1
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Crameri JJ, Palmer CS, Stait T, Jackson TD, Lynch M, Sinclair A, Frajman LE, Compton AG, Coman D, Thorburn DR, Frazier AE, Stojanovski D. Reduced Protein Import via TIM23 SORT Drives Disease Pathology in TIMM50-Associated Mitochondrial Disease. Mol Cell Biol 2024:1-19. [PMID: 38828998 DOI: 10.1080/10985549.2024.2353652] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2024] [Accepted: 05/07/2024] [Indexed: 06/05/2024] Open
Abstract
TIMM50 is a core subunit of the TIM23 complex, the mitochondrial inner membrane translocase responsible for the import of pre-sequence-containing precursors into the mitochondrial matrix and inner membrane. Here we describe a mitochondrial disease patient who is homozygous for a novel variant in TIMM50 and establish the first proteomic map of mitochondrial disease associated with TIMM50 dysfunction. We demonstrate that TIMM50 pathogenic variants reduce the levels and activity of endogenous TIM23 complex, which significantly impacts the mitochondrial proteome, resulting in a combined oxidative phosphorylation (OXPHOS) defect and changes to mitochondrial ultrastructure. Using proteomic data sets from TIMM50 patient fibroblasts and a TIMM50 HEK293 cell model of disease, we reveal that laterally released substrates imported via the TIM23SORT complex pathway are most sensitive to loss of TIMM50. Proteins involved in OXPHOS and mitochondrial ultrastructure are enriched in the TIM23SORT substrate pool, providing a biochemical mechanism for the specific defects in TIMM50-associated mitochondrial disease patients. These results highlight the power of using proteomics to elucidate molecular mechanisms of disease and uncovering novel features of fundamental biology, with the implication that human TIMM50 may have a more pronounced role in lateral insertion than previously understood.
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Affiliation(s)
- Jordan J Crameri
- Department of Biochemistry and Pharmacology, The University of Melbourne, Parkville, Victoria, Australia
- The Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Parkville, Victoria, Australia
| | - Catherine S Palmer
- Department of Biochemistry and Pharmacology, The University of Melbourne, Parkville, Victoria, Australia
- The Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Parkville, Victoria, Australia
| | - Tegan Stait
- Murdoch Children's Research Institute, Royal Children's Hospital, Parkville, Victoria, Australia
- Victorian Clinical Genetics Services, Royal Children's Hospital, Parkville, Victoria, Australia
| | - Thomas D Jackson
- Department of Biochemistry and Pharmacology, The University of Melbourne, Parkville, Victoria, Australia
- The Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Parkville, Victoria, Australia
| | - Matthew Lynch
- Neurosciences Department, Queensland Children's Hospital, South Brisbane, Queensland, Australia
- Department of Metabolic Medicine, Queensland Children's Hospital, South Brisbane, Queensland, Australia
- School of Medicine, University of Queensland, St Lucia, Queensland, Australia
| | - Adriane Sinclair
- Neurosciences Department, Queensland Children's Hospital, South Brisbane, Queensland, Australia
| | - Leah E Frajman
- Murdoch Children's Research Institute, Royal Children's Hospital, Parkville, Victoria, Australia
| | - Alison G Compton
- Murdoch Children's Research Institute, Royal Children's Hospital, Parkville, Victoria, Australia
- Victorian Clinical Genetics Services, Royal Children's Hospital, Parkville, Victoria, Australia
- Department of Paediatrics, The University of Melbourne, Parkville, Victoria, Australia
| | - David Coman
- Department of Metabolic Medicine, Queensland Children's Hospital, South Brisbane, Queensland, Australia
- School of Medicine, University of Queensland, St Lucia, Queensland, Australia
| | - David R Thorburn
- Murdoch Children's Research Institute, Royal Children's Hospital, Parkville, Victoria, Australia
- Victorian Clinical Genetics Services, Royal Children's Hospital, Parkville, Victoria, Australia
- Department of Paediatrics, The University of Melbourne, Parkville, Victoria, Australia
| | - Ann E Frazier
- Murdoch Children's Research Institute, Royal Children's Hospital, Parkville, Victoria, Australia
- Department of Paediatrics, The University of Melbourne, Parkville, Victoria, Australia
| | - Diana Stojanovski
- Department of Biochemistry and Pharmacology, The University of Melbourne, Parkville, Victoria, Australia
- The Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Parkville, Victoria, Australia
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2
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Paz E, Jain S, Gottfried I, Staretz-Chacham O, Mahajnah M, Bagchi P, Seyfried NT, Ashery U, Azem A. Biochemical and neurophysiological effects of deficiency of the mitochondrial import protein TIMM50. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.05.20.594480. [PMID: 38826427 PMCID: PMC11142075 DOI: 10.1101/2024.05.20.594480] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2024]
Abstract
TIMM50, an essential TIM23 complex subunit, is suggested to facilitate the import of ∼60% of the mitochondrial proteome. In this study, we characterized a TIMM50 disease causing mutation in human fibroblasts, and noted significant decreases in TIM23 core protein levels (TIMM50, TIMM17A/B, and TIMM23). Strikingly, TIMM50 deficiency had no impact on the steady state levels of most of its substrates, challenging the currently accepted import dogma of the essential general import role of TIM23 and suggesting that fully functioning TIM23 complex is not essential for maintaining the steady state level of the majority of mitochondrial proteins. As TIMM50 mutations have been linked to severe neurological phenotypes, we aimed to characterize TIMM50 defects in manipulated mammalian neurons. TIMM50 knockdown in mouse neurons had a minor effect on the steady state level of most of the mitochondrial proteome, supporting the results observed in patient fibroblasts. Amongst the few affected TIM23 substrates, a decrease in the steady state level of components of the intricate oxidative phosphorylation and mitochondrial ribosome complexes was evident. This led to declined respiration rates in fibroblasts and neurons, reduced cellular ATP levels and defective mitochondrial trafficking in neuronal processes, possibly contributing to the developmental defects observed in patients with TIMM50 disease. Finally, increased electrical activity was observed in TIMM50 deficient mice neuronal cells, which correlated with reduced levels of KCNJ10 and KCNA2 plasma membrane potassium channels, likely underlying the patients' epileptic phenotype.
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3
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Genge MG, Roy Chowdhury S, Dohnálek V, Yunoki K, Hirashima T, Endo T, Doležal P, Mokranjac D. Two domains of Tim50 coordinate translocation of proteins across the two mitochondrial membranes. Life Sci Alliance 2023; 6:e202302122. [PMID: 37748811 PMCID: PMC10520260 DOI: 10.26508/lsa.202302122] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2023] [Revised: 09/13/2023] [Accepted: 09/14/2023] [Indexed: 09/27/2023] Open
Abstract
Hundreds of mitochondrial proteins with N-terminal presequences are translocated across the outer and inner mitochondrial membranes via the TOM and TIM23 complexes, respectively. How translocation of proteins across two mitochondrial membranes is coordinated is largely unknown. Here, we show that the two domains of Tim50 in the intermembrane space, named core and PBD, both have essential roles in this process. Building upon the surprising observation that the two domains of Tim50 can complement each other in trans, we establish that the core domain contains the main presequence-binding site and serves as the main recruitment point to the TIM23 complex. On the other hand, the PBD plays, directly or indirectly, a critical role in cooperation of the TOM and TIM23 complexes and supports the receptor function of Tim50. Thus, the two domains of Tim50 both have essential but distinct roles and together coordinate translocation of proteins across two mitochondrial membranes.
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Affiliation(s)
- Marcel G Genge
- Biocenter-Department of Cell Biology, LMU Munich, Munich, Germany
| | | | - Vít Dohnálek
- Department of Parasitology, Faculty of Science, Charles University, BIOCEV, Vestec, Czech Republic
| | - Kaori Yunoki
- Faculty of Life Sciences and Institute for Protein Dynamics, Kyoto Sangyo University, Kyoto, Japan
| | - Takashi Hirashima
- Faculty of Life Sciences and Institute for Protein Dynamics, Kyoto Sangyo University, Kyoto, Japan
| | - Toshiya Endo
- Faculty of Life Sciences and Institute for Protein Dynamics, Kyoto Sangyo University, Kyoto, Japan
| | - Pavel Doležal
- Department of Parasitology, Faculty of Science, Charles University, BIOCEV, Vestec, Czech Republic
| | - Dejana Mokranjac
- Biocenter-Department of Cell Biology, LMU Munich, Munich, Germany
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4
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Schrott S, Osman C. Two mitochondrial HMG-box proteins, Cim1 and Abf2, antagonistically regulate mtDNA copy number in Saccharomyces cerevisiae. Nucleic Acids Res 2023; 51:11813-11835. [PMID: 37850632 PMCID: PMC10681731 DOI: 10.1093/nar/gkad849] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2023] [Revised: 08/21/2023] [Accepted: 09/24/2023] [Indexed: 10/19/2023] Open
Abstract
The mitochondrial genome, mtDNA, is present in multiple copies in cells and encodes essential subunits of oxidative phosphorylation complexes. mtDNA levels have to change in response to metabolic demands and copy number alterations are implicated in various diseases. The mitochondrial HMG-box proteins Abf2 in yeast and TFAM in mammals are critical for mtDNA maintenance and packaging and have been linked to mtDNA copy number control. Here, we discover the previously unrecognized mitochondrial HMG-box protein Cim1 (copy number influence on mtDNA) in Saccharomyces cerevisiae, which exhibits metabolic state dependent mtDNA association. Surprisingly, in contrast to Abf2's supportive role in mtDNA maintenance, Cim1 negatively regulates mtDNA copy number. Cells lacking Cim1 display increased mtDNA levels and enhanced mitochondrial function, while Cim1 overexpression results in mtDNA loss. Intriguingly, Cim1 deletion alleviates mtDNA maintenance defects associated with loss of Abf2, while defects caused by Cim1 overexpression are mitigated by simultaneous overexpression of Abf2. Moreover, we find that the conserved LON protease Pim1 is essential to maintain low Cim1 levels, thereby preventing its accumulation and concomitant repressive effects on mtDNA. We propose a model in which the protein ratio of antagonistically acting Cim1 and Abf2 determines mtDNA copy number.
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Affiliation(s)
- Simon Schrott
- Faculty of Biology, Ludwig-Maximilians-Universität München, Großhaderner Str. 2, Planegg-Martinsried 82152, Germany
| | - Christof Osman
- Faculty of Biology, Ludwig-Maximilians-Universität München, Großhaderner Str. 2, Planegg-Martinsried 82152, Germany
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5
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Reed AL, Mitchell W, Alexandrescu AT, Alder NN. Interactions of amyloidogenic proteins with mitochondrial protein import machinery in aging-related neurodegenerative diseases. Front Physiol 2023; 14:1263420. [PMID: 38028797 PMCID: PMC10652799 DOI: 10.3389/fphys.2023.1263420] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2023] [Accepted: 10/02/2023] [Indexed: 12/01/2023] Open
Abstract
Most mitochondrial proteins are targeted to the organelle by N-terminal mitochondrial targeting sequences (MTSs, or "presequences") that are recognized by the import machinery and subsequently cleaved to yield the mature protein. MTSs do not have conserved amino acid compositions, but share common physicochemical properties, including the ability to form amphipathic α-helical structures enriched with basic and hydrophobic residues on alternating faces. The lack of strict sequence conservation implies that some polypeptides can be mistargeted to mitochondria, especially under cellular stress. The pathogenic accumulation of proteins within mitochondria is implicated in many aging-related neurodegenerative diseases, including Alzheimer's, Parkinson's, and Huntington's diseases. Mechanistically, these diseases may originate in part from mitochondrial interactions with amyloid-β precursor protein (APP) or its cleavage product amyloid-β (Aβ), α-synuclein (α-syn), and mutant forms of huntingtin (mHtt), respectively, that are mediated in part through their associations with the mitochondrial protein import machinery. Emerging evidence suggests that these amyloidogenic proteins may present cryptic targeting signals that act as MTS mimetics and can be recognized by mitochondrial import receptors and transported into different mitochondrial compartments. Accumulation of these mistargeted proteins could overwhelm the import machinery and its associated quality control mechanisms, thereby contributing to neurological disease progression. Alternatively, the uptake of amyloidogenic proteins into mitochondria may be part of a protein quality control mechanism for clearance of cytotoxic proteins. Here we review the pathomechanisms of these diseases as they relate to mitochondrial protein import and effects on mitochondrial function, what features of APP/Aβ, α-syn and mHtt make them suitable substrates for the import machinery, and how this information can be leveraged for the development of therapeutic interventions.
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Affiliation(s)
- Ashley L. Reed
- Department of Molecular and Cell Biology, University of Connecticut, Storrs, CT, United States
| | - Wayne Mitchell
- Department of Medicine, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA, United States
| | - Andrei T. Alexandrescu
- Department of Molecular and Cell Biology, University of Connecticut, Storrs, CT, United States
| | - Nathan N. Alder
- Department of Molecular and Cell Biology, University of Connecticut, Storrs, CT, United States
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6
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Makki A, Rehling P. Protein transport along the presequence pathway. Biol Chem 2023; 404:807-812. [PMID: 37155927 DOI: 10.1515/hsz-2023-0133] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2023] [Accepted: 04/25/2023] [Indexed: 05/10/2023]
Abstract
Most mitochondrial proteins are nuclear-encoded and imported by the protein import machinery based on specific targeting signals. The proteins that carry an amino-terminal targeting signal (presequence) are imported via the presequence import pathway that involves the translocases of the outer and inner membranes - TOM and TIM23 complexes. In this article, we discuss how mitochondrial matrix and inner membrane precursor proteins are imported along the presequence pathway in Saccharomyces cerevisiae with a focus on the dynamics of the TIM23 complex, and further update with some of the key findings that advanced the field in the last few years.
