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Kumar A, Larrea D, Pero ME, Infante P, Conenna M, Shin GJ, Van Elias V, Grueber WB, Di Marcotullio L, Area-Gomez E, Bartolini F. MFN2 coordinates mitochondria motility with α-tubulin acetylation and this regulation is disrupted in CMT2A. iScience 2024; 27:109994. [PMID: 38883841 PMCID: PMC11177149 DOI: 10.1016/j.isci.2024.109994] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2023] [Revised: 11/13/2023] [Accepted: 05/13/2024] [Indexed: 06/18/2024] Open
Abstract
Mitofusin-2 (MFN2), a large GTPase residing in the mitochondrial outer membrane and mutated in Charcot-Marie-Tooth type 2 disease (CMT2A), is a regulator of mitochondrial fusion and tethering with the ER. The role of MFN2 in mitochondrial transport has however remained elusive. Like MFN2, acetylated microtubules play key roles in mitochondria dynamics. Nevertheless, it is unknown if the α-tubulin acetylation cycle functionally interacts with MFN2. Here, we show that mitochondrial contacts with microtubules are sites of α-tubulin acetylation, which occurs through MFN2-mediated recruitment of α-tubulin acetyltransferase 1 (ATAT1). This activity is critical for MFN2-dependent regulation of mitochondria transport, and axonal degeneration caused by CMT2A MFN2 associated R94W and T105M mutations may depend on the inability to release ATAT1 at sites of mitochondrial contacts with microtubules. Our findings reveal a function for mitochondria in α-tubulin acetylation and suggest that disruption of this activity plays a role in the onset of MFN2-dependent CMT2A.
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Affiliation(s)
- Atul Kumar
- Department of Pathology & Cell Biology, Columbia University Irving Medical Center, New York, NY 10032, USA
| | - Delfina Larrea
- Department of Neurology, Columbia University Irving Medical Center, New York, NY 10032, USA
| | - Maria Elena Pero
- Department of Pathology & Cell Biology, Columbia University Irving Medical Center, New York, NY 10032, USA
- Department of Veterinary Medicine and Animal Production, University of Naples Federico II, 80137 Naples, Italy
| | - Paola Infante
- Department of Molecular Medicine, University of Rome “La Sapienza”, 00161 Rome, Italy
| | - Marilisa Conenna
- Department of Pathology & Cell Biology, Columbia University Irving Medical Center, New York, NY 10032, USA
- Department of Molecular Medicine, University of Rome “La Sapienza”, 00161 Rome, Italy
| | - Grace J. Shin
- Department of Neuroscience, Zuckerman Mind Brain Behavior Institute, Columbia University, New York, NY 10027, USA
| | - Vincent Van Elias
- Department of Pathology & Cell Biology, Columbia University Irving Medical Center, New York, NY 10032, USA
| | - Wesley B. Grueber
- Department of Neuroscience, Zuckerman Mind Brain Behavior Institute, Columbia University, New York, NY 10027, USA
- Department of Physiology & Cellular Biophysics, Zuckerman Mind Brain Behavior Institute, Columbia University, New York, NY 10032, USA
| | - Lucia Di Marcotullio
- Department of Molecular Medicine, University of Rome “La Sapienza”, 00161 Rome, Italy
- Istituto Pasteur-Fondazione Cenci Bolognetti, University of Rome La Sapienza, Rome, Italy
| | - Estela Area-Gomez
- Department of Neurology, Columbia University Irving Medical Center, New York, NY 10032, USA
| | - Francesca Bartolini
- Department of Pathology & Cell Biology, Columbia University Irving Medical Center, New York, NY 10032, USA
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2
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Abati E, Rizzuti M, Anastasia A, Comi GP, Corti S, Rizzo F. Charcot-Marie-Tooth type 2A in vivo models: Current updates. J Cell Mol Med 2024; 28:e18293. [PMID: 38722298 PMCID: PMC11081012 DOI: 10.1111/jcmm.18293] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2024] [Revised: 03/13/2024] [Accepted: 03/25/2024] [Indexed: 05/12/2024] Open
Abstract
Charcot-Marie-Tooth type 2A (CMT2A) is an inherited sensorimotor neuropathy associated with mutations within the Mitofusin 2 (MFN2) gene. These mutations impair normal mitochondrial functioning via different mechanisms, disturbing the equilibrium between mitochondrial fusion and fission, of mitophagy and mitochondrial axonal transport. Although CMT2A disease causes a significant disability, no resolutive treatment for CMT2A patients to date. In this context, reliable experimental models are essential to precisely dissect the molecular mechanisms of disease and to devise effective therapeutic strategies. The most commonly used models are either in vitro or in vivo, and among the latter murine models are by far the most versatile and popular. Here, we critically revised the most relevant literature focused on the experimental models, providing an update on the mammalian models of CMT2A developed to date. We highlighted the different phenotypic, histopathological and molecular characteristics, and their use in translational studies for bringing potential therapies from the bench to the bedside. In addition, we discussed limitations of these models and perspectives for future improvement.
