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Caron-Godon CA, Collington E, Wolf JL, Coletta G, Glerum DM. More than Just Bread and Wine: Using Yeast to Understand Inherited Cytochrome Oxidase Deficiencies in Humans. Int J Mol Sci 2024; 25:3814. [PMID: 38612624 PMCID: PMC11011759 DOI: 10.3390/ijms25073814] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2024] [Revised: 03/26/2024] [Accepted: 03/28/2024] [Indexed: 04/14/2024] Open
Abstract
Inherited defects in cytochrome c oxidase (COX) are associated with a substantial subset of diseases adversely affecting the structure and function of the mitochondrial respiratory chain. This multi-subunit enzyme consists of 14 subunits and numerous cofactors, and it requires the function of some 30 proteins to assemble. COX assembly was first shown to be the primary defect in the majority of COX deficiencies 36 years ago. Over the last three decades, most COX assembly genes have been identified in the yeast Saccharomyces cerevisiae, and studies in yeast have proven instrumental in testing the impact of mutations identified in patients with a specific COX deficiency. The advent of accessible genome-wide sequencing capabilities has led to more patient mutations being identified, with the subsequent identification of several new COX assembly factors. However, the lack of genotype-phenotype correlations and the large number of genes involved in generating a functional COX mean that functional studies must be undertaken to assign a genetic variant as being causal. In this review, we provide a brief overview of the use of yeast as a model system and briefly compare the COX assembly process in yeast and humans. We focus primarily on the studies in yeast that have allowed us to both identify new COX assembly factors and to demonstrate the pathogenicity of a subset of the mutations that have been identified in patients with inherited defects in COX. We conclude with an overview of the areas in which studies in yeast are likely to continue to contribute to progress in understanding disease arising from inherited COX deficiencies.
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Affiliation(s)
- Chenelle A. Caron-Godon
- Department of Biology, University of Waterloo, Waterloo, ON N2L 3G1, Canada; (C.A.C.-G.); (E.C.); (J.L.W.); (G.C.)
| | - Emma Collington
- Department of Biology, University of Waterloo, Waterloo, ON N2L 3G1, Canada; (C.A.C.-G.); (E.C.); (J.L.W.); (G.C.)
| | - Jessica L. Wolf
- Department of Biology, University of Waterloo, Waterloo, ON N2L 3G1, Canada; (C.A.C.-G.); (E.C.); (J.L.W.); (G.C.)
| | - Genna Coletta
- Department of Biology, University of Waterloo, Waterloo, ON N2L 3G1, Canada; (C.A.C.-G.); (E.C.); (J.L.W.); (G.C.)
| | - D. Moira Glerum
- Department of Biology, University of Waterloo, Waterloo, ON N2L 3G1, Canada; (C.A.C.-G.); (E.C.); (J.L.W.); (G.C.)
- Waterloo Institute for Nanotechnology, University of Waterloo, Waterloo, ON N2L 3G1, Canada
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Key J, Gispert S, Koepf G, Steinhoff-Wagner J, Reichlmeir M, Auburger G. Translation Fidelity and Respiration Deficits in CLPP-Deficient Tissues: Mechanistic Insights from Mitochondrial Complexome Profiling. Int J Mol Sci 2023; 24:17503. [PMID: 38139332 PMCID: PMC10743472 DOI: 10.3390/ijms242417503] [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: 11/13/2023] [Revised: 12/07/2023] [Accepted: 12/08/2023] [Indexed: 12/24/2023] Open
Abstract
The mitochondrial matrix peptidase CLPP is crucial during cell stress. Its loss causes Perrault syndrome type 3 (PRLTS3) with infertility, neurodegeneration, and a growth deficit. Its target proteins are disaggregated by CLPX, which also regulates heme biosynthesis via unfolding ALAS enzymes, providing access for pyridoxal-5'-phosphate (PLP). Despite efforts in diverse organisms with multiple techniques, CLPXP substrates remain controversial. Here, avoiding recombinant overexpression, we employed complexomics in mitochondria from three mouse tissues to identify endogenous targets. A CLPP absence caused the accumulation and dispersion of CLPX-VWA8 as AAA+ unfoldases, and of PLPBP. Similar changes and CLPX-VWA8 co-migration were evident for mitoribosomal central protuberance clusters, translation factors like GFM1-HARS2, the RNA granule components LRPPRC-SLIRP, and enzymes OAT-ALDH18A1. Mitochondrially translated proteins in testes showed reductions to <30% for MTCO1-3, the mis-assembly of the complex IV supercomplex, and accumulated metal-binding assembly factors COX15-SFXN4. Indeed, heavy metal levels were increased for iron, molybdenum, cobalt, and manganese. RT-qPCR showed compensatory downregulation only for Clpx mRNA; most accumulated proteins appeared transcriptionally upregulated. Immunoblots validated VWA8, MRPL38, MRPL18, GFM1, and OAT accumulation. Co-immunoprecipitation confirmed CLPX binding to MRPL38, GFM1, and OAT, so excess CLPX and PLP may affect their activity. Our data mechanistically elucidate the mitochondrial translation fidelity deficits which underlie progressive hearing impairment in PRLTS3.
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Affiliation(s)
- Jana Key
- Goethe University Frankfurt, University Hospital, Clinic of Neurology, Exp. Neurology, Heinrich Hoffmann Str. 7, 60590 Frankfurt am Main, Germany; (S.G.); (M.R.); (G.A.)
| | - Suzana Gispert
- Goethe University Frankfurt, University Hospital, Clinic of Neurology, Exp. Neurology, Heinrich Hoffmann Str. 7, 60590 Frankfurt am Main, Germany; (S.G.); (M.R.); (G.A.)
| | - Gabriele Koepf
- Goethe University Frankfurt, University Hospital, Clinic of Neurology, Exp. Neurology, Heinrich Hoffmann Str. 7, 60590 Frankfurt am Main, Germany; (S.G.); (M.R.); (G.A.)
| | - Julia Steinhoff-Wagner
- TUM School of Life Sciences, Animal Nutrition and Metabolism, Technical University of Munich, Liesel-Beckmann-Str. 2, 85354 Freising-Weihenstephan, Germany;
| | - Marina Reichlmeir
- Goethe University Frankfurt, University Hospital, Clinic of Neurology, Exp. Neurology, Heinrich Hoffmann Str. 7, 60590 Frankfurt am Main, Germany; (S.G.); (M.R.); (G.A.)
| | - Georg Auburger
- Goethe University Frankfurt, University Hospital, Clinic of Neurology, Exp. Neurology, Heinrich Hoffmann Str. 7, 60590 Frankfurt am Main, Germany; (S.G.); (M.R.); (G.A.)
