1
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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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2
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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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3
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Sim SI, Chen Y, Lynch DL, Gumbart JC, Park E. Structural basis of mitochondrial protein import by the TIM23 complex. Nature 2023; 621:620-626. [PMID: 37344598 DOI: 10.1038/s41586-023-06239-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2021] [Accepted: 05/19/2023] [Indexed: 06/23/2023]
Abstract
Mitochondria import nearly all of their approximately 1,000-2,000 constituent proteins from the cytosol across their double-membrane envelope1-5. Genetic and biochemical studies have shown that the conserved protein translocase, termed the TIM23 complex, mediates import of presequence-containing proteins (preproteins) into the mitochondrial matrix and inner membrane. Among about ten different subunits of the TIM23 complex, the essential multipass membrane protein Tim23, together with the evolutionarily related protein Tim17, has long been postulated to form a protein-conducting channel6-11. However, the mechanism by which these subunits form a translocation path in the membrane and enable the import process remains unclear due to a lack of structural information. Here we determined the cryo-electron microscopy structure of the core TIM23 complex (heterotrimeric Tim17-Tim23-Tim44) from Saccharomyces cerevisiae. Contrary to the prevailing model, Tim23 and Tim17 themselves do not form a water-filled channel, but instead have separate, lipid-exposed concave cavities that face in opposite directions. Our structural and biochemical analyses show that the cavity of Tim17, but not Tim23, forms the protein translocation path, whereas Tim23 probably has a structural role. The results further suggest that, during translocation of substrate polypeptides, the nonessential subunit Mgr2 seals the lateral opening of the Tim17 cavity to facilitate the translocation process. We propose a new model for the TIM23-mediated protein import and sorting mechanism, a central pathway in mitochondrial biogenesis.
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Affiliation(s)
- Sue Im Sim
- Department of Molecular and Cell Biology, University of California, Berkeley, CA, USA
| | - Yuanyuan Chen
- Department of Molecular and Cell Biology, University of California, Berkeley, CA, USA
- California Institute for Quantitative Biosciences, University of California, Berkeley, CA, USA
| | - Diane L Lynch
- School of Physics, Georgia Institute of Technology, Atlanta, GA, USA
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA, USA
| | - James C Gumbart
- School of Physics, Georgia Institute of Technology, Atlanta, GA, USA
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA, USA
| | - Eunyong Park
- Department of Molecular and Cell Biology, University of California, Berkeley, CA, USA.
- California Institute for Quantitative Biosciences, University of California, Berkeley, CA, USA.
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4
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Protein import motor complex reacts to mitochondrial misfolding by reducing protein import and activating mitophagy. Nat Commun 2022; 13:5164. [PMID: 36056001 PMCID: PMC9440083 DOI: 10.1038/s41467-022-32564-x] [Citation(s) in RCA: 20] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2021] [Accepted: 08/05/2022] [Indexed: 11/08/2022] Open
Abstract
Mitophagy is essential to maintain mitochondrial function and prevent diseases. It activates upon mitochondria depolarization, which causes PINK1 stabilization on the mitochondrial outer membrane. Strikingly, a number of conditions, including mitochondrial protein misfolding, can induce mitophagy without a loss in membrane potential. The underlying molecular details remain unclear. Here, we report that a loss of mitochondrial protein import, mediated by the pre-sequence translocase-associated motor complex PAM, is sufficient to induce mitophagy in polarized mitochondria. A genome-wide CRISPR/Cas9 screen for mitophagy inducers identifies components of the PAM complex. Protein import defects are able to induce mitophagy without a need for depolarization. Upon mitochondrial protein misfolding, PAM dissociates from the import machinery resulting in decreased protein import and mitophagy induction. Our findings extend the current mitophagy model to explain mitophagy induction upon conditions that do not affect membrane polarization, such as mitochondrial protein misfolding. Mitophagy activation is mediated by mitochondrial depolarization. Here, the authors show that mitochondrial protein misfolding can activate mitophagy in a depolarization-independent manner mediated by a protein import reduction.
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5
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Spatiotemporal stop-and-go dynamics of the mitochondrial TOM core complex correlates with channel activity. Commun Biol 2022; 5:471. [PMID: 35581327 PMCID: PMC9114391 DOI: 10.1038/s42003-022-03419-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2021] [Accepted: 04/26/2022] [Indexed: 11/08/2022] Open
Abstract
Single-molecule studies can reveal phenomena that remain hidden in ensemble measurements. Here we show the correlation between lateral protein diffusion and channel activity of the general protein import pore of mitochondria (TOM-CC) in membranes resting on ultrathin hydrogel films. Using electrode-free optical recordings of ion flux, we find that TOM-CC switches reversibly between three states of ion permeability associated with protein diffusion. While freely diffusing TOM-CC molecules are predominantly in a high permeability state, non-mobile molecules are mostly in an intermediate or low permeability state. We explain this behavior by the mechanical binding of the two protruding Tom22 subunits to the hydrogel and a concomitant combinatorial opening and closing of the two β-barrel pores of TOM-CC. TOM-CC could thus represent a β-barrel membrane protein complex to exhibit membrane state-dependent mechanosensitive properties, mediated by its two Tom22 subunits.
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6
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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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7
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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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8
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Zhao F, Zou MH. Role of the Mitochondrial Protein Import Machinery and Protein Processing in Heart Disease. Front Cardiovasc Med 2021; 8:749756. [PMID: 34651031 PMCID: PMC8505727 DOI: 10.3389/fcvm.2021.749756] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2021] [Accepted: 08/26/2021] [Indexed: 12/12/2022] Open
Abstract
Mitochondria are essential organelles for cellular energy production, metabolic homeostasis, calcium homeostasis, cell proliferation, and apoptosis. About 99% of mammalian mitochondrial proteins are encoded by the nuclear genome, synthesized as precursors in the cytosol, and imported into mitochondria by mitochondrial protein import machinery. Mitochondrial protein import systems function not only as independent units for protein translocation, but also are deeply integrated into a functional network of mitochondrial bioenergetics, protein quality control, mitochondrial dynamics and morphology, and interaction with other organelles. Mitochondrial protein import deficiency is linked to various diseases, including cardiovascular disease. In this review, we describe an emerging class of protein or genetic variations of components of the mitochondrial import machinery involved in heart disease. The major protein import pathways, including the presequence pathway (TIM23 pathway), the carrier pathway (TIM22 pathway), and the mitochondrial intermembrane space import and assembly machinery, related translocases, proteinases, and chaperones, are discussed here. This review highlights the importance of mitochondrial import machinery in heart disease, which deserves considerable attention, and further studies are urgently needed. Ultimately, this knowledge may be critical for the development of therapeutic strategies in heart disease.
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Affiliation(s)
- Fujie Zhao
- Center for Molecular and Translational Medicine, Georgia State University, Atlanta, GA, United States
| | - Ming-Hui Zou
- Center for Molecular and Translational Medicine, Georgia State University, Atlanta, GA, United States
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9
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Dimogkioka AR, Lees J, Lacko E, Tokatlidis K. Protein import in mitochondria biogenesis: guided by targeting signals and sustained by dedicated chaperones. RSC Adv 2021; 11:32476-32493. [PMID: 35495482 PMCID: PMC9041937 DOI: 10.1039/d1ra04497d] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2021] [Accepted: 09/25/2021] [Indexed: 12/31/2022] Open
Abstract
Mitochondria have a central role in cellular metabolism; they are responsible for the biosynthesis of amino acids, lipids, iron-sulphur clusters and regulate apoptosis. About 99% of mitochondrial proteins are encoded by nuclear genes, so the biogenesis of mitochondria heavily depends on protein import pathways into the organelle. An intricate system of well-studied import machinery facilitates the import of mitochondrial proteins. In addition, folding of the newly synthesized proteins takes place in a busy environment. A system of folding helper proteins, molecular chaperones and co-chaperones, are present to maintain proper conformation and thus avoid protein aggregation and premature damage. The components of the import machinery are well characterised, but the targeting signals and how they are recognised and decoded remains in some cases unclear. Here we provide some detail on the types of targeting signals involved in the protein import process. Furthermore, we discuss the very elaborate chaperone systems of the intermembrane space that are needed to overcome the particular challenges for the folding process in this compartment. The mechanisms that sustain productive folding in the face of aggregation and damage in mitochondria are critical components of the stress response and play an important role in cell homeostasis.
