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Chen S, Collart MA. Membrane-associated mRNAs: A Post-transcriptional Pathway for Fine-turning Gene Expression. J Mol Biol 2024; 436:168579. [PMID: 38648968 DOI: 10.1016/j.jmb.2024.168579] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2023] [Revised: 04/14/2024] [Accepted: 04/16/2024] [Indexed: 04/25/2024]
Abstract
Gene expression is a fundamental and highly regulated process involving a series of tightly coordinated steps, including transcription, post-transcriptional processing, translation, and post-translational modifications. A growing number of studies have revealed an additional layer of complexity in gene expression through the phenomenon of mRNA subcellular localization. mRNAs can be organized into membraneless subcellular structures within both the cytoplasm and the nucleus, but they can also targeted to membranes. In this review, we will summarize in particular our knowledge on localization of mRNAs to organelles, focusing on important regulators and available techniques for studying organellar localization, and significance of this localization in the broader context of gene expression regulation.
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Affiliation(s)
- Siyu Chen
- Department of Microbiology and Molecular Medicine, Faculty of Medicine, University of Geneva, Institute of Genetics and Genomics of Geneva, Geneva, Switzerland.
| | - Martine A Collart
- Department of Microbiology and Molecular Medicine, Faculty of Medicine, University of Geneva, Institute of Genetics and Genomics of Geneva, Geneva, Switzerland.
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2
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Darden C, Donkor JE, Korolkova O, Barozai MYK, Chaudhuri M. Distinct structural motifs are necessary for targeting and import of Tim17 in Trypanosoma brucei mitochondrion. mSphere 2024; 9:e0055823. [PMID: 38193679 PMCID: PMC10871166 DOI: 10.1128/msphere.00558-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2023] [Accepted: 11/28/2023] [Indexed: 01/10/2024] Open
Abstract
Nuclear-encoded mitochondrial proteins are correctly translocated to their proper sub-mitochondrial destination using location-specific mitochondrial targeting signals and via multi-protein import machineries (translocases) in the outer and inner mitochondrial membranes (TOM and TIMs, respectively). However, targeting signals of multi-pass Tims are less defined. Here, we report the characterization of the targeting signals of Trypanosoma brucei Tim17 (TbTim17), an essential component of the most divergent TIM complex. TbTim17 possesses a characteristic secondary structure including four predicted transmembrane (TM) domains in the center with hydrophilic N- and C-termini. After examining mitochondrial localization of various deletion and site-directed mutants of TbTim17 in T. brucei using subcellular fractionation and confocal microscopy, we located at least two internal targeting signals (ITS): (i) within TM1 (31-50 AAs) and (ii) TM4 + loop 3 (120-136 AAs). Both signals are required for proper targeting and integration of TbTim17 in the membrane. Furthermore, a positively charged residue (K122) is critical for mitochondrial localization of TbTim17. This is the first report of characterizing the ITS for a multipass inner membrane protein in a divergent eukaryote, like T. brucei.IMPORTANCEAfrican trypanosomiasis (AT) is a deadly disease in human and domestic animals, caused by the parasitic protozoan Trypanosoma brucei. Therefore, AT is not only a concern for human health but also for economic development in the vast area of sub-Saharan Africa. T. brucei possesses a single mitochondrion per cell that imports hundreds of nuclear-encoded mitochondrial proteins for its functions. T. brucei Tim17 (TbTim17), an essential component of the TbTIM17 complex, is a nuclear-encoded protein; thus, it is necessary to be imported from the cytosol to form the TbTIM17 complex. Here, we demonstrated that the internal targeting signals within the transmembrane 1 (TM1) and TM4 with loop 3, and residue K122 are required collectively for import and integration of TbTim17 in the T. brucei mitochondrion. This information could be utilized to block TbTim17 function and parasite growth.
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Affiliation(s)
- Chauncey Darden
- Department of Biochemistry, Cancer Biology, Neuroscience, and Pharmacology, Meharry Medical College, Nashville, Tennessee, USA
| | - Joseph E. Donkor
- Department of Microbiology, Immunology, and Physiology, Meharry Medical College, Nashville, Tennessee, USA
| | - Olga Korolkova
- The Consolidated Research Instrumentation, Informatics, Statistics, and Learning Integration Suite (CRISALIS), Meharry Medical College, Nashville, Tennessee, USA
| | | | - Minu Chaudhuri
- Department of Microbiology, Immunology, and Physiology, Meharry Medical College, Nashville, Tennessee, USA
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3
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Nieto-Panqueva F, Rubalcava-Gracia D, Hamel PP, González-Halphen D. The constraints of allotopic expression. Mitochondrion 2023; 73:30-50. [PMID: 37739243 DOI: 10.1016/j.mito.2023.09.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2023] [Revised: 08/28/2023] [Accepted: 09/18/2023] [Indexed: 09/24/2023]
Abstract
Allotopic expression is the functional transfer of an organellar gene to the nucleus, followed by synthesis of the gene product in the cytosol and import into the appropriate organellar sub compartment. Here, we focus on mitochondrial genes encoding OXPHOS subunits that were naturally transferred to the nucleus, and critically review experimental evidence that claim their allotopic expression. We emphasize aspects that may have been overlooked before, i.e., when modifying a mitochondrial gene for allotopic expression━besides adapting the codon usage and including sequences encoding mitochondrial targeting signals━three additional constraints should be considered: (i) the average apparent free energy of membrane insertion (μΔGapp) of the transmembrane stretches (TMS) in proteins earmarked for the inner mitochondrial membrane, (ii) the final, functional topology attained by each membrane-bound OXPHOS subunit; and (iii) the defined mechanism by which the protein translocator TIM23 sorts cytosol-synthesized precursors. The mechanistic constraints imposed by TIM23 dictate the operation of two pathways through which alpha-helices in TMS are sorted, that eventually determine the final topology of membrane proteins. We used the biological hydrophobicity scale to assign an average apparent free energy of membrane insertion (μΔGapp) and a "traffic light" color code to all TMS of OXPHOS membrane proteins, thereby predicting which are more likely to be internalized into mitochondria if allotopically produced. We propose that the design of proteins for allotopic expression must make allowance for μΔGapp maximization of highly hydrophobic TMS in polypeptides whose corresponding genes have not been transferred to the nucleus in some organisms.
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Affiliation(s)
- Felipe Nieto-Panqueva
- Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico City, Mexico
| | - Diana Rubalcava-Gracia
- Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico City, Mexico; Division of Molecular Metabolism, Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm, Sweden
| | - Patrice P Hamel
- Department of Molecular Genetics and Department of Biological Chemistry and Pharmacology, Ohio State University, Columbus, OH, USA; Vellore Institute of Technology (VIT), School of BioScience and Technology, Vellore, Tamil Nadu, India
| | - Diego González-Halphen
- Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico City, Mexico.
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Darden C, Donkor J, Korolkova O, Khan Barozai MY, Chaudhuri M. Distinct structural motifs are necessary for targeting and import of Tim17 in Trypanosoma brucei mitochondrion. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.07.07.548172. [PMID: 37461662 PMCID: PMC10350046 DOI: 10.1101/2023.07.07.548172] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/23/2024]
Abstract
Nuclear-encoded mitochondrial proteins are correctly translocated to their proper sub-mitochondrial destination using location specific mitochondrial targeting signals (MTSs) and via multi-protein import machineries (translocases) in the outer and inner mitochondrial membranes (TOM and TIMs, respectively). However, MTSs of multi-pass Tims are less defined. Here we report the characterization of the MTSs of Trypanosoma brucei Tim17 (TbTim17), an essential component of the most divergent TIM complex. TbTim17 possesses a characteristic secondary structure including four predicted transmembrane (TM) domains in the center with hydrophilic N- and C-termini. After examining mitochondrial localization of various deletion and site-directed mutants of TbTim17 in T. brucei using subcellular fractionation and confocal microscopy we located at least two internal signals, 1) within TM1 (31-50 AAs) and 2) TM4 + Loop 3 (120-136 AAs). Both signals are required for proper targeting and integration of TbTim17 in the membrane. Furthermore, a positively charged residue (K 122 ) is critical for mitochondrial localization of TbTim17. This is the first report of characterizing the internal mitochondrial targeting signals (ITS) for a multipass inner membrane protein in a divergent eukaryote, like T. brucei . Summary Internal targeting signals within the TM1, TM4 with Loop 3, and residue K122 are required collectively for import and integration of TbTim17 in the T. brucei mitochondrion. This information could be utilized to block parasite growth.
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TOMM40 Genetic Variants Cause Neuroinflammation in Alzheimer's Disease. Int J Mol Sci 2023; 24:ijms24044085. [PMID: 36835494 PMCID: PMC9962462 DOI: 10.3390/ijms24044085] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2022] [Revised: 02/10/2023] [Accepted: 02/15/2023] [Indexed: 02/22/2023] Open
Abstract
Translocase of outer mitochondrial membrane 40 (TOMM40) is located in the outer membrane of mitochondria. TOMM40 is essential for protein import into mitochondria. TOMM40 genetic variants are believed to increase the risk of Alzheimer's disease (AD) in different populations. In this study, three exonic variants (rs772262361, rs157581, and rs11556505) and three intronic variants (rs157582, rs184017, and rs2075650) of the TOMM40 gene were identified from Taiwanese AD patients using next-generation sequencing. Associations between the three TOMM40 exonic variants and AD susceptibility were further evaluated in another AD cohort. Our results showed that rs157581 (c.339T > C, p.Phe113Leu, F113L) and rs11556505 (c.393C > T, p.Phe131Leu, F131L) were associated with an increased risk of AD. We further utilized cell models to examine the role of TOMM40 variation in mitochondrial dysfunction that causes microglial activation and neuroinflammation. When expressed in BV2 microglial cells, the AD-associated mutant (F113L) or (F131L) TOMM40 induced mitochondrial dysfunction and oxidative stress-induced activation of microglia and NLRP3 inflammasome. Pro-inflammatory TNF-α, IL-1β, and IL-6 released by mutant (F113L) or (F131L) TOMM40-activated BV2 microglial cells caused cell death of hippocampal neurons. Taiwanese AD patients carrying TOMM40 missense (F113L) or (F131L) variants displayed an increased plasma level of inflammatory cytokines IL-6, IL-18, IL-33, and COX-2. Our results provide evidence that TOMM40 exonic variants, including rs157581 (F113L) and rs11556505 (F131L), increase the AD risk of the Taiwanese population. Further studies suggest that AD-associated mutant (F113L) or (F131L) TOMM40 cause the neurotoxicity of hippocampal neurons by inducing the activation of microglia and NLRP3 inflammasome and the release of pro-inflammatory cytokines.