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3
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Kanduc D. Exposure to SARS-CoV-2 and Infantile Diseases. Glob Med Genet 2023; 10:72-78. [PMID: 37144240 PMCID: PMC10154082 DOI: 10.1055/s-0043-1768699] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/06/2023] Open
Abstract
Background and Aim Immune response against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in newborns and children after prophylactic immunization is currently a relevant research topic. The present study analyzes the issue by examining the possibility that the anti-SARS-CoV-2 immune responses are not uniquely directed against the virus but can-via molecular mimicry and the consequent cross-reactivity-also hit human proteins involved in infantile diseases. Methods Human proteins that-if altered-associate with infantile disorders were searched for minimal immune pentapeptide determinants shared with SARS-CoV-2 spike glycoprotein (gp). Then, the shared pentapeptides were analyzed for immunologic potential and immunologic imprinting phenomena. Results Comparative sequence analysis shows that: (1) numerous pentapeptides (namely, 54) are common to SARS-CoV-2 spike gp and human proteins that, when altered, are linked to infantile diseases; (2) all the shared peptides have an immunologic potential since they are present in experimentally validated SARS-CoV-2 spike gp-derived epitopes; and (3) many of the shared peptides are also hosted in infectious pathogens to which children can have already been exposed, thus making immunologic imprint phenomena feasible. Conclusion Molecular mimicry and the consequent cross-reactivity can represent the mechanism that connects exposure to SARS-CoV-2 and various pediatric diseases, with a fundamental role of the immunologic memory and the history of the child's infections in determining and specifying the immune response and the pathologic autoimmune sequela.
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Affiliation(s)
- Darja Kanduc
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari, Bari, Italy
- Address for correspondence Darja Kanduc, PhD Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari70126 BariItaly
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Gayathri N, Deepha S, Sharma S. Diagnosis of primary mitochondrial disorders -Emphasis on myopathological aspects. Mitochondrion 2021; 61:69-84. [PMID: 34592422 DOI: 10.1016/j.mito.2021.09.007] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2021] [Revised: 09/03/2021] [Accepted: 09/22/2021] [Indexed: 12/29/2022]
Abstract
Mitochondrial disorders are one of the most common neurometabolic disorders affecting all age groups. The phenotype-genotype heterogeneity in these disorders can be attributed to the dual genetic control on mitochondrial functions, posing a challenge for diagnosis. Though the advancement in the high-throughput sequencing and other omics platforms resulted in a "genetics-first" approach, the muscle biopsy remains the benchmark in most of the mitochondrial disorders. This review focuses on the myopathological aspects of primary mitochondrial disorders. The utility of muscle biopsy is not limited to analyse the structural abnormalities; rather it also proves to be a potential tool to understand the deranged sub-cellular functions.
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Affiliation(s)
- Narayanappa Gayathri
- Department of Neuropathology, National Institute of Mental Health and Neurosciences (NIMHANS), Bangalore 560 029, India.
| | - Sekar Deepha
- Department of Neuropathology, National Institute of Mental Health and Neurosciences (NIMHANS), Bangalore 560 029, India
| | - Shivani Sharma
- Department of Neuropathology, National Institute of Mental Health and Neurosciences (NIMHANS), Bangalore 560 029, India
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5
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Rivett ED, Heo L, Feig M, Hegg EL. Biosynthesis and trafficking of heme o and heme a: new structural insights and their implications for reaction mechanisms and prenylated heme transfer. Crit Rev Biochem Mol Biol 2021; 56:640-668. [PMID: 34428995 DOI: 10.1080/10409238.2021.1957668] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
Aerobic respiration is a key energy-producing pathway in many prokaryotes and virtually all eukaryotes. The final step of aerobic respiration is most commonly catalyzed by heme-copper oxidases embedded in the cytoplasmic or mitochondrial membrane. The majority of these terminal oxidases contain a prenylated heme (typically heme a or occasionally heme o) in the active site. In addition, many heme-copper oxidases, including mitochondrial cytochrome c oxidases, possess a second heme a cofactor. Despite the critical role of heme a in the electron transport chain, the details of the mechanism by which heme b, the prototypical cellular heme, is converted to heme o and then to heme a remain poorly understood. Recent structural investigations, however, have helped clarify some elements of heme a biosynthesis. In this review, we discuss the insight gained from these advances. In particular, we present a new structural model of heme o synthase (HOS) based on distance restraints from inferred coevolutionary relationships and refined by molecular dynamics simulations that are in good agreement with the experimentally determined structures of HOS homologs. We also analyze the two structures of heme a synthase (HAS) that have recently been solved by other groups. For both HOS and HAS, we discuss the proposed catalytic mechanisms and highlight how new insights into the heme-binding site locations shed light on previously obtained biochemical data. Finally, we explore the implications of the new structural data in the broader context of heme trafficking in the heme a biosynthetic pathway and heme-copper oxidase assembly.