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Affiliation(s)
- Anna-Roza Dimogkioka
- Institute of Molecular Cell and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow University Avenue Glasgow G12 8QQ Scotland UK
| | - Jamie Lees
- Institute of Molecular Cell and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow University Avenue Glasgow G12 8QQ Scotland UK
| | - Erik Lacko
- Institute of Molecular Cell and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow University Avenue Glasgow G12 8QQ Scotland UK
| | - Kostas Tokatlidis
- Institute of Molecular Cell and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow University Avenue Glasgow G12 8QQ Scotland UK
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10
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Quality control of protein import into mitochondria. Biochem J 2021; 478:3125-3143. [PMID: 34436539 DOI: 10.1042/bcj20190584] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2021] [Revised: 07/29/2021] [Accepted: 08/03/2021] [Indexed: 12/19/2022]
Abstract
Mitochondria import about 1000 proteins that are produced as precursors on cytosolic ribosomes. Defects in mitochondrial protein import result in the accumulation of non-imported precursor proteins and proteotoxic stress. The cell is equipped with different quality control mechanisms to monitor protein transport into mitochondria. First, molecular chaperones guide unfolded proteins to mitochondria and deliver non-imported proteins to proteasomal degradation. Second, quality control factors remove translocation stalled precursor proteins from protein translocases. Third, protein translocases monitor protein sorting to mitochondrial subcompartments. Fourth, AAA proteases of the mitochondrial subcompartments remove mislocalized or unassembled proteins. Finally, impaired efficiency of protein transport is an important sensor for mitochondrial dysfunction and causes the induction of cellular stress responses, which could eventually result in the removal of the defective mitochondria by mitophagy. In this review, we summarize our current understanding of quality control mechanisms that govern mitochondrial protein transport.
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11
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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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12
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Sensing, signaling and surviving mitochondrial stress. Cell Mol Life Sci 2021; 78:5925-5951. [PMID: 34228161 PMCID: PMC8316193 DOI: 10.1007/s00018-021-03887-7] [Citation(s) in RCA: 40] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2021] [Revised: 06/15/2021] [Accepted: 06/22/2021] [Indexed: 12/11/2022]
Abstract
Mitochondrial fidelity is a key determinant of longevity and was found to be perturbed in a multitude of disease contexts ranging from neurodegeneration to heart failure. Tight homeostatic control of the mitochondrial proteome is a crucial aspect of mitochondrial function, which is severely complicated by the evolutionary origin and resulting peculiarities of the organelle. This is, on one hand, reflected by a range of basal quality control factors such as mitochondria-resident chaperones and proteases, that assist in import and folding of precursors as well as removal of aggregated proteins. On the other hand, stress causes the activation of several additional mechanisms that counteract any damage that may threaten mitochondrial function. Countermeasures depend on the location and intensity of the stress and on a range of factors that are equipped to sense and signal the nature of the encountered perturbation. Defective mitochondrial import activates mechanisms that combat the accumulation of precursors in the cytosol and the import pore. To resolve proteotoxic stress in the organelle interior, mitochondria depend on nuclear transcriptional programs, such as the mitochondrial unfolded protein response and the integrated stress response. If organelle damage is too severe, mitochondria signal for their own destruction in a process termed mitophagy, thereby preventing further harm to the mitochondrial network and allowing the cell to salvage their biological building blocks. Here, we provide an overview of how different types and intensities of stress activate distinct pathways aimed at preserving mitochondrial fidelity.
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13
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Molecular Insights into Mitochondrial Protein Translocation and Human Disease. Genes (Basel) 2021; 12:genes12071031. [PMID: 34356047 PMCID: PMC8305315 DOI: 10.3390/genes12071031] [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] [Received: 05/29/2021] [Revised: 06/27/2021] [Accepted: 06/30/2021] [Indexed: 12/11/2022] Open
Abstract
In human mitochondria, mtDNA encodes for only 13 proteins, all components of the OXPHOS system. The rest of the mitochondrial components, which make up approximately 99% of its proteome, are encoded in the nuclear genome, synthesized in cytosolic ribosomes and imported into mitochondria. Different import machineries translocate mitochondrial precursors, depending on their nature and the final destination inside the organelle. The proper and coordinated function of these molecular pathways is critical for mitochondrial homeostasis. Here, we will review molecular details about these pathways, which components have been linked to human disease and future perspectives on the field to expand the genetic landscape of mitochondrial diseases.
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14
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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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15
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Shiino H, Furuta S, Kojima R, Kimura K, Endo T, Tamura Y. Phosphatidylserine flux into mitochondria unveiled by organelle-targeted Escherichia coli phosphatidylserine synthase PssA. FEBS J 2020; 288:3285-3299. [PMID: 33283454 DOI: 10.1111/febs.15657] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2020] [Revised: 11/12/2020] [Accepted: 12/04/2020] [Indexed: 11/26/2022]
Abstract
Most phospholipids are synthesised in the endoplasmic reticulum and distributed to other cellular membranes. Although the vesicle transport contributes to the phospholipid distribution among the endomembrane system, exactly how phospholipids are transported to, from and between mitochondrial membranes remains unclear. To gain insights into phospholipid transport routes into mitochondria, we expressed the Escherichia coli phosphatidylserine (PS) synthase PssA in various membrane compartments with distinct membrane topologies in yeast cells lacking a sole PS synthase (Cho1). Interestingly, PssA could complement loss of Cho1 when targeted to the endoplasmic reticulum (ER), peroxisome, or lipid droplet membranes. Synthesised PS could be converted to phosphatidylethanolamine (PE) by Psd1, the mitochondrial PS decarboxylase, suggesting that phospholipids synthesised in the peroxisomes and low doses (LDs) can efficiently reach mitochondria. Furthermore, we found that PssA which has been integrated into the mitochondrial inner membrane (MIM) from the matrix side could partially complement the loss of Cho1. The PS synthesised in the MIM was also converted to PE, indicating that PS flops across the MIM to become PE. These findings expand our understanding of the intracellular phospholipid transport routes via mitochondria.
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Affiliation(s)
| | | | | | | | - Toshiya Endo
- Faculty of Life Sciences, Kyoto Sangyo University, Japan.,Institute for Protein Dynamics, Kyoto Sangyo University, Japan
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16
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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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17
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Abstract
The past several decades have witnessed tremendous growth in the protein targeting, transport and translocation field. Major advances were made during this time period. Now the molecular details of the targeting factors, receptors and the membrane channels that were envisioned in Blobel's Signal Hypothesis in the 1970s have been revealed by powerful structural methods. It is evident that there is a myriad of cytosolic and membrane associated systems that accurately sort and target newly synthesized proteins to their correct membrane translocases for membrane insertion or protein translocation. Here we will describe the common principles for protein transport in prokaryotes and eukaryotes.
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18
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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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19
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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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20
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A mutagenesis analysis of Tim50, the major receptor of the TIM23 complex, identifies regions that affect its interaction with Tim23. Sci Rep 2019; 9:2012. [PMID: 30765764 PMCID: PMC6375917 DOI: 10.1038/s41598-018-38353-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2017] [Accepted: 12/27/2018] [Indexed: 12/03/2022] Open
Abstract
Maintenance of the mitochondrial proteome depends on import of newly made proteins from the cytosol. More than half of mitochondrial proteins are made as precursor proteins with N-terminal extensions called presequences and use the TIM23 complex for translocation into the matrix, the inner mitochondrial membrane and the intermembrane space (IMS). Tim50 is the central receptor of the complex that recognizes precursor proteins in the IMS. Additionally, Tim50 interacts with the IMS domain of the channel forming subunit, Tim23, an interaction that is essential for protein import across the mitochondrial inner membrane. In order to gain deeper insight into the molecular function of Tim50, we used random mutagenesis to determine residues that are important for its function. The temperature-sensitive mutants isolated were defective in import of TIM23-dependent precursor proteins. The residues mutated map to two distinct patches on the surface of Tim50. Notably, mutations in both patches impaired the interaction of Tim50 with Tim23. We propose that two regions of Tim50 play a role in its interaction with Tim23 and thereby affect the import function of the complex.
