1
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Maruszczak KK, Draczkowski P, Wnorowski A, Chacinska A. Structure prediction analysis of human core TIM23 complex reveals conservation of the protein translocation mechanism. FEBS Open Bio 2024. [PMID: 38837610 DOI: 10.1002/2211-5463.13840] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2024] [Revised: 05/21/2024] [Accepted: 05/27/2024] [Indexed: 06/07/2024] Open
Abstract
The majority of mitochondrial proteins are encoded in the nucleus, translated on cytosolic ribosomes, and subsequently targeted to the mitochondrial surface. Their further import into the organelle is facilitated by highly specialized protein translocases. Mitochondrial precursor proteins that are destined to the mitochondrial matrix and, to some extent, the inner membrane, utilize translocase of the inner membrane (TIM23). This indispensable import machinery has been extensively studied in yeast. The translocating unit of the TIM23 complex in yeast consists of two membrane proteins, Tim17 and Tim23. In contrast to previous findings, recent reports demonstrate the primary role of Tim17, rather than Tim23, in the translocation of newly synthesized proteins. Very little is known about human TIM23 translocase. Human cells have two orthologs of yeast Tim17, TIMM17A and TIMM17B. Here, using computational tools, we present the architecture of human core TIM23 variants with either TIMM17A or TIMM17B, forming two populations of highly similar complexes. The structures reveal high conservation of the core TIM23 complex between human and yeast. Interestingly, both TIMM17A and TIMM17B variants interact with TIMM23 and reactive oxygen species modulator 1 (ROMO1); a homolog of yeast Mgr2, a protein that can create a channel-like structure with Tim17. The high structural conservation of proteins that form the core TIM23 complex in yeast and humans raises an interesting question about mechanistic and functional differences that justify existence of the two variants of TIM23 in higher eukaryotes.
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Affiliation(s)
| | - Piotr Draczkowski
- National Bioinformatics Infrastructure Sweden, SciLifeLab, Solna, Sweden
- Department of Synthesis and Chemical Technology of Pharmaceutical Substances, Medical University of Lublin, Poland
| | - Artur Wnorowski
- Department of Biopharmacy, Medical University of Lublin, Poland
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2
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Makki A, Kereïche S, Le T, Kučerová J, Rada P, Žárský V, Hrdý I, Tachezy J. A hybrid TIM complex mediates protein import into hydrogenosomes of Trichomonas vaginalis. BMC Biol 2024; 22:130. [PMID: 38825681 PMCID: PMC11145794 DOI: 10.1186/s12915-024-01928-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2023] [Accepted: 05/22/2024] [Indexed: 06/04/2024] Open
Abstract
BACKGROUND Hydrogenosomes are a specific type of mitochondria that have adapted for life under anaerobiosis. Limited availability of oxygen has resulted in the loss of the membrane-associated respiratory chain, and consequently in the generation of minimal inner membrane potential (Δψ), and inefficient ATP synthesis via substrate-level phosphorylation. The changes in energy metabolism are directly linked with the organelle biogenesis. In mitochondria, proteins are imported across the outer membrane via the Translocase of the Outer Membrane (TOM complex), while two Translocases of the Inner Membrane, TIM22, and TIM23, facilitate import to the inner membrane and matrix. TIM23-mediated steps are entirely dependent on Δψ and ATP hydrolysis, while TIM22 requires only Δψ. The character of the hydrogenosomal inner membrane translocase and the mechanism of translocation is currently unknown. RESULTS We report unprecedented modification of TIM in hydrogenosomes of the human parasite Trichomonas vaginalis (TvTIM). We show that the import of the presequence-containing protein into the hydrogenosomal matrix is mediated by the hybrid TIM22-TIM23 complex that includes three highly divergent core components, TvTim22, TvTim23, and TvTim17-like proteins. The hybrid character of the TvTIM is underlined by the presence of both TvTim22 and TvTim17/23, association with small Tim chaperones (Tim9-10), which in mitochondria are known to facilitate the transfer of substrates to the TIM22 complex, and the coupling with TIM23-specific ATP-dependent presequence translocase-associated motor (PAM). Interactome reconstruction based on co-immunoprecipitation (coIP) and mass spectrometry revealed that hybrid TvTIM is formed with the compositional variations of paralogs. Single-particle electron microscopy for the 132-kDa purified TvTIM revealed the presence of a single ring of small Tims complex, while mitochondrial TIM22 complex bears twin small Tims hexamer. TvTIM is currently the only TIM visualized outside of Opisthokonta, which raised the question of which form is prevailing across eukaryotes. The tight association of the hybrid TvTIM with ADP/ATP carriers (AAC) suggests that AAC may directly supply ATP for the protein import since ATP synthesis is limited in hydrogenosomes. CONCLUSIONS The hybrid TvTIM in hydrogenosomes represents an original structural solution that evolved for protein import when Δψ is negligible and remarkable example of evolutionary adaptation to an anaerobic lifestyle.