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Affiliation(s)
- Abhijith Makki
- 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
- Cluster of Excellence "Multiscale Bioimaging: from Molecular Machines to Networks of Excitable Cells" (MBExC), University of Göttingen, Göttingen, Germany
- Max Planck Institute for Multidisciplinary Sciences, D-37077 Göttingen, Germany
- Fraunhofer Institute for Translational Medicine and Pharmacology ITMP, Translational Neuroinflammation and Automated Microscopy, Göttingen, Germany
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7
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Jain N, Gomkale R, Bernhard O, Rehling P, Cruz-Zaragoza LD. A quantitative fluorescence-based approach to study mitochondrial protein import. EMBO Rep 2023; 24:e55760. [PMID: 36938994 PMCID: PMC10157374 DOI: 10.15252/embr.202255760] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2022] [Revised: 01/22/2023] [Accepted: 02/17/2023] [Indexed: 03/21/2023] Open
Abstract
Mitochondria play central roles in cellular energy production and metabolism. Most proteins required to carry out these functions are synthesized in the cytosol and imported into mitochondria. A growing number of metabolic disorders arising from mitochondrial dysfunction can be traced to errors in mitochondrial protein import. The mechanisms underlying the import of precursor proteins are commonly studied using radioactively labeled precursor proteins imported into purified mitochondria. Here, we establish a fluorescence-based import assay to analyze protein import into mitochondria. We show that fluorescently labeled precursors enable import analysis with similar sensitivity to those using radioactive precursors, yet they provide the advantage of quantifying import with picomole resolution. We adapted the import assay to a 96-well plate format allowing for fast analysis in a screening-compatible format. Moreover, we show that fluorescently labeled precursors can be used to monitor the assembly of the F1 F0 ATP synthase in purified mitochondria. Thus, we provide a sensitive fluorescence-based import assay that enables quantitative and fast import analysis.
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Affiliation(s)
- Naintara Jain
- Department of Cellular Biochemistry, University Medical Center Göttingen, Göttingen, Germany
| | - Ridhima Gomkale
- Department of Cellular Biochemistry, University Medical Center Göttingen, Göttingen, Germany
| | - Olaf Bernhard
- Department of Cellular Biochemistry, University Medical Center Göttingen, Göttingen, Germany
| | - Peter Rehling
- Department of Cellular Biochemistry, University Medical Center Göttingen, Göttingen, Germany.,Cluster of Excellence "Multiscale Bioimaging: from Molecular Machines to Networks of Excitable Cells" (MBExC), University of Göttingen, Göttingen, Germany.,Max Planck Institute for Multidisciplinary Science, Göttingen, Germany
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8
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Sayyed UMH, Mahalakshmi R. Mitochondrial protein translocation machinery: From TOM structural biogenesis to functional regulation. J Biol Chem 2022; 298:101870. [PMID: 35346689 PMCID: PMC9052162 DOI: 10.1016/j.jbc.2022.101870] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2021] [Revised: 03/13/2022] [Accepted: 03/14/2022] [Indexed: 01/15/2023] Open
Abstract
The human mitochondrial outer membrane is biophysically unique as it is the only membrane possessing transmembrane β-barrel proteins (mitochondrial outer membrane proteins, mOMPs) in the cell. The most vital of the three mOMPs is the core protein of the translocase of the outer mitochondrial membrane (TOM) complex. Identified first as MOM38 in Neurospora in 1990, the structure of Tom40, the core 19-stranded β-barrel translocation channel, was solved in 2017, after nearly three decades. Remarkably, the past four years have witnessed an exponential increase in structural and functional studies of yeast and human TOM complexes. In addition to being conserved across all eukaryotes, the TOM complex is the sole ATP-independent import machinery for nearly all of the ∼1000 to 1500 known mitochondrial proteins. Recent cryo-EM structures have provided detailed insight into both possible assembly mechanisms of the TOM core complex and organizational dynamics of the import machinery and now reveal novel regulatory interplay with other mOMPs. Functional characterization of the TOM complex using biochemical and structural approaches has also revealed mechanisms for substrate recognition and at least five defined import pathways for precursor proteins. In this review, we discuss the discovery, recently solved structures, molecular function, and regulation of the TOM complex and its constituents, along with the implications these advances have for alleviating human diseases.
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Affiliation(s)
- Ulfat Mohd Hanif Sayyed
- Molecular Biophysics Laboratory, Indian Institute of Science Education and Research, Bhopal, India
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9
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Genge MG, Mokranjac D. Coordinated Translocation of Presequence-Containing Precursor Proteins Across Two Mitochondrial Membranes: Knowns and Unknowns of How TOM and TIM23 Complexes Cooperate With Each Other. Front Physiol 2022; 12:806426. [PMID: 35069261 PMCID: PMC8770809 DOI: 10.3389/fphys.2021.806426] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2021] [Accepted: 12/03/2021] [Indexed: 11/23/2022] Open
Abstract
The vast majority of mitochondrial proteins are encoded in the nuclear genome and synthesized on cytosolic ribosomes as precursor proteins with specific mitochondrial targeting signals. Mitochondrial targeting signals are very diverse, however, about 70% of mitochondrial proteins carry cleavable, N-terminal extensions called presequences. These amphipathic helices with one positively charged and one hydrophobic surface target proteins to the mitochondrial matrix with the help of the TOM and TIM23 complexes in the outer and inner membranes, respectively. Translocation of proteins across the two mitochondrial membranes does not take place independently of each other. Rather, in the intermembrane space, where the two complexes meet, components of the TOM and TIM23 complexes form an intricate network of protein-protein interactions that mediates initially transfer of presequences and then of the entire precursor proteins from the outer to the inner mitochondrial membrane. In this Mini Review, we summarize our current understanding of how the TOM and TIM23 complexes cooperate with each other and highlight some of the future challenges and unresolved questions in the field.
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Affiliation(s)
| | - Dejana Mokranjac
- Biozentrum — Department of Cell Biology, LMU Munich, Munich, Germany
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10
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Araiso Y, Endo T. Structural overview of the translocase of the mitochondrial outer membrane complex. Biophys Physicobiol 2022; 19:e190022. [PMID: 35859989 PMCID: PMC9260164 DOI: 10.2142/biophysico.bppb-v19.0022] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2022] [Accepted: 06/03/2022] [Indexed: 12/01/2022] Open
Abstract
Most mitochondrial proteins are synthesized as precursor proteins (preproteins) in the cytosol and imported into mitochondria. The translocator of the outer membrane (TOM) complex functions as a main entry gate for the import of mitochondrial proteins. The TOM complex is a multi-subunit membrane protein complex composed of a β-barrel channel Tom40 and six single-pass membrane proteins. Recent cryo-EM studies have revealed high-resolution structures of the yeast and human TOM complexes, which enabled us to discuss the mechanism of protein import at an amino-acid residue level. The cryo-EM structures show that two Tom40 β-barrels are surrounded by two sets of small Tom subunits to form a dimeric structure. The intermembrane space (IMS) domains of Tom40, Tom22, and Tom7 form a binding site for presequence-containing preproteins in the middle of the dimer to achieve their efficient transfer of to the downstream translocase, the TIM23 complex. The N-terminal segment of Tom40 spans the channel from the cytosol to the IMS to interact with Tom5 at the periphery of the dimer, where downstream components of presequence-lacking preproteins are recruited. Structure-based biochemical analyses together with crosslinking experiments revealed that each Tom40 channel possesses two distinct paths and exit sites for protein translocation of different sets of mitochondrial preproteins. Here we summarize the current knowledge on the structural features, protein translocation mechanisms, and remaining questions for the TOM complexes, with particular emphasis on their determined cryo-EM structures. This article is an extended version of the Japanese article, Structural basis for protein translocation by the translocase of the outer mitochondrial membrane, published in SEIBUTSU BUTSURI Vol. 60, p. 280-283 (2020).
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Affiliation(s)
- Yuhei Araiso
- Department of Clinical Laboratory Science, Graduate School of Medical Science, Kanazawa University
| | - Toshiya Endo
- Faculty of Life Sciences, Kyoto Sangyo University
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11
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Usey MM, Huet D. Parasite powerhouse: A review of the Toxoplasma gondii mitochondrion. J Eukaryot Microbiol 2022; 69:e12906. [PMID: 35315174 PMCID: PMC9490983 DOI: 10.1111/jeu.12906] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Toxoplasma gondii is a member of the apicomplexan phylum, a group of single-celled eukaryotic parasites that cause significant human morbidity and mortality around the world. T. gondii harbors two organelles of endosymbiotic origin: a non-photosynthetic plastid, known as the apicoplast, and a single mitochondrion derived from the ancient engulfment of an α-proteobacterium. Due to excitement surrounding the novelty of the apicoplast, the T. gondii mitochondrion was, to a certain extent, overlooked for about two decades. However, recent work has illustrated that the mitochondrion is an essential hub of apicomplexan-specific biology. Development of novel techniques, such as cryo-electron microscopy, complexome profiling, and next-generation sequencing have led to a renaissance in mitochondrial studies. This review will cover what is currently known about key features of the T. gondii mitochondrion, ranging from its genome to protein import machinery and biochemical pathways. Particular focus will be given to mitochondrial features that diverge significantly from the mammalian host, along with discussion of this important organelle as a drug target.
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Affiliation(s)
- Madelaine M. Usey
- Department of Cellular BiologyUniversity of GeorgiaAthensGeorgiaUSA,Center for Tropical and Emerging Global DiseasesUniversity of GeorgiaAthensGeorgiaUSA
| | - Diego Huet
- Center for Tropical and Emerging Global DiseasesUniversity of GeorgiaAthensGeorgiaUSA,Department of Pharmaceutical and Biomedical SciencesUniversity of GeorgiaAthensGeorgiaUSA
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12
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Guerrero-Castillo S, van Strien J, Brandt U, Arnold S. Ablation of mitochondrial DNA results in widespread remodeling of the mitochondrial complexome. EMBO J 2021; 40:e108648. [PMID: 34542926 PMCID: PMC8561636 DOI: 10.15252/embj.2021108648] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2021] [Revised: 08/26/2021] [Accepted: 09/01/2021] [Indexed: 11/16/2022] Open
Abstract
So‐called ρ0 cells lack mitochondrial DNA and are therefore incapable of aerobic ATP synthesis. How cells adapt to survive ablation of oxidative phosphorylation remains poorly understood. Complexome profiling analysis of ρ0 cells covered 1,002 mitochondrial proteins and revealed changes in abundance and organization of numerous multiprotein complexes including previously not described assemblies. Beyond multiple subassemblies of complexes that would normally contain components encoded by mitochondrial DNA, we observed widespread reorganization of the complexome. This included distinct changes in the expression pattern of adenine nucleotide carrier isoforms, other mitochondrial transporters, and components of the protein import machinery. Remarkably, ablation of mitochondrial DNA hardly affected the complexes organizing cristae junctions indicating that the altered cristae morphology in ρ0 mitochondria predominantly resulted from the loss of complex V dimers required to impose narrow curvatures to the inner membrane. Our data provide a comprehensive resource for in‐depth analysis of remodeling of the mitochondrial complexome in response to respiratory deficiency.
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Affiliation(s)
- Sergio Guerrero-Castillo
- Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, The Netherlands.,University Children's Research@Kinder-UKE, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Joeri van Strien
- Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, The Netherlands.,Center for Molecular and Biomolecular Informatics, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Ulrich Brandt
- Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, The Netherlands.,Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Cologne, Germany
| | - Susanne Arnold
- Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, The Netherlands.,Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Cologne, Germany
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13
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Multiple variants of the human presequence translocase motor subunit Magmas govern the mitochondrial import. J Biol Chem 2021; 297:101349. [PMID: 34715125 PMCID: PMC8605242 DOI: 10.1016/j.jbc.2021.101349] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2021] [Revised: 10/16/2021] [Accepted: 10/22/2021] [Indexed: 11/22/2022] Open
Abstract
Mitochondrial protein translocation is an intricately regulated process that requires dedicated translocases at the outer and inner membranes. The presequence translocase complex, translocase of the inner membrane 23, facilitates most of the import of preproteins containing presequences into the mitochondria, and its primary structural organization is highly conserved. As part of the translocase motor, two J-proteins, DnaJC15 and DnaJC19, are recruited to form two independent translocation machineries (translocase A and translocase B, respectively). On the other hand, the J-like protein subunit of translocase of the inner membrane 23, Mitochondria-associated granulocyte-macrophage colony-stimulating factor signaling molecule (Magmas) (orthologous to the yeast subunit Pam16), can regulate human import-motor activity by forming a heterodimer with DnaJC19 and DnaJC15. However, the precise coordinated regulation of two human import motors by a single Magmas protein is poorly understood. Here, we report two additional Magmas variants (Magmas-1 and Magmas-2) constitutively expressed in the mammalian system. Both the Magmas variants are functional orthologs of Pam16 with an evolutionarily conserved J-like domain critical for cell survival. Moreover, the Magmas variants are peripherally associated with the inner membrane as part of the human import motor for translocation. Our results demonstrate that Magmas-1 is predominantly recruited to translocase B, whereas Magmas-2 is majorly associated with translocase A. Strikingly, both the variants exhibit differential J-protein inhibitory activity in modulating import motor, thereby regulating overall translocase function. Based on our findings, we hypothesize that additional Magmas variants are of evolutionary significance in humans to maximize protein import in familial-linked pathological conditions.
