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Koludarova L, Battersby BJ. Mitochondrial protein synthesis quality control. Hum Mol Genet 2024:ddae012. [PMID: 38280230 DOI: 10.1093/hmg/ddae012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2023] [Accepted: 01/05/2023] [Indexed: 01/29/2024] Open
Abstract
Human mitochondrial DNA is one of the most simplified cellular genomes and facilitates compartmentalized gene expression. Within the organelle, there is no physical barrier to separate transcription and translation, nor is there evidence that quality control surveillance pathways are active to prevent translation on faulty mRNA transcripts. Mitochondrial ribosomes synthesize 13 hydrophobic proteins that require co-translational insertion into the inner membrane of the organelle. To maintain the integrity of the inner membrane, which is essential for organelle function, requires responsive quality control mechanisms to recognize aberrations in protein synthesis. In this review, we explore how defects in mitochondrial protein synthesis can arise due to the culmination of inherent mistakes that occur throughout the steps of gene expression. In turn, we examine the stepwise series of quality control processes that are needed to eliminate any mistakes that would perturb organelle homeostasis. We aim to provide an integrated view on the quality control mechanisms of mitochondrial protein synthesis and to identify promising avenues for future research.
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Affiliation(s)
- Lidiia Koludarova
- Institute of Biotechnology, HiLIFE, University of Helsinki, Helsinki 00014, Finland
| | - Brendan J Battersby
- Institute of Biotechnology, HiLIFE, University of Helsinki, Helsinki 00014, Finland
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2
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Gorski K, Jackson CB, Nyman TA, Rezov V, Battersby BJ, Lehesjoki AE. Progressive mitochondrial dysfunction in cerebellar synaptosomes of cystatin B-deficient mice. Front Mol Neurosci 2023; 16:1175851. [PMID: 37251643 PMCID: PMC10213208 DOI: 10.3389/fnmol.2023.1175851] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2023] [Accepted: 04/25/2023] [Indexed: 05/31/2023] Open
Abstract
The involvement of mitochondrial dysfunction in cystatin B (CSTB) deficiency has been suggested, but its role in the onset of neurodegeneration, myoclonus, and ataxia in the CSTB-deficient mouse model (Cstb-/-) is yet unknown. CSTB is an inhibitor of lysosomal and nuclear cysteine cathepsins. In humans, partial loss-of-function mutations cause the progressive myoclonus epilepsy neurodegenerative disorder, EPM1. Here we applied proteome analysis and respirometry on cerebellar synaptosomes from early symptomatic (Cstb-/-) mice to identify the molecular mechanisms involved in the onset of CSTB-deficiency associated neural pathogenesis. Proteome analysis showed that CSTB deficiency is associated with differential expression of mitochondrial and synaptic proteins, and respirometry revealed a progressive impairment in mitochondrial function coinciding with the onset of myoclonus and neurodegeneration in (Cstb-/-) mice. This mitochondrial dysfunction was not associated with alterations in mitochondrial DNA copy number or membrane ultrastructure. Collectively, our results show that CSTB deficiency generates a defect in synaptic mitochondrial bioenergetics that coincides with the onset and progression of the clinical phenotypes, and thus is likely a contributor to the pathogenesis of EPM1.
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Affiliation(s)
- Katarin Gorski
- Folkhälsan Research Center, Helsinki, Finland
- Medicum, Faculty of Medicine, University of Helsinki, Helsinki, Finland
| | - Christopher B. Jackson
- Department of Biochemistry and Developmental Biology, Medicum, Faculty of Medicine, University of Helsinki, Helsinki, Finland
| | - Tuula A. Nyman
- Department of Immunology, Oslo University Hospital, University of Oslo, Oslo, Norway
| | - Veronika Rezov
- Folkhälsan Research Center, Helsinki, Finland
- Medicum, Faculty of Medicine, University of Helsinki, Helsinki, Finland
| | | | - Anna-Elina Lehesjoki
- Folkhälsan Research Center, Helsinki, Finland
- Medicum, Faculty of Medicine, University of Helsinki, Helsinki, Finland
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3
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Jett KA, Baker ZN, Hossain A, Boulet A, Cobine PA, Ghosh S, Ng P, Yilmaz O, Barreto K, DeCoteau J, Mochoruk K, Ioannou GN, Savard C, Yuan S, Abdalla OH, Lowden C, Kim BE, Cheng HYM, Battersby BJ, Gohil VM, Leary SC. Mitochondrial dysfunction reactivates α-fetoprotein expression that drives copper-dependent immunosuppression in mitochondrial disease models. J Clin Invest 2023; 133:154684. [PMID: 36301669 PMCID: PMC9797342 DOI: 10.1172/jci154684] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2021] [Accepted: 10/26/2022] [Indexed: 02/04/2023] Open
Abstract
Signaling circuits crucial to systemic physiology are widespread, yet uncovering their molecular underpinnings remains a barrier to understanding the etiology of many metabolic disorders. Here, we identified a copper-linked signaling circuit activated by disruption of mitochondrial function in the murine liver or heart that resulted in atrophy of the spleen and thymus and caused a peripheral white blood cell deficiency. We demonstrated that the leukopenia was caused by α-fetoprotein, which required copper and the cell surface receptor CCR5 to promote white blood cell death. We further showed that α-fetoprotein expression was upregulated in several cell types upon inhibition of oxidative phosphorylation. Collectively, our data argue that α-fetoprotein may be secreted by bioenergetically stressed tissue to suppress the immune system, an effect that may explain the recurrent or chronic infections that are observed in a subset of mitochondrial diseases or in other disorders with secondary mitochondrial dysfunction.
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Affiliation(s)
- Kimberly A. Jett
- Department of Biochemistry, Microbiology and Immunology, University of Saskatchewan, Saskatoon, Canada
| | - Zakery N. Baker
- Department of Biochemistry, Microbiology and Immunology, University of Saskatchewan, Saskatoon, Canada
| | - Amzad Hossain
- Department of Biochemistry, Microbiology and Immunology, University of Saskatchewan, Saskatoon, Canada
| | - Aren Boulet
- Department of Biochemistry, Microbiology and Immunology, University of Saskatchewan, Saskatoon, Canada
| | - Paul A. Cobine
- Department of Biological Sciences, Auburn University, Auburn, Alabama, USA
| | - Sagnika Ghosh
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas, USA
| | - Philip Ng
- Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, USA
| | - Orhan Yilmaz
- Department of Biochemistry, Microbiology and Immunology, University of Saskatchewan, Saskatoon, Canada
| | - Kris Barreto
- Department of Laboratory and Pathology Medicine, University of Saskatchewan, Saskatoon, Canada
| | - John DeCoteau
- Department of Laboratory and Pathology Medicine, University of Saskatchewan, Saskatoon, Canada
| | - Karen Mochoruk
- Department of Laboratory and Pathology Medicine, University of Saskatchewan, Saskatoon, Canada
| | - George N. Ioannou
- Division of Gastroenterology,,Research and Development, Veterans Affairs Puget Sound Health Care System and the,Division of Gastroenterology, Department of Medicine, University of Washington, Seattle, Washington, USA
| | - Christopher Savard
- Division of Gastroenterology,,Research and Development, Veterans Affairs Puget Sound Health Care System and the,Division of Gastroenterology, Department of Medicine, University of Washington, Seattle, Washington, USA
| | - Sai Yuan
- Department of Animal and Avian Sciences, University of Maryland, College Park, Maryland, USA
| | - Osama H.M.H. Abdalla
- Department of Biology, University of Toronto Mississauga, Mississauga, Ontario, Canada.,Department of Cell and Systems Biology, University of Toronto, Toronto, Canada
| | - Christopher Lowden
- Department of Biology, University of Toronto Mississauga, Mississauga, Ontario, Canada.,Department of Cell and Systems Biology, University of Toronto, Toronto, Canada
| | - Byung-Eun Kim
- Department of Animal and Avian Sciences, University of Maryland, College Park, Maryland, USA
| | - Hai-Ying Mary Cheng
- Department of Biology, University of Toronto Mississauga, Mississauga, Ontario, Canada.,Department of Cell and Systems Biology, University of Toronto, Toronto, Canada
| | | | - Vishal M. Gohil
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas, USA
| | - Scot C. Leary
- Department of Biochemistry, Microbiology and Immunology, University of Saskatchewan, Saskatoon, Canada
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4
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Ng KY, Battersby BJ. Sucrose Gradient Analysis of Human Mitochondrial Ribosomes and RNA. Methods Mol Biol 2023; 2661:101-117. [PMID: 37166634 DOI: 10.1007/978-1-0716-3171-3_7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Faithful expression of the mitochondrial genome is required for the synthesis of the oxidative phosphorylation complexes and cell fitness. In humans, mitochondrial DNA (mtDNA) encodes 13 essential subunits of four oxidative phosphorylation complexes along with tRNAs and rRNAs needed for the translation of these proteins. Protein synthesis occurs on unique ribosomes within the organelle. Over the last decade, the revolution in genetic diagnostics has identified disruptions to the faithful synthesis of these 13 mitochondrial proteins as the largest group of inherited human mitochondrial pathologies. All of the molecular steps required for mitochondrial protein synthesis can be affected, from the genome to protein, including cotranslational quality control. Here, we describe methodologies for the biochemical separation of mitochondrial ribosomes from cultured human cells for RNA and protein analysis. Our method has been optimized to facilitate analysis for low-level sample material and thus does not require prior organelle enrichment.
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Affiliation(s)
- Kah Ying Ng
- Institute of Biotechnology, Helsinki Institute of Life Science, University of Helsinki, Helsinki, Finland
| | - Brendan J Battersby
- Institute of Biotechnology, Helsinki Institute of Life Science, University of Helsinki, Helsinki, Finland.
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5
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Ng KY, Lutfullahoglu Bal G, Richter U, Safronov O, Paulin L, Dunn CD, Paavilainen VO, Richer J, Newman WG, Taylor RW, Battersby BJ. Nonstop mRNAs generate a ground state of mitochondrial gene expression noise. Sci Adv 2022; 8:eabq5234. [PMID: 36399564 PMCID: PMC9674279 DOI: 10.1126/sciadv.abq5234] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/13/2022] [Accepted: 10/22/2022] [Indexed: 05/29/2023]
Abstract
A stop codon within the mRNA facilitates coordinated termination of protein synthesis, releasing the nascent polypeptide from the ribosome. This essential step in gene expression is impeded with transcripts lacking a stop codon, generating nonstop ribosome complexes. Here, we use deep sequencing to investigate sources of nonstop mRNAs generated from the human mitochondrial genome. We identify diverse types of nonstop mRNAs on mitochondrial ribosomes that are resistant to translation termination by canonical release factors. Failure to resolve these aberrations by the mitochondrial release factor in rescue (MTRFR) imparts a negative regulatory effect on protein synthesis that is associated with human disease. Our findings reveal a source of underlying noise in mitochondrial gene expression and the importance of responsive ribosome quality control mechanisms for cell fitness and human health.
