating the mitochondrial membrane potential using CCCP and oligomycin or using Ru360, an inhibitor of the mitochondrial Ca2+ uniporter, enhanced the peak amplitude and duration of ATP-induced [Ca2+](cyt) transients. In the presence of Ru360, the mean propagation velocity, amplitude and extent of spread of damage-induced intercellular Ca2+ waves was significantly increased. Thus, mitochondria function as spatial Ca2+ buffers during agonist-evoked [Ca2+](cyt) signalling in cochlear supporting cells and play a significant role in regulating the spatio-temporal properties of intercellular Ca2+ waves.
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Affiliation(s)
- Zoë F Mann
- UCL Ear Institute, 332 Gray's Inn Road, London WC1X 8EE, UK; Department of Cell and Developmental Biology, University College London, Gower Street, London WC1E 6BT, UK
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Jaiswal MK, Zech WD, Goos M, Leutbecher C, Ferri A, Zippelius A, Carrì MT, Nau R, Keller BU. Impairment of mitochondrial calcium handling in a mtSOD1 cell culture model of motoneuron disease. BMC Neurosci 2009; 10:64. [PMID: 19545440 PMCID: PMC2716351 DOI: 10.1186/1471-2202-10-64] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2009] [Accepted: 06/22/2009] [Indexed: 12/16/2022] Open
Abstract
Background Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disorder characterized by the selective loss of motor neurons (MN) in the brain stem and spinal cord. Intracellular disruptions of cytosolic and mitochondrial calcium have been associated with selective MN degeneration, but the underlying mechanisms are not well understood. The present evidence supports a hypothesis that mitochondria are a target of mutant SOD1-mediated toxicity in familial amyotrophic lateral sclerosis (fALS) and intracellular alterations of cytosolic and mitochondrial calcium might aggravate the course of this neurodegenerative disease. In this study, we used a fluorescence charged cool device (CCD) imaging system to separate and simultaneously monitor cytosolic and mitochondrial calcium concentrations in individual cells in an established cellular model of ALS. Results To gain insights into the molecular mechanisms of SOD1G93A associated motor neuron disease, we simultaneously monitored cytosolic and mitochondrial calcium concentrations in individual cells. Voltage – dependent cytosolic Ca2+ elevations and mitochondria – controlled calcium release mechanisms were monitored after loading cells with fluorescent dyes fura-2 and rhod-2. Interestingly, comparable voltage-dependent cytosolic Ca2+ elevations in WT (SH-SY5YWT) and G93A (SH-SY5YG93A) expressing cells were observed. In contrast, mitochondrial intracellular Ca2+ release responses evoked by bath application of the mitochondrial toxin FCCP were significantly smaller in G93A expressing cells, suggesting impaired calcium stores. Pharmacological experiments further supported the concept that the presence of G93A severely disrupts mitochondrial Ca2+ regulation. Conclusion In this study, by fluorescence measurement of cytosolic calcium and using simultaneous [Ca2+]i and [Ca2+]mito measurements, we are able to separate and simultaneously monitor cytosolic and mitochondrial calcium concentrations in individual cells an established cellular model of ALS. The primary goals of this paper are (1) method development, and (2) screening for deficits in mutant cells on the single cell level. On the technological level, our method promises to serve as a valuable tool to identify mitochondrial and Ca2+-related defects during G93A-mediated MN degeneration. In addition, our experiments support a model where a specialized interplay between cytosolic calcium profiles and mitochondrial mechanisms contribute to the selective degeneration of neurons in ALS.
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Nicholls DG. Mitochondrial calcium function and dysfunction in the central nervous system. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2009; 1787:1416-24. [PMID: 19298790 DOI: 10.1016/j.bbabio.2009.03.010] [Citation(s) in RCA: 169] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/26/2008] [Revised: 03/09/2009] [Accepted: 03/10/2009] [Indexed: 12/17/2022]
Abstract
The ability of isolated brain mitochondria to accumulate, store and release calcium has been extensively characterized. Extrapolation to the intact neuron led to predictions that the in situ mitochondria would reversibly accumulate Ca(2+) when the concentration of the cation in the vicinity of the mitochondria rose above the 'set-point' at which uptake and efflux were in balance, storing Ca(2+) as a complex with phosphate, and slowly releasing the cation when plasma membrane ion pumps lowered the cytoplasmic free Ca(2+). Excessive accumulation of the cation was predicted to lead to activation of the permeability transition, with catastrophic consequences for the neuron. Each of these predictions has been confirmed with intact neurons, and there is convincing evidence for the permeability transition in cellular Ca(2+) overload associated with glutamate excitotoxicity and stroke, while the neurodegenerative disease in which possible defects in mitochondrial Ca(2+) handling have been most intensively investigated is Huntington's Disease. In this brief review evidence that mitochondrial Ca(2+) transport is relevant to neuronal survival in these conditions will be discussed.