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Affiliation(s)
- Elise D Rivett
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI, USA
| | - Lim Heo
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI, USA
| | - Michael Feig
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI, USA
| | - Eric L Hegg
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI, USA
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6
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Dietz JV, Fox JL, Khalimonchuk O. Down the Iron Path: Mitochondrial Iron Homeostasis and Beyond. Cells 2021; 10:cells10092198. [PMID: 34571846 PMCID: PMC8468894 DOI: 10.3390/cells10092198] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2021] [Revised: 08/22/2021] [Accepted: 08/23/2021] [Indexed: 12/20/2022] Open
Abstract
Cellular iron homeostasis and mitochondrial iron homeostasis are interdependent. Mitochondria must import iron to form iron–sulfur clusters and heme, and to incorporate these cofactors along with iron ions into mitochondrial proteins that support essential functions, including cellular respiration. In turn, mitochondria supply the cell with heme and enable the biogenesis of cytosolic and nuclear proteins containing iron–sulfur clusters. Impairment in cellular or mitochondrial iron homeostasis is deleterious and can result in numerous human diseases. Due to its reactivity, iron is stored and trafficked through the body, intracellularly, and within mitochondria via carefully orchestrated processes. Here, we focus on describing the processes of and components involved in mitochondrial iron trafficking and storage, as well as mitochondrial iron–sulfur cluster biogenesis and heme biosynthesis. Recent findings and the most pressing topics for future research are highlighted.
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Affiliation(s)
- Jonathan V. Dietz
- Department of Biochemistry, University of Nebraska, Lincoln, NE 68588, USA;
| | - Jennifer L. Fox
- Department of Chemistry and Biochemistry, College of Charleston, Charleston, SC 29424, USA;
| | - Oleh Khalimonchuk
- Department of Biochemistry, University of Nebraska, Lincoln, NE 68588, USA;
- Nebraska Redox Biology Center, University of Nebraska, Lincoln, NE 68588, USA
- Fred and Pamela Buffett Cancer Center, Omaha, NE 68198, USA
- Correspondence:
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7
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Zanfardino P, Doccini S, Santorelli FM, Petruzzella V. Tackling Dysfunction of Mitochondrial Bioenergetics in the Brain. Int J Mol Sci 2021; 22:8325. [PMID: 34361091 PMCID: PMC8348117 DOI: 10.3390/ijms22158325] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2021] [Revised: 07/29/2021] [Accepted: 07/30/2021] [Indexed: 12/15/2022] Open
Abstract
Oxidative phosphorylation (OxPhos) is the basic function of mitochondria, although the landscape of mitochondrial functions is continuously growing to include more aspects of cellular homeostasis. Thanks to the application of -omics technologies to the study of the OxPhos system, novel features emerge from the cataloging of novel proteins as mitochondrial thus adding details to the mitochondrial proteome and defining novel metabolic cellular interrelations, especially in the human brain. We focussed on the diversity of bioenergetics demand and different aspects of mitochondrial structure, functions, and dysfunction in the brain. Definition such as 'mitoexome', 'mitoproteome' and 'mitointeractome' have entered the field of 'mitochondrial medicine'. In this context, we reviewed several genetic defects that hamper the last step of aerobic metabolism, mostly involving the nervous tissue as one of the most prominent energy-dependent tissues and, as consequence, as a primary target of mitochondrial dysfunction. The dual genetic origin of the OxPhos complexes is one of the reasons for the complexity of the genotype-phenotype correlation when facing human diseases associated with mitochondrial defects. Such complexity clinically manifests with extremely heterogeneous symptoms, ranging from organ-specific to multisystemic dysfunction with different clinical courses. Finally, we briefly discuss the future directions of the multi-omics study of human brain disorders.
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Affiliation(s)
- Paola Zanfardino
- Department of Medical Basic Sciences, Neurosciences and Sense Organs, University of Bari Aldo Moro, 70124 Bari, Italy;
| | - Stefano Doccini
- IRCCS Fondazione Stella Maris, Calambrone, 56128 Pisa, Italy;
| | | | - Vittoria Petruzzella
- Department of Medical Basic Sciences, Neurosciences and Sense Organs, University of Bari Aldo Moro, 70124 Bari, Italy;
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8
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Iron supplementation regulates the progression of high fat diet induced obesity and hepatic steatosis via mitochondrial signaling pathways. Sci Rep 2021; 11:10753. [PMID: 34031430 PMCID: PMC8144192 DOI: 10.1038/s41598-021-89673-8] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2020] [Accepted: 04/23/2021] [Indexed: 12/04/2022] Open
Abstract
Disruption of iron metabolism is closely related to metabolic diseases. Iron deficiency is frequently associated with obesity and hepatic steatosis. However, the effects of iron supplementation on obesity and energy metabolism remain unclear. Here we show that a high-fat diet supplemented with iron reduces body weight gain and hepatic lipid accumulation in mice. Iron supplementation was found to reduce mitochondrial morphological abnormalities and upregulate gene transcription involved in mitochondrial function and beta oxidation in the liver and skeletal muscle. In both these tissues, iron supplementation increased the expression of genes involved in heme or iron–sulfur (Fe–S) cluster synthesis. Heme and Fe–S cluster, which are iron prosthetic groups contained in electron transport chain complex subunits, are essential for mitochondrial respiration. The findings of this study demonstrated that iron regulates mitochondrial signaling pathways—gene transcription of mitochondrial component molecules synthesis and their energy metabolism. Overall, the study elucidates the molecular basis underlying the relationship between iron supplementation and obesity and hepatic steatosis progression, and the role of iron as a signaling molecule.
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Galvão de Oliveira M, Tengan C, Micheletti C, Ramos de Macedo P, Soares Pinho Cernach MC, Cavole TR, de França Basto M, Filho JS, Virmond LA, Milanezi F, Nakano V, Falconi A, Perrone E. A novel variant in the COX15 gene causing a fatal infantile cardioencephalomyopathy: A case report with clinical and molecular review. Eur J Med Genet 2021; 64:104195. [PMID: 33746038 DOI: 10.1016/j.ejmg.2021.104195] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2020] [Revised: 03/04/2021] [Accepted: 03/14/2021] [Indexed: 10/21/2022]
Abstract
The cytochrome c-oxidase (COX) enzyme, also known as mitochondrial complex IV (MT-C4D), is a transmembrane protein complex found in mitochondria. COX deficiency is one of the most frequent causes of electron transport chain defects in humans. Therefore, high energy demand organs and tissues are affected in patients with mutations in the COX15 gene, with variable phenotypic expressiveness. We describe the case of a male newborn with hypertrophic cardiomyopathy and serum and cerebrospinal fluid hyperlacticaemia, whose exome sequencing revealed two variants in a compound heterozygous state: c.232G > A; p.(Gly78Arg), classified as likely pathogenic, and c.452C > G; p.(Ser151Ter), as pathogenic; the former never previously described in the literature.