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Affiliation(s)
- Abhijith Makki
- Department of Parasitology, Faculty of Science, Charles University, BIOCEV, Průmyslová 595, 25250, Vestec, Czech Republic
- Present address: Department of Cellular Biochemistry, University Medical Center Göttingen, D-37073, Göttingen, Germany
| | - Sami Kereïche
- Institute of Biology and Medical Genetics, First Faculty of Medicine, Charles University, Albertov 4, 12800, Prague 2, Czech Republic
| | - Tien Le
- Department of Parasitology, Faculty of Science, Charles University, BIOCEV, Průmyslová 595, 25250, Vestec, Czech Republic
| | - Jitka Kučerová
- Department of Parasitology, Faculty of Science, Charles University, BIOCEV, Průmyslová 595, 25250, Vestec, Czech Republic
| | - Petr Rada
- Department of Parasitology, Faculty of Science, Charles University, BIOCEV, Průmyslová 595, 25250, Vestec, Czech Republic
| | - Vojtěch Žárský
- Department of Biology and Ecology, Faculty of Science, University of Ostrava, Ostrava, Czech Republic
| | - Ivan Hrdý
- Department of Parasitology, Faculty of Science, Charles University, BIOCEV, Průmyslová 595, 25250, Vestec, Czech Republic
| | - Jan Tachezy
- Department of Parasitology, Faculty of Science, Charles University, BIOCEV, Průmyslová 595, 25250, Vestec, Czech Republic.
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3
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Paz E, Jain S, Gottfried I, Staretz-Chacham O, Mahajnah M, Bagchi P, Seyfried NT, Ashery U, Azem A. Biochemical and neurophysiological effects of deficiency of the mitochondrial import protein TIMM50. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.05.20.594480. [PMID: 38826427 PMCID: PMC11142075 DOI: 10.1101/2024.05.20.594480] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2024]
Abstract
TIMM50, an essential TIM23 complex subunit, is suggested to facilitate the import of ∼60% of the mitochondrial proteome. In this study, we characterized a TIMM50 disease causing mutation in human fibroblasts, and noted significant decreases in TIM23 core protein levels (TIMM50, TIMM17A/B, and TIMM23). Strikingly, TIMM50 deficiency had no impact on the steady state levels of most of its substrates, challenging the currently accepted import dogma of the essential general import role of TIM23 and suggesting that fully functioning TIM23 complex is not essential for maintaining the steady state level of the majority of mitochondrial proteins. As TIMM50 mutations have been linked to severe neurological phenotypes, we aimed to characterize TIMM50 defects in manipulated mammalian neurons. TIMM50 knockdown in mouse neurons had a minor effect on the steady state level of most of the mitochondrial proteome, supporting the results observed in patient fibroblasts. Amongst the few affected TIM23 substrates, a decrease in the steady state level of components of the intricate oxidative phosphorylation and mitochondrial ribosome complexes was evident. This led to declined respiration rates in fibroblasts and neurons, reduced cellular ATP levels and defective mitochondrial trafficking in neuronal processes, possibly contributing to the developmental defects observed in patients with TIMM50 disease. Finally, increased electrical activity was observed in TIMM50 deficient mice neuronal cells, which correlated with reduced levels of KCNJ10 and KCNA2 plasma membrane potassium channels, likely underlying the patients' epileptic phenotype.
