51
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Pooya S, Liu X, Kumar VBS, Anderson J, Imai F, Zhang W, Ciraolo G, Ratner N, Setchell KDR, Yoshida Y, Yutaka Y, Jankowski MP, Dasgupta B. The tumour suppressor LKB1 regulates myelination through mitochondrial metabolism. Nat Commun 2014; 5:4993. [PMID: 25256100 DOI: 10.1038/ncomms5993] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2014] [Accepted: 08/14/2014] [Indexed: 01/04/2023] Open
Abstract
A prerequisite to myelination of peripheral axons by Schwann cells (SCs) is SC differentiation, and recent evidence indicates that reprogramming from a glycolytic to oxidative metabolism occurs during cellular differentiation. Whether this reprogramming is essential for SC differentiation, and the genes that regulate this critical metabolic transition are unknown. Here we show that the tumour suppressor Lkb1 is essential for this metabolic transition and myelination of peripheral axons. Hypomyelination in the Lkb1-mutant nerves and muscle atrophy lead to hindlimb dysfunction and peripheral neuropathy. Lkb1-null SCs failed to optimally activate mitochondrial oxidative metabolism during differentiation. This deficit was caused by Lkb1-regulated diminished production of the mitochondrial Krebs cycle substrate citrate, a precursor to cellular lipids. Consequently, myelin lipids were reduced in Lkb1-mutant mice. Restoring citrate partially rescued Lkb1-mutant SC defects. Thus, Lkb1-mediated metabolic shift during SC differentiation increases mitochondrial metabolism and lipogenesis, necessary for normal myelination.
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Affiliation(s)
- Shabnam Pooya
- Department of Oncology, Cincinnati Children's Hospital Medical Center, 3333 Burnet Avenue, Cincinnati, Ohio 45229, USA
| | - Xiaona Liu
- Department of Experimental Hematology and Cancer Biology, Cincinnati Children's Hospital Medical Center, 3333 Burnet Avenue, Cincinnati, Ohio 45229, USA
| | - V B Sameer Kumar
- Department of Oncology, Cincinnati Children's Hospital Medical Center, 3333 Burnet Avenue, Cincinnati, Ohio 45229, USA
| | - Jane Anderson
- Department of Oncology, Cincinnati Children's Hospital Medical Center, 3333 Burnet Avenue, Cincinnati, Ohio 45229, USA
| | - Fumiyasu Imai
- Department of Developmental Biology, Cincinnati Children's Hospital Medical Center, 3333 Burnet Avenue, Cincinnati, Ohio 45229, USA
| | - Wujuan Zhang
- Department of Pathology, Cincinnati Children's Hospital Medical Center, 3333 Burnet Avenue, Cincinnati, Ohio 45229, USA
| | - Georgianne Ciraolo
- Department of Pathology and Laboratory Medicine, Cincinnati Children's Hospital Medical Center, 3333 Burnet Avenue, Cincinnati, Ohio 45229, USA
| | - Nancy Ratner
- Department of Experimental Hematology and Cancer Biology, Cincinnati Children's Hospital Medical Center, 3333 Burnet Avenue, Cincinnati, Ohio 45229, USA
| | - Kenneth D R Setchell
- Department of Pathology, Cincinnati Children's Hospital Medical Center, 3333 Burnet Avenue, Cincinnati, Ohio 45229, USA
| | | | - Yoshida Yutaka
- Department of Developmental Biology, Cincinnati Children's Hospital Medical Center, 3333 Burnet Avenue, Cincinnati, Ohio 45229, USA
| | - Michael P Jankowski
- Department of Anesthesia, Cincinnati Children's Hospital Medical Center, 3333 Burnet Avenue, Cincinnati, Ohio 45229, USA
| | - Biplab Dasgupta
- Department of Oncology, Cincinnati Children's Hospital Medical Center, 3333 Burnet Avenue, Cincinnati, Ohio 45229, USA
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Abstract
Mitochondrial dysfunction is the underlying cause of many neurological disorders, including peripheral neuropathies. Mitochondria rely on a proton gradient to generate ATP and interfering with electron transport chain function can lead to the deleterious accumulation of reactive oxygen species (ROS). Notably, loss of mitochondrial potential precedes cellular demise in several programmed cell destruction pathways, including axons undergoing Wallerian degeneration. Here, we demonstrate that mitochondrial depolarization triggers axon degeneration and cell death in primary mouse sensory neurons. These degenerative events are not blocked by inhibitors of canonical programmed cell death pathways such as apoptosis, necroptosis, and parthanatos. Instead, the axodestructive factor Sarm1 is required for this axon degeneration and cell death. In the absence of Sarm1, the mitochondrial poison CCCP still induces depolarization of mitochondria, ATP depletion, calcium influx, and the accumulation of ROS, yet cell death and axon degeneration are blocked. The survival of these neurons despite the accumulation of ROS indicates that Sarm1 acts downstream of ROS generation. Indeed, loss of Sarm1 protects sensory neurons and their axons from prolonged exposure to ROS. Therefore, Sarm1 functions downstream of ROS to induce neuronal cell death and axon degeneration during oxidative stress. These findings highlight the central role for Sarm1 in a novel form of programmed cell destruction that we term sarmoptosis.
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Pope HM, Voigt MM. Peripheral glia have a pivotal role in the initial response to axon degeneration of peripheral sensory neurons in zebrafish. PLoS One 2014; 9:e103283. [PMID: 25058656 PMCID: PMC4109997 DOI: 10.1371/journal.pone.0103283] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2014] [Accepted: 06/30/2014] [Indexed: 02/07/2023] Open
Abstract
Axon degeneration is a feature of many peripheral neuropathies. Understanding the organismal response to this degeneration may aid in identifying new therapeutic targets for treatment. Using a transgenic zebrafish line expressing a bacterial nitroreductase (Ntr)/mCherry fusion protein in the peripheral sensory neurons of the V, VII, IX, and X cranial nerves, we were able to induce and visualize the pathology of axon degeneration in vivo. Exposure of 4 days post fertilization Ntr larvae to the prodrug metronidazole (Met), which Ntr metabolizes into cytotoxic metabolites, resulted in dose-dependent cell death and axon degeneration. This was limited to the Ntr-expressing sensory neurons, as neighboring glia and motor axons were unaffected. Cell death was rapid, becoming apparent 3-4 hours after Met treatment, and was followed by phagocytosis of soma and axon debris by cells within the nerves and ganglia beginning at 4-5 hours of exposure. Although neutrophils appear to be activated in response to the degenerating neurons, they did not accumulate at the sites of degeneration. In contrast, macrophages were found to be attracted to the sites of the degenerating axons, where they phagocytosed debris. We demonstrated that peripheral glia are critical for both the phagocytosis and inflammatory response to degenerating neurons: mutants that lack all peripheral glia (foxD3-/-; Ntr) exhibit a much reduced reaction to axonal degeneration, resulting in a dramatic decrease in the clearance of debris, and impaired macrophage recruitment. Overall, these results show that this zebrafish model of peripheral sensory axon degeneration exhibits many aspects common to peripheral neuropathies and that peripheral glia play an important role in the initial response to this process.
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Affiliation(s)
- Holly M. Pope
- Department of Pharmacological and Physiological Science, Saint Louis University School of Medicine, St. Louis, Missouri, United States of America
| | - Mark M. Voigt
- Department of Pharmacological and Physiological Science, Saint Louis University School of Medicine, St. Louis, Missouri, United States of America
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54
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Mitochondria modify exercise-induced development of stem cell-derived neurons in the adult brain. J Neurosci 2014; 34:6624-33. [PMID: 24806687 DOI: 10.1523/jneurosci.4972-13.2014] [Citation(s) in RCA: 92] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Neural stem cells in the adult mammalian hippocampus continuously generate new functional neurons, which modify the hippocampal network and significantly contribute to cognitive processes and mood regulation. Here, we show that the development of new neurons from stem cells in adult mice is paralleled by extensive changes to mitochondrial mass, distribution, and shape. Moreover, exercise-a strong modifier of adult hippocampal neurogenesis-accelerates neuronal maturation and induces a profound increase in mitochondrial content and the presence of mitochondria in dendritic segments. Genetic inhibition of the activity of the mitochondrial fission factor dynamin-related protein 1 (Drp1) inhibits neurogenesis under basal and exercise conditions. Conversely, enhanced Drp1 activity furthers exercise-induced acceleration of neuronal maturation. Collectively, these results indicate that adult hippocampal neurogenesis requires adaptation of the mitochondrial compartment and suggest that mitochondria are targets for enhancing neurogenesis-dependent hippocampal plasticity.
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55
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Abbott JA, Francklyn CS, Robey-Bond SM. Transfer RNA and human disease. Front Genet 2014; 5:158. [PMID: 24917879 PMCID: PMC4042891 DOI: 10.3389/fgene.2014.00158] [Citation(s) in RCA: 150] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2014] [Accepted: 05/14/2014] [Indexed: 12/25/2022] Open
Abstract
Pathological mutations in tRNA genes and tRNA processing enzymes are numerous and result in very complicated clinical phenotypes. Mitochondrial tRNA (mt-tRNA) genes are “hotspots” for pathological mutations and over 200 mt-tRNA mutations have been linked to various disease states. Often these mutations prevent tRNA aminoacylation. Disrupting this primary function affects protein synthesis and the expression, folding, and function of oxidative phosphorylation enzymes. Mitochondrial tRNA mutations manifest in a wide panoply of diseases related to cellular energetics, including COX deficiency (cytochrome C oxidase), mitochondrial myopathy, MERRF (Myoclonic Epilepsy with Ragged Red Fibers), and MELAS (mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes). Diseases caused by mt-tRNA mutations can also affect very specific tissue types, as in the case of neurosensory non-syndromic hearing loss and pigmentary retinopathy, diabetes mellitus, and hypertrophic cardiomyopathy. Importantly, mitochondrial heteroplasmy plays a role in disease severity and age of onset as well. Not surprisingly, mutations in enzymes that modify cytoplasmic and mitochondrial tRNAs are also linked to a diverse range of clinical phenotypes. In addition to compromised aminoacylation of the tRNAs, mutated modifying enzymes can also impact tRNA expression and abundance, tRNA modifications, tRNA folding, and even tRNA maturation (e.g., splicing). Some of these pathological mutations in tRNAs and processing enzymes are likely to affect non-canonical tRNA functions, and contribute to the diseases without significantly impacting on translation. This chapter will review recent literature on the relation of mitochondrial and cytoplasmic tRNA, and enzymes that process tRNAs, to human disease. We explore the mechanisms involved in the clinical presentation of these various diseases with an emphasis on neurological disease.
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Affiliation(s)
- Jamie A Abbott
- Department of Biochemistry, College of Medicine, University of Vermont Burlington, VT, USA
| | | | - Susan M Robey-Bond
- Department of Biochemistry, College of Medicine, University of Vermont Burlington, VT, USA
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Niemann A, Huber N, Wagner KM, Somandin C, Horn M, Lebrun-Julien F, Angst B, Pereira JA, Halfter H, Welzl H, Feltri ML, Wrabetz L, Young P, Wessig C, Toyka KV, Suter U. The Gdap1 knockout mouse mechanistically links redox control to Charcot-Marie-Tooth disease. ACTA ACUST UNITED AC 2014; 137:668-82. [PMID: 24480485 PMCID: PMC3927703 DOI: 10.1093/brain/awt371] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Mutations in the mitochondrial fission factor GDAP1 are associated with severe peripheral neuropathies, but why the CNS remains unaffected is unclear. Using a Gdap1−/− mouse, Niemann et al. demonstrate that a CNS-expressed Gdap1 paralogue changes its subcellular localisation under oxidative stress conditions to also act as a mitochondrial fission factor. The ganglioside-induced differentiation-associated protein 1 (GDAP1) is a mitochondrial fission factor and mutations in GDAP1 cause Charcot–Marie–Tooth disease. We found that Gdap1 knockout mice (Gdap1−/−), mimicking genetic alterations of patients suffering from severe forms of Charcot–Marie–Tooth disease, develop an age-related, hypomyelinating peripheral neuropathy. Ablation of Gdap1 expression in Schwann cells recapitulates this phenotype. Additionally, intra-axonal mitochondria of peripheral neurons are larger in Gdap1−/− mice and mitochondrial transport is impaired in cultured sensory neurons of Gdap1−/− mice compared with controls. These changes in mitochondrial morphology and dynamics also influence mitochondrial biogenesis. We demonstrate that mitochondrial DNA biogenesis and content is increased in the peripheral nervous system but not in the central nervous system of Gdap1−/− mice compared with control littermates. In search for a molecular mechanism we turned to the paralogue of GDAP1, GDAP1L1, which is mainly expressed in the unaffected central nervous system. GDAP1L1 responds to elevated levels of oxidized glutathione by translocating from the cytosol to mitochondria, where it inserts into the mitochondrial outer membrane. This translocation is necessary to substitute for loss of GDAP1 expression. Accordingly, more GDAP1L1 was associated with mitochondria in the spinal cord of aged Gdap1−/− mice compared with controls. Our findings demonstrate that Charcot–Marie–Tooth disease caused by mutations in GDAP1 leads to mild, persistent oxidative stress in the peripheral nervous system, which can be compensated by GDAP1L1 in the unaffected central nervous system. We conclude that members of the GDAP1 family are responsive and protective against stress associated with increased levels of oxidized glutathione.