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Affiliation(s)
| | - Célia Tengan
- Universidade Federal de São Paulo, Unifesp, Departamento de Neurologia, São Paulo, SP, CEP 04039-000, Brazil.
| | - Cecília Micheletti
- Universidade Federal de São Paulo, Unifesp, Departamento de Pediatria, São Paulo, SP, CEP 04023-060, Brazil.
| | - Paloma Ramos de Macedo
- Universidade Federal de São Paulo, Unifesp, Departamento de Neurologia, São Paulo, SP, CEP 04039-000, Brazil.
| | | | - Thiago Rodrigues Cavole
- Universidade Federal de São Paulo, Unifesp, Departamento de Genética, São Paulo, SP, CEP 04023-061, Brazil.
| | - Marina de França Basto
- Universidade Federal de São Paulo, Unifesp, Departamento de Genética, São Paulo, SP, CEP 04023-061, Brazil.
| | - Joselito Sobreira Filho
- Universidade Federal de São Paulo, Unifesp, Departamento de Genética, São Paulo, SP, CEP 04023-061, Brazil.
| | - Luiza Amaral Virmond
- Universidade Federal de São Paulo, Unifesp, Departamento de Genética, São Paulo, SP, CEP 04023-061, Brazil.
| | | | | | | | - Eduardo Perrone
- Universidade Federal de São Paulo, Unifesp, Departamento de Genética, São Paulo, SP, CEP 04023-061, Brazil.
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10
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Fernandez-Vizarra E, Zeviani M. Mitochondrial disorders of the OXPHOS system. FEBS Lett 2020; 595:1062-1106. [PMID: 33159691 DOI: 10.1002/1873-3468.13995] [Citation(s) in RCA: 91] [Impact Index Per Article: 22.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2020] [Revised: 10/21/2020] [Accepted: 11/01/2020] [Indexed: 12/13/2022]
Abstract
Mitochondrial disorders are among the most frequent inborn errors of metabolism, their primary cause being the dysfunction of the oxidative phosphorylation system (OXPHOS). OXPHOS is composed of the electron transport chain (ETC), formed by four multimeric enzymes and two mobile electron carriers, plus an ATP synthase [also called complex V (cV)]. The ETC performs the redox reactions involved in cellular respiration while generating the proton motive force used by cV to synthesize ATP. OXPHOS biogenesis involves multiple steps, starting from the expression of genes encoded in physically separated genomes, namely the mitochondrial and nuclear DNA, to the coordinated assembly of components and cofactors building each individual complex and eventually the supercomplexes. The genetic cause underlying around half of the diagnosed mitochondrial disease cases is currently known. Many of these cases result from pathogenic variants in genes encoding structural subunits or additional factors directly involved in the assembly of the ETC complexes. Here, we review the historical and most recent findings concerning the clinical phenotypes and the molecular pathological mechanisms underlying this particular group of disorders.
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Affiliation(s)
- Erika Fernandez-Vizarra
- Institute of Molecular, Cell and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, UK
| | - Massimo Zeviani
- Venetian Institute of Molecular Medicine, Padova, Italy.,Department of Neurosciences, University of Padova, Italy
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11
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Human Mitochondrial Pathologies of the Respiratory Chain and ATP Synthase: Contributions from Studies of Saccharomyces cerevisiae. Life (Basel) 2020; 10:life10110304. [PMID: 33238568 PMCID: PMC7700678 DOI: 10.3390/life10110304] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2020] [Revised: 11/18/2020] [Accepted: 11/19/2020] [Indexed: 12/14/2022] Open
Abstract
The ease with which the unicellular yeast Saccharomyces cerevisiae can be manipulated genetically and biochemically has established this organism as a good model for the study of human mitochondrial diseases. The combined use of biochemical and molecular genetic tools has been instrumental in elucidating the functions of numerous yeast nuclear gene products with human homologs that affect a large number of metabolic and biological processes, including those housed in mitochondria. These include structural and catalytic subunits of enzymes and protein factors that impinge on the biogenesis of the respiratory chain. This article will review what is currently known about the genetics and clinical phenotypes of mitochondrial diseases of the respiratory chain and ATP synthase, with special emphasis on the contribution of information gained from pet mutants with mutations in nuclear genes that impair mitochondrial respiration. Our intent is to provide the yeast mitochondrial specialist with basic knowledge of human mitochondrial pathologies and the human specialist with information on how genes that directly and indirectly affect respiration were identified and characterized in yeast.
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12
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Cytochrome c oxidase deficiency. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2020; 1862:148335. [PMID: 33171185 DOI: 10.1016/j.bbabio.2020.148335] [Citation(s) in RCA: 52] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 09/10/2020] [Revised: 10/31/2020] [Accepted: 11/03/2020] [Indexed: 12/23/2022]
Abstract
Cytochrome c oxidase (COX) deficiency is characterized by a high degree of genetic and phenotypic heterogeneity, partly reflecting the extreme structural complexity, multiple post-translational modification, variable, tissue-specific composition, and the high number of and intricate connections among the assembly factors of this enzyme. In fact, decreased COX specific activity can manifest with different degrees of severity, affect the whole organism or specific tissues, and develop a wide spectrum of disease natural history, including disease onsets ranging from birth to late adulthood. More than 30 genes have been linked to COX deficiency, but the list is still incomplete and in fact constantly updated. We here discuss the current knowledge about COX in health and disease, focusing on genetic aetiology and link to clinical manifestations. In addition, information concerning either fundamental biological features of the enzymes or biochemical signatures of its defects have been provided by experimental in vivo models, including yeast, fly, mouse and fish, which expanded our knowledge on the functional features and the phenotypical consequences of different forms of COX deficiency.