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Affiliation(s)
- Elena Abati
- Neurology Unit, Foundation IRCCS Ca' Granda Ospedale Maggiore PoliclinicoMilanItaly
- Department of Pathophysiology and Transplantation, Dino Ferrari CenterUniversità degli Studi di MilanoMilanItaly
| | - Mafalda Rizzuti
- Neurology Unit, Foundation IRCCS Ca' Granda Ospedale Maggiore PoliclinicoMilanItaly
| | - Alessia Anastasia
- Neurology Unit, Foundation IRCCS Ca' Granda Ospedale Maggiore PoliclinicoMilanItaly
| | - Giacomo Pietro Comi
- Neurology Unit, Foundation IRCCS Ca' Granda Ospedale Maggiore PoliclinicoMilanItaly
- Department of Pathophysiology and Transplantation, Dino Ferrari CenterUniversità degli Studi di MilanoMilanItaly
| | - Stefania Corti
- Department of Pathophysiology and Transplantation, Dino Ferrari CenterUniversità degli Studi di MilanoMilanItaly
- Neuromuscular and Rare Diseases Unit, Department of NeuroscienceFondazione IRCCS Ca' Granda Ospedale Maggiore PoliclinicoMilanItaly
| | - Federica Rizzo
- Neurology Unit, Foundation IRCCS Ca' Granda Ospedale Maggiore PoliclinicoMilanItaly
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3
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Alberti C, Rizzo F, Anastasia A, Comi G, Corti S, Abati E. Charcot-Marie-tooth disease type 2A: An update on pathogenesis and therapeutic perspectives. Neurobiol Dis 2024; 193:106467. [PMID: 38452947 DOI: 10.1016/j.nbd.2024.106467] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2024] [Revised: 03/04/2024] [Accepted: 03/04/2024] [Indexed: 03/09/2024] Open
Abstract
Mutations in the gene encoding MFN2 have been identified as associated with Charcot-Marie-Tooth disease type 2A (CMT2A), a neurological disorder characterized by a broad clinical phenotype involving the entire nervous system. MFN2, a dynamin-like GTPase protein located on the outer mitochondrial membrane, is well-known for its involvement in mitochondrial fusion. Numerous studies have demonstrated its participation in a network crucial for various other mitochondrial functions, including mitophagy, axonal transport, and its controversial role in endoplasmic reticulum (ER)-mitochondria contacts. Considerable progress has been made in the last three decades in elucidating the disease pathogenesis, aided by the generation of animal and cellular models that have been instrumental in studying disease physiology. A review of the literature reveals that, up to now, no definitive pharmacological treatment for any CMT2A variant has been established; nonetheless, recent years have witnessed substantial progress. Many treatment approaches, especially concerning molecular therapy, such as histone deacetylase inhibitors, peptide therapy to increase mitochondrial fusion, the new therapeutic strategies based on MF1/MF2 balance, and SARM1 inhibitors, are currently in preclinical testing. The literature on gene silencing and gene replacement therapies is still limited, except for a recent study by Rizzo et al.(Rizzo et al., 2023), which recently first achieved encouraging results in in vitro and in vivo models of the disease. The near-future goal for these promising therapies is to progress to the stage of clinical translation.
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Affiliation(s)
- Claudia Alberti
- Department of Pathophysiology and Transplantation (DEPT), University of Milan, Milan, Italy
| | - Federica Rizzo
- Neurology Unit, Foundation IRCCS Ca' Granda Ospedale Maggiore Policlinico, Milan, Italy
| | - Alessia Anastasia
- Neurology Unit, Foundation IRCCS Ca' Granda Ospedale Maggiore Policlinico, Milan, Italy
| | - Giacomo Comi
- Department of Pathophysiology and Transplantation (DEPT), University of Milan, Milan, Italy; Neurology Unit, Foundation IRCCS Ca' Granda Ospedale Maggiore Policlinico, Milan, Italy
| | - Stefania Corti
- Department of Pathophysiology and Transplantation (DEPT), University of Milan, Milan, Italy; Neuromuscular and Rare Diseases Unit, Foundation IRCCS Ca' Granda Ospedale Maggiore Policlinico, Milan, Italy
| | - Elena Abati
- Department of Pathophysiology and Transplantation (DEPT), University of Milan, Milan, Italy; Neurology Unit, Foundation IRCCS Ca' Granda Ospedale Maggiore Policlinico, Milan, Italy.
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Ladero M, Reche-Sainz JA, Gallardo ME. Hereditary Optic Neuropathies: A Systematic Review on the Interplay between Biomaterials and Induced Pluripotent Stem Cells. Bioengineering (Basel) 2024; 11:52. [PMID: 38247929 PMCID: PMC10813088 DOI: 10.3390/bioengineering11010052] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2023] [Revised: 12/29/2023] [Accepted: 12/30/2023] [Indexed: 01/23/2024] Open
Abstract
Hereditary optic neuropathies (HONs) such as dominant optic atrophy (DOA) and Leber Hereditary Optic Neuropathy (LHON) are mitochondrial diseases characterized by a degenerative loss of retinal ganglion cells (RGCs) and are a cause of blindness worldwide. To date, there are only limited disease-modifying treatments for these disorders. The discovery of induced pluripotent stem cell (iPSC) technology has opened several promising opportunities in the field of HON research and the search for therapeutic approaches. This systematic review is focused on the two most frequent HONs (LHON and DOA) and on the recent studies related to the application of human iPSC technology in combination with biomaterials technology for their potential use in the development of RGC replacement therapies with the final aim of the improvement or even the restoration of the vision of HON patients. To this purpose, the combination of natural and synthetic biomaterials modified with peptides, neurotrophic factors, and other low- to medium-molecular weight compounds, mimicking the ocular extracellular matrices, with human iPSC or iPSC-derived cell retinal progenitors holds enormous potential to be exploited in the near future for the generation of transplantable RGC populations.
