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Nusir A, Sinclair P, Kabbani N. Mitochondrial Proteomes in Neural Cells: A Systematic Review. Biomolecules 2023; 13:1638. [PMID: 38002320 PMCID: PMC10669788 DOI: 10.3390/biom13111638] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2023] [Revised: 11/07/2023] [Accepted: 11/09/2023] [Indexed: 11/26/2023] Open
Abstract
Mitochondria are ancient endosymbiotic double membrane organelles that support a wide range of eukaryotic cell functions through energy, metabolism, and cellular control. There are over 1000 known proteins that either reside within the mitochondria or are transiently associated with it. These mitochondrial proteins represent a functional subcellular protein network (mtProteome) that is encoded by mitochondrial and nuclear genomes and significantly varies between cell types and conditions. In neurons, the high metabolic demand and differential energy requirements at the synapses are met by specific modifications to the mtProteome, resulting in alterations in the expression and functional properties of the proteins involved in energy production and quality control, including fission and fusion. The composition of mtProteomes also impacts the localization of mitochondria in axons and dendrites with a growing number of neurodegenerative diseases associated with changes in mitochondrial proteins. This review summarizes the findings on the composition and properties of mtProteomes important for mitochondrial energy production, calcium and lipid signaling, and quality control in neural cells. We highlight strategies in mass spectrometry (MS) proteomic analysis of mtProteomes from cultured cells and tissue. The research into mtProteome composition and function provides opportunities in biomarker discovery and drug development for the treatment of metabolic and neurodegenerative disease.
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Affiliation(s)
- Aya Nusir
- Interdisciplinary Program in Neuroscience, School of Systems Biology, George Mason University, Fairfax, VA 22030, USA;
| | - Patricia Sinclair
- School of Systems Biology, George Mason University, Fairfax, VA 22030, USA;
| | - Nadine Kabbani
- Interdisciplinary Program in Neuroscience, School of Systems Biology, George Mason University, Fairfax, VA 22030, USA;
- School of Systems Biology, George Mason University, Fairfax, VA 22030, USA;
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2
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Miranda M, Bonekamp NA, Kühl I. Starting the engine of the powerhouse: mitochondrial transcription and beyond. Biol Chem 2022; 403:779-805. [PMID: 35355496 DOI: 10.1515/hsz-2021-0416] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2021] [Accepted: 03/09/2022] [Indexed: 12/25/2022]
Abstract
Mitochondria are central hubs for cellular metabolism, coordinating a variety of metabolic reactions crucial for human health. Mitochondria provide most of the cellular energy via their oxidative phosphorylation (OXPHOS) system, which requires the coordinated expression of genes encoded by both the nuclear (nDNA) and mitochondrial genomes (mtDNA). Transcription of mtDNA is not only essential for the biogenesis of the OXPHOS system, but also generates RNA primers necessary to initiate mtDNA replication. Like the prokaryotic system, mitochondria have no membrane-based compartmentalization to separate the different steps of mtDNA maintenance and expression and depend entirely on nDNA-encoded factors imported into the organelle. Our understanding of mitochondrial transcription in mammalian cells has largely progressed, but the mechanisms regulating mtDNA gene expression are still poorly understood despite their profound importance for human disease. Here, we review mechanisms of mitochondrial gene expression with a focus on the recent findings in the field of mammalian mtDNA transcription and disease phenotypes caused by defects in proteins involved in this process.
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Affiliation(s)
- Maria Miranda
- Department of Mitochondrial Biology, Max Planck Institute for Biology of Ageing, Cologne, D-50931, Germany
| | - Nina A Bonekamp
- Department of Neuroanatomy, Mannheim Center for Translational Neurosciences (MCTN), Medical Faculty Mannheim, Heidelberg University, Mannheim, D-68167, Germany
| | - Inge Kühl
- Department of Cell Biology, Institute of Integrative Biology of the Cell (I2BC), UMR9198, CEA, CNRS, Université Paris-Saclay, Gif-sur-Yvette, F-91190, France
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3
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Lenarčič T, Niemann M, Ramrath DJF, Calderaro S, Flügel T, Saurer M, Leibundgut M, Boehringer D, Prange C, Horn EK, Schneider A, Ban N. Mitoribosomal small subunit maturation involves formation of initiation-like complexes. Proc Natl Acad Sci U S A 2022; 119:e2114710118. [PMID: 35042777 PMCID: PMC8784144 DOI: 10.1073/pnas.2114710118] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2021] [Accepted: 10/29/2021] [Indexed: 01/02/2023] Open
Abstract
Mitochondrial ribosomes (mitoribosomes) play a central role in synthesizing mitochondrial inner membrane proteins responsible for oxidative phosphorylation. Although mitoribosomes from different organisms exhibit considerable structural variations, recent insights into mitoribosome assembly suggest that mitoribosome maturation follows common principles and involves a number of conserved assembly factors. To investigate the steps involved in the assembly of the mitoribosomal small subunit (mt-SSU) we determined the cryoelectron microscopy structures of middle and late assembly intermediates of the Trypanosoma brucei mitochondrial small subunit (mt-SSU) at 3.6- and 3.7-Å resolution, respectively. We identified five additional assembly factors that together with the mitochondrial initiation factor 2 (mt-IF-2) specifically interact with functionally important regions of the rRNA, including the decoding center, thereby preventing premature mRNA or large subunit binding. Structural comparison of assembly intermediates with mature mt-SSU combined with RNAi experiments suggests a noncanonical role of mt-IF-2 and a stepwise assembly process, where modular exchange of ribosomal proteins and assembly factors together with mt-IF-2 ensure proper 9S rRNA folding and protein maturation during the final steps of assembly.
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Affiliation(s)
- Tea Lenarčič
- Department of Biology, Institute of Molecular Biology and Biophysics, ETH Zurich, CH-8093 Zurich, Switzerland
| | - Moritz Niemann
- Department of Chemistry, Biochemistry, and Pharmaceutical Sciences, University of Bern, CH-3012 Bern, Switzerland
| | - David J F Ramrath
- Department of Biology, Institute of Molecular Biology and Biophysics, ETH Zurich, CH-8093 Zurich, Switzerland
| | - Salvatore Calderaro
- Department of Chemistry, Biochemistry, and Pharmaceutical Sciences, University of Bern, CH-3012 Bern, Switzerland
| | - Timo Flügel
- Department of Biology, Institute of Molecular Biology and Biophysics, ETH Zurich, CH-8093 Zurich, Switzerland
| | - Martin Saurer
- Department of Biology, Institute of Molecular Biology and Biophysics, ETH Zurich, CH-8093 Zurich, Switzerland
| | - Marc Leibundgut
- Department of Biology, Institute of Molecular Biology and Biophysics, ETH Zurich, CH-8093 Zurich, Switzerland
| | - Daniel Boehringer
- Department of Biology, Institute of Molecular Biology and Biophysics, ETH Zurich, CH-8093 Zurich, Switzerland
| | - Céline Prange
- Department of Biology, Institute of Molecular Biology and Biophysics, ETH Zurich, CH-8093 Zurich, Switzerland
| | - Elke K Horn
- Department of Chemistry, Biochemistry, and Pharmaceutical Sciences, University of Bern, CH-3012 Bern, Switzerland
| | - André Schneider
- Department of Chemistry, Biochemistry, and Pharmaceutical Sciences, University of Bern, CH-3012 Bern, Switzerland
| | - Nenad Ban
- Department of Biology, Institute of Molecular Biology and Biophysics, ETH Zurich, CH-8093 Zurich, Switzerland;
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4
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Srinivasan K, Banerjee A, Baid P, Dhur A, Sengupta J. Ribosome-membrane crosstalk: Co-translational targeting pathways of proteins across membranes in prokaryotes and eukaryotes. ADVANCES IN PROTEIN CHEMISTRY AND STRUCTURAL BIOLOGY 2021; 128:163-198. [PMID: 35034718 DOI: 10.1016/bs.apcsb.2021.07.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Ribosomes are the molecular machine of living cells designed for decoding mRNA-encoded genetic information into protein. Being sophisticated machinery, both in design and function, the ribosome not only carries out protein synthesis, but also coordinates several other ribosome-associated cellular processes. One such process is the translocation of proteins across or into the membrane depending on their secretory or membrane-associated nature. These proteins comprise a large portion of a cell's proteome and act as key factors for cellular survival as well as several crucial functional pathways. Protein transport to extra- and intra-cytosolic compartments (across the eukaryotic endoplasmic reticulum (ER) or across the prokaryotic plasma membrane) or insertion into membranes majorly occurs through an evolutionarily conserved protein-conducting channel called translocon (eukaryotic Sec61 or prokaryotic SecYEG channels). Targeting proteins to the membrane-bound translocon may occur via post-translational or co-translational modes and it is often mediated by recognition of an N-terminal signal sequence in the newly synthesizes polypeptide chain. Co-translational translocation is coupled to protein synthesis where the ribosome-nascent chain complex (RNC) itself is targeted to the translocon. Here, in the light of recent advances in structural and functional studies, we discuss our current understanding of the mechanistic models of co-translational translocation, coordinated by the actively translating ribosomes, in prokaryotes and eukaryotes.
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Affiliation(s)
- Krishnamoorthi Srinivasan
- Division of Structural Biology and Bioinformatics, CSIR-Indian Institute of Chemical Biology, Kolkata, India; Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, India
| | - Aneek Banerjee
- Division of Structural Biology and Bioinformatics, CSIR-Indian Institute of Chemical Biology, Kolkata, India; Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, India
| | - Priya Baid
- Division of Structural Biology and Bioinformatics, CSIR-Indian Institute of Chemical Biology, Kolkata, India
| | - Ankit Dhur
- Division of Structural Biology and Bioinformatics, CSIR-Indian Institute of Chemical Biology, Kolkata, India
| | - Jayati Sengupta
- Division of Structural Biology and Bioinformatics, CSIR-Indian Institute of Chemical Biology, Kolkata, India; Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, India.