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Eldeeb MA, Bayne AN, Fallahi A, Goiran T, MacDougall EJ, Soumbasis A, Zorca CE, Tabah JJ, Thomas RA, Karpilovsky N, Mathur M, Durcan TM, Trempe JF, Fon EA. Tom20 gates PINK1 activity and mediates its tethering of the TOM and TIM23 translocases upon mitochondrial stress. Proc Natl Acad Sci U S A 2024; 121:e2313540121. [PMID: 38416681 DOI: 10.1073/pnas.2313540121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2023] [Accepted: 01/08/2024] [Indexed: 03/01/2024] Open
Abstract
Mutations in PTEN-induced putative kinase 1 (PINK1) cause autosomal recessive early-onset Parkinson's disease (PD). PINK1 is a Ser/Thr kinase that regulates mitochondrial quality control by triggering mitophagy mediated by the ubiquitin (Ub) ligase Parkin. Upon mitochondrial damage, PINK1 accumulates on the outer mitochondrial membrane forming a high-molecular-weight complex with the translocase of the outer membrane (TOM). PINK1 then phosphorylates Ub, which enables recruitment and activation of Parkin followed by autophagic clearance of the damaged mitochondrion. Thus, Parkin-dependent mitophagy hinges on the stable accumulation of PINK1 on the TOM complex. Yet, the mechanism linking mitochondrial stressors to PINK1 accumulation and whether the translocases of the inner membrane (TIMs) are also involved remain unclear. Herein, we demonstrate that mitochondrial stress induces the formation of a PINK1-TOM-TIM23 supercomplex in human cultured cell lines, dopamine neurons, and midbrain organoids. Moreover, we show that PINK1 is required to stably tether the TOM to TIM23 complexes in response to stress such that the supercomplex fails to accumulate in cells lacking PINK1. This tethering is dependent on an interaction between the PINK1 N-terminal-C-terminal extension module and the cytosolic domain of the Tom20 subunit of the TOM complex, the disruption of which, by either designer or PD-associated PINK1 mutations, inhibits downstream mitophagy. Together, the findings provide key insight into how PINK1 interfaces with the mitochondrial import machinery, with important implications for the mechanisms of mitochondrial quality control and PD pathogenesis.
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Affiliation(s)
- Mohamed A Eldeeb
- McGill Parkinson Program and Neurodegenerative Disorders Research Group, Department of Neurology and Neurosurgery, Montreal Neurological Institute-Hospital, McGill University, Montréal, QC H3A 2B4, Canada
- Structural Genomics Consortium - Neuro, McGill University, Montréal, QC H3A 2B4, Canada
| | - Andrew N Bayne
- Structural Genomics Consortium - Neuro, McGill University, Montréal, QC H3A 2B4, Canada
- Department of Pharmacology and Therapeutics, McGill University, Montréal, QC H3G 1Y6, Canada
- Centre de Recherche en Biologie Structurale, Montréal, QC H3G 0B1, Canada
| | - Armaan Fallahi
- McGill Parkinson Program and Neurodegenerative Disorders Research Group, Department of Neurology and Neurosurgery, Montreal Neurological Institute-Hospital, McGill University, Montréal, QC H3A 2B4, Canada
- Structural Genomics Consortium - Neuro, McGill University, Montréal, QC H3A 2B4, Canada
| | - Thomas Goiran
- McGill Parkinson Program and Neurodegenerative Disorders Research Group, Department of Neurology and Neurosurgery, Montreal Neurological Institute-Hospital, McGill University, Montréal, QC H3A 2B4, Canada
- Structural Genomics Consortium - Neuro, McGill University, Montréal, QC H3A 2B4, Canada
| | - Emma J MacDougall
- McGill Parkinson Program and Neurodegenerative Disorders Research Group, Department of Neurology and Neurosurgery, Montreal Neurological Institute-Hospital, McGill University, Montréal, QC H3A 2B4, Canada
- Structural Genomics Consortium - Neuro, McGill University, Montréal, QC H3A 2B4, Canada
| | - Andrea Soumbasis
- McGill Parkinson Program and Neurodegenerative Disorders Research Group, Department of Neurology and Neurosurgery, Montreal Neurological Institute-Hospital, McGill University, Montréal, QC H3A 2B4, Canada
- Structural Genomics Consortium - Neuro, McGill University, Montréal, QC H3A 2B4, Canada
| | - Cornelia E Zorca
- McGill Parkinson Program and Neurodegenerative Disorders Research Group, Department of Neurology and Neurosurgery, Montreal Neurological Institute-Hospital, McGill University, Montréal, QC H3A 2B4, Canada
- Structural Genomics Consortium - Neuro, McGill University, Montréal, QC H3A 2B4, Canada
| | - Jace-Jones Tabah
- McGill Parkinson Program and Neurodegenerative Disorders Research Group, Department of Neurology and Neurosurgery, Montreal Neurological Institute-Hospital, McGill University, Montréal, QC H3A 2B4, Canada
- Structural Genomics Consortium - Neuro, McGill University, Montréal, QC H3A 2B4, Canada
| | - Rhalena A Thomas