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Affiliation(s)
- David G Nicholls
- Buck Institute for Age Research, 8001 Redwood Boulevard, Novato, CA 94945, USA.
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Celsi F, Pizzo P, Brini M, Leo S, Fotino C, Pinton P, Rizzuto R. Mitochondria, calcium and cell death: a deadly triad in neurodegeneration. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2009; 1787:335-44. [PMID: 19268425 DOI: 10.1016/j.bbabio.2009.02.021] [Citation(s) in RCA: 219] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/17/2008] [Revised: 02/23/2009] [Accepted: 02/24/2009] [Indexed: 12/17/2022]
Abstract
Mitochondrial Ca(2+) accumulation is a tightly controlled process, in turn regulating functions as diverse as aerobic metabolism and induction of cell death. The link between Ca(2+) (dys)regulation, mitochondria and cellular derangement is particularly evident in neurodegenerative disorders, in which genetic models and environmental factors allowed to identify common traits in the pathogenic routes. We will here summarize: i) the current view of mechanisms and functions of mitochondrial Ca(2+) homeostasis, ii) the basic principles of organelle Ca(2+) transport, iii) the role of Ca(2+) in neuronal cell death, and iv) the new information on the pathogenesis of Alzheimer's, Huntington's and Parkinson's diseases, highlighting the role of Ca(2+) and mitochondria.
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Affiliation(s)
- Fulvio Celsi
- Department of Experimental and Diagnostic Medicine, Interdisciplinary Center for the Study of Inflammation, Italy
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The Psi(m) depolarization that accompanies mitochondrial Ca2+ uptake is greater in mutant SOD1 than in wild-type mouse motor terminals. Proc Natl Acad Sci U S A 2009; 106:2007-11. [PMID: 19174508 DOI: 10.1073/pnas.0810934106] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The electrical gradient across the mitochondrial inner membrane (Psi(m)) is established by electron transport chain (ETC) activity and permits mitochondrial Ca(2+) sequestration. Using rhodamine-123, we determined how repetitive nerve stimulation (100 Hz) affects Psi(m) in motor terminals innervating mouse levator auris muscles. Stimulation-induced Psi(m) depolarizations in wild-type (WT) terminals were small (<5 mV at 30 degrees C) and reversible. These depolarizations depended on Ca(2+) influx into motor terminals, as they were inhibited when P/Q-type Ca(2+) channels were blocked with omega-agatoxin. Stimulation-induced Psi(m) depolarization and elevation of cytosolic [Ca(2+)] both increased when complex I of the ETC was partially inhibited by low concentrations of rotenone (25-50 nmol/l). This finding is consistent with the hypothesis that acceleration of ETC proton extrusion normally limits the magnitude of Psi(m) depolarization during mitochondrial Ca(2+) uptake, thereby permitting continued Ca(2+) uptake. Compared with WT, stimulation-induced increases in rhodamine-123 fluorescence were approximately 5 times larger in motor terminals from presymptomatic mice expressing mutations of human superoxide dismutase I (SOD1) that cause familial amyotrophic lateral sclerosis (SOD1-G85R, which lacks dismutase activity; SOD1-G93A, which retains dismutase activity). Psi(m) depolarizations were not significantly altered by expression of WT human SOD1 or knockout of SOD1 or by inhibiting opening of the mitochondrial permeability transition pore with cyclosporin A. We suggest that an early functional consequence of the association of SOD1-G85R or SOD1-G93A with motoneuronal mitochondria is reduced capacity of the ETC to limit Ca(2+)-induced Psi(m) depolarization, and that this impairment contributes to disease progression in mutant SOD1 motor terminals.