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Affiliation(s)
- Axel Niemann
- 1 Institute of Molecular Health Sciences, Cell Biology, Department of Biology, ETH Zurich, Swiss Federal Institute of Technology, Switzerland, ETH-Hönggerberg, 8093 Zürich, Switzerland
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57
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Bereiter-Hahn J. Do we age because we have mitochondria? PROTOPLASMA 2014; 251:3-23. [PMID: 23794102 DOI: 10.1007/s00709-013-0515-x] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/19/2013] [Accepted: 05/21/2013] [Indexed: 06/02/2023]
Abstract
The process of aging remains a great riddle. Production of reactive oxygen species (ROS) by mitochondria is an inevitable by-product of respiration, which has led to a hypothesis proposing the oxidative impairment of mitochondrial components (e.g., mtDNA, proteins, lipids) that initiates a vicious cycle of dysfunctional respiratory complexes producing more ROS, which again impairs function. This does not exclude other processes acting in parallel or targets for ROS action in other organelles than mitochondria. Given that aging is defined as the process leading to death, the role of mitochondria-based impairments in those organ systems responsible for human death (e.g., the cardiovascular system, cerebral dysfunction, and cancer) is described within the context of "garbage" accumulation and increasing insulin resistance, type 2 diabetes, and glycation of proteins. Mitochondrial mass, fusion, and fission are important factors in coping with impaired function. Both biogenesis of mitochondria and their degradation are important regulatory mechanisms stimulated by physical exercise and contribute to healthy aging. The hypothesis of mitochondria-related aging should be revised to account for the limitations of the degradative capacity of the lysosomal system. The processes involved in mitochondria-based impairments are very similar across a large range of organisms. Therefore, studies on model organisms from yeast, fungi, nematodes, flies to vertebrates, and from cells to organisms also add considerably to the understanding of human aging.
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Affiliation(s)
- Jürgen Bereiter-Hahn
- Institut für Zellbiologie und Neurowissenschaften, Goethe Universität Frankfurt am Main, Max-von-Lauestrasse 13, 60438, Frankfurt am Main, Germany,
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58
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Bolea I, Gan WB, Manfedi G, Magrané J. Imaging of mitochondrial dynamics in motor and sensory axons of living mice. Methods Enzymol 2014; 547:97-110. [PMID: 25416354 DOI: 10.1016/b978-0-12-801415-8.00006-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Appropriate distribution and supply of mitochondria to critical neuronal sites are thought to be necessary for the normal maintenance of neuronal architecture and activity, including synaptic plasticity and function. Imaging of neurons in vitro has provided understanding of the basic mechanisms of mitochondrial transport and the regulation of mitochondrial dynamics. However, in vivo imaging studies of neurons are preferable to in vitro approaches because of the advantage of being performed in their natural environment. Here, we present useful protocols to image and study axonal transport of mitochondria in vivo, in the peripheral nerves of mice. Imaging in motor and sensory axons of living mice allows researchers to analyze mitochondrial dynamics in two distinct neuronal populations that are often affected in peripheral neuropathies.
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Affiliation(s)
- Irene Bolea
- Brain and Mind Research Institute, Weill Medical College of Cornell University, New York, USA
| | - Wen-Biao Gan
- Department of Physiology and Neuroscience, Skirball Institute, New York University School of Medicine, New York, USA
| | - Giovanni Manfedi
- Brain and Mind Research Institute, Weill Medical College of Cornell University, New York, USA
| | - Jordi Magrané
- Brain and Mind Research Institute, Weill Medical College of Cornell University, New York, USA.
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59
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Cho B, Choi SY, Cho HM, Kim HJ, Sun W. Physiological and pathological significance of dynamin-related protein 1 (drp1)-dependent mitochondrial fission in the nervous system. Exp Neurobiol 2013; 22:149-57. [PMID: 24167410 PMCID: PMC3807002 DOI: 10.5607/en.2013.22.3.149] [Citation(s) in RCA: 87] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2013] [Revised: 09/02/2013] [Accepted: 09/02/2013] [Indexed: 12/29/2022] Open
Abstract
Mitochondria are essential for proper neuronal morphogenesis and functions, as they are the major source of energy for neural development. The dynamic morphology of mitochondria determines the key functions of mitochondria. Several regulatory proteins such as dynamin-related protein 1 (Drp1) are required to maintain mitochondrial morphology via a balance between continuous fusion and fission. Activity of Drp1, a key regulator in mitochondrial fission, is modulated by multiple post-translation modifications and receptor interactions. In addition, numerous researches have revealed that the regulation of Drp1 activity and mitochondrial dynamics is closely associated with several neurodegenerative diseases such as Alzheimer's and Parkinson's diseases. In this article, we concisely review the recent findings about the biological importance of Drp1-mediated mitochondrial fission in neurons under physiological and pathological conditions.
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Affiliation(s)
- Bongki Cho
- Department of Anatomy, Korea University College of Medicine, Seoul 136-705, Korea
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60
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Katsetos CD, Koutzaki S, Melvin JJ. Mitochondrial dysfunction in neuromuscular disorders. Semin Pediatr Neurol 2013; 20:202-15. [PMID: 24331362 DOI: 10.1016/j.spen.2013.10.010] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
This review deciphers aspects of mitochondrial (mt) dysfunction among nosologically, pathologically, and genetically diverse diseases of the skeletal muscle, lower motor neuron, and peripheral nerve, which fall outside the traditional realm of mt cytopathies. Special emphasis is given to well-characterized mt abnormalities in collagen VI myopathies (Ullrich congenital muscular dystrophy and Bethlem myopathy), megaconial congenital muscular dystrophy, limb-girdle muscular dystrophy type 2 (calpainopathy), centronuclear myopathies, core myopathies, inflammatory myopathies, spinal muscular atrophy, Charcot-Marie-Tooth neuropathy type 2, and drug-induced peripheral neuropathies. Among inflammatory myopathies, mt abnormalities are more prominent in inclusion body myositis and a subset of polymyositis with mt pathology, both of which are refractory to corticosteroid treatment. Awareness is raised about instances of phenotypic mimicry between cases harboring primary mtDNA depletion, in the context of mtDNA depletion syndrome, and established neuromuscular disorders such as spinal muscular atrophy. A substantial body of experimental work, derived from animal models, attests to a major role of mitochondria (mt) in the early process of muscle degeneration. Common mechanisms of mt-related cell injury include dysregulation of the mt permeability transition pore opening and defective autophagy. The therapeutic use of mt permeability transition pore modifiers holds promise in various neuromuscular disorders, including muscular dystrophies.
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Affiliation(s)
- Christos D Katsetos
- Department of Pediatrics, Drexel University College of Medicine, St. Christopher's Hospital for Children, Philadelphia, PA; Department of Pathology and Laboratory Medicine, Drexel University College of Medicine, Philadelphia, PA; Department of Neurology, Drexel University College of Medicine, Philadelphia, PA.
| | - Sirma Koutzaki
- Department of Pathology and Laboratory Medicine, Drexel University College of Medicine, Philadelphia, PA
| | - Joseph J Melvin
- Department of Pediatrics, Drexel University College of Medicine, St. Christopher's Hospital for Children, Philadelphia, PA; Department of Neurology, Drexel University College of Medicine, Philadelphia, PA
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61
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Guo BL, Sui BD, Wang XY, Wei YY, Huang J, Chen J, Wu SX, Li YQ, Wang YY, Yang YL. Significant changes in mitochondrial distribution in different pain models of mice. Mitochondrion 2013; 13:292-7. [DOI: 10.1016/j.mito.2013.03.007] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2012] [Revised: 02/23/2013] [Accepted: 03/19/2013] [Indexed: 11/25/2022]
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62
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Abstract
Neurons, perhaps more than any other cell type, depend on mitochondrial trafficking for their survival. Recent studies have elucidated a motor/adaptor complex on the mitochondrial surface that is shared between neurons and other animal cells. In addition to kinesin and dynein, this complex contains the proteins Miro (also called RhoT1/2) and milton (also called TRAK1/2) and is responsible for much, although not necessarily all, mitochondrial movement. Elucidation of the complex has permitted inroads for understanding how this movement is regulated by a variety of intracellular signals, although many mysteries remain. Regulating mitochondrial movement can match energy demand to energy supply throughout the extraordinary architecture of these cells and can control the clearance and replenishing of mitochondria in the periphery. Because the extended axons of neurons contain uniformly polarized microtubules, they have been useful for studying mitochondrial motility in conjunction with biochemical assays in many cell types.
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Affiliation(s)
- Thomas L Schwarz
- F.M. Kirby Neurobiology Center, Children's Hospital Boston, and Department of Neurobiology, Harvard Medical School, Boston, Massachusetts 02115, USA.
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63
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Gillingwater TH, Wishart TM. Mechanisms underlying synaptic vulnerability and degeneration in neurodegenerative disease. Neuropathol Appl Neurobiol 2013; 39:320-34. [PMID: 23289367 DOI: 10.1111/nan.12014] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2012] [Accepted: 12/21/2012] [Indexed: 02/06/2023]
Abstract
Recent developments in our understanding of events underlying neurodegeneration across the central and peripheral nervous systems have highlighted the critical role that synapses play in the initiation and progression of neuronal loss. With the development of increasingly accurate and versatile animal models of neurodegenerative disease it has become apparent that disruption of synaptic form and function occurs comparatively early, preceding the onset of degenerative changes in the neuronal cell body. Yet, despite our increasing awareness of the importance of synapses in neurodegeneration, the mechanisms governing the particular susceptibility of distal neuronal processes are only now becoming clear. In this review we bring together recent developments in our understanding of cellular and molecular mechanisms regulating synaptic vulnerability. We have placed a particular focus on three major areas of research that have gained significant interest over the last few years: (i) the contribution of synaptic mitochondria to neurodegeneration; (ii) the contribution of pathways that modulate synaptic function; and (iii) regulation of synaptic degeneration by local posttranslational modifications such as ubiquitination. We suggest that targeting these organelles and pathways may be a productive way to develop synaptoprotective strategies applicable to a range of neurodegenerative conditions.
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Affiliation(s)
- T H Gillingwater
- Centre for Integrative Physiology, University of Edinburgh, Edinburgh, UK
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64
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Viader A, Sasaki Y, Kim S, Strickland A, Workman CS, Yang K, Gross RW, Milbrandt J. Aberrant Schwann cell lipid metabolism linked to mitochondrial deficits leads to axon degeneration and neuropathy. Neuron 2013; 77:886-98. [PMID: 23473319 PMCID: PMC3594792 DOI: 10.1016/j.neuron.2013.01.012] [Citation(s) in RCA: 184] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/11/2013] [Indexed: 02/06/2023]
Abstract
Mitochondrial dysfunction is a common cause of peripheral neuropathy. Much effort has been devoted to examining the role played by neuronal/axonal mitochondria, but how mitochondrial deficits in peripheral nerve glia (Schwann cells [SCs]) contribute to peripheral nerve diseases remains unclear. Here, we investigate a mouse model of peripheral neuropathy secondary to SC mitochondrial dysfunction (Tfam-SCKOs). We show that disruption of SC mitochondria activates a maladaptive integrated stress response (ISR) through the actions of heme-regulated inhibitor (HRI) kinase, and causes a shift in lipid metabolism away from fatty acid synthesis toward oxidation. These alterations in SC lipid metabolism result in depletion of important myelin lipid components as well as in accumulation of acylcarnitines (ACs), an intermediate of fatty acid β-oxidation. Importantly, we show that ACs are released from SCs and induce axonal degeneration. A maladaptive ISR as well as altered SC lipid metabolism are thus underlying pathological mechanisms in mitochondria-related peripheral neuropathies.