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Affiliation(s)
- Miguel Ladero
- FQPIMA Group, Materials and Chemical Engineering Department, Chemical Sciences School, Complutense University of Madrid, 28040 Madrid, Spain
| | - Jose Alberto Reche-Sainz
- Ophthalmology Unit, Hospital Universitario 12 de Octubre, 28041 Madrid, Spain
- Translational Research with iPS Cells Group, Research Institute of Hospital 12 de Octubre, imas12, 28041 Madrid, Spain
| | - M. Esther Gallardo
- Translational Research with iPS Cells Group, Research Institute of Hospital 12 de Octubre, imas12, 28041 Madrid, Spain
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Anton V, Buntenbroich I, Simões T, Joaquim M, Müller L, Buettner R, Odenthal M, Hoppe T, Escobar-Henriques M. E4 ubiquitin ligase promotes mitofusin turnover and mitochondrial stress response. Mol Cell 2023; 83:2976-2990.e9. [PMID: 37595558 PMCID: PMC10434984 DOI: 10.1016/j.molcel.2023.07.021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2022] [Revised: 05/31/2023] [Accepted: 07/18/2023] [Indexed: 08/20/2023]
Abstract
Ubiquitin-dependent control of mitochondrial dynamics is important for protein quality and neuronal integrity. Mitofusins, mitochondrial fusion factors, can integrate cellular stress through their ubiquitylation, which is carried out by multiple E3 enzymes in response to many different stimuli. However, the molecular mechanisms that enable coordinated responses are largely unknown. Here we show that yeast Ufd2, a conserved ubiquitin chain-elongating E4 enzyme, is required for mitochondrial shape adjustments. Under various stresses, Ufd2 translocates to mitochondria and triggers mitofusin ubiquitylation. This elongates ubiquitin chains on mitofusin and promotes its proteasomal degradation, leading to mitochondrial fragmentation. Ufd2 and its human homologue UBE4B also target mitofusin mutants associated with Charcot-Marie-Tooth disease, a hereditary sensory and motor neuropathy characterized by progressive loss of the peripheral nerves. This underscores the pathophysiological importance of E4-mediated ubiquitylation in neurodegeneration. In summary, we identify E4-dependent mitochondrial stress adaptation by linking various metabolic processes to mitochondrial fusion and fission dynamics.
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Affiliation(s)
- Vincent Anton
- Institute for Genetics, Cologne, Germany; Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), Cologne, Germany
| | - Ira Buntenbroich
- Institute for Genetics, Cologne, Germany; Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), Cologne, Germany
| | - Tânia Simões
- Institute for Genetics, Cologne, Germany; Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), Cologne, Germany
| | - Mariana Joaquim
- Institute for Genetics, Cologne, Germany; Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), Cologne, Germany; Center for Molecular Medicine Cologne (CMMC), Cologne, Germany
| | - Leonie Müller
- Institute for Genetics, Cologne, Germany; Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), Cologne, Germany
| | - Reinhard Buettner
- Center for Molecular Medicine Cologne (CMMC), Cologne, Germany; Institute of Pathology, Medical Faculty, University Hospital, University of Cologne, Germany
| | - Margarete Odenthal
- Center for Molecular Medicine Cologne (CMMC), Cologne, Germany; Institute of Pathology, Medical Faculty, University Hospital, University of Cologne, Germany
| | - Thorsten Hoppe
- Institute for Genetics, Cologne, Germany; Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), Cologne, Germany; Center for Molecular Medicine Cologne (CMMC), Cologne, Germany
| | - Mafalda Escobar-Henriques
- Institute for Genetics, Cologne, Germany; Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), Cologne, Germany; Center for Molecular Medicine Cologne (CMMC), Cologne, Germany.
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Buntenbroich I, Anton V, Perez-Hernandez D, Simões T, Gaedke F, Schauss A, Dittmar G, Riemer J, Escobar-Henriques M. Docking and stability defects in mitofusin highlight the proteasome as a potential therapeutic target. iScience 2023; 26:107014. [PMID: 37416455 PMCID: PMC10320088 DOI: 10.1016/j.isci.2023.107014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2022] [Revised: 04/23/2023] [Accepted: 05/29/2023] [Indexed: 07/08/2023] Open
Abstract
Defects in mitochondrial fusion are at the base of many diseases. Mitofusins power membrane-remodeling events via self-interaction and GTP hydrolysis. However, how exactly mitofusins mediate fusion of the outer membrane is still unclear. Structural studies enable tailored design of mitofusin variants, providing valuable tools to dissect this stepwise process. Here, we found that the two cysteines conserved between yeast and mammals are required for mitochondrial fusion, revealing two novel steps of the fusion cycle. C381 is dominantly required for the formation of the trans-tethering complex, before GTP hydrolysis. C805 allows stabilizing the Fzo1 protein and the trans-tethering complex, just prior to membrane fusion. Moreover, proteasomal inhibition rescued Fzo1 C805S levels and membrane fusion, suggesting a possible application for clinically approved drugs. Together, our study provides insights into how assembly or stability defects in mitofusins might cause mitofusin-associated diseases and uncovers potential therapeutic intervention by proteasomal inhibition.
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Affiliation(s)
- Ira Buntenbroich
- Institute for Genetics,University of Cologne, Cologne 50931, Germany
| | - Vincent Anton
- Institute for Genetics,University of Cologne, Cologne 50931, Germany
| | - Daniel Perez-Hernandez
- Proteomics of Cellular Signaling, Luxembourg Institute of Health, Strassen 1445, Luxembourg
| | - Tânia Simões
- Institute for Genetics,University of Cologne, Cologne 50931, Germany
| | - Felix Gaedke
- Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Cologne 50931, Germany
| | - Astrid Schauss
- Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Cologne 50931, Germany
| | - Gunnar Dittmar
- Proteomics of Cellular Signaling, Luxembourg Institute of Health, Strassen 1445, Luxembourg
| | - Jan Riemer
- Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Cologne 50931, Germany
- Institute for Biochemistry, University of Cologne, Cologne 50931, Germany
| | - Mafalda Escobar-Henriques
- Institute for Genetics,University of Cologne, Cologne 50931, Germany
- Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Cologne 50931, Germany
- Center for Molecular Medicine Cologne (CMMC), University of Cologne, Cologne 50931, Germany
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7
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Okamoto Y, Takashima H. The Current State of Charcot-Marie-Tooth Disease Treatment. Genes (Basel) 2023; 14:1391. [PMID: 37510296 PMCID: PMC10379063 DOI: 10.3390/genes14071391] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2023] [Revised: 06/20/2023] [Accepted: 06/29/2023] [Indexed: 07/30/2023] Open
Abstract
Charcot-Marie-Tooth disease (CMT) and associated neuropathies are the most predominant genetically transmitted neuromuscular conditions; however, effective pharmacological treatments have not established. The extensive genetic heterogeneity of CMT, which impacts the peripheral nerves and causes lifelong disability, presents a significant barrier to the development of comprehensive treatments. An estimated 100 loci within the human genome are linked to various forms of CMT and its related inherited neuropathies. This review delves into prospective therapeutic strategies used for the most frequently encountered CMT variants, namely CMT1A, CMT1B, CMTX1, and CMT2A. Compounds such as PXT3003, which are being clinically and preclinically investigated, and a broad array of therapeutic agents and their corresponding mechanisms are discussed. Furthermore, the progress in established gene therapy techniques, including gene replacement via viral vectors, exon skipping using antisense oligonucleotides, splicing modification, and gene knockdown, are appraised. Each of these gene therapies has the potential for substantial advancements in future research.