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Sulkshane P, Ram J, Glickman MH. Ubiquitination of Intramitochondrial Proteins: Implications for Metabolic Adaptability. Biomolecules 2020; 10:biom10111559. [PMID: 33207558 PMCID: PMC7697252 DOI: 10.3390/biom10111559] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2020] [Revised: 11/11/2020] [Accepted: 11/12/2020] [Indexed: 02/07/2023] Open
Abstract
Mitochondria are constantly subjected to stressful conditions due to their unique physiology and organization. The resulting damage leads to mitochondrial dysfunction, which underlies many pathophysiological conditions. Hence, constant surveillance is required to closely monitor mitochondrial health for sound maintenance of cellular metabolism and thus, for viability. In addition to internal mitochondrial chaperones and proteases, mitochondrial health is also governed by host cell protein quality control systems. The ubiquitin-proteasome system (UPS) and autophagy constitute the main pathways for removal of damaged or superfluous proteins in the cytosol, nucleus, and from certain organelles such as the Endoplasmic Reticulum (ER) and mitochondria. Although stress-induced ubiquitin-dependent degradation of mitochondrial outer membrane proteins has been widely studied, mechanisms of intramitochondrial protein ubiquitination has remained largely elusive due to the predominantly cytosolic nature of UPS components, separated from internal mitochondrial proteins by a double membrane. However, recent research has illuminated examples of intramitochondrial protein ubiquitination pathways and highlighted their importance under basal and stressful conditions. Owing to the dependence of mitochondria on the error-prone process of protein import from the cytosol, it is imperative that the cell eliminate any accumulated proteins in the event of mitochondrial protein import deficiency. Apparently, a significant portion of this activity involves ubiquitination in one way or another. In the present review article, following a brief introduction to mitochondrial protein quality control mechanisms, we discuss our recent understanding of intramitochondrial protein ubiquitination, its importance for basal function of mitochondria, metabolic implications, and possible therapeutic applications.
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Affiliation(s)
- Prasad Sulkshane
- Correspondence: (P.S.); (M.H.G.); Tel.: +972-58779-2319 (P.S.); +972-4-829-4552 (M.H.G.)
| | | | - Michael H Glickman
- Correspondence: (P.S.); (M.H.G.); Tel.: +972-58779-2319 (P.S.); +972-4-829-4552 (M.H.G.)
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The presence of disulfide bonds reveals an evolutionarily conserved mechanism involved in mitochondrial protein translocase assembly. Sci Rep 2016; 6:27484. [PMID: 27265872 PMCID: PMC4893733 DOI: 10.1038/srep27484] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2015] [Accepted: 05/17/2016] [Indexed: 11/23/2022] Open
Abstract
Disulfide bond formation is crucial for the biogenesis and structure of many proteins that are localized in the intermembrane space of mitochondria. The importance of disulfide bond formation within mitochondrial proteins was extended beyond soluble intermembrane space proteins. Tim22, a membrane protein and core component of the mitochondrial translocase TIM22, forms an intramolecular disulfide bond in yeast. Tim22 belongs to the Tim17/Tim22/Tim23 family of protein translocases. Here, we present evidence of the high evolutionary conservation of disulfide bond formation in Tim17 and Tim22 among fungi and metazoa. Topological models are proposed that include the location of disulfide bonds relative to the predicted transmembrane regions. Yeast and human Tim22 variants that are not oxidized do not properly integrate into the membrane complex. Moreover, the lack of Tim17 oxidation disrupts the TIM23 translocase complex. This underlines the importance of disulfide bond formation for mature translocase assembly through membrane stabilization of weak transmembrane domains.
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The Role of Cardiolipin in Cardiovascular Health. BIOMED RESEARCH INTERNATIONAL 2015; 2015:891707. [PMID: 26301254 PMCID: PMC4537736 DOI: 10.1155/2015/891707] [Citation(s) in RCA: 58] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/21/2015] [Accepted: 07/08/2015] [Indexed: 12/20/2022]
Abstract
Cardiolipin (CL), the signature phospholipid of mitochondrial membranes, is crucial for both mitochondrial function and cellular processes outside of the mitochondria. The importance of CL in cardiovascular health is underscored by the life-threatening genetic disorder Barth syndrome (BTHS), which manifests clinically as cardiomyopathy, skeletal myopathy, neutropenia, and growth retardation. BTHS is caused by mutations in the gene encoding tafazzin, the transacylase that carries out the second CL remodeling step. In addition to BTHS, CL is linked to other cardiovascular diseases (CVDs), including cardiomyopathy, atherosclerosis, myocardial ischemia-reperfusion injury, heart failure, and Tangier disease. The link between CL and CVD may possibly be explained by the physiological roles of CL in pathways that are cardioprotective, including mitochondrial bioenergetics, autophagy/mitophagy, and mitogen activated protein kinase (MAPK) pathways. In this review, we focus on the role of CL in the pathogenesis of CVD as well as the molecular mechanisms that may link CL functions to cardiovascular health.
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9
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Alzheimer's pathogenesis and its link to the mitochondrion. OXIDATIVE MEDICINE AND CELLULAR LONGEVITY 2015; 2015:803942. [PMID: 25973139 PMCID: PMC4417983 DOI: 10.1155/2015/803942] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 12/30/2014] [Revised: 03/16/2015] [Accepted: 04/02/2015] [Indexed: 01/02/2023]
Abstract
Alzheimer's disease (AD) is the most common form of dementia in the elderly. This neurodegenerative disorder is clinically characterized by impairment of cognitive functions and changes in behaviour and personality. The pathogenesis of AD is still unclear. Recent evidence supports some role of mitochondria dysfunction and oxidative stress in the development of the neurodegenerative process. In this review, we discuss the role of mitochondrial dysfunction in AD, focusing on the mechanisms that lead to mitochondrial impairment, oxidative stress, and neurodegeneration, a “vicious circle” that ends in dementia.
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Gornicka A, Bragoszewski P, Chroscicki P, Wenz LS, Schulz C, Rehling P, Chacinska A. A discrete pathway for the transfer of intermembrane space proteins across the outer membrane of mitochondria. Mol Biol Cell 2014; 25:3999-4009. [PMID: 25318675 PMCID: PMC4263444 DOI: 10.1091/mbc.e14-06-1155] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
The TOM translocase serves as a portal for proteins destined to the mitochondrial membranes and matrix. This study determines how proteins targeted to the MIA pathway arrive in the intermembrane space. A different mode of the transport across the outer membrane for intermembrane space proteins with the help of Tom40 is postulated. Mitochondrial proteins are synthesized on cytosolic ribosomes and imported into mitochondria with the help of protein translocases. For the majority of precursor proteins, the role of the translocase of the outer membrane (TOM) and mechanisms of their transport across the outer mitochondrial membrane are well recognized. However, little is known about the mode of membrane translocation for proteins that are targeted to the intermembrane space via the redox-driven mitochondrial intermembrane space import and assembly (MIA) pathway. On the basis of the results obtained from an in organello competition import assay, we hypothesized that MIA-dependent precursor proteins use an alternative pathway to cross the outer mitochondrial membrane. Here we demonstrate that this alternative pathway involves the protein channel formed by Tom40. We sought a translocation intermediate by expressing tagged versions of MIA-dependent proteins in vivo. We identified a transient interaction between our model substrates and Tom40. Of interest, outer membrane translocation did not directly involve other core components of the TOM complex, including Tom22. Thus MIA-dependent proteins take another route across the outer mitochondrial membrane that involves Tom40 in a form that is different from the canonical TOM complex.
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Affiliation(s)
- Agnieszka Gornicka
- International Institute of Molecular and Cell Biology, 02-109 Warsaw, Poland
| | - Piotr Bragoszewski
- International Institute of Molecular and Cell Biology, 02-109 Warsaw, Poland
| | - Piotr Chroscicki
- International Institute of Molecular and Cell Biology, 02-109 Warsaw, Poland
| | - Lena-Sophie Wenz
- Institut für Biochemie und Molekularbiologie, ZBMZ, Universität Freiburg, D-79104 Freiburg, Germany
| | - Christian Schulz
- Department of Cellular Biochemistry, University Medical Center Göttingen, D-37073 Göttingen, Germany
| | - Peter Rehling
- Department of Cellular Biochemistry, University Medical Center Göttingen, D-37073 Göttingen, Germany
| | - Agnieszka Chacinska
- International Institute of Molecular and Cell Biology, 02-109 Warsaw, Poland
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11
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Highly divergent mitochondrion-related organelles in anaerobic parasitic protozoa. Biochimie 2014; 100:3-17. [DOI: 10.1016/j.biochi.2013.11.018] [Citation(s) in RCA: 103] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2013] [Accepted: 11/24/2013] [Indexed: 11/20/2022]
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12
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Su B, Ryan RO. Metabolic biology of 3-methylglutaconic acid-uria: a new perspective. J Inherit Metab Dis 2014; 37:359-68. [PMID: 24407466 PMCID: PMC4016128 DOI: 10.1007/s10545-013-9669-0] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/22/2013] [Revised: 11/20/2013] [Accepted: 11/26/2013] [Indexed: 10/25/2022]
Abstract
Over the past 25 years a growing number of distinct syndromes/mutations associated with compromised mitochondrial function have been identified that share a common feature: urinary excretion of 3-methylglutaconic acid (3MGA). In the leucine degradation pathway, carboxylation of 3-methylcrotonyl CoA leads to formation of 3-methylglutaconyl CoA while 3-methylglutaconyl CoA hydratase converts this metabolite to 3-hydroxy-3-methylglutaryl CoA (HMG CoA). In "primary" 3MGA-uria, mutations in the hydratase are directly responsible for the accumulation of 3MGA. On the other hand, in all "secondary" 3MGA-urias, no defect in leucine catabolism exists and the metabolic origin of 3MGA is unknown. Herein, a path to 3MGA from mitochondrial acetyl CoA is proposed. The pathway is initiated when syndrome-associated mutations/DNA deletions result in decreased Krebs cycle flux. When this occurs, acetoacetyl CoA thiolase condenses two acetyl CoA into acetoacetyl CoA plus CoASH. Subsequently, HMG CoA synthase 2 converts acetoacetyl CoA and acetyl CoA to HMG CoA. Under syndrome-specific metabolic conditions, 3-methylglutaconyl CoA hydratase converts HMG CoA into 3-methylglutaconyl CoA in a reverse reaction of the leucine degradation pathway. This metabolite fails to proceed further up the leucine degradation pathway owing to the kinetic properties of 3-methylcrotonyl CoA carboxylase. Instead, hydrolysis of the CoA moiety of 3-methylglutaconyl CoA generates 3MGA, which appears in urine. If experimentally confirmed, this pathway provides an explanation for the occurrence of 3MGA in multiple disorders associated with compromised mitochondrial function.