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14
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Trypanosoma brucei Tim50 Possesses PAP Activity and Plays a Critical Role in Cell Cycle Regulation and Parasite Infectivity. mBio 2021; 12:e0159221. [PMID: 34517757 PMCID: PMC8546626 DOI: 10.1128/mbio.01592-21] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Trypanosoma brucei, the infective agent for African trypanosomiasis, possesses a homologue of the translocase of the mitochondrial inner membrane 50 (TbTim50). It has a pair of characteristic phosphatase signature motifs, DXDX(T/V). Here, we demonstrated that, besides its protein phosphatase activity, the recombinant TbTim50 binds and hydrolyzes phosphatidic acid in a concentration-dependent manner. Mutations of D242 and D244, but not of D345and D347, to alanine abolished these activities. In silico structural homology models identified the putative binding interfaces that may accommodate different phosphosubstrates. Interestingly, TbTim50 depletion in the bloodstream form (BF) of T. brucei reduced cardiolipin (CL) levels and decreased mitochondrial membrane potential (ΔΨ). TbTim50 knockdown (KD) also reduced the population of G2/M phase and increased that of G1 phase cells; inhibited segregation and caused overreplication of kinetoplast DNA (kDNA), and reduced BF cell growth. Depletion of TbTim50 increased the levels of AMPK phosphorylation, and parasite morphology was changed with upregulation of expression of a few stumpy marker genes. Importantly, we observed that TbTim50-depleted parasites were unable to establish infection in mice. Proteomics analysis showed reductions in levels of the translation factors, flagellar transport proteins, and many proteasomal subunits, including those of the mitochondrial heat shock locus ATPase (HslVU), which is known to play a role in regulation of kinetoplast DNA (kDNA) replication. Reduction of the level of HslV in TbTim50 KD cells was further validated by immunoblot analysis. Together, our results showed that TbTim50 is essential for mitochondrial function, regulation of kDNA replication, and the cell cycle in the BF. Therefore, TbTim50 is an important target for structure-based drug design to combat African trypanosomiasis.
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Chaudhuri M, Tripathi A, Gonzalez FS. Diverse Functions of Tim50, a Component of the Mitochondrial Inner Membrane Protein Translocase. Int J Mol Sci 2021; 22:7779. [PMID: 34360547 PMCID: PMC8346121 DOI: 10.3390/ijms22157779] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2021] [Revised: 07/14/2021] [Accepted: 07/16/2021] [Indexed: 12/17/2022] Open
Abstract
Mitochondria are essential in eukaryotes. Besides producing 80% of total cellular ATP, mitochondria are involved in various cellular functions such as apoptosis, inflammation, innate immunity, stress tolerance, and Ca2+ homeostasis. Mitochondria are also the site for many critical metabolic pathways and are integrated into the signaling network to maintain cellular homeostasis under stress. Mitochondria require hundreds of proteins to perform all these functions. Since the mitochondrial genome only encodes a handful of proteins, most mitochondrial proteins are imported from the cytosol via receptor/translocase complexes on the mitochondrial outer and inner membranes known as TOMs and TIMs. Many of the subunits of these protein complexes are essential for cell survival in model yeast and other unicellular eukaryotes. Defects in the mitochondrial import machineries are also associated with various metabolic, developmental, and neurodegenerative disorders in multicellular organisms. In addition to their canonical functions, these protein translocases also help maintain mitochondrial structure and dynamics, lipid metabolism, and stress response. This review focuses on the role of Tim50, the receptor component of one of the TIM complexes, in different cellular functions, with an emphasis on the Tim50 homologue in parasitic protozoan Trypanosoma brucei.
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Affiliation(s)
- Minu Chaudhuri
- Department of Microbiology, Immunology, and Physiology, Meharry Medical College, Nashville, TN 37208, USA; (A.T.); (F.S.G.)
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16
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Callegari S, Cruz-Zaragoza LD, Rehling P. From TOM to the TIM23 complex - handing over of a precursor. Biol Chem 2021; 401:709-721. [PMID: 32074073 DOI: 10.1515/hsz-2020-0101] [Citation(s) in RCA: 30] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2020] [Accepted: 02/13/2020] [Indexed: 12/31/2022]
Abstract
Mitochondrial precursor proteins with amino-terminal presequences are imported via the presequence pathway, utilizing the TIM23 complex for inner membrane translocation. Initially, the precursors pass the outer membrane through the TOM complex and are handed over to the TIM23 complex where they are sorted into the inner membrane or translocated into the matrix. This handover process depends on the receptor proteins at the inner membrane, Tim50 and Tim23, which are critical for efficient import. In this review, we summarize key findings that shaped the current concepts of protein translocation along the presequence import pathway, with a particular focus on the precursor handover process from TOM to the TIM23 complex. In addition, we discuss functions of the human TIM23 pathway and the recently uncovered pathogenic mutations in TIM50.
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Affiliation(s)
- Sylvie Callegari
- Department of Cellular Biochemistry, University Medical Center Göttingen, D-37073 Göttingen, Germany
| | - Luis Daniel Cruz-Zaragoza
- 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.,Max Planck Institute for Biophysical Chemistry, D-37077 Göttingen, Germany
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17
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Farouk SM, Abdellatif AM, Metwally E. Outer and inner mitochondrial membrane proteins TOMM40 and TIMM50 are intensively concentrated and localized at Purkinje and pyramidal neurons in the New Zealand white rabbit brain. Anat Rec (Hoboken) 2021; 305:209-221. [PMID: 34041863 DOI: 10.1002/ar.24689] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2020] [Revised: 03/25/2021] [Accepted: 04/06/2021] [Indexed: 11/05/2022]
Abstract
Mitochondria are involved in a variety of developmental processes and neurodegenerative diseases. The translocase complexes of the outer and inner mitochondrial membranes (TOM and TIM) are protein complexes involved in transporting protein precursors across mitochondrial membranes. Although rabbits are important animal models for neurodegenerative diseases, the expression of TOM and TIM complexes has yet to be examined in the rabbit brain. In the present study, we quantitatively evaluated the protein expression of the translocase of outer mitochondrial membrane 40 (TOMM40) and inner mitochondrial membrane 50 (TIMM50) complexes, two of the TOM/TIM complexes, in the cerebral, cerebellar, and hippocampal cortices of the New Zealand white rabbit brain, using immunohistochemistry. Sections from brain specimens were initially stained for cytochrome c oxidase (COX), a well-known mitochondrial marker, which was found to be homogeneously expressed in the cerebrum, but localized to the Purkinje and pyramidal neurons of the cerebellum and hippocampus, respectively. TOMM40 and TIMM50 proteins consistently revealed a similar expression pattern, although at different ratios. In the cerebrum, TOMM40 and TIMM50 immunoreactions were homogeneously distributed within the cytoplasm of various neurons. Meanwhile, Purkinje cells in the cerebellum and pyramidal neurons in the hippocampus displayed higher intensities in their cytoplasm. The specific cellular localization of TOMM40 and TIMM50 proteins in various regions of the rabbit brain suggests a distinct function of each protein in these regions. Further analysis will be required to evaluate the molecular functions of these proteins.
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Affiliation(s)
- Sameh M Farouk
- Department of Cytology & Histology, Faculty of Veterinary Medicine, Suez Canal University, Ismailia, Egypt
| | - Ahmed M Abdellatif
- Department of Anatomy and Embryology, Faculty of Veterinary Medicine, Mansoura University, Mansoura, Egypt
| | - Elsayed Metwally
- Department of Cytology & Histology, Faculty of Veterinary Medicine, Suez Canal University, Ismailia, Egypt
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18
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Transmembrane Coordination of Preprotein Recognition and Motor Coupling by the Mitochondrial Presequence Receptor Tim50. Cell Rep 2021; 30:3092-3104.e4. [PMID: 32130909 DOI: 10.1016/j.celrep.2020.02.031] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2019] [Revised: 12/13/2019] [Accepted: 02/07/2020] [Indexed: 01/05/2023] Open
Abstract
Mitochondrial preproteins contain amino-terminal presequences directing them to the presequence translocase of the mitochondrial inner membrane (TIM23 complex). Depending on additional downstream import signals, TIM23 either inserts preproteins into the inner membrane or translocates them into the matrix. Matrix import requires the coupling of the presequence translocase-associated motor (PAM) to TIM23. The molecular mechanisms coordinating preprotein recognition by TIM23 in the intermembrane space (IMS) with PAM activation in the matrix are unknown. Here we show that subsequent to presequence recognition in the IMS, the Tim50 matrix domain facilitates the recruitment of the coupling factor Pam17. Next, the IMS domain of Tim50 promotes PAM recruitment to TIM23. Finally, the Tim50 transmembrane segment stimulates the matrix-directed import-driving force exerted by PAM. We propose that recognition of preprotein segments in the IMS and transfer of signal information across the inner membrane by Tim50 determine import motor activation.
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Chaudhuri M, Darden C, Soto Gonzalez F, Singha UK, Quinones L, Tripathi A. Tim17 Updates: A Comprehensive Review of an Ancient Mitochondrial Protein Translocator. Biomolecules 2020; 10:E1643. [PMID: 33297490 PMCID: PMC7762337 DOI: 10.3390/biom10121643] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2020] [Revised: 12/02/2020] [Accepted: 12/03/2020] [Indexed: 02/06/2023] Open
Abstract
The translocases of the mitochondrial outer and inner membranes, the TOM and TIMs, import hundreds of nucleus-encoded proteins into mitochondria. TOM and TIMs are multi-subunit protein complexes that work in cooperation with other complexes to import proteins in different sub-mitochondrial destinations. The overall architecture of these protein complexes is conserved among yeast/fungi, animals, and plants. Recent studies have revealed unique characteristics of this machinery, particularly in the eukaryotic supergroup Excavata. Despite multiple differences, homologues of Tim17, an essential component of one of the TIM complexes and a member of the Tim17/Tim22/Tim23 family, have been found in all eukaryotes. Here, we review the structure and function of Tim17 and Tim17-containing protein complexes in different eukaryotes, and then compare them to the single homologue of this protein found in Trypanosoma brucei, a unicellular parasitic protozoan.
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Affiliation(s)
- Minu Chaudhuri
- Department of Microbiology, Immunology, and Physiology, Meharry Medical College, 1005 Dr. D.B. Todd, Jr., Blvd, Nashville, TN 37208, USA; (C.D.); (F.S.G.); (U.K.S.); (L.Q.); (A.T.)
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20
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Singh AP, Salvatori R, Aftab W, Kohler A, Carlström A, Forne I, Imhof A, Ott M. Molecular Connectivity of Mitochondrial Gene Expression and OXPHOS Biogenesis. Mol Cell 2020; 79:1051-1065.e10. [PMID: 32877643 DOI: 10.1016/j.molcel.2020.07.024] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2020] [Revised: 07/20/2020] [Accepted: 07/21/2020] [Indexed: 01/05/2023]
Abstract
Mitochondria contain their own gene expression systems, including membrane-bound ribosomes dedicated to synthesizing a few hydrophobic subunits of the oxidative phosphorylation (OXPHOS) complexes. We used a proximity-dependent biotinylation technique, BioID, coupled with mass spectrometry to delineate in baker's yeast a comprehensive network of factors involved in biogenesis of mitochondrial encoded proteins. This mitochondrial gene expression network (MiGENet) encompasses proteins involved in transcription, RNA processing, translation, or protein biogenesis. Our analyses indicate the spatial organization of these processes, thereby revealing basic mechanistic principles and the proteins populating strategically important sites. For example, newly synthesized proteins are directly handed over to ribosomal tunnel exit-bound factors that mediate membrane insertion, co-factor acquisition, or their mounting into OXPHOS complexes in a special early assembly hub. Collectively, the data reveal the connectivity of mitochondrial gene expression, reflecting a unique tailoring of the mitochondrial gene expression system.
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Affiliation(s)
- Abeer Prakash Singh
- Department of Biochemistry and Biophysics, Stockholm University, 10691 Stockholm, Sweden; Department of Medical Biochemistry and Cell Biology, University of Gothenburg, 40530 Gothenburg, Sweden
| | - Roger Salvatori
- Department of Biochemistry and Biophysics, Stockholm University, 10691 Stockholm, Sweden; Department of Medical Biochemistry and Cell Biology, University of Gothenburg, 40530 Gothenburg, Sweden
| | - Wasim Aftab
- BioMedical Center, Faculty of Medicine, Ludwig Maximilians University of Munich, 82152 Planegg-Martinsried, Germany; Graduate School for Quantitative Biosciences (QBM), Ludwig Maximilians University of Munich, 81377 Munich, Germany
| | - Andreas Kohler
- Department of Biochemistry and Biophysics, Stockholm University, 10691 Stockholm, Sweden
| | - Andreas Carlström
- Department of Biochemistry and Biophysics, Stockholm University, 10691 Stockholm, Sweden
| | - Ignasi Forne
- BioMedical Center, Faculty of Medicine, Ludwig Maximilians University of Munich, 82152 Planegg-Martinsried, Germany
| | - Axel Imhof
- BioMedical Center, Faculty of Medicine, Ludwig Maximilians University of Munich, 82152 Planegg-Martinsried, Germany
| | - Martin Ott
- Department of Biochemistry and Biophysics, Stockholm University, 10691 Stockholm, Sweden; Department of Medical Biochemistry and Cell Biology, University of Gothenburg, 40530 Gothenburg, Sweden.