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Affiliation(s)
- Andreu Viader
- Department of Genetics, Washington University School of Medicine, St. Louis, MO
| | - Yo Sasaki
- Department of Genetics, Washington University School of Medicine, St. Louis, MO
| | - Sungsu Kim
- Department of Genetics, Washington University School of Medicine, St. Louis, MO
| | - Amy Strickland
- Department of Genetics, Washington University School of Medicine, St. Louis, MO
| | - Cayce S. Workman
- Department of Genetics, Washington University School of Medicine, St. Louis, MO
| | - Kui Yang
- Division of Bioorganic Chemistry and Molecular Pharmacology, Department of Internal Medicine, Washington University School of Medicine, St. Louis, MO
| | - Richard W. Gross
- Division of Bioorganic Chemistry and Molecular Pharmacology, Department of Internal Medicine, Washington University School of Medicine, St. Louis, MO
| | - Jeffrey Milbrandt
- Department of Genetics, Washington University School of Medicine, St. Louis, MO
- Hope Center for Neurological Diseases, Washington University School of Medicine, St. Louis, MO
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65
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Paul S, Das N, Bhattacharjee P, Banerjee M, Das JK, Sarma N, Sarkar A, Bandyopadhyay AK, Sau TJ, Basu S, Banerjee S, Majumder P, Giri AK. Arsenic-induced toxicity and carcinogenicity: a two-wave cross-sectional study in arsenicosis individuals in West Bengal, India. JOURNAL OF EXPOSURE SCIENCE & ENVIRONMENTAL EPIDEMIOLOGY 2013; 23:156-162. [PMID: 22990472 DOI: 10.1038/jes.2012.91] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/18/2012] [Revised: 07/04/2012] [Accepted: 07/08/2012] [Indexed: 06/01/2023]
Abstract
In the state of West Bengal in India, over 26 million individuals are exposed to arsenic via drinking water. Dermatological, non-dermatological disorders and cancers are associated with arsenic toxicity. Of late, there has been a decrease in the arsenic concentration in drinking water owing to governmental efforts, raising the possibility of remediation. A cross-sectional study was conducted, where 189 arsenicosis and 171 unexposed individuals were recruited at two time points, (2005-06 and 2010-11) with concomitant decrease in the level of arsenic exposure via drinking water in the arsenicosis group in 2010-11. Parameters studied included dermatological, non-dermatological health status and cytogenetic damage. Decrease of arsenic exposure (190.1 μg/l to 37.94 μg/l) resulted in significant decline in the number of individuals having dermatological disorders (P<0.01) and in the severity of each dermatological outcome (P<0.0001). Micronucleus formation in urothelial cells and lymphocytes decreased significantly (P<0.001). However, there was a significant (P<0.001) rise in the incidence of each of the non-dermatological diseases, that is, peripheral neuropathy, conjunctivitis and respiratory distress over the period. Thirteen (6.87%) of the initially recruited arsenicosis individuals died of cancer, in this period. Remediation by arsenic-safe drinking water can reduce dermatological manifestations and cytogenetic insult; but is unable to counter the non-dermatological symptoms.
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Affiliation(s)
- Somnath Paul
- Molecular and Human Genetics Division, Indian Institute of Chemical Biology (A Unit of Council of Scientific and Industrial Research, New Delhi), 4 Raja S. C. Mullick Road, Jadavpur, Kolkata, India
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66
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Lovas JR, Wang X. The meaning of mitochondrial movement to a neuron's life. BIOCHIMICA ET BIOPHYSICA ACTA 2013; 1833:184-94. [PMID: 22548961 PMCID: PMC3413748 DOI: 10.1016/j.bbamcr.2012.04.007] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/09/2012] [Revised: 04/13/2012] [Accepted: 04/14/2012] [Indexed: 11/21/2022]
Abstract
Cells precisely regulate mitochondrial movement in order to balance energy needs and avoid cell death. Neurons are particularly susceptible to disturbance of mitochondrial motility and distribution due to their highly extended structures and specialized function. Regulation of mitochondrial motility plays a vital role in neuronal health and death. Here we review the current understanding of regulatory mechanisms that govern neuronal mitochondrial transport and probe their implication in health and disease. This article is part of a Special Issue entitled: Mitochondrial dynamics and physiology.
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Affiliation(s)
- Jonathan R. Lovas
- Stanford Institute for Neuro-innovation and Translational Neurosciences and Department of Neurosurgery, Stanford University School of Medicine
| | - Xinnan Wang
- Stanford Institute for Neuro-innovation and Translational Neurosciences and Department of Neurosurgery, Stanford University School of Medicine
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Fuller BF, Cortes DF, Landis MK, Yohannes H, Griffin HE, Stafflinger JE, Bowers MS, Lewis MH, Fox MA, Ottens AK. Exposure of rats to environmental tobacco smoke during cerebellar development alters behavior and perturbs mitochondrial energetics. ENVIRONMENTAL HEALTH PERSPECTIVES 2012; 120:1684-1691. [PMID: 23014793 PMCID: PMC3548280 DOI: 10.1289/ehp.1104857] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/14/2011] [Accepted: 09/26/2012] [Indexed: 06/01/2023]
Abstract
BACKGROUND Environmental tobacco smoke (ETS) exposure is linked to developmental deficits and disorders with known cerebellar involvement. However, direct biological effects and underlying neurochemical mechanisms remain unclear. OBJECTIVES We sought to identify and evaluate underlying neurochemical change in the rat cerebellum with ETS exposure during critical period development. METHODS We exposed rats to daily ETS (300, 100, and 0 µg/m3 total suspended particulate) from postnatal day 8 (PD8) to PD23 and then assayed the response at the behavioral, neuroproteomic, and cellular levels. RESULTS Postnatal ETS exposure induced heightened locomotor response in a novel environment on par initially with amphetamine stimulation. The cerebellar mitochondrial subproteome was significantly perturbed in the ETS-exposed rats. Findings revealed a dose-dependent up-regulation of aerobic processes through the modification and increased translocation of Hk1 to the mitochondrion with corresponding heightened ATP synthase expression. ETS exposure also induced a dose-dependent increase in total Dnm1l mitochondrial fission factor; although more active membrane-bound Dnm1l was found at the lower dose. Dnm1l activation was associated with greater mitochondrial staining, particularly in the molecular layer, which was independent of stress-induced Bcl-2 family dynamics. Further, electron microscopy associated Dnm1l-mediated mitochondrial fission with increased biogenesis, rather than fragmentation. CONCLUSIONS The critical postnatal period of cerebellar development is vulnerable to the effects of ETS exposure, resulting in altered behavior. The biological effect of ETS is underlain in part by a Dnm1l-mediated mitochondrial energetic response at a time of normally tight control. These findings represent a novel mechanism by which environmental exposure can impact neurodevelopment and function.
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Affiliation(s)
- Brian F Fuller
- Department of Anatomy and Neurobiology, Virginia Commonwealth University, Richmond, Virginia 23298-0709, USA
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68
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Casanova-Molla J, Morales M, Garrabou G, Solà-Valls N, Soriano A, Calvo M, Grau JM, Valls-Solé J. Mitochondrial loss indicates early axonal damage in small fiber neuropathies. J Peripher Nerv Syst 2012; 17:147-57. [PMID: 22734900 DOI: 10.1111/j.1529-8027.2012.00396.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Evaluation of nerve fibers in the skin provides a useful tool for the diagnosis of small fiber neuropathies (SFNs). Our aim was to determine whether mitochondria are involved in SFN, indicating early axonal damage. We quantified mitochondrial respiratory chain complex IV (OXPHOS) and axonal (PGP 9.5) fluorescence on skin sections from 32 SFN patients and 14 healthy controls. Also, a group of six patients were recruited before and after 30-day treatment with the mitotoxic antibiotic linezolid. We measured the co-localization of OXPHOS within the intraepidermal and subpapillary dermal axons (PGP-immunoreactive [PGP-ir]). SFN patients with relatively preserved intraepidermal nerve fibers (SFN borderline) showed statistically significant reduction of OXPHOS (50.5 ± 33.9 µm(2) vs. 107.6 ± 81 µm(2) in controls, p < 0.02). A positive correlation was found between both PGP-ir and OXPHOS in controls (Pearson's coefficient r = 0.59, p < 0.001), whereas such correlation was absent in SFN. With respect to baseline measurements, linezolid therapy increased both PGP-ir and OXPHOS, which could be considered an initial compensatory toxic-induced response. This study set out to identify a possible marker of axonal pre-degenerative state in SFN borderline patients.
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Affiliation(s)
- Jordi Casanova-Molla
- Department of Neurology, Hospital Clinic IDIBAPS-Institut d'Investigació Augustí Pi i Sunyer, University of Barcelona, Barcelona, Spain.
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69
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Kawaguchi K. Role of kinesin-1 in the pathogenesis of SPG10, a rare form of hereditary spastic paraplegia. Neuroscientist 2012; 19:336-44. [PMID: 22785106 DOI: 10.1177/1073858412451655] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Molecular protein motors play key roles in processes such as intracellular cargo transport and brain wiring, and failure of function can give rise to serious diseases. Kinesin-1, a member of the kinesin superfamily (also known as KIFs) is a two-headed motor protein that uses energy derived from ATP hydrolysis to transport diverse types of intracellular cargo toward the plus-ends of microtubules within axons. Recent studies at the level of a single molecule have provided extensive knowledge on how kinesin-1 moves along microtubules. Further elucidation of kinesin-1 movement may shed light on its influence on axon generation, thereby leading to therapies for diseases such as spastic paraplegia type 10 (SPG10), the subject of this review. SPG10 is an autosomal dominant form of hereditary spastic paraplegia caused by mutations in KIF5A, which encodes one of the isoforms of kinesin-1 (KIF5A, KIF5B, and KIF5C). Although little is known about the cargo of KIF5A, a recent study revealed an axonal transport defect of mitochondria in a KIF5A (-/-) mouse model. This review discusses the consensus moving model of kinesin-1 and the pathogenicity of SPG10 caused by defective KIF5A function.
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Affiliation(s)
- Kenji Kawaguchi
- Graduate School of Medicine, Chiba University, Chiba, Japan.
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70
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Patel KP, O’Brien TW, Subramony SH, Shuster J, Stacpoole PW. The spectrum of pyruvate dehydrogenase complex deficiency: clinical, biochemical and genetic features in 371 patients. Mol Genet Metab 2012; 106:385-94. [PMID: 22896851 PMCID: PMC4003492 DOI: 10.1016/j.ymgme.2012.03.017] [Citation(s) in RCA: 127] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
CONTEXT Pyruvate dehydrogenase complex (PDC) deficiency is a genetic mitochondrial disorder commonly associated with lactic acidosis, progressive neurological and neuromuscular degeneration and, usually, death during childhood. There has been no recent comprehensive analysis of the natural history and clinical course of this disease. OBJECTIVE We reviewed 371 cases of PDC deficiency, published between 1970 and 2010, that involved defects in subunits E1α and E1β and components E1, E2, E3 and the E3 binding protein of the complex. DATA SOURCES AND EXTRACTION English language peer-reviewed publications were identified, primarily by using PubMed and Google Scholar search engines. RESULTS Neurodevelopmental delay and hypotonia were the commonest clinical signs of PDC deficiency. Structural brain abnormalities frequently included ventriculomegaly, dysgenesis of the corpus callosum and neuroimaging findings typical of Leigh syndrome. Neither gender nor any clinical or neuroimaging feature differentiated the various biochemical etiologies of the disease. Patients who died were younger, presented clinically earlier and had higher blood lactate levels and lower residual enzyme activities than subjects who were still alive at the time of reporting. Survival bore no relationship to the underlying biochemical or genetic abnormality or to gender. CONCLUSIONS Although the clinical spectrum of PDC deficiency is broad, the dominant clinical phenotype includes presentation during the first year of life; neurological and neuromuscular degeneration; structural lesions revealed by neuroimaging; lactic acidosis and a blood lactate:pyruvate ratio ≤ 20.
