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Bohovych I, Chan SS, Khalimonchuk O. Mitochondrial protein quality control: the mechanisms guarding mitochondrial health. Antioxid Redox Signal 2015; 22:977-94. [PMID: 25546710 PMCID: PMC4390190 DOI: 10.1089/ars.2014.6199] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/26/2014] [Accepted: 12/20/2014] [Indexed: 12/20/2022]
Abstract
SIGNIFICANCE Mitochondria are complex dynamic organelles pivotal for cellular physiology and human health. Failure to maintain mitochondrial health leads to numerous maladies that include late-onset neurodegenerative diseases and cardiovascular disorders. Furthermore, a decline in mitochondrial health is prevalent with aging. A set of evolutionary conserved mechanisms known as mitochondrial quality control (MQC) is involved in recognition and correction of the mitochondrial proteome. RECENT ADVANCES Here, we review current knowledge and latest developments in MQC. We particularly focus on the proteolytic aspect of MQC and its impact on health and aging. CRITICAL ISSUES While our knowledge about MQC is steadily growing, critical gaps remain in the mechanistic understanding of how MQC modules sense damage and preserve mitochondrial welfare, particularly in higher organisms. FUTURE DIRECTIONS Delineating how coordinated action of the MQC modules orchestrates physiological responses on both organellar and cellular levels will further elucidate the current picture of MQC's role and function in health, cellular stress, and degenerative diseases.
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Affiliation(s)
- Iryna Bohovych
- Department of Biochemistry, University of Nebraska-Lincoln, Lincoln, Nebraska
- Nebraska Redox Biology Center, University of Nebraska-Lincoln, Lincoln, Nebraska
| | - Sherine S.L. Chan
- Department of Drug Discovery and Biomedical Sciences, Medical University of South Carolina, Charleston, South Carolina
| | - Oleh Khalimonchuk
- Department of Biochemistry, University of Nebraska-Lincoln, Lincoln, Nebraska
- Nebraska Redox Biology Center, University of Nebraska-Lincoln, Lincoln, Nebraska
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152
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Coutelier M, Stevanin G, Brice A. Genetic landscape remodelling in spinocerebellar ataxias: the influence of next-generation sequencing. J Neurol 2015; 262:2382-95. [DOI: 10.1007/s00415-015-7725-4] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2015] [Revised: 03/25/2015] [Accepted: 03/26/2015] [Indexed: 12/23/2022]
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153
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Mancini C, Orsi L, Guo Y, Li J, Chen Y, Wang F, Tian L, Liu X, Zhang J, Jiang H, Nmezi BS, Tatsuta T, Giorgio E, Di Gregorio E, Cavalieri S, Pozzi E, Mortara P, Caglio MM, Balducci A, Pinessi L, Langer T, Padiath QS, Hakonarson H, Zhang X, Brusco A. An atypical form of AOA2 with myoclonus associated with mutations in SETX and AFG3L2. BMC MEDICAL GENETICS 2015; 16:16. [PMID: 25927548 PMCID: PMC4422141 DOI: 10.1186/s12881-015-0159-0] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/19/2014] [Accepted: 02/26/2015] [Indexed: 11/10/2022]
Abstract
BACKGROUND Hereditary ataxias are a heterogeneous group of neurodegenerative disorders, where exome sequencing may become an important diagnostic tool to solve clinically or genetically complex cases. METHODS We describe an Italian family in which three sisters were affected by ataxia with postural/intentional myoclonus and involuntary movements at onset, which persisted during the disease. Oculomotor apraxia was absent. Clinical and genetic data did not allow us to exclude autosomal dominant or recessive inheritance and suggest a disease gene. RESULTS Exome sequencing identified a homozygous c.6292C > T (p.Arg2098*) mutation in SETX and a heterozygous c.346G > A (p.Gly116Arg) mutation in AFG3L2 shared by all three affected individuals. A fourth sister (II.7) had subclinical myoclonic jerks at proximal upper limbs and perioral district, confirmed by electrophysiology, and carried the p.Gly116Arg change. Three siblings were healthy. Pathogenicity prediction and a yeast-functional assay suggested p.Gly116Arg impaired m-AAA (ATPases associated with various cellular activities) complex function. CONCLUSIONS Exome sequencing is a powerful tool in identifying disease genes. We identified an atypical form of Ataxia with Oculoapraxia type 2 (AOA2) with myoclonus at onset associated with the c.6292C > T (p.Arg2098*) homozygous mutation. Because the same genotype was described in six cases from a Tunisian family with a typical AOA2 without myoclonus, we speculate this latter feature is associated with a second mutated gene, namely AFG3L2 (p.Gly116Arg variant). We suggest that variant phenotypes may be due to the combined effect of different mutated genes associated to ataxia or related disorders, that will become more apparent as the costs of exome sequencing progressively will reduce, amplifying its diagnostics use, and meanwhile proposing significant challenges in the interpretation of the data.
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Affiliation(s)
- Cecilia Mancini
- Department of Medical Sciences, University of Torino, via Santena 19, 10126, Torino, Italy.
| | - Laura Orsi
- Struttura Complessa Neurologia I, Department of Neuroscience and Mental Health, Città della Salute e della Scienza University Hospital, Torino, 10126, Italy.
| | - Yiran Guo
- Center for Applied Genomics, The Children's Hospital of Philadelphia, Philadelphia, PA, 19104, USA.
| | | | | | - Fengxiang Wang
- Center for Applied Genomics, The Children's Hospital of Philadelphia, Philadelphia, PA, 19104, USA.
| | - Lifeng Tian
- Center for Applied Genomics, The Children's Hospital of Philadelphia, Philadelphia, PA, 19104, USA.
| | | | | | - Hui Jiang
- BGI-Shenzhen, Shenzhen, 510803, China. .,Shenzhen Key Laboratory of Genomics, Shenzhen, 518083, China. .,The Guangdong Enterprise Key Laboratory of Human Disease Genomics, BGI-Shenzhen, Shenzhen, 510803, China.
| | - Bruce Shike Nmezi
- Department of Human Genetics, Graduate School of Public Health, University of Pittsburgh, Pittsburgh, PA, 15261, USA.
| | - Takashi Tatsuta
- Institute for Genetics, Center for Molecular Medicine (CMMC), Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Cologne, 50931, Germany.
| | - Elisa Giorgio
- Department of Medical Sciences, University of Torino, via Santena 19, 10126, Torino, Italy.
| | - Eleonora Di Gregorio
- Medical Genetics Unit, Città della Salute e della Scienza University Hospital, Torino, 10126, Italy.
| | - Simona Cavalieri
- Medical Genetics Unit, Città della Salute e della Scienza University Hospital, Torino, 10126, Italy.
| | - Elisa Pozzi
- Department of Medical Sciences, University of Torino, via Santena 19, 10126, Torino, Italy.
| | - Paolo Mortara
- Struttura Complessa Neurologia I, Department of Neuroscience and Mental Health, Città della Salute e della Scienza University Hospital, Torino, 10126, Italy. .,Department of Neuroscience, University of Torino, Torino, 10126, Italy.
| | - Maria Marcella Caglio
- Department of Neuroscience, University of Torino, Torino, 10126, Italy. .,Division of Neurology III, Department of Neuroscience and Mental Health, Città della Salute e della Scienza University Hospital, Torino, 10126, Italy.
| | - Alessandro Balducci
- Department of Neuroscience, University of Torino, Torino, 10126, Italy. .,Division of Neurology III, Department of Neuroscience and Mental Health, Città della Salute e della Scienza University Hospital, Torino, 10126, Italy.
| | - Lorenzo Pinessi
- Struttura Complessa Neurologia I, Department of Neuroscience and Mental Health, Città della Salute e della Scienza University Hospital, Torino, 10126, Italy. .,Department of Neuroscience, University of Torino, Torino, 10126, Italy.
| | - Thomas Langer
- Institute for Genetics, Center for Molecular Medicine (CMMC), Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Cologne, 50931, Germany. .,Max-Planck-Institute for Biology of Aging, Cologne, 50931, Germany.
| | - Quasar S Padiath
- Department of Human Genetics, Graduate School of Public Health, University of Pittsburgh, Pittsburgh, PA, 15261, USA.
| | - Hakon Hakonarson
- Center for Applied Genomics, The Children's Hospital of Philadelphia, Philadelphia, PA, 19104, USA. .,Division of Human Genetics, The Children's Hospital of Philadelphia, Philadelphia, PA, 19104, USA. .,Department of Pediatrics, The Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, 19104, USA.
| | - Xiuqing Zhang
- BGI-Shenzhen, Shenzhen, 510803, China. .,Shenzhen Key Laboratory of Genomics, Shenzhen, 518083, China. .,The Guangdong Enterprise Key Laboratory of Human Disease Genomics, BGI-Shenzhen, Shenzhen, 510803, China.
| | - Alfredo Brusco
- Department of Medical Sciences, University of Torino, via Santena 19, 10126, Torino, Italy. .,Medical Genetics Unit, Città della Salute e della Scienza University Hospital, Torino, 10126, Italy.