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5
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Busch JD, Cipullo M, Atanassov I, Bratic A, Silva Ramos E, Schöndorf T, Li X, Pearce SF, Milenkovic D, Rorbach J, Larsson NG. MitoRibo-Tag Mice Provide a Tool for In Vivo Studies of Mitoribosome Composition. Cell Rep 2019; 29:1728-1738.e9. [PMID: 31693908 PMCID: PMC6859486 DOI: 10.1016/j.celrep.2019.09.080] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2019] [Revised: 08/14/2019] [Accepted: 09/26/2019] [Indexed: 11/16/2022] Open
Abstract
Mitochondria harbor specialized ribosomes (mitoribosomes) necessary for the synthesis of key membrane proteins of the oxidative phosphorylation (OXPHOS) machinery located in the mitochondrial inner membrane. To date, no animal model exists to study mitoribosome composition and mitochondrial translation coordination in mammals in vivo. Here, we create MitoRibo-Tag mice as a tool enabling affinity purification and proteomics analyses of mitoribosomes and their interactome in different tissues. We also define the composition of an assembly intermediate formed in the absence of MTERF4, necessary for a late step in mitoribosomal biogenesis. We identify the orphan protein PUSL1, which interacts with a large subunit assembly intermediate, and demonstrate that it is an inner-membrane-associated mitochondrial matrix protein required for efficient mitochondrial translation. This work establishes MitoRibo-Tag mice as a powerful tool to study mitoribosomes in vivo, enabling future studies on the mitoribosome interactome under different physiological states, as well as in disease and aging. MitoRibo-Tag mice with a tag on mL62 were generated to study mitoribosomes in vivo The mitoribosome interactome of different mouse tissues was defined with proteomics PUSL1 was identified as a mitoribosome-interacting protein using MitoRibo-Tag mice MitoRibo-Tag mice allow mitoribosome analysis under different conditions and setups
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Affiliation(s)
- Jakob D Busch
- Department of Mitochondrial Biology, Max-Planck-Institute for Biology of Ageing, Joseph-Stelzmann-Str. 9b, 50931 Cologne, Germany; Faculty of Mathematics and Natural Sciences, University of Cologne, Albertus-Magnus-Platz, 50923 Cologne, Germany
| | - Miriam Cipullo
- Department of Medical Biochemistry and Biophysics, Research Division of Molecular Metabolism, Karolinska Institutet, Solnavägen 9, 171 65 Solna, Sweden; Max-Planck-Institute for Biology of Ageing - Karolinska Institutet Laboratory, Karolinska Institutet, Stockholm, Sweden
| | - Ilian Atanassov
- Proteomics Core Facility, Max-Planck-Institute for Biology of Ageing, Joseph-Stelzmann-Str. 9b, 50931 Cologne, Germany
| | - Ana Bratic
- Department of Mitochondrial Biology, Max-Planck-Institute for Biology of Ageing, Joseph-Stelzmann-Str. 9b, 50931 Cologne, Germany
| | - Eduardo Silva Ramos
- Department of Mitochondrial Biology, Max-Planck-Institute for Biology of Ageing, Joseph-Stelzmann-Str. 9b, 50931 Cologne, Germany
| | - Thomas Schöndorf
- Department of Mitochondrial Biology, Max-Planck-Institute for Biology of Ageing, Joseph-Stelzmann-Str. 9b, 50931 Cologne, Germany; Faculty of Mathematics and Natural Sciences, University of Cologne, Albertus-Magnus-Platz, 50923 Cologne, Germany
| | - Xinping Li
- Proteomics Core Facility, Max-Planck-Institute for Biology of Ageing, Joseph-Stelzmann-Str. 9b, 50931 Cologne, Germany
| | - Sarah F Pearce
- Department of Medical Biochemistry and Biophysics, Research Division of Molecular Metabolism, Karolinska Institutet, Solnavägen 9, 171 65 Solna, Sweden; Max-Planck-Institute for Biology of Ageing - Karolinska Institutet Laboratory, Karolinska Institutet, Stockholm, Sweden
| | - Dusanka Milenkovic
- Department of Mitochondrial Biology, Max-Planck-Institute for Biology of Ageing, Joseph-Stelzmann-Str. 9b, 50931 Cologne, Germany
| | - Joanna Rorbach
- Department of Medical Biochemistry and Biophysics, Research Division of Molecular Metabolism, Karolinska Institutet, Solnavägen 9, 171 65 Solna, Sweden; Max-Planck-Institute for Biology of Ageing - Karolinska Institutet Laboratory, Karolinska Institutet, Stockholm, Sweden.
| | - Nils-Göran Larsson
- Department of Mitochondrial Biology, Max-Planck-Institute for Biology of Ageing, Joseph-Stelzmann-Str. 9b, 50931 Cologne, Germany; Department of Medical Biochemistry and Biophysics, Research Division of Molecular Metabolism, Karolinska Institutet, Solnavägen 9, 171 65 Solna, Sweden; Max-Planck-Institute for Biology of Ageing - Karolinska Institutet Laboratory, Karolinska Institutet, Stockholm, Sweden.
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6
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Rugen N, Straube H, Franken LE, Braun HP, Eubel H. Complexome Profiling Reveals Association of PPR Proteins with Ribosomes in the Mitochondria of Plants. Mol Cell Proteomics 2019; 18:1345-1362. [PMID: 31023727 PMCID: PMC6601216 DOI: 10.1074/mcp.ra119.001396] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2019] [Revised: 04/12/2019] [Indexed: 12/28/2022] Open
Abstract
Mitochondrial transcripts are subject to a wealth of processing mechanisms including cis- and trans-splicing events, as well as base modifications (RNA editing). Hundreds of proteins are required for these processes in plant mitochondria, many of which belong to the pentatricopeptide repeat (PPR) protein superfamily. The structure, localization, and function of these proteins is only poorly understood. Here we present evidence that several PPR proteins are bound to mitoribosomes in plants. A novel complexome profiling strategy in combination with chemical crosslinking has been employed to systematically define the protein constituents of the large and the small ribosomal subunits in the mitochondria of plants. We identified more than 80 ribosomal proteins, which include several PPR proteins and other non-conventional ribosomal proteins. These findings reveal a potential coupling of transcriptional and translational events in the mitochondria of plants. Furthermore, the data indicate an extremely high molecular mass of the "small" subunit, even exceeding that of the "large" subunit.
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Affiliation(s)
- Nils Rugen
- From the ‡Leibniz Universität Hannover, Institute of Plant Genetics, Herrenhäuser Str. 2, 30419 Hannover, Germany
| | - Henryk Straube
- From the ‡Leibniz Universität Hannover, Institute of Plant Genetics, Herrenhäuser Str. 2, 30419 Hannover, Germany
| | - Linda E Franken
- §Heinrich Pette Institute, Leibniz Institute for Experimental Virology - Centre for Structural Systems Biology, Notkestraβe 85, 22607 Hamburg, Germany
| | - Hans-Peter Braun
- From the ‡Leibniz Universität Hannover, Institute of Plant Genetics, Herrenhäuser Str. 2, 30419 Hannover, Germany
| | - Holger Eubel
- From the ‡Leibniz Universität Hannover, Institute of Plant Genetics, Herrenhäuser Str. 2, 30419 Hannover, Germany;.
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7
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Durigon R, Mitchell AL, Jones AW, Manole A, Mennuni M, Hirst EM, Houlden H, Maragni G, Lattante S, Doronzio PN, Dalla Rosa I, Zollino M, Holt IJ, Spinazzola A. LETM1 couples mitochondrial DNA metabolism and nutrient preference. EMBO Mol Med 2019; 10:emmm.201708550. [PMID: 30012579 PMCID: PMC6127893 DOI: 10.15252/emmm.201708550] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
The diverse clinical phenotypes of Wolf–Hirschhorn syndrome (WHS) are the result of haploinsufficiency of several genes, one of which, LETM1, encodes a protein of the mitochondrial inner membrane of uncertain function. Here, we show that LETM1 is associated with mitochondrial ribosomes, is required for mitochondrial DNA distribution and expression, and regulates the activity of an ancillary metabolic enzyme, pyruvate dehydrogenase. LETM1 deficiency in WHS alters mitochondrial morphology and DNA organization, as does substituting ketone bodies for glucose in control cells. While this change in nutrient availability leads to the death of fibroblasts with normal amounts of LETM1, WHS‐derived fibroblasts survive on ketone bodies, which can be attributed to their reduced dependence on glucose oxidation. Thus, remodeling of mitochondrial nucleoprotein complexes results from the inability of mitochondria to use specific substrates for energy production and is indicative of mitochondrial dysfunction. However, the dysfunction could be mitigated by a modified diet—for WHS, one high in lipids and low in carbohydrates.
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Affiliation(s)
- Romina Durigon
- Department of Clinical and Movement Neurosciences, UCL Institute of Neurology, London, UK
| | - Alice L Mitchell
- Department of Clinical and Movement Neurosciences, UCL Institute of Neurology, London, UK
| | - Aleck We Jones
- Department of Clinical and Movement Neurosciences, UCL Institute of Neurology, London, UK
| | - Andreea Manole
- MRC Centre for Neuromuscular Diseases, UCL Institute of Neurology and National Hospital for Neurology and Neurosurgery, London, UK.,Department of Molecular Neuroscience, UCL Institute of Neurology, London, UK
| | - Mara Mennuni
- Department of Clinical and Movement Neurosciences, UCL Institute of Neurology, London, UK
| | | | - Henry Houlden
- MRC Centre for Neuromuscular Diseases, UCL Institute of Neurology and National Hospital for Neurology and Neurosurgery, London, UK.,Department of Molecular Neuroscience, UCL Institute of Neurology, London, UK
| | | | - Serena Lattante
- Institute of Genomic Medicine, Catholic University, Rome, Italy
| | | | - Ilaria Dalla Rosa
- Department of Clinical and Movement Neurosciences, UCL Institute of Neurology, London, UK
| | | | - Ian J Holt
- Department of Clinical and Movement Neurosciences, UCL Institute of Neurology, London, UK.,Biodonostia Health Research Institute, San Sebastián, Spain.,IKERBASQUE, Basque Foundation for Science, Bilbao, Spain
| | - Antonella Spinazzola
- Department of Clinical and Movement Neurosciences, UCL Institute of Neurology, London, UK .,MRC Centre for Neuromuscular Diseases, UCL Institute of Neurology and National Hospital for Neurology and Neurosurgery, London, UK
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8
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González-Serrano LE, Chihade JW, Sissler M. When a common biological role does not imply common disease outcomes: Disparate pathology linked to human mitochondrial aminoacyl-tRNA synthetases. J Biol Chem 2019; 294:5309-5320. [PMID: 30647134 PMCID: PMC6462531 DOI: 10.1074/jbc.rev118.002953] [Citation(s) in RCA: 42] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Mitochondrial aminoacyl-tRNA synthetases (mt-aaRSs) are essential components of the mitochondrial translation machinery. The correlation of mitochondrial disorders with mutations in these enzymes has raised the interest of the scientific community over the past several years. Most surprising has been the wide-ranging presentation of clinical manifestations in patients with mt-aaRS mutations, despite the enzymes' common biochemical role. Even among cases where a common physiological system is affected, phenotypes, severity, and age of onset varies depending on which mt-aaRS is mutated. Here, we review work done thus far and propose a categorization of diseases based on tissue specificity that highlights emerging patterns. We further discuss multiple in vitro and in cellulo efforts to characterize the behavior of WT and mutant mt-aaRSs that have shaped hypotheses about the molecular causes of these pathologies. Much remains to do in order to complete our understanding of these proteins. We expect that futher work is likely to result in the discovery of new roles for the mt-aaRSs in addition to their fundamental function in mitochondrial translation, informing the development of treatment strategies and diagnoses.
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Affiliation(s)
- Ligia Elena González-Serrano
- From the Université de Strasbourg, CNRS, Architecture et Réactivité de l'ARN, UPR9002, F-67000 Strasbourg, France and
| | - Joseph W Chihade
- the Department of Chemistry, Carleton College, Northfield, Minnesota 55057
| | - Marie Sissler
- From the Université de Strasbourg, CNRS, Architecture et Réactivité de l'ARN, UPR9002, F-67000 Strasbourg, France and
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9
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Xu D, Zhao Y, Weng X, Lu Y, Li W, Tang K, Chen W, Liu Z, Qi X, Zheng J, Fassett J, Zhang Y, Xu Y. Novel role of mitochondrial GTPases 1 in pathological cardiac hypertrophy. J Mol Cell Cardiol 2019; 128:105-116. [PMID: 30707992 DOI: 10.1016/j.yjmcc.2019.01.025] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/05/2018] [Revised: 01/22/2019] [Accepted: 01/28/2019] [Indexed: 11/28/2022]
Abstract
While most mitochondrial proteins are encoded in the nucleus and translated on cytosolic/endoplasmic reticulum ribosomes, proteins encoded by mitochondrial DNA are translated on mitochondrial ribosomes. Mitochondrial GTPases 1 (MTG1) regulates mitochondrial ribosome assembly and translation, but its impact on cardiac adaptation to stress is unknown. Here, we found that MTG1 is dramatically elevated in hearts of dilated cardiomyopathy patients and in mice exposed to left ventricular pressure overload (AB). To examine the role of MTG1 in cardiac hypertrophy and heart failure, MTG1 loss/gain of function studies were performed in cultured cardiomyocytes and mice exposed to hypertrophic stress. MTG1 shRNA and adenoviral overexpression studies indicated that MTG1 expression attenuates angiotensin II-induced hypertrophy in cultured cardiomyocytes, while MTG1 KO mice exhibited no observable cardiac phenotype under basal conditions. MTG1 deficiency significantly exacerbated AB-induced cardiac hypertrophy, expression of hypertrophic stress markers, fibrosis, and LV dysfunction in comparison to WT mice. Conversely, transgenic cardiac MTG1 expression attenuated AB-induced hypertrophy and LV dysfunction. Mechanistically, MTG1 preserved mitochondrial respiratory chain complex activity during pressure overload, which further attenuated ROS generation. Moreover, we demonstrated that TAK1, P38 and JNK1/2 activity is downregulated in the MTG1 overexpression group. Importantly, dampening oxidative stress with N-acetylcysteine (NAC) lowered hypertrophy in MTG1 KO to WT levels. Collectively, our data indicate that MTG1 protects against pressure overload-induced cardiac hypertrophy and dysfunction by preserving mitochondrial function and reducing oxidative stress and downstream TAK1 stress signaling.