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Affiliation(s)
- Kah Ying Ng
- Institute of Biotechnology, Helsinki Institute of Life Science, University of Helsinki, Helsinki, Finland
| | - Guleycan Lutfullahoglu Bal
- Institute of Biotechnology, Helsinki Institute of Life Science, University of Helsinki, Helsinki, Finland
| | - Uwe Richter
- Institute of Biotechnology, Helsinki Institute of Life Science, University of Helsinki, Helsinki, Finland
- Faculty of Biological and Environmental Sciences, University of Helsinki, Helsinki, Finland
- Wellcome Centre for Mitochondrial Research, Biosciences Institute, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, UK
| | - Omid Safronov
- Institute of Biotechnology, Helsinki Institute of Life Science, University of Helsinki, Helsinki, Finland
- Faculty of Biological and Environmental Sciences, University of Helsinki, Helsinki, Finland
| | - Lars Paulin
- Institute of Biotechnology, Helsinki Institute of Life Science, University of Helsinki, Helsinki, Finland
- DNA Sequencing and Genomics Laboratory, University of Helsinki, Helsinki, Finland
| | - Cory D. Dunn
- Institute of Biotechnology, Helsinki Institute of Life Science, University of Helsinki, Helsinki, Finland
| | - Ville O. Paavilainen
- Institute of Biotechnology, Helsinki Institute of Life Science, University of Helsinki, Helsinki, Finland
| | - Julie Richer
- Department of Medical Genetics, Children’s Hospital of Eastern Ontario, Ottawa, ON, Canada
| | - William G. Newman
- Manchester Centre for Genomic Medicine, St. Mary’s Hospital, Manchester University NHS Foundation Trust, Manchester, UK
- Division of Evolution, Infection and Genomics, School of Biological Sciences, University of Manchester, Manchester, UK
| | - Robert W. Taylor
- Wellcome Centre for Mitochondrial Research, Translational and Clinical Research Institute, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, UK
- NHS Highly Specialised Service for Rare Mitochondrial Disorders, Newcastle upon Tyne Hospitals NHS Foundation Trust, Newcastle upon Tyne, UK
| | - Brendan J. Battersby
- Institute of Biotechnology, Helsinki Institute of Life Science, University of Helsinki, Helsinki, Finland
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6
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Hochberg I, Demain LA, Richer J, Thompson K, Urquhart JE, Rea A, Pagarkar W, Rodríguez-Palmero A, Schlüter A, Verdura E, Pujol A, Quijada-Fraile P, Amberger A, Deutschmann AJ, Demetz S, Gillespie M, Belyantseva IA, McMillan HJ, Barzik M, Beaman GM, Motha R, Ng KY, O’Sullivan J, Williams SG, Bhaskar SS, Lawrence IR, Jenkinson EM, Zambonin JL, Blumenfeld Z, Yalonetsky S, Oerum S, Rossmanith W, Yue WW, Zschocke J, Munro KJ, Battersby BJ, Friedman TB, Taylor RW, O’Keefe RT, Newman WG, Newman WG. Bi-allelic variants in the mitochondrial RNase P subunit PRORP cause mitochondrial tRNA processing defects and pleiotropic multisystem presentations. Am J Hum Genet 2021; 108:2195-2204. [PMID: 34715011 PMCID: PMC8595931 DOI: 10.1016/j.ajhg.2021.10.002] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2021] [Accepted: 10/07/2021] [Indexed: 02/03/2023] Open
Abstract
Human mitochondrial RNase P (mt-RNase P) is responsible for 5′ end processing of mitochondrial precursor tRNAs, a vital step in mitochondrial RNA maturation, and is comprised of three protein subunits: TRMT10C, SDR5C1 (HSD10), and PRORP. Pathogenic variants in TRMT10C and SDR5C1 are associated with distinct recessive or x-linked infantile onset disorders, resulting from defects in mitochondrial RNA processing. We report four unrelated families with multisystem disease associated with bi-allelic variants in PRORP, the metallonuclease subunit of mt-RNase P. Affected individuals presented with variable phenotypes comprising sensorineural hearing loss, primary ovarian insufficiency, developmental delay, and brain white matter changes. Fibroblasts from affected individuals in two families demonstrated decreased steady state levels of PRORP, an accumulation of unprocessed mitochondrial transcripts, and decreased steady state levels of mitochondrial-encoded proteins, which were rescued by introduction of the wild-type PRORP cDNA. In mt-tRNA processing assays performed with recombinant mt-RNase P proteins, the disease-associated variants resulted in diminished mitochondrial tRNA processing. Identification of disease-causing variants in PRORP indicates that pathogenic variants in all three subunits of mt-RNase P can cause mitochondrial dysfunction, each with distinct pleiotropic clinical presentations.
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Affiliation(s)
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | - William G Newman
- Division of Evolution, Infection, and Genomics, School of Biological Sciences, University of Manchester, Manchester M13 9PL, UK; Manchester Centre for Genomic Medicine, St Mary's Hospital, Manchester University NHS Foundation Trust, Manchester M13 9WL, UK.
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7
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Ng KY, Richter U, Jackson CB, Seneca S, Battersby BJ. Translation of MT-ATP6 pathogenic variants reveals distinct regulatory consequences from the co-translational quality control of mitochondrial protein synthesis. Hum Mol Genet 2021; 31:1230-1241. [PMID: 34718584 PMCID: PMC9029222 DOI: 10.1093/hmg/ddab314] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2021] [Revised: 10/15/2021] [Accepted: 10/18/2021] [Indexed: 11/16/2022] Open
Abstract
Pathogenic variants that disrupt human mitochondrial protein synthesis are associated with a clinically heterogeneous group of diseases. Despite an impairment in oxidative phosphorylation being a common phenotype, the underlying molecular pathogenesis is more complex than simply a bioenergetic deficiency. Currently, we have limited mechanistic understanding on the scope by which a primary defect in mitochondrial protein synthesis contributes to organelle dysfunction. Since the proteins encoded in the mitochondrial genome are hydrophobic and need co-translational insertion into a lipid bilayer, responsive quality control mechanisms are required to resolve aberrations that arise with the synthesis of truncated and misfolded proteins. Here, we show that defects in the OXA1L-mediated insertion of MT-ATP6 nascent chains into the mitochondrial inner membrane are rapidly resolved by the AFG3L2 protease complex. Using pathogenic MT-ATP6 variants, we then reveal discrete steps in this quality control mechanism and the differential functional consequences to mitochondrial gene expression. The inherent ability of a given cell type to recognize and resolve impairments in mitochondrial protein synthesis may in part contribute at the molecular level to the wide clinical spectrum of these disorders.
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Affiliation(s)
- Kah Ying Ng
- Institute of Biotechnology, University of Helsinki, Helsinki, Finland
| | - Uwe Richter
- Faculty of Biological and Environmental Sciences, University of Helsinki, Helsinki, Finland.,Wellcome Centre for Mitochondrial Research, Biosciences Institute, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, UK
| | - Christopher B Jackson
- Department of Biochemistry and Developmental Biology, Faculty of Medicine, University of Helsinki, Helsinki, Finland
| | - Sara Seneca
- Center for Medical Genetics/Research Center Reproduction and Genetics, Universitair Ziekenhuis Brussel, Vrije Universiteit Brussel (VUB), Brussels, Belgium
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8
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Itoh Y, Andréll J, Choi A, Richter U, Maiti P, Best RB, Barrientos A, Battersby BJ, Amunts A. Mechanism of membrane-tethered mitochondrial protein synthesis. Science 2021; 371:846-849. [PMID: 33602856 PMCID: PMC7610362 DOI: 10.1126/science.abe0763] [Citation(s) in RCA: 61] [Impact Index Per Article: 20.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2020] [Accepted: 12/24/2020] [Indexed: 12/11/2022]
Abstract
Mitochondrial ribosomes (mitoribosomes) are tethered to the mitochondrial inner membrane to facilitate the cotranslational membrane insertion of the synthesized proteins. We report cryo-electron microscopy structures of human mitoribosomes with nascent polypeptide, bound to the insertase oxidase assembly 1-like (OXA1L) through three distinct contact sites. OXA1L binding is correlated with a series of conformational changes in the mitoribosomal large subunit that catalyze the delivery of newly synthesized polypeptides. The mechanism relies on the folding of mL45 inside the exit tunnel, forming two specific constriction sites that would limit helix formation of the nascent chain. A gap is formed between the exit and the membrane, making the newly synthesized proteins accessible. Our data elucidate the basis by which mitoribosomes interact with the OXA1L insertase to couple protein synthesis and membrane delivery.
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Affiliation(s)
- Yuzuru Itoh
- Science for Life Laboratory, Department of Biochemistry and Biophysics, Stockholm University, 17165 Solna, Stockholm, Sweden.
- Department of Medical Biochemistry and Biophysics, Karolinska Institutet, 17177 Stockholm, Sweden
| | - Juni Andréll
- Science for Life Laboratory, Department of Biochemistry and Biophysics, Stockholm University, 17165 Solna, Stockholm, Sweden.
- Department of Medical Biochemistry and Biophysics, Karolinska Institutet, 17177 Stockholm, Sweden
| | - Austin Choi
- Department of Neurology, University of Miami Miller School of Medicine, Miami, FL 33136, USA.
| | - Uwe Richter
- Institute of Biotechnology, University of Helsinki, 00790 Helsinki, Finland.
- Faculty of Biological and Environmental Sciences, University of Helsinki, 00790 Helsinki, Finland
- Wellcome Centre for Mitochondrial Research, Biosciences Institute, Newcastle University, Newcastle upon Tyne NE2 4HH, UK
| | - Priyanka Maiti
- Department of Neurology, University of Miami Miller School of Medicine, Miami, FL 33136, USA
| | - Robert B Best
- Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892-0520, USA
| | - Antoni Barrientos
- Department of Neurology, University of Miami Miller School of Medicine, Miami, FL 33136, USA.
| | - Brendan J Battersby
- Institute of Biotechnology, University of Helsinki, 00790 Helsinki, Finland.
| | - Alexey Amunts
- Science for Life Laboratory, Department of Biochemistry and Biophysics, Stockholm University, 17165 Solna, Stockholm, Sweden.
- Department of Medical Biochemistry and Biophysics, Karolinska Institutet, 17177 Stockholm, Sweden
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9
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Gorski K, Spoljaric A, Nyman TA, Kaila K, Battersby BJ, Lehesjoki AE. Quantitative Changes in the Mitochondrial Proteome of Cerebellar Synaptosomes From Preclinical Cystatin B-Deficient Mice. Front Mol Neurosci 2020; 13:570640. [PMID: 33281550 PMCID: PMC7691638 DOI: 10.3389/fnmol.2020.570640] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2020] [Accepted: 10/21/2020] [Indexed: 12/04/2022] Open
Abstract
Progressive myoclonus epilepsy of Unverricht-Lundborg type (EPM1) is a neurodegenerative disorder caused by loss-of-function mutations in the cystatin B (CSTB) gene. Progression of the clinical symptoms in EPM1 patients, including stimulus-sensitive myoclonus, tonic-clonic seizures, and ataxia, are well described. However, the cellular dysfunction during the presymptomatic phase that precedes the disease onset is not understood. CSTB deficiency leads to alterations in GABAergic signaling, and causes early neuroinflammation followed by progressive neurodegeneration in brains of a mouse model, manifesting as progressive myoclonus and ataxia. Here, we report the first proteome atlas from cerebellar synaptosomes of presymptomatic Cstb-deficient mice, and propose that early mitochondrial dysfunction is important to the pathogenesis of altered synaptic function in EPM1. A decreased sodium- and chloride dependent GABA transporter 1 (GAT-1) abundance was noted in synaptosomes with CSTB deficiency, but no functional difference was seen between the two genotypes in electrophysiological experiments with pharmacological block of GAT-1. Collectively, our findings provide novel insights into the early onset and pathogenesis of CSTB deficiency, and reveal greater complexity to the molecular pathogenesis of EPM1.