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13
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Functions of Cytochrome c oxidase Assembly Factors. Int J Mol Sci 2020; 21:ijms21197254. [PMID: 33008142 PMCID: PMC7582755 DOI: 10.3390/ijms21197254] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2020] [Accepted: 09/23/2020] [Indexed: 12/22/2022] Open
Abstract
Cytochrome c oxidase is the terminal complex of eukaryotic oxidative phosphorylation in mitochondria. This process couples the reduction of electron carriers during metabolism to the reduction of molecular oxygen to water and translocation of protons from the internal mitochondrial matrix to the inter-membrane space. The electrochemical gradient formed is used to generate chemical energy in the form of adenosine triphosphate to power vital cellular processes. Cytochrome c oxidase and most oxidative phosphorylation complexes are the product of the nuclear and mitochondrial genomes. This poses a series of topological and temporal steps that must be completed to ensure efficient assembly of the functional enzyme. Many assembly factors have evolved to perform these steps for insertion of protein into the inner mitochondrial membrane, maturation of the polypeptide, incorporation of co-factors and prosthetic groups and to regulate this process. Much of the information about each of these assembly factors has been gleaned from use of the single cell eukaryote Saccharomyces cerevisiae and also mutations responsible for human disease. This review will focus on the assembly factors of cytochrome c oxidase to highlight some of the outstanding questions in the assembly of this vital enzyme complex.
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14
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Halperin D, Drabkin M, Wormser O, Yogev Y, Dolgin V, Shorer Z, Gradstein L, Shelef I, Flusser H, Birk OS. Phenotypic variability and mutation hotspot in COX15-related Leigh syndrome. Am J Med Genet A 2020; 182:1506-1512. [PMID: 32232962 DOI: 10.1002/ajmg.a.61577] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2020] [Revised: 03/12/2020] [Accepted: 03/13/2020] [Indexed: 11/05/2022]
Abstract
COX15 mutations were shown to underlie Leigh syndrome (LS), a progressive subacute necrotizing encephalopathy caused by defects in the mitochondrial respiratory chain. Here, two siblings of consanguineous kindred presented in infancy with a syndrome of hypotonia, nystagmus, psychomotor retardation, and pyramidal signs. Toward the end of their second year, both patients developed progressive quadriparesis, convulsions, and pseudobulbar palsy. Similar to two previously reported cases, one of the two affected siblings had severe hypertrophic obstructive cardiomyopathy, hearing loss, and no visual response. Through linkage analysis and whole-exome sequencing, we identified a homozygous p.R217W mutation in Cytochrome C oxidase assembly protein COX15 homolog. Consistent with the known heterogeneity of mitochondrial diseases in general and that of LS in particular, several phenotypic features were markedly distinguished between the affected siblings and in relation to previous reports of COX15 mutations. Interestingly, of the previously reported five cases of COX15-mutated patients, all of different ethnic origins, three had a p.R217W mutation. We highlight p.R217W as a hotspot mutation in COX15 and delineate the phenotypic variability, both between the patients we describe and in all cases reported to date.
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Affiliation(s)
- Daniel Halperin
- Faculty of Health Sciences, The Morris Kahn Laboratory of Human Genetics, National Institute for Biotechnology in the Negev, Ben-Gurion University of the Negev, Beer-Sheva, Israel
| | - Max Drabkin
- Faculty of Health Sciences, The Morris Kahn Laboratory of Human Genetics, National Institute for Biotechnology in the Negev, Ben-Gurion University of the Negev, Beer-Sheva, Israel
| | - Ohad Wormser
- Faculty of Health Sciences, The Morris Kahn Laboratory of Human Genetics, National Institute for Biotechnology in the Negev, Ben-Gurion University of the Negev, Beer-Sheva, Israel
| | - Yuval Yogev
- Faculty of Health Sciences, The Morris Kahn Laboratory of Human Genetics, National Institute for Biotechnology in the Negev, Ben-Gurion University of the Negev, Beer-Sheva, Israel
| | - Vadim Dolgin
- Faculty of Health Sciences, The Morris Kahn Laboratory of Human Genetics, National Institute for Biotechnology in the Negev, Ben-Gurion University of the Negev, Beer-Sheva, Israel
| | - Zamir Shorer
- Pediatric Neurology Unit, Division of Pediatrics, Soroka University Medical Center, Ben-Gurion University of the Negev, Beer-Sheva, Israel
| | - Libe Gradstein
- Department of Ophthalmology, Soroka University Medical Center and Clalit Health Services, Ben-Gurion University of the Negev, Beer-Sheva, Israel
| | - Ilan Shelef
- Faculty of Health Sciences, Department of Imaging, Soroka University Medical Center, Ben-Gurion University of the Negev, Beer-Sheva, Israel
| | - Hagit Flusser
- Zusman Child Development Center, Division of Pediatrics, Soroka University Medical Center, Ben-Gurion University of the Negev, Beer-Sheva, Israel
| | - Ohad S Birk
- Faculty of Health Sciences, The Morris Kahn Laboratory of Human Genetics, National Institute for Biotechnology in the Negev, Ben-Gurion University of the Negev, Beer-Sheva, Israel.,Genetics Institute, Soroka University Medical Center, Beer-Sheva, Israel
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15
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From Synthesis to Utilization: The Ins and Outs of Mitochondrial Heme. Cells 2020; 9:cells9030579. [PMID: 32121449 PMCID: PMC7140478 DOI: 10.3390/cells9030579] [Citation(s) in RCA: 57] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2020] [Revised: 02/19/2020] [Accepted: 02/23/2020] [Indexed: 12/14/2022] Open
Abstract
Heme is a ubiquitous and essential iron containing metallo-organic cofactor required for virtually all aerobic life. Heme synthesis is initiated and completed in mitochondria, followed by certain covalent modifications and/or its delivery to apo-hemoproteins residing throughout the cell. While the biochemical aspects of heme biosynthetic reactions are well understood, the trafficking of newly synthesized heme—a highly reactive and inherently toxic compound—and its subsequent delivery to target proteins remain far from clear. In this review, we summarize current knowledge about heme biosynthesis and trafficking within and outside of the mitochondria.