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Affiliation(s)
- Yuji Okamoto
- Department of Neurology and Geriatrics, Kagoshima University Graduate School of Medical and Dental Sciences, Kagoshima 890-8544, Japan
- Department of Physical Therapy, School of Health Sciences, Faculty of Medicine, Kagoshima University, Kagoshima 890-8544, Japan
| | - Hiroshi Takashima
- Department of Neurology and Geriatrics, Kagoshima University Graduate School of Medical and Dental Sciences, Kagoshima 890-8544, Japan
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Zacharioudakis E, Gavathiotis E. Mitochondrial dynamics proteins as emerging drug targets. Trends Pharmacol Sci 2023; 44:112-127. [PMID: 36496299 PMCID: PMC9868082 DOI: 10.1016/j.tips.2022.11.004] [Citation(s) in RCA: 26] [Impact Index Per Article: 26.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2022] [Revised: 11/15/2022] [Accepted: 11/16/2022] [Indexed: 12/12/2022]
Abstract
The importance of mitochondrial dynamics, the physiological process of mitochondrial fusion and fission, in regulating diverse cellular functions and cellular fitness has been well established. Several pathologies are associated with aberrant mitochondrial fusion or fission that is often a consequence of deregulated mitochondrial dynamics proteins; however, pharmacological targeting of these proteins has been lacking and is challenged by complex molecular mechanisms. Recent studies have advanced our understanding in this area and have enabled rational drug design and chemical screening strategies. We provide an updated overview of the regulatory mechanisms of fusion and fission proteins, their structure-function relationships, and the discovery of pharmacological modulators demonstrating their therapeutic potential. These advances provide exciting opportunities for the development of prototype therapeutics for various diseases.
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Affiliation(s)
- Emmanouil Zacharioudakis
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, NY, USA; Department of Medicine, Albert Einstein College of Medicine, Bronx, NY, USA; Albert Einstein Cancer Center, Albert Einstein College of Medicine, Bronx, NY, USA; Wilf Family Cardiovascular Research Institute, Albert Einstein College of Medicine, Bronx, NY, USA; Institute for Aging Research, Albert Einstein College of Medicine, Bronx, NY, USA
| | - Evripidis Gavathiotis
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, NY, USA; Department of Medicine, Albert Einstein College of Medicine, Bronx, NY, USA; Albert Einstein Cancer Center, Albert Einstein College of Medicine, Bronx, NY, USA; Wilf Family Cardiovascular Research Institute, Albert Einstein College of Medicine, Bronx, NY, USA; Institute for Aging Research, Albert Einstein College of Medicine, Bronx, NY, USA.
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Multiple respiratory complications in a patient with Charcot-Marie-Tooth disease with MFN2 mutation. Respir Med Case Rep 2022; 36:101601. [PMID: 35242516 PMCID: PMC8866735 DOI: 10.1016/j.rmcr.2022.101601] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2021] [Accepted: 02/15/2022] [Indexed: 11/23/2022] Open
Abstract
Charcot-Marie-Tooth disease (CMT) is a hereditary peripheral neuropathy characterized by progressive atrophy of distal muscles. Respiratory complications are rare. We present a case of a 49-year-old male with childhood-onset CMT bearing a genetic mutation of MFN2. He had difficulty breathing when he was 46. Imaging examination revealed complications of phrenic nerve paralysis and pneumothorax with a funnel chest. Respiratory function test demonstrated severe restrictive ventilatory impairment. Polysomnography supported the diagnosis of mild sleep apnea syndrome. Noninvasive positive pressure ventilation successfully reduced respiratory symptoms. To our knowledge, this is the first demonstration of multiple respiratory complications in a CMT patient. Respiratory complications in Charcot-Marie-Tooth disease (CMT) are rare. This is the first report of multiple respiratory complications in a CMT patient. Non-invasive ventilation was safely introduced and effective in this case.
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Zhang T, Li J, Zhao G. Quality Control Mechanisms of Mitochondria: Another Important Target for Treatment of Peripheral Neuropathy. DNA Cell Biol 2021; 40:1513-1527. [PMID: 34851723 DOI: 10.1089/dna.2021.0529] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Mitochondria provide energy for various cellular activities and are involved in the regulating of several physiological and pathological processes. Mitochondria constitute a dynamic network regulated by numerous quality control mechanisms; for example, division is necessary for mitochondria to develop, and fusion dilutes toxins produced by the mitochondria. Mitophagy removes damaged mitochondria. The etiologies of peripheral neuropathy include congenital and acquired diseases, and the pathogenesis varies; however, oxidative stress caused by mitochondrial damage is the accepted pathogenesis of peripheral neuropathy. Regulation and control of mitochondrial quality might point the way toward potential treatments for peripheral neuropathy. This article will review mitochondrial quality control mechanisms, their involvement in peripheral nerve diseases, and their potential therapeutic role.