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Affiliation(s)
- Katarin Gorski
- Folkhälsan Research Center, Helsinki, Finland.,Department of Medical and Clinical Genetics, Medicum, University of Helsinki, Helsinki, Finland
| | - Albert Spoljaric
- Molecular and Integrative Biosciences, and Neuroscience Center (HiLIFE), Faculty of Biological and Environmental Sciences, University of Helsinki, Helsinki, Finland
| | - Tuula A Nyman
- Institute of Clinical Medicine, University of Oslo and Oslo University Hospital, Oslo, Norway
| | - Kai Kaila
- Molecular and Integrative Biosciences, and Neuroscience Center (HiLIFE), Faculty of Biological and Environmental Sciences, University of Helsinki, Helsinki, Finland
| | | | - Anna-Elina Lehesjoki
- Folkhälsan Research Center, Helsinki, Finland.,Department of Medical and Clinical Genetics, Medicum, University of Helsinki, Helsinki, Finland
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10
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Forsström S, Jackson CB, Carroll CJ, Kuronen M, Pirinen E, Pradhan S, Marmyleva A, Auranen M, Kleine IM, Khan NA, Roivainen A, Marjamäki P, Liljenbäck H, Wang L, Battersby BJ, Richter U, Velagapudi V, Nikkanen J, Euro L, Suomalainen A. Fibroblast Growth Factor 21 Drives Dynamics of Local and Systemic Stress Responses in Mitochondrial Myopathy with mtDNA Deletions. Cell Metab 2019; 30:1040-1054.e7. [PMID: 31523008 DOI: 10.1016/j.cmet.2019.08.019] [Citation(s) in RCA: 128] [Impact Index Per Article: 25.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/08/2019] [Revised: 07/09/2019] [Accepted: 08/20/2019] [Indexed: 11/28/2022]
Abstract
Mitochondrial dysfunction elicits stress responses that safeguard cellular homeostasis against metabolic insults. Mitochondrial integrated stress response (ISRmt) is a major response to mitochondrial (mt)DNA expression stress (mtDNA maintenance, translation defects), but the knowledge of dynamics or interdependence of components is lacking. We report that in mitochondrial myopathy, ISRmt progresses in temporal stages and development from early to chronic and is regulated by autocrine and endocrine effects of FGF21, a metabolic hormone with pleiotropic effects. Initial disease signs induce transcriptional ISRmt (ATF5, mitochondrial one-carbon cycle, FGF21, and GDF15). The local progression to 2nd metabolic ISRmt stage (ATF3, ATF4, glucose uptake, serine biosynthesis, and transsulfuration) is FGF21 dependent. Mitochondrial unfolded protein response marks the 3rd ISRmt stage of failing tissue. Systemically, FGF21 drives weight loss and glucose preference, and modifies metabolism and respiratory chain deficiency in a specific hippocampal brain region. Our evidence indicates that FGF21 is a local and systemic messenger of mtDNA stress in mice and humans with mitochondrial disease.
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Affiliation(s)
- Saara Forsström
- Stem Cells and Metabolism Research Program, Faculty of Medicine, University of Helsinki, 00290 Helsinki, Finland
| | - Christopher B Jackson
- Stem Cells and Metabolism Research Program, Faculty of Medicine, University of Helsinki, 00290 Helsinki, Finland
| | - Christopher J Carroll
- Stem Cells and Metabolism Research Program, Faculty of Medicine, University of Helsinki, 00290 Helsinki, Finland; Molecular and Clinical Sciences Research Institute, St. George's University of London, London SW170RE, UK
| | - Mervi Kuronen
- Stem Cells and Metabolism Research Program, Faculty of Medicine, University of Helsinki, 00290 Helsinki, Finland
| | - Eija Pirinen
- Clinical and Molecular Metabolism Research Program, Faculty of Medicine, University of Helsinki, 00290 Helsinki, Finland
| | - Swagat Pradhan
- Stem Cells and Metabolism Research Program, Faculty of Medicine, University of Helsinki, 00290 Helsinki, Finland
| | - Anastasiia Marmyleva
- Stem Cells and Metabolism Research Program, Faculty of Medicine, University of Helsinki, 00290 Helsinki, Finland
| | - Mari Auranen
- Department of Neurosciences, Helsinki University Central Hospital, 00290 Helsinki, Finland
| | - Iida-Marja Kleine
- Stem Cells and Metabolism Research Program, Faculty of Medicine, University of Helsinki, 00290 Helsinki, Finland
| | - Nahid A Khan
- Stem Cells and Metabolism Research Program, Faculty of Medicine, University of Helsinki, 00290 Helsinki, Finland
| | - Anne Roivainen
- Turku PET Centre, University of Turku, 20520 Turku, Finland; Turku Center for Disease Modeling, Institute of Biomedicine, University of Turku, 20520 Turku, Finland
| | | | - Heidi Liljenbäck
- Turku PET Centre, University of Turku, 20520 Turku, Finland; Turku Center for Disease Modeling, Institute of Biomedicine, University of Turku, 20520 Turku, Finland
| | - Liya Wang
- Department of Anatomy, Physiology, and Biochemistry, Swedish University of Agricultural Sciences, 75007 Uppsala, Sweden
| | | | - Uwe Richter
- Institute of Biotechnology, University of Helsinki, 00790 Helsinki, Finland
| | - Vidya Velagapudi
- Metabolomics Unit, Institute for Molecular Medicine Finland FIMM, HiLIFE, University of Helsinki, 00290 Helsinki, Finland
| | - Joni Nikkanen
- Stem Cells and Metabolism Research Program, Faculty of Medicine, University of Helsinki, 00290 Helsinki, Finland
| | - Liliya Euro
- Stem Cells and Metabolism Research Program, Faculty of Medicine, University of Helsinki, 00290 Helsinki, Finland
| | - Anu Suomalainen
- Stem Cells and Metabolism Research Program, Faculty of Medicine, University of Helsinki, 00290 Helsinki, Finland; Department of Neurosciences, Helsinki University Central Hospital, 00290 Helsinki, Finland; Neuroscience Center, University of Helsinki, 00290 Helsinki, Finland.
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11
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Abstract
Proteotoxicity has long been considered a key factor in mitochondrial dysfunction and human disease. The origin of the endogenous offending toxic substrates and the regulatory pathways to deal with these insults, however, have remained unclear. Mitochondria maintain a compartmentalized gene expression system that in animals is only responsible for synthesis of 1% of the organelle proteome. Because of the relatively small contribution of the mitochondrial genome to the overall proteome, the synthesis and quality control of these nascent chains to maintain organelle proteostasis has long been overlooked. However, recent research has uncovered mechanisms by which defects to the quality control of mitochondrial gene expression are linked to a novel cellular stress response that impinges upon organelle form and function and cell fitness. In this review, we discuss the mechanisms for a key event in the response: activation of the metalloprotease OMA1. This severs the membrane tether of the dynamin-related GTPase OPA1, which is a critical determinant for mitochondrial morphology and function. We also highlight the evolutionary conservation from bacteria of these quality-control mechanisms to maintain membrane integrity, gene expression, and cell fitness.
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Affiliation(s)
| | - Uwe Richter
- Institute of Biotechnology, University of Helsinki, Helsinki 00014, Finland
| | - Omid Safronov
- Institute of Biotechnology, University of Helsinki, Helsinki 00014, Finland
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12
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Jackson CB, Huemer M, Bolognini R, Martin F, Szinnai G, Donner BC, Richter U, Battersby BJ, Nuoffer JM, Suomalainen A, Schaller A. A variant in MRPS14 (uS14m) causes perinatal hypertrophic cardiomyopathy with neonatal lactic acidosis, growth retardation, dysmorphic features and neurological involvement. Hum Mol Genet 2019; 28:639-649. [PMID: 30358850 DOI: 10.1093/hmg/ddy374] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2018] [Accepted: 10/16/2018] [Indexed: 11/13/2022] Open
Abstract
Dysfunction of mitochondrial translation is an increasingly important molecular cause of human disease, but structural defects of mitochondrial ribosomal subunits are rare. We used next-generation sequencing to identify a homozygous variant in the mitochondrial small ribosomal protein 14 (MRPS14, uS14m) in a patient manifesting with perinatal hypertrophic cardiomyopathy, growth retardation, muscle hypotonia, elevated lactate, dysmorphy and mental retardation. In skeletal muscle and fibroblasts from the patient, there was biochemical deficiency in complex IV of the respiratory chain. In fibroblasts, mitochondrial translation was impaired, and ectopic expression of a wild-type MRPS14 cDNA functionally complemented this defect. Surprisingly, the mutant uS14m was stable and did not affect assembly of the small ribosomal subunit. Instead, structural modeling of the uS14m mutation predicted a disruption to the ribosomal mRNA channel.Collectively, our data demonstrate pathogenic mutations in MRPS14 can manifest as a perinatal-onset mitochondrial hypertrophic cardiomyopathy with a novel molecular pathogenic mechanism that impairs the function of mitochondrial ribosomes during translation elongation or mitochondrial mRNA recruitment rather than assembly.
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Affiliation(s)
- Christopher B Jackson
- Research Programs Unit, Molecular Neurology, Biomedicum Helsinki, University of Helsinki, Helsinki FIN, Finland
| | - Martina Huemer
- Division of Metabolism and Children's Research Center, University Children's Hospital Zürich, Zürich CH, Switzerland.,University Children's Hospital Basel, University of Basel, Switzerland
| | - Ramona Bolognini
- Division of Human Genetics, Department of Pediatrics, Inselspital, Bern University Hospital, University of Bern, Bern CH, Switzerland
| | - Franck Martin
- CNRS, Architecture et Réactivité de l'ARN, Université de Strasbourg, UPR 9002, Strasbourg F, France
| | - Gabor Szinnai
- University Children's Hospital Basel, University of Basel, Switzerland.,Division of Pediatric Endocrinology, University Children's Hospital Basel, Basel CH, Switzerland
| | - Birgit C Donner
- Division of Cardiology, University of Basel, Basel CH, Switzerland
| | - Uwe Richter
- Institute of Biotechnology, University of Helsinki, Helsinki, FIN, Finland
| | | | - Jean-Marc Nuoffer
- Institute of Clinical Chemistry, University of Bern, Inselspital, Bern CH, Switzerland.,Division of Endocrinology Diabetology and Metabolism, University Children's Hospital, University of Bern, Bern CH, Switzerland
| | - Anu Suomalainen
- Research Programs Unit, Molecular Neurology, Biomedicum Helsinki, University of Helsinki, Helsinki FIN, Finland.,Neuroscience Center, University of Helsinki, Helsinki FIN, Finland
| | - André Schaller
- Division of Human Genetics, Department of Pediatrics, Inselspital, Bern University Hospital, University of Bern, Bern CH, Switzerland
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13
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Thompson K, Mai N, Oláhová M, Scialó F, Formosa LE, Stroud DA, Garrett M, Lax NZ, Robertson FM, Jou C, Nascimento A, Ortez C, Jimenez-Mallebrera C, Hardy SA, He L, Brown GK, Marttinen P, McFarland R, Sanz A, Battersby BJ, Bonnen PE, Ryan MT, Chrzanowska-Lightowlers ZM, Lightowlers RN, Taylor RW. OXA1L mutations cause mitochondrial encephalopathy and a combined oxidative phosphorylation defect. EMBO Mol Med 2019; 10:emmm.201809060. [PMID: 30201738 PMCID: PMC6220311 DOI: 10.15252/emmm.201809060] [Citation(s) in RCA: 45] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
OXA1, the mitochondrial member of the YidC/Alb3/Oxa1 membrane protein insertase family, is required for the assembly of oxidative phosphorylation complexes IV and V in yeast. However, depletion of human OXA1 (OXA1L) was previously reported to impair assembly of complexes I and V only. We report a patient presenting with severe encephalopathy, hypotonia and developmental delay who died at 5 years showing complex IV deficiency in skeletal muscle. Whole exome sequencing identified biallelic OXA1L variants (c.500_507dup, p.(Ser170Glnfs*18) and c.620G>T, p.(Cys207Phe)) that segregated with disease. Patient muscle and fibroblasts showed decreased OXA1L and subunits of complexes IV and V. Crucially, expression of wild‐type human OXA1L in patient fibroblasts rescued the complex IV and V defects. Targeted depletion of OXA1L in human cells or Drosophila melanogaster caused defects in the assembly of complexes I, IV and V, consistent with patient data. Immunoprecipitation of OXA1L revealed the enrichment of mtDNA‐encoded subunits of complexes I, IV and V. Our data verify the pathogenicity of these OXA1L variants and demonstrate that OXA1L is required for the assembly of multiple respiratory chain complexes.