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21
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Mirzalieva O, Jeon S, Damri K, Hartke R, Drwesh L, Demishtein-Zohary K, Azem A, Dunn CD, Peixoto PM. Deletion of Mgr2p Affects the Gating Behavior of the TIM23 Complex. Front Physiol 2019; 9:1960. [PMID: 30697167 PMCID: PMC6340964 DOI: 10.3389/fphys.2018.01960] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2018] [Accepted: 12/28/2018] [Indexed: 11/13/2022] Open
Abstract
The TIM23 complex is a hub for translocation of preproteins into or across the mitochondrial inner membrane. This dual sorting mechanism is currently being investigated, and in yeast appears to be regulated by a recently discovered subunit, the Mgr2 protein. Deletion of Mgr2p has been found to delay protein translocation into the matrix and accumulation in the inner membrane. This result and other findings suggested that Mgr2p controls the lateral release of inner membrane proteins harboring a stop-transfer signal that follows an N-terminal amino acid signal. However, the mechanism of lateral release is unknown. Here, we used patch clamp electrophysiology to investigate the role of Mgr2p on the channel activity of TIM23. Deletion of Mgr2p decreased normal channel frequency and increased occurrence of a residual TIM23 activity. The residual channel lacked gating transitions but remained sensitive to synthetic import signal peptides. Similarly, a G145L mutation in Tim23p displaced Mgr2p from the import complex leading to gating impairment. These results suggest that Mgr2p regulates the gating behavior of the TIM23 channel.
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Affiliation(s)
- Oygul Mirzalieva
- Department of Natural Sciences, Baruch College, The City University of New York, New York City, NY, United States
| | - Shinhye Jeon
- Department of Natural Sciences, Baruch College, The City University of New York, New York City, NY, United States
| | - Kevin Damri
- Department of Natural Sciences, Baruch College, The City University of New York, New York City, NY, United States
| | - Ruth Hartke
- Department of Natural Sciences, Baruch College, The City University of New York, New York City, NY, United States
| | - Layla Drwesh
- Department of Biochemistry and Molecular Biology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
| | - Keren Demishtein-Zohary
- Department of Biochemistry and Molecular Biology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
| | - Abdussalam Azem
- Department of Biochemistry and Molecular Biology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
| | - Cory D Dunn
- Institute of Biotechnology, Helsinki Institute of Life Science, University of Helsinki, Helsinki, Finland.,Department of Molecular Biology and Genetics, Koç University, Istanbul, Turkey
| | - Pablo M Peixoto
- Department of Natural Sciences, Baruch College, The City University of New York, New York City, NY, United States.,MCD Program, The Graduate Center, The City University of New York, New York City, NY, United States
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22
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Inner Mitochondrial Translocase Tim50 Is Central in Adrenal and Testicular Steroid Synthesis. Mol Cell Biol 2018; 39:MCB.00484-18. [PMID: 30348838 DOI: 10.1128/mcb.00484-18] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2018] [Accepted: 10/14/2018] [Indexed: 01/24/2023] Open
Abstract
Adrenal and gonadal mitochondrial metabolic activity requires electrons from cofactors, cholesterol, and a substrate for rapid steroid synthesis, an essential requirement for mammalian survival. Substrate activity depends on its environment, which is regulated by chaperones and mitochondrial translocases. Cytochrome P450 side-chain cleavage enzyme (SCC or CYP11A1) catalyzes cholesterol to pregnenolone conversion, although its mechanism of action is not well understood. We find that SCC is directly imported into the mitochondrial matrix, where its N-terminal sequence is cleaved sequentially, after which it becomes activated following the second cleavage, which is dependent on the folding of the protein. Following integration of the SCC C terminus into the TIM23 complex, amino acids 141 to 146 interact with the intermembrane-exposed Tim50 protein, forming a large complex. The absence of Tim50 or its mutation reduced enzymatic activity. For the first time, we report that a protein activated at the matrix remains mostly unfolded and is transported back to the IMS to integrate with the TIM23 translocase complex and align with the Tim50 protein. Amino acid changes that suppress the association of Tim50 with SCC ablate metabolic activity. Thus, the TIM23 complex is the central regulator of metabolism guided by Tim50.
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23
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Backes S, Herrmann JM. Protein Translocation into the Intermembrane Space and Matrix of Mitochondria: Mechanisms and Driving Forces. Front Mol Biosci 2017; 4:83. [PMID: 29270408 PMCID: PMC5725982 DOI: 10.3389/fmolb.2017.00083] [Citation(s) in RCA: 63] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2017] [Accepted: 11/24/2017] [Indexed: 11/17/2022] Open
Abstract
Mitochondria contain two aqueous subcompartments, the matrix and the intermembrane space (IMS). The matrix is enclosed by both the inner and outer mitochondrial membranes, whilst the IMS is sandwiched between the two. Proteins of the matrix are synthesized in the cytosol as preproteins, which contain amino-terminal matrix targeting sequences that mediate their translocation through translocases embedded in the outer and inner membrane. For these proteins, the translocation reaction is driven by the import motor which is part of the inner membrane translocase. The import motor employs matrix Hsp70 molecules and ATP hydrolysis to ratchet proteins into the mitochondrial matrix. Most IMS proteins lack presequences and instead utilize the IMS receptor Mia40, which facilitates their translocation across the outer membrane in a reaction that is coupled to the formation of disulfide bonds within the protein. This process requires neither ATP nor the mitochondrial membrane potential. Mia40 fulfills two roles: First, it acts as a holdase, which is crucial in the import of IMS proteins and second, it functions as a foldase, introducing disulfide bonds into newly imported proteins, which induces and stabilizes their natively folded state. For several Mia40 substrates, oxidative folding is an essential prerequisite for their assembly into oligomeric complexes. Interestingly, recent studies have shown that the two functions of Mia40 can be experimentally separated from each other by the use of specific mutants, hence providing a powerful new way to dissect the different physiological roles of Mia40. In this review we summarize the current knowledge relating to the mitochondrial matrix-targeting and the IMS-targeting/Mia40 pathway. Moreover, we discuss the mechanistic properties by which the mitochondrial import motor on the one hand and Mia40 on the other, drive the translocation of their substrates into the organelle. We propose that the lateral diffusion of Mia40 in the inner membrane and the oxidation-mediated folding of incoming polypeptides supports IMS import.
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Affiliation(s)
- Sandra Backes
- Cell Biology, University of Kaiserslautern, Kaiserslautern, Germany
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24
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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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25
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Straub SP, Stiller SB, Wiedemann N, Pfanner N. Dynamic organization of the mitochondrial protein import machinery. Biol Chem 2017; 397:1097-1114. [PMID: 27289000 DOI: 10.1515/hsz-2016-0145] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2016] [Accepted: 05/17/2016] [Indexed: 01/12/2023]
Abstract
Mitochondria contain elaborate machineries for the import of precursor proteins from the cytosol. The translocase of the outer mitochondrial membrane (TOM) performs the initial import of precursor proteins and transfers the precursors to downstream translocases, including the presequence translocase and the carrier translocase of the inner membrane, the mitochondrial import and assembly machinery of the intermembrane space, and the sorting and assembly machinery of the outer membrane. Although the protein translocases can function as separate entities in vitro, recent studies revealed a close and dynamic cooperation of the protein import machineries to facilitate efficient transfer of precursor proteins in vivo. In addition, protein translocases were found to transiently interact with distinct machineries that function in the respiratory chain or in the maintenance of mitochondrial membrane architecture. Mitochondrial protein import is embedded in a regulatory network that ensures protein biogenesis, membrane dynamics, bioenergetic activity and quality control.