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Demaurex N, Poburko D, Frieden M. Regulation of plasma membrane calcium fluxes by mitochondria. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2009; 1787:1383-94. [PMID: 19161976 DOI: 10.1016/j.bbabio.2008.12.012] [Citation(s) in RCA: 97] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/17/2008] [Revised: 12/21/2008] [Accepted: 12/29/2008] [Indexed: 11/27/2022]
Abstract
The role of mitochondria in cell signaling is becoming increasingly apparent, to an extent that the signaling role of mitochondria appears to have stolen the spotlight from their primary function as energy producers. In this chapter, we will review the ionic basis of calcium handling by mitochondria and discuss the mechanisms that these organelles use to regulate the activity of plasma membrane calcium channels and transporters.
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Affiliation(s)
- Nicolas Demaurex
- Department of Cell Physiology and Metabolism, University of Geneva, 1, rue Michel-Servet, CH-1211 Geneva 4, Switzerland
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Ardón F, Rodríguez-Miranda E, Beltrán C, Hernández-Cruz A, Darszon A. Mitochondrial inhibitors activate influx of external Ca2+ in sea urchin sperm. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2009; 1787:15-24. [DOI: 10.1016/j.bbabio.2008.10.003] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/07/2008] [Revised: 09/16/2008] [Accepted: 10/09/2008] [Indexed: 01/01/2023]
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Jaiswal MK, Keller BU. Cu/Zn Superoxide Dismutase Typical for Familial Amyotrophic Lateral Sclerosis Increases the Vulnerability of Mitochondria and Perturbs Ca2+ Homeostasis in SOD1G93A Mice. Mol Pharmacol 2008; 75:478-89. [DOI: 10.1124/mol.108.050831] [Citation(s) in RCA: 85] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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Aydin J, Andersson DC, Hänninen SL, Wredenberg A, Tavi P, Park CB, Larsson NG, Bruton JD, Westerblad H. Increased mitochondrial Ca2+ and decreased sarcoplasmic reticulum Ca2+ in mitochondrial myopathy. Hum Mol Genet 2008; 18:278-88. [PMID: 18945718 DOI: 10.1093/hmg/ddn355] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Genetic mutations that affect mitochondrial function often cause skeletal muscle dysfunction. Here, we used mice with skeletal-muscle-specific disruption of the nuclear gene for mitochondrial transcription factor A (Tfam) to study whether changes in cellular Ca(2+) handling is part of the mechanism of muscle dysfunction in mitochondrial myopathy. Force measurements were combined with measurements of cytosolic Ca(2+), mitochondrial Ca(2+) and membrane potential and reactive oxygen species in intact, adult muscle fibres. The results show reduced sarcoplasmic reticulum (SR) Ca(2+) storage capacity in Tfam KO muscles due to a decreased expression of calsequestrin-1. This resulted in decreased SR Ca(2+) release during contraction and hence lower force production in Tfam KO than in control muscles. Additionally, there were no signs of oxidative stress in Tfam KO cells, whereas they displayed increased mitochondrial [Ca(2+)] during repeated contractions. Mitochondrial [Ca(2+)] remained elevated long after the end of stimulation in muscle cells from terminally ill Tfam KO mice, and the increase was smaller in the presence of the cyclophilin D-binding inhibitor cyclosporin A. The mitochondrial membrane potential in Tfam KO cells did not decrease during repeated contractions. In conclusion, we suggest that the observed changes in Ca(2+) handling are adaptive responses with long-term detrimental effects. Reduced SR Ca(2+) release likely decreases ATP expenditure, but it also induces muscle weakness. Increased [Ca(2+)](mit) will stimulate mitochondrial metabolism acutely but may also trigger cell damage.