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Affiliation(s)
- Kavi P. Patel
- Department of Medicine (Division of Endocrinology, Metabolism and
Diabetes), College of Medicine, University of Florida, Gainesville, FL 32611,
USA
| | - Thomas W. O’Brien
- Department of Biochemistry and Molecular Biology, College of
Medicine, University of Florida, Gainesville, FL 32611, USA
| | | | - Jonathan Shuster
- Department of Epidemiology and Health Policy Research, College of
Medicine, University of Florida, Gainesville, FL 32611, USA
| | - Peter W. Stacpoole
- Department of Medicine (Division of Endocrinology, Metabolism and
Diabetes), College of Medicine, University of Florida, Gainesville, FL 32611,
USA
- Department of Biochemistry and Molecular Biology, College of
Medicine, University of Florida, Gainesville, FL 32611, USA
- Corresponding author at: UF College of Medicine, 1600 SW
Archer Road M2-238, P.O. Box 100226, Gainesville, FL 32610, USA. Fax: +1
352 273 9013. (P.W. Stacpoole)
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71
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Neural and molecular features on Charcot-Marie-Tooth disease plasticity and therapy. Neural Plast 2012; 2012:171636. [PMID: 22745917 PMCID: PMC3382403 DOI: 10.1155/2012/171636] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2012] [Accepted: 04/16/2012] [Indexed: 12/21/2022] Open
Abstract
In the peripheral nervous system disorders plasticity is related to changes on the axon and Schwann cell biology, and the synaptic formations and connections, which could be also a focus for therapeutic research. Charcot-Marie-Tooth disease (CMT) represents a large group of inherited peripheral neuropathies that involve mainly both motor and sensory nerves and induce muscular atrophy and weakness. Genetic analysis has identified several pathways and molecular mechanisms involving myelin structure and proper nerve myelination, transcriptional regulation, protein turnover, vesicle trafficking, axonal transport and mitochondrial dynamics. These pathogenic mechanisms affect the continuous signaling and dialogue between the Schwann cell and the axon, having as final result the loss of myelin and nerve maintenance; however, some late onset axonal CMT neuropathies are a consequence of Schwann cell specific changes not affecting myelin. Comprehension of molecular pathways involved in Schwann cell-axonal interactions is likely not only to increase the understanding of nerve biology but also to identify the molecular targets and cell pathways to design novel therapeutic approaches for inherited neuropathies but also for most common peripheral neuropathies. These approaches should improve the plasticity of the synaptic connections at the neuromuscular junction and regenerate cell viability based on improving myelin and axon interaction.
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72
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Zhang CL, Rodenkirch L, Schultz JR, Chiu SY. A novel method to study the local mitochondrial fusion in myelinated axons in vivo. J Neurosci Methods 2012; 207:51-8. [PMID: 22484559 PMCID: PMC3364104 DOI: 10.1016/j.jneumeth.2012.03.013] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2011] [Revised: 03/20/2012] [Accepted: 03/22/2012] [Indexed: 11/20/2022]
Abstract
Mitochondrial remodeling (replication, fission/fusion) is a dynamically regulated process with diverse functions in neurons. A myelinated axon is an extension from the cell soma of a fully differentiated neuron. Mitochondria, once synthesized in the cell body, enter the axon displaying robust trafficking and accumulation at nodes of Ranvier to match metabolic needs. This long-distance deployment of mitochondria to axons raises the issue of whether myelinated axons can function independently of the cell body to execute mitochondrial remodeling to match local demands. Mitochondrial fusion has been suggested to occur in axons in simple neuronal cultures in vitro. However, whether such events occur in vivo in an intact nervous system remains unanswered. Here we describe a novel technique which allows monitoring of mitochondrial fusion in intact sciatic nerve of frog (Xenopus laevis). Mitochondrial population was labeled by injecting two different MitoTracker dyes (Red and Green), spatially apart along sciatic nerves surgically and then allow to "meet"in vivo. At 24h post-surgery, the sciatic nerves were taken out for mitochondrial imaging at the half-way point. During the post-injection periods, the anterograde-directed Green mitochondria meet with the retrograde-directed Red mitochondria. If fusion occurs, the merged of Green and Red fluorophores in the same mitochondrion will produce a Yellow color in merged images. The labeled mitochondria were observed with a Nikon A1 confocal microscope. Our new mitochondrial imaging method opens an avenue to separately assess the role of local axonal mitochondrial fusion, independent of the cell body of nerve fibers.
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Affiliation(s)
- Chuan-Li Zhang
- Dept. of Neuroscience, 1300 University Avenue, University of Wisconsin School of Medicine and Public Health, Madison, WI 53706, USA
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73
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Bucci C, Bakke O, Progida C. Charcot-Marie-Tooth disease and intracellular traffic. Prog Neurobiol 2012; 99:191-225. [PMID: 22465036 PMCID: PMC3514635 DOI: 10.1016/j.pneurobio.2012.03.003] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2011] [Revised: 12/23/2011] [Accepted: 03/13/2012] [Indexed: 12/23/2022]
Abstract
Mutations of genes whose primary function is the regulation of membrane traffic are increasingly being identified as the underlying causes of various important human disorders. Intriguingly, mutations in ubiquitously expressed membrane traffic genes often lead to cell type- or organ-specific disorders. This is particularly true for neuronal diseases, identifying the nervous system as the most sensitive tissue to alterations of membrane traffic. Charcot-Marie-Tooth (CMT) disease is one of the most common inherited peripheral neuropathies. It is also known as hereditary motor and sensory neuropathy (HMSN), which comprises a group of disorders specifically affecting peripheral nerves. This peripheral neuropathy, highly heterogeneous both clinically and genetically, is characterized by a slowly progressive degeneration of the muscle of the foot, lower leg, hand and forearm, accompanied by sensory loss in the toes, fingers and limbs. More than 30 genes have been identified as targets of mutations that cause CMT neuropathy. A number of these genes encode proteins directly or indirectly involved in the regulation of intracellular traffic. Indeed, the list of genes linked to CMT disease includes genes important for vesicle formation, phosphoinositide metabolism, lysosomal degradation, mitochondrial fission and fusion, and also genes encoding endosomal and cytoskeletal proteins. This review focuses on the link between intracellular transport and CMT disease, highlighting the molecular mechanisms that underlie the different forms of this peripheral neuropathy and discussing the pathophysiological impact of membrane transport genetic defects as well as possible future ways to counteract these defects.
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Affiliation(s)
- Cecilia Bucci
- Department of Biological and Environmental Sciences and Technologies (DiSTeBA), University of Salento, Via Provinciale Monteroni, 73100 Lecce, Italy.
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74
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Misko AL, Sasaki Y, Tuck E, Milbrandt J, Baloh RH. Mitofusin2 mutations disrupt axonal mitochondrial positioning and promote axon degeneration. J Neurosci 2012; 32:4145-55. [PMID: 22442078 PMCID: PMC3319368 DOI: 10.1523/jneurosci.6338-11.2012] [Citation(s) in RCA: 144] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2011] [Revised: 01/27/2012] [Accepted: 02/03/2012] [Indexed: 11/21/2022] Open
Abstract
Alterations in mitochondrial dynamics (fission, fusion, and movement) are implicated in many neurodegenerative diseases, from rare genetic disorders such as Charcot-Marie-Tooth disease, to common conditions including Alzheimer's disease. However, the relationship between altered mitochondrial dynamics and neurodegeneration is incompletely understood. Here we show that disease associated MFN2 proteins suppressed both mitochondrial fusion and transport, and produced classic features of segmental axonal degeneration without cell body death, including neurofilament filled swellings, loss of calcium homeostasis, and accumulation of reactive oxygen species. By contrast, depletion of Opa1 suppressed mitochondrial fusion while sparing transport, and did not induce axonal degeneration. Axon degeneration induced by mutant MFN2 proteins correlated with the disruption of the proper mitochondrial positioning within axons, rather than loss of overall mitochondrial movement, or global mitochondrial dysfunction. We also found that augmenting expression of MFN1 rescued the axonal degeneration caused by MFN2 mutants, suggesting a possible therapeutic strategy for Charcot-Marie-Tooth disease. These experiments provide evidence that the ability of mitochondria to sense energy requirements and localize properly within axons is key to maintaining axonal integrity, and may be a common pathway by which disruptions in axonal transport contribute to neurodegeneration.
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Affiliation(s)
| | | | | | - Jeffrey Milbrandt
- Genetics, and
- Hope Center for Neurological Diseases, Washington University School of Medicine, St Louis, Missouri 63110, and
| | - Robert H. Baloh
- Departments of Neurology and
- Hope Center for Neurological Diseases, Washington University School of Medicine, St Louis, Missouri 63110, and
- Department of Neurology, Regenerative Medicine Institute, Cedars-Sinai Medical Center, Los Angeles, California 90048
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75
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Liu S, Sawada T, Lee S, Yu W, Silverio G, Alapatt P, Millan I, Shen A, Saxton W, Kanao T, Takahashi R, Hattori N, Imai Y, Lu B. Parkinson's disease-associated kinase PINK1 regulates Miro protein level and axonal transport of mitochondria. PLoS Genet 2012; 8:e1002537. [PMID: 22396657 PMCID: PMC3291531 DOI: 10.1371/journal.pgen.1002537] [Citation(s) in RCA: 293] [Impact Index Per Article: 24.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2011] [Accepted: 12/29/2011] [Indexed: 11/18/2022] Open
Abstract
Mutations in Pten-induced kinase 1 (PINK1) are linked to early-onset familial Parkinson's disease (FPD). PINK1 has previously been implicated in mitochondrial fission/fusion dynamics, quality control, and electron transport chain function. However, it is not clear how these processes are interconnected and whether they are sufficient to explain all aspects of PINK1 pathogenesis. Here we show that PINK1 also controls mitochondrial motility. In Drosophila, downregulation of dMiro or other components of the mitochondrial transport machinery rescued dPINK1 mutant phenotypes in the muscle and dopaminergic (DA) neurons, whereas dMiro overexpression alone caused DA neuron loss. dMiro protein level was increased in dPINK1 mutant but decreased in dPINK1 or dParkin overexpression conditions. In Drosophila larval motor neurons, overexpression of dPINK1 inhibited axonal mitochondria transport in both anterograde and retrograde directions, whereas dPINK1 knockdown promoted anterograde transport. In HeLa cells, overexpressed hPINK1 worked together with hParkin, another FPD gene, to regulate the ubiquitination and degradation of hMiro1 and hMiro2, apparently in a Ser-156 phosphorylation-independent manner. Also in HeLa cells, loss of hMiro promoted the perinuclear clustering of mitochondria and facilitated autophagy of damaged mitochondria, effects previously associated with activation of the PINK1/Parkin pathway. These newly identified functions of PINK1/Parkin and Miro in mitochondrial transport and mitophagy contribute to our understanding of the complex interplays in mitochondrial quality control that are critically involved in PD pathogenesis, and they may explain the peripheral neuropathy symptoms seen in some PD patients carrying particular PINK1 or Parkin mutations. Moreover, the different effects of loss of PINK1 function on Miro protein level in Drosophila and mouse cells may offer one explanation of the distinct phenotypic manifestations of PINK1 mutants in these two species. Parkinson's disease (PD) is the second most common neurodegenerative disease. It mainly affects movement in elderly people and was traditionally considered a sporadic disease with no known cause. Discoveries of genes associated with familial PD (FPD) have demonstrated that PD pathogenesis can be significantly influenced by an individual's genetic makeup. Understanding the functions of these FPD genes will allow better understanding of the sporadic PD cases. PINK1 and Parkin are genes associated with FPD that affect patients at an early age. Mutations in PINK1 and Parkin lead to the accumulation of damaged mitochondria, the powerhouse of the cell, as a result of impairments of the mitochondrial quality control system. However, the mechanism of PINK1/Parkin action remains poorly understood. Here we show that PINK1 and Parkin act together to regulate Miro, a key component of the mitochondrial transport machinery, and that altered activities of PINK1 cause aberrant mitochondrial transport. Regulation of mitochondrial transport may be a critical aspect of the mechanisms by which the PINK1/Parkin pathway governs mitochondrial quality control. Dysfunction of this process could contribute to the loss of DA neurons, the cardinal feature of PD, as well as the peripheral neuropathy symptom associated with particular PINK1 or Parkin mutations.