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Affiliation(s)
- Kyle Thompson
- Wellcome Centre for Mitochondrial Research, Newcastle University, Newcastle upon Tyne, UK
| | - Nicole Mai
- Wellcome Centre for Mitochondrial Research, Newcastle University, Newcastle upon Tyne, UK
| | - Monika Oláhová
- Wellcome Centre for Mitochondrial Research, Newcastle University, Newcastle upon Tyne, UK
| | - Filippo Scialó
- Institute for Cell and Molecular Biosciences, Newcastle University Institute for Ageing, Newcastle University, Newcastle upon Tyne, UK
| | - Luke E Formosa
- Department of Biochemistry and Molecular Biology, Monash Biomedicine Discovery Institute, Monash University, Melbourne, Vic., Australia
| | - David A Stroud
- Department of Biochemistry and Molecular Biology and The Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Parkville, Vic., Australia
| | - Madeleine Garrett
- Department of Biochemistry and Molecular Biology, Monash Biomedicine Discovery Institute, Monash University, Melbourne, Vic., Australia
| | - Nichola Z Lax
- Wellcome Centre for Mitochondrial Research, Newcastle University, Newcastle upon Tyne, UK
| | - Fiona M Robertson
- Wellcome Centre for Mitochondrial Research, Newcastle University, Newcastle upon Tyne, UK
| | - Cristina Jou
- Pathology Department, Hospital Sant Joan de Déu, CIBERER, Barcelona, Spain
| | - Andres Nascimento
- Neuromuscular Unit, Neuropaediatrics Department, Hospital Sant Joan de Déu, CIBERER - ISCIII, Barcelona, Spain
| | - Carlos Ortez
- Neuromuscular Unit, Neuropaediatrics Department, Hospital Sant Joan de Déu, CIBERER - ISCIII, Barcelona, Spain
| | - Cecilia Jimenez-Mallebrera
- Neuromuscular Unit, Neuropaediatrics Department, Hospital Sant Joan de Déu, CIBERER - ISCIII, Barcelona, Spain
| | - Steven A Hardy
- Wellcome Centre for Mitochondrial Research, Newcastle University, Newcastle upon Tyne, UK
| | - Langping He
- Wellcome Centre for Mitochondrial Research, Newcastle University, Newcastle upon Tyne, UK
| | - Garry K Brown
- Oxford Medical Genetics Laboratories, Churchill Hospital, Oxford University Hospitals NHS Foundation Trust, Oxford, UK
| | - Paula Marttinen
- Institute of Biotechnology, University of Helsinki, Helsinki, Finland
| | - Robert McFarland
- Wellcome Centre for Mitochondrial Research, Newcastle University, Newcastle upon Tyne, UK
| | - Alberto Sanz
- Institute for Cell and Molecular Biosciences, Newcastle University Institute for Ageing, Newcastle University, Newcastle upon Tyne, UK
| | | | - Penelope E Bonnen
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA
| | - Michael T Ryan
- Department of Biochemistry and Molecular Biology, Monash Biomedicine Discovery Institute, Monash University, Melbourne, Vic., Australia
| | | | - Robert N Lightowlers
- Wellcome Centre for Mitochondrial Research, Newcastle University, Newcastle upon Tyne, UK
| | - Robert W Taylor
- Wellcome Centre for Mitochondrial Research, Newcastle University, Newcastle upon Tyne, UK
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14
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Richter U, Ng KY, Suomi F, Marttinen P, Turunen T, Jackson C, Suomalainen A, Vihinen H, Jokitalo E, Nyman TA, Isokallio MA, Stewart JB, Mancini C, Brusco A, Seneca S, Lombès A, Taylor RW, Battersby BJ. Mitochondrial stress response triggered by defects in protein synthesis quality control. Life Sci Alliance 2019; 2:2/1/e201800219. [PMID: 30683687 PMCID: PMC6348486 DOI: 10.26508/lsa.201800219] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2018] [Revised: 01/16/2019] [Accepted: 01/17/2019] [Indexed: 12/11/2022] Open
Abstract
Quality control defects of mitochondrial nascent chain synthesis trigger a sequential stress response characterized by OMA1 activation and ribosome decay, determining mitochondrial form and function. Mitochondria have a compartmentalized gene expression system dedicated to the synthesis of membrane proteins essential for oxidative phosphorylation. Responsive quality control mechanisms are needed to ensure that aberrant protein synthesis does not disrupt mitochondrial function. Pathogenic mutations that impede the function of the mitochondrial matrix quality control protease complex composed of AFG3L2 and paraplegin cause a multifaceted clinical syndrome. At the cell and molecular level, defects to this quality control complex are defined by impairment to mitochondrial form and function. Here, we establish the etiology of these phenotypes. We show how disruptions to the quality control of mitochondrial protein synthesis trigger a sequential stress response characterized first by OMA1 activation followed by loss of mitochondrial ribosomes and by remodelling of mitochondrial inner membrane ultrastructure. Inhibiting mitochondrial protein synthesis with chloramphenicol completely blocks this stress response. Together, our data establish a mechanism linking major cell biological phenotypes of AFG3L2 pathogenesis and show how modulation of mitochondrial protein synthesis can exert a beneficial effect on organelle homeostasis.
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Affiliation(s)
- Uwe Richter
- Institute of Biotechnology, University of Helsinki, Helsinki, Finland
| | - Kah Ying Ng
- Institute of Biotechnology, University of Helsinki, Helsinki, Finland
| | - Fumi Suomi
- Institute of Biotechnology, University of Helsinki, Helsinki, Finland
| | - Paula Marttinen
- Institute of Biotechnology, University of Helsinki, Helsinki, Finland
| | - Taina Turunen
- Institute of Biotechnology, University of Helsinki, Helsinki, Finland
| | - Christopher Jackson
- Research Programs Unit-Molecular Neurology, University of Helsinki, Helsinki, Finland
| | - Anu Suomalainen
- Research Programs Unit-Molecular Neurology, University of Helsinki, Helsinki, Finland
| | - Helena Vihinen
- Institute of Biotechnology, University of Helsinki, Helsinki, Finland
| | - Eija Jokitalo
- Institute of Biotechnology, University of Helsinki, Helsinki, Finland
| | - Tuula A Nyman
- Department of Immunology, Institute of Clinical Medicine, University of Oslo and Oslo University Hospital, Oslo, Norway
| | | | - James B Stewart
- Max Planck Institute for Biology of Ageing, Cologne, Germany
| | - Cecilia Mancini
- Department of Medical Sciences, University of Torino, Torino, Italy
| | - Alfredo Brusco
- Department of Medical Sciences, University of Torino, Torino, Italy
| | - Sara Seneca
- Center for Medical Genetics/Research Center Reproduction and Genetics, Universitair Ziekenhuis Brussel, Brussels, Belgium
| | - Anne Lombès
- Faculté de médecine Cochin, Institut Cochin Institut national de la santé et de la recherche médicale U1016, Centre national de la recherche scientifique Unités Mixtes de Recherche 8104, Université Paris 5, Paris, France
| | - Robert W Taylor
- Wellcome Centre for Mitochondrial Research, Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, UK
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15
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Mancini C, Hoxha E, Iommarini L, Brussino A, Richter U, Montarolo F, Cagnoli C, Parolisi R, Gondor Morosini DI, Nicolò V, Maltecca F, Muratori L, Ronchi G, Geuna S, Arnaboldi F, Donetti E, Giorgio E, Cavalieri S, Di Gregorio E, Pozzi E, Ferrero M, Riberi E, Casari G, Altruda F, Turco E, Gasparre G, Battersby BJ, Porcelli AM, Ferrero E, Brusco A, Tempia F. Mice harbouring a SCA28 patient mutation in AFG3L2 develop late-onset ataxia associated with enhanced mitochondrial proteotoxicity. Neurobiol Dis 2018; 124:14-28. [PMID: 30389403 DOI: 10.1016/j.nbd.2018.10.018] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2018] [Revised: 10/05/2018] [Accepted: 10/28/2018] [Indexed: 12/20/2022] Open
Abstract
Spinocerebellar ataxia 28 is an autosomal dominant neurodegenerative disorder caused by missense mutations affecting the proteolytic domain of AFG3L2, a major component of the mitochondrial m-AAA protease. However, little is known of the underlying pathogenetic mechanisms or how to treat patients with SCA28. Currently available Afg3l2 mutant mice harbour deletions that lead to severe, early-onset neurological phenotypes that do not faithfully reproduce the late-onset and slowly progressing SCA28 phenotype. Here we describe production and detailed analysis of a new knock-in murine model harbouring an Afg3l2 allele carrying the p.Met665Arg patient-derived mutation. Heterozygous mutant mice developed normally but adult mice showed signs of cerebellar ataxia detectable by beam test. Although cerebellar pathology was negative, electrophysiological analysis showed a trend towards increased spontaneous firing in Purkinje cells from heterozygous mutants with respect to wild-type controls. As homozygous mutants died perinatally with evidence of cardiac atrophy, for each genotype we generated mouse embryonic fibroblasts (MEFs) to investigate mitochondrial function. MEFs from mutant mice showed altered mitochondrial bioenergetics, with decreased basal oxygen consumption rate, ATP synthesis and mitochondrial membrane potential. Mitochondrial network formation and morphology was altered, with greatly reduced expression of fusogenic Opa1 isoforms. Mitochondrial alterations were also detected in cerebella of 18-month-old heterozygous mutants and may be a hallmark of disease. Pharmacological inhibition of de novo mitochondrial protein translation with chloramphenicol caused reversal of mitochondrial morphology in homozygous mutant MEFs, supporting the relevance of mitochondrial proteotoxicity for SCA28 pathogenesis and therapy development.