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21
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Cupo RR, Shorter J. Skd3 (human ClpB) is a potent mitochondrial protein disaggregase that is inactivated by 3-methylglutaconic aciduria-linked mutations. eLife 2020; 9:e55279. [PMID: 32573439 PMCID: PMC7343390 DOI: 10.7554/elife.55279] [Citation(s) in RCA: 37] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2020] [Accepted: 06/22/2020] [Indexed: 12/14/2022] Open
Abstract
Cells have evolved specialized protein disaggregases to reverse toxic protein aggregation and restore protein functionality. In nonmetazoan eukaryotes, the AAA+ disaggregase Hsp78 resolubilizes and reactivates proteins in mitochondria. Curiously, metazoa lack Hsp78. Hence, whether metazoan mitochondria reactivate aggregated proteins is unknown. Here, we establish that a mitochondrial AAA+ protein, Skd3 (human ClpB), couples ATP hydrolysis to protein disaggregation and reactivation. The Skd3 ankyrin-repeat domain combines with conserved AAA+ elements to enable stand-alone disaggregase activity. A mitochondrial inner-membrane protease, PARL, removes an autoinhibitory peptide from Skd3 to greatly enhance disaggregase activity. Indeed, PARL-activated Skd3 solubilizes α-synuclein fibrils connected to Parkinson's disease. Human cells lacking Skd3 exhibit reduced solubility of various mitochondrial proteins, including anti-apoptotic Hax1. Importantly, Skd3 variants linked to 3-methylglutaconic aciduria, a severe mitochondrial disorder, display diminished disaggregase activity (but not always reduced ATPase activity), which predicts disease severity. Thus, Skd3 is a potent protein disaggregase critical for human health.
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Affiliation(s)
- Ryan R Cupo
- Department of Biochemistry and Biophysics, Perelman School of Medicine at the University of PennsylvaniaPhiladelphiaUnited States
- Pharmacology Graduate Group, Perelman School of Medicine at the University of PennsylvaniaPhiladelphiaUnited States
| | - James Shorter
- Department of Biochemistry and Biophysics, Perelman School of Medicine at the University of PennsylvaniaPhiladelphiaUnited States
- Pharmacology Graduate Group, Perelman School of Medicine at the University of PennsylvaniaPhiladelphiaUnited States
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22
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Günsel U, Paz E, Gupta R, Mathes I, Azem A, Mokranjac D. InVivo Dissection of the Intrinsically Disordered Receptor Domain of Tim23. J Mol Biol 2020; 432:3326-3337. [PMID: 32277989 DOI: 10.1016/j.jmb.2020.03.031] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2019] [Revised: 03/05/2020] [Accepted: 03/31/2020] [Indexed: 01/11/2023]
Abstract
In the intermembrane space (IMS) of mitochondria, the receptor domain of Tim23 has an essential role during translocation of hundreds of different proteins from the cytosol via the TOM and TIM23 complexes in the outer and inner membranes, respectively. This intrinsically disordered domain, which can even extend into the cytosol, was shown, mostly in vitro, to interact with several subunits of the TOM and TIM23 complexes. To obtain molecular understanding of this organizational hub in the IMS, we dissected the IMS domain of Tim23 in vivo. We show that the interaction surface of Tim23 with Tim50 is larger than previously thought and reveal an unexpected interaction of Tim23 with Pam17 in the IMS, impairment of which influences their interaction in the matrix. Furthermore, mutations of two conserved negatively charged residues of Tim23, close to the inner membrane, prevented dimerization of Tim23. The same mutations increased exposure of Tim23 on the mitochondrial surface, whereas dissipation of membrane potential decreased it. Our results reveal an intricate network of Tim23 interactions in the IMS, whose influence is transduced across two mitochondrial membranes, ensuring efficient translocation of proteins into mitochondria.
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Affiliation(s)
- Umut Günsel
- BMC-Physiological Chemistry, LMU Munich, 82152 Martinsried, Germany
| | - Eyal Paz
- Department of Biochemistry and Molecular Biology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| | - Ruhita Gupta
- BMC-Physiological Chemistry, LMU Munich, 82152 Martinsried, Germany
| | | | - Abdussalam Azem
- Department of Biochemistry and Molecular Biology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| | - Dejana Mokranjac
- BMC-Physiological Chemistry, LMU Munich, 82152 Martinsried, Germany.
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23
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Matta SK, Kumar A, D'Silva P. Mgr2 regulates mitochondrial preprotein import by associating with channel-forming Tim23 subunit. Mol Biol Cell 2020; 31:1112-1123. [PMID: 32186971 PMCID: PMC7353164 DOI: 10.1091/mbc.e19-12-0677] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Mgr2, a newly identified subunit of the TIM23 complex, functions as a gatekeeper of presequence translocase and thereby maintains quality control of inner membrane preproteins sorting. However, precise recruitment of the Mgr2 subunit to the core channel and how it influences the assembly of the TIM23 complex during lateral sorting of preproteins are poorly understood. Present findings provide insights into a direct association of Mgr2 with the channel-forming Tim23 subunit. Furthermore, the mutational analysis uncovers the TM1 region of Mgr2 critically required for association with Tim23 and Tim21. On the other hand, the TM2 region of Mgr2 is involved in bridging respiratory complexes to the TIM23 complex via Tim21. Importantly, both TM regions of Mgr2 are essential for lateral sorting of preprotein into the inner membrane, as well as maintaining mitochondrial morphology. Together, our findings provide mechanistic insights into the role of Mgr2 in regulating the dynamicity of the TIM23 complex assembly required for preprotein import and coupling of respiratory pathways.
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Affiliation(s)
- Srujan Kumar Matta
- Department of Biochemistry, New Biological Sciences Building, Indian Institute of Science, Bangalore-560012, India
| | - Abhishek Kumar
- Department of Biochemistry, New Biological Sciences Building, Indian Institute of Science, Bangalore-560012, India
| | - Patrick D'Silva
- Department of Biochemistry, New Biological Sciences Building, Indian Institute of Science, Bangalore-560012, India
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24
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Guan Z, Wang Y, Wang Y, Liu X, Wang Y, Zhang W, Chi X, Dong Y, Liu X, Shao S, Zhan Q. Long non-coding RNA LOC100133669 promotes cell proliferation in oesophageal squamous cell carcinoma. Cell Prolif 2020; 53:e12750. [PMID: 32130753 PMCID: PMC7162797 DOI: 10.1111/cpr.12750] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2019] [Revised: 10/30/2019] [Accepted: 11/26/2019] [Indexed: 12/30/2022] Open
Abstract
Objectives LOC100133669 is a lncRNA whose function during tumorigenesis remains unclear now. Thus, we aimed to explore its clinical significance and function in oesophageal squamous cell carcinoma (ESCC). Materials and Methods ISH was used to detect LOC100133669 expression in ESCC tissues. The full‐length LOC100133669 was identified by using RACE assay. Subcellular distribution of LOC100133669 was examined by nuclear/cytoplasmic RNA fractionation and qPCR. The role of LOC100133669 in ESCC cell growth was determined by colony formation, MTT and flow cytometry experiments in vitro, as well as xenograft tumour experiment in vivo. RNA pull‐down assay was performed to find LOC100133669‐interacted protein, which was further examined by RIP, IP, Western blot and rescue experiments. Results LOC100133669 was upregulated in ESCC tissues compared with adjacent non‐tumour tissues. High LOC100133669 expression was associated with poor prognosis of patients with ESCC. We defined LOC100133669 to be 831 nt in length and mainly localized in the cytoplasm of ESCC cells. Knockdown of LOC100133669 inhibited ESCC cell proliferation and cell cycle progression, while overexpression of LOC100133669 showed the opposite effects. Furthermore, LOC100133669 could bind to Tim50 and upregulated its protein level through inhibiting ubiquitination. Overexpression of Tim50 in part abolished the LOC100133669 depletion–caused inhibitory effect on ESCC cell proliferation. Conclusions LOC100133669 plays an oncogenic role in ESCC and may serve as a promising diagnostic marker and therapeutic target for ESCC patients.
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Affiliation(s)
- Zhuzhu Guan
- Institute of Cancer Stem Cell, Dalian Medical University, Dalian, China
| | - Yali Wang
- State Key Laboratory of Molecular Oncology, National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
| | - Yu Wang
- Institute of Cancer Stem Cell, Dalian Medical University, Dalian, China
| | - Xiaoxu Liu
- Institute of Cancer Stem Cell, Dalian Medical University, Dalian, China
| | - Yan Wang
- Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education/Beijing), Laboratory of Molecular Oncology, Peking University Cancer Hospital & Institute, Beijing, China
| | - Weimin Zhang
- Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education/Beijing), Laboratory of Molecular Oncology, Peking University Cancer Hospital & Institute, Beijing, China
| | - Xinming Chi
- Liaoning Key Laboratory of Proteomics, Dalian Medical University, Dalian, China
| | - Yan Dong
- College of Stomatology, Dalian Medical University, Dalian, China
| | - Xuefeng Liu
- Institute of Cancer Stem Cell, Dalian Medical University, Dalian, China
| | - Shujuan Shao
- Liaoning Key Laboratory of Proteomics, Dalian Medical University, Dalian, China
| | - Qimin Zhan
- Institute of Cancer Stem Cell, Dalian Medical University, Dalian, China.,Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education/Beijing), Laboratory of Molecular Oncology, Peking University Cancer Hospital & Institute, Beijing, China
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25
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Basch M, Wagner M, Rolland S, Carbonell A, Zeng R, Khosravi S, Schmidt A, Aftab W, Imhof A, Wagener J, Conradt B, Wagener N. Msp1 cooperates with the proteasome for extraction of arrested mitochondrial import intermediates. Mol Biol Cell 2020; 31:753-767. [PMID: 32049577 PMCID: PMC7185958 DOI: 10.1091/mbc.e19-06-0329] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
The mitochondrial AAA ATPase Msp1 is well known for extraction of mislocalized tail-anchored ER proteins from the mitochondrial outer membrane. Here, we analyzed the extraction of precursors blocking the import pore in the outer membrane. We demonstrate strong genetic interactions of Msp1 and the proteasome with components of the TOM complex, the main translocase in the outer membrane. Msp1 and the proteasome both contribute to the removal of arrested precursor proteins that specifically accumulate in these mutants. The proteasome activity is essential for the removal as proteasome inhibitors block extraction. Furthermore, the proteasomal subunit Rpn10 copurified with Msp1. The human Msp1 homologue has been implicated in neurodegenerative diseases, and we show that the lack of the Caenorhabditis elegans Msp1 homologue triggers an import stress response in the worm, which indicates a conserved role in metazoa. In summary, our results suggest a role of Msp1 as an adaptor for the proteasome that drives the extraction of arrested and mislocalized proteins at the mitochondrial outer membrane.
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Affiliation(s)
- Marion Basch
- Zell- und Entwicklungsbiologie, Department Biologie II, Ludwig-Maximilians-Universität München, Planegg-Martinsried 82152, Germany
| | - Mirjam Wagner
- Zell- und Entwicklungsbiologie, Department Biologie II, Ludwig-Maximilians-Universität München, Planegg-Martinsried 82152, Germany
| | - Stéphane Rolland
- Zell- und Entwicklungsbiologie, Department Biologie II, Ludwig-Maximilians-Universität München, Planegg-Martinsried 82152, Germany
| | - Andres Carbonell
- Zell- und Entwicklungsbiologie, Department Biologie II, Ludwig-Maximilians-Universität München, Planegg-Martinsried 82152, Germany
| | - Rachel Zeng
- Max-Planck-Institut für Biochemie, Martinsried 82152, Germany
| | - Siavash Khosravi
- Zellbiologie-Anatomie III, Biomedizinisches Centrum, Ludwig-Maximilians-Universität München, Planegg-Martinsried 82152, Germany
| | - Andreas Schmidt
- Protein Analysis Unit ZfP, Ludwig-Maximilians-Universität München, Planegg-Martinsried 82152, Germany
| | - Wasim Aftab
- Protein Analysis Unit ZfP, Ludwig-Maximilians-Universität München, Planegg-Martinsried 82152, Germany
| | - Axel Imhof
- Protein Analysis Unit ZfP, Ludwig-Maximilians-Universität München, Planegg-Martinsried 82152, Germany
| | - Johannes Wagener
- Institut für Hygiene und Mikrobiologie, Julius-Maximilians-Universität Würzburg, Würzburg 97080, Germany
| | - Barbara Conradt
- Zell- und Entwicklungsbiologie, Department Biologie II, Ludwig-Maximilians-Universität München, Planegg-Martinsried 82152, Germany
| | - Nikola Wagener
- Zell- und Entwicklungsbiologie, Department Biologie II, Ludwig-Maximilians-Universität München, Planegg-Martinsried 82152, Germany.,Max-Planck-Institut für Biochemie, Martinsried 82152, Germany
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26
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Abstract
Mitochondria are essential organelles of eukaryotic cells. They consist of hundreds of different proteins that exhibit crucial activities in respiration, catabolic metabolism and the synthesis of amino acids, lipids, heme and iron-sulfur clusters. With the exception of a handful of hydrophobic mitochondrially encoded membrane proteins, all these proteins are synthesized on cytosolic ribosomes, targeted to receptors on the mitochondrial surface, and transported across or inserted into the outer and inner mitochondrial membrane before they are folded and assembled into their final native structure. This review article provides a comprehensive overview of the mechanisms and components of the mitochondrial protein import systems with a particular focus on recent developments in the field.