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Affiliation(s)
- Dachun Xu
- Department of Cardiology, Shanghai Tenth People's Hospital, Tongji University School of Medicine, Shanghai, China
| | - Yifan Zhao
- Department of Cardiology, Shanghai Tenth People's Hospital, Tongji University School of Medicine, Shanghai, China
| | - Xinyu Weng
- Department of Cardiology, Shanghai Tenth People's Hospital, Tongji University School of Medicine, Shanghai, China
| | - Yuyan Lu
- Department of Cardiology, Shanghai Tenth People's Hospital, Tongji University School of Medicine, Shanghai, China
| | - Weiming Li
- Department of Cardiology, Shanghai Tenth People's Hospital, Tongji University School of Medicine, Shanghai, China
| | - Kai Tang
- Department of Cardiology, Shanghai Tenth People's Hospital, Tongji University School of Medicine, Shanghai, China
| | - Wei Chen
- Department of Cardiology, Shanghai Tenth People's Hospital, Tongji University School of Medicine, Shanghai, China
| | - Zheng Liu
- Wadsworth Center, New York State Department of Health, Albany, USA
| | - Xinrui Qi
- Center for Translational Neurodegeneration and Regenerative Therapy, Shanghai Tenth People's Hospital Affiliated with Tongji University School of Medicine, China
| | - Jialing Zheng
- Center for Translational Neurodegeneration and Regenerative Therapy, Shanghai Tenth People's Hospital Affiliated with Tongji University School of Medicine, China
| | - John Fassett
- Department of Pharmacology and Toxicology, University of Graz, Graz 8020, Austria
| | - Yi Zhang
- Department of Cardiology, Shanghai Tenth People's Hospital, Tongji University School of Medicine, Shanghai, China.
| | - Yawei Xu
- Department of Cardiology, Shanghai Tenth People's Hospital, Tongji University School of Medicine, Shanghai, China.
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10
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González-Serrano LE, Karim L, Pierre F, Schwenzer H, Rötig A, Munnich A, Sissler M. Three human aminoacyl-tRNA synthetases have distinct sub-mitochondrial localizations that are unaffected by disease-associated mutations. J Biol Chem 2018; 293:13604-13615. [PMID: 30006346 PMCID: PMC6120215 DOI: 10.1074/jbc.ra118.003400] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2018] [Revised: 07/12/2018] [Indexed: 01/04/2023] Open
Abstract
Human mitochondrial aminoacyl-tRNA synthetases (mt-aaRSs) are key enzymes in the mitochondrial protein translation system and catalyze the charging of amino acids on their cognate tRNAs. Mutations in their nuclear genes are associated with pathologies having a broad spectrum of clinical phenotypes, but with no clear molecular mechanism(s). For example, mutations in the nuclear genes encoding mt-AspRS and mt-ArgRS are correlated with the moderate neurodegenerative disorder leukoencephalopathy with brainstem and spinal cord involvement and lactate elevation (LBSL) and with the severe neurodevelopmental disorder pontocerebellar hypoplasia type 6 (PCH6), respectively. Previous studies have shown no or only minor impacts of these mutations on the canonical properties of these enzymes, indicating that the role of the mt-aaRSs in protein synthesis is mostly not affected by these mutations, but their effects on the mitochondrial localizations of aaRSs remain unclear. Here, we demonstrate that three human aaRSs, mt-AspRS, mt-ArgRS, and LysRS, each have a specific sub-mitochondrial distribution, with mt-ArgRS being exclusively localized in the membrane, LysRS exclusively in the soluble fraction, and mt-AspRS being present in both. Chemical treatments revealed that mt-AspRs is anchored in the mitochondrial membrane through electrostatic interactions, whereas mt-ArgRS uses hydrophobic interactions. We also report that novel mutations in mt-AspRS and mt-ArgRS genes from individuals with LBSL and PCH6, respectively, had no significant impact on the mitochondrial localizations of mt-AspRS and mt-ArgRS. The variable sub-mitochondrial locations for these three mt-aaRSs strongly suggest the existence of additional enzyme properties, requiring further investigation to unravel the mechanisms underlying the two neurodegenerative disorders.
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Affiliation(s)
- Ligia Elena González-Serrano
- From the Université de Strasbourg, CNRS, Architecture et Réactivité de l'ARN, UPR9002, F-67084 Strasbourg, France and
| | - Loukmane Karim
- From the Université de Strasbourg, CNRS, Architecture et Réactivité de l'ARN, UPR9002, F-67084 Strasbourg, France and
| | - Florian Pierre
- From the Université de Strasbourg, CNRS, Architecture et Réactivité de l'ARN, UPR9002, F-67084 Strasbourg, France and
| | - Hagen Schwenzer
- From the Université de Strasbourg, CNRS, Architecture et Réactivité de l'ARN, UPR9002, F-67084 Strasbourg, France and
| | - Agnès Rötig
- the INSERM UMR 1163, Laboratory of Genetics of Mitochondrial Disorders, Paris Descartes-Sorbonne Paris Cité University, Imagine Institute, F-75015 Paris, France
| | - Arnold Munnich
- the INSERM UMR 1163, Laboratory of Genetics of Mitochondrial Disorders, Paris Descartes-Sorbonne Paris Cité University, Imagine Institute, F-75015 Paris, France
| | - Marie Sissler
- From the Université de Strasbourg, CNRS, Architecture et Réactivité de l'ARN, UPR9002, F-67084 Strasbourg, France and
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11
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Bieri P, Greber BJ, Ban N. High-resolution structures of mitochondrial ribosomes and their functional implications. Curr Opin Struct Biol 2018; 49:44-53. [DOI: 10.1016/j.sbi.2017.12.009] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2017] [Revised: 12/08/2017] [Accepted: 12/22/2017] [Indexed: 01/06/2023]
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12
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Hameed MW, Juszczak I, Bock R, van Dongen JT. Comparison of mitochondrial gene expression and polysome loading in different tobacco tissues. PLANT METHODS 2017; 13:112. [PMID: 29255478 PMCID: PMC5729415 DOI: 10.1186/s13007-017-0257-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/07/2017] [Accepted: 11/22/2017] [Indexed: 06/07/2023]
Abstract
BACKGROUND To investigate translational regulation of gene expression in plant mitochondria, a mitochondrial polysome isolation protocol was established for tobacco to investigate polysomal mRNA loading as a proxy for translational activity. Furthermore, we developed an oligonucleotide based microarray platform to determine the level of Nicotiana tabacum and Arabidopsis thaliana mitochondrial mRNA. RESULTS Microarray analysis of free and polysomal mRNAs was used to characterize differences in the levels of free transcripts and ribosome-bound mRNAs in various organs of tobacco plants. We have observed higher mitochondrial transcript levels in young leaves, flowers and floral buds as compared to fully expanded leaves and roots. A similar pattern of abundance was observed for ribosome-bound mitochondrial mRNAs in these tissues. However, the accumulation of the mitochondrial protein COX2 was found to be inversely related to that of its ribosome-bound mRNA. CONCLUSIONS Our results indicate that the association of mitochondrial mRNAs to ribosomes is largely determined by the total transcript level of a gene. However, at least for Cox2, we demonstrated that the level of ribosome-bound mRNA is not reflected by the amount of COX2 protein.
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Affiliation(s)
- Muhammad Waqar Hameed
- Max Planck Institute of Molecular Plant Physiology, Am Mühlenberg 1, 14476 Potsdam-Golm, Germany
- Dr. Panjwani Center for Molecular Medicine and Drug Research, International Center for Chemical and Biological Sciences, University of Karachi, Karachi, 75270 Pakistan
| | - Ilona Juszczak
- Max Planck Institute of Molecular Plant Physiology, Am Mühlenberg 1, 14476 Potsdam-Golm, Germany
- Molecular Physiology, University of Bonn, Kirschallee 1, 53115 Bonn, Germany
| | - Ralph Bock
- Max Planck Institute of Molecular Plant Physiology, Am Mühlenberg 1, 14476 Potsdam-Golm, Germany
| | - Joost Thomas van Dongen
- Max Planck Institute of Molecular Plant Physiology, Am Mühlenberg 1, 14476 Potsdam-Golm, Germany
- Institute of Biology I, RWTH Aachen University, Worringerweg 1, 52056 Aachen, Germany
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13
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Mitsopoulos P, Lapohos O, Weraarpachai W, Antonicka H, Chang YH, Madrenas J. Stomatin-like protein 2 deficiency results in impaired mitochondrial translation. PLoS One 2017; 12:e0179967. [PMID: 28654702 PMCID: PMC5487072 DOI: 10.1371/journal.pone.0179967] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2017] [Accepted: 06/07/2017] [Indexed: 12/22/2022] Open
Abstract
Mitochondria translate the RNAs for 13 core polypeptides of respiratory chain and ATP synthase complexes that are essential for the assembly and function of these complexes. This process occurs in close proximity to the mitochondrial inner membrane. However, the mechanisms and molecular machinery involved in mitochondrial translation are not fully understood, and defects in this process can result in severe diseases. Stomatin-like protein (SLP)-2 is a mainly mitochondrial protein that forms cardiolipin- and prohibitin-enriched microdomains in the mitochondrial inner membrane that are important for the formation of respiratory supercomplexes and their function. Given this regulatory role of SLP-2 in processes closely associated with the mitochondrial inner membrane, we hypothesized that the function of SLP-2 would have an impact on mitochondrial translation. 35S-Methionine/cysteine pulse labeling of resting or activated T cells from T cell-specific Slp-2 knockout mice showed a significant impairment in the production of several mitochondrial DNA-encoded polypeptides following T cell activation, including Cytb, COXI, COXII, COXIII, and ATP6. Measurement of mitochondrial DNA stability and mitochondrial transcription revealed that this impairment was at the post-transcriptional level. Examination of mitochondrial ribosome assembly showed that SLP-2 migrated in sucrose-density gradients similarly to the large ribosomal subunit but that its deletion at the genetic level did not affect mitochondrial ribosome assembly. Functionally, the impairment in mitochondrial translation correlated with decreased interleukin-2 production in activated T cells. Altogether, these data show that SLP-2 acts as a general regulator of mitochondrial translation.