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Affiliation(s)
- Betty Su
- Children's Hospital Oakland Research Institute, 5700 Martin Luther King Jr. Way, Oakland, CA, 94609, USA
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13
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Weak pulling forces exerted on Nin-orientated transmembrane segments during co-translational insertion into the inner membrane ofEscherichia coli. FEBS Lett 2014; 588:1930-4. [DOI: 10.1016/j.febslet.2014.03.050] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2014] [Revised: 03/24/2014] [Accepted: 03/27/2014] [Indexed: 11/17/2022]
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14
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High expression of the aspartate–glutamate carrier Aralar1 favors lactate consumption in CHO cell culture. ACTA ACUST UNITED AC 2013. [DOI: 10.4155/pbp.13.5] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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Wrobel L, Trojanowska A, Sztolsztener ME, Chacinska A. Mitochondrial protein import: Mia40 facilitates Tim22 translocation into the inner membrane of mitochondria. Mol Biol Cell 2013; 24:543-54. [PMID: 23283984 PMCID: PMC3583659 DOI: 10.1091/mbc.e12-09-0649] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
The MIA pathway governs the localization and oxidative folding of intermembrane space proteins. This study reports that the MIA pathway is involved in the transport of mitochondrial inner membrane protein Tim22, thereby broadening the known functions of MIA to the biogenesis of inner membrane proteins. The mitochondrial intermembrane space assembly (MIA) pathway is generally considered to be dedicated to the redox-dependent import and biogenesis of proteins localized to the intermembrane space of mitochondria. The oxidoreductase Mia40 is a central component of the pathway responsible for the transfer of disulfide bonds to intermembrane space precursor proteins, causing their oxidative folding. Here we present the first evidence that the function of Mia40 is not restricted to the transport and oxidative folding of intermembrane space proteins. We identify Tim22, a multispanning membrane protein and core component of the TIM22 translocase of inner membrane, as a protein with cysteine residues undergoing oxidation during Tim22 biogenesis. We show that Mia40 is involved in the biogenesis and complex assembly of Tim22. Tim22 forms a disulfide-bonded intermediate with Mia40 upon import into mitochondria. Of interest, Mia40 binds the Tim22 precursor also via noncovalent interactions. We propose that Mia40 not only is responsible for disulfide bond formation, but also assists the Tim22 protein in its integration into the inner membrane of mitochondria.
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Affiliation(s)
- Lidia Wrobel
- International Institute of Molecular and Cell Biology, 02-109 Warsaw, Poland
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16
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Zhang Y, Xu Y, Zhao Q, Ji Z, Deng H, Li SJ. The structural characteristics of human preprotein translocase of the inner mitochondrial membrane Tim23: Implications for its physiological activities. Protein Expr Purif 2012; 82:255-62. [DOI: 10.1016/j.pep.2012.01.009] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2011] [Revised: 01/06/2012] [Accepted: 01/09/2012] [Indexed: 11/26/2022]
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17
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Singha UK, Hamilton V, Duncan MR, Weems E, Tripathi MK, Chaudhuri M. Protein translocase of mitochondrial inner membrane in Trypanosoma brucei. J Biol Chem 2012; 287:14480-93. [PMID: 22408251 DOI: 10.1074/jbc.m111.322925] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Translocases of mitochondrial inner membrane (TIMs) are multiprotein complexes. The only Tim component so far characterized in kinetoplastid parasites such as Trypanosoma brucei is Tim17 (TbTim17), which is essential for cell survival and mitochondrial protein import. Here, we report that TbTim17 is present in a protein complex of about 1,100 kDa, which is much larger than the TIM complexes found in fungi and mammals. Depletion of TbTim17 in T. brucei impairs the mitochondrial import of cytochrome oxidase subunit IV, an N-terminal signal-containing protein. Pretreatment of isolated mitoplasts with the anti-TbTim17 antibody inhibited import of cytochrome oxidase subunit IV, indicating a direct involvement of the TbTim17 in the import process. Purification of the TbTim17-containing protein complex from the mitochondrial membrane of T. brucei by tandem affinity chromatography revealed that TbTim17 associates with seven unique as well as a few known T. brucei mitochondrial proteins. Depletion of three of these novel proteins, i.e. TbTim47, TbTim54, and TbTim62, significantly decreased mitochondrial protein import in vitro. In vivo targeting of a newly synthesized mitochondrial matrix protein, MRP2, was also inhibited due to depletion of TbTim17, TbTim54, and TbTim62. Co-precipitation analysis confirmed the interaction of TbTim54 and TbTim62 with TbTim17 in vivo. Overall, our data reveal that TbTim17, the single homolog of Tim17/22/23 family proteins, is present in a unique TIM complex consisting of novel proteins in T. brucei and is critical for mitochondrial protein import.
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Affiliation(s)
- Ujjal K Singha
- Department of Microbiology and Immunology, Meharry Medical College, Nashville, Tennessee 37208, USA
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Kumar S, Yoshizumi T, Hongo H, Yoneda A, Hara H, Hamasaki H, Takahashi N, Nagata N, Shimada H, Matsui M. Arabidopsis mitochondrial protein TIM50 affects hypocotyl cell elongation through intracellular ATP level. PLANT SCIENCE : AN INTERNATIONAL JOURNAL OF EXPERIMENTAL PLANT BIOLOGY 2012; 183:212-7. [PMID: 22195596 DOI: 10.1016/j.plantsci.2011.08.014] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/15/2011] [Revised: 08/31/2011] [Accepted: 08/31/2011] [Indexed: 05/08/2023]
Abstract
The plant hypocotyl is an excellent model for the analysis of cell elongation. We have characterized a knockout mutant of the Arabidopsis TIM50 gene that showed a reduction in the hypocotyls length of etiolated seedlings. We also found that a knockout of TIM50 caused enlargement and deformation of the mitochondrial structure and a reduction in intracellular ATP levels. TIM50 is a component of the mitochondrial TIM23 inner membrane protein complex and is involved in the import of mitochondrial proteins. The short hypocotyl phenotype was recovered by the addition of Compound C, an inhibitor of AMPK. Thus, the mitochondrial ATP level controls cell elongation in Arabidopsis hypocotyls through possible signaling via AMPK.
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Affiliation(s)
- Shailesh Kumar
- Plant Synthetic Genomics Research Division, Kihara Institute for Biological Research, Yokohama City University, 641-12 Maioka-cho, Totsuka-ku, Yokohama 244-0813, Japan
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Baker MJ, Tatsuta T, Langer T. Quality control of mitochondrial proteostasis. Cold Spring Harb Perspect Biol 2011; 3:cshperspect.a007559. [PMID: 21628427 DOI: 10.1101/cshperspect.a007559] [Citation(s) in RCA: 197] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
A decline in mitochondrial activity has been associated with aging and is a hallmark of many neurological diseases. Surveillance mechanisms acting at the molecular, organellar, and cellular level monitor mitochondrial integrity and ensure the maintenance of mitochondrial proteostasis. Here we will review the central role of mitochondrial chaperones and proteases, the cytosolic ubiquitin-proteasome system, and the mitochondrial unfolded response in this interconnected quality control network, highlighting the dual function of some proteases in protein quality control within the organelle and for the regulation of mitochondrial fusion and mitophagy.
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Affiliation(s)
- Michael J Baker
- Institute for Genetics, Center for Molecular Medicine (CMMC), Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, 50674 Cologne, Germany
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Zhang Y, Xu Y, Zhao Q, Ji Z, Li Q, Li SJ. Expression and structural characterization of human translocase of inner membrane of mitochondria Tim50. Protein Expr Purif 2011; 80:130-7. [PMID: 21742040 DOI: 10.1016/j.pep.2011.06.012] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2011] [Revised: 06/17/2011] [Accepted: 06/21/2011] [Indexed: 11/17/2022]
Abstract
The preprotein translocase of the inner membrane of mitochondria (TIM23 complex) is the main entry gate for proteins of the matrix and the inner membrane. Tim50 is a major receptor in TIM23 complex, which spans the inner membrane with a single transmembrane segment and exposes a large hydrophilic domain in the intermembrane space. In this study, we expressed and purified the intermembrane space (IMS) domain of human Tim50 (Tim50(IMS)), and investigated its structural characteristics and assembly behaviors. The far-UV CD spectra of Tim50(IMS) in native and denatured states revealed that the protein has a significantly folded secondary structure consisted of α-helixes and β-sheets. Size exclusion chromatography showed that Tim50(IMS) is a monomer. Furthermore, the results showed, by intrinsic fluorescence, ANS binding, fluorescence anisotropy and fluorescence quenching, that Tim50(IMS) forms a compact structure in the range of pH 8.0-5.0; and it is more compact at pH 8.0 than pH 7.0; when pH decreases below 5.0, the protein is gradually denatured.