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Affiliation(s)
- Katja G Hansen
- Cell Biology, University of Kaiserslautern, Erwin-Schrödinger-Strasse 13, 67663, Kaiserslautern, Germany
| | - Johannes M Herrmann
- Cell Biology, University of Kaiserslautern, Erwin-Schrödinger-Strasse 13, 67663, Kaiserslautern, Germany.
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27
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Structure of the mitochondrial import gate reveals distinct preprotein paths. Nature 2019; 575:395-401. [PMID: 31600774 DOI: 10.1038/s41586-019-1680-7] [Citation(s) in RCA: 134] [Impact Index Per Article: 26.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2019] [Accepted: 09/30/2019] [Indexed: 11/08/2022]
Abstract
The translocase of the outer mitochondrial membrane (TOM) is the main entry gate for proteins1-4. Here we use cryo-electron microscopy to report the structure of the yeast TOM core complex5-9 at 3.8-Å resolution. The structure reveals the high-resolution architecture of the translocator consisting of two Tom40 β-barrel channels and α-helical transmembrane subunits, providing insight into critical features that are conserved in all eukaryotes1-3. Each Tom40 β-barrel is surrounded by small TOM subunits, and tethered by two Tom22 subunits and one phospholipid. The N-terminal extension of Tom40 forms a helix inside the channel; mutational analysis reveals its dual role in early and late steps in the biogenesis of intermembrane-space proteins in cooperation with Tom5. Each Tom40 channel possesses two precursor exit sites. Tom22, Tom40 and Tom7 guide presequence-containing preproteins to the exit in the middle of the dimer, whereas Tom5 and the Tom40 N extension guide preproteins lacking a presequence to the exit at the periphery of the dimer.
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Göke A, Schrott S, Mizrak A, Belyy V, Osman C, Walter P. Mrx6 regulates mitochondrial DNA copy number in Saccharomyces cerevisiae by engaging the evolutionarily conserved Lon protease Pim1. Mol Biol Cell 2019; 31:527-545. [PMID: 31532710 PMCID: PMC7202074 DOI: 10.1091/mbc.e19-08-0470] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Mitochondrial function depends crucially on the maintenance of multiple mitochondrial DNA (mtDNA) copies. Surprisingly, the cellular mechanisms regulating mtDNA copy number remain poorly understood. Through a systematic high-throughput approach in Saccharomyces cerevisiae, we determined mtDNA–to–nuclear DNA ratios in 5148 strains lacking nonessential genes. The screen revealed MRX6, a largely uncharacterized gene, whose deletion resulted in a marked increase in mtDNA levels, while maintaining wild type–like mitochondrial structure and cell size. Quantitative superresolution imaging revealed that deletion of MRX6 alters both the size and the spatial distribution of mtDNA nucleoids. We demonstrate that Mrx6 partially colocalizes with mtDNA within mitochondria and interacts with the conserved Lon protease Pim1 in a complex that also includes Mam33 and the Mrx6-related protein Pet20. Acute depletion of Pim1 phenocopied the high mtDNA levels observed in Δmrx6 cells. No further increase in mtDNA copy number was observed upon depletion of Pim1 in Δmrx6 cells, revealing an epistatic relationship between Pim1 and Mrx6. Human and bacterial Lon proteases regulate DNA replication by degrading replication initiation factors, suggesting a model in which Pim1 acts similarly with the Mrx6 complex, providing a scaffold linking it to mtDNA.
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Affiliation(s)
- Aylin Göke
- Howard Hughes Medical Institute and Department of Biochemistry and Biophysics and
| | - Simon Schrott
- Faculty of Biology, Ludwig-Maximilian-Universität München, 82152 Planegg-Martinsried, Germany
| | - Arda Mizrak
- Department of Physiology, University of California, San Francisco, San Francisco, CA 94143
| | - Vladislav Belyy
- Howard Hughes Medical Institute and Department of Biochemistry and Biophysics and
| | - Christof Osman
- Howard Hughes Medical Institute and Department of Biochemistry and Biophysics and.,Faculty of Biology, Ludwig-Maximilian-Universität München, 82152 Planegg-Martinsried, Germany
| | - Peter Walter
- Howard Hughes Medical Institute and Department of Biochemistry and Biophysics and
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Tripathi A, Singha UK, Paromov V, Hill S, Pratap S, Rose K, Chaudhuri M. The Cross Talk between TbTim50 and PIP39, Two Aspartate-Based Protein Phosphatases, Maintains Cellular Homeostasis in Trypanosoma brucei. mSphere 2019; 4:e00353-19. [PMID: 31391278 PMCID: PMC6686227 DOI: 10.1128/msphere.00353-19] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2019] [Accepted: 07/08/2019] [Indexed: 12/18/2022] Open
Abstract
Trypanosoma brucei, the infectious agent of a deadly disease known as African trypanosomiasis, undergoes various stresses during its digenetic life cycle. We previously showed that downregulation of T. brucei mitochondrial inner membrane protein translocase 50 (TbTim50), an aspartate-based protein phosphatase and a component of the translocase of the mitochondrial inner membrane (TIM), increased the tolerance of procyclic cells to oxidative stress. Using comparative proteomics analysis and further validating the proteomics results by immunoblotting, here we discovered that TbTim50 downregulation caused an approximately 5-fold increase in the levels of PIP39, which is also an aspartate-based protein phosphatase and is primarily localized in glycosomes. A moderate upregulation of a number of glycosomal enzymes was also noticed due to TbTim50 knockdown. We found that the rate of mitochondrial ATP production by oxidative phosphorylation decreased and that substrate-level phosphorylation increased due to depletion of TbTim50. These results were correlated with relative increases in the levels of trypanosome alternative oxidase and hexokinase and a reduced-growth phenotype in low-glucose medium. The levels and activity of the mitochondrial superoxide dismutase and glutaredoxin levels were increased due to TbTim50 knockdown. Furthermore, we show that TbTim50 downregulation increased the cellular AMP/ATP ratio, and as a consequence, phosphorylation of AMP-activated protein kinase (AMPK) was increased. Knocking down both TbTim50 and TbPIP39 reduced PIP39 levels as well as AMPK phosphorylation and reduced T. brucei tolerance to oxidative stress. These results suggest that TbTim50 and PIP39, two protein phosphatases in mitochondria and glycosomes, respectively, cross talk via the AMPK pathway to maintain cellular homeostasis in the procyclic form of T. bruceiIMPORTANCETrypanosoma brucei, the infectious agent of African trypanosomiasis, must adapt to strikingly different host environments during its digenetic life cycle. Developmental regulation of mitochondrial activities is an essential part of these processes. We have shown previously that mitochondrial inner membrane protein translocase 50 in T. brucei (TbTim50) possesses a dually specific phosphatase activity and plays a role in the cellular stress response pathway. Using proteomics analysis, here we have elucidated a novel connection between TbTim50 and a protein phosphatase of the same family, PIP39, which is also a differentiation-related protein localized in glycosomes. We found that these two protein phosphatases cross talk via the AMPK pathway and modulate cellular metabolic activities under stress. Together, our results indicate the importance of a TbTim50 and PIP39 cascade for communication between mitochondria and other cellular parts in regulation of cell homeostasis in T. brucei.
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Affiliation(s)
- Anuj Tripathi
- Department of Microbiology, Immunology, and Physiology, Meharry Medical College, Nashville, Tennessee, USA
| | - Ujjal K Singha
- Department of Microbiology, Immunology, and Physiology, Meharry Medical College, Nashville, Tennessee, USA
| | - Victor Paromov
- Department of Microbiology, Immunology, and Physiology, Meharry Medical College, Nashville, Tennessee, USA
| | - Salisha Hill
- Department of Biochemistry, Vanderbilt University, Nashville, Tennessee, USA
| | - Siddharth Pratap
- Department of Microbiology, Immunology, and Physiology, Meharry Medical College, Nashville, Tennessee, USA
| | - Kristie Rose
- Department of Biochemistry, Vanderbilt University, Nashville, Tennessee, USA
| | - Minu Chaudhuri
- Department of Microbiology, Immunology, and Physiology, Meharry Medical College, Nashville, Tennessee, USA
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Tort F, Ugarteburu O, Texidó L, Gea-Sorlí S, García-Villoria J, Ferrer-Cortès X, Arias Á, Matalonga L, Gort L, Ferrer I, Guitart-Mampel M, Garrabou G, Vaz FM, Pristoupilova A, Rodríguez MIE, Beltran S, Cardellach F, Wanders RJ, Fillat C, García-Silva MT, Ribes A. Mutations in TIMM50 cause severe mitochondrial dysfunction by targeting key aspects of mitochondrial physiology. Hum Mutat 2019; 40:1700-1712. [PMID: 31058414 DOI: 10.1002/humu.23779] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2018] [Revised: 04/26/2019] [Accepted: 04/28/2019] [Indexed: 01/16/2023]
Abstract
3-Methylglutaconic aciduria (3-MGA-uria) syndromes comprise a heterogeneous group of diseases associated with mitochondrial membrane defects. Whole-exome sequencing identified compound heterozygous mutations in TIMM50 (c.[341 G>A];[805 G>A]) in a boy with West syndrome, optic atrophy, neutropenia, cardiomyopathy, Leigh syndrome, and persistent 3-MGA-uria. A comprehensive analysis of the mitochondrial function was performed in fibroblasts of the patient to elucidate the molecular basis of the disease. TIMM50 protein was severely reduced in the patient fibroblasts, regardless of the normal mRNA levels, suggesting that the mutated residues might be important for TIMM50 protein stability. Severe morphological defects and ultrastructural abnormalities with aberrant mitochondrial cristae organization in muscle and fibroblasts were found. The levels of fully assembled OXPHOS complexes and supercomplexes were strongly reduced in fibroblasts from this patient. High-resolution respirometry demonstrated a significant reduction of the maximum respiratory capacity. A TIMM50-deficient HEK293T cell line that we generated using CRISPR/Cas9 mimicked the respiratory defect observed in the patient fibroblasts; notably, this defect was rescued by transfection with a plasmid encoding the TIMM50 wild-type protein. In summary, we demonstrated that TIMM50 deficiency causes a severe mitochondrial dysfunction by targeting key aspects of mitochondrial physiology, such as the maintenance of proper mitochondrial morphology, OXPHOS assembly, and mitochondrial respiratory capacity.