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Pfeffer G, Pyle A, Griffin H, Miller J, Wilson V, Turnbull L, Fawcett K, Sims D, Eglon G, Hadjivassiliou M, Horvath R, Németh A, Chinnery PF. SPG7 mutations are a common cause of undiagnosed ataxia. Neurology 2015; 84:1174-6. [PMID: 25681447 PMCID: PMC4371411 DOI: 10.1212/wnl.0000000000001369] [Citation(s) in RCA: 76] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/05/2022] Open
Affiliation(s)
- Gerald Pfeffer
- From the Wellcome Trust Centre for Mitochondrial Research (G.P., A.P., H.G., V.W., L.T., G.E., R.H., P.F.C.) and Institute of Genetic Medicine (G.P., A.P., H.G., R.H., P.F.C.), Newcastle University, Newcastle-upon-Tyne; John Radcliffe Hospital (J.M., K.F., D.S., A.N.), University of Oxford; Royal Hallamshire Hospital (M.H.), University of Sheffield; and Churchill Hospital (A.N.), Oxford, UK
| | - Angela Pyle
- From the Wellcome Trust Centre for Mitochondrial Research (G.P., A.P., H.G., V.W., L.T., G.E., R.H., P.F.C.) and Institute of Genetic Medicine (G.P., A.P., H.G., R.H., P.F.C.), Newcastle University, Newcastle-upon-Tyne; John Radcliffe Hospital (J.M., K.F., D.S., A.N.), University of Oxford; Royal Hallamshire Hospital (M.H.), University of Sheffield; and Churchill Hospital (A.N.), Oxford, UK
| | - Helen Griffin
- From the Wellcome Trust Centre for Mitochondrial Research (G.P., A.P., H.G., V.W., L.T., G.E., R.H., P.F.C.) and Institute of Genetic Medicine (G.P., A.P., H.G., R.H., P.F.C.), Newcastle University, Newcastle-upon-Tyne; John Radcliffe Hospital (J.M., K.F., D.S., A.N.), University of Oxford; Royal Hallamshire Hospital (M.H.), University of Sheffield; and Churchill Hospital (A.N.), Oxford, UK
| | - Jack Miller
- From the Wellcome Trust Centre for Mitochondrial Research (G.P., A.P., H.G., V.W., L.T., G.E., R.H., P.F.C.) and Institute of Genetic Medicine (G.P., A.P., H.G., R.H., P.F.C.), Newcastle University, Newcastle-upon-Tyne; John Radcliffe Hospital (J.M., K.F., D.S., A.N.), University of Oxford; Royal Hallamshire Hospital (M.H.), University of Sheffield; and Churchill Hospital (A.N.), Oxford, UK
| | - Valerie Wilson
- From the Wellcome Trust Centre for Mitochondrial Research (G.P., A.P., H.G., V.W., L.T., G.E., R.H., P.F.C.) and Institute of Genetic Medicine (G.P., A.P., H.G., R.H., P.F.C.), Newcastle University, Newcastle-upon-Tyne; John Radcliffe Hospital (J.M., K.F., D.S., A.N.), University of Oxford; Royal Hallamshire Hospital (M.H.), University of Sheffield; and Churchill Hospital (A.N.), Oxford, UK
| | - Lisa Turnbull
- From the Wellcome Trust Centre for Mitochondrial Research (G.P., A.P., H.G., V.W., L.T., G.E., R.H., P.F.C.) and Institute of Genetic Medicine (G.P., A.P., H.G., R.H., P.F.C.), Newcastle University, Newcastle-upon-Tyne; John Radcliffe Hospital (J.M., K.F., D.S., A.N.), University of Oxford; Royal Hallamshire Hospital (M.H.), University of Sheffield; and Churchill Hospital (A.N.), Oxford, UK
| | - Katherine Fawcett
- From the Wellcome Trust Centre for Mitochondrial Research (G.P., A.P., H.G., V.W., L.T., G.E., R.H., P.F.C.) and Institute of Genetic Medicine (G.P., A.P., H.G., R.H., P.F.C.), Newcastle University, Newcastle-upon-Tyne; John Radcliffe Hospital (J.M., K.F., D.S., A.N.), University of Oxford; Royal Hallamshire Hospital (M.H.), University of Sheffield; and Churchill Hospital (A.N.), Oxford, UK
| | - David Sims
- From the Wellcome Trust Centre for Mitochondrial Research (G.P., A.P., H.G., V.W., L.T., G.E., R.H., P.F.C.) and Institute of Genetic Medicine (G.P., A.P., H.G., R.H., P.F.C.), Newcastle University, Newcastle-upon-Tyne; John Radcliffe Hospital (J.M., K.F., D.S., A.N.), University of Oxford; Royal Hallamshire Hospital (M.H.), University of Sheffield; and Churchill Hospital (A.N.), Oxford, UK
| | - Gail Eglon
- From the Wellcome Trust Centre for Mitochondrial Research (G.P., A.P., H.G., V.W., L.T., G.E., R.H., P.F.C.) and Institute of Genetic Medicine (G.P., A.P., H.G., R.H., P.F.C.), Newcastle University, Newcastle-upon-Tyne; John Radcliffe Hospital (J.M., K.F., D.S., A.N.), University of Oxford; Royal Hallamshire Hospital (M.H.), University of Sheffield; and Churchill Hospital (A.N.), Oxford, UK
| | - Marios Hadjivassiliou
- From the Wellcome Trust Centre for Mitochondrial Research (G.P., A.P., H.G., V.W., L.T., G.E., R.H., P.F.C.) and Institute of Genetic Medicine (G.P., A.P., H.G., R.H., P.F.C.), Newcastle University, Newcastle-upon-Tyne; John Radcliffe Hospital (J.M., K.F., D.S., A.N.), University of Oxford; Royal Hallamshire Hospital (M.H.), University of Sheffield; and Churchill Hospital (A.N.), Oxford, UK
| | - Rita Horvath
- From the Wellcome Trust Centre for Mitochondrial Research (G.P., A.P., H.G., V.W., L.T., G.E., R.H., P.F.C.) and Institute of Genetic Medicine (G.P., A.P., H.G., R.H., P.F.C.), Newcastle University, Newcastle-upon-Tyne; John Radcliffe Hospital (J.M., K.F., D.S., A.N.), University of Oxford; Royal Hallamshire Hospital (M.H.), University of Sheffield; and Churchill Hospital (A.N.), Oxford, UK
| | - Andrea Németh
- From the Wellcome Trust Centre for Mitochondrial Research (G.P., A.P., H.G., V.W., L.T., G.E., R.H., P.F.C.) and Institute of Genetic Medicine (G.P., A.P., H.G., R.H., P.F.C.), Newcastle University, Newcastle-upon-Tyne; John Radcliffe Hospital (J.M., K.F., D.S., A.N.), University of Oxford; Royal Hallamshire Hospital (M.H.), University of Sheffield; and Churchill Hospital (A.N.), Oxford, UK
| | - Patrick F Chinnery
- From the Wellcome Trust Centre for Mitochondrial Research (G.P., A.P., H.G., V.W., L.T., G.E., R.H., P.F.C.) and Institute of Genetic Medicine (G.P., A.P., H.G., R.H., P.F.C.), Newcastle University, Newcastle-upon-Tyne; John Radcliffe Hospital (J.M., K.F., D.S., A.N.), University of Oxford; Royal Hallamshire Hospital (M.H.), University of Sheffield; and Churchill Hospital (A.N.), Oxford, UK.
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155
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Iommarini L, Peralta S, Torraco A, Diaz F. Mitochondrial Diseases Part II: Mouse models of OXPHOS deficiencies caused by defects in regulatory factors and other components required for mitochondrial function. Mitochondrion 2015; 22:96-118. [PMID: 25640959 DOI: 10.1016/j.mito.2015.01.008] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2015] [Accepted: 01/22/2015] [Indexed: 01/21/2023]
Abstract
Mitochondrial disorders are defined as defects that affect the oxidative phosphorylation system (OXPHOS). They are characterized by a heterogeneous array of clinical presentations due in part to a wide variety of factors required for proper function of the components of the OXPHOS system. There is no cure for these disorders owing to our poor knowledge of the pathogenic mechanisms of disease. To understand the mechanisms of human disease numerous mouse models have been developed in recent years. Here we summarize the features of several mouse models of mitochondrial diseases directly related to those factors affecting mtDNA maintenance, replication, transcription, translation as well as other proteins that are involved in mitochondrial dynamics and quality control which affect mitochondrial OXPHOS function without being intrinsic components of the system. We discuss how these models have contributed to our understanding of mitochondrial diseases and their pathogenic mechanisms.
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Affiliation(s)
- Luisa Iommarini
- Department of Pharmacy and Biotechnology (FABIT), University of Bologna, Via Irnerio 42, 40128 Bologna, Italy.
| | - Susana Peralta
- Department of Neurology, University of Miami, Miller School of Medicine, Miami, FL 33136, USA.
| | - Alessandra Torraco
- Unit for Neuromuscular and Neurodegenerative Disorders, Laboratory of Molecular Medicine, Bambino Gesù Children's Hospital, IRCCS, Viale di San Paolo, 15 - 00146, Rome, Italy.
| | - Francisca Diaz
- Department of Neurology, University of Miami, Miller School of Medicine, Miami, FL 33136, USA.
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156
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Sebold C, Soileau B, Heard P, Carter E, O'Donnell L, Hale DE, Cody JD. Whole arm deletions of 18p: medical and developmental effects. Am J Med Genet A 2015; 167A:313-23. [PMID: 25586871 DOI: 10.1002/ajmg.a.36880] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2014] [Accepted: 10/01/2014] [Indexed: 11/07/2022]
Abstract
Deletions of the short arm of chromosome 18 have been well-described in case reports. However, the utility of these descriptions in clinical practice is limited by varied and imprecise breakpoints. As we work to establish genotype-phenotype correlations for 18p-, it is critical to have accurate and complete clinical descriptions of individuals with differing breakpoints. In addition, the developmental profile of 18p- has not been well-delineated. We undertook a thorough review of the medical histories of 31 individuals with 18p- and a breakpoint in the centromeric region. We collected developmental data using mailed surveys and questionnaires. The most common findings included neonatal complications; cardiac anomalies; hypotonia; MRI abnormalities; endocrine dysfunction; strabismus; ptosis; and refractive errors. Less common features included holoprosencephaly and its microforms; hearing loss; and orthopedic anomalies. The developmental effects of the deletion appear to be less severe than reported in the literature, as average IQ scores were in the range of borderline intellectual functioning. Based on responses to standardized questionnaires, it appears this population has marked difficulty with activities of daily living, though several young adults were able to live independent of their parents. This manuscript represents the most comprehensive description of a cohort of 18p- individuals with identical breakpoints. Despite identical breakpoints, a great deal of phenotype variability remained among this population, suggesting that many of the genes on 18p- cause low-penetrance phenotypes when present in a hemizygous state. Future efforts will focus on the clinical description of individuals with more distal breakpoints and the identification of critical regions and candidate genes.
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Affiliation(s)
- Courtney Sebold
- Department of Pediatrics, University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, Texas
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157
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Szklarczyk R, Nooteboom M, Osiewacz HD. Control of mitochondrial integrity in ageing and disease. Philos Trans R Soc Lond B Biol Sci 2015; 369:20130439. [PMID: 24864310 DOI: 10.1098/rstb.2013.0439] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Various molecular and cellular pathways are active in eukaryotes to control the quality and integrity of mitochondria. These pathways are involved in keeping a 'healthy' population of this essential organelle during the lifetime of the organism. Quality control (QC) systems counteract processes that lead to organellar dysfunction manifesting as degenerative diseases and ageing. We discuss disease- and ageing-related pathways involved in mitochondrial QC: mtDNA repair and reorganization, regeneration of oxidized amino acids, refolding and degradation of severely damaged proteins, degradation of whole mitochondria by mitophagy and finally programmed cell death. The control of the integrity of mtDNA and regulation of its expression is essential to remodel single proteins as well as mitochondrial complexes that determine mitochondrial functions. The redundancy of components, such as proteases, and the hierarchies of the QC raise questions about crosstalk between systems and their precise regulation. The understanding of the underlying mechanisms on the genomic, proteomic, organellar and cellular levels holds the key for the development of interventions for mitochondrial dysfunctions, degenerative processes, ageing and age-related diseases resulting from impairments of mitochondria.
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Affiliation(s)
- Radek Szklarczyk
- Centre for Molecular and Biomolecular Informatics, Radboud University Medical Centre, 6500 HB Nijmegen, The Netherlands Department of Clinical Genetics, Unit Clinical Genomics, Maastricht University Medical Centre, 6200 MD Maastricht, The Netherlands
| | - Marco Nooteboom
- Department of Biochemistry (286), Radboud Institute for Molecular Life Sciences, Radboud University Medical Centre, 6500 HB Nijmegen, The Netherlands
| | - Heinz D Osiewacz
- Faculty for Biosciences and Cluster of Excellence 'Macromolecular Complexes', Goethe University, Molecular Developmental Biology, 60438 Frankfurt am Main, Germany
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158
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Subramony S, Moscovich M, Ashizawa T. Genetics and Clinical Features of Inherited Ataxias. Mov Disord 2015. [DOI: 10.1016/b978-0-12-405195-9.00062-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
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159
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160
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Baker MJ, Palmer CS, Stojanovski D. Mitochondrial protein quality control in health and disease. Br J Pharmacol 2014; 171:1870-89. [PMID: 24117041 DOI: 10.1111/bph.12430] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2013] [Revised: 08/28/2013] [Accepted: 09/01/2013] [Indexed: 12/13/2022] Open
Abstract
Progressive mitochondrial dysfunction is linked with the onset of many age-related pathologies and neurological disorders. Mitochondrial damage can come in many forms and be induced by a variety of cellular insults. To preserve organelle function during biogenesis or times of stress, multiple surveillance systems work to ensure the persistence of a functional mitochondrial network. This review provides an overview of these processes, which collectively contribute to the maintenance of a healthy mitochondrial population, which is critical for cell physiology and survival.