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Affiliation(s)
- Te Zhang
- China-Japan Union Hospital of Jilin University, Changchun, P.R. China
| | - Jiannan Li
- China-Japan Union Hospital of Jilin University, Changchun, P.R. China
| | - Guoqing Zhao
- China-Japan Union Hospital of Jilin University, Changchun, P.R. China
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11
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Shen L, Zhang Q, Tu S, Qin W. SIRT3 mediates mitofusin 2 ubiquitination and degradation to suppress ischemia reperfusion-induced acute kidney injury. Exp Cell Res 2021; 408:112861. [PMID: 34624325 DOI: 10.1016/j.yexcr.2021.112861] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2021] [Revised: 09/30/2021] [Accepted: 10/04/2021] [Indexed: 01/22/2023]
Abstract
Ischemia reperfusion-induced acute kidney injury (IR-induced AKI) is a life-threatening disease with many complications. Mitofusin 2 (Mfn2) ubiquitination is related to AKI. But the underlying molecular mechanisms remain unknown. This study aimed to probe the mechanism of Mfn2 ubiquitination in IR-induced AKI development. In IR-induced AKI mouse models, orbital blood and urine were collected for assessing kidney function. The kidney injury, ultrastructure of mitochondria, and histopathology in mice were evaluated after injection of G5, an ubiquitination inhibitor. Oxygen glucose deprivation/reoxygenation (OGD/R) models were established in HK-2 cells, and the mitochondria were extracted. Cell viability, apoptosis, oxidative stress, inflammatory reaction, mitochondrial membrane potential, and ATP production were measured. Mfn2 ubiquitination in mouse and cell models was evaluated. si-SIRT3 and pcDNA3.1-SIRT3 were transfected into cell models. Consequently, kidney function in mice was impaired by IR-induced AKI. Mfn2 ubiquitination and degradation promoted IR-induced AKI. OGD/R induced renal tubular epithelial cell injury and disrupted mitochondrial dynamics and functions through promoting Mfn2 ubiquitination. SIRT3 knockdown led to Mfn2 ubiquitination by binding to UBC; while its overexpression alleviated tubular epithelial cell injury. Briefly, SIRT3 mediates Mfn2 ubiquitination to relieve IR-induced AKI. This investigation may offer new insights for the treatment of IR-induced AKI injury.
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Affiliation(s)
- Lin Shen
- Emergency Department, Shangqiu First People's Hospital, No.292 Kaixuan South Road, Suiyang District, Shangqiu, Henan Province, 476000, China
| | - Qiufeng Zhang
- Emergency Department, Shangqiu First People's Hospital, No.292 Kaixuan South Road, Suiyang District, Shangqiu, Henan Province, 476000, China.
| | - Shumin Tu
- Emergency Department, Shangqiu First People's Hospital, No.292 Kaixuan South Road, Suiyang District, Shangqiu, Henan Province, 476000, China
| | - Wentao Qin
- Emergency Department, Shangqiu First People's Hospital, No.292 Kaixuan South Road, Suiyang District, Shangqiu, Henan Province, 476000, China
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12
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Joaquim M, Escobar-Henriques M. Role of Mitofusins and Mitophagy in Life or Death Decisions. Front Cell Dev Biol 2020; 8:572182. [PMID: 33072754 PMCID: PMC7539839 DOI: 10.3389/fcell.2020.572182] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2020] [Accepted: 09/03/2020] [Indexed: 12/12/2022] Open
Abstract
Mitochondria entail an incredible dynamism in their morphology, impacting death signaling and selective elimination of the damaged organelles. In turn, by recycling the superfluous or malfunctioning mitochondria, mostly prevalent during aging, mitophagy contributes to maintain a healthy mitochondrial network. Mitofusins locate at the outer mitochondrial membrane and control the plastic behavior of mitochondria, by mediating fusion events. Besides deciding on mitochondrial interconnectivity, mitofusin 2 regulates physical contacts between mitochondria and the endoplasmic reticulum, but also serves as a decisive docking platform for mitophagy and apoptosis effectors. Thus, mitofusins integrate multiple bidirectional inputs from and into mitochondria and ensure proper energetic and metabolic cellular performance. Here, we review the role of mitofusins and mitophagy at the cross-road between life and apoptotic death decisions. Furthermore, we highlight the impact of this interplay on disease, focusing on how mitofusin 2 and mitophagy affect non-alcoholic fatty liver disease.
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Affiliation(s)
- Mariana Joaquim
- Institute for Genetics, Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), Center for Molecular Medicine Cologne (CMMC), University of Cologne, Cologne, Germany
| | - Mafalda Escobar-Henriques
- Institute for Genetics, Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), Center for Molecular Medicine Cologne (CMMC), University of Cologne, Cologne, Germany
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De Gioia R, Citterio G, Abati E, Nizzardo M, Bresolin N, Comi GP, Corti S, Rizzo F. Animal Models of CMT2A: State-of-art and Therapeutic Implications. Mol Neurobiol 2020; 57:5121-5129. [PMID: 32856204 PMCID: PMC7541381 DOI: 10.1007/s12035-020-02081-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2020] [Accepted: 08/19/2020] [Indexed: 01/19/2023]
Abstract
Charcot-Marie-Tooth disease type 2A (CMT2A), arising from mitofusin 2 (MFN2) gene mutations, is the most common inherited axonal neuropathy affecting motor and sensory neurons. The cellular and molecular mechanisms by which MFN2 mutations determine neuronal degeneration are largely unclear. No effective treatment exists for CMT2A, which has a high degree of genetic/phenotypic heterogeneity. The identification of mutations in MFN2 has allowed the generation of diverse transgenic animal models, but to date, their ability to recapitulate the CMT2A phenotype is limited, precluding elucidation of its pathogenesis and discovery of therapeutic strategies. This review will critically present recent progress in in vivo CMT2A disease modeling, discoveries, drawbacks and limitations, current challenges, and key reflections to advance the field towards developing effective therapies for these patients.