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Affiliation(s)
- Panagiotis Mitsopoulos
- Microbiome and Disease Tolerance Centre, Department of Microbiology and Immunology, McGill University, Montreal, Quebec, Canada
- Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, California, United States of America
| | - Orsolya Lapohos
- Microbiome and Disease Tolerance Centre, Department of Microbiology and Immunology, McGill University, Montreal, Quebec, Canada
- Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, California, United States of America
| | - Woranontee Weraarpachai
- Department of Human Genetics and Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada
- Department of Biochemistry, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand
| | - Hana Antonicka
- Department of Human Genetics and Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada
| | - Yu-Han Chang
- Microbiome and Disease Tolerance Centre, Department of Microbiology and Immunology, McGill University, Montreal, Quebec, Canada
- Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, California, United States of America
| | - Joaquín Madrenas
- Microbiome and Disease Tolerance Centre, Department of Microbiology and Immunology, McGill University, Montreal, Quebec, Canada
- Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, California, United States of America
- * E-mail:
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14
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Woellhaf MW, Sommer F, Schroda M, Herrmann JM. Proteomic profiling of the mitochondrial ribosome identifies Atp25 as a composite mitochondrial precursor protein. Mol Biol Cell 2016; 27:3031-3039. [PMID: 27582385 PMCID: PMC5063612 DOI: 10.1091/mbc.e16-07-0513] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2016] [Revised: 08/18/2016] [Accepted: 08/23/2016] [Indexed: 11/15/2022] Open
Abstract
Whereas the structure and function of cytosolic ribosomes are well characterized, we only have a limited understanding of the mitochondrial translation apparatus. Using SILAC-based proteomic profiling, we identified 13 proteins that cofractionated with the mitochondrial ribosome, most of which play a role in translation or ribosomal biogenesis. One of these proteins is a homologue of the bacterial ribosome-silencing factor (Rsf). This protein is generated from the composite precursor protein Atp25 upon internal cleavage by the matrix processing peptidase MPP, and in this respect, it differs from all other characterized mitochondrial proteins of baker's yeast. We observed that cytosolic expression of Rsf, but not of noncleaved Atp25 protein, is toxic. Our results suggest that eukaryotic cells face the challenge of avoiding negative interference from the biogenesis of their two distinct translation machineries.
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Affiliation(s)
- Michael W Woellhaf
- Cell Biology, University of Kaiserslautern, 67663 Kaiserslautern, Germany
| | - Frederik Sommer
- Molecular Biotechnology and Systems Biology, University of Kaiserslautern, 67663 Kaiserslautern, Germany
| | - Michael Schroda
- Molecular Biotechnology and Systems Biology, University of Kaiserslautern, 67663 Kaiserslautern, Germany
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15
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Abstract
Oxidative phosphorylation (OXPHOS) is the mechanism whereby ATP, the major energy source for the cell, is produced by harnessing cellular respiration in the mitochondrion. This is facilitated by five multi-subunit complexes housed within the inner mitochondrial membrane. These complexes, with the exception of complex II, are of a dual genetic origin, requiring expression from nuclear and mitochondrial genes. Mitochondrially encoded mRNA is translated on the mitochondrial ribosome (mitoribosome) and the recent release of the near atomic resolution structure of the mammalian mitoribosome has highlighted its peculiar features. However, whereas some aspects of mitochondrial translation are understood, much is to be learnt about the presentation of mitochondrial mRNA to the mitoribosome, the biogenesis of the machinery, the exact role of the membrane, the constitution of the translocon/insertion machinery and the regulation of translation in the mitochondrion. This review addresses our current knowledge of mammalian mitochondrial gene expression, highlights key questions and indicates how defects in this process can result in profound mitochondrial disease.
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16
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Affiliation(s)
- Martin Ott
- Department of Biochemistry and Biophysics, Stockholm University, SE-106 91 Stockholm, Sweden;
| | - Alexey Amunts
- Department of Biochemistry and Biophysics, Stockholm University, SE-106 91 Stockholm, Sweden;
- Science for Life Laboratory, Stockholm University, SE-171 21 Solna, Sweden;
| | - Alan Brown
- Laboratory of Molecular Biology, Medical Research Council, Cambridge CB2 0QH, United Kingdom;
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17
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Ostojić J, Panozzo C, Bourand-Plantefol A, Herbert CJ, Dujardin G, Bonnefoy N. Ribosome recycling defects modify the balance between the synthesis and assembly of specific subunits of the oxidative phosphorylation complexes in yeast mitochondria. Nucleic Acids Res 2016; 44:5785-97. [PMID: 27257059 PMCID: PMC4937339 DOI: 10.1093/nar/gkw490] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2016] [Accepted: 05/20/2016] [Indexed: 01/07/2023] Open
Abstract
Mitochondria have their own translation machinery that produces key subunits of the OXPHOS complexes. This machinery relies on the coordinated action of nuclear-encoded factors of bacterial origin that are well conserved between humans and yeast. In humans, mutations in these factors can cause diseases; in yeast, mutations abolishing mitochondrial translation destabilize the mitochondrial DNA. We show that when the mitochondrial genome contains no introns, the loss of the yeast factors Mif3 and Rrf1 involved in ribosome recycling neither blocks translation nor destabilizes mitochondrial DNA. Rather, the absence of these factors increases the synthesis of the mitochondrially-encoded subunits Cox1, Cytb and Atp9, while strongly impairing the assembly of OXPHOS complexes IV and V. We further show that in the absence of Rrf1, the COX1 specific translation activator Mss51 accumulates in low molecular weight forms, thought to be the source of the translationally-active form, explaining the increased synthesis of Cox1. We propose that Rrf1 takes part in the coordination between translation and OXPHOS assembly in yeast mitochondria. These interactions between general and specific translation factors might reveal an evolutionary adaptation of the bacterial translation machinery to the set of integral membrane proteins that are translated within mitochondria.
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Affiliation(s)
- Jelena Ostojić
- Institute of Integrative Biology of the Cell (I2BC), CEA, CNRS, Université Paris-Sud, Université Paris-Saclay, UEVE, 91198, Gif-sur-Yvette cedex, France
| | - Cristina Panozzo
- Institute of Integrative Biology of the Cell (I2BC), CEA, CNRS, Université Paris-Sud, Université Paris-Saclay, UEVE, 91198, Gif-sur-Yvette cedex, France
| | - Alexa Bourand-Plantefol
- Institute of Integrative Biology of the Cell (I2BC), CEA, CNRS, Université Paris-Sud, Université Paris-Saclay, UEVE, 91198, Gif-sur-Yvette cedex, France
| | - Christopher J Herbert
- Institute of Integrative Biology of the Cell (I2BC), CEA, CNRS, Université Paris-Sud, Université Paris-Saclay, UEVE, 91198, Gif-sur-Yvette cedex, France
| | - Geneviève Dujardin
- Institute of Integrative Biology of the Cell (I2BC), CEA, CNRS, Université Paris-Sud, Université Paris-Saclay, UEVE, 91198, Gif-sur-Yvette cedex, France
| | - Nathalie Bonnefoy
- Institute of Integrative Biology of the Cell (I2BC), CEA, CNRS, Université Paris-Sud, Université Paris-Saclay, UEVE, 91198, Gif-sur-Yvette cedex, France
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18
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Abstract
Mitochondrial ribosomes (mitoribosomes) perform protein synthesis inside mitochondria, the organelles responsible for energy conversion and adenosine triphosphate production in eukaryotic cells. Throughout evolution, mitoribosomes have become functionally specialized for synthesizing mitochondrial membrane proteins, and this has been accompanied by large changes to their structure and composition. We review recent high-resolution structural data that have provided unprecedented insight into the structure and function of mitoribosomes in mammals and fungi.
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Affiliation(s)
- Basil J Greber
- Department of Biology, Institute of Molecular Biology and Biophysics, ETH Zurich, CH-8093 Zurich, Switzerland; .,*Present address: California Institute for Quantitative Biosciences (QB3), University of California, Berkeley, California 94720-3220
| | - Nenad Ban
- Department of Biology, Institute of Molecular Biology and Biophysics, ETH Zurich, CH-8093 Zurich, Switzerland;
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19
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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: 84] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [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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20
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De Silva D, Tu YT, Amunts A, Fontanesi F, Barrientos A. Mitochondrial ribosome assembly in health and disease. Cell Cycle 2015; 14:2226-50. [PMID: 26030272 DOI: 10.1080/15384101.2015.1053672] [Citation(s) in RCA: 130] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
The ribosome is a structurally and functionally conserved macromolecular machine universally responsible for catalyzing protein synthesis. Within eukaryotic cells, mitochondria contain their own ribosomes (mitoribosomes), which synthesize a handful of proteins, all essential for the biogenesis of the oxidative phosphorylation system. High-resolution cryo-EM structures of the yeast, porcine and human mitoribosomal subunits and of the entire human mitoribosome have uncovered a wealth of new information to illustrate their evolutionary divergence from their bacterial ancestors and their adaptation to synthesis of highly hydrophobic membrane proteins. With such structural data becoming available, one of the most important remaining questions is that of the mitoribosome assembly pathway and factors involved. The regulation of mitoribosome biogenesis is paramount to mitochondrial respiration, and thus to cell viability, growth and differentiation. Moreover, mutations affecting the rRNA and protein components produce severe human mitochondrial disorders. Despite its biological and biomedical significance, knowledge on mitoribosome biogenesis and its deviations from the much-studied bacterial ribosome assembly processes is scarce, especially the order of rRNA processing and assembly events and the regulatory factors required to achieve fully functional particles. This article focuses on summarizing the current available information on mitoribosome assembly pathway, factors that form the mitoribosome assembly machinery, and the effect of defective mitoribosome assembly on human health.
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Affiliation(s)
- Dasmanthie De Silva
- a Department of Biochemistry and Molecular Biology ; University of Miami Miller School of Medicine ; Miami , FL USA
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21
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22
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D'Anna C, Cigna D, Costanzo G, Bruno A, Ferraro M, Di Vincenzo S, Bianchi L, Bini L, Gjomarkaj M, Pace E. Cigarette smoke alters the proteomic profile of lung fibroblasts. MOLECULAR BIOSYSTEMS 2015; 11:1644-52. [DOI: 10.1039/c5mb00188a] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
The protein identified here may offer a new insight into deciphering damage caused by cigarette smoke.
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Affiliation(s)
- Claudia D'Anna
- Institute of Biomedicine and Molecular Immunology (IBIM)
- CNR
- Palermo
- Italy
| | - Diego Cigna
- Institute of Biomedicine and Molecular Immunology (IBIM)
- CNR
- Palermo
- Italy
| | - Giorgia Costanzo
- Institute of Biomedicine and Molecular Immunology (IBIM)
- CNR
- Palermo
- Italy
| | - Andreina Bruno
- Institute of Biomedicine and Molecular Immunology (IBIM)
- CNR
- Palermo
- Italy
| | - Maria Ferraro
- Institute of Biomedicine and Molecular Immunology (IBIM)
- CNR
- Palermo
- Italy
| | | | - Laura Bianchi
- Laboratory of Functional Proteomics
- Molecular Biology Department
- Università degli Studi di Siena
- Siena
- Italy
| | - Luca Bini
- Laboratory of Functional Proteomics
- Molecular Biology Department
- Università degli Studi di Siena
- Siena
- Italy
| | - Mark Gjomarkaj
- Institute of Biomedicine and Molecular Immunology (IBIM)
- CNR
- Palermo
- Italy
| | - Elisabetta Pace
- Institute of Biomedicine and Molecular Immunology (IBIM)
- CNR
- Palermo
- Italy
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23
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Brown A, Amunts A, Bai XC, Sugimoto Y, Edwards PC, Murshudov G, Scheres SHW, Ramakrishnan V. Structure of the large ribosomal subunit from human mitochondria. Science 2014; 346:718-722. [PMID: 25278503 DOI: 10.1126/science.1258026] [Citation(s) in RCA: 234] [Impact Index Per Article: 23.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Human mitochondrial ribosomes are highly divergent from all other known ribosomes and are specialized to exclusively translate membrane proteins. They are linked with hereditary mitochondrial diseases and are often the unintended targets of various clinically useful antibiotics. Using single-particle cryogenic electron microscopy, we have determined the structure of its large subunit to 3.4 angstrom resolution, revealing 48 proteins, 21 of which are specific to mitochondria. The structure unveils an adaptation of the exit tunnel for hydrophobic nascent peptides, extensive remodeling of the central protuberance, including recruitment of mitochondrial valine transfer RNA (tRNA(Val)) to play an integral structural role, and changes in the tRNA binding sites related to the unusual characteristics of mitochondrial tRNAs.