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Affiliation(s)
- Michael J Baker
- Department of Biochemistry and Molecular Biology and Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Melbourne, VIC, Australia; ARC Centre of Excellence for Coherent X-ray Science, Melbourne, VIC, Australia
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161
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Maltecca F, Baseggio E, Consolato F, Mazza D, Podini P, Young SM, Drago I, Bahr BA, Puliti A, Codazzi F, Quattrini A, Casari G. Purkinje neuron Ca2+ influx reduction rescues ataxia in SCA28 model. J Clin Invest 2014; 125:263-74. [PMID: 25485680 DOI: 10.1172/jci74770] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2013] [Accepted: 11/06/2014] [Indexed: 12/11/2022] Open
Abstract
Spinocerebellar ataxia type 28 (SCA28) is a neurodegenerative disease caused by mutations of the mitochondrial protease AFG3L2. The SCA28 mouse model, which is haploinsufficient for Afg3l2, exhibits a progressive decline in motor function and displays dark degeneration of Purkinje cells (PC-DCD) of mitochondrial origin. Here, we determined that mitochondria in cultured Afg3l2-deficient PCs ineffectively buffer evoked Ca²⁺ peaks, resulting in enhanced cytoplasmic Ca²⁺ concentrations, which subsequently triggers PC-DCD. This Ca²⁺-handling defect is the result of negative synergism between mitochondrial depolarization and altered organelle trafficking to PC dendrites in Afg3l2-mutant cells. In SCA28 mice, partial genetic silencing of the metabotropic glutamate receptor mGluR1 decreased Ca²⁺ influx in PCs and reversed the ataxic phenotype. Moreover, administration of the β-lactam antibiotic ceftriaxone, which promotes synaptic glutamate clearance, thereby reducing Ca²⁺ influx, improved ataxia-associated phenotypes in SCA28 mice when given either prior to or after symptom onset. Together, the results of this study indicate that ineffective mitochondrial Ca²⁺ handling in PCs underlies SCA28 pathogenesis and suggest that strategies that lower glutamate stimulation of PCs should be further explored as a potential treatment for SCA28 patients.
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162
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Rainbolt TK, Saunders JM, Wiseman RL. YME1L degradation reduces mitochondrial proteolytic capacity during oxidative stress. EMBO Rep 2014; 16:97-106. [PMID: 25433032 DOI: 10.15252/embr.201438976] [Citation(s) in RCA: 65] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Mitochondrial proteostasis is maintained by a network of ATP-dependent quality control proteases including the inner membrane protease YME1L. Here, we show that YME1L is a stress-sensitive mitochondrial protease that is rapidly degraded in response to acute oxidative stress. This degradation requires reductions in cellular ATP and involves the activity of the ATP-independent protease OMA1. Oxidative stress-dependent reductions in YME1L inhibit protective YME1L-dependent functions and increase cellular sensitivity to oxidative insult. Collectively, our results identify stress-induced YME1L degradation as a biologic process that attenuates protective regulation of mitochondrial proteostasis and promotes cellular death in response to oxidative stress.
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Affiliation(s)
- T Kelly Rainbolt
- Department of Molecular & Experimental Medicine, Department of Chemical Physiology, The Scripps Research Institute, La Jolla, CA, USA
| | - Jaclyn M Saunders
- Department of Molecular & Experimental Medicine, Department of Chemical Physiology, The Scripps Research Institute, La Jolla, CA, USA
| | - R Luke Wiseman
- Department of Molecular & Experimental Medicine, Department of Chemical Physiology, The Scripps Research Institute, La Jolla, CA, USA
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163
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Sugiura A, McLelland GL, Fon EA, McBride HM. A new pathway for mitochondrial quality control: mitochondrial-derived vesicles. EMBO J 2014; 33:2142-56. [PMID: 25107473 PMCID: PMC4282503 DOI: 10.15252/embj.201488104] [Citation(s) in RCA: 571] [Impact Index Per Article: 57.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2014] [Revised: 07/08/2014] [Accepted: 07/23/2014] [Indexed: 12/31/2022] Open
Abstract
The last decade has been marked by tremendous progress in our understanding of the cell biology of mitochondria, with the identification of molecules and mechanisms that regulate their fusion, fission, motility, and the architectural transitions within the inner membrane. More importantly, the manipulation of these machineries in tissues has provided links between mitochondrial dynamics and physiology. Indeed, just as the proteins required for fusion and fission were identified, they were quickly linked to both rare and common human diseases. This highlighted the critical importance of this emerging field to medicine, with new hopes of finding drugable targets for numerous pathologies, from neurodegenerative diseases to inflammation and cancer. In the midst of these exciting new discoveries, an unexpected new aspect of mitochondrial cell biology has been uncovered; the generation of small vesicular carriers that transport mitochondrial proteins and lipids to other intracellular organelles. These mitochondrial-derived vesicles (MDVs) were first found to transport a mitochondrial outer membrane protein MAPL to a subpopulation of peroxisomes. However, other MDVs did not target peroxisomes and instead fused with the late endosome, or multivesicular body. The Parkinson's disease-associated proteins Vps35, Parkin, and PINK1 are involved in the biogenesis of a subset of these MDVs, linking this novel trafficking pathway to human disease. In this review, we outline what has been learned about the mechanisms and functional importance of MDV transport and speculate on the greater impact of these pathways in cellular physiology.
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Affiliation(s)
- Ayumu Sugiura
- Montreal Neurological Institute, McGill University, Montreal, QC, Canada
| | | | - Edward A Fon
- Montreal Neurological Institute, McGill University, Montreal, QC, Canada
| | - Heidi M McBride
- Montreal Neurological Institute, McGill University, Montreal, QC, Canada
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164
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Myers KA, Warman Chardon J, Huang L, Boycott KM. Deletion ofAFG3L2associated with spinocerebellar ataxia type 28 in the context of multiple genomic anomalies. Am J Med Genet A 2014; 164A:3209-12. [DOI: 10.1002/ajmg.a.36771] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2013] [Accepted: 08/20/2014] [Indexed: 11/10/2022]
Affiliation(s)
- Kenneth A. Myers
- Division of Neurology; Department of Pediatrics; Alberta Children's Hospital; University of Calgary; Calgary Alberta Canada
| | - Jodi Warman Chardon
- Department of Genetics; Children's Hospital of Eastern Ontario; University of Ottawa; Ottawa Ontario Canada
| | - Lijia Huang
- Department of Genetics; Children's Hospital of Eastern Ontario; University of Ottawa; Ottawa Ontario Canada
| | - Kym M. Boycott
- Department of Genetics; Children's Hospital of Eastern Ontario; University of Ottawa; Ottawa Ontario Canada
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165
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Abstract
Mitochondrial disease resulting in reduced bioenergetic output can be due to mutations in either nuclear DNA-encoded or mitochondrial DNA-encoded gene products. We summarize some of the underlying principles of mitochondrial genetics that impact the diagnosis and pathogenesis of mitochondrial disorders. In addition, we present a brief overview of a new frontier in the field, namely, mitochondrial "dynamics," which controls organellar fusion, fission, trafficking, and positioning, and exerts mitochondrial "quality control" by maintaining organellar integrity and viability. Analysis of mutations in gene products associated with this latter area has opened up new vistas in the study of disorders associated with compromised energy production.
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Affiliation(s)
- Estela Area-Gomez
- Department of Neurology, Columbia University Medical Center, New York, NY, USA
| | - Eric A Schon
- Department of Neurology, Columbia University Medical Center, New York, NY, USA Department of Genetics and Development, Columbia University Medical Center, New York, NY, USA
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166
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Chaussenot A, Paquis-Flucklinger V. An overview of neurological and neuromuscular signs in mitochondrial diseases. Rev Neurol (Paris) 2014; 170:323-38. [DOI: 10.1016/j.neurol.2014.03.007] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2014] [Accepted: 03/24/2014] [Indexed: 01/10/2023]
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167
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Almontashiri NAM, Chen HH, Mailloux RJ, Tatsuta T, Teng ACT, Mahmoud AB, Ho T, Stewart NAS, Rippstein P, Harper ME, Roberts R, Willenborg C, Erdmann J, Pastore A, McBride HM, Langer T, Stewart AFR. SPG7 variant escapes phosphorylation-regulated processing by AFG3L2, elevates mitochondrial ROS, and is associated with multiple clinical phenotypes. Cell Rep 2014; 7:834-47. [PMID: 24767997 DOI: 10.1016/j.celrep.2014.03.051] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2013] [Revised: 02/06/2014] [Accepted: 03/20/2014] [Indexed: 02/01/2023] Open
Abstract
Mitochondrial production of reactive oxygen species (ROS) affects many processes in health and disease. SPG7 assembles with AFG3L2 into the mAAA protease at the inner membrane of mitochondria, degrades damaged proteins, and regulates the synthesis of mitochondrial ribosomes. SPG7 is cleaved and activated by AFG3L2 upon assembly. A variant in SPG7 that replaces arginine 688 with glutamine (Q688) is associated with several phenotypes, including toxicity of chemotherapeutic agents, type 2 diabetes mellitus, and (as reported here) coronary artery disease. We demonstrate that SPG7 processing is regulated by tyrosine phosphorylation of AFG3L2. Carriers of Q688 bypass this regulation and constitutively process and activate SPG7 mAAA protease. Cells expressing Q688 produce higher ATP levels and ROS, promoting cell proliferation. Our results thus reveal an unexpected link between the phosphorylation-dependent regulation of the mitochondria mAAA protease affecting ROS production and several clinical phenotypes.
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Affiliation(s)
- Naif A M Almontashiri
- Ruddy Canadian Cardiovascular Genetics Centre, University of Ottawa Heart Institute, Ottawa, ON K1Y, Canada; Department of Biochemistry, Microbiology and Immunology, University of Ottawa, Ottawa, ON K1H 8M5, Canada; Center for Genetics and Inherited Diseases, Department of Applied Medical Sciences, Taibah University, Almedinah, P.O. Box 41477, Saudi Arabia
| | - Hsiao-Huei Chen
- Ottawa Hospital Research Institute, Ottawa, ON K1Y 4E9, Canada
| | - Ryan J Mailloux
- Department of Biochemistry, Microbiology and Immunology, University of Ottawa, Ottawa, ON K1H 8M5, Canada
| | - Takashi Tatsuta
- Institute for Genetics, University of Cologne, Cologne 50674, Germany
| | - Allen C T Teng
- Ruddy Canadian Cardiovascular Genetics Centre, University of Ottawa Heart Institute, Ottawa, ON K1Y, Canada; Department of Biochemistry, Microbiology and Immunology, University of Ottawa, Ottawa, ON K1H 8M5, Canada
| | - Ahmad B Mahmoud
- Department of Biochemistry, Microbiology and Immunology, University of Ottawa, Ottawa, ON K1H 8M5, Canada
| | - Tiffany Ho
- Ruddy Canadian Cardiovascular Genetics Centre, University of Ottawa Heart Institute, Ottawa, ON K1Y, Canada
| | - Nicolas A S Stewart
- Center for Clinical Pharmacology, Department of Medicine, University of Pittsburgh, Pittsburgh, PA 15261, USA
| | - Peter Rippstein
- Ruddy Canadian Cardiovascular Genetics Centre, University of Ottawa Heart Institute, Ottawa, ON K1Y, Canada
| | - Mary Ellen Harper
- Department of Biochemistry, Microbiology and Immunology, University of Ottawa, Ottawa, ON K1H 8M5, Canada
| | - Robert Roberts
- Ruddy Canadian Cardiovascular Genetics Centre, University of Ottawa Heart Institute, Ottawa, ON K1Y, Canada
| | | | | | | | - Annalisa Pastore
- National Institute for Medical Research, The Ridgeway, Mill Hill, London NW7 1AA, UK
| | | | - Thomas Langer
- Institute for Genetics, University of Cologne, Cologne 50674, Germany
| | - Alexandre F R Stewart
- Ruddy Canadian Cardiovascular Genetics Centre, University of Ottawa Heart Institute, Ottawa, ON K1Y, Canada; Department of Biochemistry, Microbiology and Immunology, University of Ottawa, Ottawa, ON K1H 8M5, Canada.