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26
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Tang K, Zhao Y, Li H, Zhu M, Li W, Liu W, Zhu G, Xu D, Peng W, Xu YW. Translocase of Inner Membrane 50 Functions as a Novel Protective Regulator of Pathological Cardiac Hypertrophy. J Am Heart Assoc 2017; 6:JAHA.116.004346. [PMID: 28432072 PMCID: PMC5532988 DOI: 10.1161/jaha.116.004346] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
BACKGROUND Translocase of inner membrane 50 (TIM50) is a member of the translocase of inner membrane (TIM) complex in the mitochondria. Previous research has demonstrated the role of TIM50 in the regulation of oxidative stress and cardiac morphology. However, the role of TIM50 in pathological cardiac hypertrophy remains unknown. METHODS AND RESULTS In the present study we found that the expression of TIM50 was downregulated in hypertrophic hearts. Using genetic loss-of-function animal models, we demonstrated that TIM50 deficiency increased heart and cardiomyocyte size with more severe cardiac fibrosis compared with wild-type littermates. Moreover, we generated cardiomyocyte-specific TIM50 transgenic mice in which the hypertrophic and fibrotic phenotypes were all alleviated. Next, we tested reactive oxygen species generation and the activities of the antioxidant enzymes superoxide dismutase and catalase, and also respiratory chain complexes I, II, and IV, finding that all the activities were regulated by TIM50. Meanwhile, expression of the ASK1-JNK/P38 axis was increased in TIM50-deficient mice, and TIM50 overexpression decreased the activity of the ASK1-JNK/P38 axis. Finally, we treated mice with the antioxidant N-acetyl cysteine to reduce oxidative stress. After N-acetyl cysteine treatment, the deteriorative hypertrophic and fibrotic phenotypes caused by TIM50 deficiency were all remarkably reversed. CONCLUSIONS These data indicated that TIM50 could attenuate pathological cardiac hypertrophy primarily by reducing oxidative stress. TIM50 could be a promising target for the prevention and therapy of cardiac hypertrophy and heart failure.
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Affiliation(s)
- Kai Tang
- Department of Cardiology, Shanghai Tenth People's Hospital, Tongji University School of Medicine, Shanghai, China
| | - Yifan Zhao
- Department of Cardiology, Shanghai Tenth People's Hospital, Tongji University School of Medicine, Shanghai, China
| | - Hailing Li
- Department of Cardiology, Shanghai Tenth People's Hospital, Tongji University School of Medicine, Shanghai, China
| | - Mengyun Zhu
- Department of Cardiology, Shanghai Tenth People's Hospital, Tongji University School of Medicine, Shanghai, China
| | - Weiming Li
- Department of Cardiology, Shanghai Tenth People's Hospital, Tongji University School of Medicine, Shanghai, China
| | - Weijing Liu
- Department of Cardiology, Shanghai Tenth People's Hospital, Tongji University School of Medicine, Shanghai, China
| | - Guofu Zhu
- Department of Cardiology, Shanghai Tenth People's Hospital, Tongji University School of Medicine, Shanghai, China
| | - Dachun Xu
- Department of Cardiology, Shanghai Tenth People's Hospital, Tongji University School of Medicine, Shanghai, China
| | - Wenhui Peng
- Department of Cardiology, Shanghai Tenth People's Hospital, Tongji University School of Medicine, Shanghai, China
| | - Ya-Wei Xu
- Department of Cardiology, Shanghai Tenth People's Hospital, Tongji University School of Medicine, Shanghai, China
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27
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Demishtein-Zohary K, Günsel U, Marom M, Banerjee R, Neupert W, Azem A, Mokranjac D. Role of Tim17 in coupling the import motor to the translocation channel of the mitochondrial presequence translocase. eLife 2017; 6. [PMID: 28165323 PMCID: PMC5308891 DOI: 10.7554/elife.22696] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2016] [Accepted: 02/06/2017] [Indexed: 12/24/2022] Open
Abstract
The majority of mitochondrial proteins use N-terminal presequences for targeting to mitochondria and are translocated by the presequence translocase. During translocation, proteins, threaded through the channel in the inner membrane, are handed over to the import motor at the matrix face. Tim17 is an essential, membrane-embedded subunit of the translocase; however, its function is only poorly understood. Here, we functionally dissected its four predicted transmembrane (TM) segments. Mutations in TM1 and TM2 impaired the interaction of Tim17 with Tim23, component of the translocation channel, whereas mutations in TM3 compromised binding of the import motor. We identified residues in the matrix-facing region of Tim17 involved in binding of the import motor. Our results reveal functionally distinct roles of different regions of Tim17 and suggest how they may be involved in handing over the proteins, during their translocation into mitochondria, from the channel to the import motor of the presequence translocase. DOI:http://dx.doi.org/10.7554/eLife.22696.001
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Affiliation(s)
- Keren Demishtein-Zohary
- Department of Biochemistry and Molecular Biology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
| | - Umut Günsel
- BMC-Physiological Chemistry, LMU Munich, Martinsried, Germany
| | - Milit Marom
- Department of Biochemistry and Molecular Biology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
| | - Rupa Banerjee
- BMC-Physiological Chemistry, LMU Munich, Martinsried, Germany
| | - Walter Neupert
- Max Planck Institute of Biochemistry, Martinsried, Germany
| | - Abdussalam Azem
- Department of Biochemistry and Molecular Biology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
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28
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Harsman A, Schneider A. Mitochondrial protein import in trypanosomes: Expect the unexpected. Traffic 2017; 18:96-109. [PMID: 27976830 DOI: 10.1111/tra.12463] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2016] [Revised: 12/01/2016] [Accepted: 12/06/2016] [Indexed: 12/11/2022]
Abstract
Mitochondria have many different functions, the most important one of which is oxidative phosphorylation. They originated from an endosymbiotic event between a bacterium and an archaeal host cell. It was the evolution of a protein import system that marked the boundary between the endosymbiotic ancestor of the mitochondrion and a true organelle that is under the control of the nucleus. In present day mitochondria more than 95% of all proteins are imported from the cytosol in a proces mediated by hetero-oligomeric protein complexes in the outer and inner mitochondrial membranes. In this review we compare mitochondrial protein import in the best studied model system yeast and the parasitic protozoan Trypanosoma brucei. The 2 organisms are phylogenetically only remotely related. Despite the fact that mitochondrial protein import has the same function in both species, only very few subunits of their import machineries are conserved. Moreover, while yeast has 2 inner membrane protein translocases, one specialized for presequence-containing and one for mitochondrial carrier proteins, T. brucei has a single inner membrane translocase only, that mediates import of both types of substrates. The evolutionary implications of these findings are discussed.
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Affiliation(s)
- Anke Harsman
- Department of Chemistry and Biochemistry, University of Bern, Bern, Switzerland
| | - André Schneider
- Department of Chemistry and Biochemistry, University of Bern, Bern, Switzerland
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29
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Abstract
Mitochondria have to import the vast majority of their proteins, which are synthesized as precursors on cytosolic ribosomes. The translocase of the outer membrane (TOM complex) forms the general entry gate for the precursor proteins, which are subsequently sorted by protein machineries into the mitochondrial subcompartments: the outer and inner membrane, the intermembrane space and the mitochondrial matrix. The transport across and into the inner membrane is driven by the membrane potential, which is generated by the respiratory chain. Recent studies revealed that the lipid composition of mitochondrial membranes is important for the biogenesis of mitochondrial proteins. Cardiolipin and phosphatidylethanolamine exhibit unexpectedly specific functions for the activity of distinct protein translocases. Both phospholipids are required for full activity of respiratory chain complexes and thus to maintain the membrane potential for protein import. In addition, cardiolipin is required to maintain structural integrity of mitochondrial protein translocases. Finally, the low sterol content in the mitochondrial outer membrane may contribute to the targeting of some outer membrane proteins with a single α-helical membrane anchor. Altogether, mitochondrial lipids modulate protein import on various levels involving precursor targeting, membrane potential generation, stability and activity of protein translocases.
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30
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Harsman A, Oeljeklaus S, Wenger C, Huot JL, Warscheid B, Schneider A. The non-canonical mitochondrial inner membrane presequence translocase of trypanosomatids contains two essential rhomboid-like proteins. Nat Commun 2016; 7:13707. [PMID: 27991487 PMCID: PMC5187411 DOI: 10.1038/ncomms13707] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2016] [Accepted: 10/24/2016] [Indexed: 02/07/2023] Open
Abstract
Mitochondrial protein import is essential for all eukaryotes. Here we show that the early diverging eukaryote Trypanosoma brucei has a non-canonical inner membrane (IM) protein translocation machinery. Besides TbTim17, the single member of the Tim17/22/23 family in trypanosomes, the presequence translocase contains nine subunits that co-purify in reciprocal immunoprecipitations and with a presequence-containing substrate that is trapped in the translocation channel. Two of the newly discovered subunits are rhomboid-like proteins, which are essential for growth and mitochondrial protein import. Rhomboid-like proteins were proposed to form the protein translocation pore of the ER-associated degradation system, suggesting that they may contribute to pore formation in the presequence translocase of T. brucei. Pulldown of import-arrested mitochondrial carrier protein shows that the carrier translocase shares eight subunits with the presequence translocase. This indicates that T. brucei may have a single IM translocase that with compositional variations mediates import of presequence-containing and carrier proteins.