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Affiliation(s)
- Frederic Tort
- Secció d'Errors Congènits del Metabolisme -IBC, Servei de Bioquímica i Genètica Molecular, Hospital Clínic, IDIBAPS, CIBERER, Barcelona, Spain
| | - Olatz Ugarteburu
- Secció d'Errors Congènits del Metabolisme -IBC, Servei de Bioquímica i Genètica Molecular, Hospital Clínic, IDIBAPS, CIBERER, Barcelona, Spain
| | - Laura Texidó
- Secció d'Errors Congènits del Metabolisme -IBC, Servei de Bioquímica i Genètica Molecular, Hospital Clínic, IDIBAPS, CIBERER, Barcelona, Spain
| | - Sabrina Gea-Sorlí
- Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Universitat de Barcelona, Barcelona, Spain
| | - Judit García-Villoria
- Secció d'Errors Congènits del Metabolisme -IBC, Servei de Bioquímica i Genètica Molecular, Hospital Clínic, IDIBAPS, CIBERER, Barcelona, Spain
| | - Xènia Ferrer-Cortès
- Secció d'Errors Congènits del Metabolisme -IBC, Servei de Bioquímica i Genètica Molecular, Hospital Clínic, IDIBAPS, CIBERER, Barcelona, Spain
| | - Ángela Arias
- Secció d'Errors Congènits del Metabolisme -IBC, Servei de Bioquímica i Genètica Molecular, Hospital Clínic, IDIBAPS, CIBERER, Barcelona, Spain
| | - Leslie Matalonga
- Secció d'Errors Congènits del Metabolisme -IBC, Servei de Bioquímica i Genètica Molecular, Hospital Clínic, IDIBAPS, CIBERER, Barcelona, Spain
| | - Laura Gort
- Secció d'Errors Congènits del Metabolisme -IBC, Servei de Bioquímica i Genètica Molecular, Hospital Clínic, IDIBAPS, CIBERER, Barcelona, Spain
| | - Isidre Ferrer
- Department of Pathology and Experimental Therapeutics, University of Barcelona; Bellvitge University Hospital; IDIBELL; Network Biomedical Research Center of Neurodegenerative diseases (CIBERNED), Hospitalet de Llobregat, Barcelona, Spain
| | - Mariona Guitart-Mampel
- Muscle Research and Mitochondrial Function Laboratory, Cellex-IDIBAPS, Faculty of Medicine and Health Science-University of Barcelona, Internal Medicine Service-Hospital Clínic of Barcelona, CIBERER, Barcelona, Spain
| | - Glòria Garrabou
- Muscle Research and Mitochondrial Function Laboratory, Cellex-IDIBAPS, Faculty of Medicine and Health Science-University of Barcelona, Internal Medicine Service-Hospital Clínic of Barcelona, CIBERER, Barcelona, Spain
| | - Frederick M Vaz
- Departments of Clinical Chemistry and Pediatrics, Laboratory Genetic Metabolic Diseases, University of Amsterdam, Amsterdam, The Netherlands
| | - Ana Pristoupilova
- Department of Pediatrics and Adolescent Medicine, Research Unit for Rare Diseases, First Faculty of Medicine, Charles University, Prague, Czech Republic.,Centre for Genomic Regulation (CRG), CNAG-CRG, Barcelona Institute of Science and Technology (BIST), Barcelona, Spain
| | | | - Sergi Beltran
- Centre for Genomic Regulation (CRG), CNAG-CRG, Barcelona Institute of Science and Technology (BIST), Barcelona, Spain.,Universitat Pompeu Fabra (UPF), Barcelona, Spain
| | - Francesc Cardellach
- Muscle Research and Mitochondrial Function Laboratory, Cellex-IDIBAPS, Faculty of Medicine and Health Science-University of Barcelona, Internal Medicine Service-Hospital Clínic of Barcelona, CIBERER, Barcelona, Spain
| | - Ronald Ja Wanders
- Departments of Clinical Chemistry and Pediatrics, Laboratory Genetic Metabolic Diseases, University of Amsterdam, Amsterdam, The Netherlands
| | - Cristina Fillat
- Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Universitat de Barcelona, Barcelona, Spain
| | - María Teresa García-Silva
- Unidad de Enfermedades Mitocondriales- Enfermedades Metabólicas Hereditarias. Servicio de Pediatría. Universitary Hospital 12 de Octubre, U723 CIBERER, Universidad Complutense, Madrid, Spain
| | - Antonia Ribes
- Secció d'Errors Congènits del Metabolisme -IBC, Servei de Bioquímica i Genètica Molecular, Hospital Clínic, IDIBAPS, CIBERER, Barcelona, Spain
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Mitochondrial presequence import: Multiple regulatory knobs fine-tune mitochondrial biogenesis and homeostasis. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2019; 1866:930-944. [PMID: 30802482 DOI: 10.1016/j.bbamcr.2019.02.012] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/12/2019] [Revised: 02/14/2019] [Accepted: 02/19/2019] [Indexed: 12/22/2022]
Abstract
Mitochondria are pivotal organelles for cellular signaling and metabolism, and their dysfunction leads to severe cellular stress. About 60-70% of the mitochondrial proteome consists of preproteins synthesized in the cytosol with an amino-terminal cleavable presequence targeting signal. The TIM23 complex transports presequence signals towards the mitochondrial matrix. Ultimately, the mature protein segments are either transported into the matrix or sorted to the inner membrane. To ensure accurate preprotein import into distinct mitochondrial sub-compartments, the TIM23 machinery adopts specific functional conformations and interacts with different partner complexes. Regulatory subunits modulate the translocase dynamics, tailoring the import reaction to the incoming preprotein. The mitochondrial membrane potential and the ATP generated via oxidative phosphorylation are key energy sources in driving the presequence import pathway. Thus, mitochondrial dysfunctions have rapid repercussions on biogenesis. Cellular mechanisms exploit the presequence import pathway to monitor mitochondrial dysfunctions and mount transcriptional and proteostatic responses to restore functionality.
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32
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A novel variant of the human mitochondrial DnaJ protein, Tid1, associates with a human disease exhibiting developmental delay and polyneuropathy. Eur J Hum Genet 2019; 27:1072-1080. [PMID: 30770860 DOI: 10.1038/s41431-019-0358-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2018] [Revised: 01/15/2019] [Accepted: 01/24/2019] [Indexed: 12/18/2022] Open
Abstract
Here, we describe a single patient from a consanguineous family, who suffers from developmental delay, intellectual disability, hypermetropia, moderate alternating esotropia, unsteady gait, and peripheral polyneuropathy. Brain MRI revealed basal ganglia disease. Exome analysis disclosed a homozygous variant, c.452G>C (p.(Arg151Thr)), in TID1, encoding a mitochondrial J-protein chaperone that is known for its function in assisting the Hsp70 chaperone, mortalin, in mediating the refolding of denatured protein and dissolving protein aggregates. Results from in vitro import assays showed that both wild type and c.452G>C (p.(Arg151Thr)) are efficiently imported into isolated mitochondria. However, the import rate of the c.452G>C (p.(Arg151Thr)) variant was less than that of the wild-type protein. In the second part of this study, we demonstrated, in vitro, that the disaggregation function of the mortalin/Tid1 team is compromised in the TID1 c.452G>C (p.(Arg151Thr)) variant, as its chaperone activity has a level similar to that of the non-functional H→Q HPD domain variant. The results shed light on the essential function played by Tid1 during neuronal development.
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33
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Zhang X, Han S, Zhou H, Cai L, Li J, Liu N, Liu Y, Wang L, Fan C, Li A, Miao Y. TIMM50 promotes tumor progression via ERK signaling and predicts poor prognosis of non-small cell lung cancer patients. Mol Carcinog 2019; 58:767-776. [PMID: 30604908 DOI: 10.1002/mc.22969] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2018] [Revised: 12/15/2018] [Accepted: 12/27/2018] [Indexed: 12/13/2022]
Abstract
TIMM50 (Translocase of the inner mitochondrial membrane 50), also called TIM50, plays an essential role in mitochondrial membrane transportation. The existing literature suggests that TIMM50 may perform as an oncogenetic protein in breast cancer. However, the molecular mechanism, especially in human non-small cell lung cancer (NSCLC), is uncertain to date. In the present study, using immunohistochemistry, we found that TIMM50 expression significantly correlated with larger tumor size (P = 0.049), advanced TNM stage (P = 0.001), positive regional lymph node metastasis (P = 0.007), and poor overall survival (P = 0.001). Proliferation and invasion assay showed that TIMM50 dramatically promoted the ability of proliferation and invasion of NSCLC cells. Subsequent Western blotting results revealed that TIMM50 enhanced the expression of Cyclin D1 and Snail, and inhibited the expression of E-cadherin. Moreover, TIMM50 facilitated the expression of phosphorylated ERK and P90RSK. Incorporation of ERK inhibitor counteracted the upregulating expression of CyclinD1, and Snail, and downregulating expression of E-cadherin expression induced by TIMM50 overexpression. In conclusion, our data indicated that TIMM50 facilitated tumor proliferation and invasion of NSCLC through enhancing phosphorylation of its downstream ERK/P90RSK signaling pathway. We speculated that TIMM50 might be a useful prognosis marker of NSCLC patients.
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Affiliation(s)
- Xiupeng Zhang
- Department of Pathology, College of Basic Medical Science and the First Affiliated Hospital of China Medical University, Shenyang, China
| | - Shuai Han
- Department of Neurosurgery, The First Hospital of China Medical University, Shenyang, China
| | - Haijing Zhou
- Department of Pathology, College of Basic Medical Science and the First Affiliated Hospital of China Medical University, Shenyang, China
| | - Lin Cai
- Department of Pathology, College of Basic Medical Science and the First Affiliated Hospital of China Medical University, Shenyang, China
| | - Jingduo Li
- Department of Pathology, College of Basic Medical Science and the First Affiliated Hospital of China Medical University, Shenyang, China
| | - Nan Liu
- Department of Pathology, College of Basic Medical Science and the First Affiliated Hospital of China Medical University, Shenyang, China
| | - Yang Liu
- Department of Pathology, College of Basic Medical Science and the First Affiliated Hospital of China Medical University, Shenyang, China
| | - Liang Wang
- Department of Pathology, College of Basic Medical Science and the First Affiliated Hospital of China Medical University, Shenyang, China
| | - Chuifeng Fan
- Department of Pathology, College of Basic Medical Science and the First Affiliated Hospital of China Medical University, Shenyang, China
| | - Ailin Li
- Department of Radiotherapy, The First Affiliated Hospital of China Medical University, Shenyang, China
| | - Yuan Miao
- Department of Pathology, College of Basic Medical Science and the First Affiliated Hospital of China Medical University, Shenyang, China
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Bentley SJ, Jamabo M, Boshoff A. The Hsp70/J-protein machinery of the African trypanosome, Trypanosoma brucei. Cell Stress Chaperones 2019; 24:125-148. [PMID: 30506377 PMCID: PMC6363631 DOI: 10.1007/s12192-018-0950-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2018] [Revised: 11/06/2018] [Accepted: 11/12/2018] [Indexed: 12/28/2022] Open
Abstract
The etiological agent of the neglected tropical disease African trypanosomiasis, Trypanosoma brucei, possesses an expanded and diverse repertoire of heat shock proteins, which have been implicated in cytoprotection, differentiation, as well as progression and transmission of the disease. Hsp70 plays a crucial role in proteostasis, and inhibition of its interactions with co-chaperones is emerging as a potential therapeutic target for numerous diseases. In light of genome annotations and the release of the genome sequence of the human infective subspecies, an updated and current in silico overview of the Hsp70/J-protein machinery in both T. brucei brucei and T. brucei gambiense was conducted. Functional, structural, and evolutionary analyses of the T. brucei Hsp70 and J-protein families were performed. The Hsp70 and J-proteins from humans and selected kinetoplastid parasites were used to assist in identifying proteins from T. brucei, as well as the prediction of potential Hsp70-J-protein partnerships. The Hsp70 and J-proteins were mined from numerous genome-wide proteomics studies, which included different lifecycle stages and subcellular localisations. In this study, 12 putative Hsp70 proteins and 67 putative J-proteins were identified to be encoded on the genomes of both T. brucei subspecies. Interestingly there are 6 type III J-proteins that possess tetratricopeptide repeat-containing (TPR) motifs. Overall, it is envisioned that the results of this study will provide a future context for studying the biology of the African trypanosome and evaluating Hsp70 and J-protein interactions as potential drug targets.
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Affiliation(s)
| | - Miebaka Jamabo
- Biotechnology Innovation Centre, Rhodes University, Grahamstown, South Africa
| | - Aileen Boshoff
- Biotechnology Innovation Centre, Rhodes University, Grahamstown, South Africa.
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35
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Richter F, Dennerlein S, Nikolov M, Jans DC, Naumenko N, Aich A, MacVicar T, Linden A, Jakobs S, Urlaub H, Langer T, Rehling P. ROMO1 is a constituent of the human presequence translocase required for YME1L protease import. J Cell Biol 2018; 218:598-614. [PMID: 30598479 PMCID: PMC6363466 DOI: 10.1083/jcb.201806093] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2018] [Revised: 10/18/2018] [Accepted: 11/26/2018] [Indexed: 01/15/2023] Open
Abstract
Mitochondria are the powerhouses of eukaryotic cells and rely on protein import from the cytosol. Richter et al. found ROMO1 as a new constituent of the human mitochondrial import machinery linking protein import to quality control and mitochondrial morphology. The mitochondrial presequence translocation machinery (TIM23 complex) is conserved between the yeast Saccharomyces cerevisiae and humans; however, functional characterization has been mainly performed in yeast. Here, we define the constituents of the human TIM23 complex using mass spectrometry and identified ROMO1 as a new translocase constituent with an exceptionally short half-life. Analyses of a ROMO1 knockout cell line revealed aberrant inner membrane structure and altered processing of the GTPase OPA1. We show that in the absence of ROMO1, mitochondria lose the inner membrane YME1L protease, which participates in OPA1 processing and ROMO1 turnover. While ROMO1 is dispensable for general protein import along the presequence pathway, we show that it participates in the dynamics of TIM21 during respiratory chain biogenesis and is specifically required for import of YME1L. This selective import defect can be linked to charge distribution in the unusually long targeting sequence of YME1L. Our analyses establish an unexpected link between mitochondrial protein import and inner membrane protein quality control.
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Affiliation(s)
- Frank Richter
- Department of Cellular Biochemistry, University Medical Center Göttingen, Göttingen, Germany
| | - Sven Dennerlein
- Department of Cellular Biochemistry, University Medical Center Göttingen, Göttingen, Germany
| | - Miroslav Nikolov
- Bioanalytical Mass Spectrometry Group, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Daniel C Jans
- Department of NanoBiophotonics, Mitochondrial Structure and Dynamics Group, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany.,Department of Neurology, University Medical Center, Göttingen, Germany
| | - Nataliia Naumenko
- Department of Cellular Biochemistry, University Medical Center Göttingen, Göttingen, Germany
| | - Abhishek Aich
- Department of Cellular Biochemistry, University Medical Center Göttingen, Göttingen, Germany
| | - Thomas MacVicar
- Department of Mitochondrial Proteostasis, Max Planck Institute for Biology of Ageing, Cologne, Germany
| | - Andreas Linden
- Bioanalytical Mass Spectrometry Group, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany.,Bioanalytics Group, Department of Clinical Chemistry, University Medical Center Göttingen, Göttingen, Germany
| | - Stefan Jakobs
- Department of NanoBiophotonics, Mitochondrial Structure and Dynamics Group, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany.,Department of Neurology, University Medical Center, Göttingen, Germany
| | - Henning Urlaub
- Bioanalytical Mass Spectrometry Group, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany.,Bioanalytics Group, Department of Clinical Chemistry, University Medical Center Göttingen, Göttingen, Germany
| | - Thomas Langer
- Department of Mitochondrial Proteostasis, Max Planck Institute for Biology of Ageing, Cologne, Germany
| | - Peter Rehling
- Department of Cellular Biochemistry, University Medical Center Göttingen, Göttingen, Germany .,Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
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36
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Mitochondrial diseases caused by dysfunctional mitochondrial protein import. Biochem Soc Trans 2018; 46:1225-1238. [PMID: 30287509 DOI: 10.1042/bst20180239] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2018] [Revised: 08/20/2018] [Accepted: 08/31/2018] [Indexed: 12/18/2022]
Abstract
Mitochondria are essential organelles which perform complex and varied functions within eukaryotic cells. Maintenance of mitochondrial health and functionality is thus a key cellular priority and relies on the organelle's extensive proteome. The mitochondrial proteome is largely encoded by nuclear genes, and mitochondrial proteins must be sorted to the correct mitochondrial sub-compartment post-translationally. This essential process is carried out by multimeric and dynamic translocation and sorting machineries, which can be found in all four mitochondrial compartments. Interestingly, advances in the diagnosis of genetic disease have revealed that mutations in various components of the human import machinery can cause mitochondrial disease, a heterogenous and often severe collection of disorders associated with energy generation defects and a multisystem presentation often affecting the cardiovascular and nervous systems. Here, we review our current understanding of mitochondrial protein import systems in human cells and the molecular basis of mitochondrial diseases caused by defects in these pathways.