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Affiliation(s)
- Yongqiang Zhang
- The Key Laboratory of Bioactive Materials, Ministry of Education, School of Physics Science, Nankai University, Tianjin 300071, PR China
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21
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Danne JC, Waller RF. Analysis of dinoflagellate mitochondrial protein sorting signals indicates a highly stable protein targeting system across eukaryotic diversity. J Mol Biol 2011; 408:643-53. [PMID: 21376056 DOI: 10.1016/j.jmb.2011.02.057] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2010] [Revised: 02/21/2011] [Accepted: 02/24/2011] [Indexed: 11/17/2022]
Abstract
Protein targeting into mitochondria from the cytoplasm is fundamental to the cell biology of all eukaryotes. Our understanding of this process is heavily biased towards "model" organisms, such as animals and fungi, and it is less clear how conserved this process is throughout diverse eukaryotes. In this study, we have surveyed mitochondrial protein sorting signals from a representative of the dinoflagellate algae. Dinoflagellates are a phylum belonging to the group Alveolata, which also includes apicomplexan parasites and ciliates. We generated 46 mitochondrial gene sequences from the dinoflagellate Karlodinium micrum and analysed these for mitochondrial sorting signals. Most of the sequences contain predicted N-terminal peptide extensions that conform to mitochondrial targeting peptides from animals and fungi in terms of length, amino acid composition, and propensity to form amphipathic α-helices. The remainder lack predicted mitochondrial targeting peptides and represent carrier proteins of the inner mitochondrial membrane that have internal targeting signals in model eukaryotes. We tested for functional conservation of the dinoflagellate mitochondrial sorting signals by expressing K. micrum mitochondrial proteins in the fungus Saccharomyces cerevisiae. Both the N-terminal and internal targeting signals were sufficiently conserved to operate in this distantly related system. This study indicates that the character of mitochondrial sorting signals was well established prior to the radiation of major eukaryotic lineages and has shown remarkable conservation during long periods of evolution.
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Affiliation(s)
- Jillian C Danne
- School of Botany, University of Melbourne, Victoria 3010, Australia
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Tong J, Dolezal P, Selkrig J, Crawford S, Simpson AGB, Noinaj N, Buchanan SK, Gabriel K, Lithgow T. Ancestral and derived protein import pathways in the mitochondrion of Reclinomonas americana. Mol Biol Evol 2010; 28:1581-91. [PMID: 21081480 DOI: 10.1093/molbev/msq305] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
The evolution of mitochondria from ancestral bacteria required that new protein transport machinery be established. Recent controversy over the evolution of these new molecular machines hinges on the degree to which ancestral bacterial transporters contributed during the establishment of the new protein import pathway. Reclinomonas americana is a unicellular eukaryote with the most gene-rich mitochondrial genome known, and the large collection of membrane proteins encoded on the mitochondrial genome of R. americana includes a bacterial-type SecY protein transporter. Analysis of expressed sequence tags shows R. americana also has components of a mitochondrial protein translocase or "translocase in the inner mitochondrial membrane complex." Along with several other membrane proteins encoded on the mitochondrial genome Cox11, an assembly factor for cytochrome c oxidase retains sequence features suggesting that it is assembled by the SecY complex in R. americana. Despite this, protein import studies show that the RaCox11 protein is suited for import into mitochondria and functional complementation if the gene is transferred into the nucleus of yeast. Reclinomonas americana provides direct evidence that bacterial protein transport pathways were retained, alongside the evolving mitochondrial protein import machinery, shedding new light on the process of mitochondrial evolution.
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Affiliation(s)
- Janette Tong
- Department of Biochemistry & Molecular Biology, Monash University, Clayton, Australia
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Su YC, Hong JR. Betanodavirus B2 causes ATP depletion-induced cell death via mitochondrial targeting and complex II inhibition in vitro and in vivo. J Biol Chem 2010; 285:39801-10. [PMID: 20870718 DOI: 10.1074/jbc.m110.164988] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
The betanodavirus non-structural protein B2 is a newly discovered necrotic death factor with a still unknown role in regulation of mitochondrial function. In the present study, we examined protein B2-mediated inhibition of mitochondrial complex II activity, which results in ATP depletion and thereby in a bioenergetic crisis in vitro and in vivo. Expression of protein B2 was detected early at 24 h postinfection with red-spotted grouper nervous necrosis virus in the cytoplasm. Later B2 was found in mitochondria using enhanced yellow fluorescent protein (EYFP) and immuno-EM analysis. Furthermore, the B2 mitochondrial targeting signal peptide was analyzed by serial deletion and specific point mutation. The sequence of the B2 targeting signal peptide ((41)RTFVISAHAA(50)) was identified and its presence correlated with loss of mitochondrial membrane potential in fish cells. Protein B2 also was found to dramatically inhibit complex II (succinate dehydrogenase) activity, which impairs ATP synthesis in fish GF-1 cells as well as human embryonic kidney 293T cells. Furthermore, when B2 was injected into zebrafish embryos at the one-cell stage to determine its cytotoxicity and ability to inhibit ATP synthesis, we found that B2 caused massive embryonic cell death and depleted ATP resulting in further embryonic death at 10 and 24 h post-fertilization. Taken together, our results indicate that betanodavirus protein B2-induced cell death is due to direct targeting of the mitochondrial matrix by a specific signal peptide that targets mitochondria and inhibits mitochondrial complex II activity thereby reducing ATP synthesis.
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Affiliation(s)
- Yu-Chin Su
- Laboratory of Molecular Virology and Biotechnology, Institute of Biotechnology, National Cheng Kung University, Tainan 701, Taiwan
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Hjort K, Goldberg AV, Tsaousis AD, Hirt RP, Embley TM. Diversity and reductive evolution of mitochondria among microbial eukaryotes. Philos Trans R Soc Lond B Biol Sci 2010; 365:713-27. [PMID: 20124340 DOI: 10.1098/rstb.2009.0224] [Citation(s) in RCA: 137] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
All extant eukaryotes are now considered to possess mitochondria in one form or another. Many parasites or anaerobic protists have highly reduced versions of mitochondria, which have generally lost their genome and the capacity to generate ATP through oxidative phosphorylation. These organelles have been called hydrogenosomes, when they make hydrogen, or remnant mitochondria or mitosomes when their functions were cryptic. More recently, organelles with features blurring the distinction between mitochondria, hydrogenosomes and mitosomes have been identified. These organelles have retained a mitochondrial genome and include the mitochondrial-like organelle of Blastocystis and the hydrogenosome of the anaerobic ciliate Nyctotherus. Studying eukaryotic diversity from the perspective of their mitochondrial variants has yielded important insights into eukaryote molecular cell biology and evolution. These investigations are contributing to understanding the essential functions of mitochondria, defined in the broadest sense, and the limits to which reductive evolution can proceed while maintaining a viable organelle.
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Affiliation(s)
- Karin Hjort
- Institute for Cell and Molecular Biosciences, University of Newcastle, Newcastle upon Tyne NE2 4HH, UK
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25
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Ophir R, Pang X, Halaly T, Venkateswari J, Lavee S, Galbraith D, Or E. Gene-expression profiling of grape bud response to two alternative dormancy-release stimuli expose possible links between impaired mitochondrial activity, hypoxia, ethylene-ABA interplay and cell enlargement. PLANT MOLECULAR BIOLOGY 2009; 71:403-23. [PMID: 19653104 DOI: 10.1007/s11103-009-9531-9] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/19/2009] [Accepted: 07/16/2009] [Indexed: 05/20/2023]
Abstract
A grape-bud-oriented genomic platform was produced for a large-scale comparative analysis of bud responses to two stimuli of grape-bud dormancy release, hydrogen cyanamide (HC) and heat shock (HS). The results suggested considerable similarity in bud response to the stimuli, both in the repertoire of responding genes and in the temporary nature of the transcriptome reprogramming. Nevertheless, the bud response to HC was delayed, more condensed and stronger, as reflected by a higher number of regulated genes and a higher intensity of regulation compared to the response to HS. Integrating the changes occurring in response to both stimuli suggested perturbation of mitochondrial activity, development of oxidative stress and establishment of a situation that resembles hypoxia, which coincides with induction of glycolysis and fermentation, as well as changes in the interplay between ABA and ethylene metabolism. The latter is known to induce various growth responses in submerged plants and the possibility of a similar mechanism operating in the bud meristem during dormancy release is raised. The new link suggested between sub lethal stress, mitochondrial activity, hypoxic conditions, ethylene metabolism and cell enlargement during bud dormancy release may be instrumental in understanding the dormancy-release mechanism. Temporary increase of acetaldehyde, ethanol and ethylene in response to dormancy release stimuli demonstrated the predictive power of the working model, and its relevance to dormancy release was demonstrated by enhancement of bud break by exogenous ethylene and its inhibition by an ethylene signal inhibitor.
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Affiliation(s)
- Ron Ophir
- Department of Fruit Tree Sciences, Institute of Horticulture, Agricultural Research Organization, The Volcani Center, Bet Dagan 50250, Israel
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26
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Mancuso M, Calsolaro V, Orsucci D, Carlesi C, Choub A, Piazza S, Siciliano G. Mitochondria, cognitive impairment, and Alzheimer's disease. Int J Alzheimers Dis 2009; 2009. [PMID: 20798880 PMCID: PMC2925259 DOI: 10.4061/2009/951548] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2009] [Accepted: 06/22/2009] [Indexed: 01/05/2023] Open
Abstract
To date, the beta amyloid (Abeta) cascade hypothesis remains the main pathogenetic model of Alzheimer's disease (AD), but its role in the majority of sporadic AD cases is unclear. The "mitochondrial cascade hypothesis" could explain many of the biochemical, genetic, and pathological features of sporadic AD. Somatic mutations in mitochondrial DNA (mtDNA) could cause energy failure, increased oxidative stress, and accumulation of Abeta, which in a vicious cycle reinforce the mtDNA damage and the oxidative stress. Despite the evidence of mitochondrial dysfunction in AD, no causative mutations in the mtDNA have been detected so far. Indeed, results of studies on the role of mtDNA haplogroups in AD are controversial. In this review we discuss the role of the mitochondria, and especially of the mtDNA, in the cascade of events leading to neurodegeneration, dementia, and AD.