The mitochondrial protein import machinery is crucial for eukaryotes but little is known about its evolutionary origin. Here, the authors characterize the translocase of the inner membrane (TIM) in trypanosomes, showing that it contains two rhomboid-like proteins essential for protein import.
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Affiliation(s)
- Anke Harsman
- Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, Bern CH-3012, Switzerland
| | - Silke Oeljeklaus
- Department of Biochemistry and Functional Proteomics, Institute of Biology II, Faculty of Biology, University of Freiburg, Schänzlestraße 18, Freiburg 79104, Germany
| | - Christoph Wenger
- Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, Bern CH-3012, Switzerland
| | - Jonathan L Huot
- Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, Bern CH-3012, Switzerland
| | - Bettina Warscheid
- Department of Biochemistry and Functional Proteomics, Institute of Biology II, Faculty of Biology, University of Freiburg, Schänzlestraße 18, Freiburg 79104, Germany.,BIOSS Centre for Biological Signalling Studies, University of Freiburg, Schänzlestraße 18, Freiburg 79104, Germany
| | - André Schneider
- Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, Bern CH-3012, Switzerland
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31
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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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32
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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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33
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Kang Y, Baker MJ, Liem M, Louber J, McKenzie M, Atukorala I, Ang CS, Keerthikumar S, Mathivanan S, Stojanovski D. Tim29 is a novel subunit of the human TIM22 translocase and is involved in complex assembly and stability. eLife 2016; 5. [PMID: 27554484 PMCID: PMC5016092 DOI: 10.7554/elife.17463] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2016] [Accepted: 08/14/2016] [Indexed: 12/14/2022] Open
Abstract
The TIM22 complex mediates the import of hydrophobic carrier proteins into the mitochondrial inner membrane. While the TIM22 machinery has been well characterised in yeast, the human complex remains poorly characterised. Here, we identify Tim29 (C19orf52) as a novel, metazoan-specific subunit of the human TIM22 complex. The protein is integrated into the mitochondrial inner membrane with it's C-terminus exposed to the intermembrane space. Tim29 is required for the stability of the TIM22 complex and functions in the assembly of hTim22. Furthermore, Tim29 contacts the Translocase of the Outer Mitochondrial Membrane, TOM complex, enabling a mechanism for transport of hydrophobic carrier substrates across the aqueous intermembrane space. Identification of Tim29 highlights the significance of analysing mitochondrial import systems across phylogenetic boundaries, which can reveal novel components and mechanisms in higher organisms.
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Affiliation(s)
- Yilin Kang
- Department of Biochemistry and Molecular Biology, The University of Melbourne, Melbourne, Australia.,The Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Melbourne, Australia
| | - Michael James Baker
- Department of Biochemistry and Molecular Biology, The University of Melbourne, Melbourne, Australia.,The Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Melbourne, Australia
| | - Michael Liem
- Department of Biochemistry and Genetics, La Trobe University, Melbourne, Australia.,La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Australia
| | - Jade Louber
- Department of Biochemistry and Molecular Biology, The University of Melbourne, Melbourne, Australia.,The Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Melbourne, Australia
| | - Matthew McKenzie
- Centre for Genetic Diseases, Hudson Institute of Medical Research, Melbourne, Australia
| | - Ishara Atukorala
- Department of Biochemistry and Genetics, La Trobe University, Melbourne, Australia.,La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Australia
| | - Ching-Seng Ang
- The Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Melbourne, Australia
| | - Shivakumar Keerthikumar
- Department of Biochemistry and Genetics, La Trobe University, Melbourne, Australia.,La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Australia
| | - Suresh Mathivanan
- Department of Biochemistry and Genetics, La Trobe University, Melbourne, Australia.,La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Australia
| | - Diana Stojanovski
- Department of Biochemistry and Molecular Biology, The University of Melbourne, Melbourne, Australia.,The Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Melbourne, Australia
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34
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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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35
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Kunze M, Berger J. The similarity between N-terminal targeting signals for protein import into different organelles and its evolutionary relevance. Front Physiol 2015; 6:259. [PMID: 26441678 PMCID: PMC4585086 DOI: 10.3389/fphys.2015.00259] [Citation(s) in RCA: 73] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2015] [Accepted: 09/04/2015] [Indexed: 12/04/2022] Open
Abstract
The proper distribution of proteins between the cytosol and various membrane-bound compartments is crucial for the functionality of eukaryotic cells. This requires the cooperation between protein transport machineries that translocate diverse proteins from the cytosol into these compartments and targeting signal(s) encoded within the primary sequence of these proteins that define their cellular destination. The mechanisms exerting protein translocation differ remarkably between the compartments, but the predominant targeting signals for mitochondria, chloroplasts and the ER share the N-terminal position, an α-helical structural element and the removal from the core protein by intraorganellar cleavage. Interestingly, similar properties have been described for the peroxisomal targeting signal type 2 mediating the import of a fraction of soluble peroxisomal proteins, whereas other peroxisomal matrix proteins encode the type 1 targeting signal residing at the extreme C-terminus. The structural similarity of N-terminal targeting signals poses a challenge to the specificity of protein transport, but allows the generation of ambiguous targeting signals that mediate dual targeting of proteins into different compartments. Dual targeting might represent an advantage for adaptation processes that involve a redistribution of proteins, because it circumvents the hierarchy of targeting signals. Thus, the co-existence of two equally functional import pathways into peroxisomes might reflect a balance between evolutionary constant and flexible transport routes.
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Affiliation(s)
- Markus Kunze
- Department of Pathobiology of the Nervous System, Center for Brain Research, Medical University of Vienna Vienna, Austria
| | - Johannes Berger
- Department of Pathobiology of the Nervous System, Center for Brain Research, Medical University of Vienna Vienna, Austria
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36
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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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37
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Wang Y, Katayama A, Terami T, Han X, Nunoue T, Zhang D, Teshigawara S, Eguchi J, Nakatsuka A, Murakami K, Ogawa D, Furuta Y, Makino H, Wada J. Translocase of inner mitochondrial membrane 44 alters the mitochondrial fusion and fission dynamics and protects from type 2 diabetes. Metabolism 2015; 64:677-88. [PMID: 25749183 DOI: 10.1016/j.metabol.2015.02.004] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/17/2014] [Revised: 02/14/2015] [Accepted: 02/18/2015] [Indexed: 11/27/2022]
Abstract
OBJECTIVE In obesity and type 2 diabetes, the impairment of mitochondrial function in white adipose tissue (WAT) is linked to a reduction in whole body insulin sensitivity. Timm44 is upregulated in the kidneys of streptozotocin-induced diabetic mice. In the inner mitochondrial membrane, Timm44 anchors mitochondrial heat-shock protein 70 (mtHsp70) to the translocase of inner mitochondrial membrane 23 (TIM23) complex and facilitates the import of mitochondria-targeted preproteins into the mitochondrial matrix dependent on the inner membrane potential and ATP hydrolysis on ATPase domain of mtHsp70. METHODS We generated the aP2-promoter driven Timm44 transgenic (Tg) mouse model and investigated whether Timm44 Tg mice fed high-fat/high-sucrose (HFHS) chow are protected from type 2 diabetes and obesity. RESULTS The body weight of aP2-promoter driven Timm44 Tg mice was lower than that of wild type mice, and insulin sensitivity was greater in Timm44 Tg mice than in wild type mice. Although WAT weight was not altered in Timm44 Tg mice fed HFHS chow, adipocyte size was reduced, and mitochondrial fusion associated with decreased expression of fission genes, such as Dnm1l and Fis1, was observed. In addition, when fed standard (STD) chow, the expressions of the fusion genes Opa1, Mfn1 and Mfn2, and Mfn1 were significantly increased in Timm44 Tg mice compared to wild type mice, and fused mitochondria were also observed in Timm44 Tg mice fed STD chow. CONCLUSIONS The Timm44 gene may be a new target for the treatment of type 2 diabetes.