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Affiliation(s)
- Roberta De Gioia
- Neurology Unit, IRCCS Foundation Ca' Granda Ospedale Maggiore Policlinico, Via Francesco Sforza 35, 20122, Milan, Italy
| | - Gaia Citterio
- Dino Ferrari Centre, Neuroscience Section, Department of Pathophysiology and Transplantation (DEPT), University of Milan, Milan, Italy
| | - Elena Abati
- Dino Ferrari Centre, Neuroscience Section, Department of Pathophysiology and Transplantation (DEPT), University of Milan, Milan, Italy
| | - Monica Nizzardo
- Neurology Unit, IRCCS Foundation Ca' Granda Ospedale Maggiore Policlinico, Via Francesco Sforza 35, 20122, Milan, Italy.,Dino Ferrari Centre, Neuroscience Section, Department of Pathophysiology and Transplantation (DEPT), University of Milan, Milan, Italy
| | - Nereo Bresolin
- Neurology Unit, IRCCS Foundation Ca' Granda Ospedale Maggiore Policlinico, Via Francesco Sforza 35, 20122, Milan, Italy.,Dino Ferrari Centre, Neuroscience Section, Department of Pathophysiology and Transplantation (DEPT), University of Milan, Milan, Italy
| | - Giacomo Pietro Comi
- Neurology Unit, IRCCS Foundation Ca' Granda Ospedale Maggiore Policlinico, Via Francesco Sforza 35, 20122, Milan, Italy.,Dino Ferrari Centre, Neuroscience Section, Department of Pathophysiology and Transplantation (DEPT), University of Milan, Milan, Italy
| | - Stefania Corti
- Neurology Unit, IRCCS Foundation Ca' Granda Ospedale Maggiore Policlinico, Via Francesco Sforza 35, 20122, Milan, Italy.,Dino Ferrari Centre, Neuroscience Section, Department of Pathophysiology and Transplantation (DEPT), University of Milan, Milan, Italy
| | - Federica Rizzo
- Neurology Unit, IRCCS Foundation Ca' Granda Ospedale Maggiore Policlinico, Via Francesco Sforza 35, 20122, Milan, Italy. .,Dino Ferrari Centre, Neuroscience Section, Department of Pathophysiology and Transplantation (DEPT), University of Milan, Milan, Italy.
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14
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Abati E, Bresolin N, Comi G, Corti S. Silence superoxide dismutase 1 (SOD1): a promising therapeutic target for amyotrophic lateral sclerosis (ALS). Expert Opin Ther Targets 2020; 24:295-310. [PMID: 32125907 DOI: 10.1080/14728222.2020.1738390] [Citation(s) in RCA: 43] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Introduction: Amyotrophic lateral sclerosis (ALS) is a progressive and incurable neurodegenerative disorder that targets upper and lower motor neurons and leads to fatal muscle paralysis. Mutations in the superoxide dismutase 1 (SOD1) gene are responsible for 15% of familial ALS cases, but several studies have indicated that SOD1 dysfunction may also play a pathogenic role in sporadic ALS. SOD1 induces numerous toxic effects through the pathological misfolding and aggregation of mutant SOD1 species, hence a reduction of the levels of toxic variants appears to be a promising therapeutic strategy for SOD1-related ALS. Several methods are used to modulate gene expression in vivo; these include RNA interference, antisense oligonucleotides (ASOs) and CRISPR/Cas9 technology.Areas covered: This paper examines the current approaches for gene silencing and the progress made in silencing SOD1 in vivo. It progresses to shed light on the key results and pitfalls of these studies and highlights the future challenges and new perspectives for this exciting research field.Expert opinion: Gene silencing strategies targeting SOD1 may represent effective approaches for familial and sporadic ALS-related neurodegeneration; however, the risk of off-target effects must be minimized, and effective and minimally invasive delivery strategies should be fine-tuned.
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Affiliation(s)
- Elena Abati
- Department of Pathophysiology and Transplantation (DEPT), Dino Ferrari Centre, Neuroscience Section, University of Milan, Milan, Italy
| | - Nereo Bresolin
- Department of Pathophysiology and Transplantation (DEPT), Dino Ferrari Centre, Neuroscience Section, University of Milan, Milan, Italy.,Foundation IRCCS Ca' Granda Ospedale Maggiore Policlinico, Neurology Unit, Milan, Italy
| | - Giacomo Comi
- Department of Pathophysiology and Transplantation (DEPT), Dino Ferrari Centre, Neuroscience Section, University of Milan, Milan, Italy.,Foundation IRCCS Ca' Granda Ospedale Maggiore Policlinico, Neurology Unit, Milan, Italy
| | - Stefania Corti
- Department of Pathophysiology and Transplantation (DEPT), Dino Ferrari Centre, Neuroscience Section, University of Milan, Milan, Italy.,Foundation IRCCS Ca' Granda Ospedale Maggiore Policlinico, Neurology Unit, Milan, Italy
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15
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Schuster R, Anton V, Simões T, Altin S, den Brave F, Hermanns T, Hospenthal M, Komander D, Dittmar G, Dohmen RJ, Escobar-Henriques M. Dual role of a GTPase conformational switch for membrane fusion by mitofusin ubiquitylation. Life Sci Alliance 2020; 3:e201900476. [PMID: 31857350 PMCID: PMC6925385 DOI: 10.26508/lsa.201900476] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2019] [Revised: 12/11/2019] [Accepted: 12/11/2019] [Indexed: 12/13/2022] Open
Abstract
Mitochondria are essential organelles whose function is upheld by their dynamic nature. This plasticity is mediated by large dynamin-related GTPases, called mitofusins in the case of fusion between two mitochondrial outer membranes. Fusion requires ubiquitylation, attached to K398 in the yeast mitofusin Fzo1, occurring in atypical and conserved forms. Here, modelling located ubiquitylation to α4 of the GTPase domain, a critical helix in Ras-mediated events. Structure-driven analysis revealed a dual role of K398. First, it is required for GTP-dependent dynamic changes of α4. Indeed, mutations designed to restore the conformational switch, in the absence of K398, rescued wild-type-like ubiquitylation on Fzo1 and allowed fusion. Second, K398 is needed for Fzo1 recognition by the pro-fusion factors Cdc48 and Ubp2. Finally, the atypical ubiquitylation pattern is stringently required bilaterally on both involved mitochondria. In contrast, exchange of the conserved pattern with conventional ubiquitin chains was not sufficient for fusion. In sum, α4 lysines from both small and large GTPases could generally have an electrostatic function for membrane interaction, followed by posttranslational modifications, thus driving membrane fusion events.