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Affiliation(s)
- Song Liu
- Department of Pathology, Stanford University School of Medicine, Stanford, California, United States of America
| | - Tomoyo Sawada
- Department of Neurology, Graduate School of Medicine, Kyoto University, Kyoto, Japan
- CREST (Core Research for Evolutionary Science and Technology), Japan Science and Technology Agency, Saitama, Japan
| | - Seongsoo Lee
- Department of Pathology, Stanford University School of Medicine, Stanford, California, United States of America
| | - Wendou Yu
- Department of Pathology, Stanford University School of Medicine, Stanford, California, United States of America
| | - George Silverio
- Department of Pathology, Stanford University School of Medicine, Stanford, California, United States of America
| | - Philomena Alapatt
- Department of Pathology, Stanford University School of Medicine, Stanford, California, United States of America
| | - Ivan Millan
- Neuroscience Program, Stanford University School of Medicine, Stanford, California, United States of America
| | - Alice Shen
- College of Arts and Sciences, Washington University, St. Louis, Missouri, United States of America
| | - William Saxton
- Department of Molecular, Cell, and Developmental Biology, University of California Santa Cruz, Santa Cruz, California, United States of America
| | - Tomoko Kanao
- Research Institute for Diseases of Old Age, Juntendo University Graduate School of Medicine, Tokyo, Japan
| | - Ryosuke Takahashi
- Department of Neurology, Graduate School of Medicine, Kyoto University, Kyoto, Japan
- CREST (Core Research for Evolutionary Science and Technology), Japan Science and Technology Agency, Saitama, Japan
| | - Nobutaka Hattori
- CREST (Core Research for Evolutionary Science and Technology), Japan Science and Technology Agency, Saitama, Japan
- Department of Neurology, Juntendo University Graduate School of Medicine, Tokyo, Japan
| | - Yuzuru Imai
- Department of Neuroscience for Neurodegenerative Disorders, Juntendo University Graduate School of Medicine, Tokyo, Japan
- * E-mail: (YI); (BL)
| | - Bingwei Lu
- Department of Pathology, Stanford University School of Medicine, Stanford, California, United States of America
- * E-mail: (YI); (BL)
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76
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Patel KP, O'Brien TW, Subramony SH, Shuster J, Stacpoole PW. The spectrum of pyruvate dehydrogenase complex deficiency: clinical, biochemical and genetic features in 371 patients. Mol Genet Metab 2012; 105:34-43. [PMID: 22079328 PMCID: PMC3754811 DOI: 10.1016/j.ymgme.2011.09.032] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/02/2011] [Revised: 09/27/2011] [Accepted: 09/27/2011] [Indexed: 01/01/2023]
Abstract
CONTEXT Pyruvate dehydrogenase complex (PDC) deficiency is a genetic mitochondrial disorder commonly associated with lactic acidosis, progressive neurological and neuromuscular degeneration and, usually, death during childhood. There has been no recent comprehensive analysis of the natural history and clinical course of this disease. OBJECTIVE We reviewed 371 cases of PDC deficiency, published between 1970 and 2010, that involved defects in subunits E1α and E1β and components E1, E2, E3 and the E3 binding protein of the complex. DATA SOURCES AND EXTRACTION English language peer-reviewed publications were identified, primarily by using PubMed and Google Scholar search engines. RESULTS Neurodevelopmental delay and hypotonia were the commonest clinical signs of PDC deficiency. Structural brain abnormalities frequently included ventriculomegaly, dysgenesis of the corpus callosum and neuroimaging findings typical of Leigh syndrome. Neither gender nor any clinical or neuroimaging feature differentiated the various biochemical etiologies of the disease. Patients who died were younger, presented clinically earlier and had higher blood lactate levels and lower residual enzyme activities than subjects who were still alive at the time of reporting. Survival bore no relationship to the underlying biochemical or genetic abnormality or to gender. CONCLUSIONS Although the clinical spectrum of PDC deficiency is broad, the dominant clinical phenotype includes presentation during the first year of life; neurological and neuromuscular degeneration; structural lesions revealed by neuroimaging; lactic acidosis and a blood lactate:pyruvate ratio ≤20.
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Affiliation(s)
- Kavi P. Patel
- Department of Medicine (Division of Endocrinology and Metabolism), College of Medicine, University of Florida, Gainesville, FL, 32611, USA
| | - Thomas W. O'Brien
- Department of Biochemistry and Molecular Biology College of Medicine, University of Florida, Gainesville, FL, 32611, USA
| | | | - Jonathan Shuster
- Epidemiology and Health Policy Research College of Medicine, University of Florida, Gainesville, FL, 32611, USA
| | - Peter W. Stacpoole
- Department of Medicine (Division of Endocrinology and Metabolism), College of Medicine, University of Florida, Gainesville, FL, 32611, USA
- Department of Biochemistry and Molecular Biology College of Medicine, University of Florida, Gainesville, FL, 32611, USA
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77
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Estacion M, Han C, Choi JS, Hoeijmakers JGJ, Lauria G, Drenth JPH, Gerrits MM, Dib-Hajj SD, Faber CG, Merkies ISJ, Waxman SG. Intra- and interfamily phenotypic diversity in pain syndromes associated with a gain-of-function variant of NaV1.7. Mol Pain 2011; 7:92. [PMID: 22136189 PMCID: PMC3248882 DOI: 10.1186/1744-8069-7-92] [Citation(s) in RCA: 87] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2011] [Accepted: 12/02/2011] [Indexed: 12/19/2022] Open
Abstract
BACKGROUND Sodium channel NaV1.7 is preferentially expressed within dorsal root ganglia (DRG), trigeminal ganglia and sympathetic ganglion neurons and their fine-diamter axons, where it acts as a threshold channel, amplifying stimuli such as generator potentials in nociceptors. Gain-of-function mutations and variants (single amino acid substitutions) of NaV1.7 have been linked to three pain syndromes: Inherited Erythromelalgia (IEM), Paroxysmal Extreme Pain Disorder (PEPD), and Small Fiber Neuropathy (SFN). IEM is characterized clinically by burning pain and redness that is usually focused on the distal extremities, precipitated by mild warmth and relieved by cooling, and is caused by mutations that hyperpolarize activation, slow deactivation, and enhance the channel ramp response. PEPD is characterized by perirectal, periocular or perimandibular pain, often triggered by defecation or lower body stimulation, and is caused by mutations that severely impair fast-inactivation. SFN presents a clinical picture dominated by neuropathic pain and autonomic symptoms; gain-of-function variants have been reported to be present in approximately 30% of patients with biopsy-confirmed idiopathic SFN, and functional testing has shown altered fast-inactivation, slow-inactivation or resurgent current. In this paper we describe three patients who house the NaV1.7/I228M variant. METHODS We have used clinical assessment of patients, quantitative sensory testing and skin biopsy to study these patients, including two siblings in one family, in whom genomic screening demonstrated the I228M NaV1.7 variant. Electrophysiology (voltage-clamp and current-clamp) was used to test functional effects of the variant channel. RESULTS We report three different clinical presentations of the I228M NaV1.7 variant: presentation with severe facial pain, presentation with distal (feet, hands) pain, and presentation with scalp discomfort in three patients housing this NaV1.7 variant, two of which are from a single family. We also demonstrate that the NaV1.7/I228M variant impairs slow-inactivation, and produces hyperexcitability in both trigeminal ganglion and DRG neurons. CONCLUSION Our results demonstrate intra- and interfamily phenotypic diversity in pain syndromes produced by a gain-of-function variant of NaV1.7.
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Affiliation(s)
- Mark Estacion
- Department of Neurology, Yale University School of Medicine, New Haven, CT 06510, and Center for Neuroscience and Regeneration Research, Veterans Affairs Medical Center, West Haven, CT 06516, USA
| | - Chongyang Han
- Department of Neurology, Yale University School of Medicine, New Haven, CT 06510, and Center for Neuroscience and Regeneration Research, Veterans Affairs Medical Center, West Haven, CT 06516, USA
| | - Jin-Sung Choi
- Department of Neurology, Yale University School of Medicine, New Haven, CT 06510, and Center for Neuroscience and Regeneration Research, Veterans Affairs Medical Center, West Haven, CT 06516, USA
- College of Pharmacy, Catholic University of Korea, Bucheon, South Korea
| | - Janneke GJ Hoeijmakers
- Department of Neurology, University Medical Center Maastricht, Maastricht, the Netherlands
| | - Giuseppe Lauria
- Neuromuscular Diseases Unit, IRCCS Foundation, "Carlo Besta", Milan, Italy
| | - Joost PH Drenth
- Department of Gastroenterology and Hepatology, Radboud University Nijmegen Medical Center, Nijmegen, the Netherlands
| | - Monique M Gerrits
- Department of Clinical Genetics, University Medical Center Maastricht, Maastricht, the Netherlands
| | - Sulayman D Dib-Hajj
- Department of Neurology, Yale University School of Medicine, New Haven, CT 06510, and Center for Neuroscience and Regeneration Research, Veterans Affairs Medical Center, West Haven, CT 06516, USA
| | - Catharina G Faber
- Department of Neurology, University Medical Center Maastricht, Maastricht, the Netherlands
| | - Ingemar SJ Merkies
- Department of Neurology, University Medical Center Maastricht, Maastricht, the Netherlands
- Department of Neurology, Spaarne Hospital, Hoofddorp, the Netherlands
| | - Stephen G Waxman
- Department of Neurology, Yale University School of Medicine, New Haven, CT 06510, and Center for Neuroscience and Regeneration Research, Veterans Affairs Medical Center, West Haven, CT 06516, USA
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Schmidt RE, Feng D, Wang Q, Green KG, Snipes LL, Yamin M, Brines M. Effect of insulin and an erythropoietin-derived peptide (ARA290) on established neuritic dystrophy and neuronopathy in Akita (Ins2 Akita) diabetic mouse sympathetic ganglia. Exp Neurol 2011; 232:126-35. [PMID: 21872588 PMCID: PMC3202026 DOI: 10.1016/j.expneurol.2011.05.025] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2011] [Revised: 04/28/2011] [Accepted: 05/26/2011] [Indexed: 01/23/2023]
Abstract
The Akita mouse is a robust model of diabetic autonomic neuropathy which develops severe diabetes following beta cell death, which occurs reproducibly at 3-4 weeks of age, and maintains the diabetic state without therapy for as long as 11 additional months. Neuritic dystrophy and neuronopathy involving prevertebral sympathetic superior mesenteric and celiac ganglia begin to develop within the first two months of onset of diabetes and are progressive with time. We have examined the effect of insulin implants resulting in normoglycemia and injections of ARA290, a small erythropoietin peptide which has no effect on glycemic parameters, on the reversal of established neuritic dystrophy and neuronopathy. We have found that 4 weeks of insulin therapy beginning at 2 months of diabetes resulted in normalization of blood glucose, body weight and HbA1c. Insulin therapy successfully reversed established neuritic dystrophy and neuronopathy to control levels. Numbers of sympathetic neurons were not significantly changed in either 3 month diabetic or insulin-treated Akita mice. Treatment with ARA290 for 7 weeks beginning at 4 months of diabetes did not result in altered metabolic severity of diabetes as measured by blood glucose, body weight or HbA1c levels. ARA290 treatment was able to decrease neuritic dystrophy by 55-74% compared to untreated diabetics or in comparison to a separate group of diabetic animals representing the 4 month treatment onset point. Surprisingly, there was no effect of ARA290 on ganglionic neuron number or ongoing neuronopathy (pale/degenerating neurons) in diabetic Akita mice during this time period. The development of neuroprotective EPO-like peptides may provide a possible future therapy for this debilitating complication of diabetes; however, it appears that discrete elements may be differentially targeted by the diabetic state and may require selective therapy.
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Affiliation(s)
- Robert E Schmidt
- Division of Neuropathology, Department of Pathology and Immunology, Washington University School of Medicine, Saint Louis, Missouri 63110, USA.