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Affiliation(s)
- Yu Wang
- Department of Medicine and Clinical Science, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, 2-5-1 Shikata-cho, Kita-ku, Okayama 700-8558, Japan
| | - Akihiro Katayama
- Department of Medicine and Clinical Science, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, 2-5-1 Shikata-cho, Kita-ku, Okayama 700-8558, Japan
| | - Takahiro Terami
- Department of Medicine and Clinical Science, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, 2-5-1 Shikata-cho, Kita-ku, Okayama 700-8558, Japan
| | - Xiaoying Han
- Department of Medicine and Clinical Science, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, 2-5-1 Shikata-cho, Kita-ku, Okayama 700-8558, Japan; Lady Davis Institute-Jewish General Hospital, McGill University, Montreal, Canada, H3T 1E2
| | - Tomokazu Nunoue
- Department of Medicine and Clinical Science, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, 2-5-1 Shikata-cho, Kita-ku, Okayama 700-8558, Japan
| | - Dongxiao Zhang
- Department of Medicine and Clinical Science, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, 2-5-1 Shikata-cho, Kita-ku, Okayama 700-8558, Japan
| | - Sanae Teshigawara
- Department of Medicine and Clinical Science, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, 2-5-1 Shikata-cho, Kita-ku, Okayama 700-8558, Japan
| | - Jun Eguchi
- Department of Medicine and Clinical Science, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, 2-5-1 Shikata-cho, Kita-ku, Okayama 700-8558, Japan
| | - Atsuko Nakatsuka
- Department of Medicine and Clinical Science, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, 2-5-1 Shikata-cho, Kita-ku, Okayama 700-8558, Japan
| | - Kazutoshi Murakami
- Department of General Medicine, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, 2-5-1 Shikata-cho, Kita-ku, Okayama 700-8558, Japan
| | - Daisuke Ogawa
- Department of Diabetic Nephropathy, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, 2-5-1 Shikata-cho, Kita-ku, Okayama 700-8558, Japan
| | - Yasuhide Furuta
- Laboratory for Animal Resources and Genetic Engineering, RIKEN Center for Developmental Biology, 2-2-3 Minatojima Minami, Chuou-ku, Kobe 650-0047, Japan
| | - Hirofumi Makino
- Department of Medicine and Clinical Science, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, 2-5-1 Shikata-cho, Kita-ku, Okayama 700-8558, Japan
| | - Jun Wada
- Department of Medicine and Clinical Science, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, 2-5-1 Shikata-cho, Kita-ku, Okayama 700-8558, Japan.
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Cooperation of protein machineries in mitochondrial protein sorting. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2015; 1853:1119-29. [DOI: 10.1016/j.bbamcr.2015.01.012] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/17/2014] [Revised: 01/16/2015] [Accepted: 01/20/2015] [Indexed: 02/07/2023]
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Demishtein-Zohary K, Marom M, Neupert W, Mokranjac D, Azem A. GxxxG motifs hold the TIM23 complex together. FEBS J 2015; 282:2178-86. [PMID: 25765297 DOI: 10.1111/febs.13266] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2014] [Revised: 02/28/2015] [Accepted: 03/09/2015] [Indexed: 11/30/2022]
Abstract
Approximately 99% of the mitochondrial proteome is nucleus-encoded, synthesized in the cytosol, and subsequently imported into and sorted to the correct compartment in the organelle. The translocase of the inner mitochondrial membrane 23 (TIM23) complex is the major protein translocase of the inner membrane, and is responsible for translocation of proteins across the inner membrane and their insertion into the inner membrane. Tim23 is the central component of the complex that forms the import channel. A high-resolution structure of the import channel is still missing, and structural elements important for its function are unknown. In the present study, we analyzed the importance of the highly abundant GxxxG motifs in the transmembrane segments of Tim23 for the structural integrity of the TIM23 complex. Of 10 glycines present in the GxxxG motifs in the first, second and third transmembrane segments of Tim23, mutations of three of them in transmembrane segments 1 and 2 resulted in a lethal phenotype, and mutations of three others in a temperature-sensitive phenotype. The remaining four caused no obvious growth phenotype. Importantly, none of the mutations impaired the import and membrane integration of Tim23 precursor into mitochondria. However, the severity of growth impairment correlated with the destabilization of the TIM23 complex. We conclude that the GxxxG motifs found in the first and second transmembrane segments of Tim23 are necessary for the structural integrity of the TIM23 complex.
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Affiliation(s)
- Keren Demishtein-Zohary
- Department of Biochemistry and Molecular Biology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Israel
| | - Milit Marom
- Department of Biochemistry and Molecular Biology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Israel
| | | | - Dejana Mokranjac
- Institute for Physiological Chemistry, University of Munich, Munich, Germany
| | - Abdussalam Azem
- Department of Biochemistry and Molecular Biology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Israel
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40
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A Perspective on Transport of Proteins into Mitochondria: A Myriad of Open Questions. J Mol Biol 2015; 427:1135-58. [DOI: 10.1016/j.jmb.2015.02.001] [Citation(s) in RCA: 91] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2014] [Revised: 01/30/2015] [Accepted: 02/02/2015] [Indexed: 11/22/2022]
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41
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Horvath SE, Rampelt H, Oeljeklaus S, Warscheid B, van der Laan M, Pfanner N. Role of membrane contact sites in protein import into mitochondria. Protein Sci 2015; 24:277-97. [PMID: 25514890 DOI: 10.1002/pro.2625] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2014] [Accepted: 12/08/2014] [Indexed: 12/13/2022]
Abstract
Mitochondria import more than 1,000 different proteins from the cytosol. The proteins are synthesized as precursors on cytosolic ribosomes and are translocated by protein transport machineries of the mitochondrial membranes. Five main pathways for protein import into mitochondria have been identified. Most pathways use the translocase of the outer mitochondrial membrane (TOM) as the entry gate into mitochondria. Depending on specific signals contained in the precursors, the proteins are subsequently transferred to different intramitochondrial translocases. In this article, we discuss the connection between protein import and mitochondrial membrane architecture. Mitochondria possess two membranes. It is a long-standing question how contact sites between outer and inner membranes are formed and which role the contact sites play in the translocation of precursor proteins. A major translocation contact site is formed between the TOM complex and the presequence translocase of the inner membrane (TIM23 complex), promoting transfer of presequence-carrying preproteins to the mitochondrial inner membrane and matrix. Recent findings led to the identification of contact sites that involve the mitochondrial contact site and cristae organizing system (MICOS) of the inner membrane. MICOS plays a dual role. It is crucial for maintaining the inner membrane cristae architecture and forms contacts sites to the outer membrane that promote translocation of precursor proteins into the intermembrane space and outer membrane of mitochondria. The view is emerging that the mitochondrial protein translocases do not function as independent units, but are embedded in a network of interactions with machineries that control mitochondrial activity and architecture.
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Affiliation(s)
- Susanne E Horvath
- Institut für Biochemie und Molekularbiologie, ZBMZ, Universität Freiburg, 79104, Freiburg, Germany
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42
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Verner Z, Basu S, Benz C, Dixit S, Dobáková E, Faktorová D, Hashimi H, Horáková E, Huang Z, Paris Z, Peña-Diaz P, Ridlon L, Týč J, Wildridge D, Zíková A, Lukeš J. Malleable mitochondrion of Trypanosoma brucei. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2015; 315:73-151. [PMID: 25708462 DOI: 10.1016/bs.ircmb.2014.11.001] [Citation(s) in RCA: 76] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The importance of mitochondria for a typical aerobic eukaryotic cell is undeniable, as the list of necessary mitochondrial processes is steadily growing. Here, we summarize the current knowledge of mitochondrial biology of an early-branching parasitic protist, Trypanosoma brucei, a causative agent of serious human and cattle diseases. We present a comprehensive survey of its mitochondrial pathways including kinetoplast DNA replication and maintenance, gene expression, protein and metabolite import, major metabolic pathways, Fe-S cluster synthesis, ion homeostasis, organellar dynamics, and other processes. As we describe in this chapter, the single mitochondrion of T. brucei is everything but simple and as such rivals mitochondria of multicellular organisms.