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Affiliation(s)
- Alan Brown
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, United Kingdom
| | - Alexey Amunts
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, United Kingdom
| | - Xiao-Chen Bai
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, United Kingdom
| | - Yoichiro Sugimoto
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, United Kingdom
| | - Patricia C Edwards
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, United Kingdom
| | - Garib Murshudov
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, United Kingdom
| | - Sjors H W Scheres
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, United Kingdom
| | - V Ramakrishnan
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, United Kingdom
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24
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Abstract
Understanding regulation of mitochondrial DNA (mtDNA) expression is of considerable interest given that mitochondrial dysfunction is important in human pathology and aging. Similar to the situation in bacteria, there is no compartmentalization between transcription and translation in mitochondria; hence, both processes are likely to have a direct molecular crosstalk. Accumulating evidence suggests that there are important mechanisms for regulation of mammalian mtDNA expression at the posttranscriptional level. Regulation of mRNA maturation, mRNA stability, translational coordination, ribosomal biogenesis, and translation itself all form the basis for controlling oxidative phosphorylation capacity. Consequently, a wide variety of inherited human mitochondrial diseases are caused by mutations of nuclear genes regulating various aspects of mitochondrial translation. Furthermore, mutations of mtDNA, associated with human disease and aging, often affect tRNA genes critical for mitochondrial translation. Recent advances in molecular understanding of mitochondrial translation regulation will most likely provide novel avenues for modulating mitochondrial function for treating human disease.
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Affiliation(s)
- B Martin Hällberg
- Department of Cell and Molecular Biology, Karolinska Institutet, 171 77 Stockholm, Sweden; Röntgen-Ångström-Cluster, Karolinska Institutet Outstation, Centre for Structural Systems Biology, DESY Campus, 22603 Hamburg, Germany; European Molecular Biology Laboratory, Hamburg Unit, 22603 Hamburg, Germany.
| | - Nils-Göran Larsson
- Department of Mitochondrial Biology, Max Planck Institute for Biology of Ageing, 509 31 Cologne, Germany; Department of Laboratory Medicine, Karolinska Institutet, 171 77 Stockholm, Sweden.
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25
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Lightowlers RN, Rozanska A, Chrzanowska-Lightowlers ZM. Mitochondrial protein synthesis: figuring the fundamentals, complexities and complications, of mammalian mitochondrial translation. FEBS Lett 2014; 588:2496-503. [PMID: 24911204 PMCID: PMC4099522 DOI: 10.1016/j.febslet.2014.05.054] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2014] [Revised: 05/28/2014] [Accepted: 05/29/2014] [Indexed: 12/28/2022]
Abstract
Mitochondrial protein synthesis is essential for all mammals, being responsible for providing key components of the oxidative phosphorylation complexes. Although only thirteen different polypeptides are made, the molecular details of this deceptively simple process remain incomplete. Central to this process is a non-canonical ribosome, the mitoribosome, which has evolved to address its unique mandate. In this review, we integrate the current understanding of the molecular aspects of mitochondrial translation with recent advances in structural biology. We identify numerous key questions that we will need to answer if we are to increase our knowledge of the molecular mechanisms underlying mitochondrial protein synthesis.
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Affiliation(s)
- Robert N Lightowlers
- The Wellcome Trust Centre for Mitochondrial Research, Institute for Cell and Molecular Biosciences, Newcastle University, The Medical School, Framlington Place, Newcastle upon Tyne NE2 4HH, UK.
| | - Agata Rozanska
- The Wellcome Trust Centre for Mitochondrial Research, Institute for Cell and Molecular Biosciences, Newcastle University, The Medical School, Framlington Place, Newcastle upon Tyne NE2 4HH, UK
| | - Zofia M Chrzanowska-Lightowlers
- The Wellcome Trust Centre for Mitochondrial Research, Institute of Neuroscience, Newcastle University, The Medical School, Framlington Place, Newcastle upon Tyne NE2 4HH, UK.
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26
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Bogenhagen DF, Martin DW, Koller A. Initial steps in RNA processing and ribosome assembly occur at mitochondrial DNA nucleoids. Cell Metab 2014; 19:618-29. [PMID: 24703694 DOI: 10.1016/j.cmet.2014.03.013] [Citation(s) in RCA: 75] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/08/2013] [Revised: 12/17/2013] [Accepted: 02/06/2014] [Indexed: 10/25/2022]
Abstract
Mammalian mitochondrial DNA (mtDNA) resides in compact nucleoids, where it is replicated and transcribed into long primary transcripts processed to generate rRNAs, tRNAs, and mRNAs encoding 13 proteins. This situation differs from bacteria and eukaryotic nucleoli, which have dedicated rRNA transcription units. The assembly of rRNAs into mitoribosomes has received little study. We show that mitochondrial RNA processing enzymes involved in tRNA excision, ribonuclease P (RNase P) and ELAC2, as well as a subset of nascent mitochondrial ribosomal proteins (MRPs) associate with nucleoids to initiate RNA processing and ribosome assembly. SILAC pulse-chase labeling experiments show that nascent MRPs recruited to the nucleoid fraction were highly labeled after the pulse in a transcription-dependent manner and decreased in labeling intensity during the chase. These results provide insight into the landscape of binding events required for mitochondrial ribosome assembly and firmly establish the mtDNA nucleoid as a control center for mitochondrial biogenesis.
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Affiliation(s)
- Daniel F Bogenhagen
- Department of Pharmacological Sciences, Stony Brook University, Stony Brook, NY 11794-8651, USA.
| | - Dwight W Martin
- Department of Medicine, Stony Brook University, Stony Brook, NY 11794-8160, USA; Proteomics Center, Stony Brook University, Stony Brook, NY 11794-8691, USA
| | - Antonius Koller
- Proteomics Center, Stony Brook University, Stony Brook, NY 11794-8691, USA
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27
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The Mitochondrial Aminoacyl tRNA Synthetases: Genes and Syndromes. Int J Cell Biol 2014; 2014:787956. [PMID: 24639874 PMCID: PMC3932222 DOI: 10.1155/2014/787956] [Citation(s) in RCA: 103] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2013] [Accepted: 12/01/2013] [Indexed: 02/05/2023] Open
Abstract
Mitochondrial respiratory chain (RC) disorders are a group of genetically and clinically heterogeneous diseases. This is because protein components of the RC are encoded by both mitochondrial and nuclear genomes and are essential in all cells. In addition, the biogenesis and maintenance of mitochondria, including mitochondrial DNA (mtDNA) replication, transcription, and translation, require nuclear-encoded genes. In the past decade, a growing number of syndromes associated with dysfunction of mtDNA translation have been reported. This paper reviews the current knowledge of mutations affecting mitochondrial aminoacyl tRNAs synthetases and their role in the pathogenic mechanisms underlying the different clinical presentations.
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28
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Molecular crowding inhibits U-insertion/deletion RNA editing in vitro: consequences for the in vivo reaction. PLoS One 2013; 8:e83796. [PMID: 24376749 PMCID: PMC3871654 DOI: 10.1371/journal.pone.0083796] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2013] [Accepted: 11/16/2013] [Indexed: 01/02/2023] Open
Abstract
Mitochondrial pre-mRNAs in African trypanosomes are edited to generate functional transcripts. The reaction is typified by the insertion and deletion of U nucleotides and is catalyzed by a macromolecular complex, the editosome. Editosomes bind pre-edited mRNA/gRNA pairs and the reaction can be recapitulated in vitro by using pre-mRNA- and gRNA-mimicking oligoribonucleotides together with enriched editosome preparations. Although the in vitro assay has been instrumental in unraveling the basic steps of the editing cycle it is performed at dilute solvent conditions. This ignores the fact that editing takes place inside the highly crowded mitochondria. Here we investigate the effects of molecular crowding on RNA editing. By using neutral, macromolecular cosolutes we generate defined dilute, semidilute and crowded solvent properties and we demonstrate different thermodynamic stabilities of the pre-mRNA/gRNA hybrid RNAs at these conditions. Crowded conditions stabilize the RNAs by -30 kJ/mol. Furthermore, we show that the rate constants for the association and dissociation (kass/kdiss) of substrate RNAs to editosomes decrease, ultimately inhibiting the in vitro reaction. The data demonstrate that the current RNA editing in vitro system is sensitive to molecular crowding, which suggests that the in vivo reaction cannot rely on a diffusion-controlled, collision-based mechanism. Possible non-diffusional reaction pathways are discussed.
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29
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Architecture of the large subunit of the mammalian mitochondrial ribosome. Nature 2013; 505:515-9. [PMID: 24362565 DOI: 10.1038/nature12890] [Citation(s) in RCA: 177] [Impact Index Per Article: 16.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2013] [Accepted: 11/15/2013] [Indexed: 01/30/2023]
Abstract
Mitochondrial ribosomes synthesize a number of highly hydrophobic proteins encoded on the genome of mitochondria, the organelles in eukaryotic cells that are responsible for energy conversion by oxidative phosphorylation. The ribosomes in mammalian mitochondria have undergone massive structural changes throughout their evolution, including ribosomal RNA shortening and acquisition of mitochondria-specific ribosomal proteins. Here we present the three-dimensional structure of the 39S large subunit of the porcine mitochondrial ribosome determined by cryo-electron microscopy at 4.9 Å resolution. The structure, combined with data from chemical crosslinking and mass spectrometry experiments, reveals the unique features of the 39S subunit at near-atomic resolution and provides detailed insight into the architecture of the polypeptide exit site. This region of the mitochondrial ribosome has been considerably remodelled compared to its bacterial counterpart, providing a specialized platform for the synthesis and membrane insertion of the highly hydrophobic protein components of the respiratory chain.
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Kotani T, Akabane S, Takeyasu K, Ueda T, Takeuchi N. Human G-proteins, ObgH1 and Mtg1, associate with the large mitochondrial ribosome subunit and are involved in translation and assembly of respiratory complexes. Nucleic Acids Res 2013; 41:3713-22. [PMID: 23396448 PMCID: PMC3616715 DOI: 10.1093/nar/gkt079] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
The bacterial homologues of ObgH1 and Mtg1, ObgE and RbgA, respectively, have been suggested to be involved in the assembly of large ribosomal subunits. We sought to elucidate the functions of ObgH1 and Mtg1 in ribosome biogenesis in human mitochondria. ObgH1 and Mtg1 are localized in mitochondria in association with the inner membrane, and are exposed on the matrix side. Mtg1 and ObgH1 specifically associate with the large subunit of the mitochondrial ribosome in GTP-dependent manner. The large ribosomal subunit stimulated the GTPase activity of Mtg1, whereas only the intrinsic GTPase activity was detectable with ObgH1. The knockdown of Mtg1 decreased the overall mitochondrial translation activity, and caused defects in the formation of respiratory complexes. On the other hand, the depletion of ObgH1 led to the specific activation of the translation of subunits of Complex V, and disrupted its proper formation. Our results suggested that Mtg1 and ObgH1 function with the large subunit of the mitochondrial ribosome, and are also involved in both the translation and assembly of respiratory complexes. The fine coordination of ribosome assembly, translation and respiratory complex formation in mammalian mitochondria is affirmed.