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Affiliation(s)
- M Mancuso
- Department of Neuroscience, Neurological Clinic, University of Pisa, Via Roma 67, 56126 Pisa, Italy
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Yamada Y, Harashima H. Mitochondrial drug delivery systems for macromolecule and their therapeutic application to mitochondrial diseases. Adv Drug Deliv Rev 2008; 60:1439-62. [PMID: 18655816 DOI: 10.1016/j.addr.2008.04.016] [Citation(s) in RCA: 177] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2008] [Accepted: 04/21/2008] [Indexed: 11/30/2022]
Abstract
Mitochondrial dysfunction has been implicated in a variety of human disorders--the so-called mitochondrial diseases. Therefore, the organelle is a promising therapeutic drug target. In this review, we describe the key role of mitochondria in living cells, a number of mitochondrial drug delivery systems and mitochondria-targeted therapeutic strategies. In particular, we discuss mitochondrial delivery of macromolecules, such as proteins and nucleic acids. The discussion of protein delivery is limited primarily to the mitochondrial import machinery. In the section on mitochondrial gene delivery and therapy, we discuss mitochondrial diseases caused by mutations in mitochondrial DNA, several gene delivery strategies and approaches to mitochondrial gene therapy. This review also summarizes our current efforts regarding liposome-based delivery system including use of a multifunctional envelope-type nano-device (MEND) and mitochondrial liposome-based delivery as anti-cancer therapies. Furthermore, we introduce the novel MITO-Porter--a liposome-based mitochondrial delivery system that functions using a membrane-fusion mechanism.
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Affiliation(s)
- Yuma Yamada
- Laboratory for Molecular Design of Pharmaceutics, Faculty of Pharmaceutical Sciences, Hokkaido University, Kita-12, Nishi-6, Kita-ku, Sapporo 060-0812, Japan
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The amyloid beta-peptide is imported into mitochondria via the TOM import machinery and localized to mitochondrial cristae. Proc Natl Acad Sci U S A 2008; 105:13145-50. [PMID: 18757748 DOI: 10.1073/pnas.0806192105] [Citation(s) in RCA: 524] [Impact Index Per Article: 32.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
The amyloid beta-peptide (Abeta) has been suggested to exert its toxicity intracellularly. Mitochondrial functions can be negatively affected by Abeta and accumulation of Abeta has been detected in mitochondria. Because Abeta is not likely to be produced locally in mitochondria, we decided to investigate the mechanisms for mitochondrial Abeta uptake. Our results from rat mitochondria show that Abeta is transported into mitochondria via the translocase of the outer membrane (TOM) machinery. The import was insensitive to valinomycin, indicating that it is independent of the mitochondrial membrane potential. Subfractionation studies following the import experiments revealed Abeta association with the inner membrane fraction, and immunoelectron microscopy after import showed localization of Abeta to mitochondrial cristae. A similar distribution pattern of Abeta in mitochondria was shown by immunoelectron microscopy in human cortical brain biopsies obtained from living subjects with normal pressure hydrocephalus. Thus, we present a unique import mechanism for Abeta in mitochondria and demonstrate both in vitro and in vivo that Abeta is located to the mitochondrial cristae. Importantly, we also show that extracellulary applied Abeta can be internalized by human neuroblastoma cells and can colocalize with mitochondrial markers. Together, these results provide further insight into the mitochondrial uptake of Abeta, a peptide considered to be of major significance in Alzheimer's disease.
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Protein import into hydrogenosomes of Trichomonas vaginalis involves both N-terminal and internal targeting signals: a case study of thioredoxin reductases. EUKARYOTIC CELL 2008; 7:1750-7. [PMID: 18676956 DOI: 10.1128/ec.00206-08] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The parabasalian flagellate Trichomonas vaginalis harbors mitochondrion-related and H(2)-producing organelles of anaerobic ATP synthesis, called hydrogenosomes, which harbor oxygen-sensitive enzymes essential to its pyruvate metabolism. In the human urogenital tract, however, T. vaginalis is regularly exposed to low oxygen concentrations and therefore must possess antioxidant systems protecting the organellar environment against the detrimental effects of molecular oxygen and reactive oxygen species. We have identified two closely related hydrogenosomal thioredoxin reductases (TrxRs), the hitherto-missing component of a thioredoxin-linked hydrogenosomal antioxidant system. One of the two hydrogenosomal TrxR isoforms, TrxRh1, carried an N-terminal extension resembling known hydrogenosomal targeting signals. Expression of hemagglutinin-tagged TrxRh1 in transfected T. vaginalis cells revealed that its N-terminal extension was necessary to import the protein into the organelles. The second hydrogenosomal TrxR isoform, TrxRh2, had no N-terminal targeting signal but was nonetheless efficiently targeted to hydrogenosomes. N-terminal presequences from hydrogenosomal proteins with known processing sites, i.e., the alpha subunit of succinyl coenzyme A synthetase (SCSalpha) and pyruvate:ferredoxin oxidoreductase A, were investigated for their ability to direct mature TrxRh1 to hydrogenosomes. Neither presequence directed TrxRh1 to hydrogenosomes, indicating that neither extension is, by itself, sufficient for hydrogenosomal targeting. Moreover, SCSalpha lacking its N-terminal extension was efficiently imported into hydrogenosomes, indicating that this extension is not required for import of this major hydrogenosomal protein. The finding that some hydrogenosomal enzymes require N-terminal signals for import but that in others the N-terminal extension is not necessary for targeting indicates the presence of additional targeting signals within the mature subunits of several hydrogenosome-localized proteins.
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Chapter 5 New Insights into the Mechanism of Precursor Protein Insertion into the Mitochondrial Membranes. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2008; 268:147-90. [DOI: 10.1016/s1937-6448(08)00805-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/10/2023]
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Yamano K, Yatsukawa YI, Esaki M, Hobbs AEA, Jensen RE, Endo T. Tom20 and Tom22 share the common signal recognition pathway in mitochondrial protein import. J Biol Chem 2007; 283:3799-807. [PMID: 18063580 DOI: 10.1074/jbc.m708339200] [Citation(s) in RCA: 109] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Precise targeting of mitochondrial precursor proteins to mitochondria requires receptor functions of Tom20, Tom22, and Tom70 on the mitochondrial surface. Tom20 is a major import receptor that recognizes preferentially mitochondrial presequences, and Tom70 is a specialized receptor that recognizes presequence-less inner membrane proteins. The cytosolic domain of Tom22 appears to function as a receptor in cooperation with Tom20, but how its substrate specificity differs from that of Tom20 remains unclear. To reveal possible differences in substrate specificities between Tom20 and Tom22, if any, we deleted the receptor domain of Tom20 or Tom22 in mitochondria in vitro by introducing cleavage sites for a tobacco etch virus protease between the receptor domains and transmembrane segments of Tom20 and Tom22. Then mitochondria without the receptor domain of Tom20 or Tom22 were analyzed for their abilities to import various mitochondrial precursor proteins targeted to different mitochondrial subcompartments in vitro. The effects of deletion of the receptor domains on the import of different mitochondrial proteins for different import pathways were quite similar between Tom20 and Tom22. Therefore Tom20 and Tom22 are apparently involved in the same step or sequential steps along the same pathway of targeting signal recognition in import.
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Affiliation(s)
- Koji Yamano
- Department of Chemistry, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya 464-8602, Japan
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Nebauer R, Schuiki I, Kulterer B, Trajanoski Z, Daum G. The phosphatidylethanolamine level of yeast mitochondria is affected by the mitochondrial components Oxa1p and Yme1p. FEBS J 2007; 274:6180-90. [PMID: 17976194 DOI: 10.1111/j.1742-4658.2007.06138.x] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The majority of phosphatidylethanolamine, an essential component of yeast mitochondria, is synthesized by phosphatidylserine decarboxylase 1 (Psd1p), a component of the inner mitochondrial membrane. Here, we report that deletion of OXA1 encoding an inner mitochondrial membrane protein translocase markedly affects the mitochondrial phosphatidylethanolamine level. In an oxa1Delta mutant, cellular and mitochondrial levels of phosphatidylethanolamine were lowered similar to a mutant with PSD1 deleted, and the rate of phosphatidylethanolamine synthesis by decarboxylation of phosphatidylserine in vivo and in vitro was decreased. This was due to a lower PSD1 transcription rate in the oxa1Delta mutant compared with wild-type and compromised assembly of Psd1p into the inner mitochondrial membrane. Lack of Mba1p, another component involved in the assembly of mitochondrial proteins into the inner mitochondrial membrane, did not affect the amount of phosphatidylethanolamine or the assembly of Psd1p. Deletion of the inner membrane protease Yme1p enhanced Psd1p stability suggesting that Yme1p contributed substantially to the proteolytic turnover of Psd1p in wild-type. In summary, our results demonstrate a link between the mitochondrial protein import machinery, assembly and stability of Psd1p, and phosphatidylethanolamine homeostasis in yeast mitochondria.