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Affiliation(s)
- Zdeněk Verner
- Institute of Parasitology, Biology Centre, Czech Academy of Sciences, Czech Republic; Present address: Faculty of Natural Sciences, Comenius University, Bratislava, Slovakia; Present address: Faculty of Sciences, Charles University, Prague, Czech Republic
| | - Somsuvro Basu
- Institute of Parasitology, Biology Centre, Czech Academy of Sciences, Czech Republic; Faculty of Sciences, University of South Bohemia, České Budějovice (Budweis), Czech Republic; Present address: Institut für Zytobiologie und Zytopathologie, Philipps-Universität Marburg, Germany
| | - Corinna Benz
- Faculty of Sciences, University of South Bohemia, České Budějovice (Budweis), Czech Republic
| | - Sameer Dixit
- Faculty of Sciences, University of South Bohemia, České Budějovice (Budweis), Czech Republic
| | - Eva Dobáková
- Institute of Parasitology, Biology Centre, Czech Academy of Sciences, Czech Republic; Present address: Faculty of Natural Sciences, Comenius University, Bratislava, Slovakia
| | - Drahomíra Faktorová
- Institute of Parasitology, Biology Centre, Czech Academy of Sciences, Czech Republic; Faculty of Sciences, University of South Bohemia, České Budějovice (Budweis), Czech Republic
| | - Hassan Hashimi
- Institute of Parasitology, Biology Centre, Czech Academy of Sciences, Czech Republic; Faculty of Sciences, University of South Bohemia, České Budějovice (Budweis), Czech Republic
| | - Eva Horáková
- Institute of Parasitology, Biology Centre, Czech Academy of Sciences, Czech Republic
| | - Zhenqiu Huang
- Institute of Parasitology, Biology Centre, Czech Academy of Sciences, Czech Republic; Faculty of Sciences, University of South Bohemia, České Budějovice (Budweis), Czech Republic
| | - Zdeněk Paris
- Institute of Parasitology, Biology Centre, Czech Academy of Sciences, Czech Republic
| | - Priscila Peña-Diaz
- Institute of Parasitology, Biology Centre, Czech Academy of Sciences, Czech Republic
| | - Lucie Ridlon
- Faculty of Sciences, University of South Bohemia, České Budějovice (Budweis), Czech Republic; Present address: Salk Institute, La Jolla, San Diego, USA
| | - Jiří Týč
- Institute of Parasitology, Biology Centre, Czech Academy of Sciences, Czech Republic; Faculty of Sciences, University of South Bohemia, České Budějovice (Budweis), Czech Republic
| | - David Wildridge
- Institute of Parasitology, Biology Centre, Czech Academy of Sciences, Czech Republic
| | - Alena Zíková
- Institute of Parasitology, Biology Centre, Czech Academy of Sciences, Czech Republic; Faculty of Sciences, University of South Bohemia, České Budějovice (Budweis), Czech Republic
| | - Julius Lukeš
- Institute of Parasitology, Biology Centre, Czech Academy of Sciences, Czech Republic; Faculty of Sciences, University of South Bohemia, České Budějovice (Budweis), Czech Republic
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43
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Mgr2 functions as lateral gatekeeper for preprotein sorting in the mitochondrial inner membrane. Mol Cell 2014; 56:641-52. [PMID: 25454944 DOI: 10.1016/j.molcel.2014.10.010] [Citation(s) in RCA: 65] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2014] [Revised: 08/14/2014] [Accepted: 10/09/2014] [Indexed: 11/21/2022]
Abstract
The majority of preproteins destined for mitochondria carry N-terminal presequences. The presequence translocase of the inner mitochondrial membrane (TIM23 complex) plays a central role in protein sorting. Preproteins are either translocated through the TIM23 complex into the matrix or are laterally released into the inner membrane. We report that the small hydrophobic protein Mgr2 controls the lateral release of preproteins. Mgr2 interacts with preproteins in transit through the TIM23 complex. Overexpression of Mgr2 delays preprotein release, whereas a lack of Mgr2 promotes preprotein sorting into the inner membrane. Preproteins with a defective inner membrane sorting signal are translocated into the matrix in wild-type mitochondria but are released into the inner membrane in Mgr2-deficient mitochondria. We conclude that Mgr2 functions as a lateral gatekeeper of the mitochondrial presequence translocase, providing quality control for the membrane sorting of preproteins.
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44
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Höhr AIC, Straub SP, Warscheid B, Becker T, Wiedemann N. Assembly of β-barrel proteins in the mitochondrial outer membrane. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2014; 1853:74-88. [PMID: 25305573 DOI: 10.1016/j.bbamcr.2014.10.006] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/21/2014] [Revised: 09/25/2014] [Accepted: 10/01/2014] [Indexed: 12/15/2022]
Abstract
Mitochondria evolved through endosymbiosis of a Gram-negative progenitor with a host cell to generate eukaryotes. Therefore, the outer membrane of mitochondria and Gram-negative bacteria contain pore proteins with β-barrel topology. After synthesis in the cytosol, β-barrel precursor proteins are first transported into the mitochondrial intermembrane space. Folding and membrane integration of β-barrel proteins depend on the mitochondrial sorting and assembly machinery (SAM) located in the outer membrane, which is related to the β-barrel assembly machinery (BAM) in bacteria. The SAM complex recognizes β-barrel proteins by a β-signal in the C-terminal β-strand that is required to initiate β-barrel protein insertion into the outer membrane. In addition, the SAM complex is crucial to form membrane contacts with the inner mitochondrial membrane by interacting with the mitochondrial contact site and cristae organizing system (MICOS) and shares a subunit with the endoplasmic reticulum-mitochondria encounter structure (ERMES) that links the outer mitochondrial membrane to the endoplasmic reticulum (ER).
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Affiliation(s)
- Alexandra I C Höhr
- Institut für Biochemie und Molekularbiologie, ZBMZ, Universität Freiburg, 79104 Freiburg, Germany; Fakultät für Biologie, Universität Freiburg, 79104 Freiburg, Germany
| | - Sebastian P Straub
- Institut für Biochemie und Molekularbiologie, ZBMZ, Universität Freiburg, 79104 Freiburg, Germany; Fakultät für Biologie, Universität Freiburg, 79104 Freiburg, Germany
| | - Bettina Warscheid
- BIOSS Centre for Biological Signalling Studies, Universität Freiburg, 79104 Freiburg, Germany; Abteilung Biochemie und Funktionelle Proteomik, Institut für Biologie II, Fakultät für Biologie, Universität Freiburg, 79104 Freiburg, Germany
| | - Thomas Becker
- Institut für Biochemie und Molekularbiologie, ZBMZ, Universität Freiburg, 79104 Freiburg, Germany; BIOSS Centre for Biological Signalling Studies, Universität Freiburg, 79104 Freiburg, Germany
| | - Nils Wiedemann
- Institut für Biochemie und Molekularbiologie, ZBMZ, Universität Freiburg, 79104 Freiburg, Germany; BIOSS Centre for Biological Signalling Studies, Universität Freiburg, 79104 Freiburg, Germany.
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45
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Waegemann K, Popov-Čeleketić D, Neupert W, Azem A, Mokranjac D. Cooperation of TOM and TIM23 complexes during translocation of proteins into mitochondria. J Mol Biol 2014; 427:1075-84. [PMID: 25083920 DOI: 10.1016/j.jmb.2014.07.015] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2014] [Revised: 07/14/2014] [Accepted: 07/22/2014] [Indexed: 01/07/2023]
Abstract
Translocation of the majority of mitochondrial proteins from the cytosol into mitochondria requires the cooperation of TOM and TIM23 complexes in the outer and inner mitochondrial membranes. The molecular mechanisms underlying this cooperation remain largely unknown. Here, we present biochemical and genetic evidence that at least two contacts from the side of the TIM23 complex play an important role in TOM-TIM23 cooperation in vivo. Tim50, likely through its very C-terminal segment, interacts with Tom22. This interaction is stimulated by translocating proteins and is independent of any other TOM-TIM23 contact known so far. Furthermore, the exposure of Tim23 on the mitochondrial surface depends not only on its interaction with Tim50 but also on the dynamics of the TOM complex. Destabilization of the individual contacts reduces the efficiency of import of proteins into mitochondria and destabilization of both contacts simultaneously is not tolerated by yeast cells. We conclude that an intricate and coordinated network of protein-protein interactions involving primarily Tim50 and also Tim23 is required for efficient translocation of proteins across both mitochondrial membranes.