- McGill Parkinson Program and Neurodegenerative Disorders Research Group, Department of Neurology and Neurosurgery, Montreal Neurological Institute-Hospital, McGill University, Montréal, QC H3A 2B4, Canada
- Structural Genomics Consortium - Neuro, McGill University, Montréal, QC H3A 2B4, Canada
| | - Nathan Karpilovsky
- McGill Parkinson Program and Neurodegenerative Disorders Research Group, Department of Neurology and Neurosurgery, Montreal Neurological Institute-Hospital, McGill University, Montréal, QC H3A 2B4, Canada
- Structural Genomics Consortium - Neuro, McGill University, Montréal, QC H3A 2B4, Canada
| | - Meghna Mathur
- McGill Parkinson Program and Neurodegenerative Disorders Research Group, Department of Neurology and Neurosurgery, Montreal Neurological Institute-Hospital, McGill University, Montréal, QC H3A 2B4, Canada
- Structural Genomics Consortium - Neuro, McGill University, Montréal, QC H3A 2B4, Canada
| | - Thomas M Durcan
- McGill Parkinson Program and Neurodegenerative Disorders Research Group, Department of Neurology and Neurosurgery, Montreal Neurological Institute-Hospital, McGill University, Montréal, QC H3A 2B4, Canada
- Structural Genomics Consortium - Neuro, McGill University, Montréal, QC H3A 2B4, Canada
| | - Jean-François Trempe
- Structural Genomics Consortium - Neuro, McGill University, Montréal, QC H3A 2B4, Canada
- Department of Pharmacology and Therapeutics, McGill University, Montréal, QC H3G 1Y6, Canada
- Centre de Recherche en Biologie Structurale, Montréal, QC H3G 0B1, Canada
| | - Edward A Fon
- McGill Parkinson Program and Neurodegenerative Disorders Research Group, Department of Neurology and Neurosurgery, Montreal Neurological Institute-Hospital, McGill University, Montréal, QC H3A 2B4, Canada
- Structural Genomics Consortium - Neuro, McGill University, Montréal, QC H3A 2B4, Canada
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5
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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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6
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Wasilewski M, Draczkowski P, Chacinska A. Protein import into mitochondria - a new path through the membranes. Nat Struct Mol Biol 2023; 30:1831-1833. [PMID: 38087086 DOI: 10.1038/s41594-023-01170-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2023]
Affiliation(s)
| | - Piotr Draczkowski
- Department of Synthesis and Chemical Technology of Pharmaceutical Substances, Faculty of Pharmacy, Medical University of Lublin, Lublin, Poland
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7
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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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8
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Nieto-Panqueva F, Rubalcava-Gracia D, Hamel PP, González-Halphen D. The constraints of allotopic expression. Mitochondrion 2023; 73:30-50. [PMID: 37739243 DOI: 10.1016/j.mito.2023.09.004] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2023] [Revised: 08/28/2023] [Accepted: 09/18/2023] [Indexed: 09/24/2023]
Abstract
Allotopic expression is the functional transfer of an organellar gene to the nucleus, followed by synthesis of the gene product in the cytosol and import into the appropriate organellar sub compartment. Here, we focus on mitochondrial genes encoding OXPHOS subunits that were naturally transferred to the nucleus, and critically review experimental evidence that claim their allotopic expression. We emphasize aspects that may have been overlooked before, i.e., when modifying a mitochondrial gene for allotopic expression━besides adapting the codon usage and including sequences encoding mitochondrial targeting signals━three additional constraints should be considered: (i) the average apparent free energy of membrane insertion (μΔGapp) of the transmembrane stretches (TMS) in proteins earmarked for the inner mitochondrial membrane, (ii) the final, functional topology attained by each membrane-bound OXPHOS subunit; and (iii) the defined mechanism by which the protein translocator TIM23 sorts cytosol-synthesized precursors. The mechanistic constraints imposed by TIM23 dictate the operation of two pathways through which alpha-helices in TMS are sorted, that eventually determine the final topology of membrane proteins. We used the biological hydrophobicity scale to assign an average apparent free energy of membrane insertion (μΔGapp) and a "traffic light" color code to all TMS of OXPHOS membrane proteins, thereby predicting which are more likely to be internalized into mitochondria if allotopically produced. We propose that the design of proteins for allotopic expression must make allowance for μΔGapp maximization of highly hydrophobic TMS in polypeptides whose corresponding genes have not been transferred to the nucleus in some organisms.