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Affiliation(s)
- Cecilia Mancini
- Department of Medical Sciences, University of Torino, Torino, Italy
| | - Eriola Hoxha
- Department of Neuroscience, University of Torino, Torino, Italy; Neuroscience Institute Cavalieri Ottolenghi (NICO), Orbassano, Italy
| | - Luisa Iommarini
- Department of Pharmacy and Biotechnologies (FABIT), University of Bologna, Bologna, Italy
| | | | - Uwe Richter
- Institute of Biotechnology, University of Helsinki, Helsinki, Finland
| | - Francesca Montarolo
- Department of Neuroscience, University of Torino, Torino, Italy; Neuroscience Institute Cavalieri Ottolenghi (NICO), Orbassano, Italy
| | - Claudia Cagnoli
- Department of Medical Sciences, University of Torino, Torino, Italy
| | - Roberta Parolisi
- Department of Neuroscience, University of Torino, Torino, Italy; Neuroscience Institute Cavalieri Ottolenghi (NICO), Orbassano, Italy
| | - Diana Iulia Gondor Morosini
- Department of Neuroscience, University of Torino, Torino, Italy; Neuroscience Institute Cavalieri Ottolenghi (NICO), Orbassano, Italy
| | - Valentina Nicolò
- Department of Neuroscience, University of Torino, Torino, Italy; Neuroscience Institute Cavalieri Ottolenghi (NICO), Orbassano, Italy
| | - Francesca Maltecca
- Università Vita-Salute San Raffaele, Division of Genetics and Cell Biology, San Raffaele Scientific Institute, Milan, Italy
| | - Luisa Muratori
- Neuroscience Institute Cavalieri Ottolenghi (NICO), Orbassano, Italy; Department of Clinical and Biological Sciences, University of Torino, Torino, Italy
| | - Giulia Ronchi
- Neuroscience Institute Cavalieri Ottolenghi (NICO), Orbassano, Italy; Department of Clinical and Biological Sciences, University of Torino, Torino, Italy
| | - Stefano Geuna
- Neuroscience Institute Cavalieri Ottolenghi (NICO), Orbassano, Italy; Department of Clinical and Biological Sciences, University of Torino, Torino, Italy
| | - Francesca Arnaboldi
- Department of Biomedical Sciences for Health, Università degli Studi di Milano, Milan, Italy
| | - Elena Donetti
- Department of Biomedical Sciences for Health, Università degli Studi di Milano, Milan, Italy
| | - Elisa Giorgio
- Department of Medical Sciences, University of Torino, Torino, Italy
| | - Simona Cavalieri
- Department of Medical Sciences, University of Torino, Torino, Italy
| | - Eleonora Di Gregorio
- Medical Genetics Unit, Città della Salute e della Scienza University Hospital, Torino, Italy
| | - Elisa Pozzi
- Department of Medical Sciences, University of Torino, Torino, Italy
| | - Marta Ferrero
- Department of Medical Sciences, University of Torino, Torino, Italy
| | - Evelise Riberi
- Department of Public Health and Pediatrics, University of Torino, Torino, Italy
| | - Giorgio Casari
- Università Vita-Salute San Raffaele, Division of Genetics and Cell Biology, San Raffaele Scientific Institute, Milan, Italy
| | - Fiorella Altruda
- Molecular Biotechnology Center, Department of Molecular Biotechnology and Health Sciences, University of Torino, Torino, Italy
| | - Emilia Turco
- Molecular Biotechnology Center, Department of Molecular Biotechnology and Health Sciences, University of Torino, Torino, Italy
| | - Giuseppe Gasparre
- Department Medical and Surgical Sciences, Medical Genetics, University of Bologna, Bologna, Italy
| | | | - Anna Maria Porcelli
- Department of Pharmacy and Biotechnologies (FABIT), University of Bologna, Bologna, Italy
| | - Enza Ferrero
- Department of Medical Sciences, University of Torino, Torino, Italy
| | - Alfredo Brusco
- Department of Medical Sciences, University of Torino, Torino, Italy; Medical Genetics Unit, Città della Salute e della Scienza University Hospital, Torino, Italy.
| | - Filippo Tempia
- Department of Neuroscience, University of Torino, Torino, Italy; Neuroscience Institute Cavalieri Ottolenghi (NICO), Orbassano, Italy
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16
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Jackson CB, Hahn D, Schröter B, Richter U, Battersby BJ, Schmitt-Mechelke T, Marttinen P, Nuoffer JM, Schaller A. A novel mitochondrial ATP6 frameshift mutation causing isolated complex V deficiency, ataxia and encephalomyopathy. Eur J Med Genet 2017; 60:345-351. [PMID: 28412374 DOI: 10.1016/j.ejmg.2017.04.006] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2016] [Revised: 04/03/2017] [Accepted: 04/10/2017] [Indexed: 12/15/2022]
Abstract
We describe a novel frameshift mutation in the mitochondrial ATP6 gene in a 4-year-old girl associated with ataxia, microcephaly, developmental delay and intellectual disability. A heteroplasmic frameshift mutation in the MT-ATP6 gene was confirmed in the patient's skeletal muscle and blood. The mutation was not detectable in the mother's DNA extracted from blood or buccal cells. Enzymatic and oxymetric analysis of the mitochondrial respiratory system in the patients' skeletal muscle and skin fibroblasts demonstrated an isolated complex V deficiency. Native PAGE with subsequent immunoblotting for complex V revealed impaired complex V assembly and accumulation of ATPase subcomplexes. Whilst northern blotting confirmed equal presence of ATP8/6 mRNA, metabolic 35S-labelling of mitochondrial translation products showed a severe depletion of the ATP6 protein together with aberrant translation product accumulation. In conclusion, this novel isolated complex V defect expands the clinical and genetic spectrum of mitochondrial defects of complex V deficiency. Furthermore, this work confirms the benefit of native PAGE as an additional diagnostic method for the identification of OXPHOS defects, as the presence of complex V subcomplexes is associated with pathogenic mutations of mtDNA.
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Affiliation(s)
- Christopher B Jackson
- Institute of Clinical Chemistry, University Hospital Bern, Switzerland; Research Programs for Molecular Neurology, Biomedicum Helsinki, University of Helsinki, Finland.
| | - Dagmar Hahn
- Institute of Clinical Chemistry, University Hospital Bern, Switzerland
| | - Barbara Schröter
- Department of Neuropaediatrics, Children's Hospital, Cantonal Hospital Lucerne, Switzerland.
| | - Uwe Richter
- Institute of Biotechnology, University of Helsinki, Finland.
| | | | - Thomas Schmitt-Mechelke
- Department of Neuropaediatrics, Children's Hospital, Cantonal Hospital Lucerne, Switzerland.
| | - Paula Marttinen
- Institute of Biotechnology, University of Helsinki, Finland.
| | - Jean-Marc Nuoffer
- Institute of Clinical Chemistry, University Hospital Bern, Switzerland.
| | - André Schaller
- Division of Human Genetics, Bern, University Hospital Bern, Switzerland.
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17
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Richter U, Lahtinen T, Marttinen P, Suomi F, Battersby BJ. Quality control of mitochondrial protein synthesis is required for membrane integrity and cell fitness. J Cell Biol 2016; 211:373-89. [PMID: 26504172 PMCID: PMC4621829 DOI: 10.1083/jcb.201504062] [Citation(s) in RCA: 82] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Impaired turnover of newly synthesized mitochondrial proteins of the oxidative phosphorylation complexes leads to protein over-accumulation in the inner mitochondrial membrane, thereby generating a stress that dissipates the mitochondrial membrane potential and therefore compromises organelle and cellular fitness. Mitochondrial ribosomes synthesize a subset of hydrophobic proteins required for assembly of the oxidative phosphorylation complexes. This process requires temporal and spatial coordination and regulation, so quality control of mitochondrial protein synthesis is paramount to maintain proteostasis. We show how impaired turnover of de novo mitochondrial proteins leads to aberrant protein accumulation in the mitochondrial inner membrane. This creates a stress in the inner membrane that progressively dissipates the mitochondrial membrane potential, which in turn stalls mitochondrial protein synthesis and fragments the mitochondrial network. The mitochondrial m-AAA protease subunit AFG3L2 is critical to this surveillance mechanism that we propose acts as a sensor to couple the synthesis of mitochondrial proteins with organelle fitness, thus ensuring coordinated assembly of the oxidative phosphorylation complexes from two sets of ribosomes.
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Affiliation(s)
- Uwe Richter
- Research Programs for Molecular Neurology, Biomedicum Helsinki, University of Helsinki, 00290 Helsinki, Finland
| | - Taina Lahtinen
- Research Programs for Molecular Neurology, Biomedicum Helsinki, University of Helsinki, 00290 Helsinki, Finland
| | - Paula Marttinen
- Research Programs for Molecular Neurology, Biomedicum Helsinki, University of Helsinki, 00290 Helsinki, Finland
| | - Fumi Suomi
- Research Programs for Molecular Neurology, Biomedicum Helsinki, University of Helsinki, 00290 Helsinki, Finland
| | - Brendan J Battersby
- Research Programs for Molecular Neurology, Biomedicum Helsinki, University of Helsinki, 00290 Helsinki, Finland
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18
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Jokinen R, Marttinen P, Stewart JB, Neil Dear T, Battersby BJ. Tissue-specific modulation of mitochondrial DNA segregation by a defect in mitochondrial division. Hum Mol Genet 2015; 25:706-14. [PMID: 26681804 DOI: 10.1093/hmg/ddv508] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2015] [Accepted: 12/08/2015] [Indexed: 01/19/2023] Open
Abstract
Mitochondria are dynamic organelles that divide and fuse by remodeling an outer and inner membrane in response to developmental, physiological and stress stimuli. These events are coordinated by conserved dynamin-related GTPases. The dynamics of mitochondrial morphology require coordination with mitochondrial DNA (mtDNA) to ensure faithful genome transmission, however, this process remains poorly understood. Mitochondrial division is linked to the segregation of mtDNA but how it affects cases of mtDNA heteroplasmy, where two or more mtDNA variants/mutations co-exist in a cell, is unknown. Segregation of heteroplasmic human pathogenic mtDNA mutations is a critical factor in the onset and severity of human mitochondrial diseases. Here, we investigated the coupling of mitochondrial morphology to the transmission and segregation of mtDNA in mammals by taking advantage of two genetically modified mouse models: one with a dominant-negative mutation in the dynamin-related protein 1 (Drp1 or Dnm1l) that impairs mitochondrial fission and the other, heteroplasmic mice segregating two neutral mtDNA haplotypes (BALB and NZB). We show a tissue-specific response to mtDNA segregation from a defect in mitochondrial fission. Only mtDNA segregation in the hematopoietic compartment is modulated from impaired Dnm1l function. In contrast, no effect was observed in other tissues arising from the three germ layers during development and in mtDNA transmission through the female germline. Our data suggest a robust organization of a heteroplasmic mtDNA segregating unit across mammalian cell types that can overcome impaired mitochondrial division to ensure faithful transmission of the mitochondrial genome.
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Affiliation(s)
- Riikka Jokinen
- Research Programs Unit - Molecular Neurology, University of Helsinki, Helsinki, Finland
| | - Paula Marttinen
- Research Programs Unit - Molecular Neurology, University of Helsinki, Helsinki, Finland
| | - James B Stewart
- Max Planck Institute for Biology of Ageing, Cologne, Germany and
| | - T Neil Dear
- South Australian Health and Medical Research Institute, Adelaide, Australia
| | - Brendan J Battersby
- Research Programs Unit - Molecular Neurology, University of Helsinki, Helsinki, Finland,
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19
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Jokinen R, Junnila H, Battersby BJ. Gimap3: A foot-in-the-door to tissue-specific regulation of mitochondrial DNA genetics. Small GTPases 2014; 2:31-35. [PMID: 21686279 DOI: 10.4161/sgtp.2.1.14937] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2010] [Revised: 01/18/2011] [Accepted: 01/23/2011] [Indexed: 01/31/2023] Open
Abstract
Mitochondrial DNA (mtDNA) is a multi-copy genome encoding for proteins essential for aerobic energy metabolism. Mutations in mtDNA can lead to a variety of human diseases, from mild metabolic syndromes to severe fatal encephalomyopathies. Most mtDNA mutations co-exist with wild type genomes in a state known as heteroplasmy. The segregation of these pathogenic mutants is tissue and mutation specific, and a key determinant in the onset and severity of human mitochondrial disorders. We used a forward genetic approach in mice to identify and demonstrate that Gimap3 (GTP ase of immunity associated protein) is a key regulator of mtDNA segregation in leukocytes. The Gimap gene cluster is found only in vertebrates and appear to be a class of nucleotide-dependent dimerization GTP ases. Gimap3 is a membrane-anchored GTP ase with a critical role in T cell development. Here, we summarize our genetic findings and postulate how Gimap3 might regulate mtDNA genetics.