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168
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Matilla-Dueñas A, Ashizawa T, Brice A, Magri S, McFarland KN, Pandolfo M, Pulst SM, Riess O, Rubinsztein DC, Schmidt J, Schmidt T, Scoles DR, Stevanin G, Taroni F, Underwood BR, Sánchez I. Consensus paper: pathological mechanisms underlying neurodegeneration in spinocerebellar ataxias. CEREBELLUM (LONDON, ENGLAND) 2014; 13:269-302. [PMID: 24307138 PMCID: PMC3943639 DOI: 10.1007/s12311-013-0539-y] [Citation(s) in RCA: 98] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Intensive scientific research devoted in the recent years to understand the molecular mechanisms or neurodegeneration in spinocerebellar ataxias (SCAs) are identifying new pathways and targets providing new insights and a better understanding of the molecular pathogenesis in these diseases. In this consensus manuscript, the authors discuss their current views on the identified molecular processes causing or modulating the neurodegenerative phenotype in spinocerebellar ataxias with the common opinion of translating the new knowledge acquired into candidate targets for therapy. The following topics are discussed: transcription dysregulation, protein aggregation, autophagy, ion channels, the role of mitochondria, RNA toxicity, modulators of neurodegeneration and current therapeutic approaches. Overall point of consensus includes the common vision of neurodegeneration in SCAs as a multifactorial, progressive and reversible process, at least in early stages. Specific points of consensus include the role of the dysregulation of protein folding, transcription, bioenergetics, calcium handling and eventual cell death with apoptotic features of neurons during SCA disease progression. Unresolved questions include how the dysregulation of these pathways triggers the onset of symptoms and mediates disease progression since this understanding may allow effective treatments of SCAs within the window of reversibility to prevent early neuronal damage. Common opinions also include the need for clinical detection of early neuronal dysfunction, for more basic research to decipher the early neurodegenerative process in SCAs in order to give rise to new concepts for treatment strategies and for the translation of the results to preclinical studies and, thereafter, in clinical practice.
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Affiliation(s)
- A Matilla-Dueñas
- Health Sciences Research Institute Germans Trias i Pujol (IGTP), Ctra. de Can Ruti, Camí de les Escoles s/n, Badalona, Barcelona, Spain,
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169
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Kondadi AK, Wang S, Montagner S, Kladt N, Korwitz A, Martinelli P, Herholz D, Baker MJ, Schauss AC, Langer T, Rugarli EI. Loss of the m-AAA protease subunit AFG₃L₂ causes mitochondrial transport defects and tau hyperphosphorylation. EMBO J 2014; 33:1011-26. [PMID: 24681487 DOI: 10.1002/embj.201387009] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The m-AAA protease subunit AFG₃L₂ is involved in degradation and processing of substrates in the inner mitochondrial membrane. Mutations in AFG₃L₂ are associated with spinocerebellar ataxia SCA28 in humans and impair axonal development and neuronal survival in mice. The loss of AFG₃L₂ causes fragmentation of the mitochondrial network. However, the pathogenic mechanism of neurodegeneration in the absence of AFG₃L₂ is still unclear. Here, we show that depletion of AFG₃L₂ leads to a specific defect of anterograde transport of mitochondria in murine cortical neurons. We observe similar transport deficiencies upon loss of AFG₃L₂ in OMA1-deficient neurons, indicating that they are not caused by OMA1-mediated degradation of the dynamin-like GTPase OPA1 and inhibition of mitochondrial fusion. Treatment of neurons with antioxidants, such as N-acetylcysteine or vitamin E, or decreasing tau levels in axons restored mitochondrial transport in AFG₃L₂-depleted neurons. Consistently, tau hyperphosphorylation and activation of ERK kinases are detected in mouse neurons postnatally deleted for Afg3l2. We propose that reactive oxygen species signaling leads to cytoskeletal modifications that impair mitochondrial transport in neurons lacking AFG₃L₂.
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170
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A novel missense mutation in AFG3L2 associated with late onset and slow progression of spinocerebellar ataxia type 28. J Mol Neurosci 2013; 52:493-6. [PMID: 24293060 DOI: 10.1007/s12031-013-0187-1] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2013] [Accepted: 11/15/2013] [Indexed: 12/12/2022]
Abstract
SCA28 is caused by mutations in the AFG3L2 gene. This gene encodes a subunit of the mitochondrial metalloprotease AFG3L2 (AFG3-like protein 2). Clinical features of SCA28 include slow to moderate progressive ataxia, dysarthria, and additional symptoms such as nystagmus, slow saccades, and increased deep tendon reflexes. Here, we report on a novel AFG3L2 mutation in a patient with slowly progressive ataxia and a positive family history. The nucleotide change results in the substitution of an evolutionarily highly conserved tyrosine by histidine (p.Y689H) in the M41 peptidase domain of AFG3L2.
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171
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Musova Z, Kaiserova M, Kriegova E, Fillerova R, Vasovcak P, Santava A, Mensikova K, Zumrova A, Krepelova A, Sedlacek Z, Kanovsky P. A Novel Frameshift Mutation in the AFG3L2 Gene in a Patient with Spinocerebellar Ataxia. THE CEREBELLUM 2013; 13:331-7. [DOI: 10.1007/s12311-013-0538-z] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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172
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Campello S, Strappazzon F, Cecconi F. Mitochondrial dismissal in mammals, from protein degradation to mitophagy. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2013; 1837:451-60. [PMID: 24275087 DOI: 10.1016/j.bbabio.2013.11.010] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/29/2013] [Revised: 11/06/2013] [Accepted: 11/15/2013] [Indexed: 11/17/2022]
Abstract
Mitochondria are double-membraned highly dynamic organelles; the shape, location and function of which are determined by a constant balance between opposing fusion and fission events. A fine modulation of mitochondrial structure is crucial for their correct functionality and for many physiological cell processes, the status of these organelles, being thus a key aspect in a cell's fate. Indeed, the homeostasis of mitochondria needs to be highly regulated for the above mentioned reasons, and since a) they are the major source of energy; b) they participate in various signaling pathways; albeit at the same time c) they are also the major source of reactive oxygen species (ROS, the main damaging detrimental players for all cell components). Elaborate mechanisms of mitochondrial quality control have evolved for maintaining a functional mitochondrial network and avoiding cell damage. The first mechanism is the removal of damaged mitochondrial proteins within the organelle via chaperones and protease; the second is the cytosolic ubiquitin-proteasome system (UPS), able to eliminate proteins embedded in the outer mitochondrial membrane; the third is the removal of the entire mitochondria through mitophagy, in the case of extensive organelle damage and dysfunction. In this review, we provide an overview of these mitochondria stability and quality control mechanisms, highlighting mitophagy, and emphasizing the central role of mitochondrial dynamics in this context. This article is part of a Special Issue entitled: Dynamic and ultrastructure of bioenergetic membranes and their components.
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Affiliation(s)
| | - Flavie Strappazzon
- IRCCS Fondazione Santa Lucia, 00143 Rome, Italy; Department of Biology, University of Rome Tor Vergata, 00133 Rome, Italy
| | - Francesco Cecconi
- IRCCS Fondazione Santa Lucia, 00143 Rome, Italy; Department of Biology, University of Rome Tor Vergata, 00133 Rome, Italy; Unit of Cell Stress and Survival, Danish Cancer Society Research Center, Strandboulevarden 49, 2100 Copenhagen Ø, Denmark.
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173
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Grenier K, McLelland GL, Fon EA. Parkin- and PINK1-Dependent Mitophagy in Neurons: Will the Real Pathway Please Stand Up? Front Neurol 2013; 4:100. [PMID: 23882257 PMCID: PMC3715719 DOI: 10.3389/fneur.2013.00100] [Citation(s) in RCA: 100] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2013] [Accepted: 07/08/2013] [Indexed: 11/13/2022] Open
Abstract
Parkinson's disease (PD) is characterized by massive degeneration of dopaminergic neurons in the substantia nigra. Whereas the majority of PD cases are sporadic, about 5-10% of cases are familial and associated with genetic factors. The loss of parkin or PINK1, two such factors, leads to an early onset form of PD. Importantly, recent studies have shown that parkin functions downstream of PINK1 in a common genetic pathway affecting mitochondrial homeostasis. More precisely, parkin has been shown to mediate the autophagy of damaged mitochondria (mitophagy) in a PINK1-dependent manner. However, much of the work characterizing this pathway has been carried out in immortalized cell lines overexpressing high levels of parkin. In contrast, whether or how endogenous parkin and PINK1 contribute to mitophagy in neurons is much less clear. Here we review recent work addressing the role of parkin/PINK1-dependent mitophagy in neurons. Clearly, it appears that mitophagy pathways differ spatially and kinetically in neurons and immortalized cells, and therefore might diverge in their ultimate outcome and function. While evidence suggests that parkin can translocate to mitochondria in neurons, the function and mechanism of mitophagy downstream of parkin recruitment in neurons remains to be clarified. Moreover, it is noteworthy that most work has focused on the downstream signaling events in parkin/PINK1 mitophagy, whereas the upstream signaling pathways remain comparatively poorly characterized. Identifying the upstream signaling mechanisms that trigger parkin/PINK1 mitophagy will help to explain the nature of the insults affecting mitochondrial function in PD, and a better understanding of these pathways in neurons will be the key in identifying new therapeutic targets in PD.