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Affiliation(s)
- Tetsuya Kotani
- Department of Medical Genome Sciences, Graduate School of Frontier Sciences, University of Tokyo, 5-1-5, Kashiwanoha, Kashiwa-shi, Chiba 277-8562, Japan
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31
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Funes S, Westerburg H, Jaimes-Miranda F, Woellhaf MW, Aguilar-Lopez JL, Janßen L, Bonnefoy N, Kauff F, Herrmann JM. Partial suppression of Oxa1 mutants by mitochondria-targeted signal recognition particle provides insights into the evolution of the cotranslational insertion systems. FEBS J 2013. [PMID: 23198851 DOI: 10.1111/febs.12082] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The biogenesis of hydrophobic membrane proteins involves their cotranslational membrane integration in order to prevent their unproductive aggregation. In the cytosol of bacteria and eukaryotes, membrane targeting of ribosomes that synthesize membrane proteins is achieved by signal recognition particles (SRPs) and their cognate membrane-bound receptors. As is evident from the genomes of fully sequenced eukaryotes, mitochondria generally lack an SRP system. Instead, mitochondrial ribosomes are physically associated with the protein insertion machinery in the inner membrane. Accordingly, deletion of ribosome-binding sites on the Oxa1 insertase and the Mba1 ribosome receptor in yeast leads to severe defects in cotranslational protein insertion and results in respiration-deficient mutants. In this study, we expressed mitochondria-targeted versions of the bacterial SRP protein Ffh and its receptor FtsY in these yeast mutants. Interestingly, Ffh was found to bind to the large subunit of mitochondrial ribosomes, and could relieve, to some degree, the defect of these insertion mutants. Although FtsY could also bind to mitochondrial membranes, it did not improve membrane protein biogenesis in this strain, presumably because of its inability to interact with Ffh. Hence, mitochondrial ribosomes are still able to interact physically and functionally with the bacterial SRP system. Our observations are consistent with a model according to which the protein insertion system in mitochondria evolved in three steps. The loss of genes for hydrophilic polypeptides (step 1) allowed the development of ribosome-binding sites on membrane proteins (step 2), which finally made the existence of an SRP-mediated system dispensable (step 3).
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Affiliation(s)
- Soledad Funes
- Departamento de Genética Molecular, Instituto de Fisiología Celular, Ciudad Universitaria, Universidad Nacional Autónoma de México, Distrito Federal, Mexico.
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Agrawal RK, Sharma MR. Structural aspects of mitochondrial translational apparatus. Curr Opin Struct Biol 2012; 22:797-803. [PMID: 22959417 DOI: 10.1016/j.sbi.2012.08.003] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2012] [Revised: 08/13/2012] [Accepted: 08/15/2012] [Indexed: 10/27/2022]
Abstract
During the last decade groundbreaking progress has been made towards the understanding of structure and function of cell's translational machinery. Cryo-electron microscopic (cryo-EM) and X-ray crystallographic structures of cytoplasmic ribosomes from several bacterial and eukaryotic species are now available in various ligand-bound states. Significant advances have also been made in structural studies on ribosomes of the cellular organelles, such as those present in the chloroplasts and mitochondria, using cryo-EM techniques. Here we review the progress made in structure determination of the mitochondrial ribosomes, with an emphasis on the mammalian mitochondrial ribosome and one of its translation initiation factors, and discuss challenges that lie ahead in obtaining their high-resolution structures.
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Affiliation(s)
- Rajendra K Agrawal
- Division of Translational Medicine, Wadsworth Center, New York State Department of Health, Albany, NY 12201-0509, United States.
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Christian BE, Spremulli LL. Mechanism of protein biosynthesis in mammalian mitochondria. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2011; 1819:1035-54. [PMID: 22172991 DOI: 10.1016/j.bbagrm.2011.11.009] [Citation(s) in RCA: 135] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/15/2011] [Revised: 11/03/2011] [Accepted: 11/08/2011] [Indexed: 01/25/2023]
Abstract
Protein synthesis in mammalian mitochondria produces 13 proteins that are essential subunits of the oxidative phosphorylation complexes. This review provides a detailed outline of each phase of mitochondrial translation including initiation, elongation, termination, and ribosome recycling. The roles of essential proteins involved in each phase are described. All of the products of mitochondrial protein synthesis in mammals are inserted into the inner membrane. Several proteins that may help bind ribosomes to the membrane during translation are described, although much remains to be learned about this process. Mutations in mitochondrial or nuclear genes encoding components of the translation system often lead to severe deficiencies in oxidative phosphorylation, and a summary of these mutations is provided. This article is part of a Special Issue entitled: Mitochondrial Gene Expression.
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Affiliation(s)
- Brooke E Christian
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
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Daoud R, Forget L, Lang BF. Yeast mitochondrial RNase P, RNase Z and the RNA degradosome are part of a stable supercomplex. Nucleic Acids Res 2011; 40:1728-36. [PMID: 22034500 PMCID: PMC3287206 DOI: 10.1093/nar/gkr941] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Initial steps in the synthesis of functional tRNAs require 5'- and 3'-processing of precursor tRNAs (pre-tRNAs), which in yeast mitochondria are achieved by two endonucleases, RNase P and RNase Z. In this study, using a combination of detergent-free Blue Native Gel Electrophoresis, proteomics and in vitro testing of pre-tRNA maturation, we reveal the physical association of these plus other mitochondrial activities in a large, stable complex of 136 proteins. It contains a total of seven proteins involved in RNA processing including RNase P and RNase Z, five out of six subunits of the mitochondrial RNA degradosome, components of the fatty acid synthesis pathway, translation, metabolism and protein folding. At the RNA level, there are the small and large rRNA subunits and RNase P RNA. Surprisingly, this complex is absent in an oar1Δ deletion mutant of the type II fatty acid synthesis pathway, supporting a recently published functional link between pre-tRNA processing and the FAS II pathway--apparently by integration into a large complex as we demonstrate here. Finally, the question of mt-RNase P localization within mitochondria was investigated, by GFP-tracing of a known protein subunit (Rpm2p). We find that about equal fractions of RNase P are soluble versus membrane-attached.
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Affiliation(s)
- Rachid Daoud
- Robert-Cedergren Centre for Bioinformatics and Genomics, Department of Biochemistry, Université de Montréal, 2900 Edouard-Montpetit, Montreal, Quebec H3T 1J4, Canada
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Haque ME, Koc H, Cimen H, Koc EC, Spremulli LL. Contacts between mammalian mitochondrial translational initiation factor 3 and ribosomal proteins in the small subunit. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2011; 1814:1779-84. [PMID: 22015679 DOI: 10.1016/j.bbapap.2011.09.013] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/12/2011] [Revised: 09/26/2011] [Accepted: 09/28/2011] [Indexed: 11/18/2022]
Abstract
Mammalian mitochondrial translational initiation factor 3 (IF3(mt)) binds to the small subunit of the ribosome displacing the large subunit during the initiation of protein biosynthesis. About half of the proteins in mitochondrial ribosomes have homologs in bacteria while the remainder are unique to the mitochondrion. To obtain information on the ribosomal proteins located near the IF3(mt) binding site, cross-linking studies were carried out followed by identification of the cross-linked proteins by mass spectrometry. IF3(mt) cross-links to mammalian mitochondrial homologs of the bacterial ribosomal proteins S5, S9, S10, and S18-2 and to unique mitochondrial ribosomal proteins MRPS29, MRPS32, MRPS36 and PTCD3 (Pet309) which has now been identified as a small subunit ribosomal protein. IF3(mt) has extensions on both the N- and C-termini compared to the bacterial factors. Cross-linking of a truncated derivative lacking these extensions gives the same hits as the full length IF3(mt) except that no cross-links were observed to MRPS36. IF3 consists of two domains separated by a flexible linker. Cross-linking of the isolated N- and C-domains was observed to a range of ribosomal proteins particularly with the C-domain carrying the linker which showed significant cross-linking to several ribosomal proteins not found in prokaryotes.
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MESH Headings
- Animals
- Cattle
- Eukaryotic Initiation Factor-3/chemistry
- Eukaryotic Initiation Factor-3/genetics
- Eukaryotic Initiation Factor-3/metabolism
- Humans
- Mammals/genetics
- Mammals/metabolism
- Mitochondrial Proteins/chemistry
- Mitochondrial Proteins/genetics
- Mitochondrial Proteins/metabolism
- Models, Biological
- Models, Molecular
- Peptide Chain Initiation, Translational/genetics
- Protein Binding
- Protein Interaction Mapping
- Protein Structure, Secondary
- Ribosomal Proteins/chemistry
- Ribosomal Proteins/genetics
- Ribosomal Proteins/metabolism
- Ribosome Subunits, Small, Eukaryotic/chemistry
- Ribosome Subunits, Small, Eukaryotic/genetics
- Ribosome Subunits, Small, Eukaryotic/metabolism
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Affiliation(s)
- Md Emdadul Haque
- Department of Chemistry, University of North Carolina, Chapel Hill, NC 27599-3290, USA
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Kaur J, Stuart RA. Truncation of the Mrp20 protein reveals new ribosome-assembly subcomplex in mitochondria. EMBO Rep 2011; 12:950-5. [PMID: 21779004 DOI: 10.1038/embor.2011.133] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2011] [Revised: 06/08/2011] [Accepted: 06/09/2011] [Indexed: 12/30/2022] Open
Abstract
Mitochondrial ribosomal protein 20 (Mrp20) is a component of the yeast mitochondrial large (54S) ribosomal subunit and is homologous to the bacterial L23 protein, located at the ribosomal tunnel exit site. The carboxy-terminal mitochondrial-specific domain of Mrp20 was found to have a crucial role in the assembly of the ribosomes. A new, membrane-bound, ribosomal-assembly subcomplex composed of known tunnel-exit-site proteins, an uncharacterized ribosomal protein, MrpL25, and the mitochondrial peroxiredoxin (Prx), Prx1, accumulates in an mrp20ΔC yeast mutant. Finally, data supporting the idea that the inner mitochondrial membrane acts as a platform for the ribosome assembly process are discussed.
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Affiliation(s)
- Jasvinder Kaur
- Department of Biological Sciences, Marquette University, Milwaukee, Wisconsin 53233, USA
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37
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Rötig A. Human diseases with impaired mitochondrial protein synthesis. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2011; 1807:1198-205. [DOI: 10.1016/j.bbabio.2011.06.010] [Citation(s) in RCA: 100] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/18/2011] [Revised: 06/03/2011] [Accepted: 06/06/2011] [Indexed: 10/18/2022]
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Lupo D, Vollmer C, Deckers M, Mick DU, Tews I, Sinning I, Rehling P. Mdm38 is a 14-3-3-like receptor and associates with the protein synthesis machinery at the inner mitochondrial membrane. Traffic 2011; 12:1457-66. [PMID: 21718401 DOI: 10.1111/j.1600-0854.2011.01239.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Mitochondrial ribosomes synthesize core subunits of the inner membrane respiratory chain complexes. In mitochondria, translation is regulated by mRNA-specific activator proteins and occurs on membrane-associated ribosomes. Mdm38/Letm1 is a conserved membrane receptor for mitochondrial ribosomes and specifically involved in respiratory chain biogenesis. In addition, Mdm38 and its higher eukaryotic homolog Letm1, function as K(+)/H(+) or Ca(2+)/H(+) antiporters in the inner membrane. Here, we identify the conserved ribosome-binding domain (RBD) of Mdm38 and determine the crystal structure at 2.1 Å resolution. Surprisingly, Mdm38(RBD) displays a 14-3-3-like fold despite any similarity to 14-3-3-proteins at the primary sequence level and thus represents the first 14-3-3-like protein in mitochondria. The 14-3-3-like domain is critical for respiratory chain assembly through regulation of Cox1 and Cytb translation. We show that this function can be spatially separated from the ion transport activity of the membrane integrated portion of Mdm38. On the basis of the phenotypes observed for mdm38Δ as compared to Mdm38 lacking the RBD, we suggest a model that combining ion transport and translational regulation into one molecule allows for direct coupling of ion flux across the inner membrane, and serves as a signal for the translation of mitochondrial membrane proteins via its direct association with the protein synthesis machinery.