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Affiliation(s)
- Ruth Nebauer
- Institute of Biochemistry, Graz University of Technology, Austria
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Smith DG, Gawryluk RM, Spencer DF, Pearlman RE, Siu KM, Gray MW. Exploring the Mitochondrial Proteome of the Ciliate Protozoon Tetrahymena thermophila: Direct Analysis by Tandem Mass Spectrometry. J Mol Biol 2007; 374:837-63. [DOI: 10.1016/j.jmb.2007.09.051] [Citation(s) in RCA: 85] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2007] [Revised: 09/18/2007] [Accepted: 09/19/2007] [Indexed: 11/27/2022]
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Habib SJ, Neupert W, Rapaport D. Analysis and prediction of mitochondrial targeting signals. Methods Cell Biol 2007; 80:761-81. [PMID: 17445721 DOI: 10.1016/s0091-679x(06)80035-x] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Affiliation(s)
- Shukry J Habib
- Institut für Physiologische Chemie, Universität München, D-81377 Munich, Germany
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35
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Sugiyama S, Moritoh S, Furukawa Y, Mizuno T, Lim YM, Tsuda L, Nishida Y. Involvement of the mitochondrial protein translocator component tim50 in growth, cell proliferation and the modulation of respiration in Drosophila. Genetics 2007; 176:927-36. [PMID: 17435247 PMCID: PMC1894619 DOI: 10.1534/genetics.107.072074] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Allelic mutants exhibiting growth defects in Drosophila were isolated. Molecular cloning identified the responsible gene as a budding yeast Tim50 ortholog, and thus it was named tiny tim 50 (ttm50). The weak allele (ttm50(Gp99)) produced small flies due to reduced cell size and number, and growth terminated at the larval stage in the strong alleles (ttm50(IE1) and ttm50(IE2)). Twin-spot analysis showed fewer cells in ttm50(Gp99) clones, whereas ttm50(IE1) clones did not proliferate, suggesting that the gene has an essential cellular function. Tim50 is known to maintain mitochondrial membrane potential (MMP) while facilitating inner-membrane protein transport. We found that tagged Ttm50 also localized to mitochondria and that mitochondrial morphology and MMP were affected in mutants, indicating that mitochondrial dysfunction causes the developmental phenotype. Conversely, ttm50 overexpression increased MMP and apoptosis. Co-expression of p35 suppressed this apoptosis, resulting in cell overproliferation. Interestingly, ttm50 transcription was tissue specific, corresponding to elevated MMP in the larval midgut, which was decreased in the mutant. The correlation of ttm50 expression levels with differences in MMP match its proposed role in mitochondrial permeability barrier maintenance. Thus a mitochondrial protein translocase component can play active roles in regulating metabolic levels, possibly for modulation of physiological function or growth in development.
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Affiliation(s)
- Shin Sugiyama
- Division of Biological Science, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya 464-8602, Japan and Department of Mechanism of Aging, National Institute for Longevity Sciences, Morioka-Cho, Obu City, Aichi 474-8522, Japan
| | - Satoru Moritoh
- Division of Biological Science, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya 464-8602, Japan and Department of Mechanism of Aging, National Institute for Longevity Sciences, Morioka-Cho, Obu City, Aichi 474-8522, Japan
| | - Yoshimi Furukawa
- Division of Biological Science, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya 464-8602, Japan and Department of Mechanism of Aging, National Institute for Longevity Sciences, Morioka-Cho, Obu City, Aichi 474-8522, Japan
| | - Tomohiko Mizuno
- Division of Biological Science, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya 464-8602, Japan and Department of Mechanism of Aging, National Institute for Longevity Sciences, Morioka-Cho, Obu City, Aichi 474-8522, Japan
| | - Young-Mi Lim
- Division of Biological Science, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya 464-8602, Japan and Department of Mechanism of Aging, National Institute for Longevity Sciences, Morioka-Cho, Obu City, Aichi 474-8522, Japan
| | - Leo Tsuda
- Division of Biological Science, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya 464-8602, Japan and Department of Mechanism of Aging, National Institute for Longevity Sciences, Morioka-Cho, Obu City, Aichi 474-8522, Japan
| | - Yasuyoshi Nishida
- Division of Biological Science, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya 464-8602, Japan and Department of Mechanism of Aging, National Institute for Longevity Sciences, Morioka-Cho, Obu City, Aichi 474-8522, Japan
- Corresponding author: Division of Biological Science, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya 464-8602, Japan. E-mail:
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MacKenzie JA, Payne RM. Mitochondrial protein import and human health and disease. Biochim Biophys Acta Mol Basis Dis 2006; 1772:509-23. [PMID: 17300922 PMCID: PMC2702852 DOI: 10.1016/j.bbadis.2006.12.002] [Citation(s) in RCA: 82] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2006] [Revised: 12/06/2006] [Accepted: 12/07/2006] [Indexed: 12/31/2022]
Abstract
The targeting and assembly of nuclear-encoded mitochondrial proteins are essential processes because the energy supply of humans is dependent upon the proper functioning of mitochondria. Defective import of mitochondrial proteins can arise from mutations in the targeting signals within precursor proteins, from mutations that disrupt the proper functioning of the import machinery, or from deficiencies in the chaperones involved in the proper folding and assembly of proteins once they are imported. Defects in these steps of import have been shown to lead to oxidative stress, neurodegenerative diseases, and metabolic disorders. In addition, protein import into mitochondria has been found to be a dynamically regulated process that varies in response to conditions such as oxidative stress, aging, drug treatment, and exercise. This review focuses on how mitochondrial protein import affects human health and disease.
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Affiliation(s)
- James A MacKenzie
- Department of Biological Sciences, 133 Piez Hall, State University of New York at Oswego, Oswego, NY 13126, USA.
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37
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Uboldi AD, Lueder FB, Walsh P, Spurck T, McFadden GI, Curtis J, Likic VA, Perugini MA, Barson M, Lithgow T, Handman E. A mitochondrial protein affects cell morphology, mitochondrial segregation and virulence in Leishmania. Int J Parasitol 2006; 36:1499-514. [PMID: 17011565 DOI: 10.1016/j.ijpara.2006.08.006] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2006] [Revised: 08/21/2006] [Accepted: 08/22/2006] [Indexed: 11/24/2022]
Abstract
The single mitochondrion of kinetoplastids divides in synchrony with the nucleus and plays a crucial role in cell division. However, despite its importance and potential as a drug target, the mechanism of mitochondrial division and segregation and the molecules involved are only partly understood. In our quest to identify novel mitochondrial proteins in Leishmania, we constructed a hidden Markov model from the targeting motifs of known mitochondrial proteins as a tool to search the Leishmania major genome. We show here that one of the 17 proteins of unknown function that we identified, designated mitochondrial protein X (MIX), is an oligomeric protein probably located in the inner membrane and expressed throughout the Leishmania life cycle. The MIX gene appears to be essential. Moreover, even deletion of one allele from L. major led to abnormalities in cell morphology, mitochondrial segregation and, importantly, to loss of virulence. MIX is unique to kinetoplastids but its heterologous expression in Saccharomyces cerevisiae produced defects in mitochondrial morphology. Our data show that a number of mitochondrial proteins are unique to kinetoplastids and some, like MIX, play a central role in mitochondrial segregation and cell division, as well as virulence.
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Abstract
Hereditary spastic paraplegia describes a diverse group of disorders characterized by progressive paraparesis primarily affecting lower limbs. In Troyer syndrome, an autosomal recessive form of hereditary spastic paraplegia, patients have dysarthria, distal amyotrophy, developmental delay and short stature in addition to spastic paraparesis. It is caused by a frameshift mutation (1110delA) in SPG20 leading to premature truncation of spartin, a protein with no known function. The objective of this study was to determine the subcellular localization of spartin and investigate the effect of the 1110delA mutation. We observed cytoplasmic expression of spartin in all transfected cell lines. Using superimposed organelle markers or immunocytochemistry staining, we established that spartin localizes to mitochondria and that this localization is dependent on sequences in the C-terminal region. Mutant spartin containing the 1110delA mutation has lost mitochondrial localization. Immunocytochemistry staining using anti-alpha-tubulin antibody provided evidence for partial co-localization of spartin with microtubules. Analysis of fluorescence resonance energy transfer indicated that sequences in the amino terminal are important in mediating microtubule interaction. This study provides the first evidence of spartin subcellular localization and identifies it as the third mitochondrial protein implicated in hereditary spastic paraplegia. Our results suggest that Troyer syndrome may be due to defective microtubule-mediated trafficking of mitochondria and/or mitochondrial dysfunction.
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Affiliation(s)
- JianPing Lu
- UCD School of Medicine and Medical Science, Conway Institute, University College Dublin, Ireland
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Mukhopadhyay A, Yang CS, Weiner H. Binding of mitochondrial leader sequences to Tom20 assessed using a bacterial two-hybrid system shows that hydrophobic interactions are essential and that some mutated leaders that do not bind Tom20 can still be imported. Protein Sci 2006; 15:2739-48. [PMID: 17088320 PMCID: PMC2242433 DOI: 10.1110/ps.062462006] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
Previous studies pointed to the importance of leucine residues in the binding of mitochondrial leader sequences to Tom20, an outer membrane protein translocator that initially binds the leader during import. A bacteria two-hybrid assay was here employed to determine if this could be an alternative way to investigate the binding of leader to the receptor. Leucine to alanine and arginine to glutamine mutations were made in the leader sequence from rat liver aldehyde dehydrogenase (pALDH). The leucine residues in the C-terminal of pALDH leader were found to be essential for TOM20 binding. The hydrophobic residues of another mitochondrial leader F1beta-ATPase that were important for Tom20 binding were found at the C-terminus of the leader. In contrast, it was the leucines in the N-terminus of the leader of ornithine transcarbamylase that were essential for binding. Modeling the peptides to the structure of Tom20 showed that the hydrophobic residues from the three proteins could all fit into the hydrophobic binding pocket. The mutants of pALDH that did not bind to Tom20 were still imported in vivo in transformed HeLa cells or in vitro into isolated mitochondria. In contrast, the mutant from pOTC was imported less well ( approximately 50%) while the mutant from F1beta-ATPase was not imported to any measurable extent. Binding to Tom20 might not be a prerequisite for import; however, it also is possible that import can occur even if binding to a receptor component is poor, so long as the leader binds tightly to another component of the translocator.
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Affiliation(s)
- Abhijit Mukhopadhyay
- Department of Biochemistry, Purdue University, West Lafayette, Indiana 47907-2063, USA
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40
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Tamura Y, Harada Y, Yamano K, Watanabe K, Ishikawa D, Ohshima C, Nishikawa SI, Yamamoto H, Endo T. Identification of Tam41 maintaining integrity of the TIM23 protein translocator complex in mitochondria. ACTA ACUST UNITED AC 2006; 174:631-7. [PMID: 16943180 PMCID: PMC2064306 DOI: 10.1083/jcb.200603087] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Newly synthesized mitochondrial proteins are imported into mitochondria with the aid of protein translocator complexes in the outer and inner mitochondrial membranes. We report the identification of yeast Tam41, a new member of mitochondrial protein translocator systems. Tam41 is a peripheral inner mitochondrial membrane protein facing the matrix. Disruption of the TAM41 gene led to temperature-sensitive growth of yeast cells and resulted in defects in protein import via the TIM23 translocator complex at elevated temperature both in vivo and in vitro. Although Tam41 is not a constituent of the TIM23 complex, depletion of Tam41 led to a decreased molecular size of the TIM23 complex and partial aggregation of Pam18 and -16. Import of Pam16 into mitochondria without Tam41 was retarded, and the imported Pam16 formed aggregates in vitro. These results suggest that Tam41 facilitates mitochondrial protein import by maintaining the functional integrity of the TIM23 protein translocator complex from the matrix side of the inner membrane.