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79
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Viader A, Golden JP, Baloh RH, Schmidt RE, Hunter DA, Milbrandt J. Schwann cell mitochondrial metabolism supports long-term axonal survival and peripheral nerve function. J Neurosci 2011; 31:10128-40. [PMID: 21752989 PMCID: PMC3147283 DOI: 10.1523/jneurosci.0884-11.2011] [Citation(s) in RCA: 127] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2011] [Revised: 04/25/2011] [Accepted: 05/04/2011] [Indexed: 11/21/2022] Open
Abstract
Mitochondrial dysfunction is a common cause of peripheral neuropathies. While the role of neuron and axonal mitochondria in peripheral nerve disease is well appreciated, whether Schwann cell (SC) mitochondrial deficits contribute to peripheral neuropathies is unclear. Here, we examine how SC mitochondrial dysfunction affects axonal survival and contributes to the decline of peripheral nerve function by generating mice with SC-specific mitochondrial deficits. These mice (Tfam-SCKOs) were produced through the tissue-specific deletion of the mitochondrial transcription factor A gene (Tfam), which is essential for mitochondrial DNA (mtDNA) transcription and maintenance. Tfam-SCKOs were viable, but as they aged, they developed a progressive peripheral neuropathy characterized by nerve conduction abnormalities as well as extensive muscle denervation. Morphological examination of Tfam-SCKO nerves revealed early preferential loss of small unmyelinated fibers followed by prominent demyelination and degeneration of larger-caliber axons. Tfam-SCKOs displayed sensory and motor deficits consistent with this pathology. Remarkably, the severe mtDNA depletion and respiratory chain abnormalities in Tfam-SCKO mice did not affect SC proliferation or survival. Mitochondrial function in SCs is therefore essential for maintenance of axonal survival and normal peripheral nerve function, suggesting that SC mitochondrial dysfunction contributes to human peripheral neuropathies.
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Affiliation(s)
| | | | - Robert H. Baloh
- Department of Neurology
- Hope Center for Neurological Disorders, and
| | | | - Daniel A. Hunter
- Division of Plastic and Reconstructive Surgery, Washington University School of Medicine, St. Louis, Missouri 63110
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80
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Nekrasova OE, Mendez MG, Chernoivanenko IS, Tyurin-Kuzmin PA, Kuczmarski ER, Gelfand VI, Goldman RD, Minin AA. Vimentin intermediate filaments modulate the motility of mitochondria. Mol Biol Cell 2011; 22:2282-9. [PMID: 21562225 PMCID: PMC3128530 DOI: 10.1091/mbc.e10-09-0766] [Citation(s) in RCA: 97] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2010] [Revised: 04/19/2011] [Accepted: 05/05/2011] [Indexed: 12/17/2022] Open
Abstract
Interactions with vimentin intermediate filaments (VimIFs) affect the motility, distribution, and anchorage of mitochondria. In cells lacking VimIFs or in which VimIF organization is disrupted, the motility of mitochondria is increased relative to control cells that express normal VimIF networks. Expression of wild-type VimIF in vimentin-null cells causes mitochondrial motility to return to normal (slower) rates. In contrast, expressing vimentin with mutations in the mid-region of the N-terminal non-α-helical domain (deletions of residues 41-96 or 45-70, or substitution of Pro-57 with Arg) did not inhibit mitochondrial motility even though these mutants retain their ability to assemble into VimIFs in vivo. It was also found that a vimentin peptide consisting of residues 41-94 localizes to mitochondria. Taken together, these data suggest that VimIFs bind directly or indirectly to mitochondria and anchor them within the cytoplasm.
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Affiliation(s)
- Oxana E. Nekrasova
- Group of Cell Biology, Institute of Protein Research, Russian Academy of Sciences, Moscow 119988, Russia
| | - Melissa G. Mendez
- Department of Cell and Molecular Biology, Northwestern University's Feinberg School of Medicine, Chicago, IL 60611
| | - Ivan S. Chernoivanenko
- Group of Cell Biology, Institute of Protein Research, Russian Academy of Sciences, Moscow 119988, Russia
- Koltsov's Institute of Developmental Biology, Russian Academy of Sciences, 119334 Moscow, Russia
| | - Pyotr A. Tyurin-Kuzmin
- Group of Cell Biology, Institute of Protein Research, Russian Academy of Sciences, Moscow 119988, Russia
| | - Edward R. Kuczmarski
- Department of Cell and Molecular Biology, Northwestern University's Feinberg School of Medicine, Chicago, IL 60611
| | - Vladimir I. Gelfand
- Department of Cell and Molecular Biology, Northwestern University's Feinberg School of Medicine, Chicago, IL 60611
| | - Robert D. Goldman
- Department of Cell and Molecular Biology, Northwestern University's Feinberg School of Medicine, Chicago, IL 60611
| | - Alexander A. Minin
- Group of Cell Biology, Institute of Protein Research, Russian Academy of Sciences, Moscow 119988, Russia
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81
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Chu C, Levine E, Gear RW, Bogen O, Levine JD. Mitochondrial dependence of nerve growth factor-induced mechanical hyperalgesia. Pain 2011; 152:1832-1837. [PMID: 21570183 DOI: 10.1016/j.pain.2011.03.034] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2010] [Revised: 03/23/2011] [Accepted: 03/25/2011] [Indexed: 11/26/2022]
Abstract
Mitochondria are present at high concentration at the site of sensory transduction in the peripheral terminals of nociceptors. Because nerve growth factor (NGF), which induces nociceptor sensitization by acting on the high-affinity tropomyosin receptor kinase A (TrkA) receptor, also produces local recruitment of mitochondria in DRG neurons, we evaluated the role of mitochondria in NGF-induced mechanical hyperalgesia. Inhibition of 3 major mitochondrial functions-oxidation of nutrients, adenosine triphosphate (ATP) production, and generation of reactive oxygen species--markedly attenuated NGF-induced mechanical hyperalgesia in the rat. Disruption of microtubules, which are required for the trafficking and subcellular localization of mitochondria, also attenuated NGF-induced hyperalgesia. Our results suggest a contribution of mitochondrial localization and function to NGF-dependent pain syndromes.
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Affiliation(s)
- Carissa Chu
- Department of Oral and Maxillofacial Surgery, University of California, San Francisco, CA, USA Division of Neuroscience, University of California, San Francisco, CA, USA Department of Medicine, University of California, San Francisco, CA, USA
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82
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Abstract
Myelinated axons conduct nerve impulses at high speed using a unique mode of excitation, referred to as saltatory conduction, which is enabled structurally by the narrowing of the site of action potentials to a tiny gap in the axon called the node of Ranvier. With this structural specialization comes an interesting metabolic matching problem. How do mitochondria find and supply energy to these tiny nodes of Ranvier distributed sparsely along a myelinated axon? Does the intense Na(+) influx at the node, which is produced by the highest known sodium channel density in all excitable membranes, help guide where mitochondria stop? Evidence suggests that during excitation in the peripheral nervous system, Na(+) influx recruits mitochondria to the node by triggering Ca(2+) elevation and activating Na(+) pumps. Intriguingly, indirect evidence suggests that in the central nervous system, activity recruits mitochondria to the internode (myelin-covered portion of the axon). Metabolic dysfunction thus might produce spatially distinct lesions in PNS and CNS myelinated fibers. Future dissection of regional variation in mitochondrial biology in myelinated axons using live imaging will likely yield surprises about sites of vulnerability in demyelinating diseases and clues for therapeutic intervention strategy.
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Affiliation(s)
- Shing Y Chiu
- Department of Physiology, University of Wisconsin School of Medicine, Madison, WI 53706, USA.
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83
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Fischer LR, Igoudjil A, Magrané J, Li Y, Hansen JM, Manfredi G, Glass JD. SOD1 targeted to the mitochondrial intermembrane space prevents motor neuropathy in the Sod1 knockout mouse. ACTA ACUST UNITED AC 2010; 134:196-209. [PMID: 21078595 DOI: 10.1093/brain/awq314] [Citation(s) in RCA: 98] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Motor axon degeneration is a critical but poorly understood event leading to weakness and muscle atrophy in motor neuron diseases. Here, we investigated oxidative stress-mediated axonal degeneration in mice lacking the antioxidant enzyme, Cu,Zn superoxide dismutase (SOD1). We demonstrate a progressive motor axonopathy in these mice and show that Sod1(-/-) primary motor neurons extend short axons in vitro with reduced mitochondrial density. Sod1(-/-) neurons also show oxidation of mitochondrial--but not cytosolic--thioredoxin, suggesting that loss of SOD1 causes preferential oxidative stress in mitochondria, a primary source of superoxide in cells. SOD1 is widely regarded as the cytosolic isoform of superoxide dismutase, but is also found in the mitochondrial intermembrane space. The functional significance of SOD1 in the intermembrane space is unknown. We used a transgenic approach to express SOD1 exclusively in the intermembrane space and found that mitochondrial SOD1 is sufficient to prevent biochemical and morphological defects in the Sod1(-/-) model, and to rescue the motor phenotype of these mice when followed to 12 months of age. These results suggest that SOD1 in the mitochondrial intermembrane space is fundamental for motor axon maintenance, and implicate oxidative damage initiated at mitochondrial sites in the pathogenesis of motor axon degeneration.
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Affiliation(s)
- Lindsey R Fischer
- Department of Neurology, Emory University School of Medicine, Atlanta, GA 30322, USA
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84
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Perkins GA, Ellisman MH. Mitochondrial configurations in peripheral nerve suggest differential ATP production. J Struct Biol 2010; 173:117-27. [PMID: 20600951 DOI: 10.1016/j.jsb.2010.06.017] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2010] [Accepted: 06/21/2010] [Indexed: 12/25/2022]
Abstract
Physiological states of mitochondria often correlate with distinctive morphology. Electron microscopy and tomographic reconstruction were used to investigate the three-dimensional structure of axonal mitochondria and mitochondria in the surrounding Schwann cells of the peripheral nervous system (PNS), both in the vicinity of nodes of Ranvier and far from these nodes. Condensed mitochondria were found to be abundant in the axoplasm, but not in the Schwann cell. Uncharacteristic of the classical morphology of condensed mitochondria, the outer and inner boundary membranes are in close apposition and the crista junctions are narrow, consistent with their function as gates for the diffusion of macromolecules. There is also less cristae surface area and lower density of crista junctions in these mitochondria. The density of mitochondria was greater at the paranode-node-paranode (PNP) as was the crista junction opening, yet there were fewer cristae in these organelles compared to those in the internodal region. The greater density of condensed mitochondria in the PNS axoplasm and in particular at the PNP suggests a need for these organelles to operate at a high workload of ATP production.
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Affiliation(s)
- Guy A Perkins
- National Center for Microscopy and Imaging Research, Center for Research in Biological Systems, University of California, San Diego, La Jolla, CA 92093-0608, United States.
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85
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Activity-dependent regulation of mitochondrial motility by calcium and Na/K-ATPase at nodes of Ranvier of myelinated nerves. J Neurosci 2010; 30:3555-66. [PMID: 20219989 DOI: 10.1523/jneurosci.4551-09.2010] [Citation(s) in RCA: 87] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The node of Ranvier is a tiny segment of a myelinated fiber with various types of specializations adapted for generation of high-speed nerve impulses. It is ionically specialized with respect to ion channel segregation and ionic fluxes, and metabolically specialized in ionic pump expression and mitochondrial density augmentation. This report examines the interplay of three important parameters (calcium fluxes, Na pumps, mitochondrial motility) at nodes of Ranvier in frog during normal nerve activity. First, we used calcium dyes to resolve a highly localized elevation in axonal calcium at a node of Ranvier during action potentials, and showed that this calcium elevation retards mitochondrial motility during nerve impulses. Second, we found, surprisingly, that physiologic activation of the Na pumps retards mitochondrial motility. Blocking Na pumps alone greatly prevents action potentials from retarding mitochondrial motility, which reveals that mitochondrial motility is coupled to Na/K-ATPase. In conclusion, we suggest that during normal nerve activity, Ca elevation and activation of Na/K-ATPase act, possibly in a synergistic manner, to recruit mitochondria to a node of Ranvier to match metabolic needs.