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Affiliation(s)
- Ramona Schuster
- Institute for Genetics, Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), Center for Molecular Medicine Cologne, University of Cologne, Cologne, Germany
| | - Vincent Anton
- Institute for Genetics, Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), Center for Molecular Medicine Cologne, University of Cologne, Cologne, Germany
| | - Tânia Simões
- Institute for Genetics, Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), Center for Molecular Medicine Cologne, University of Cologne, Cologne, Germany
| | - Selver Altin
- Institute for Genetics, Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), Center for Molecular Medicine Cologne, University of Cologne, Cologne, Germany
| | - Fabian den Brave
- Department of Molecular Cell Biology, Max Planck Institute of Biochemistry, Martinsried, Germany
| | - Thomas Hermanns
- Institute for Genetics, University of Cologne, Cologne, Germany
| | - Manuela Hospenthal
- Institute of Molecular Biology and Biophysics, Eidgenössische Technische Hochschule Zürich, Zürich, Switzerland
| | - David Komander
- Medical Research Council Laboratory of Molecular Biology, Cambridge, UK
- Ubiquitin Signalling Division, The Walter and Eliza Hall Institute of Medical Research, Parkville, Australia
- Department of Medical Biology, The University of Melbourne, Melbourne, Australia
| | - Gunnar Dittmar
- Proteomics of Cellular Signalling, Luxembourg Institute of Health, Strassen, Luxembourg
| | - R Jürgen Dohmen
- Institute for Genetics, University of Cologne, Cologne, Germany
| | - Mafalda Escobar-Henriques
- Institute for Genetics, Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), Center for Molecular Medicine Cologne, University of Cologne, Cologne, Germany
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Anton V, Buntenbroich I, Schuster R, Babatz F, Simões T, Altin S, Calabrese G, Riemer J, Schauss A, Escobar-Henriques M. Plasticity in salt bridge allows fusion-competent ubiquitylation of mitofusins and Cdc48 recognition. Life Sci Alliance 2019; 2:e201900491. [PMID: 31740565 PMCID: PMC6861704 DOI: 10.26508/lsa.201900491] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2019] [Revised: 11/06/2019] [Accepted: 11/07/2019] [Indexed: 01/08/2023] Open
Abstract
Mitofusins are dynamin-related GTPases that drive mitochondrial fusion by sequential events of oligomerization and GTP hydrolysis, followed by their ubiquitylation. Here, we show that fusion requires a trilateral salt bridge at a hinge point of the yeast mitofusin Fzo1, alternatingly forming before and after GTP hydrolysis. Mutations causative of Charcot-Marie-Tooth disease massively map to this hinge point site, underlining the disease relevance of the trilateral salt bridge. A triple charge swap rescues the activity of Fzo1, emphasizing the close coordination of the hinge residues with GTP hydrolysis. Subsequently, ubiquitylation of Fzo1 allows the AAA-ATPase ubiquitin-chaperone Cdc48 to resolve Fzo1 clusters, releasing the dynamin for the next fusion round. Furthermore, cross-complementation within the oligomer unexpectedly revealed ubiquitylated but fusion-incompetent Fzo1 intermediates. However, Cdc48 did not affect the ubiquitylated but fusion-incompetent variants, indicating that Fzo1 ubiquitylation is only controlled after membrane merging. Together, we present an integrated model on how mitochondrial outer membranes fuse, a critical process for their respiratory function but also putatively relevant for therapeutic interventions.
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Affiliation(s)
- Vincent Anton
- Institute for Genetics, Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), Center for Molecular Medicine Cologne, University of Cologne, Cologne, Germany
| | - Ira Buntenbroich
- Institute for Genetics, Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), Center for Molecular Medicine Cologne, University of Cologne, Cologne, Germany
| | - Ramona Schuster
- Institute for Genetics, Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), Center for Molecular Medicine Cologne, University of Cologne, Cologne, Germany
| | | | - Tânia Simões
- Institute for Genetics, Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), Center for Molecular Medicine Cologne, University of Cologne, Cologne, Germany
| | - Selver Altin
- Institute for Genetics, Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), Center for Molecular Medicine Cologne, University of Cologne, Cologne, Germany
| | - Gaetano Calabrese
- Institute for Biochemistry, Department of Chemistry, University of Cologne, Cologne, Germany
| | - Jan Riemer
- Institute for Biochemistry, Department of Chemistry, University of Cologne, Cologne, Germany
| | | | - Mafalda Escobar-Henriques
- Institute for Genetics, Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), Center for Molecular Medicine Cologne, University of Cologne, Cologne, Germany
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17
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Moss KR, Höke A. Targeting the programmed axon degeneration pathway as a potential therapeutic for Charcot-Marie-Tooth disease. Brain Res 2019; 1727:146539. [PMID: 31689415 DOI: 10.1016/j.brainres.2019.146539] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2019] [Revised: 10/24/2019] [Accepted: 10/30/2019] [Indexed: 12/14/2022]
Abstract
The programmed axon degeneration pathway has emerged as an important process contributing to the pathogenesis of several neurological diseases. The most crucial events in this pathway include activation of the central executioner SARM1 and NAD+ depletion, which leads to an energetic failure and ultimately axon destruction. Given the prevalence of this pathway, it is not surprising that inhibitory therapies are currently being developed in order to treat multiple neurological diseases with the same therapy. Charcot-Marie-Tooth disease (CMT) is a heterogeneous group of neurological diseases that may also benefit from this therapeutic approach. To evaluate the appropriateness of this strategy, the contribution of the programmed axon degeneration pathway to the pathogenesis of different CMT subtypes is being actively investigated. The subtypes CMT1A, CMT1B and CMT2D are the first to have been examined. Based on the results from these studies and advances in developing therapies to block the programmed axon degeneration pathway, promising therapeutics for CMT are now on the horizon.