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Affiliation(s)
- Riikka Jokinen
- Research Program of Molecular Neurology and Institute of Biomedicine; Biomedicum Helsinki; University of Helsinki; Helsinki, Finland
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20
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Hagström E, Freyer C, Battersby BJ, Stewart JB, Larsson NG. No recombination of mtDNA after heteroplasmy for 50 generations in the mouse maternal germline. Nucleic Acids Res 2013; 42:1111-6. [PMID: 24163253 PMCID: PMC3902947 DOI: 10.1093/nar/gkt969] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Variants of mitochondrial DNA (mtDNA) are commonly used as markers to track human evolution because of the high sequence divergence and exclusive maternal inheritance. It is assumed that the inheritance is clonal, i.e. that mtDNA is transmitted between generations without germline recombination. In contrast to this assumption, a number of studies have reported the presence of recombinant mtDNA molecules in cell lines and animal tissues, including humans. If germline recombination of mtDNA is frequent, it would strongly impact phylogenetic and population studies by altering estimates of coalescent time and branch lengths in phylogenetic trees. Unfortunately, this whole area is controversial and the experimental approaches have been widely criticized as they often depend on polymerase chain reaction (PCR) amplification of mtDNA and/or involve studies of transformed cell lines. In this study, we used an in vivo mouse model that has had germline heteroplasmy for a defined set of mtDNA mutations for more than 50 generations. To assess recombination, we adapted and validated a method based on cloning of single mtDNA molecules in the λ phage, without prior PCR amplification, followed by subsequent mutation analysis. We screened 2922 mtDNA molecules and found no germline recombination after transmission of mtDNA under genetically and evolutionary relevant conditions in mammals.
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Affiliation(s)
- Erik Hagström
- Department of Laboratory Medicine, Karolinska Institutet, S-17177 Stockholm, Sweden, Research Programs Unit - Molecular Neurology, Biomedicum Helsinki, University of Helsinki, 00290 Finland and Max Planck Institute for Biology of Ageing, D-50931 Cologne, Germany
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21
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Abstract
Mitochondrial DNA (mtDNA) is essential for aerobic energy production in eukaryotic cells, and mutations in this genome can lead to mitochondrial dysfunction. Human mtDNA mutations are typically heteroplasmic, a mix of mutant and wild-type genomes, which can present as a heterogeneous group of disorders ranging in severity from mild to fatal, and commonly affecting highly aerobic tissues such as heart, skeletal muscle, and neurons. During the 1990s, many research groups started to notice that mtDNA mutations could segregate depending upon the mutation and tissue. This segregation pattern can have a direct effect on the onset and severity of these mutations. However, these segregation patterns could not be easily explained by respiratory chain function, implying that there is regulation of mtDNA independent of its bioenergetic role. A lot of research on this topic has been largely descriptive, but over the last several years advances in mitochondrial biology have provided some mechanistic insight into the regulation of the organelle and its genome. This review addresses these advances with respect to somatic segregation of mtDNA in mammals.
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Affiliation(s)
- Riikka Jokinen
- Research Programs Unit-Molecular Neurology, and Institute of Biomedicine, Biomedicum Helsinki, University of Helsinki, Helsinki, Finland
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22
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Carroll CJ, Isohanni P, Pöyhönen R, Euro L, Richter U, Brilhante V, Götz A, Lahtinen T, Paetau A, Pihko H, Battersby BJ, Tyynismaa H, Suomalainen A. Whole-exome sequencing identifies a mutation in the mitochondrial ribosome protein MRPL44 to underlie mitochondrial infantile cardiomyopathy. J Med Genet 2013; 50:151-9. [PMID: 23315540 DOI: 10.1136/jmedgenet-2012-101375] [Citation(s) in RCA: 71] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
BACKGROUND The genetic complexity of infantile cardiomyopathies is remarkable, and the importance of mitochondrial translation defects as a causative factor is only starting to be recognised. We investigated the genetic basis for infantile onset recessive hypertrophic cardiomyopathy in two siblings. METHODS AND RESULTS Analysis of respiratory chain enzymes revealed a combined deficiency of complexes I and IV in the heart and skeletal muscle. Exome sequencing uncovered a homozygous mutation (L156R) in MRPL44 of both siblings. MRPL44 encodes a protein in the large subunit of the mitochondrial ribosome and is suggested to locate in close proximity to the tunnel exit of the yeast mitochondrial ribosome. We found severely reduced MRPL44 levels in the patient's heart, skeletal muscle and fibroblasts suggesting that the missense mutation affected the protein stability. In patient fibroblasts, decreased MRPL44 affected assembly of the large ribosomal subunit and stability of 16S rRNA leading to complex IV deficiency. Despite this assembly defect, de novo mitochondrial translation was only mildly affected in fibroblasts suggesting that MRPL44 may have a function in the assembly/stability of nascent mitochondrial polypeptides exiting the ribosome. Retroviral expression of wild-type MRPL44 in patient fibroblasts rescued the large ribosome assembly defect and COX deficiency. CONCLUSIONS These findings indicate that mitochondrial ribosomal subunit defects can generate tissue-specific manifestations, such as cardiomyopathy.
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Affiliation(s)
- Christopher J Carroll
- Research Programs Unit, Molecular Neurology, Biomedicum-Helsinki, University of Helsinki, r.C523B, Haartmaninkatu 8, Helsinki 00290, Finland.
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23
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Battersby BJ, Richter U. Why translation counts for mitochondria – retrograde signalling links mitochondrial protein synthesis to mitochondrial biogenesis and cell proliferation. J Cell Sci 2013; 126:4331-8. [DOI: 10.1242/jcs.131888] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Organelle biosynthesis is a key requirement for cell growth and division. The regulation of mitochondrial biosynthesis exhibits additional layers of complexity compared with that of other organelles because they contain their own genome and dedicated ribosomes. Maintaining these components requires gene expression to be coordinated between the nucleo-cytoplasmic compartment and mitochondria in order to monitor organelle homeostasis and to integrate the responses to the physiological and developmental demands of the cell. Surprisingly, the parameters that are used to monitor or count mitochondrial abundance are not known, nor are the signalling pathways. Inhibiting the translation on mito-ribosomes genetically or with antibiotics can impair cell proliferation and has been attributed to defects in aerobic energy metabolism, even though proliferating cells rely primarily on glycolysis to fuel their metabolic demands. However, a recent study indicates that mitochondrial translational stress and the rescue mechanisms that relieve this stress cause the defect in cell proliferation and occur before any impairment of oxidative phosphorylation. Therefore, the process of mitochondrial translation in itself appears to be an important checkpoint for the monitoring of mitochondrial homeostasis and might have a role in establishing mitochondrial abundance within a cell. This hypothesis article will explore the evidence supporting a role for mito-ribosomes and translation in a mitochondria-counting mechanism.
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Jokinen⁎ R, Marttinen P, Sandell K, Manninen T, Teerenhovi H, Wai T, Teoli D, Loredo-Osti J, Shoubridge EA, Battersby BJ. Cloning a novel mitochondrial protein which regulates tissue-specific mtDNA segregation. Mitochondrion 2011. [DOI: 10.1016/j.mito.2011.03.023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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25
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Jokinen R, Marttinen P, Sandell HK, Manninen T, Teerenhovi H, Wai T, Teoli D, Loredo-Osti JC, Shoubridge EA, Battersby BJ. Gimap3 regulates tissue-specific mitochondrial DNA segregation. PLoS Genet 2010; 6:e1001161. [PMID: 20976251 PMCID: PMC2954831 DOI: 10.1371/journal.pgen.1001161] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2010] [Accepted: 09/15/2010] [Indexed: 12/20/2022] Open
Abstract
Mitochondrial DNA (mtDNA) sequence variants segregate in mutation and tissue-specific manners, but the mechanisms remain unknown. The segregation pattern of pathogenic mtDNA mutations is a major determinant of the onset and severity of disease. Using a heteroplasmic mouse model, we demonstrate that Gimap3, an outer mitochondrial membrane GTPase, is a critical regulator of this process in leukocytes. Gimap3 is important for T cell development and survival, suggesting that leukocyte survival may be a key factor in the genetic regulation of mtDNA sequence variants and in modulating human mitochondrial diseases.
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Affiliation(s)
- Riikka Jokinen
- Research Program of Molecular Neurology and Institute of Biomedicine, Biomedicum Helsinki, University of Helsinki, Helsinki, Finland
| | - Paula Marttinen
- Research Program of Molecular Neurology and Institute of Biomedicine, Biomedicum Helsinki, University of Helsinki, Helsinki, Finland
| | - Helen Katarin Sandell
- Research Program of Molecular Neurology and Institute of Biomedicine, Biomedicum Helsinki, University of Helsinki, Helsinki, Finland
| | - Tuula Manninen
- Research Program of Molecular Neurology and Institute of Biomedicine, Biomedicum Helsinki, University of Helsinki, Helsinki, Finland
| | - Heli Teerenhovi
- Research Program of Molecular Neurology and Institute of Biomedicine, Biomedicum Helsinki, University of Helsinki, Helsinki, Finland
| | - Timothy Wai
- Montreal Neurological Institute and Department of Human Genetics, McGill University, Montreal, Quebec, Canada
| | - Daniella Teoli
- Montreal Neurological Institute and Department of Human Genetics, McGill University, Montreal, Quebec, Canada
| | - J. C. Loredo-Osti
- Department of Mathematics and Statistics, Memorial University, St. John's, Newfoundland, Canada
| | - Eric A. Shoubridge
- Montreal Neurological Institute and Department of Human Genetics, McGill University, Montreal, Quebec, Canada
| | - Brendan J. Battersby
- Research Program of Molecular Neurology and Institute of Biomedicine, Biomedicum Helsinki, University of Helsinki, Helsinki, Finland
- * E-mail:
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26
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Battersby BJ. 86 Tissue-specific control of mitochondrial DNA genetics. Mitochondrion 2010. [DOI: 10.1016/j.mito.2009.12.080] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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27
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28
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Bacman SR, Williams SL, Hernandez D, Battersby BJ, Shoubridge EA, Moraes CT. Manipulating heteroplasmy by delivering restriction endonuclease to mitochondria in a “differential multiple cleavage-site” model. Mitochondrion 2006. [DOI: 10.1016/j.mito.2006.08.036] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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29
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Bayona-Bafaluy MP, Blits B, Battersby BJ, Shoubridge EA, Moraes CT. Rapid directional shift of mitochondrial DNA heteroplasmy in animal tissues by a mitochondrially targeted restriction endonuclease. Proc Natl Acad Sci U S A 2005; 102:14392-7. [PMID: 16179392 PMCID: PMC1242285 DOI: 10.1073/pnas.0502896102] [Citation(s) in RCA: 120] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Frequently, mtDNA with pathogenic mutations coexist with wild-type genomes (mtDNA heteroplasmy). Mitochondrial dysfunction and disease ensue only when the proportion of mutated mtDNAs is high, thus a reduction in this proportion should provide an effective therapy for these disorders. We developed a system to decrease specific mtDNA haplotypes by expressing a mitochondrially targeted restriction endonuclease, ApaLI, in cells of heteroplasmic mice. These mice have two mtDNA haplotypes, of which only one contains an ApaLI site. After transfection of cultured hepatocytes with mitochondrially targeted ApaLI, we found a rapid, directional, and complete shift in mtDNA heteroplasmy (2-6 h). We tested the efficacy of this approach in vivo, by using recombinant viral vectors expressing the mitochondrially targeted ApaLI. We observed a significant shift in mtDNA heteroplasmy in muscle and brain transduced with recombinant viruses. This strategy could prevent disease onset or reverse clinical symptoms in patients harboring certain heteroplasmic pathogenic mutations in mtDNA.