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Affiliation(s)
- Karl Grenier
- McGill Parkinson Program, Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University , Montreal, QC , Canada
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174
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Gispert S, Parganlija D, Klinkenberg M, Dröse S, Wittig I, Mittelbronn M, Grzmil P, Koob S, Hamann A, Walter M, Büchel F, Adler T, Hrabé de Angelis M, Busch DH, Zell A, Reichert AS, Brandt U, Osiewacz HD, Jendrach M, Auburger G. Loss of mitochondrial peptidase Clpp leads to infertility, hearing loss plus growth retardation via accumulation of CLPX, mtDNA and inflammatory factors. Hum Mol Genet 2013; 22:4871-87. [PMID: 23851121 PMCID: PMC7108587 DOI: 10.1093/hmg/ddt338] [Citation(s) in RCA: 143] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
The caseinolytic peptidase P (CLPP) is conserved from bacteria to humans. In the mitochondrial matrix, it multimerizes and forms a macromolecular proteasome-like cylinder together with the chaperone CLPX. In spite of a known relevance for the mitochondrial unfolded protein response, its substrates and tissue-specific roles are unclear in mammals. Recessive CLPP mutations were recently observed in the human Perrault variant of ovarian failure and sensorineural hearing loss. Here, a first characterization of CLPP null mice demonstrated complete female and male infertility and auditory deficits. Disrupted spermatogenesis already at the spermatid stage and ovarian follicular differentiation failure were evident. Reduced pre-/post-natal survival and marked ubiquitous growth retardation contrasted with only light impairment of movement and respiratory activities. Interestingly, the mice showed resistance to ulcerative dermatitis. Systematic expression studies detected up-regulation of other mitochondrial chaperones, accumulation of CLPX and mtDNA as well as inflammatory factors throughout tissues. T-lymphocytes in the spleen were activated. Thus, murine Clpp deletion represents a faithful Perrault model. The disease mechanism probably involves deficient clearance of mitochondrial components and inflammatory tissue destruction.
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175
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Genome-wide expression profiling and functional characterization of SCA28 lymphoblastoid cell lines reveal impairment in cell growth and activation of apoptotic pathways. BMC Med Genomics 2013; 6:22. [PMID: 23777634 PMCID: PMC3689607 DOI: 10.1186/1755-8794-6-22] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2013] [Accepted: 06/05/2013] [Indexed: 11/10/2022] Open
Abstract
Background SCA28 is an autosomal dominant ataxia associated with AFG3L2 gene mutations. We performed a whole genome expression profiling using lymphoblastoid cell lines (LCLs) from four SCA28 patients and six unrelated healthy controls matched for sex and age. Methods Gene expression was evaluated with the Affymetrix GeneChip Human Genome U133A 2.0 Arrays and data were validated by real-time PCR. Results We found 66 genes whose expression was statistically different in SCA28 LCLs, 35 of which were up-regulated and 31 down-regulated. The differentially expressed genes were clustered in five functional categories: (1) regulation of cell proliferation; (2) regulation of programmed cell death; (3) response to oxidative stress; (4) cell adhesion, and (5) chemical homeostasis. To validate these data, we performed functional experiments that proved an impaired SCA28 LCLs growth compared to controls (p < 0.005), an increased number of cells in the G0/G1 phase (p < 0.001), and an increased mortality because of apoptosis (p < 0.05). We also showed that respiratory chain activity and reactive oxygen species levels was not altered, although lipid peroxidation in SCA28 LCLs was increased in basal conditions (p < 0.05). We did not detect mitochondrial DNA large deletions. An increase of TFAM, a crucial protein for mtDNA maintenance, and of DRP1, a key regulator of mitochondrial dynamic mechanism, suggested an alteration of fission/fusion pathways. Conclusions Whole genome expression profiling, performed on SCA28 LCLs, allowed us to identify five altered functional categories that characterize the SCA28 LCLs phenotype, the first reported in human cells to our knowledge.
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176
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Goard CA, Schimmer AD. Mitochondrial matrix proteases as novel therapeutic targets in malignancy. Oncogene 2013; 33:2690-9. [PMID: 23770858 DOI: 10.1038/onc.2013.228] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2013] [Revised: 04/23/2013] [Accepted: 04/30/2013] [Indexed: 12/30/2022]
Abstract
Although mitochondrial function is often altered in cancer, it remains essential for tumor viability. Tight control of protein homeostasis is required for the maintenance of mitochondrial function, and the mitochondrial matrix houses several coordinated protein quality control systems. These include three evolutionarily conserved proteases of the AAA+ superfamily-the Lon, ClpXP and m-AAA proteases. In humans, these proteases are proposed to degrade, process and chaperone the assembly of mitochondrial proteins in the matrix and inner membrane involved in oxidative phosphorylation, mitochondrial protein synthesis, mitochondrial network dynamics and nucleoid function. In addition, these proteases are upregulated by a variety of mitochondrial stressors, including oxidative stress, unfolded protein stress and imbalances in respiratory complex assembly. Given that tumor cells must survive and proliferate under dynamic cellular stress conditions, dysregulation of mitochondrial protein quality control systems may provide a selective advantage. The association of mitochondrial matrix AAA+ proteases with cancer and their potential for therapeutic modulation therefore warrant further consideration. Although our current knowledge of the endogenous human substrates of these proteases is limited, we highlight functional insights gained from cultured human cells, protease-deficient mouse models and other eukaryotic model organisms. We also review the consequences of disrupting mitochondrial matrix AAA+ proteases through genetic and pharmacological approaches, along with implications of these studies on the potential of these proteases as anticancer therapeutic targets.
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Affiliation(s)
- C A Goard
- Princess Margaret Cancer Centre, Ontario Cancer Institute, University Health Network, Toronto, Ontario, Canada
| | - A D Schimmer
- Princess Margaret Cancer Centre, Ontario Cancer Institute, University Health Network, Toronto, Ontario, Canada
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177
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Figueira TR, Barros MH, Camargo AA, Castilho RF, Ferreira JCB, Kowaltowski AJ, Sluse FE, Souza-Pinto NC, Vercesi AE. Mitochondria as a source of reactive oxygen and nitrogen species: from molecular mechanisms to human health. Antioxid Redox Signal 2013; 18:2029-74. [PMID: 23244576 DOI: 10.1089/ars.2012.4729] [Citation(s) in RCA: 304] [Impact Index Per Article: 27.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Mitochondrially generated reactive oxygen species are involved in a myriad of signaling and damaging pathways in different tissues. In addition, mitochondria are an important target of reactive oxygen and nitrogen species. Here, we discuss basic mechanisms of mitochondrial oxidant generation and removal and the main factors affecting mitochondrial redox balance. We also discuss the interaction between mitochondrial reactive oxygen and nitrogen species, and the involvement of these oxidants in mitochondrial diseases, cancer, neurological, and cardiovascular disorders.
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Affiliation(s)
- Tiago R Figueira
- Department of Clinical Pathology, Faculty of Medical Sciences, State University of Campinas, Campinas, Brazil
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178
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Jose C, Melser S, Benard G, Rossignol R. Mitoplasticity: adaptation biology of the mitochondrion to the cellular redox state in physiology and carcinogenesis. Antioxid Redox Signal 2013; 18:808-49. [PMID: 22989324 DOI: 10.1089/ars.2011.4357] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Adaptation and transformation biology of the mitochondrion to redox status is an emerging domain of physiology and pathophysiology. Mitochondrial adaptations occur in response to accidental changes in cellular energy demand or supply while mitochondrial transformations are a part of greater program of cell metamorphosis. The possible role of mitochondrial adaptations and transformations in pathogenesis remains unexplored, and it has become critical to decipher the stimuli and the underlying molecular pathways. Immediate activation of mitochondrial function was described during acute exercise, respiratory chain injury, Endoplasmic Reticulum stress, genotoxic stress, or environmental toxic insults. Delayed adaptations of mitochondrial form, composition, and functions were evidenced for persistent changes in redox status as observed in endurance training, in fibroblasts grown in presence of respiratory chain inhibitors or in absence of glucose, in the smooth muscle of patients with severe asthma, or in the skeletal muscle of patients with a mitochondrial disease. Besides, mitochondrial transformations were observed in the course of human cell differentiation, during immune response activation, or in cells undergoing carcinogenesis. Little is known on the signals and downstream pathways that govern mitochondrial adaptations and transformations. Few adaptative loops, including redox sensors, kinases, and transcription factors were deciphered, but their implication in physiology and pathology remains elusive. Mitoplasticity could play a protective role against aging, diabetes, cancer, or neurodegenerative diseases. Research on adaptation and transformation could allow the design of innovative therapies, notably in cancer.
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Affiliation(s)
- Caroline Jose
- University Bordeaux, Maladies Rares: Génétique et Métabolisme, France
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179
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Rüb U, Schöls L, Paulson H, Auburger G, Kermer P, Jen JC, Seidel K, Korf HW, Deller T. Clinical features, neurogenetics and neuropathology of the polyglutamine spinocerebellar ataxias type 1, 2, 3, 6 and 7. Prog Neurobiol 2013; 104:38-66. [PMID: 23438480 DOI: 10.1016/j.pneurobio.2013.01.001] [Citation(s) in RCA: 228] [Impact Index Per Article: 20.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2012] [Revised: 01/22/2013] [Accepted: 01/31/2013] [Indexed: 12/18/2022]
Abstract
The spinocerebellar ataxias type 1 (SCA1), 2 (SCA2), 3 (SCA3), 6 (SCA6) and 7 (SCA7) are genetically defined autosomal dominantly inherited progressive cerebellar ataxias (ADCAs). They belong to the group of CAG-repeat or polyglutamine diseases and share pathologically expanded and meiotically unstable glutamine-encoding CAG-repeats at distinct gene loci encoding elongated polyglutamine stretches in the disease proteins. In recent years, progress has been made in the understanding of the pathogenesis of these currently incurable diseases: Identification of underlying genetic mechanisms made it possible to classify the different ADCAs and to define their clinical and pathological features. Furthermore, advances in molecular biology yielded new insights into the physiological and pathophysiological role of the gene products of SCA1, SCA2, SCA3, SCA6 and SCA7 (i.e. ataxin-1, ataxin-2, ataxin-3, α-1A subunit of the P/Q type voltage-dependent calcium channel, ataxin-7). In the present review we summarize our current knowledge about the polyglutamine ataxias SCA1, SCA2, SCA3, SCA6 and SCA7 and compare their clinical and electrophysiological features, genetic and molecular biological background, as well as their brain pathologies. Furthermore, we provide an overview of the structure, interactions and functions of the different disease proteins. On the basis of these comprehensive data, similarities, differences and possible disease mechanisms are discussed.
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Affiliation(s)
- Udo Rüb
- Dr. Senckenberg Chronomedical Institute, Goethe-University, Theodor-Stern-Kai 7, D-60590 Frankfurt/Main, Germany.
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180
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Abstract
This review focuses on organellar AAA/FtsH proteases, whose proteolytic and chaperone-like activity is a crucial component of the protein quality control systems of mitochondrial and chloroplast membranes. We compare the AAA/FtsH proteases from yeast, mammals and plants. The nature of the complexes formed by AAA/FtsH proteases and the current view on their involvement in degradation of non-native organellar proteins or assembly of membrane complexes are discussed. Additional functions of AAA proteases not directly connected with protein quality control found in yeast and mammals but not yet in plants are also described shortly. Following an overview of the molecular functions of the AAA/FtsH proteases we discuss physiological consequences of their inactivation in yeast, mammals and plants. The molecular basis of phenotypes associated with inactivation of the AAA/FtsH proteases is not fully understood yet, with the notable exception of those observed in m-AAA protease-deficient yeast cells, which are caused by impaired maturation of mitochondrial ribosomal protein. Finally, examples of cytosolic events affecting protein quality control in mitochondria and chloroplasts are given. This article is part of a Special Issue entitled: Protein Import and Quality Control in Mitochondria and Plastids.
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Affiliation(s)
- Hanna Janska
- Department of Biotechnology, University of Wroclaw, Przybyszewskiego 63/77, 51-148 Wroclaw, Poland.