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Affiliation(s)
- Felipe Nieto-Panqueva
- Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico City, Mexico
| | - Diana Rubalcava-Gracia
- Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico City, Mexico; Division of Molecular Metabolism, Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm, Sweden
| | - Patrice P Hamel
- Department of Molecular Genetics and Department of Biological Chemistry and Pharmacology, Ohio State University, Columbus, OH, USA; Vellore Institute of Technology (VIT), School of BioScience and Technology, Vellore, Tamil Nadu, India
| | - Diego González-Halphen
- Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico City, Mexico.
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9
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Wen Y, Wu K, Chai B, Fang Y, Hu P, Tan Y, Wang Y, Wu H, Wang J, Zhu L, Zhang G, Gao Z, Ren D, Zeng D, Shen L, Dong G, Zhang Q, Li Q, Qian Q, Hu J. NLG1, encoding a mitochondrial membrane protein, controls leaf and grain development in rice. BMC PLANT BIOLOGY 2023; 23:418. [PMID: 37689677 PMCID: PMC10492415 DOI: 10.1186/s12870-023-04417-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/21/2023] [Accepted: 08/22/2023] [Indexed: 09/11/2023]
Abstract
BACKGROUND Mitochondrion is the key respiratory organ and participate in multiple anabolism and catabolism pathways in eukaryote. However, the underlying mechanism of how mitochondrial membrane proteins regulate leaf and grain development remains to be further elucidated. RESULTS Here, a mitochondria-defective mutant narrow leaf and slender grain 1 (nlg1) was identified from an EMS-treated mutant population, which exhibits narrow leaves and slender grains. Moreover, nlg1 also presents abnormal mitochondria structure and was sensitive to the inhibitors of mitochondrial electron transport chain. Map-based cloning and transgenic functional confirmation revealed that NLG1 encodes a mitochondrial import inner membrane translocase containing a subunit Tim21. GUS staining assay and RT-qPCR suggested that NLG1 was mainly expressed in leaves and panicles. The expression level of respiratory function and auxin response related genes were significantly down-regulated in nlg1, which may be responsible for the declination of ATP production and auxin content. CONCLUSIONS These results suggested that NLG1 plays an important role in the regulation of leaf and grain size development by maintaining mitochondrial homeostasis. Our finding provides a novel insight into the effects of mitochondria development on leaf and grain morphogenesis in rice.
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Affiliation(s)
- Yi Wen
- Rice Research Institute of Shenyang Agricultural University/Key Laboratory of Northern Japonica Rice Genetics and Breeding, Ministry of Education and Liaoning Province, Shenyang, 110866, China
- State Key Laboratory of Rice Biology and Breeding, China National Rice Research Institute, Hangzhou, 310006, China
| | - Kaixiong Wu
- State Key Laboratory of Rice Biology and Breeding, China National Rice Research Institute, Hangzhou, 310006, China
| | - Bingze Chai
- State Key Laboratory of Rice Biology and Breeding, China National Rice Research Institute, Hangzhou, 310006, China
| | - Yunxia Fang
- College of Life and Environmental Sciences, Hangzhou Normal University, 16 Xiasha Road, Hangzhou, 310036, China
| | - Peng Hu
- State Key Laboratory of Rice Biology and Breeding, China National Rice Research Institute, Hangzhou, 310006, China
| | - Yiqing Tan
- State Key Laboratory of Rice Biology and Breeding, China National Rice Research Institute, Hangzhou, 310006, China
| | - Yueying Wang
- State Key Laboratory of Rice Biology and Breeding, China National Rice Research Institute, Hangzhou, 310006, China
| | - Hao Wu
- State Key Laboratory of Rice Biology and Breeding, China National Rice Research Institute, Hangzhou, 310006, China
| | - Junge Wang
- State Key Laboratory of Rice Biology and Breeding, China National Rice Research Institute, Hangzhou, 310006, China
| | - Li Zhu
- State Key Laboratory of Rice Biology and Breeding, China National Rice Research Institute, Hangzhou, 310006, China
| | - Guangheng Zhang
- State Key Laboratory of Rice Biology and Breeding, China National Rice Research Institute, Hangzhou, 310006, China
| | - Zhenyu Gao
- State Key Laboratory of Rice Biology and Breeding, China National Rice Research Institute, Hangzhou, 310006, China
| | - Deyong Ren
- State Key Laboratory of Rice Biology and Breeding, China National Rice Research Institute, Hangzhou, 310006, China
| | - Dali Zeng
- State Key Laboratory of Rice Biology and Breeding, China National Rice Research Institute, Hangzhou, 310006, China
| | - Lan Shen
- State Key Laboratory of Rice Biology and Breeding, China National Rice Research Institute, Hangzhou, 310006, China
| | - Guojun Dong
- State Key Laboratory of Rice Biology and Breeding, China National Rice Research Institute, Hangzhou, 310006, China
| | - Qiang Zhang
- State Key Laboratory of Rice Biology and Breeding, China National Rice Research Institute, Hangzhou, 310006, China
| | - Qing Li
- State Key Laboratory of Rice Biology and Breeding, China National Rice Research Institute, Hangzhou, 310006, China
| | - Qian Qian
- Rice Research Institute of Shenyang Agricultural University/Key Laboratory of Northern Japonica Rice Genetics and Breeding, Ministry of Education and Liaoning Province, Shenyang, 110866, China.