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Affiliation(s)
- Yasushi Tamura
- Department of Chemistry, Graduate School of Science, Nagoya University, Nagoya 464-8602, Japan
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Davey KM, Parboosingh JS, McLeod DR, Chan A, Casey R, Ferreira P, Snyder FF, Bridge PJ, Bernier FP. Mutation of DNAJC19, a human homologue of yeast inner mitochondrial membrane co-chaperones, causes DCMA syndrome, a novel autosomal recessive Barth syndrome-like condition. J Med Genet 2006; 43:385-93. [PMID: 16055927 PMCID: PMC2564511 DOI: 10.1136/jmg.2005.036657] [Citation(s) in RCA: 168] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
BACKGROUND A novel autosomal recessive condition, dilated cardiomyopathy with ataxia (DCMA) syndrome, has been identified in the Canadian Dariusleut Hutterite population, characterised by early onset dilated cardiomyopathy with conduction defects, non-progressive cerebellar ataxia, testicular dysgenesis, growth failure, and 3-methylglutaconic aciduria. OBJECTIVE To map DCMA syndrome and identify the mutation underlying this condition. METHODS A genome wide scan was undertaken on consanguineous Hutterite families using a homozygosity mapping approach in order to identify the DCMA associated chromosomal region. Mutation analysis was carried out on positional candidate genes in this region by sequencing. Reverse transcriptase polymerase chain reaction and bioinformatics analyses were then used to characterise the mutation and determine its effect on the protein product. RESULTS The association of DCMA syndrome with a 2.2 Mb region of chromosome 3q26.33 was found. A disease associated mutation was identified: IVS3-1 G-->C in the DNAJC19 gene, encoding a DNAJ domain containing protein of previously unknown function (Entrez Gene ID 131118). CONCLUSIONS The DNAJC19 protein was previously localised to the mitochondria in cardiac myocytes, and shares sequence and organisational similarity with proteins from several species including two yeast mitochondrial inner membrane proteins, Mdj2p and Tim14. Tim14 is a component of the yeast inner mitochondrial membrane presequence translocase, suggesting that the unique phenotype of DCMA may be the result of defective mitochondrial protein import. It is only the second human disorder caused by defects in this pathway that has been identified.
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Affiliation(s)
- K M Davey
- Molecular Diagnostic Laboratory, Alberta Children's Hospital, Calgary, Alberta 2T 5C7, Canada
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Lee EW, Lai Y, Zhang H, Unadkat JD. Identification of the mitochondrial targeting signal of the human equilibrative nucleoside transporter 1 (hENT1): implications for interspecies differences in mitochondrial toxicity of fialuridine. J Biol Chem 2006; 281:16700-6. [PMID: 16595656 DOI: 10.1074/jbc.m513825200] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We have previously shown that the human equilibrative nucleoside transporter 1 (hENT1) is expressed and functional in the mitochondrial membrane and that this expression enhances the mitochondrial toxicity of the nucleoside drug, fialuridine (FIAU) (Lai, Y., Tse, C. M., and Unadkat, J. D. (2004) J. Biol. Chem. 279, 4490-4497). Here we report on identification of the mitochondrial targeting sequence of hENT1. Using confocal microscopy and different truncated and point mutants of hENT1-YFP (yellow fluorescent protein) expressed in Madin-Darby canine kidney cells, we identified amino acid residues Pro(71),Glu(72), and Asn(74) (the PEXN motif) of hENT1 as important in mitochondrial targeting of hENT1. Identification of this mitochondrial targeting sequence provides a possible explanation for the dramatic difference in mitochondrial toxicity of FIAU between humans and rodents. Although the mouse ENT1 (mENT1), expressed in Madin-Darby canine kidney cells, can transport FIAU, confocal microscopy showed that mENT1-GFP (green fluorescent protein) was not localized to the mitochondria. Consistent with this observation, mitochondria isolated from mouse livers did not transport FIAU. Sequence alignment of hENT1, mENT1, and rat ENT1 (rENT1) showed that the PEXN motif of hENT1 was substituted with a PAXS motif in both mENT1 and rENT1. Substitution of PAXS in mENT1 with PEXN (to create mENT1-PEXN-GFP) and of PEXN in hENT1 with PAXS (to create hENT1-PAXS-YFP) resulted in partial mitochondrial localization of mENT1-PEXN-GFP and loss of mitochondrial localization of hENT1-PAXS-YFP. This is the first time that the mitochondrial targeting signal of hENT1 has been identified. Our data suggest that the lack of mitochondrial toxicity of FIAU in mice is due to the lack of mENT1 targeting to and expression in the mitochondria.
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Affiliation(s)
- Eun-Woo Lee
- Department of Pharmaceutics, School of Pharmacy, University of Washington, Seattle, WA 98195, USA
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43
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Spinazzola A, Viscomi C, Fernandez-Vizarra E, Carrara F, D'Adamo P, Calvo S, Marsano RM, Donnini C, Weiher H, Strisciuglio P, Parini R, Sarzi E, Chan A, DiMauro S, Rötig A, Gasparini P, Ferrero I, Mootha VK, Tiranti V, Zeviani M. MPV17 encodes an inner mitochondrial membrane protein and is mutated in infantile hepatic mitochondrial DNA depletion. Nat Genet 2006; 38:570-5. [PMID: 16582910 DOI: 10.1038/ng1765] [Citation(s) in RCA: 310] [Impact Index Per Article: 17.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2005] [Accepted: 02/15/2006] [Indexed: 12/22/2022]
Abstract
The mitochondrial (mt) DNA depletion syndromes (MDDS) are genetic disorders characterized by a severe, tissue-specific decrease of mtDNA copy number, leading to organ failure. There are two main clinical presentations: myopathic (OMIM 609560) and hepatocerebral (OMIM 251880). Known mutant genes, including TK2, SUCLA2, DGUOK and POLG, account for only a fraction of MDDS cases. We found a new locus for hepatocerebral MDDS on chromosome 2p21-23 and prioritized the genes on this locus using a new integrative genomics strategy. One of the top-scoring candidates was the human ortholog of the mouse kidney disease gene Mpv17. We found disease-segregating mutations in three families with hepatocerebral MDDS and demonstrated that, contrary to the alleged peroxisomal localization of the MPV17 gene product, MPV17 is a mitochondrial inner membrane protein, and its absence or malfunction causes oxidative phosphorylation (OXPHOS) failure and mtDNA depletion, not only in affected individuals but also in Mpv17-/- mice.
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Affiliation(s)
- Antonella Spinazzola
- Unit of Molecular Neurogenetics, Pierfranco and Luisa Mariani Center for the Study of Children's Mitochondrial Disorders, National Neurological Institute C. Besta, Milan 20126, Italy
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44
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Zara V, Ferramosca A, Papatheodorou P, Palmieri F, Rassow J. Import of rat mitochondrial citrate carrier (CIC) at increasing salt concentrations promotes presequence binding to import receptor Tom20 and inhibits membrane translocation. J Cell Sci 2005; 118:3985-95. [PMID: 16129883 DOI: 10.1242/jcs.02526] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Mitochondria contain a family of related carrier proteins that mediate transport of metabolites across the mitochondrial inner membrane. All members of this family are synthesized in the cytosol. We characterized the interactions of newly synthesized rat citrate carrier (CIC) precursor protein (pCIC) with the components of the mitochondrial protein import machinery. pCIC contains both a positively charged presequence of 13 amino acids and internal targeting sequences. We found that the pCIC presequence does not interfere with the import pathway and merely acts as an internal chaperone in the cytosol. Under conditions of increased ionic strength, the pCIC presequence binds to the import receptor Tom20 and accumulates at the mitochondrial surface, thereby delaying pCIC translocation across the mitochondrial outer membrane. Similarly, the presequence of the bovine phosphate carrier (PiC) precursor protein (pPiC) is arrested at the mitochondrial surface when salt concentrations are elevated. We conclude that presequences can only act as mediators of mitochondrial protein import if they allow rapid release from import receptor sites. Release from receptors sites may be rate-limiting in translocation.
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Affiliation(s)
- Vincenzo Zara
- Dipartimento di Scienze e Tecnologie Biologiche ed Ambientali, Università di Lecce, I-73100 Lecce, Italy.
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45
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Adam AC, Bornhövd C, Prokisch H, Neupert W, Hell K. The Nfs1 interacting protein Isd11 has an essential role in Fe/S cluster biogenesis in mitochondria. EMBO J 2005; 25:174-83. [PMID: 16341090 PMCID: PMC1356348 DOI: 10.1038/sj.emboj.7600905] [Citation(s) in RCA: 181] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2005] [Accepted: 11/15/2005] [Indexed: 11/09/2022] Open
Abstract
Formation of iron/sulfur (Fe/S) clusters, protein translocation and protein folding are essential processes in the mitochondria of Saccharomyces cerevisiae. In a systematic approach to characterize essential proteins involved in these processes, we identified a novel essential protein of the mitochondrial matrix, which is highly conserved from yeast to human and which we termed Isd11. Depletion of Isd11 caused a strong reduction in the levels of the Fe/S proteins aconitase and the Rieske protein, and a massive decrease in the enzymatic activities of aconitase and succinate dehydrogenase. Incorporation of iron into the Fe/S protein Leu1 and formation of the Fe/S cluster containing holoform of the mitochondrial ferredoxin Yah1 were inhibited in the absence of Isd11. This strongly suggests that Isd11 is required for the assembly of Fe/S proteins. We show that Isd11 forms a stable complex with Nfs1, the cysteine desulfurase of the mitochondrial machinery for Fe/S cluster assembly. In the absence of Isd11, Nfs1 is prone to aggregation. We propose that Isd11 acts together with Nfs1 in an early step in the biogenesis of Fe/S proteins.