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Affiliation(s)
- Kathryn R Moss
- Department of Neurology, Neuromuscular Division, Johns Hopkins School of Medicine, Baltimore, MD, United States
| | - Ahmet Höke
- Department of Neurology, Neuromuscular Division, Johns Hopkins School of Medicine, Baltimore, MD, United States.
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18
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Charcot-Marie-Tooth: From Molecules to Therapy. Int J Mol Sci 2019; 20:ijms20143419. [PMID: 31336816 PMCID: PMC6679156 DOI: 10.3390/ijms20143419] [Citation(s) in RCA: 96] [Impact Index Per Article: 19.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2019] [Revised: 07/03/2019] [Accepted: 07/03/2019] [Indexed: 01/08/2023] Open
Abstract
Charcot-Marie-Tooth (CMT) is the most prevalent category of inherited neuropathy. The most common inheritance pattern is autosomal dominant, though there also are X-linked and autosomal recessive subtypes. In addition to a variety of inheritance patterns, there are a myriad of genes associated with CMT, reflecting the heterogeneity of this disorder. Next generation sequencing (NGS) has expanded and simplified the diagnostic yield of genes/molecules underlying and/or associated with CMT, which is of paramount importance in providing a substrate for current and future targeted disease-modifying treatment options. Considerable research attention for disease-modifying therapy has been geared towards the most commonly encountered genetic mutations (PMP22, GJB1, MPZ, and MFN2). In this review, we highlight the clinical background, molecular understanding, and therapeutic investigations of these CMT subtypes, while also discussing therapeutic research pertinent to the remaining less common CMT subtypes.
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19
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Mitochondrial dynamics and their potential as a therapeutic target. Mitochondrion 2019; 49:269-283. [PMID: 31228566 DOI: 10.1016/j.mito.2019.06.002] [Citation(s) in RCA: 112] [Impact Index Per Article: 22.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2019] [Revised: 05/02/2019] [Accepted: 06/06/2019] [Indexed: 12/16/2022]
Abstract
Mitochondrial dynamics shape the mitochondrial network and contribute to mitochondrial function and quality control. Mitochondrial fusion and division are integrated into diverse cellular functions and respond to changes in cell physiology. Imbalanced mitochondrial dynamics are associated with a range of diseases that are broadly characterized by impaired mitochondrial function and increased cell death. In various disease models, modulating mitochondrial fusion and division with either small molecules or genetic approaches has improved function. Although additional mechanistic understanding of mitochondrial fusion and division will be critical to inform further therapeutic approaches, mitochondrial dynamics represent a powerful therapeutic target in a wide range of human diseases.
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20
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Escobar-Henriques M, Joaquim M. Mitofusins: Disease Gatekeepers and Hubs in Mitochondrial Quality Control by E3 Ligases. Front Physiol 2019; 10:517. [PMID: 31156446 PMCID: PMC6533591 DOI: 10.3389/fphys.2019.00517] [Citation(s) in RCA: 49] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2019] [Accepted: 04/11/2019] [Indexed: 02/06/2023] Open
Abstract
Mitochondria are dynamic organelles engaged in quality control and aging processes. They constantly undergo fusion, fission, transport, and anchoring events, which empower mitochondria with a very interactive behavior. The membrane remodeling processes needed for fusion require conserved proteins named mitofusins, MFN1 and MFN2 in mammals and Fzo1 in yeast. They are the first determinants deciding on whether communication and content exchange between different mitochondrial populations should occur. Importantly, each cell possesses hundreds of mitochondria, with a different severity of mitochondrial mutations or dysfunctional proteins, which potentially spread damage to the entire network. Therefore, the degree of their merging capacity critically influences cellular fitness. In turn, the mitochondrial network rapidly and dramatically changes in response to metabolic and environmental cues. Notably, cancer or obesity conditions, and stress experienced by neurons and cardiomyocytes, for example, triggers the downregulation of mitofusins and thus fragmentation of mitochondria. This places mitofusins upfront in sensing and transmitting stress. In fact, mitofusins are almost entirely exposed to the cytoplasm, a topology suitable for a critical relay point in information exchange between mitochondria and their cellular environment. Consistent with their topology, mitofusins are either activated or repressed by cytosolic post-translational modifiers, mainly by ubiquitin. Ubiquitin is a ubiquitous small protein orchestrating multiple quality control pathways, which is covalently attached to lysine residues in its substrates, or in ubiquitin itself. Importantly, from a chain of events also mediated by E1 and E2 enzymes, E3 ligases perform the ultimate and determinant step in substrate choice. Here, we review the ubiquitin E3 ligases that modify mitofusins. Two mitochondrial E3 enzymes—March5 and MUL1—one ligase located to the ER—Gp78—and finally three cytosolic enzymes—MGRN1, HUWE1, and Parkin—were shown to ubiquitylate mitofusins, in response to a variety of cellular inputs. The respective outcomes on mitochondrial morphology, on contact sites to the endoplasmic reticulum and on destructive processes, like mitophagy or apoptosis, are presented. Ultimately, understanding the mechanisms by which E3 ligases and mitofusins sense and bi-directionally signal mitochondria-cytosolic dysfunctions could pave the way for therapeutic approaches in neurodegenerative, cardiovascular, and obesity-linked diseases.
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Affiliation(s)
- Mafalda Escobar-Henriques
- Center for Molecular Medicine Cologne (CMMC), Institute for Genetics, Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Cologne, Germany
| | - Mariana Joaquim
- Center for Molecular Medicine Cologne (CMMC), Institute for Genetics, Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Cologne, Germany
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