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Affiliation(s)
- Karin Waegemann
- Department of Physiological Chemistry, Medical Faculty, University of Munich, Butenandtstrasse 5, 81377 Munich, Germany
| | - Dušan Popov-Čeleketić
- Department of Physiological Chemistry, Medical Faculty, University of Munich, Butenandtstrasse 5, 81377 Munich, Germany
| | - Walter Neupert
- Max Planck Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany
| | - Abdussalam Azem
- Department of Biochemistry and Molecular Biology, George S. Wise Faculty of Life Sciences, Tel Aviv University, 69978 Tel Aviv, Israel
| | - Dejana Mokranjac
- Department of Physiological Chemistry, Medical Faculty, University of Munich, Butenandtstrasse 5, 81377 Munich, Germany.
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46
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Woellhaf MW, Hansen KG, Garth C, Herrmann JM. Import of ribosomal proteins into yeast mitochondria. Biochem Cell Biol 2014; 92:489-98. [PMID: 24943357 DOI: 10.1139/bcb-2014-0029] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Mitochondrial ribosomes of baker's yeast contain at least 78 protein subunits. All but one of these proteins are nuclear-encoded, synthesized on cytosolic ribosomes, and imported into the matrix for biogenesis. The import of matrix proteins typically relies on N-terminal mitochondrial targeting sequences that form positively charged amphipathic helices. Interestingly, the N-terminal regions of many ribosomal proteins do not closely match the characteristics of matrix targeting sequences, suggesting that the import processes of these proteins might deviate to some extent from the general import route. So far, the biogenesis of only two ribosomal proteins, Mrpl32 and Mrp10, was studied experimentally and indeed showed surprising differences to the import of other preproteins. In this review article we summarize the current knowledge on the transport of proteins into the mitochondrial matrix, and thereby specifically focus on proteins of the mitochondrial ribosome.
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Affiliation(s)
- Michael W Woellhaf
- a Cell Biology, University of Kaiserslautern, Erwin-Schrödinger-Strasse 13, 67663 Kaiserslautern, Germany
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47
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Wenz LS, Opaliński L, Schuler MH, Ellenrieder L, Ieva R, Böttinger L, Qiu J, van der Laan M, Wiedemann N, Guiard B, Pfanner N, Becker T. The presequence pathway is involved in protein sorting to the mitochondrial outer membrane. EMBO Rep 2014; 15:678-85. [PMID: 24781695 DOI: 10.1002/embr.201338144] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
The mitochondrial outer membrane contains integral α-helical and β-barrel proteins that are imported from the cytosol. The machineries importing β-barrel proteins have been identified, however, different views exist on the import of α-helical proteins. It has been reported that the biogenesis of Om45, the most abundant signal-anchored protein, does not depend on proteinaceous components, but involves direct insertion into the outer membrane. We show that import of Om45 occurs via the translocase of the outer membrane and the presequence translocase of the inner membrane. Assembly of Om45 in the outer membrane involves the MIM machinery. Om45 thus follows a new mitochondrial biogenesis pathway that uses elements of the presequence import pathway to direct a protein to the outer membrane.
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Affiliation(s)
- Lena-Sophie Wenz
- Institut für Biochemie und Molekularbiologie, ZBMZ Universität Freiburg, Freiburg, Germany Faculty of Biology, Universität Freiburg, Freiburg, Germany
| | - Lukasz Opaliński
- Institut für Biochemie und Molekularbiologie, ZBMZ Universität Freiburg, Freiburg, Germany
| | - Max-Hinderk Schuler
- Institut für Biochemie und Molekularbiologie, ZBMZ Universität Freiburg, Freiburg, Germany
| | - Lars Ellenrieder
- Institut für Biochemie und Molekularbiologie, ZBMZ Universität Freiburg, Freiburg, Germany Faculty of Biology, Universität Freiburg, Freiburg, Germany
| | - Raffaele Ieva
- Institut für Biochemie und Molekularbiologie, ZBMZ Universität Freiburg, Freiburg, Germany
| | - Lena Böttinger
- Institut für Biochemie und Molekularbiologie, ZBMZ Universität Freiburg, Freiburg, Germany Faculty of Biology, Universität Freiburg, Freiburg, Germany
| | - Jian Qiu
- Institut für Biochemie und Molekularbiologie, ZBMZ Universität Freiburg, Freiburg, Germany Spemann Graduate School of Biology and Medicine, Universität Freiburg, Freiburg, Germany
| | - Martin van der Laan
- Institut für Biochemie und Molekularbiologie, ZBMZ Universität Freiburg, Freiburg, Germany BIOSS Centre for Biological Signalling Studies, Universität Freiburg, Freiburg, Germany
| | - Nils Wiedemann
- Institut für Biochemie und Molekularbiologie, ZBMZ Universität Freiburg, Freiburg, Germany BIOSS Centre for Biological Signalling Studies, Universität Freiburg, Freiburg, Germany
| | - Bernard Guiard
- Centre de Génétique Moléculaire, CNRS, Gif-sur-Yvette, France
| | - Nikolaus Pfanner
- Institut für Biochemie und Molekularbiologie, ZBMZ Universität Freiburg, Freiburg, Germany BIOSS Centre for Biological Signalling Studies, Universität Freiburg, Freiburg, Germany
| | - Thomas Becker
- Institut für Biochemie und Molekularbiologie, ZBMZ Universität Freiburg, Freiburg, Germany BIOSS Centre for Biological Signalling Studies, Universität Freiburg, Freiburg, Germany
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48
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van der Laan M, Schrempp SG, Pfanner N. Voltage-coupled conformational dynamics of mitochondrial protein-import channel. Nat Struct Mol Biol 2013; 20:915-7. [DOI: 10.1038/nsmb.2643] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
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49
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Abstract
The mitochondrion is arguably the most complex organelle in the budding yeast cell cytoplasm. It is essential for viability as well as respiratory growth. Its innermost aqueous compartment, the matrix, is bounded by the highly structured inner membrane, which in turn is bounded by the intermembrane space and the outer membrane. Approximately 1000 proteins are present in these organelles, of which eight major constituents are coded and synthesized in the matrix. The import of mitochondrial proteins synthesized in the cytoplasm, and their direction to the correct soluble compartments, correct membranes, and correct membrane surfaces/topologies, involves multiple pathways and macromolecular machines. The targeting of some, but not all, cytoplasmically synthesized mitochondrial proteins begins with translation of messenger RNAs localized to the organelle. Most proteins then pass through the translocase of the outer membrane to the intermembrane space, where divergent pathways sort them to the outer membrane, inner membrane, and matrix or trap them in the intermembrane space. Roughly 25% of mitochondrial proteins participate in maintenance or expression of the organellar genome at the inner surface of the inner membrane, providing 7 membrane proteins whose synthesis nucleates the assembly of three respiratory complexes.
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50
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Lytovchenko O, Melin J, Schulz C, Kilisch M, Hutu DP, Rehling P. Signal recognition initiates reorganization of the presequence translocase during protein import. EMBO J 2013; 32:886-98. [PMID: 23403928 DOI: 10.1038/emboj.2013.23] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2012] [Accepted: 01/17/2013] [Indexed: 11/09/2022] Open
Abstract
The mitochondrial presequence translocase interacts with presequence-containing precursors at the intermembrane space (IMS) side of the inner membrane to mediate their translocation into the matrix. Little is known as too how these matrix-targeting signals activate the translocase in order to initiate precursor transport. Therefore, we analysed how signal recognition by the presequence translocase initiates reorganization among Tim-proteins during import. Our analyses revealed that the presequence receptor Tim50 interacts with Tim21 in a signal-sensitive manner in a process that involves the IMS-domain of the Tim23 channel. The signal-driven release of Tim21 from Tim50 promotes recruitment of Pam17 and thus triggers formation of the motor-associated form of the TIM23 complex required for matrix transport.
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