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16
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Rajendran J, Purhonen J, Tegelberg S, Smolander OP, Mörgelin M, Rozman J, Gailus-Durner V, Fuchs H, Hrabe de Angelis M, Auvinen P, Mervaala E, Jacobs HT, Szibor M, Fellman V, Kallijärvi J. Alternative oxidase-mediated respiration prevents lethal mitochondrial cardiomyopathy. EMBO Mol Med 2019; 11:emmm.201809456. [PMID: 30530468 PMCID: PMC6328925 DOI: 10.15252/emmm.201809456] [Citation(s) in RCA: 42] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Alternative oxidase (AOX) is a non‐mammalian enzyme that can bypass blockade of the complex III‐IV segment of the respiratory chain (RC). We crossed a Ciona intestinalis AOX transgene into RC complex III (cIII)‐deficient Bcs1lp.S78G knock‐in mice, displaying multiple visceral manifestations and premature death. The homozygotes expressing AOX were viable, and their median survival was extended from 210 to 590 days due to permanent prevention of lethal cardiomyopathy. AOX also prevented renal tubular atrophy and cerebral astrogliosis, but not liver disease, growth restriction, or lipodystrophy, suggesting distinct tissue‐specific pathogenetic mechanisms. Assessment of reactive oxygen species (ROS) production and damage suggested that ROS were not instrumental in the rescue. Cardiac mitochondrial ultrastructure, mitochondrial respiration, and pathological transcriptome and metabolome alterations were essentially normalized by AOX, showing that the restored electron flow upstream of cIII was sufficient to prevent cardiac energetic crisis and detrimental decompensation. These findings demonstrate the value of AOX, both as a mechanistic tool and a potential therapeutic strategy, for cIII deficiencies.
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Affiliation(s)
- Jayasimman Rajendran
- Folkhälsan Research Center, Helsinki, Finland.,Clinicum, Faculty of Medicine, University of Helsinki, Helsinki, Finland
| | - Janne Purhonen
- Folkhälsan Research Center, Helsinki, Finland.,Clinicum, Faculty of Medicine, University of Helsinki, Helsinki, Finland
| | - Saara Tegelberg
- Folkhälsan Research Center, Helsinki, Finland.,Department of Clinical Sciences, Lund, Pediatrics, Lund University, Lund, Sweden.,Molecular Neurology Research Program and Neuroscience Center, University of Helsinki, Helsinki, Finland
| | | | - Matthias Mörgelin
- Division of Infection Medicine, Clinical Sciences, Lund University, Lund, Sweden
| | - Jan Rozman
- German Mouse Clinic, Institute of Experimental Genetics, Helmholtz Zentrum München, German Research Center for Environmental Health, Neuherberg, Germany.,German Center for Diabetes Research (DZD), Neuherberg, Germany
| | - Valerie Gailus-Durner
- German Mouse Clinic, Institute of Experimental Genetics, Helmholtz Zentrum München, German Research Center for Environmental Health, Neuherberg, Germany
| | - Helmut Fuchs
- German Mouse Clinic, Institute of Experimental Genetics, Helmholtz Zentrum München, German Research Center for Environmental Health, Neuherberg, Germany
| | - Martin Hrabe de Angelis
- German Mouse Clinic, Institute of Experimental Genetics, Helmholtz Zentrum München, German Research Center for Environmental Health, Neuherberg, Germany.,German Center for Diabetes Research (DZD), Neuherberg, Germany.,Chair of Experimental Genetics, Center of Life and Food Sciences Weihenstephan, TU Munich, Freising-Weihenstephan, Germany
| | - Petri Auvinen
- Institute of Biotechnology, University of Helsinki, Helsinki, Finland
| | - Eero Mervaala
- Department of Pharmacology, Faculty of Medicine, University of Helsinki, Helsinki, Finland
| | - Howard T Jacobs
- Institute of Biotechnology, University of Helsinki, Helsinki, Finland.,Faculty of Medicine and Life Sciences, University of Tampere, Tampere, Finland
| | - Marten Szibor
- Institute of Biotechnology, University of Helsinki, Helsinki, Finland.,Faculty of Medicine and Life Sciences, University of Tampere, Tampere, Finland
| | - Vineta Fellman
- Folkhälsan Research Center, Helsinki, Finland.,Department of Clinical Sciences, Lund, Pediatrics, Lund University, Lund, Sweden.,Children's Hospital, Helsinki University Hospital, University of Helsinki, Helsinki, Finland
| | - Jukka Kallijärvi
- Folkhälsan Research Center, Helsinki, Finland .,Clinicum, Faculty of Medicine, University of Helsinki, Helsinki, Finland
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17
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Abstract
Heme A is an essential cofactor for respiratory terminal oxidases and vital for respiration in aerobic organisms. The final step of heme A biosynthesis is formylation of the C-8 methyl group of heme molecule by heme A synthase (HAS). HAS is a heme-containing integral membrane protein, and its structure and reaction mechanisms have remained unknown. Thus, little is known about HAS despite of its importance. Here we report the crystal structure of HAS from Bacillus subtilis at 2.2-Å resolution. The N- and C-terminal halves of HAS consist of four-helix bundles and they align in a pseudo twofold symmetry manner. Each bundle contains a pair of histidine residues and forms a heme-binding domain. The C-half domain binds a cofactor-heme molecule, while the N-half domain is vacant. Many water molecules are found in the transmembrane region and around the substrate-binding site, and some of them interact with the main chain of transmembrane helix. Comparison of these two domain structures enables us to construct a substrate-heme binding state structure. This structure implies that a completely conserved glutamate, Glu57 in B. subtilis, is the catalytic residue for the formylation reaction. These results provide valuable suggestions of the substrate-heme binding mechanism. Our results present significant insight into the heme A biosynthesis.