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181
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Klebe S, Depienne C, Gerber S, Challe G, Anheim M, Charles P, Fedirko E, Lejeune E, Cottineau J, Brusco A, Dollfus H, Chinnery PF, Mancini C, Ferrer X, Sole G, Destée A, Mayer JM, Fontaine B, de Seze J, Clanet M, Ollagnon E, Busson P, Cazeneuve C, Stevanin G, Kaplan J, Rozet JM, Brice A, Durr A. Spastic paraplegia gene 7 in patients with spasticity and/or optic neuropathy. ACTA ACUST UNITED AC 2013; 135:2980-93. [PMID: 23065789 DOI: 10.1093/brain/aws240] [Citation(s) in RCA: 126] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Mutations in the spastic paraplegia 7 (SPG7) gene encoding paraplegin are responsible for autosomal recessive hereditary spasticity. We screened 135 unrelated index cases, selected in five different settings: SPG7-positive patients detected during SPG31 analysis using SPG31/SPG7 multiplex ligation-dependent probe amplification (n = 7); previously reported ambiguous SPG7 cases (n = 5); patients carefully selected on the basis of their phenotype (spasticity of the lower limbs with cerebellar signs and/or cerebellar atrophy on magnetic resonance imaging/computer tomography scan and/or optic neuropathy and without other signs) (n = 24); patients with hereditary spastic paraparesis referred consecutively from attending neurologists and the national reference centre in a diagnostic setting (n = 98); and the index case of a four-generation family with autosomal dominant optic neuropathy but no spasticity linked to the SPG7 locus. We identified two SPG7 mutations in 23/134 spastic patients, 21% of the patients selected according to phenotype but only 8% of those referred directly. Our results confirm the pathogenicity of Ala510Val, which was the most frequent mutation in our series (65%) and segregated at the homozygous state with spastic paraparesis in a large family with autosomal recessive inheritance. All SPG7-positive patients tested had optic neuropathy or abnormalities revealed by optical coherence tomography, indicating that abnormalities in optical coherence tomography could be a clinical biomarker for SPG7 testing. In addition, the presence of late-onset very slowly progressive spastic gait (median age 39 years, range 18-52 years) associated with cerebellar ataxia (39%) or cerebellar atrophy (47%) constitute, with abnormal optical coherence tomography, key features pointing towards SPG7-testing. Interestingly, three relatives of patients with heterozygote SPG7 mutations had cerebellar signs and atrophy, or peripheral neuropathy, but no spasticity of the lower limbs, suggesting that SPG7 mutations at the heterozygous state might predispose to late-onset neurodegenerative disorders, mimicking autosomal dominant inheritance. Finally, a novel missense SPG7 mutation at the heterozygous state (Asp411Ala) was identified as the cause of autosomal dominant optic neuropathy in a large family, indicating that some SPG7 mutations can occasionally be dominantly inherited and be an uncommon cause of isolated optic neuropathy. Altogether, these results emphasize the clinical variability associated with SPG7 mutations, ranging from optic neuropathy to spastic paraplegia, and support the view that SPG7 screening should be carried out in both conditions.
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182
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Quirós PM, Ramsay AJ, López-Otín C. New roles for OMA1 metalloprotease: From mitochondrial proteostasis to metabolic homeostasis. Adipocyte 2013; 2:7-11. [PMID: 23700547 PMCID: PMC3661128 DOI: 10.4161/adip.21999] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
The mitochondrial quality control system is essential for the preservation and regulation of mitochondrial function. This system is formed by a complex machinery that controls and maintains protein function and regulates mitochondrial morphology through a coordinated system of continual fusion and fission events. Impairments in the mitochondrial quality control system through either mutation or deficiency in any of its components, can lead to mitochondrial dysfunction. However, the physiological consequences of these deficiencies remain unknown in most cases. Here, we briefly review the role of the OPA1-OMA1 system in mitochondrial biology, and summarize our recent report on the generation and phenotypic characterization of a model deficient in OMA1, an ATP-independent mitochondrial metalloprotease that participates in mitochondrial quality control. Interestingly, Oma1-deficient mice display an obesity phenotype, characterized by hepatic steatosis, decrease in energy expenditure and defective thermogenic regulation. In addition, our study has provided in vivo evidence of OMA1 function as a mitochondrial quality control protease, inactivating OPA1 under stress conditions and inhibiting mitochondrial fusion. Further, we have demonstrated the essential role of the OMA1-OPA1 system for brown adipose function and how this system regulates metabolic homeostasis in mice.
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183
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Voos W, Ward LA, Truscott KN. The role of AAA+ proteases in mitochondrial protein biogenesis, homeostasis and activity control. Subcell Biochem 2013; 66:223-263. [PMID: 23479443 DOI: 10.1007/978-94-007-5940-4_9] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Mitochondria are specialised organelles that are structurally and functionally integrated into cells in the vast majority of eukaryotes. They are the site of numerous enzymatic reactions, some of which are essential for life. The double lipid membrane of the mitochondrion, that spatially defines the organelle and is necessary for some functions, also creates a physical but semi-permeable barrier to the rest of the cell. Thus to ensure the biogenesis, regulation and maintenance of a functional population of proteins, an autonomous protein handling network within mitochondria is required. This includes resident mitochondrial protein translocation machinery, processing peptidases, molecular chaperones and proteases. This review highlights the contribution of proteases of the AAA+ superfamily to protein quality and activity control within the mitochondrion. Here they are responsible for the degradation of unfolded, unassembled and oxidatively damaged proteins as well as the activity control of some enzymes. Since most knowledge about these proteases has been gained from studies in the eukaryotic microorganism Saccharomyces cerevisiae, much of the discussion here centres on their role in this organism. However, reference is made to mitochondrial AAA+ proteases in other organisms, particularly in cases where they play a unique role such as the mitochondrial unfolded protein response. As these proteases influence mitochondrial function in both health and disease in humans, an understanding of their regulation and diverse activities is necessary.
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Affiliation(s)
- Wolfgang Voos
- Institut für Biochemie und Molekularbiologie (IBMB), Universität Bonn, Nussallee 11, 53115, Bonn, Germany,
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184
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Abstract
FtsH, a member of the AAA (ATPases associated with a variety of cellular activities) family of proteins, is an ATP-dependent protease of ∼71 kDa anchored to the inner membrane. It plays crucial roles in a variety of cellular processes. It is responsible for the degradation of both membrane and cytoplasmic substrate proteins. Substrate proteins are unfolded and translocated through the central pore of the ATPase domain into the proteolytic chamber, where the polypeptide chains are processively degraded into short peptides. FtsH is not only involved in the proteolytic elimination of unnecessary proteins, but also in the proteolytic regulation of a number of cellular functions. Its role in proteolytic regulation is achieved by one of two approaches, either the cellular levels of a regulatory protein are controlled by processive degradation of the entire protein, or the activity of a particular substrate protein is modified by processing. In the latter case, protein processing requires the presence of a stable domain within the substrate. Since FtsH does not have a robust unfolding activity, this stable domain is sufficient to abort processive degradation of the protein - resulting in release of a stable protein fragment.
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Affiliation(s)
- Takashi Okuno
- Department of Material and Biological Chemistry, Faculty of Science, Yamagata University, Yamagata, 990-8560, Japan,
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185
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Bahat A, Perlberg S, Melamed-Book N, Lauria I, Langer T, Orly J. StAR enhances transcription of genes encoding the mitochondrial proteases involved in its own degradation. Mol Endocrinol 2013; 28:208-24. [PMID: 24422629 DOI: 10.1210/me.2013-1275] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Steroidogenic acute regulatory protein (StAR) is essential for steroid hormone synthesis in the adrenal cortex and the gonads. StAR activity facilitates the supply of cholesterol substrate into the inner mitochondrial membranes where conversion of the sterol to a steroid is catalyzed. Mitochondrial import terminates the cholesterol mobilization activity of StAR and leads to mounting accumulation of StAR in the mitochondrial matrix. Our studies suggest that to prevent mitochondrial impairment, StAR proteolysis is executed by at least 2 mitochondrial proteases, ie, the matrix LON protease and the inner membrane complexes of the metalloproteases AFG3L2 and AFG3L2:SPG7/paraplegin. Gonadotropin administration to prepubertal rats stimulated ovarian follicular development associated with increased expression of the mitochondrial protein quality control system. In addition, enrichment of LON and AFG3L2 is evident in StAR-expressing ovarian cells examined by confocal microscopy. Furthermore, reporter studies of the protease promoters examined in the heterologous cell model suggest that StAR expression stimulates up to a 3.5-fold increase in the protease gene transcription. Such effects are StAR-specific, are independent of StAR activity, and failed to occur upon expression of StAR mutants that do not enter the matrix. Taken together, the results of this study suggest the presence of a novel regulatory loop, whereby acute accumulation of an apparent nuisance protein in the matrix provokes a mitochondria to nucleus signaling that, in turn, activates selected transcription of genes encoding the enrichment of mitochondrial proteases relevant for enhanced clearance of StAR.
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Affiliation(s)
- Assaf Bahat
- Department of Biological Chemistry (A.B., S.P., J.O.) and Bio-Imaging Unit (N.M.-B.), The Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem 91904, Israel; and Institute for Genetics (I.L., T.L.), Center for Molecular Medicine, Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases, University of Cologne, 50931 Cologne, Germany
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186
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Almajan ER, Richter R, Paeger L, Martinelli P, Barth E, Decker T, Larsson NG, Kloppenburg P, Langer T, Rugarli EI. AFG3L2 supports mitochondrial protein synthesis and Purkinje cell survival. J Clin Invest 2012; 122:4048-58. [PMID: 23041622 DOI: 10.1172/jci64604] [Citation(s) in RCA: 83] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2012] [Accepted: 08/13/2012] [Indexed: 12/11/2022] Open
Abstract
Mutations in the AFG3L2 gene have been linked to spinocerebellar ataxia type 28 and spastic ataxia-neuropathy syndrome in humans; however, the pathogenic mechanism is still unclear. AFG3L2 encodes a subunit of the mitochondrial m-AAA protease, previously implicated in quality control of misfolded inner mitochondrial membrane proteins and in regulatory functions via processing of specific substrates. Here, we used a conditional Afg3l2 mouse model that allows restricted deletion of the gene in Purkinje cells (PCs) to shed light on the pathogenic cascade in the neurons mainly affected in the human diseases. We demonstrate a cell-autonomous requirement of AFG3L2 for survival of PCs. Examination of PCs prior to neurodegeneration revealed fragmentation and altered distribution of mitochondria in the dendritic tree, indicating that abnormal mitochondrial dynamics is an early event in the pathogenic process. Moreover, PCs displayed features pointing to defects in mitochondrially encoded respiratory chain subunits at early stages. To unravel the underlying mechanism, we examined a constitutive knockout of Afg3l2, which revealed a decreased rate of mitochondrial protein synthesis associated with impaired mitochondrial ribosome assembly. We therefore propose that defective mitochondrial protein synthesis, leading to early-onset fragmentation of the mitochondrial network, is a central causative factor in AFG3L2-related neurodegeneration.