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Banerjee R, Günsel U, Mokranjac D. Chemical Crosslinking in Intact Mitochondria. Methods Mol Biol 2018; 1567:139-154. [PMID: 28276017 DOI: 10.1007/978-1-4939-6824-4_9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
Many mitochondrial proteins perform their functions as components of large, multimeric complexes. Chemical crosslinking is a powerful method to analyze protein-protein interactions within such complexes. Using membrane-permeable crosslinkers and isolated intact mitochondria, protein-protein interactions that are secluded by two mitochondrial membranes can be readily analyzed in physiologically active, isolated organelles under a variety of physiological and pathophysiological conditions. Here, we describe two methods for chemical crosslinking in intact yeast mitochondria. The first method enables the analysis of ATP-dependent remodeling of mitochondrial protein complexes while the second one allows the identification of crosslinking partners of a protein of interest.
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Affiliation(s)
- Rupa Banerjee
- Biomedical Center-Physiological Chemistry, LMU Munich, Großhadernerstr. 9, 82152, Martinsried, Germany
| | - Umut Günsel
- Biomedical Center-Physiological Chemistry, LMU Munich, Großhadernerstr. 9, 82152, Martinsried, Germany
| | - Dejana Mokranjac
- Biomedical Center-Physiological Chemistry, LMU Munich, Großhadernerstr. 9, 82152, Martinsried, Germany.
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A single-cysteine mutant and chimeras of essential Leishmania Erv can complement the loss of Erv1 but not of Mia40 in yeast. Redox Biol 2017; 15:363-374. [PMID: 29310075 PMCID: PMC5760468 DOI: 10.1016/j.redox.2017.12.010] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2017] [Revised: 12/17/2017] [Accepted: 12/21/2017] [Indexed: 11/21/2022] Open
Abstract
Mia40/CHCHD4 and Erv1/ALR are essential for oxidative protein folding in the mitochondrial intermembrane space of yeast and mammals. In contrast, many protists, including important apicomplexan and kinetoplastid parasites, lack Mia40. Furthermore, the Erv homolog of the model parasite Leishmania tarentolae (LtErv) was shown to be incompatible with Saccharomyces cerevisiae Mia40 (ScMia40). Here we addressed structure-function relationships of ScErv1 and LtErv as well as their compatibility with the oxidative protein folding system in yeast using chimeric, truncated, and mutant Erv constructs. Chimeras between the N-terminal arm of ScErv1 and a variety of truncated LtErv constructs were able to rescue yeast cells that lack ScErv1. Yeast cells were also viable when only a single cysteine residue was replaced in LtErvC17S. Thus, the presence and position of the C-terminal arm and the kinetoplastida-specific second (KISS) domain of LtErv did not interfere with its functionality in the yeast system, whereas a relatively conserved cysteine residue before the flavodomain rendered LtErv incompatible with ScMia40. The question whether parasite Erv homologs might also exert the function of Mia40 was addressed in another set of complementation assays. However, neither the KISS domain nor other truncated or mutant LtErv constructs were able to rescue yeast cells that lack ScMia40. The general relevance of Erv and its candidate substrate small Tim1 was analyzed for the related parasite L. infantum. Repeated unsuccessful knockout attempts suggest that both genes are essential in this human pathogen and underline the potential of mitochondrial protein import pathways for future intervention strategies.
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39
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Weems E, Singha UK, Smith JT, Chaudhuri M. The divergent N-terminal domain of Tim17 is critical for its assembly in the TIM complex in Trypanosoma brucei. Mol Biochem Parasitol 2017; 218:4-15. [PMID: 28965880 DOI: 10.1016/j.molbiopara.2017.09.003] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2017] [Revised: 09/18/2017] [Accepted: 09/25/2017] [Indexed: 10/18/2022]
Abstract
Trypanosoma brucei Tim17(TbTim17), the single member of the Tim17/23/22 protein family, is an essential component of the translocase of the mitochondrial inner membrane (TIM). In spite of the conserved secondary structure, the primary sequence of TbTim17, particularly the N-terminal hydrophilic region, is significantly divergent. In order to understand the function of this region we expressed two N-terminal deletion mutants (Δ20 and Δ30) of TbTim17 in T. brucei. Both of these mutants of TbTim17 were targeted to mitochondria, however, they failed to complement the growth defect of TbTim17 RNAi cells. In addition, the import defect of other nuclear encoded proteins into TbTim17 knockdown mitochondria were not restored by expression of the N-terminal deletion mutants but complemented by knock-in of the full-length protein. Further analysis revealed that Δ20-TbTim17 and Δ30-TbTim17 mutants were not localized in the mitochondrial inner membrane. Analysis of the protein complexes in the wild type and mutant mitochondria by two-dimensional Blue-native/SDS-PAGE revealed that none of these mutants are assembled into the TbTim17 protein complex. However, FL-TbTim17 was integrated into the mitochondrial inner membrane and assembled into TbTim17 complex. Co-immunoprecipitation analysis showed that unlike the FL-TbTim17, mutant proteins are not associated with the endogenous TbTim17 as well as its interacting partner TbTim62, a novel trypanosome specific Tim. Together, these results show that the N-terminal domain of TbTim17 plays unique and essential roles for its sorting and assembly into the TbTim17 protein complex.
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Affiliation(s)
- Ebony Weems
- Department of Microbiology and Immunology, Meharry Medical College, Nashville, TN, 37209, United States
| | - Ujjal K Singha
- Department of Microbiology and Immunology, Meharry Medical College, Nashville, TN, 37209, United States
| | - Joseph T Smith
- Department of Microbiology and Immunology, Meharry Medical College, Nashville, TN, 37209, United States
| | - Minu Chaudhuri
- Department of Microbiology and Immunology, Meharry Medical College, Nashville, TN, 37209, United States.
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40
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Bentley SJ, Boshoff A. Hsp70/J-protein machinery from Glossina morsitans morsitans, vector of African trypanosomiasis. PLoS One 2017; 12:e0183858. [PMID: 28902917 PMCID: PMC5597180 DOI: 10.1371/journal.pone.0183858] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2017] [Accepted: 08/11/2017] [Indexed: 11/18/2022] Open
Abstract
Tsetse flies (Glossina spp.) are the sole vectors of the protozoan parasites of the genus Trypanosoma, the causative agents of African Trypanosomiasis. Species of Glossina differ in vector competence and Glossina morsitans morsitans is associated with transmission of Trypanosoma brucei rhodesiense, which causes an acute and often fatal form of African Trypanosomiasis. Heat shock proteins are evolutionarily conserved proteins that play critical roles in proteostasis. The activity of heat shock protein 70 (Hsp70) is regulated by interactions with its J-protein (Hsp40) co-chaperones. Inhibition of these interactions are emerging as potential therapeutic targets. The assembly and annotation of the G. m. morsitans genome provided a platform to identify and characterize the Hsp70s and J-proteins, and carry out an evolutionary comparison to its well-studied eukaryotic counterparts, Drosophila melanogaster and Homo sapiens, as well as Stomoxys calcitrans, a comparator species. In our study, we identified 9 putative Hsp70 proteins and 37 putative J-proteins in G. m. morsitans. Phylogenetic analyses revealed three evolutionarily distinct groups of Hsp70s, with a closer relationship to orthologues from its blood-feeding dipteran relative Stomoxys calcitrans. G. m. morsitans also lacked the high number of heat inducible Hsp70s found in D. melanogaster. The potential localisations, functions, domain organisations and Hsp70/J-protein partnerships were also identified. A greater understanding of the heat shock 70 (Hsp70) and J-protein (Hsp40) families in G. m. morsitans could enhance our understanding of the cell biology of the tsetse fly.
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Affiliation(s)
- Stephen J. Bentley
- Biotechnology Innovation Centre, Rhodes University, Grahamstown, South Africa
| | - Aileen Boshoff
- Biotechnology Innovation Centre, Rhodes University, Grahamstown, South Africa
- * E-mail:
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41
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Malhotra K, Modak A, Nangia S, Daman TH, Gunsel U, Robinson VL, Mokranjac D, May ER, Alder NN. Cardiolipin mediates membrane and channel interactions of the mitochondrial TIM23 protein import complex receptor Tim50. SCIENCE ADVANCES 2017; 3:e1700532. [PMID: 28879236 PMCID: PMC5580885 DOI: 10.1126/sciadv.1700532] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/17/2017] [Accepted: 08/04/2017] [Indexed: 05/07/2023]
Abstract
The phospholipid cardiolipin mediates the functional interactions of proteins that reside within energy-conserving biological membranes. However, the molecular basis by which this lipid performs this essential cellular role is not well understood. We address this role of cardiolipin using the multisubunit mitochondrial TIM23 protein transport complex as a model system. The early stages of protein import by this complex require specific interactions between the polypeptide substrate receptor, Tim50, and the membrane-bound channel-forming subunit, Tim23. Using analyses performed in vivo, in isolated mitochondria, and in reductionist nanoscale model membrane systems, we show that the soluble receptor domain of Tim50 interacts with membranes and with specific sites on the Tim23 channel in a manner that is directly modulated by cardiolipin. To obtain structural insights into the nature of these interactions, we obtained the first small-angle x-ray scattering-based structure of the soluble Tim50 receptor in its entirety. Using these structural insights, molecular dynamics simulations combined with a range of biophysical measurements confirmed the role of cardiolipin in driving the association of the Tim50 receptor with lipid bilayers with concomitant structural changes, highlighting the role of key structural elements in mediating this interaction. Together, these results show that cardiolipin is required to mediate specific receptor-channel associations in the TIM23 complex. Our results support a new working model for the dynamic structural changes that occur within the complex during transport. More broadly, this work strongly advances our understanding of how cardiolipin mediates interactions among membrane-associated proteins.
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Affiliation(s)
- Ketan Malhotra
- Department of Molecular and Cell Biology, University of Connecticut, 91 North Eagleville Road, Storrs, CT 06269–3125, USA
| | - Arnab Modak
- Department of Molecular and Cell Biology, University of Connecticut, 91 North Eagleville Road, Storrs, CT 06269–3125, USA
| | - Shivangi Nangia
- Department of Molecular and Cell Biology, University of Connecticut, 91 North Eagleville Road, Storrs, CT 06269–3125, USA
| | - Tyler H. Daman
- Department of Molecular and Cell Biology, University of Connecticut, 91 North Eagleville Road, Storrs, CT 06269–3125, USA
| | - Umut Gunsel
- Department of Physiological Chemistry, Biomedical Center Munich, Ludwig-Maximilian University of Munich, 82152 Planegg-Martinsried, Germany
| | - Victoria L. Robinson
- Department of Molecular and Cell Biology, University of Connecticut, 91 North Eagleville Road, Storrs, CT 06269–3125, USA
| | - Dejana Mokranjac
- Department of Physiological Chemistry, Biomedical Center Munich, Ludwig-Maximilian University of Munich, 82152 Planegg-Martinsried, Germany
| | - Eric R. May
- Department of Molecular and Cell Biology, University of Connecticut, 91 North Eagleville Road, Storrs, CT 06269–3125, USA
| | - Nathan N. Alder
- Department of Molecular and Cell Biology, University of Connecticut, 91 North Eagleville Road, Storrs, CT 06269–3125, USA
- Corresponding author.
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42
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Protein trafficking in the mitochondrial intermembrane space: mechanisms and links to human disease. Biochem J 2017; 474:2533-2545. [PMID: 28701417 PMCID: PMC5509380 DOI: 10.1042/bcj20160627] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2016] [Revised: 05/03/2017] [Accepted: 05/09/2017] [Indexed: 01/20/2023]
Abstract
Mitochondria fulfill a diverse range of functions in cells including oxygen metabolism, homeostasis of inorganic ions and execution of apoptosis. Biogenesis of mitochondria relies on protein import pathways that are ensured by dedicated multiprotein translocase complexes localized in all sub-compartments of these organelles. The key components and pathways involved in protein targeting and assembly have been characterized in great detail over the last three decades. This includes the oxidative folding machinery in the intermembrane space, which contributes to the redox-dependent control of proteostasis. Here, we focus on several components of this system and discuss recent evidence suggesting links to human proteopathy.