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Affiliation(s)
- Jan Aydin
- Present address: Max Planck Institute for Biology of Ageing, Gleueler Str. 50a, Cologne, Germany
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Mechanisms of prolonged presynaptic Ca2+ signaling and glutamate release induced by TRPV1 activation in rat sensory neurons. J Neurosci 2008; 28:5295-311. [PMID: 18480286 DOI: 10.1523/jneurosci.4810-07.2008] [Citation(s) in RCA: 108] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Transient receptor potential vanilloid receptor 1 (TRPV1)-mediated release of neuroactive peptides and neurotransmitters from the peripheral and central terminals of primary sensory neurons can critically contribute to nociceptive processing at the periphery and in the CNS. However, the mechanisms that link TRPV1 activation with Ca2+ signaling at the release sites and neurosecretion are poorly understood. Here we demonstrate that a brief stimulation of the receptor using either capsaicin or the endogenous TRPV1 agonist N-arachidonoyl-dopamine induces a prolonged elevation of presynaptic [Ca2+](i) and a concomitant enhancement of glutamate release at sensory synapses. Initiation of this response required Ca2+ entry, primarily via TRPV1. The sustained phase of the response was independent of extracellular Ca2+ and was prevented by inhibitors of mitochondrial Ca2+ uptake and release mechanisms. Measurements using a mitochondria-targeted Ca2+ indicator, mtPericam, revealed that TRPV1 activation elicits a long-lasting Ca2+ elevation in presynaptic mitochondria. The concentration of TRPV1 agonist determined the duration of mitochondrial and cytosolic Ca2+ signals in presynaptic boutons and, consequently, the period of enhanced glutamate release and action potential firing by postsynaptic neurons. These data suggest that mitochondria control vanilloid-induced neurotransmission by translating the strength of presynaptic TRPV1 stimulation into duration of the postsynaptic response.
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Kostareva A, Sjöberg G, Bruton J, Zhang SJ, Balogh J, Gudkova A, Hedberg B, Edström L, Westerblad H, Sejersen T. Mice expressing L345P mutant desmin exhibit morphological and functional changes of skeletal and cardiac mitochondria. J Muscle Res Cell Motil 2008; 29:25-36. [PMID: 18563598 DOI: 10.1007/s10974-008-9139-8] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2007] [Accepted: 05/28/2008] [Indexed: 10/21/2022]
Abstract
Desmin mutations underlie inherited myopathies/cardiomyopathies with varying severity and involvement of the skeletal and cardiac muscles. We developed a transgenic mouse model expressing low level of the L345P desmin mutation (DESMUT mice) in order to uncover changes in skeletal and cardiac muscles caused by this mutation. The most striking ultrastructural changes in muscle from DESMUT mice were mitochondrial swelling and vacuolization. The mitochondrial Ca(2+) level was significantly increased in skeletal and cardiac myocytes from DESMUT mice compared to wild type cells during and after contractions. In isolated DESMUT soleus muscles, contractile function and recovery from fatigue were impaired. A SHIRPA screening test for neuromuscular performance demonstrated decreased motor function in DESMUT compared to WT mice. Echocardiographic changes in DESMUT mice included left ventricular wall hypertrophy and a decreased left ventricular chamber dimension. The results imply that low levels of L345P desmin acts, at least partially, by a dominant negative effect on mitochondria.
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Affiliation(s)
- Anna Kostareva
- Department of Woman and Child Health and Center for Molecular Medicine, Karolinska Institute, L8:02, Stockholm 17176, Sweden
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Abstract
Mitochondria couple cellular metabolic state with Ca(2+) transport processes. They therefore control not only their own intra-organelle [Ca(2+)], but they also influence the entire cellular network of cellular Ca(2+) signaling, including the endoplasmic reticulum, the plasma membrane, and the nucleus. Through the detailed study of mitochondrial roles in Ca(2+) signaling, a remarkable picture of inter-organelle communication has emerged. We here review the ways in which this system provides integrity and flexibility for the cell to cope with the countless demands throughout its life cycle and discuss briefly the mechanisms through which it can also drive cell death.
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Affiliation(s)
- György Szabadkai
- Department of Physiology, Mitochondrial Biology Group, University College London, London, United Kingdom.
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50
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Abstract
The kinetic properties for the uptake, storage and release of Ca2+ from isolated mitochondria accurately predict the behaviour of the organelles within the intact cell. While the steady-state cycling of Ca2+ across the inner membrane between independent uptake and efflux pathways seems at first sight to be symmetrical, the distinctive kinetics of the uniporter, which is highly dependent on external free Ca2+ concentration and the efflux pathway, whose activity is clamped over a wide range of total matrix Ca2+ by the solubility of the calcium phosphate complex provide a mechanism whereby mitochondria reversibly sequester transient elevations in cytoplasmic Ca2+. Under non-stimulated conditions, the same transport processes can regulate matrix Ca2+ concentrations and hence citric acid cycle activity.
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Affiliation(s)
- David G Nicholls
- Buck Institute for Age Research, Redwood Boulevard, Novato, CA 94945, USA.
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