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Affiliation(s)
- Domenico Lupo
- Biochemie-Zentrum der Universität Heidelberg, INF328, Heidelberg 69120, Germany
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39
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Haque ME, Spremulli LL, Fecko CJ. Identification of protein-protein and protein-ribosome interacting regions of the C-terminal tail of human mitochondrial inner membrane protein Oxa1L. J Biol Chem 2010; 285:34991-8. [PMID: 20739282 DOI: 10.1074/jbc.m110.163808] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The mammalian mitochondrial inner membrane protein Oxa1L is involved in the insertion of a number of mitochondrial translation products into the inner membrane. During this process, the C-terminal tail of Oxa1L (Oxa1L-CTT) binds mitochondrial ribosomes and is believed to coordinate the synthesis and membrane insertion of the nascent chains into the membrane. The C-terminal tail of Oxa1L does not contain any Cys residues. Four variants of this protein with a specifically placed Cys residue at position 4, 39, 67, or 94 of Oxa1L-CTT have been prepared. These Cys residues have been derivatized with a fluorescent probe, tetramethylrhodamine-5-maleimide, for biophysical studies. Oxa1L-CTT forms oligomers cooperatively with a binding constant in the submicromolar range. Fluorescence anisotropy and fluorescence lifetime measurements indicate that contacts near a long helix close to position 39 of Oxa1L-CTT occur during oligomer formation. Fluorescence correlation spectroscopy measurements demonstrate that all of the Oxa1L-CTT derivatives bind to mammalian mitochondrial ribosomes. Steady-state fluorescence quenching and fluorescence lifetime data indicate that there are extensive contacts between Oxa1L-CTT and the ribosome-encompassing regions around positions 39, 67, and 94. The results of this study suggest that Oxa1L-CTT undergoes conformational changes and induced oligomer formation when it binds to the ribosome.
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Affiliation(s)
- Md Emdadul Haque
- Department of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599-3290, USA
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40
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Mitochondrial translation and beyond: processes implicated in combined oxidative phosphorylation deficiencies. J Biomed Biotechnol 2010; 2010:737385. [PMID: 20396601 PMCID: PMC2854570 DOI: 10.1155/2010/737385] [Citation(s) in RCA: 144] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2009] [Accepted: 01/29/2010] [Indexed: 12/22/2022] Open
Abstract
Mitochondrial disorders are a heterogeneous group of often multisystemic and early fatal diseases, which are amongst the most common inherited human diseases. These disorders are caused by defects in the oxidative phosphorylation (OXPHOS) system, which comprises five multisubunit enzyme complexes encoded by both the nuclear and the mitochondrial genomes. Due to the multitude of proteins and intricacy of the processes required for a properly functioning OXPHOS system, identifying the genetic defect that underlies an OXPHOS deficiency is not an easy task, especially in the case of combined OXPHOS defects. In the present communication we give an extensive overview of the proteins and processes (in)directly involved in mitochondrial translation and the biogenesis of the OXPHOS system and their roles in combined OXPHOS deficiencies. This knowledge is important for further research into the genetic causes, with the ultimate goal to effectively prevent and cure these complex and often devastating disorders.
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41
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Aamann MD, Sorensen MM, Hvitby C, Berquist BR, Muftuoglu M, Tian J, de Souza-Pinto NC, Scheibye-Knudsen M, Wilson DM, Stevnsner T, Bohr VA. Cockayne syndrome group B protein promotes mitochondrial DNA stability by supporting the DNA repair association with the mitochondrial membrane. FASEB J 2010; 24:2334-46. [PMID: 20181933 DOI: 10.1096/fj.09-147991] [Citation(s) in RCA: 111] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Cockayne syndrome (CS) is a human premature aging disorder associated with severe developmental deficiencies and neurodegeneration, and phenotypically it resembles some mitochondrial DNA (mtDNA) diseases. Most patients belong to complementation group B, and the CS group B (CSB) protein plays a role in genomic maintenance and transcriptome regulation. By immunocytochemistry, mitochondrial fractionation, and Western blotting, we demonstrate that CSB localizes to mitochondria in different types of cells, with increased mitochondrial distribution following menadione-induced oxidative stress. Moreover, our results suggest that CSB plays a significant role in mitochondrial base excision repair (BER) regulation. In particular, we find reduced 8-oxo-guanine, uracil, and 5-hydroxy-uracil BER incision activities in CSB-deficient cells compared to wild-type cells. This deficiency correlates with deficient association of the BER activities with the mitochondrial inner membrane, suggesting that CSB may participate in the anchoring of the DNA repair complex. Increased mutation frequency in mtDNA of CSB-deficient cells demonstrates functional significance of the presence of CSB in the mitochondria. The results in total suggest that CSB plays a direct role in mitochondrial BER by helping recruit, stabilize, and/or retain BER proteins in repair complexes associated with the inner mitochondrial membrane, perhaps providing a novel basis for understanding the complex phenotype of this debilitating disorder.
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Affiliation(s)
- Maria D Aamann
- Laboratory of Molecular Gerontology, National Institute on Aging, NIH, 5600 Nathan Shock Dr., Baltimore, MD 21224, USA
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42
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Piao L, Li Y, Kim SJ, Byun HS, Huang SM, Hwang SK, Yang KJ, Park KA, Won M, Hong J, Hur GM, Seok JH, Shong M, Cho MH, Brazil DP, Hemmings BA, Park J. Association of LETM1 and MRPL36 contributes to the regulation of mitochondrial ATP production and necrotic cell death. Cancer Res 2009; 69:3397-404. [PMID: 19318571 DOI: 10.1158/0008-5472.can-08-3235] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Leucine zipper/EF hand-containing transmembrane-1 (LETM1) is a mitochondrial inner membrane protein that was first identified in Wolf-Hirschhorn syndrome, and was deleted in nearly all patients with the syndrome. LETM1 encodes for the human homologue of yeast Mdm38p, which is a mitochondria-shaping protein of unclear function. Here, we describe LETM1-mediated regulation of mitochondrial ATP production and biogenesis. We show that LETM1 overexpression can induce necrotic cell death in HeLa cells, in which LETM1 reduces mitochondrial biogenesis and ATP production. LETM1 acts as an anchor protein and associates with mitochondrial ribosome protein L36. Adenovirus-mediated overexpression of LETM1 reduced mitochondrial mass and expression of many mitochondrial proteins. LETM1-mediated inhibition of mitochondrial biogenesis enhanced glycolytic ATP supply and activated protein kinase B activity and cell survival signaling. The expression levels of LETM1 were significantly increased in multiple human cancer tissues compared with normals. These data suggest that LETM1 serves as an anchor protein for complex formation with the mitochondrial ribosome and regulates mitochondrial biogenesis. The increased expression of LETM1 in human cancer suggests that dysregulation of LETM1 is a key feature of tumorigenesis.
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Affiliation(s)
- Longzhen Piao
- Department of Pharmacology, Daejeon Regional Cancer Center, Cancer Research Institute, Research Institute for Medical Sciences, South Korea
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43
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Nozaki Y, Matsunaga N, Ishizawa T, Ueda T, Takeuchi N. HMRF1L is a human mitochondrial translation release factor involved in the decoding of the termination codons UAA and UAG. Genes Cells 2008; 13:429-38. [PMID: 18429816 DOI: 10.1111/j.1365-2443.2008.01181.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
While all essential mammalian mitochondrial factors involved in the initiation and elongation phases of translation have been cloned and well characterized, little is known about the factors involved in the termination process. In the present work, we report the functional analysis of human mitochondrial translation release factors (RF). Here, we show that HMRF1, which had been previously denoted as a human mitochondrial RF, was inactive in in vitro translation system, although it is a mitochondrial protein. Instead, we identified another human mitochondrial RF candidate, HMRF1L, and demonstrated that HMRF1L is indeed a mitochondrial protein that functions specifically as an RF for the decoding of mitochondrial UAA and UAG termination codons in vitro. The identification of the functional mitochondrial RF brings us much closer to a detailed understanding of the translational termination process in mammalian mitochondria as well as to the unraveling of the molecular mechanism of diseases caused by the dys-regulation of translational termination in human mitochondria.
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Affiliation(s)
- Yusuke Nozaki
- Department of Medical Genome Sciences, Graduate School of Frontier Sciences, University of Tokyo, Building FSB-401, 5-1-5, Kashiwanoha, Kashiwa, Chiba Prefecture 277-8562, Japan
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44
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Bogenhagen DF, Rousseau D, Burke S. The layered structure of human mitochondrial DNA nucleoids. J Biol Chem 2007; 283:3665-3675. [PMID: 18063578 DOI: 10.1074/jbc.m708444200] [Citation(s) in RCA: 316] [Impact Index Per Article: 18.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Mitochondrial DNA (mtDNA) occurs in cells in nucleoids containing several copies of the genome. Previous studies have identified proteins associated with these large DNA structures when they are biochemically purified by sedimentation and immunoaffinity chromatography. In this study, formaldehyde cross-linking was performed to determine which nucleoid proteins are in close contact with the mtDNA. A set of core nucleoid proteins is found in both native and cross-linked nucleoids, including 13 proteins with known roles in mtDNA transactions. Several other metabolic proteins and chaperones identified in native nucleoids, including ATAD3, were not observed to cross-link to mtDNA. Additional immunofluorescence and protease susceptibility studies showed that an N-terminal domain of ATAD3 previously proposed to bind to the mtDNA D-loop is directed away from the mitochondrial matrix, so it is unlikely to interact with mtDNA in vivo. These results are discussed in relation to a model for a layered structure of mtDNA nucleoids in which replication and transcription occur in the central core, whereas translation and complex assembly may occur in the peripheral region.
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Affiliation(s)
- Daniel F Bogenhagen
- Department of Pharmacological Sciences, State University of New York at Stony Brook, Stony Brook, New York 11794-8651.
| | - Denis Rousseau
- Laboratoire Biochimie et Biophysique des Systèmes Intégrés p438B, Institut de Recherches en Technologies et Sciences pour le Vivant, UMR5092 CNRS-UJF-CEA-Grenoble, 17 Rue des Martyrs, 38054 Grenoble Cedex 09, France
| | - Stephanie Burke
- Department of Pharmacological Sciences, State University of New York at Stony Brook, Stony Brook, New York 11794-8651
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45
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Soleimanpour-Lichaei HR, Kühl I, Gaisne M, Passos JF, Wydro M, Rorbach J, Temperley R, Bonnefoy N, Tate W, Lightowlers R, Chrzanowska-Lightowlers Z. mtRF1a is a human mitochondrial translation release factor decoding the major termination codons UAA and UAG. Mol Cell 2007; 27:745-57. [PMID: 17803939 PMCID: PMC1976341 DOI: 10.1016/j.molcel.2007.06.031] [Citation(s) in RCA: 92] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2007] [Revised: 05/30/2007] [Accepted: 06/21/2007] [Indexed: 11/28/2022]
Abstract
Human mitochondria contain their own genome, encoding 13 polypeptides that are synthesized within the organelle. The molecular processes that govern and facilitate this mitochondrial translation remain unclear. Many key factors have yet to be characterized—for example, those required for translation termination. All other systems have two classes of release factors that either promote codon-specific hydrolysis of peptidyl-tRNA (class I) or lack specificity but stimulate the dissociation of class I factors from the ribosome (class II). One human mitochondrial protein has been previously identified in silico as a putative member of the class I release factors. Although we could not confirm the function of this factor, we report the identification of a different mitochondrial protein, mtRF1a, that is capable in vitro and in vivo of terminating translation at UAA/UAG codons. Further, mtRF1a depletion in HeLa cells led to compromised growth in galactose and increased production of reactive oxygen species.