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86
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Misko A, Jiang S, Wegorzewska I, Milbrandt J, Baloh RH. Mitofusin 2 is necessary for transport of axonal mitochondria and interacts with the Miro/Milton complex. J Neurosci 2010; 30:4232-40. [PMID: 20335458 PMCID: PMC2852190 DOI: 10.1523/jneurosci.6248-09.2010] [Citation(s) in RCA: 455] [Impact Index Per Article: 32.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2009] [Accepted: 02/03/2010] [Indexed: 12/25/2022] Open
Abstract
Mitofusins (Mfn1 and Mfn2) are outer mitochondrial membrane proteins involved in regulating mitochondrial dynamics. Mutations in Mfn2 cause Charcot-Marie-Tooth disease (CMT) type 2A, an inherited disease characterized by degeneration of long peripheral axons, but the nature of this tissue selectivity remains unknown. Here, we present evidence that Mfn2 is directly involved in and required for axonal mitochondrial transport, distinct from its role in mitochondrial fusion. Live imaging of neurons cultured from Mfn2 knock-out mice or neurons expressing Mfn2 disease mutants shows that axonal mitochondria spend more time paused and undergo slower anterograde and retrograde movements, indicating an alteration in attachment to microtubule-based transport systems. Furthermore, Mfn2 disruption altered mitochondrial movement selectively, leaving transport of other organelles intact. Importantly, both Mfn1 and Mfn2 interact with mammalian Miro (Miro1/Miro2) and Milton (OIP106/GRIF1) proteins, members of the molecular complex that links mitochondria to kinesin motors. Knockdown of Miro2 in cultured neurons produced transport deficits identical to loss of Mfn2, indicating that both proteins must be present at the outer membrane to mediate axonal mitochondrial transport. In contrast, disruption of mitochondrial fusion via knockdown of the inner mitochondrial membrane protein Opa1 had no effect on mitochondrial motility, indicating that loss of fusion does not inherently alter mitochondrial transport. These experiments identify a role for mitofusins in directly regulating mitochondrial transport and offer important insight into the cell type specificity and molecular mechanisms of axonal degeneration in CMT2A and dominant optic atrophy.
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Affiliation(s)
| | | | | | - Jeffrey Milbrandt
- Department of Neurology and
- Hope Center for Neurological Diseases, Washington University School of Medicine, St. Louis, Missouri 63110
| | - Robert H. Baloh
- Department of Neurology and
- Hope Center for Neurological Diseases, Washington University School of Medicine, St. Louis, Missouri 63110
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87
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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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88
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Figueroa-Romero C, Iñiguez-Lluhí JA, Stadler J, Chang CR, Arnoult D, Keller PJ, Hong Y, Blackstone C, Feldman EL. SUMOylation of the mitochondrial fission protein Drp1 occurs at multiple nonconsensus sites within the B domain and is linked to its activity cycle. FASEB J 2009; 23:3917-27. [PMID: 19638400 PMCID: PMC2775011 DOI: 10.1096/fj.09-136630] [Citation(s) in RCA: 150] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2009] [Accepted: 07/09/2009] [Indexed: 12/31/2022]
Abstract
Dynamin-related protein (Drp) 1 is a key regulator of mitochondrial fission and is composed of GTP-binding, Middle, insert B, and C-terminal GTPase effector (GED) domains. Drp1 associates with mitochondrial fission sites and promotes membrane constriction through its intrinsic GTPase activity. The mechanisms that regulate Drp1 activity remain poorly understood but are likely to involve reversible post-translational modifications, such as conjugation of small ubiquitin-like modifier (SUMO) proteins. Through a detailed analysis, we find that Drp1 interacts with the SUMO-conjugating enzyme Ubc9 via multiple regions and demonstrate that Drp1 is a direct target of SUMO modification by all three SUMO isoforms. While Drp1 does not harbor consensus SUMOylation sequences, our analysis identified2 clusters of lysine residues within the B domain that serve as noncanonical conjugation sites. Although initial analysis indicates that mitochondrial recruitment of ectopically expressed Drp1 in response to staurosporine is unaffected by loss of SUMOylation, we find that Drp1 SUMOylation is enhanced in the context of the K38A mutation. This dominant-negative mutant, which is deficient in GTP binding and hydrolysis, does not associate with mitochondria and prevents normal mitochondrial fission. This finding suggests that SUMOylation of Drp1 is linked to its activity cycle and is influenced by Drp1 localization.
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Affiliation(s)
- Claudia Figueroa-Romero
- University of Michigan, Department of Neurology 5017 BSRB, 109 Zina Pitcher Pl., Ann Arbor, MI 48109-2200, USA
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89
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Amiott EA, Cohen MM, Saint-Georges Y, Weissman AM, Shaw JM. A mutation associated with CMT2A neuropathy causes defects in Fzo1 GTP hydrolysis, ubiquitylation, and protein turnover. Mol Biol Cell 2009; 20:5026-35. [PMID: 19812251 DOI: 10.1091/mbc.e09-07-0622] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Charcot-Marie-Tooth disease type 2A (CMT2A) is caused by mutations in the gene MFN2 and is one of the most common inherited peripheral neuropathies. Mfn2 is one of two mammalian mitofusin GTPases that promote mitochondrial fusion and maintain organelle integrity. It is not known how mitofusin mutations cause axonal degeneration and CMT2A disease. We used the conserved yeast mitofusin FZO1 to study the molecular consequences of CMT2A mutations on Fzo1 function in vivo and in vitro. One mutation (analogous to the CMT2A I213T substitution in the GTPase domain of Mfn2) not only abolishes GTP hydrolysis and mitochondrial membrane fusion but also reduces Mdm30-mediated ubiquitylation and degradation of the mutant protein. Importantly, complexes of wild type and the mutant Fzo1 protein are GTPase active and restore ubiquitylation and degradation of the latter. These studies identify diverse and unexpected effects of CMT2A mutations, including a possible role for mitofusin ubiquitylation and degradation in CMT2A pathogenesis, and provide evidence for a novel link between Fzo1 GTP hydrolysis, ubiquitylation, and mitochondrial fusion.
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Affiliation(s)
- Elizabeth A Amiott
- Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, UT 84112, USA
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90
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GDAP1 mutations differ in their effects on mitochondrial dynamics and apoptosis depending on the mode of inheritance. Neurobiol Dis 2009; 36:509-20. [PMID: 19782751 DOI: 10.1016/j.nbd.2009.09.011] [Citation(s) in RCA: 107] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2009] [Revised: 09/10/2009] [Accepted: 09/20/2009] [Indexed: 12/12/2022] Open
Abstract
Mutations in the GDAP1 gene lead to recessively or dominantly inherited peripheral neuropathies (Charcot-Marie-Tooth disease; CMT). Here, we demonstrate that GDAP1 is a mitochondrial fission factor whose activity is dependent on the fission factors Drp1 and Fis1. Unlike other mitochondrial fission factors, GDAP1 overexpression or knockdown does not influence the susceptibility of cells to apoptotic stimuli. Recessively inherited CMT-associated forms of GDAP1 (rmGDAP1s) have reduced fission activity, whereas dominantly inherited forms (dmGDAP1s) interfere with mitochondrial fusion. Only the expression of dmGDAP1s increases the production of ROS, leads to uneven mitochondrial transmembrane potentials, and enhances the susceptibility to apoptotic stimuli. Taken together, our results indicate that wild-type GDAP1 promotes fission without increasing the risk of apoptosis. In CMT, recessive GDAP1 mutations are associated with reduced fission activity, while dominant mutations impair mitochondrial fusion and cause mitochondrial damage. Thus, different cellular mechanisms that disturb mitochondrial dynamics underlie the similar clinical manifestations caused by GDAP1 mutations, depending on the mode of inheritance.
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91
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Rhee HS, Steel CM, Derksen FJ, Robinson NE, Hoh JFY. Immunohistochemical analysis of laryngeal muscles in normal horses and horses with subclinical recurrent laryngeal neuropathy. J Histochem Cytochem 2009; 57:787-800. [PMID: 19398607 PMCID: PMC2713078 DOI: 10.1369/jhc.2009.953844] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2009] [Accepted: 04/16/2009] [Indexed: 11/22/2022] Open
Abstract
We used immunohistochemistry to examine myosin heavy-chain (MyHC)-based fiber-type profiles of the right and left cricoarytenoideus dorsalis (CAD) and arytenoideus transversus (TrA) muscles of six horses without laryngoscopic evidence of recurrent laryngeal neuropathy (RLN). Results showed that CAD and TrA muscles have the same slow, 2a, and 2x fibers as equine limb muscles, but not the faster contracting fibers expressing extraocular and 2B MyHCs found in laryngeal muscles of small mammals. Muscles from three horses showed fiber-type grouping bilaterally in the TrA muscles, but only in the left CAD. Fiber-type grouping suggests that denervation and reinnervation of fibers had occurred, and that these horses had subclinical RLN. There was a virtual elimination of 2x fibers in these muscles, accompanied by a significant increase in the percentage of 2a and slow fibers, and hypertrophy of these fiber types. The results suggest that multiple pathophysiological mechanisms are at work in early RLN, including selective denervation and reinnervation of 2x muscle fibers, corruption of neural impulse traffic that regulates 2x and slow muscle fiber types, and compensatory hypertrophy of remaining fibers. We conclude that horses afflicted with mild RLN are able to remain subclinical by compensatory hypertrophy of surviving muscle fibers.
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Affiliation(s)
- Hannah S Rhee
- Discipline of Physiology, Bosch Institute, School of Medical Sciences, Faculty of Medicine, The University of Sydney, Australia
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92
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Akude E, Zherebitskaya E, Roy Chowdhury SK, Girling K, Fernyhough P. 4-Hydroxy-2-nonenal induces mitochondrial dysfunction and aberrant axonal outgrowth in adult sensory neurons that mimics features of diabetic neuropathy. Neurotox Res 2009; 17:28-38. [PMID: 19557324 DOI: 10.1007/s12640-009-9074-5] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2009] [Revised: 04/03/2009] [Accepted: 04/26/2009] [Indexed: 01/17/2023]
Abstract
Modification of proteins by 4-hydroxy-2-nonenal (4-HNE) has been proposed to cause neurotoxicity in a number of neurodegenerative diseases, including distal axonopathy in diabetic sensory neuropathy. We tested the hypothesis that exposure of cultured adult rat sensory neurons to 4-HNE would result in the formation of amino acid adducts on mitochondrial proteins and that this process would be associated with impaired mitochondrial function and axonal regeneration. In addition, we compared 4-HNE-induced axon pathology with that exhibited by neurons isolated from diabetic rats. Cultured adult rat dorsal root ganglion (DRG) sensory neurons were incubated with varying concentrations of 4-HNE. Cell survival, axonal morphology, and level of axon outgrowth were assessed. In addition, video microscopy of live cells, western blot, and immunofluorescent staining were utilized to detect protein adduct formation by 4-HNE and to localize actively respiring mitochondria. 4-HNE induced formation of protein adducts on cytoskeletal and mitochondrial proteins, and impaired axon regeneration by approximately 50% at 3 microM while having no effect on neuronal survival. 4-HNE initiated formation of aberrant axonal structures and caused the accumulation of mitochondria in these dystrophic structures. Neurons treated with 4-HNE exhibited a distal loss of active mitochondria. Finally, the distal axonopathy and the associated aberrant axonal structures generated by 4-HNE treatment mimicked axon pathology observed in DRG sensory neurons isolated from diabetic rats and replicated aspects of neurodegeneration observed in human diabetic sensory neuropathy.
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Affiliation(s)
- Eli Akude
- Division of Neurodegenerative Disorders, St Boniface Hospital Research Centre, R4046-351 Tache Ave, Winnipeg, MB, R2H 2A6, Canada
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93
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Current World Literature. Curr Opin Lipidol 2009; 20:135-42. [PMID: 19276892 DOI: 10.1097/mol.0b013e32832a7e09] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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94
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Song JW, Yang LJ, Russell SM. Peripheral nerve: what's new in basic science laboratories. Neurosurg Clin N Am 2009; 20:121-31, viii. [PMID: 19064185 DOI: 10.1016/j.nec.2008.07.026] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
Peripheral nerve regeneration research has unfolded a wealth of basic science knowledge in the last century. Today, that knowledge has become the fundamental groundwork for evolving clinical applications to treat peripheral nerve defects. This article discusses two clinical applications that have been investigated thoroughly in the laboratory setting for decades and recently tested in the clinical setting: nerve allotransplantation to graft nerve defects, and brief electrical stimulation to promote nerve regeneration. It also discusses the generation of Thy-1-XFP transgenic mice, which express fluorescent proteins in the nervous system and provide new avenues for investigating peripheral nerve regeneration.