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Affiliation(s)
- Maria Pilar Bayona-Bafaluy
- Department of Neurology and Cell Biologyalysis, University of Miami Miller School of Medicine, Miami, FL 33136, USA
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30
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Battersby BJ, Redpath ME, Shoubridge EA. Mitochondrial DNA segregation in hematopoietic lineages does not depend on MHC presentation of mitochondrially encoded peptides. Hum Mol Genet 2005; 14:2587-94. [PMID: 16049030 DOI: 10.1093/hmg/ddi293] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Mutations in mitochondrial DNA (mtDNA) are associated with a broad spectrum of clinical disorders. The segregation pattern of pathogenic mtDNAs is an important determinant of both the onset and the severity of the disease phenotype, but the mechanisms controlling mtDNA segregation remain poorly understood. To investigate this, we previously generated heteroplasmic mice containing two different mtDNA haplotypes and showed that BALB/c mtDNA was invariably selected over NZB mtDNA in blood and spleen. Here, we have characterized this process in hematopoietic tissues and tested whether it involves the presentation of mtDNA-encoded peptides by MHC class Ib molecules. Selection against NZB mtDNA was widespread across different hematopoietic cell lineages and proportional to heteroplasmy levels. Backcrossing heteroplasmic mice with CAST/Ei, a strain in which the MHC class Ib molecule H2-M3 is silent, completely abolished selection against NZB mtDNA in the spleen. To test whether this effect depended on an intact immune system, we generated heteroplasmic mice missing functional copies of Tap1, beta2m or Rag1 to impair presentation or recognition of mtDNA-encoded peptides. The kinetics of selection against NZB mtDNA were unaltered in these mice compared with their wild-type littermates. We conclude that mtDNA selection in hematopoietic tissues is not based on an immune mechanism, but likely involves metabolic signaling.
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Affiliation(s)
- Brendan J Battersby
- Department of Human Genetics, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada
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31
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Dean NL, Battersby BJ, Ao A, Gosden RG, Tan SL, Shoubridge EA, Molnar MJ. Prospect of preimplantation genetic diagnosis for heritable mitochondrial DNA diseases. Mol Hum Reprod 2003; 9:631-8. [PMID: 12970401 DOI: 10.1093/molehr/gag077] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
To perform preimplantation genetic diagnosis for women carrying heteroplasmic mitochondrial DNA (mtDNA) mutations, it is necessary to ensure that the proportion of mutant mtDNA diagnosed in the biopsied cell gives an accurate indication of the mutant load in the remaining embryo. A heteroplasmic mouse model, carrying NZB and BALB mtDNA genotypes, was used to study the relative proportions of each mtDNA genotype in the ooplasm and first polar body of mature oocytes, and between blastomeres of early cleavage stage embryos. The levels of heteroplasmy varied widely in the gametes compared with the maternal genotype. However, the distribution of the two mtDNA genotypes was virtually identical between the ooplasm and polar body of a mature oocyte, and also between the blastomeres of each 2-, 4- and 6-8-cell embryo. Therefore, the level of heteroplasmy diagnosed from the polar body of an unfertilized oocyte or from a single blastomere of an embryo is representative of the level in the embryo as a whole. Reliable results were obtained from both polar bodies and blastomeres, but the efficiency of diagnosis was greater with blastomeres. We conclude that preimplantation genetic diagnosis is feasible for mtDNA diseases, although it should be approached with caution, as it is possible that transmission of some pathogenic mutations could behave in a different manner.
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Affiliation(s)
- Nicola L Dean
- Department of Obstetrics and Gynecology, Royal Victoria Hospital, Montreal, H3A 1A1, Quebec, Canada
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32
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Battersby BJ, Loredo-Osti JC, Shoubridge EA. Nuclear genetic control of mitochondrial DNA segregation. Nat Genet 2003; 33:183-6. [PMID: 12539044 DOI: 10.1038/ng1073] [Citation(s) in RCA: 110] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2002] [Accepted: 12/04/2002] [Indexed: 11/09/2022]
Abstract
Mammalian mitochondrial DNA (mtDNA) is a high copy-number, maternally inherited genome that codes for a small number of essential proteins involved in oxidative phosphorylation. Mutations in mtDNA are responsible for a broad spectrum of clinical disorders. The segregation pattern of pathogenic mtDNA mutants is an important determinant of the nature and severity of mitochondrial disease, but it varies with the specific mutation, cell type and nuclear background and generally does not correlate well with mitochondrial dysfunction. To identify nuclear genes that modify the segregation behavior of mtDNA, we used a heteroplasmic mouse model derived from two inbred strains (BALB/c and NZB; ref. 12), in which we had previously demonstrated tissue-specific and age-dependent directional selection for different mtDNA genotypes in the same mouse. Here we show that this phenotype segregates in F2 mice from a genetic cross (BALB/c x CAST/Ei) and that it maps to at least three quantitative-trait loci (QTLs). Genome-wide scans showed linkage of the trait to loci on Chromosomes 2, 5 and 6, accounting for 16-35% of the variance in the trait, depending on the tissue and age of the mouse. This is the first genetic evidence for nuclear control of mammalian mtDNA segregation.
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Affiliation(s)
- Brendan J Battersby
- Montreal Neurological Institute and Department of Human Genetics, McGill University, 3801 University Street, Montreal, Quebec H3A 2B4, Canada
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33
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Battersby BJ, Shoubridge EA. Selection of a mtDNA sequence variant in hepatocytes of heteroplasmic mice is not due to differences in respiratory chain function or efficiency of replication. Hum Mol Genet 2001; 10:2469-79. [PMID: 11709534 DOI: 10.1093/hmg/10.22.2469] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
We have previously constructed lines of heteroplasmic mice from two inbred strains (NZB/BinJ and BALB/c) to investigate the mechanisms of segregation of mtDNA sequence variants. Analysis of the segregation behaviour of mtDNA in several tissues showed that the NZB genotype was invariably selected in liver/kidney and the BALB genotype in blood/spleen. Segregation was not significant in post-mitotic tissues. Here we have investigated this novel pattern of mtDNA segregation in isolated hepatocytes to determine the mechanism of selection. Polarographic measurements of respiratory chain function showed no difference between mitochondria containing either 0 or 91-97% NZB mtDNAs on a BALB nuclear background. Single-cell PCR analysis of mtDNA in isolated hepatocytes demonstrated that most hepatocytes eventually fix the NZB genotype. The rate of selection was constant with time and independent of the initial genotype frequency. Based on a mtDNA replication rate of 9.4 days, NZB mtDNA has an approximately 14% selective advantage over BALB mtDNA; however, in vivo pulse labelling with BrdU demonstrated that this was not based on efficiency of replication. Surprisingly, when hepatocytes were cultured in vitro, the majority of independent colonies selected BALB mtDNA, even if they were nearly fixed for the NZB mtDNA genotype when initially plated. These data suggest that selection for NZB mtDNA in the liver of these mice is not based on respiratory chain function at the cellular or organellar level, or a simple replicative advantage, but on a factor(s) involved with mtDNA maintenance.
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Affiliation(s)
- B J Battersby
- Montreal Neurological Institute and Department of Human Genetics, McGill University, Montreal, Quebec, Canada
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34
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LeBlanc PJ, Obbard M, Battersby BJ, Felskie AK, Brown L, Wright PA, Ballantyne JS. Correlations of plasma lipid metabolites with hibernation and lactation in wild black bears Ursus americanus. J Comp Physiol B 2001; 171:327-34. [PMID: 11409630 DOI: 10.1007/s003600100180] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
During the denning period, black bears (Ursus americanus) are capable of enduring several months without food. At the same time, female bears that are pregnant or lactating have an added metabolic stress. Based on laboratory studies, much of the energy required to support metabolism and lactation during denning in black bears comes from lipid reserves. These lipid reserves are mobilized and the most metabolically active lipid fraction in the blood are nonesterified fatty acids (NEFA). Therefore, we hypothesized that plasma NEFAs would be higher in denning relative to active bears and in lactating relative to non-lactating female bears. We further hypothesized that in bears with elevated plasma NEFA levels, other lipid-related parameters (e.g., ketone bodies, albumin, cholesterol, lipase) would also be elevated in the plasma. Denning bears had significantly increased NEFA levels in all classes (saturates, monoenes, and polyenes). A doubling of plasma NEFA levels and a 33% increase in albumin, the plasma fatty acid binding protein, in denning bears, resulted in NEFA/albumin ratios that were higher in denning bears (4:1) compared to those of active bears (3:1). Bears became relatively ketonemic with a 17-fold increase in D-beta-hydroxybutyrate levels during the denning period. Plasma cholesterol approximately doubled and lipase was ten-fold lower in denning relative to active bears. These findings indicate a strong correlation between plasma lipid metabolites and the denning period in a wild population of black bears.
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Affiliation(s)
- P J LeBlanc
- Department of Zoology, University of Guelph, Ontario, Canada
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35
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Wright PA, Obbard ME, Battersby BJ, Felskie AK, LeBlanc PJ, Ballantyne JS. Lactation during hibernation in wild black bears: effects on plasma amino acids and nitrogen metabolites. Physiol Biochem Zool 1999; 72:597-604. [PMID: 10521327 DOI: 10.1086/316691] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
This study examined the seasonal and reproductive influences on individual plasma amino acid concentrations and nitrogen metabolites in a black bear population (Ontario, Canada). During hibernation, 11 of 23 plasma amino acids were significantly higher (13%-108%) in lactating than in nonlactating females, without an alteration in plasma total protein or total essential or nonessential amino acid levels. The greatest changes were observed in glutamine, arginine, and glycine levels. Plasma urea, urea/creatinine, and ammonia levels were significantly lower in hibernating compared with active female bears, but lactation had no effect on these parameters. Taken together these results show that lactation during hibernation is an additional metabolic challenge that results in increased mobilization of individual plasma amino acids and no accumulation of nitrogen end products, underlining the remarkable efficiency of amino acid and urea recycling in denning female black bears.
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Affiliation(s)
- P A Wright
- Department of Zoology, University of Guelph, Guelph, Ontario N1G 2W1, Canada.
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36
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Huebner S, Battersby BJ, Grimm R, Cevc G. Lipid-DNA complex formation: reorganization and rupture of lipid vesicles in the presence of DNA as observed by cryoelectron microscopy. Biophys J 1999; 76:3158-66. [PMID: 10354440 PMCID: PMC1300284 DOI: 10.1016/s0006-3495(99)77467-9] [Citation(s) in RCA: 176] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
Abstract
Cryoelectron microscopy has been used to study the reorganization of unilamellar cationic lipid vesicles upon the addition of DNA. Unilamellar DNA-coated vesicles, as well as multilamellar DNA lipid complexes, could be observed. Also, DNA induced fusion of unilamellar vesicles was found. DNA appears to adsorb to the oppositely charged lipid bilayer in a monolayer of parallel helices and can act as a molecular "glue" enforcing close apposition of neighboring vesicle membranes. In samples with relatively high DNA content, there is evidence for DNA-induced aggregation and flattening of unilamellar vesicles. In these samples, multilamellar complexes are rare and contain only a small number of lamellae. At lower DNA contents, large multilamellar CL-DNA complexes, often with >10 bilayers, are formed. The multilamellar complexes in both types of sample frequently exhibit partially open bilayer segments on their outside surfaces. DNA seems to accumulate or coil near the edges of such unusually terminated membranes. Multilamellar lipid-DNA complexes appear to form by a mechanism that involves the rupture of an approaching vesicle and subsequent adsorption of its membrane to a "template" vesicle or a lipid-DNA complex.