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Affiliation(s)
| | - Inge Kühl
- Centre de Génétique Moléculaire, CNRS Batiment 26, Avenue de la Terrasse, 91198 Gif sur Yvette Cedex, France
| | - Mauricette Gaisne
- Centre de Génétique Moléculaire, CNRS Batiment 26, Avenue de la Terrasse, 91198 Gif sur Yvette Cedex, France
| | - Joao F. Passos
- Centre for Integrated Systems Biology of Ageing and Nutrition, Newcastle University, Newcastle upon Tyne NE4 6BE, UK
| | - Mateusz Wydro
- Mitochondrial Research Group, Newcastle University, Framlington Place, Newcastle upon Tyne NE2 4HH, UK
| | - Joanna Rorbach
- Mitochondrial Research Group, Newcastle University, Framlington Place, Newcastle upon Tyne NE2 4HH, UK
| | - Richard Temperley
- Mitochondrial Research Group, Newcastle University, Framlington Place, Newcastle upon Tyne NE2 4HH, UK
| | - Nathalie Bonnefoy
- Centre de Génétique Moléculaire, CNRS Batiment 26, Avenue de la Terrasse, 91198 Gif sur Yvette Cedex, France
| | - Warren Tate
- Department of Biochemistry, University of Otago, P.O. Box 56, 710 Cumberland Street, Dunedin 9016, New Zealand
| | - Robert Lightowlers
- Mitochondrial Research Group, Newcastle University, Framlington Place, Newcastle upon Tyne NE2 4HH, UK
| | - Zofia Chrzanowska-Lightowlers
- Mitochondrial Research Group, Newcastle University, Framlington Place, Newcastle upon Tyne NE2 4HH, UK
- Corresponding author
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Smits P, Smeitink JAM, van den Heuvel LP, Huynen MA, Ettema TJG. Reconstructing the evolution of the mitochondrial ribosomal proteome. Nucleic Acids Res 2007; 35:4686-703. [PMID: 17604309 PMCID: PMC1950548 DOI: 10.1093/nar/gkm441] [Citation(s) in RCA: 140] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
For production of proteins that are encoded by the mitochondrial genome, mitochondria rely on their own mitochondrial translation system, with the mitoribosome as its central component. Using extensive homology searches, we have reconstructed the evolutionary history of the mitoribosomal proteome that is encoded by a diverse subset of eukaryotic genomes, revealing an ancestral ribosome of alpha-proteobacterial descent that more than doubled its protein content in most eukaryotic lineages. We observe large variations in the protein content of mitoribosomes between different eukaryotes, with mammalian mitoribosomes sharing only 74 and 43% of its proteins with yeast and Leishmania mitoribosomes, respectively. We detected many previously unidentified mitochondrial ribosomal proteins (MRPs) and found that several have increased in size compared to their bacterial ancestral counterparts by addition of functional domains. Several new MRPs have originated via duplication of existing MRPs as well as by recruitment from outside of the mitoribosomal proteome. Using sensitive profile-profile homology searches, we found hitherto undetected homology between bacterial and eukaryotic ribosomal proteins, as well as between fungal and mammalian ribosomal proteins, detecting two novel human MRPs. These newly detected MRPs constitute, along with evolutionary conserved MRPs, excellent new screening targets for human patients with unresolved mitochondrial oxidative phosphorylation disorders.
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Affiliation(s)
- Paulien Smits
- Nijmegen Center for Mitochondrial Disorders, Nijmegen Center for Molecular Life Sciences, Radboud University Nijmegen Medical Center, Geert–Grooteplein-Zuid 10 and Center for Molecular and Biomolecular Informatics, Nijmegen Center for Molecular Life Sciences, Radboud University Nijmegen Medical Center, Geert-Grooteplein 28, 6525 GA Nijmegen, The Netherlands
| | - Jan A. M. Smeitink
- Nijmegen Center for Mitochondrial Disorders, Nijmegen Center for Molecular Life Sciences, Radboud University Nijmegen Medical Center, Geert–Grooteplein-Zuid 10 and Center for Molecular and Biomolecular Informatics, Nijmegen Center for Molecular Life Sciences, Radboud University Nijmegen Medical Center, Geert-Grooteplein 28, 6525 GA Nijmegen, The Netherlands
| | - Lambert P. van den Heuvel
- Nijmegen Center for Mitochondrial Disorders, Nijmegen Center for Molecular Life Sciences, Radboud University Nijmegen Medical Center, Geert–Grooteplein-Zuid 10 and Center for Molecular and Biomolecular Informatics, Nijmegen Center for Molecular Life Sciences, Radboud University Nijmegen Medical Center, Geert-Grooteplein 28, 6525 GA Nijmegen, The Netherlands
| | - Martijn A. Huynen
- Nijmegen Center for Mitochondrial Disorders, Nijmegen Center for Molecular Life Sciences, Radboud University Nijmegen Medical Center, Geert–Grooteplein-Zuid 10 and Center for Molecular and Biomolecular Informatics, Nijmegen Center for Molecular Life Sciences, Radboud University Nijmegen Medical Center, Geert-Grooteplein 28, 6525 GA Nijmegen, The Netherlands
| | - Thijs J. G. Ettema
- Nijmegen Center for Mitochondrial Disorders, Nijmegen Center for Molecular Life Sciences, Radboud University Nijmegen Medical Center, Geert–Grooteplein-Zuid 10 and Center for Molecular and Biomolecular Informatics, Nijmegen Center for Molecular Life Sciences, Radboud University Nijmegen Medical Center, Geert-Grooteplein 28, 6525 GA Nijmegen, The Netherlands
- *To whom correspondence should be addressed.
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Wang Z, Cotney J, Shadel GS. Human mitochondrial ribosomal protein MRPL12 interacts directly with mitochondrial RNA polymerase to modulate mitochondrial gene expression. J Biol Chem 2007; 282:12610-8. [PMID: 17337445 PMCID: PMC2606046 DOI: 10.1074/jbc.m700461200] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
The core human mitochondrial transcription machinery comprises a single subunit bacteriophage-related RNA polymerase, POLRMT, the high mobility group box DNA-binding protein h-mtTFA/TFAM, and two transcriptional co-activator proteins, h-mtTFB1 and h-mtTFB2 that also have rRNA methyltransferase activity. Recapitulation of specific initiation of transcription in vitro can be achieved by a complex of POL-RMT, h-mtTFA, and either h-mtTFB1 or h-mtTFB2. However, the nature of mitochondrial transcription complexes in vivo and the potential involvement of additional proteins in the transcription process in human mitochondria have not been extensively investigated. In Saccharomyces cerevisiae, transcription and translation are physically coupled via the formation of a multiprotein complex nucleated by the binding of Nam1p to the amino-terminal domain of mtRNA polymerase (Rpo41p). This model system paradigm led us to search for proteins that interact with POLRMT to regulate mitochondrial gene expression in humans. Using an affinity capture strategy to identify POL-RMT-binding proteins, we identified mitochondrial ribosomal protein L7/L12 (MRPL12) as a protein in HeLa mitochondrial extracts that interacts specifically with POLRMT in vitro. Purified recombinant MRPL12 binds to POLRMT and stimulates mitochondrial transcription activity in vitro, demonstrating that this interaction is both direct and functional. Finally, from HeLa cells that overexpress FLAG epitope-tagged MRPL12, increased steady-state levels of mtDNA-encoded transcripts are observed and MRPL12-POLRMT complexes can be co-immunoprecipitated, providing strong evidence that this interaction enhances mitochondrial transcription or RNA stability in vivo. We speculate that the MRPL12 interaction with POLRMT is likely part of a novel regulatory mechanism that coordinates mitochondrial transcription with translation and/or ribosome biogenesis during human mitochondrial gene expression.
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Affiliation(s)
- Zhibo Wang
- Department of Pathology, Yale University School of Medicine, New Haven, Connecticut 06520-8023
| | - Justin Cotney
- Department of Pathology, Yale University School of Medicine, New Haven, Connecticut 06520-8023
- Graduate Program in Genetics and Molecular Biology, Emory University School of Medicine, Atlanta, Georgia 30322-3050
| | - Gerald S. Shadel
- Department of Pathology, Yale University School of Medicine, New Haven, Connecticut 06520-8023
- To whom correspondence should be addressed: Dept. of Pathology, Yale University School of Medicine, 310 Cedar St., P. O. Box 208023, New Haven, CT 06520-8023. Tel.: 203-785-2475; Fax: 203-785-2628; E-mail:
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Abstract
The preparation of mammalian mitochondrial ribosomes in sufficient quantities for biochemical studies is best done beginning with whole tissue rather than from cells in culture. This issue arises because of the low abundance of these ribosomes in cells, making their isolation a challenge. Crude mitochondrial preparations are made by differential centrifugation and are treated with digitonin to remove the outer membrane. This treatment also effectively removes most contamination by cytoplasmic ribosomes. Purification of mammalian mitochondrial ribosomes requires treatment with detergents to release the ribosomes from their association with the membrane. Sucrose density gradient centrifugation is used to separate the ribosomes from other large oligomeric complexes from this organelle.
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Affiliation(s)
- Linda L Spremulli
- Department of Chemistry, University of North Carolina, Chapel Hill, USA
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Suzuki H, Ueda T, Taguchi H, Takeuchi N. Chaperone properties of mammalian mitochondrial translation elongation factor Tu. J Biol Chem 2006; 282:4076-84. [PMID: 17130126 DOI: 10.1074/jbc.m608187200] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The main function of the prokaryotic translation elongation factor Tu (EF-Tu) and its eukaryotic counterpart eEF1A is to deliver aminoacyl-tRNA to the A-site on the ribosome. In addition to this primary function, it has been reported that EF-Tu from various sources has chaperone activity. At present, little information is available about the chaperone activity of mitochondrial EF-Tu. In the present study, we have examined the chaperone function of mammalian mitochondrial EF-Tu (EF-Tumt). We demonstrate that recombinant EF-Tumt prevents thermal aggregation of proteins and enhances protein refolding in vitro and that this EF-Tumt chaperone activity proceeds in a GTP-independent manner. We also demonstrate that, under heat stress, the newly synthesized peptides from the mitochondrial ribosome specifically co-immunoprecipitate with EF-Tumt and are destabilized in EF-Tumt-overexpressing cells. We show that most of the EF-Tumt localizes on the mitochondrial inner membrane where most mitochondrial ribosomes are found. We discuss the possible role of EF-Tumt chaperone activity in protein quality control in mitochondria, with regard to the recently reported in vivo chaperone function of eEF1A.
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Affiliation(s)
- Hiroaki Suzuki
- Department of Medical Genome Sciences, Graduate School of Frontier Sciences, University of Tokyo, Building FSB-401, 5-1-5, Kashiwa, Chiba Prefecture 277-8562, Japan
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Everberg H, Leiding T, Schiöth A, Tjerneld F, Gustavsson N. Efficient and non-denaturing membrane solubilization combined with enrichment of membrane protein complexes by detergent/polymer aqueous two-phase partitioning for proteome analysis. J Chromatogr A 2006; 1122:35-46. [PMID: 16682048 DOI: 10.1016/j.chroma.2006.04.020] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2006] [Revised: 04/06/2006] [Accepted: 04/11/2006] [Indexed: 11/19/2022]
Abstract
It is of central interest in membrane proteomics to establish methods that combine efficient solubilization with enrichment of proteins and intact protein complexes. We have investigated the quantitative and qualitative solubilization efficiency of five commercially available detergents using mitochondria from the yeast Saccharomyces cerevisiae as model system. Combining the zwitterionic detergent Zwittergent 3-10 and the non-ionic detergent Triton X-114 resulted in a complementary solubilization of proteins, which was similar to that of the anionic detergent sodium dodecyl sulfate (SDS). The subsequent removal of soluble proteins by detergent/polymer two-phase system partitioning was further enhanced by addition of SDS and increasing pH. A large number of both integral and peripheral membrane protein subunits from mitochondrial membrane protein complexes were identified in the detergent phase. We suggest that the optimized solubilization protocol in combination with detergent/polymer two-phase partitioning is a mild and efficient method for initial enrichment of membrane proteins and membrane protein complexes in proteomic studies.
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Affiliation(s)
- Henrik Everberg
- Department of Biochemistry, Center for Chemistry and Chemical engineering, Lund University, P.O. Box 124, SE-22100 Lund, Sweden
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