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18
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Bilateral persistent fetal vasculature and a chromosome 10 mutation including COX15. Can J Ophthalmol 2017; 52:e203-e205. [DOI: 10.1016/j.jcjo.2017.04.019] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2016] [Revised: 04/24/2017] [Accepted: 04/28/2017] [Indexed: 11/18/2022]
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19
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Phadke R. Myopathology of Adult and Paediatric Mitochondrial Diseases. J Clin Med 2017; 6:jcm6070064. [PMID: 28677615 PMCID: PMC5532572 DOI: 10.3390/jcm6070064] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2017] [Revised: 06/21/2017] [Accepted: 06/28/2017] [Indexed: 01/09/2023] Open
Abstract
Mitochondria are dynamic organelles ubiquitously present in nucleated eukaryotic cells, subserving multiple metabolic functions, including cellular ATP generation by oxidative phosphorylation (OXPHOS). The OXPHOS machinery comprises five transmembrane respiratory chain enzyme complexes (RC). Defective OXPHOS gives rise to mitochondrial diseases (mtD). The incredible phenotypic and genetic diversity of mtD can be attributed at least in part to the RC dual genetic control (nuclear DNA (nDNA) and mitochondrial DNA (mtDNA)) and the complex interaction between the two genomes. Despite the increasing use of next-generation-sequencing (NGS) and various omics platforms in unravelling novel mtD genes and pathomechanisms, current clinical practice for investigating mtD essentially involves a multipronged approach including clinical assessment, metabolic screening, imaging, pathological, biochemical and functional testing to guide molecular genetic analysis. This review addresses the broad muscle pathology landscape including genotype–phenotype correlations in adult and paediatric mtD, the role of immunodiagnostics in understanding some of the pathomechanisms underpinning the canonical features of mtD, and recent diagnostic advances in the field.
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Affiliation(s)
- Rahul Phadke
- Division of Neuropathology, UCL Institute of Neurology, National Hospital for Neurology and Neurosurgery, UCLH NHS Foundation Trust, London WC1N 3BG, UK.
- Dubowitz Neuromuscular Centre, Great Ormond Street Hospital for Children NHS Foundation Trust, London WC1N 3JH, UK.
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20
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Swenson S, Cannon A, Harris NJ, Taylor NG, Fox JL, Khalimonchuk O. Analysis of Oligomerization Properties of Heme a Synthase Provides Insights into Its Function in Eukaryotes. J Biol Chem 2016; 291:10411-25. [PMID: 26940873 DOI: 10.1074/jbc.m115.707539] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2015] [Indexed: 11/06/2022] Open
Abstract
Heme a is an essential cofactor for function of cytochrome c oxidase in the mitochondrial electron transport chain. Several evolutionarily conserved enzymes have been implicated in the biosynthesis of heme a, including the heme a synthase Cox15. However, the structure of Cox15 is unknown, its enzymatic mechanism and the role of active site residues remain debated, and recent discoveries suggest additional chaperone-like roles for this enzyme. Here, we investigated Cox15 in the model eukaryote Saccharomyces cerevisiae via several approaches to examine its oligomeric states and determine the effects of active site and human pathogenic mutations. Our results indicate that Cox15 exhibits homotypic interactions, forming highly stable complexes dependent upon hydrophobic interactions. This multimerization is evolutionarily conserved and independent of heme levels and heme a synthase catalytic activity. Four conserved histidine residues are demonstrated to be critical for eukaryotic heme a synthase activity and cannot be substituted with other heme-ligating amino acids. The 20-residue linker region connecting the two conserved domains of Cox15 is also important; removal of this linker impairs both Cox15 multimerization and enzymatic activity. Mutations of COX15 causing single amino acid conversions associated with fatal infantile hypertrophic cardiomyopathy and the neurological disorder Leigh syndrome result in impaired stability (S344P) or catalytic function (R217W), and the latter mutation affects oligomeric properties of the enzyme. Structural modeling of Cox15 suggests these two mutations affect protein folding and heme binding, respectively. We conclude that Cox15 multimerization is important for heme a biosynthesis and/or transfer to maturing cytochrome c oxidase.
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Affiliation(s)
- Samantha Swenson
- From the Department of Biochemistry and Nebraska Redox Biology Center, University of Nebraska-Lincoln, Lincoln, Nebraska 68588 and
| | - Andrew Cannon
- From the Department of Biochemistry and Nebraska Redox Biology Center, University of Nebraska-Lincoln, Lincoln, Nebraska 68588 and
| | - Nicholas J Harris
- the Department of Chemistry and Biochemistry, College of Charleston, Charleston, South Carolina 29424
| | - Nicholas G Taylor
- the Department of Chemistry and Biochemistry, College of Charleston, Charleston, South Carolina 29424
| | - Jennifer L Fox
- the Department of Chemistry and Biochemistry, College of Charleston, Charleston, South Carolina 29424
| | - Oleh Khalimonchuk
- From the Department of Biochemistry and Nebraska Redox Biology Center, University of Nebraska-Lincoln, Lincoln, Nebraska 68588 and
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21
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Rak M, Bénit P, Chrétien D, Bouchereau J, Schiff M, El-Khoury R, Tzagoloff A, Rustin P. Mitochondrial cytochrome c oxidase deficiency. Clin Sci (Lond) 2016; 130:393-407. [PMID: 26846578 PMCID: PMC4948581 DOI: 10.1042/cs20150707] [Citation(s) in RCA: 107] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
As with other mitochondrial respiratory chain components, marked clinical and genetic heterogeneity is observed in patients with a cytochrome c oxidase deficiency. This constitutes a considerable diagnostic challenge and raises a number of puzzling questions. So far, pathological mutations have been reported in more than 30 genes, in both mitochondrial and nuclear DNA, affecting either structural subunits of the enzyme or proteins involved in its biogenesis. In this review, we discuss the possible causes of the discrepancy between the spectacular advances made in the identification of the molecular bases of cytochrome oxidase deficiency and the lack of any efficient treatment in diseases resulting from such deficiencies. This brings back many unsolved questions related to the frequent delay of clinical manifestation, variable course and severity, and tissue-involvement often associated with these diseases. In this context, we stress the importance of studying different models of these diseases, but also discuss the limitations encountered in most available disease models. In the future, with the possible exception of replacement therapy using genes, cells or organs, a better understanding of underlying mechanism(s) of these mitochondrial diseases is presumably required to develop efficient therapy.