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Affiliation(s)
- Eva R Almajan
- Institute of Zoology, University of Cologne, Cologne, Germany
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187
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Liu YT, Tang BS, Wang JL, Guan WJ, Shen L, Shi YT, Zhou Y, Yan XX, Xia K, Jiang H. Spinocerebellar ataxia type 23 is an uncommon SCA subtype in the Chinese Han population. Neurosci Lett 2012; 528:51-4. [DOI: 10.1016/j.neulet.2012.08.062] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2012] [Revised: 07/26/2012] [Accepted: 08/12/2012] [Indexed: 10/27/2022]
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188
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Hekman KE, Yu GY, Brown CD, Zhu H, Du X, Gervin K, Undlien DE, Peterson A, Stevanin G, Clark HB, Pulst SM, Bird TD, White KP, Gomez CM. A conserved eEF2 coding variant in SCA26 leads to loss of translational fidelity and increased susceptibility to proteostatic insult. Hum Mol Genet 2012; 21:5472-83. [PMID: 23001565 DOI: 10.1093/hmg/dds392] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The autosomal dominant spinocerebellar ataxias (SCAs) are a genetically heterogeneous group of disorders exhibiting cerebellar atrophy and Purkinje cell degeneration whose subtypes arise from 31 distinct genetic loci. Our group previously published the locus for SCA26 on chromosome 19p13.3. In this study, we performed targeted deep sequencing of the critical interval in order to identify candidate causative variants in individuals from the SCA26 family. We identified a single variant that co-segregates with the disease phenotype that produces a single amino acid substitution in eukaryotic elongation factor 2. This substitution, P596H, sits in a domain critical for maintaining reading frame during translation. The yeast equivalent, P580H EF2, demonstrated impaired translocation, detected as an increased rate of -1 programmed ribosomal frameshift read-through in a dual-luciferase assay for observing translational recoding. This substitution also results in a greater susceptibility to proteostatic disruption, as evidenced by a more robust activation of a reporter gene driven by unfolded protein response activation upon challenge with dithiothreitol or heat shock in our yeast model system. Our results present a compelling candidate mutation and mechanism for the pathogenesis of SCA26 and further support the role of proteostatic disruption in neurodegenerative diseases.
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Affiliation(s)
- Katherine E Hekman
- Department of Neurology, Institute for Genomics and Systems Biology, University of Chicago, Chicago, IL 60637, USA
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189
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van Gassen KLI, van der Heijden CDCC, de Bot ST, den Dunnen WFA, van den Berg LH, Verschuuren-Bemelmans CC, Kremer HPH, Veldink JH, Kamsteeg EJ, Scheffer H, van de Warrenburg BP. Genotype-phenotype correlations in spastic paraplegia type 7: a study in a large Dutch cohort. ACTA ACUST UNITED AC 2012; 135:2994-3004. [PMID: 22964162 DOI: 10.1093/brain/aws224] [Citation(s) in RCA: 91] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Spastic paraplegia type 7 is an autosomal recessive neurodegenerative disorder mainly characterized by progressive bilateral lower limb spasticity and referred to as a form of hereditary spastic paraplegia. Additional disease features may also be observed as part of a more complex phenotype. Many different mutations have already been identified, but no genotype-phenotype correlations have been found so far. From a total of almost 800 patients referred for testing, we identified 60 patients with mutations in the SPG7 gene. We identified 14 previously unreported mutations and detected a high recurrence rate of several earlier reported mutations. We were able to collect detailed clinical data for 49 patients, who were ranked based on a pure versus complex phenotype, ataxia versus no ataxia and missense versus null mutations. A generally complex phenotype occurred in 69% of all patients and was associated with a younger age at onset (trend with P = 0.07). Ataxia was observed in 57% of all patients. We found that null mutations were associated with the co-occurrence of cerebellar ataxia (trend with P = 0.06). The c.1409 G > A (p.Arg470Gln) mutation, which was found homozygously in two sibs, was associated with a specific complex phenotype that included predominant visual loss due to optical nerve atrophy. Neuropathology in one of these cases showed severe degeneration of the optic system, with less severe degeneration of the ascending tracts of the spinal cord and cerebellum. Other disease features encountered in this cohort included cervical dystonia, vertical gaze palsy, ptosis and severe intellectual disability. In this large Dutch cohort, we seem to have identified the first genotype-phenotype correlation in spastic paraplegia type 7 by observing an association between the cerebellar phenotype of spastic paraplegia type 7 and SPG7 null alleles. An overlapping phenotypic presentation with its biological counterpart AFG3L2, which when mutated causes spinocerebellar ataxia type 28, is apparent and possibly suggests that abnormal levels of the SPG7 protein impact the function of the mitochondrial ATPases associated with diverse cellular activities-protease complex (formed by SPG7 and AFG3L2) in the cerebellum. In addition, a missense mutation in exon 10 resulted in predominant optical nerve atrophy, which might suggest deleterious interactions of this SPG7 variant with its substrate OPA1, the mutated gene product in optic atrophy type 1. Functional studies are required to further investigate these interactions.
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Affiliation(s)
- Koen L I van Gassen
- Department of Human Genetics, Institute for Genetic and Metabolic Disease, Radboud University Nijmegen Medical Centre, Nijmegen, 6500 HB, The Netherlands.
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190
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Pearce S, Nezich CL, Spinazzola A. Mitochondrial diseases: translation matters. Mol Cell Neurosci 2012; 55:1-12. [PMID: 22986124 DOI: 10.1016/j.mcn.2012.08.013] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2012] [Revised: 08/22/2012] [Accepted: 08/25/2012] [Indexed: 11/30/2022] Open
Abstract
Mitochondrial diseases comprise a heterogeneous group of disorders characterized by compromised energy production. Since the early days of mitochondrial medical genetics, it has been known that these can be caused by defects in mitochondrial protein synthesis. However, only in recent years have we begun to develop a broader picture of the array of proteins required for mitochondrial translation. With this new knowledge has come the realization that there are many more neurological and other, diseases attributable to impaired mitochondrial translation than previously thought. Perturbation of any part of this intricate machinery, from the primary sequence of transfer or ribosomal RNAs, to the proteolytic processing of ribosomal proteins, can cause mitochondrial dysfunction and disease. In this review we discuss the current understanding of the mechanisms and factors involved in mammalian mitochondrial translation, and the diverse pathologies resulting when it malfunctions. This article is part of a Special Issue entitled 'Mitochondrial function and dysfunction in neurodegeneration'.
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Affiliation(s)
- Sarah Pearce
- MRC Mitochondrial Biology Unit, Wellcome Trust-MRC Building, Hills Road Cambridge, CB2 0XY, UK
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191
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Abstract
The hereditary cerebellar ataxias are a clinically and genetically heterogeneous group of disorders that primarily affect the cerebellum; often there are additional features such as neuropathy, cognitive decline, or maculopathy that help define the clinical subtype of ataxia. They are commonly classified according to their mode of inheritance into autosomal dominant, autosomal recessive, X-linked, and mitochondrial forms. Great advances have been made in understanding the genetics of cerebellar ataxias in the last 15 years. At least 36 different forms of ADCA are known, 20 autosomal-recessive, two X-linked, and several forms of ataxia associated with mitochondrial defects are known to date. However, in about 40 % of suspected genetically determined ataxia cases, the underlying genetic defect remains undetermined. Although the majority of disease genes have been found in the last two decades, over the last 2 years the genetics has undergone a methodological revolution. New DNA sequencing technologies are enabling us to investigate the whole or large targeted proportions of the genome in a rapid, affordable, and comprehensive way. Exome and targeted sequencing has recently identified four new genes causing ataxia: TGM6, ANO10, SYT14, and rundataxin. This approach is likely to continue to discover new ataxia genes and make screening of existing genes more effective. Translating the genetic findings into isolated and overlapping disease pathways will help stratify patient groups and identify therapeutic targets for ataxia that have so far remained undiscovered.
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Affiliation(s)
- Anna Sailer
- Department of Molecular Neuroscience, Institute of Neurology, Queen Square, London WC1N 3BG, United Kingdom
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192
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Maltecca F, De Stefani D, Cassina L, Consolato F, Wasilewski M, Scorrano L, Rizzuto R, Casari G. Respiratory dysfunction by AFG3L2 deficiency causes decreased mitochondrial calcium uptake via organellar network fragmentation. Hum Mol Genet 2012; 21:3858-70. [PMID: 22678058 PMCID: PMC3412383 DOI: 10.1093/hmg/dds214] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2012] [Accepted: 05/29/2012] [Indexed: 11/28/2022] Open
Abstract
The mitochondrial protein AFG3L2 forms homo-oligomeric and hetero-oligomeric complexes with paraplegin in the inner mitochondrial membrane, named m-AAA proteases. These complexes are in charge of quality control of misfolded proteins and participate in the regulation of OPA1 proteolytic cleavage, required for mitochondrial fusion. Mutations in AFG3L2 cause spinocerebellar ataxia type 28 and a complex neurodegenerative syndrome of childhood. In this study, we demonstrated that the loss of AFG3L2 in mouse embryonic fibroblasts (MEFs) reduces mitochondrial Ca(2+) uptake capacity. This defect is neither a consequence of global alteration in cellular Ca(2+) homeostasis nor of the reduced driving force for Ca(2+) internalization within mitochondria, since cytosolic Ca(2+) transients and mitochondrial membrane potential remain unaffected. Moreover, experiments in permeabilized cells revealed unaltered mitochondrial Ca(2+) uptake speed in Afg3l2(-/-) cells, indicating the presence of functional Ca(2+) uptake machinery. Our results show that the defective Ca(2+) handling in Afg3l2(-/-) cells is caused by fragmentation of the mitochondrial network, secondary to respiratory dysfunction and the consequent processing of OPA1. This leaves a number of mitochondria devoid of connections to the ER and thus without Ca(2+) elevations, hampering the proper Ca(2+) diffusion along the mitochondrial network. The recovery of mitochondrial fragmentation in Afg3l2(-/-) MEFs by overexpression of OPA1 rescues the impaired mitochondrial Ca(2+) buffering, but fails to restore respiration. By linking mitochondrial morphology and Ca(2+) homeostasis, these findings shed new light in the molecular mechanisms underlining neurodegeneration caused by AFG3L2 mutations.