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Affiliation(s)
- Jae W Song
- Department of Neurosurgery, New York University School of Medicine, New York, NY 10016, USA
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95
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Weihofen A, Thomas KJ, Ostaszewski BL, Cookson MR, Selkoe DJ. Pink1 forms a multiprotein complex with Miro and Milton, linking Pink1 function to mitochondrial trafficking. Biochemistry 2009; 48:2045-52. [PMID: 19152501 PMCID: PMC2693257 DOI: 10.1021/bi8019178] [Citation(s) in RCA: 231] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Recessive mutations in Pink1 lead to a selective degeneration of dopaminergic neurons in the substantia nigra that is characteristic of Parkinson disease. Pink1 is a kinase that is targeted in part to mitochondria, and loss of Pink1 function can alter mitochondrial morphology and dynamics, thus supporting a link between mitochondrial dysfunction and Parkinson disease etiology. Here, we report the unbiased identification and confirmation of a mitochondrial multiprotein complex that contains Pink1, the atypical GTPase Miro, and the adaptor protein Milton. Our screen also identified an interaction between Pink1 and Mitofilin. Based on previously established functions for Miro and Milton in the trafficking of mitochondria along microtubules, we postulate here a role for Pink1 in mitochondrial trafficking. Using subcellular fractionation, we show that the overexpression of Miro and Milton, both of which are known to reside at the outer mitochondrial membrane, increases the mitochondrial Pink1 pool, suggesting a function of Pink1 at the outer membrane. Further, we document that Pink1 expressed without a mitochondrial targeting sequence can still be targeted to a mitochondria-enriched subcellular fraction via Miro and Milton. The latter finding is important for the interpretation of a previously reported protective effect of Pink1 expressed without a mitochondrial targeting sequence. Finally, we find that Miro and Milton expression suppresses altered mitochondrial morphology induced by loss of Pink1 function in cell culture. Our findings suggest that Pink1 functions in the trafficking of mitochondria in cells.
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Affiliation(s)
- Andreas Weihofen
- Center for Neurologic Diseases, Brigham and Women's Hospital and Harvard Medical School, Boston, MA 02115 USA
| | - Kelly Jean Thomas
- Laboratory of Neurogenetics, National Institute on Aging, NIH, Bethesda, MD 20893, USA
| | - Beth L. Ostaszewski
- Center for Neurologic Diseases, Brigham and Women's Hospital and Harvard Medical School, Boston, MA 02115 USA
| | - Mark R. Cookson
- Laboratory of Neurogenetics, National Institute on Aging, NIH, Bethesda, MD 20893, USA
| | - Dennis J. Selkoe
- Center for Neurologic Diseases, Brigham and Women's Hospital and Harvard Medical School, Boston, MA 02115 USA
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96
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Schmidt RE, Green KG, Snipes LL, Feng D. Neuritic dystrophy and neuronopathy in Akita (Ins2(Akita)) diabetic mouse sympathetic ganglia. Exp Neurol 2009; 216:207-18. [PMID: 19111542 PMCID: PMC2672346 DOI: 10.1016/j.expneurol.2008.11.019] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2008] [Revised: 11/24/2008] [Accepted: 11/30/2008] [Indexed: 12/14/2022]
Abstract
Diabetic autonomic neuropathy is a debilitating, poorly studied complication of diabetes. Our previous studies of non-obese diabetic (NOD) and related mouse models identified rapidly developing, dramatic pathology in prevertebral sympathetic ganglia; however, once diabetic, the mice did not survive for extended periods needed to examine the ability of therapeutic agents to correct established neuropathy. In the current manuscript we show that the Akita (Ins2(Akita)) mouse is a robust model of diabetic sympathetic autonomic neuropathy with unambiguous, spontaneous, rapidly-developing neuropathology which corresponds closely to the characteristic pathology of other rodent models and man. Akita mice diabetic for 2, 4 or 8 months of diabetes progressively developed markedly swollen axons and dendrites ("neuritic dystrophy") in the prevertebral superior mesenteric (SMG) and celiac ganglia (CG). Comparable changes failed to develop in the superior cervical ganglia (SCG) of the Akita mouse or in any ganglia of non-diabetic mice. Morphometric studies demonstrate an overall increase in presynaptic axon terminal cross sectional area, including those without any ultrastructural features of dystrophy. Neurons in Akita mouse prevertebral sympathetic ganglia show an unusual perikaryal alteration characterized by the accumulation of membranous aggregates and minute mitochondria and loss of rough endoplasmic reticulum. These changes result in the loss of a third of neurons in the CG over the course of 8 months of diabetes. The extended survival of diabetic mice and robust pathologic findings provide a clinically relevant paradigm that will facilitate the analysis of novel therapeutic agents on the reversal of autonomic neuropathy.
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Affiliation(s)
- Robert E Schmidt
- Division of Neuropathology, Department of Pathology and Immunology, Washington University School of Medicine, Saint Louis, MO 63110, USA.
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97
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The role of mitochondrial network dynamics in the pathogenesis of Charcot-Marie-Tooth disease. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2009; 652:129-37. [PMID: 20225023 DOI: 10.1007/978-90-481-2813-6_9] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Mitochondrial dysfunction plays a relevant role in the pathogenesis of neurological and neuromuscular diseases. Mitochondria may be involved as a primary defect of either the mtDNA or nuclear genome encoded subunits of the respiratory chain. These organelles have also been directly involved in the pathogenesis of Mendelian neurodegenerative disorders caused by mutations in nuclear-encoded proteins targeted to mitochondria, such as Friedreich ataxia, hereditary spastic paraplegia, or some monogenic forms of Parkinson disease. In addition, mitochondria also participate in the pathogenic mechanisms affecting neurodegenerative disorders such Huntington disease or amyotrophic lateral sclerosis. Cell death in neurodegeneration associated with neurological diseases usually occurs by apoptosis being the most common route the intrinsic mitochondria pathway. Along with regulation of apoptosis, mitochondria also modulate cell pathogenesis by means of energy production, reactive oxygen species (ROS) generation, and calcium buffering. Mitochondria form dynamic tubular networks that continually change their shape and move throughout the cell. Here we review the critical role of mitochondria in monogenic neuromuscular disorders, especially inherited peripheral neuropathies caused by abnormal mitochondrial network dynamics. In yeast, at least three proteins are required for mitochondrial fusion, Fzo1, Ugo1 and Mgm1. The human counterparts of Fzo1p and Mgm1p, MFN1/MFN2 and OPA1 respectively, are related to human disease. Mutations in the MFN2 gene cause the most frequent form of autosomal dominant axonal Charcot-Marie-Tooth disease, CMT2A. Mutations in OPA1 cause autosomal dominant optic atrophy (ADOA). For the opposite process of mitochondrial fission, four proteins are at least involved in yeast. Very recently a mutation in the DRP1 gene (the human homologue of yeast Dnm1) has been reported in an infant with a syndrome with encephalopathy, optic atrophy and lactic acidosis. GDAP1 has been recently related to the mitochondrial fission in mammalian cells and, interestingly, mutations in the GDAP1 gene are the cause of the most common form of autosomal recessive CMT, either axonal or demyelinating. These and other disorders are the most recent instances of disease related with mitochondrial abnormal motility, fusion and fission. We propose that the pathomechanisms underlying these disorders also include a complex relationship between mitochondrial dynamics and transport across the axon.
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98
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Schmidt RE, Parvin CA, Green KG. Synaptic ultrastructural alterations anticipate the development of neuroaxonal dystrophy in sympathetic ganglia of aged and diabetic mice. J Neuropathol Exp Neurol 2008; 67:1166-86. [PMID: 19018240 PMCID: PMC2665250 DOI: 10.1097/nen.0b013e318190d6db] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Neuroaxonal dystrophy, a distinctive axonopathy characterized by marked enlargement of distal axons, is the hallmark pathologic alteration in aged and diabetic human prevertebral sympathetic ganglia and in corresponding rodent models. Neuroaxonal dystrophy is thought to represent the abnormal outcome of cycles of synaptic degeneration and regeneration; a systematic study of identified axon terminals in aged and diabetic prevertebral ganglia, however, has not previously been performed. We examined the initial changes that develop in presynaptic and postsynaptic elements in sympathetic ganglia of aged and diabetic mice and found numerous synaptic changes involving both presynaptic and postsynaptic elements. Early alterations in presynaptic axon terminal size, vesicle content, and morphology culminate in the development of anastomosing membranous tubulovesicular aggregates, accumulation of autophagosomes, and amorphous debris that form a continuum with progressively larger classically dystrophic swellings. Dendritic changes consist of the development of swellings composed of delicate tubulovesicular elements and mitochondriopathy characterized by increased numbers of small mitochondria and, exclusively in aged ganglia, megamitochondria. These results support the hypothesis that neuroaxonal dystrophy results from progressive changes in presynaptic axon terminals that likely involve membrane dynamics and which are accompanied by distinctive changes in postsynaptic dendritic elements.
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Affiliation(s)
- Robert E Schmidt
- Division of Neuropathology, Department of Pathology and Immunology, Washington University School of Medicine, St Louis, Missouri 63110, USA.
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99
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Voccoli V, Colombaioni L. Mitochondrial remodeling in differentiating neuroblasts. Brain Res 2008; 1252:15-29. [PMID: 19071097 DOI: 10.1016/j.brainres.2008.11.026] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2008] [Revised: 10/17/2008] [Accepted: 11/01/2008] [Indexed: 01/06/2023]
Abstract
Mitochondria are able to change their shape through fission and fusion events, leading to a continuous remodeling of the mitochondrial network. Whereas the mitochondrial fission has been extensively studied and primarily related to the onset and progression of apoptosis, the physiological function of the opposite process of fusion is far less understood. With this study we analyzed the process of mitochondrial fusion in immortalized hippocampal neuroblasts searching for a relationship with specific changes in cellular physiology. The mitochondrial dynamics was examined in every stage of the cell cycle and a link was found between the enhancement of the mitochondrial transmembrane potential DeltaPsi(m), the widespread mitochondrial fusion and the process of neurite outgrowth. An identical mitochondrial reorganization also appeared in response to the pro-differentiating agent retinoic acid. The single-cell analysis in time-lapse of the mitochondrial response to RA evidenced a free calcium raise in the mitochondrial matrix coupled with the DeltaPsi(m) increase and it confirmed the close coordination between these two events and the fusion of mitochondria. The modulation of oxidative phosphorylation by carbonyl cyanide m-chlorophenyl hydrazone (CCCP) or pyruvate, underscored the importance of DeltaPsi(m) changes both in shaping the mitochondrial network and in regulating the rate of neurite outgrowth. We also report that the mitochondrial fusion observed during neurite outgrowth is not a consequence of the microtubule reorganization, since pharmacological treatments capable of blocking the microtubule dynamics failed to inhibit the mitochondrial remodeling in response to RA.
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Affiliation(s)
- Vladimir Voccoli
- Istituto di Neuroscienze CNR, Via G. Moruzzi 1, 56100 Pisa, Italy
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100
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Dina OA, Khasar SG, Alessandri-Haber N, Bogen O, Chen X, Green PG, Reichling DB, Messing RO, Levine JD. Neurotoxic catecholamine metabolite in nociceptors contributes to painful peripheral neuropathy. Eur J Neurosci 2008; 28:1180-90. [PMID: 18783367 DOI: 10.1111/j.1460-9568.2008.06425.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The neurotoxic effects of catecholamine metabolites have been implicated in neurodegenerative diseases. As some sensory neurons express tyrosine hydroxylase and monoamine oxidase (MAO), we investigated the potential contribution of catecholamine metabolites to neuropathic pain in a model of alcoholic neuropathy. The presence of catecholamines in sensory neurons is supported by capsaicin-stimulated epinephrine release, an effect enhanced in ethanol-fed rats. mRNA for enzymes in dorsal root ganglia involved in catecholamine uptake and metabolism, dopamine beta-hydroxylase and MAO-A, were decreased by neonatal administration of capsaicin. Ethanol-induced hyperalgesia was attenuated by systemic and local peripheral administration of inhibitors of MAO-A, reduction of norepinephrine transporter (NET) in sensory neurons and a NET inhibitor. Finally, intradermal injection of 3,4-dihydroxyphenylglycolaldehyde (DOPEGAL), a neurotoxic MAO-A catecholamine metabolite, produced robust mechanical hyperalgesia. These observations suggest that catecholamines in nociceptors are metabolized to neurotoxic products by MAO-A, which can cause neuronal dysfunction underlying neuropathic pain.
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Affiliation(s)
- Olayinka A Dina
- Department of Oral & Maxillofacial Surgery, University of California at San Francisco, CA, USA
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