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Affiliation(s)
- Malgorzata Rak
- Institut National de la Santé et de la Recherche Médicale Unité Mixte de Recherche 1141, Hôpital Robert Debré, 48 Boulevard Sérurier, 75019 Paris, France Faculté de Médecine Denis Diderot, Université Paris Diderot-Paris 7, Site Robert Debré, 48 Boulevard Sérurier, 75019 Paris, France
| | - Paule Bénit
- Institut National de la Santé et de la Recherche Médicale Unité Mixte de Recherche 1141, Hôpital Robert Debré, 48 Boulevard Sérurier, 75019 Paris, France Faculté de Médecine Denis Diderot, Université Paris Diderot-Paris 7, Site Robert Debré, 48 Boulevard Sérurier, 75019 Paris, France
| | - Dominique Chrétien
- Institut National de la Santé et de la Recherche Médicale Unité Mixte de Recherche 1141, Hôpital Robert Debré, 48 Boulevard Sérurier, 75019 Paris, France Faculté de Médecine Denis Diderot, Université Paris Diderot-Paris 7, Site Robert Debré, 48 Boulevard Sérurier, 75019 Paris, France
| | - Juliette Bouchereau
- Institut National de la Santé et de la Recherche Médicale Unité Mixte de Recherche 1141, Hôpital Robert Debré, 48 Boulevard Sérurier, 75019 Paris, France Faculté de Médecine Denis Diderot, Université Paris Diderot-Paris 7, Site Robert Debré, 48 Boulevard Sérurier, 75019 Paris, France
| | - Manuel Schiff
- Institut National de la Santé et de la Recherche Médicale Unité Mixte de Recherche 1141, Hôpital Robert Debré, 48 Boulevard Sérurier, 75019 Paris, France Faculté de Médecine Denis Diderot, Université Paris Diderot-Paris 7, Site Robert Debré, 48 Boulevard Sérurier, 75019 Paris, France Reference Center for Inherited Metabolic Diseases, Hôpital Robert Debré, Assistance Publique-Hôpitaux de Paris, 48 Boulevard Sérurier, 75019 Paris, France
| | - Riyad El-Khoury
- American University of Beirut Medical Center, Department of Pathology and Laboratory Medicine, Cairo Street, Hamra, Beirut, Lebanon
| | - Alexander Tzagoloff
- Biological Sciences Department, Columbia University, New York, NY 10027, U.S.A
| | - Pierre Rustin
- Institut National de la Santé et de la Recherche Médicale Unité Mixte de Recherche 1141, Hôpital Robert Debré, 48 Boulevard Sérurier, 75019 Paris, France Faculté de Médecine Denis Diderot, Université Paris Diderot-Paris 7, Site Robert Debré, 48 Boulevard Sérurier, 75019 Paris, France
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22
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Opa1 overexpression ameliorates the phenotype of two mitochondrial disease mouse models. Cell Metab 2015; 21:845-54. [PMID: 26039449 PMCID: PMC4457891 DOI: 10.1016/j.cmet.2015.04.016] [Citation(s) in RCA: 165] [Impact Index Per Article: 18.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/29/2014] [Revised: 02/13/2015] [Accepted: 04/12/2015] [Indexed: 02/07/2023]
Abstract
Increased levels of the mitochondria-shaping protein Opa1 improve respiratory chain efficiency and protect from tissue damage, suggesting that it could be an attractive target to counteract mitochondrial dysfunction. Here we show that Opa1 overexpression ameliorates two mouse models of defective mitochondrial bioenergetics. The offspring from crosses of a constitutive knockout for the structural complex I component Ndufs4 (Ndufs4(-/-)), and of a muscle-specific conditional knockout for the complex IV assembly factor Cox15 (Cox15(sm/sm)), with Opa1 transgenic (Opa1(tg)) mice showed improved motor skills and respiratory chain activities compared to the naive, non-Opa1-overexpressing, models. While the amelioration was modest in Ndufs4(-/-)::Opa1(tg) mice, correction of cristae ultrastructure and mitochondrial respiration, improvement of motor performance and prolongation of lifespan were remarkable in Cox15(sm/sm)::Opa1(tg) mice. Mechanistically, respiratory chain supercomplexes were increased in Cox15(sm/sm)::Opa1(tg) mice, and residual monomeric complex IV was stabilized. In conclusion, cristae shape amelioration by controlled Opa1 overexpression improves two mouse models of mitochondrial disease.
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23
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High-resolution melting analysis of 15 genes in 60 patients with cytochrome-c oxidase deficiency. J Hum Genet 2012; 57:442-8. [PMID: 22592081 DOI: 10.1038/jhg.2012.49] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Cytochrome-c oxidase (COX) deficiency is one of the common childhood mitochondrial disorders. Mutations in genes for the assembly factors SURF1 and SCO2 are prevalent in children with COX deficiency in the Slavonic population. Molecular diagnosis is difficult because of the number of genes involved in COX biogenesis and assembly. The aim of this study was to screen for mutations in 15 nuclear genes that encode the 10 structural subunits, their isoforms and two assembly factors of COX in 60 unrelated Czech children with COX deficiency. Nine novel variants were identified in exons and adjacent intronic regions of COX4I2, COX6A1, COX6A2, COX7A1, COX7A2 and COX10 using high-resolution melting (HRM) analysis. Online bioinformatics servers were used to predict the importance of the newly identified amino-acid substitutions. The newly characterized variants updated the contemporary spectrum of known genetic sequence variations that are present in the Czech population, which will be important for further targeted mutation screening in Czech COX-deficient children. HRM and predictive bioinformatics methodologies are advantageous because they are low-cost screening tools that complement large-scale genomic studies and reduce the required time and effort.
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