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Affiliation(s)
- Francesca Maltecca
- San Raffaele Scientific Institute, Vita-Salute San Raffaele University and Center for Translational Genomics and Bioinformatics, Milan-I, Italy
| | - Diego De Stefani
- Department of Biomedical Sciences, University of Padova, Padova-I, Italy
| | - Laura Cassina
- San Raffaele Scientific Institute, Vita-Salute San Raffaele University and Center for Translational Genomics and Bioinformatics, Milan-I, Italy
- Department of Genetics, Biology and Biochemistry, University of Turin, Turin-I, Italy
| | - Francesco Consolato
- San Raffaele Scientific Institute, Vita-Salute San Raffaele University and Center for Translational Genomics and Bioinformatics, Milan-I, Italy
- PhD school of Neurobiology, University of Insubria, Varese-I, Italy
| | - Michal Wasilewski
- Department of Cell Physiology and Metabolism, University of Geneva Medical School, Genève-CH, Switzerland and Dulbecco-Telethon Institute, Padova-I, Italy
| | - Luca Scorrano
- Department of Cell Physiology and Metabolism, University of Geneva Medical School, Genève-CH, Switzerland and Dulbecco-Telethon Institute, Padova-I, Italy
| | - Rosario Rizzuto
- Department of Biomedical Sciences, University of Padova, Padova-I, Italy
| | - Giorgio Casari
- San Raffaele Scientific Institute, Vita-Salute San Raffaele University and Center for Translational Genomics and Bioinformatics, Milan-I, Italy
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193
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Petrakis S, Raskó T, Russ J, Friedrich RP, Stroedicke M, Riechers SP, Muehlenberg K, Möller A, Reinhardt A, Vinayagam A, Schaefer MH, Boutros M, Tricoire H, Andrade-Navarro MA, Wanker EE. Identification of human proteins that modify misfolding and proteotoxicity of pathogenic ataxin-1. PLoS Genet 2012; 8:e1002897. [PMID: 22916034 PMCID: PMC3420947 DOI: 10.1371/journal.pgen.1002897] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2011] [Accepted: 07/02/2012] [Indexed: 02/06/2023] Open
Abstract
Proteins with long, pathogenic polyglutamine (polyQ) sequences have an enhanced propensity to spontaneously misfold and self-assemble into insoluble protein aggregates. Here, we have identified 21 human proteins that influence polyQ-induced ataxin-1 misfolding and proteotoxicity in cell model systems. By analyzing the protein sequences of these modifiers, we discovered a recurrent presence of coiled-coil (CC) domains in ataxin-1 toxicity enhancers, while such domains were not present in suppressors. This suggests that CC domains contribute to the aggregation- and toxicity-promoting effects of modifiers in mammalian cells. We found that the ataxin-1-interacting protein MED15, computationally predicted to possess an N-terminal CC domain, enhances spontaneous ataxin-1 aggregation in cell-based assays, while no such effect was observed with the truncated protein MED15ΔCC, lacking such a domain. Studies with recombinant proteins confirmed these results and demonstrated that the N-terminal CC domain of MED15 (MED15CC) per se is sufficient to promote spontaneous ataxin-1 aggregation in vitro. Moreover, we observed that a hybrid Pum1 protein harboring the MED15CC domain promotes ataxin-1 aggregation in cell model systems. In strong contrast, wild-type Pum1 lacking a CC domain did not stimulate ataxin-1 polymerization. These results suggest that proteins with CC domains are potent enhancers of polyQ-mediated protein misfolding and aggregation in vitro and in vivo.
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Affiliation(s)
- Spyros Petrakis
- Neuroproteomics, Max Delbrueck Center for Molecular Medicine, Berlin, Germany
| | - Tamás Raskó
- Neuroproteomics, Max Delbrueck Center for Molecular Medicine, Berlin, Germany
| | - Jenny Russ
- Neuroproteomics, Max Delbrueck Center for Molecular Medicine, Berlin, Germany
| | - Ralf P. Friedrich
- Neuroproteomics, Max Delbrueck Center for Molecular Medicine, Berlin, Germany
| | - Martin Stroedicke
- Neuroproteomics, Max Delbrueck Center for Molecular Medicine, Berlin, Germany
| | | | - Katja Muehlenberg
- Neuroproteomics, Max Delbrueck Center for Molecular Medicine, Berlin, Germany
| | - Angeli Möller
- Neuroproteomics, Max Delbrueck Center for Molecular Medicine, Berlin, Germany
| | - Anita Reinhardt
- Unité BFA (EAC 7059), Université Paris Diderot-Paris7/CNRS, Paris, France
| | | | - Martin H. Schaefer
- Computational Biology and Data Mining, Max Delbrueck Center for Molecular Medicine, Berlin, Germany
| | - Michael Boutros
- Division of Signaling and Functional Genomics, German Cancer Research Center, Heidelberg, Germany
| | - Hervé Tricoire
- Unité BFA (EAC 7059), Université Paris Diderot-Paris7/CNRS, Paris, France
| | | | - Erich E. Wanker
- Neuroproteomics, Max Delbrueck Center for Molecular Medicine, Berlin, Germany
- * E-mail:
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194
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Bettencourt C, Quintáns B, Ros R, Ampuero I, Yáñez Z, Pascual SI, de Yébenes JG, Sobrido MJ. Revisiting genotype-phenotype overlap in neurogenetics: Triplet-repeat expansions mimicking spastic paraplegias. Hum Mutat 2012; 33:1315-23. [DOI: 10.1002/humu.22148] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2012] [Accepted: 06/06/2012] [Indexed: 01/12/2023]
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195
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Hersheson J, Haworth A, Houlden H. The inherited ataxias: Genetic heterogeneity, mutation databases, and future directions in research and clinical diagnostics. Hum Mutat 2012; 33:1324-32. [DOI: 10.1002/humu.22132] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2012] [Accepted: 05/25/2012] [Indexed: 12/25/2022]
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196
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Seidel K, Siswanto S, Brunt ERP, den Dunnen W, Korf HW, Rüb U. Brain pathology of spinocerebellar ataxias. Acta Neuropathol 2012; 124:1-21. [PMID: 22684686 DOI: 10.1007/s00401-012-1000-x] [Citation(s) in RCA: 278] [Impact Index Per Article: 23.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2012] [Revised: 05/25/2012] [Accepted: 05/25/2012] [Indexed: 12/22/2022]
Abstract
The autosomal dominant cerebellar ataxias (ADCAs) represent a heterogeneous group of neurodegenerative diseases with progressive ataxia and cerebellar degeneration. The current classification of this disease group is based on the underlying genetic defects and their typical disease courses. According to this categorization, ADCAs are divided into the spinocerebellar ataxias (SCAs) with a progressive disease course, and the episodic ataxias (EA) with episodic occurrences of ataxia. The prominent disease symptoms of the currently known and genetically defined 31 SCA types result from damage to the cerebellum and interconnected brain grays and are often accompanied by more specific extra-cerebellar symptoms. In the present review, we report the genetic and clinical background of the known SCAs and present the state of neuropathological investigations of brain tissue from SCA patients in the final disease stages. Recent findings show that the brain is commonly seriously affected in the polyglutamine SCAs (i.e. SCA1, SCA2, SCA3, SCA6, SCA7, and SCA17) and that the patterns of brain damage in these diseases overlap considerably in patients suffering from advanced disease stages. In the more rarely occurring non-polyglutamine SCAs, post-mortem neuropathological data currently are scanty and investigations have been primarily performed in vivo by means of MRI brain imaging. Only a minority of SCAs exhibit symptoms and degenerative patterns allowing for a clear and unambiguous diagnosis of the disease, e.g. retinal degeneration in SCA7, tau aggregation in SCA11, dentate calcification in SCA20, protein depositions in the Purkinje cell layer in SCA31, azoospermia in SCA32, and neurocutaneous phenotype in SCA34. The disease proteins of polyglutamine ataxias and some non-polyglutamine ataxias aggregate as cytoplasmic or intranuclear inclusions and serve as morphological markers. Although inclusions may impair axonal transport, bind transcription factors, and block protein quality control, detailed molecular and pathogenetic consequences remain to be determined.
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Affiliation(s)
- Kay Seidel
- Dr. Senckenbergisches Chronomedizinisches Institut, Goethe University, Theodor-Stern-Kai 7, 60950, Frankfurt/Main, Germany
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197
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Anand R, Langer T, Baker MJ. Proteolytic control of mitochondrial function and morphogenesis. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2012; 1833:195-204. [PMID: 22749882 DOI: 10.1016/j.bbamcr.2012.06.025] [Citation(s) in RCA: 76] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/06/2012] [Revised: 06/08/2012] [Accepted: 06/15/2012] [Indexed: 12/18/2022]
Abstract
Mitochondrial proteostasis depends on a hierarchical system of tightly controlled quality surveillance mechanisms. Proteases within mitochondria take center stage in this network. They eliminate misfolded and damaged proteins and ensure the biogenesis and morphogenesis of mitochondria by processing or degrading short-lived regulatory proteins. Mitochondrial gene expression, the mitochondrial phospholipid metabolism and the fusion of mitochondrial membranes are under proteolytic control. Furthermore, in response to stress and mitochondrial dysfunction, proteolysis inhibits fusion and facilitates mitophagy and apoptosis. Defining these versatile activities of mitochondrial proteases will be pivotal for understanding the pathogenesis of various neurodegenerative disorders associated with defective mitochondria-associated proteolysis. This article is part of a Special Issue entitled: Mitochondrial dynamics and physiology.
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198
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Jia D, Tang B, Chen Z, Shi Y, Sun Z, Zhang L, Wang J, Xia K, Jiang H. Spinocerebellar Ataxia Type 28 (SCA28) is an Uncommon Cause of Dominant Ataxia Among Chinese Kindreds. Int J Neurosci 2012; 122:560-2. [DOI: 10.3109/00207454.2012.690796] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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199
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Lowth BR, Kirstein-Miles J, Saiyed T, Brötz-Oesterhelt H, Morimoto RI, Truscott KN, Dougan DA. Substrate recognition and processing by a Walker B mutant of the human mitochondrial AAA+ protein CLPX. J Struct Biol 2012; 179:193-201. [PMID: 22710082 DOI: 10.1016/j.jsb.2012.06.001] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2012] [Revised: 05/14/2012] [Accepted: 06/07/2012] [Indexed: 10/28/2022]
Abstract
The mitochondrial matrix of mammalian cells contains several different ATP-dependent proteases, including CLPXP, some of which contribute to protein maturation and quality control. Currently however, the substrates and the physiological roles of mitochondrial CLPXP in humans, has remained elusive. Similarly, the mechanism by which these ATP-dependent proteases recognize their substrates currently remains unclear. Here we report the characterization of a Walker B mutation in human CLPX, in which the highly conserved glutamate was replaced with alanine. This mutant protein exhibits improved interaction with the model unfolded substrate casein and several putative physiological substrates in vitro. Although this mutant lacks ATPase activity, it retains the ability to mediate casein degradation by hCLPP, in a fashion similar to the small molecule ClpP-activator, ADEP. Our functional dissection of hCLPX structure, also identified that most model substrates are recognized by the N-terminal domain, although some substrates bypass this step and dock, directly to the pore-1 motif. Collectively these data reveal, that despite the difference between bacterial and human CLPXP complexes, human CLPXP exhibits a similar mode of substrate recognition and is deregulated by ADEPs.
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Affiliation(s)
- Bradley R Lowth
- Department of Biochemistry, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Victoria 3086, Australia
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200
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Shutt TE, McBride HM. Staying cool in difficult times: mitochondrial dynamics, quality control and the stress response. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2012; 1833:417-24. [PMID: 22683990 DOI: 10.1016/j.bbamcr.2012.05.024] [Citation(s) in RCA: 114] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/29/2012] [Revised: 05/21/2012] [Accepted: 05/22/2012] [Indexed: 12/30/2022]
Abstract
One of the critical problems with the combustion of sugar and fat is the generation of cellular oxidation. The ongoing consumption of oxygen results in damage to lipids, protein and mtDNA, which must be repaired through essential pathways in mitochondrial quality control. It has long been established that intrinsic protease pathways within the matrix and intermembrane space actively degrade unfolded and oxidized mitochondrial proteins. However, more recent work into the field of quality control has established distinct roles for both mitochondrial fragmentation and hyperfusion in different aspects of quality control and survival. In addition, mitochondrial derived vesicles have recently been shown to carry cargo directly to the lysosome, adding further insight into the integration of mitochondrial dynamics in cellular homeostasis. This review will focus on the mechanisms and emerging questions concerning the links between mitochondrial dynamics and quality control. This article is part of a Special Issue entitled: Protein Import and Quality Control in Mitochondria and Plastids.
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Affiliation(s)
- Timothy E Shutt
- University of Ottawa Heart Institute, 40 Ruskin St., Ottawa, ON, Canada K1Y 4W7
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