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Affiliation(s)
- S Huebner
- Medizinische Biophysik, Technische Universität München, D-81675 München, Germany.
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37
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Leary SC, Battersby BJ, Moyes CD. Inter-tissue differences in mitochondrial enzyme activity, RNA and DNA in rainbow trout (Oncorhynchus mykiss). J Exp Biol 1998; 201 (Pt 24):3377-84. [PMID: 9817834 DOI: 10.1242/jeb.201.24.3377] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
We examined whether the relationships between mitochondrial enzyme activity, mitochondrial DNA (mtDNA) and mitochondrial RNA (mtRNA) were conserved in rainbow trout (Oncorhynchus mykiss) tissues that differ widely in their metabolic and molecular organization. The activity of citrate synthase (CS), expressed either per gram of tissue or per milligram of total DNA, indicated that these tissues (blood, brain, kidney, liver,cardiac, red and white muscles) varied more than 100-fold in mitochondrial content. Several-fold differences in the levels of CS mRNA per milligram of DNA and CS activity per CS mRNA were also observed, suggesting that fundamental differences exist in the regulation of CS levels across tissues. Although tissues varied 14-fold in RNA g-1, poly(A+) RNA (mRNA)was approximately 2 % of total RNA in all tissues. DNA g-1 also varied 14-fold across tissues, but RNA:DNA ratios varied only 2.5-fold. The relationship between two mitochondrial mRNA species (COX I, ATPase VI) and one mitochondrial rRNA (16S) species was constant across tissues. The ratio of mtRNA to mtDNA was also preserved across most tissues; red and white muscle had 10- to 20-fold lower levels of mtDNA g-1 but 7- to 10-fold higher mtRNA:mtDNA ratios, respectively. Collectively, these data suggest that the relationship between mitochondrial parameters is highly conserved across most tissues, but that skeletal muscles differ in a number of important aspects of respiratory gene expression ('respiratory genes'include genes located on mtDNA and genes located in the nucleus that encode mitochondrial protein) and mtDNA transcriptional regulation.
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Affiliation(s)
- SC Leary
- Department of Biology, Queen's University, Kingston, Ontario, Canada K7L 3N6.
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Abstract
Skeletal muscle fibers typically undergo modifications in their mitochondrial content, concomitant with alterations in oxidative metabolism that occur during the development of muscle fiber and in response to physiological stimuli. We examined how cold acclimation affects the mitochondrial properties of two fish skeletal muscle fiber types and how the regulators of mitochondrial content differed between tissues. After 2 mo of acclimation to either 4 or 18 degrees C, mitochondrial enzyme activities in both red and white muscle were higher in cold-acclimated fish. No significant differences were detected between acclimation temperatures in the abundance of steady-state mitochondrial mRNA (cytochrome-c oxidase 1, subunit 6 of F0F1-ATPase), rRNA (16S), or DNA copy number. Steady-state mRNA for nuclear-encoded respiratory (adenine nucleotide translocase 1) and glycolytic genes showed high interindividual variability, particularly in the cold-acclimated fish. Although mitochondrial enzymes were 10-fold different between the two muscle types, mitochondrial DNA copy number differed only 4-fold. The relative abundance of mitochondrial mRNA and nuclear mRNA in red and white muscle reflected the differences in copy number of their respective genes. These data suggest that the response to physiological stimuli and determination of tissue-specific mitochondrial properties likely result from the regulation of nuclear-encoded genes.
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Affiliation(s)
- B J Battersby
- Department of Biology, Queen's University, Kingston, Ontario, Canada K7L 3N6
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Abstract
Ultrastructural analysis typically shows vertebrate striated muscles to possess mitochondria residing primarily in two locations. One population is interlaced throughout the myofibrils and another occurs directly beneath the cell membrane. The two populations of mitochondria can be separated and studied in vitro. Subsarcolemmal mitochondria (SSmt) are released by mechanical shearing of the tissue, whereas protease treatment is required to release the intermyofibrillar population (IMFmt). These methods were applied to rainbow trout (Oncorhynchus mykiss) red muscle to investigate the possible existence of distinct populations in this tissue. The two populations were very similar in mitochondrial DNA content (mtDNA mg-1 mitochondrial protein) and enzymatically (activities of carnitine palmitoyl transferase, &bgr ;-hydroxyacyl CoA dehydrogenase, complex I, citrate synthase, cytochrome c oxidase expressed per milligram of mitochondrial protein). Respiration rates were the same for pyruvate and succinate, but IMFmt oxidized palmitoyl carnitine 26 % faster than SSmt (P<0.05). Apart from these minor differences in fatty acyl carnitine oxidation rates, no differences in biochemical or genetic properties were detected between populations. The lack of distinct subcellular populations in fish, in contrast to the situation in mammalian striated muscle, probably relates to the high mitochondrial volume density in fish red muscle.
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Affiliation(s)
- BJ Battersby
- Department of Biology, Queen's University, Kingston, Ontario, Canada K7L 3N6.
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Abstract
We studied the interaction between energy metabolism and mitochondrial biogenesis during myogenesis in C2C12 myoblasts. Metabolic rate was nearly constant throughout differentiation, although there was a shift in the relative importance of glycolytic and oxidative metabolism, accompanied by increases in pyruvate dehydrogenase activation state and total activity. These changes in mitochondrial bioenergetic parameters observed during differentiation occurred in the absence of a hypermetabolic stress. A chronic (3 day) energetic stress was imposed on differentiated myotubes using sodium azide to inhibit oxidative metabolism. When used at low concentrations, azide inhibited more than 70% of cytochrome oxidase (COX) activity without changes in bioenergetics (either lactate production or creatine phosphorylation) or mRNA for mitochondrial enzymes. Higher azide concentrations resulted in changes in bioenergetic parameters and increases in steady state COX II mRNA levels. Azide did not affect mtDNA copy number or mRNA levels for other mitochondrial transcripts, suggesting azide affects stability, rather than synthesis, of COX II mRNA. These results indicate that changes in bioenergetics can alter mitochondrial genetic regulation, but that mitochondrial biogenesis accompanying differentiation occurs in the absence of hypermetabolic challenge.
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Affiliation(s)
- S C Leary
- Department of Biology, Queen's University, Kingston, Ont., Canada
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Battersby BJ, Grimm R, Huebner S, Cevc G. Evidence for three-dimensional interlayer correlations in cationic lipid-DNA complexes as observed by cryo-electron microscopy. Biochim Biophys Acta 1998; 1372:379-83. [PMID: 9675338 DOI: 10.1016/s0005-2736(98)00062-5] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
A fingerprint-like pattern across multilamellar, lipid-DNA complexes is attributed to DNA condensed as parallel helices between lipid bilayers. It is argued that the patterning indicates the existence of 3-D correlation forces between DNA-covered bilayers, following the DNA-driven formation of multilamellar liposomes from unilamellar vesicles.
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Affiliation(s)
- B J Battersby
- Medizinische Biophysik, Technische Universität München, Klinikum r. d.I., Ismaningerstr. 22, D-81675 Munich, Germany.
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Moyes CD, Battersby BJ, Leary SC. Regulation of muscle mitochondrial design. J Exp Biol 1998; 201:299-307. [PMID: 9503641] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Mitochondria are responsible for the generation of ATP to fuel muscle contraction. Hypermetabolic stresses imposed upon muscles can lead to mitochondrial proliferation, but the resulting mitochondria greatly resemble their progenitors. During the mitochondrial biogenesis that accompanies phenotypic adaptation, the stoichiometric relationships between functional elements are preserved through shared sensitivities of respiratory genes to specific transcription factors. Although the properties of muscle mitochondria are generally thought to be highly conserved across species, there are many examples of mitochondrial differences between muscle types, species and developmental states and even within single cells. In this review, we discuss (1) the nature and regulation of gene families that allow coordinated expression of genes for mitochondrial products and (2) the regulatory mechanisms by which mitochondrial differences can arise over physiological and evolutionary time.
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Affiliation(s)
- C D Moyes
- Department of Biology, Queen's University, Kingston, Ontario, Canada.
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Abstract
Mitochondria are responsible for the generation of ATP to fuel muscle contraction. Hypermetabolic stresses imposed upon muscles can lead to mitochondrial proliferation, but the resulting mitochondria greatly resemble their progenitors. During the mitochondrial biogenesis that accompanies phenotypic adaptation, the stoichiometric relationships between functional elements are preserved through shared sensitivities of respiratory genes to specific transcription factors. Although the properties of muscle mitochondria are generally thought to be highly conserved across species, there are many examples of mitochondrial differences between muscle types, species and developmental states and even within single cells. In this review, we discuss (1) the nature and regulation of gene families that allow coordinated expression of genes for mitochondrial products and (2) the regulatory mechanisms by which mitochondrial differences can arise over physiological and evolutionary time.
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Battersby BJ, McFarlane WJ, Ballantyne JS. Short-term effects of 3,5,3'-triiodothyronine on the intermediary metabolism of the dogfish shark Squalus acanthias: evidence from enzyme activities. J Exp Zool 1996; 274:157-62. [PMID: 8882493 DOI: 10.1002/(sici)1097-010x(19960215)274:3<157::aid-jez2>3.0.co;2-n] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Plasma 3,5,3'-triiodothyronine (T3) concentration decreased significantly (P < 0.05), during 1-5 days of captivity, from levels in the freshly caught dogfish shark Squalus acanthias. The short-term effects of T3 treatment on the intermediary metabolism of S. acanthias were measured in the gill, kidney, liver, and white muscle. Animals were kept for 1-5 days before experimentation. Three hours after an intraperitoneal injection with either a low T3 dose (8.3 pmol T3/kg fish) or a high T3 dose (830 pmol T3/kg fish), selected enzymes of amino acid metabolism, lipid catabolism, ketone body metabolism, glycolysis, and oxidative metabolism were measured. Activity of enzymes of amino acid metabolism and lipid catabolism increased significantly (P < 0.05) in the liver of fish treated with a low T3 dose. The low dose of T3 apparently influences glycolysis as pyruvate kinase activity significantly increase (P < 0.05) in the kidney and white muscle.
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Affiliation(s)
- B J Battersby
- Department of Biology, Queen's University, Kingston, Ontario, Canada
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Abstract
The spreading behavior of bulk lipid crystals and lipid dispersed in water has been investigated for dimyristoyl phosphatidylcholine at the air/water interface. The stable surface pressures reached with dispersed lipid were found to increase with lipid concentration up to a concentration of approximately 1.2 mg ml-1 where the spreading pressure approached 45 mN m-1, the value for excess lipid crystals placed on the surface (at 30.5 degrees C). These low surface pressures obtained with dispersions are attributed to the existence of 'pre-equilibria': surface pressures that appear steady because of the extremely slow approach to final equilibrium. Attainment of this pre-equilibrium condition usually takes about 20 h, whereas bulk crystals held at the surface generated a high and steady surface pressure within about 1 h. Hydration of the bulk lipid slows down the spreading rate, but does not affect the final surface pressure.
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Affiliation(s)
- G A Lawrie
- Department of Chemistry, The University of Queensland, St. Lucia, Australia
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