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43
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Granzyme B enters the mitochondria in a Sam50-, Tim22- and mtHsp70-dependent manner to induce apoptosis. Cell Death Differ 2017; 24:747-758. [PMID: 28338658 DOI: 10.1038/cdd.2017.3] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2016] [Revised: 12/07/2016] [Accepted: 12/23/2016] [Indexed: 12/22/2022] Open
Abstract
We have found that granzyme B (GB)-induced apoptosis also requires reactive oxygen species resulting from the alteration of mitochondrial complex I. How GB, which does not possess a mitochondrial targeting sequence, enter this organelle is unknown. We show that GB enters the mitochondria independently of the translocase of the outer mitochondrial membrane complex, but requires instead Sam50, the central subunit of the sorting and assembly machinery that integrates outer membrane β-barrel proteins. Moreover, GB breaches the inner membrane through Tim22, the metabolite carrier translocase pore, in a mitochondrial heat-shock protein 70 (mtHsp70)-dependent manner. Granzyme A (GA) and caspase-3 use a similar route to the mitochondria. Finally, preventing GB from entering the mitochondria either by mutating lysine 243 and arginine 244 or depleting Sam50 renders cells more resistant to GB-mediated reactive oxygen species and cell death. Similarly, Sam50 depletion protects cells from GA-, GM- and caspase-3-mediated cell death. Therefore, cytotoxic molecules enter the mitochondria to induce efficiently cell death through a noncanonical Sam50-, Tim22- and mtHsp70-dependent import pathway.
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44
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Role of Tim17 Transmembrane Regions in Regulating the Architecture of Presequence Translocase and Mitochondrial DNA Stability. Mol Cell Biol 2017; 37:MCB.00491-16. [PMID: 27994013 DOI: 10.1128/mcb.00491-16] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2016] [Accepted: 12/11/2016] [Indexed: 12/11/2022] Open
Abstract
Mitochondrial life cycle and protein import are intricate cellular processes, which require precise coordination between the transport machineries of outer and inner mitochondrial membranes. Presequence translocase performs the indispensable function of translocating preproteins having N-terminal targeting sequences across the inner membrane. Tim23 forms the core of the voltage-gated import channel, while Tim17 is presumed to maintain the stoichiometry of the translocase. However, mechanistic insights into how Tim17 coordinates these regulatory events within the complex remained elusive. We demonstrate that Tim17 harbors conserved G/AXXXG/A motifs within its transmembrane regions and plays an imperative role in the translocase assembly through interaction with Tim23. Tandem motifs are highly essential, as most of the amino acid substitutions lead to nonviability due to the complete destabilization of the TIM23 channel. Importantly, Tim17 transmembrane regions regulate the dynamic assembly of translocase to form either the TIM23 (PAM)-complex or TIM23 (SORT)-complex by recruiting the presequence translocase-associated motor (PAM) machinery or Tim21, respectively. To a greater significance, tim17 mutants displayed mitochondrial DNA (mtDNA) instability, membrane potential loss, and defective import, resulting in organellar dysfunction. We conclude that the integrity of Tim17 transmembrane regions is critical for mitochondrial function and protein turnover.
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45
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Abstract
The budding yeast Saccharomyces cerevisiae is an important model organism to study cellular structure and function. Due to its excellent accessibility to genetics and biochemical and microscopic analyses, studies with yeast have provided fundamental insights into mitochondrial biology. Yeast offers additional advantages because it can grow under fermenting conditions when oxidative phosphorylation is not obligatory and because the majority of mitochondrial structure and function are largely conserved during evolution. Isolation of mitochondria is an important technique for mitochondrial studies. This chapter focuses on procedures for the isolation and purification of intact yeast mitochondria that can be used for numerous functional assays as well as for analyses of mitochondrial ultrastructure.
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Affiliation(s)
- Toshiaki Izawa
- Max Planck Institute of Biochemistry, Am Klopferspitz 18, 82152, Martinsried, Germany.
| | - Ann-Katrin Unger
- Cell Biology and Electron Microscopy, Institut für Zellbiologie, Universität Bayreuth, 95440, Bayreuth, Germany
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46
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Shahrour MA, Staretz-Chacham O, Dayan D, Stephen J, Weech A, Damseh N, Pri Chen H, Edvardson S, Mazaheri S, Saada A, Hershkovitz E, Shaag A, Huizing M, Abu-Libdeh B, Gahl WA, Azem A, Anikster Y, Vilboux T, Elpeleg O, Malicdan MC. Mitochondrial epileptic encephalopathy, 3-methylglutaconic aciduria and variable complex V deficiency associated with TIMM50 mutations. Clin Genet 2016; 91:690-696. [PMID: 27573165 DOI: 10.1111/cge.12855] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2016] [Revised: 08/24/2016] [Accepted: 08/25/2016] [Indexed: 11/26/2022]
Abstract
Mitochondrial encephalopathies are a heterogeneous group of disorders that, usually carry grave prognosis. Recently a homozygous mutation, Gly372Ser, in the TIMM50 gene, was reported in an abstract form, in three sibs who suffered from intractable epilepsy and developmental delay accompanied by 3-methylglutaconic aciduria. We now report on four patients from two unrelated families who presented with severe intellectual disability and seizure disorder, accompanied by slightly elevated lactate level, 3-methylglutaconic aciduria and variable deficiency of mitochondrial complex V. Using exome analysis we identified two homozygous missense mutations, Arg217Trp and Thr252Met, in the TIMM50 gene. The TIMM50 protein is a subunit of TIM23 complex, the mitochondrial import machinery. It serves as the major receptor in the intermembrane space, binding to proteins which cross the mitochondrial inner membrane on their way to the matrix. The mutations, which affected evolutionary conserved residues and segregated with the disease in the families, were neither present in large cohorts of control exome analyses nor in our ethnic specific exome cohort. Given the phenotypic similarity, we conclude that missense mutations in TIMM50 are likely manifesting by severe intellectual disability and epilepsy accompanied by 3-methylglutaconic aciduria and variable mitochondrial complex V deficiency. 3-methylglutaconic aciduria is emerging as an important biomarker for mitochondrial dysfunction, in particular for mitochondrial membrane defects.
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Affiliation(s)
- M A Shahrour
- Department of Pediatrics, Al-Makassed Islamic Hospital, Jerusalem, Israel
| | - O Staretz-Chacham
- Metabolic Disease Unit, Soroka Medical Center, Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer Sheba, Israel
| | - D Dayan
- Department of Biochemistry & Molecular Biology, Tel Aviv University, Tel Aviv, Israel
| | - J Stephen
- Section of Human Biochemical Genetics, Medical Genetics Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD, USA
| | - A Weech
- NIH Undiagnosed Diseases Program, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD, USA
| | - N Damseh
- Department of Pediatrics, Al-Makassed Islamic Hospital, Jerusalem, Israel
| | - H Pri Chen
- Department of Biochemistry & Molecular Biology, Tel Aviv University, Tel Aviv, Israel.,Section of Human Biochemical Genetics, Medical Genetics Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD, USA.,Graduate Partnerships Program, Tel Aviv University, Tel Aviv, Israel, and the National Institutes of Health, Bethesda, MD, USA
| | - S Edvardson
- Pediatric Neurology Unit, Hadassah, Hebrew University Medical Center Jerusalem, Jerusalem, Israel
| | - S Mazaheri
- Section of Human Biochemical Genetics, Medical Genetics Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD, USA
| | - A Saada
- Monique and Jacques Roboh Department of Genetic Research, Hadassah, Hebrew University Medical Center Jerusalem, Jerusalem, Israel
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- NIH Intramural Sequencing Center (NISC), National Human Genome Research Institute, National Institutes of Health, Bethesda, MD, USA
| | - E Hershkovitz
- Metabolic Disease Unit, Soroka Medical Center, Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer Sheba, Israel
| | - A Shaag
- NIH Intramural Sequencing Center (NISC), National Human Genome Research Institute, National Institutes of Health, Bethesda, MD, USA
| | - M Huizing
- Section of Human Biochemical Genetics, Medical Genetics Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD, USA
| | - B Abu-Libdeh
- Department of Pediatrics, Al-Makassed Islamic Hospital, Jerusalem, Israel
| | - W A Gahl
- Section of Human Biochemical Genetics, Medical Genetics Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD, USA.,NIH Undiagnosed Diseases Program, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD, USA
| | - A Azem
- Department of Biochemistry & Molecular Biology, Tel Aviv University, Tel Aviv, Israel
| | - Y Anikster
- Metabolic Disease Unit, Edmond and Lily Safra Children's Hospital, Sheba Medical Center, Tel-Hashomer, Israel.,Sackler Faculty of Medicine, Tel-Aviv University, Tel-Aviv, Israel
| | - T Vilboux
- NIH Undiagnosed Diseases Program, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD, USA.,Division of Medical Genomics, Inova Translational Medicine Institute, Fairfax, VA, USA
| | - O Elpeleg
- NIH Intramural Sequencing Center (NISC), National Human Genome Research Institute, National Institutes of Health, Bethesda, MD, USA
| | - M C Malicdan
- Section of Human Biochemical Genetics, Medical Genetics Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD, USA.,NIH Undiagnosed Diseases Program, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD, USA
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47
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Demishtein-Zohary K, Azem A. The TIM23 mitochondrial protein import complex: function and dysfunction. Cell Tissue Res 2016; 367:33-41. [DOI: 10.1007/s00441-016-2486-7] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2016] [Accepted: 08/05/2016] [Indexed: 01/16/2023]
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48
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Banerjee R, Gladkova C, Mapa K, Witte G, Mokranjac D. Protein translocation channel of mitochondrial inner membrane and matrix-exposed import motor communicate via two-domain coupling protein. eLife 2015; 4:e11897. [PMID: 26714107 PMCID: PMC4749553 DOI: 10.7554/elife.11897] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2015] [Accepted: 12/28/2015] [Indexed: 12/18/2022] Open
Abstract
The majority of mitochondrial proteins are targeted to mitochondria by N-terminal presequences and use the TIM23 complex for their translocation across the mitochondrial inner membrane. During import, translocation through the channel in the inner membrane is coupled to the ATP-dependent action of an Hsp70-based import motor at the matrix face. How these two processes are coordinated remained unclear. We show here that the two domain structure of Tim44 plays a central role in this process. The N-terminal domain of Tim44 interacts with the components of the import motor, whereas its C-terminal domain interacts with the translocation channel and is in contact with translocating proteins. Our data suggest that the translocation channel and the import motor of the TIM23 complex communicate through rearrangements of the two domains of Tim44 that are stimulated by translocating proteins.
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Affiliation(s)
- Rupa Banerjee
- Biomedical Center Munich, Department of Physiological Chemistry, Ludwig-Maximilians-Universität, Munich, Germany
| | - Christina Gladkova
- Biomedical Center Munich, Department of Physiological Chemistry, Ludwig-Maximilians-Universität, Munich, Germany
| | - Koyeli Mapa
- Biomedical Center Munich, Department of Physiological Chemistry, Ludwig-Maximilians-Universität, Munich, Germany
| | - Gregor Witte
- Gene Center, Department of Biochemistry, Ludwig-Maximilians-Universität, Munich, Germany
| | - Dejana Mokranjac
- Biomedical Center Munich, Department of Physiological Chemistry, Ludwig-Maximilians-Universität, Munich, Germany
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49
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Li J, Sha B. The structure of Tim50(164-361) suggests the mechanism by which Tim50 receives mitochondrial presequences. Acta Crystallogr F Struct Biol Commun 2015; 71:1146-51. [PMID: 26323300 PMCID: PMC4555921 DOI: 10.1107/s2053230x15013102] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2014] [Accepted: 07/07/2015] [Indexed: 01/04/2023] Open
Abstract
Mitochondrial preproteins are transported through the translocase of the outer membrane (TOM) complex. Tim50 and Tim23 then transfer preproteins with N-terminal targeting presequences through the intermembrane space (IMS) across the inner membrane. The crystal structure of the IMS domain of Tim50 [Tim50(164-361)] has previously been determined to 1.83 Å resolution. Here, the crystal structure of Tim50(164-361) at 2.67 Å resolution that was crystallized using a different condition is reported. Compared with the previously determined Tim50(164-361) structure, significant conformational changes occur within the protruding β-hairpin of Tim50 and the nearby helix A2. These findings indicate that the IMS domain of Tim50 exhibits significant structural plasticity within the putative presequence-binding groove, which may play important roles in the function of Tim50 as a receptor protein in the TIM complex that interacts with the presequence and multiple other proteins. More interestingly, the crystal packing indicates that helix A1 from the neighboring monomer docks into the putative presequence-binding groove of Tim50(164-361), which may mimic the scenario of Tim50 and the presequence complex. Tim50 may recognize and bind the presequence helix by utilizing the inner side of the protruding β-hairpin through hydrophobic interactions. Therefore, the protruding β-hairpin of Tim50 may play critical roles in receiving the presequence and recruiting Tim23 for subsequent protein translocations.
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Affiliation(s)
- Jingzhi Li
- Department of Cell, Developmental and Integrative Biology (CDIB), University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | - Bingdong Sha
- Department of Cell, Developmental and Integrative Biology (CDIB), University of Alabama at Birmingham, Birmingham, AL 35294, USA
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50
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Loss of TIM50 suppresses proliferation and induces apoptosis in breast cancer. Tumour Biol 2015; 37:1279-87. [DOI: 10.1007/s13277-015-3878-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2015] [Accepted: 07/30/2015] [Indexed: 10/23/2022] Open
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