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Affiliation(s)
- Alexander C Adam
- Institut für Physiologische Chemie, Universität München, München, Germany
| | - Carsten Bornhövd
- Institut für Physiologische Chemie, Universität München, München, Germany
| | - Holger Prokisch
- Institute of Human Genetics, Technical University Munich, GSF National Research Center for Environment and Health, Neuherberg, Germany
| | - Walter Neupert
- Institut für Physiologische Chemie, Universität München, München, Germany
| | - Kai Hell
- Institut für Physiologische Chemie, Universität München, München, Germany
- Institut für Physiologische Chemie, Ludwig-Maximilians-Universität München, Butenandtstrasse 5, 81377 München, Germany. Tel.: +49 89 2180 77100; Fax: +49 89 2180 77093; E-mail:
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46
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Wiedemann N, Urzica E, Guiard B, Müller H, Lohaus C, Meyer HE, Ryan MT, Meisinger C, Mühlenhoff U, Lill R, Pfanner N. Essential role of Isd11 in mitochondrial iron-sulfur cluster synthesis on Isu scaffold proteins. EMBO J 2005; 25:184-95. [PMID: 16341089 PMCID: PMC1356349 DOI: 10.1038/sj.emboj.7600906] [Citation(s) in RCA: 187] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2005] [Accepted: 11/15/2005] [Indexed: 01/16/2023] Open
Abstract
Mitochondria are indispensable for cell viability; however, major mitochondrial functions including citric acid cycle and oxidative phosphorylation are dispensable. Most known essential mitochondrial proteins are involved in preprotein import and assembly, while the only known essential biosynthetic process performed by mitochondria is the biogenesis of iron-sulfur clusters (ISC). The components of the mitochondrial ISC-assembly machinery are derived from the prokaryotic ISC-assembly machinery. We have identified an essential mitochondrial matrix protein, Isd11 (YER048w-a), that is found in eukaryotes only. Isd11 is required for biogenesis of cellular Fe/S proteins and thus is a novel subunit of the mitochondrial ISC-assembly machinery. It forms a complex with the cysteine desulfurase Nfs1 and is required for formation of an Fe/S cluster on the Isu scaffold proteins. We conclude that Isd11 is an indispensable eukaryotic component of the mitochondrial machinery for biogenesis of Fe/S proteins.
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Affiliation(s)
- Nils Wiedemann
- Institut für Biochemie und Molekularbiologie, Universität Freiburg, Freiburg, Germany
| | - Eugen Urzica
- Institut für Zytobiologie und Zytopathologie, Philipps-Universität Marburg, Marburg, Germany
| | - Bernard Guiard
- Centre de Génétique Moléculaire, CNRS, Gif-sur-Yvette, France
| | - Hanne Müller
- Institut für Biochemie und Molekularbiologie, Universität Freiburg, Freiburg, Germany
| | - Christiane Lohaus
- Medizinisches Proteom-Center, Ruhr-Universität Bochum, Bochum, Germany
| | - Helmut E Meyer
- Medizinisches Proteom-Center, Ruhr-Universität Bochum, Bochum, Germany
| | - Michael T Ryan
- Department of Biochemistry, La Trobe University, Melbourne, Australia
| | - Chris Meisinger
- Institut für Biochemie und Molekularbiologie, Universität Freiburg, Freiburg, Germany
| | - Ulrich Mühlenhoff
- Institut für Zytobiologie und Zytopathologie, Philipps-Universität Marburg, Marburg, Germany
| | - Roland Lill
- Institut für Zytobiologie und Zytopathologie, Philipps-Universität Marburg, Marburg, Germany
| | - Nikolaus Pfanner
- Institut für Biochemie und Molekularbiologie, Universität Freiburg, Freiburg, Germany
- Institut für Biochemie und Molekularbiologie, Universität Freiburg, Hermann-Herder-Strasse 7, 79104 Freiburg, Germany. Tel.: +49 761 203 5224; Fax: +49 761 203 5261; E-mail:
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47
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Monné M, Chan KW, Slotboom DJ, Kunji ERS. Functional expression of eukaryotic membrane proteins in Lactococcus lactis. Protein Sci 2005; 14:3048-56. [PMID: 16260761 PMCID: PMC2253241 DOI: 10.1110/ps.051689905] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
The overproduction of eukaryotic membrane proteins is a major impediment in their structural and functional characterization. Here we have used the nisin-inducible expression system of Lactococcus lactis for the overproduction of 11 mitochondrial transport proteins from yeast. They were expressed at high levels in a functional state in the cytoplasmic membrane. The results also show that the level of expression is influenced by the N-terminal regions of the transporters. Expression levels were improved >10-fold either by replacing or truncating these regions or by adding lactococcal signal peptides. The observed expression levels are now compatible with a realistic exploration of crystallization conditions. The lactococcal expression system may be used for the high-throughput functional characterization of eukaryotic membrane proteins and structural genomics.
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Affiliation(s)
- Magnus Monné
- The Medical Research Council, Dunn Human Nutrition Unit, Hills Road, Wellcome Trust/MRC Building, Cambridge CB2 2XY, UK
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48
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Becker L, Bannwarth M, Meisinger C, Hill K, Model K, Krimmer T, Casadio R, Truscott KN, Schulz GE, Pfanner N, Wagner R. Preprotein translocase of the outer mitochondrial membrane: reconstituted Tom40 forms a characteristic TOM pore. J Mol Biol 2005; 353:1011-20. [PMID: 16213519 DOI: 10.1016/j.jmb.2005.09.019] [Citation(s) in RCA: 82] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2005] [Revised: 09/06/2005] [Accepted: 09/07/2005] [Indexed: 11/23/2022]
Abstract
Tom40 is the central pore-forming component of the translocase of the outer mitochondrial membrane (TOM complex). Different views exist about the secondary structure and electrophysiological characteristics of Tom40 from Saccharomyces cerevisiae and Neurospora crassa. We have directly compared expressed and renatured Tom40 from both species and find a high content of beta-structure in circular dichroism measurements in agreement with refined secondary structure predictions. The electrophysiological characterization of renatured Tom40 reveals the same characteristics as the purified TOM complex or mitochondrial outer membrane vesicles, with two exceptions. The total conductance of the TOM complex and outer membrane vesicles is twofold higher than the total conductance of renatured Tom40, consistent with the presence of two TOM pores. TOM complex and outer membrane vesicles possess a strongly enhanced sensitivity to a mitochondrial presequence compared to Tom40 alone, in agreement with the presence of several presequence binding sites in the TOM complex, suggesting a role of the non-channel Tom proteins in regulating channel activity.
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Affiliation(s)
- Lars Becker
- Biophysik, Universität Osnabrück, FB Biologie/Chemie, D-49034 Osnabrück, Germany
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49
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Murcha MW, Millar AH, Whelan J. The N-terminal cleavable extension of plant carrier proteins is responsible for efficient insertion into the inner mitochondrial membrane. J Mol Biol 2005; 351:16-25. [PMID: 15992825 DOI: 10.1016/j.jmb.2005.06.004] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2005] [Revised: 06/01/2005] [Accepted: 06/01/2005] [Indexed: 10/25/2022]
Abstract
A subset of mitochondrial carrier proteins from plants contain a cleavable N-terminal extension. We have used a reconstituted protein import assay system into intermembrane space-depleted mitochondria to study the role of the cleavable extension in the carrier import pathway. Insertion of carrier proteins into the inner membrane can be stimulated by the addition of a soluble intermembrane space fraction isolated from plant mitochondria. Greater stimulation of import of the adenine nucleotide carrier (ANT) and phosphate carrier (Pic), which contain N-terminal cleavable extensions, was observed compared to the import of the oxoglutarate malate carrier (OMT), which does not contain a cleavable extension. Removal of the N-terminal cleavable extension from ANT and Pic resulted in loss of stimulation of insertion into the inner membrane. Conversely, addition of the N-terminal extension from ANT or Pic to OMT resulted in significantly enhanced insertion into the inner membrane. The polytopic inner membrane proteins TIM17 and TIM23 that are imported via the carrier import pathway contain no cleavable extension, displayed high-level stimulation of insertion into the inner membrane by addition of the intermembrane space fraction. Addition of the N-terminal cleavable extension from carrier proteins to TIM23 enhanced insertion of TIM23 into the inner membrane even in the absence of the soluble intermembrane space fraction. Together, these results demonstrate that the cleavable N-terminal extensions present on carrier proteins from plants are required for efficient insertion into the inner mitochondrial membrane, and that they can stimulate insertion of any carrier-like protein into the inner membrane.
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Affiliation(s)
- Monika W Murcha
- ARC Centre of Excellence in Plant Energy Biology, CMS Building M310, The University of Western Australia, Crawley 6009, WA, Australia
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50
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Wojtkowska M, Szczech N, Stobienia O, Jarmuszkiewicz W, Budzinska M, Kmita H. An Inception Report on the TOM Complex of the Amoeba Acanthamoeba castellanii, a Simple Model Protozoan in Mitochondria Studies. J Bioenerg Biomembr 2005; 37:261-8. [PMID: 16167181 DOI: 10.1007/s10863-005-6636-y] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2005] [Accepted: 04/07/2005] [Indexed: 11/24/2022]
Abstract
It is suggested that in the course of the TOM complex evolution at least two lineages have appeared: the animal-fungal and green plant ones. The latter involves also the TOM complexes of algae and protozoans. The amoeba Acanthamoeba castellanii is a free-living non-photosynthetic soil protozoan, whose mitochondria share many bioenergetic properties with mitochondria of plants, animals and fungi. Here, we report that a protein complex, identified electrophysiologically as the A. castellanii TOM complex, contains a homologue of yeast/animal Tom 70. Further, molecular weight of the complex (about 500 kDa) also points to A. castellanii evolutionary relation with fungi and animal. Thus, the data indicates that the TOM complex of A. castellanii is not a typical example of the protozoan TOM complex.
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Affiliation(s)
- Malgorzata Wojtkowska
- Laboratory of Bioenergetics, Institute of Molecular Biology and Biotechnology, Adam Mickiewicz University, Fredry 10, 61-701, Poznan, Poland
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