- State Key Laboratory of Rice Biology and Breeding, China National Rice Research Institute, Hangzhou, 310006, China.
- Hainan Yazhou Bay Seed Laboratory, Sanya, Hainan, 572024, China.
- National Nanfan Research Institute (Sanya), Chinese Academy of Agricultural Sciences, Sanya, 572024, China.
| | - Jiang Hu
- State Key Laboratory of Rice Biology and Breeding, China National Rice Research Institute, Hangzhou, 310006, China.
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10
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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: 19] [Impact Index Per Article: 19.0] [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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11
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Fielden LF, Busch JD, Merkt SG, Ganesan I, Steiert C, Hasselblatt HB, Busto JV, Wirth C, Zufall N, Jungbluth S, Noll K, Dung JM, Butenko L, von der Malsburg K, Koch HG, Hunte C, van der Laan M, Wiedemann N. Central role of Tim17 in mitochondrial presequence protein translocation. Nature 2023; 621:627-634. [PMID: 37527780 PMCID: PMC10511324 DOI: 10.1038/s41586-023-06477-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2022] [Accepted: 07/25/2023] [Indexed: 08/03/2023]
Abstract
The presequence translocase of the mitochondrial inner membrane (TIM23) represents the major route for the import of nuclear-encoded proteins into mitochondria1,2. About 60% of more than 1,000 different mitochondrial proteins are synthesized with amino-terminal targeting signals, termed presequences, which form positively charged amphiphilic α-helices3,4. TIM23 sorts the presequence proteins into the inner membrane or matrix. Various views, including regulatory and coupling functions, have been reported on the essential TIM23 subunit Tim17 (refs. 5-7). Here we mapped the interaction of Tim17 with matrix-targeted and inner membrane-sorted preproteins during translocation in the native membrane environment. We show that Tim17 contains conserved negative charges close to the intermembrane space side of the bilayer, which are essential to initiate presequence protein translocation along a distinct transmembrane cavity of Tim17 for both classes of preproteins. The amphiphilic character of mitochondrial presequences directly matches this Tim17-dependent translocation mechanism. This mechanism permits direct lateral release of transmembrane segments of inner membrane-sorted precursors into the inner membrane.
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Affiliation(s)
- Laura F Fielden
- Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Jakob D Busch
- Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Sandra G Merkt
- Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, Freiburg, Germany
- Faculty of Biology, University of Freiburg, Freiburg, Germany
| | - Iniyan Ganesan
- Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Conny Steiert
- Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Hanna B Hasselblatt
- Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Jon V Busto
- Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Christophe Wirth
- Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Nicole Zufall
- Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Sibylle Jungbluth
- Medical Biochemistry and Molecular Biology, Center for Molecular Signaling, PZMS, Saarland University, Homburg, Germany
| | - Katja Noll
- Medical Biochemistry and Molecular Biology, Center for Molecular Signaling, PZMS, Saarland University, Homburg, Germany
| | - Julia M Dung
- Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Ludmila Butenko
- Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Karina von der Malsburg
- Medical Biochemistry and Molecular Biology, Center for Molecular Signaling, PZMS, Saarland University, Homburg, Germany
| | - Hans-Georg Koch
- Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Carola Hunte
- Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, Freiburg, Germany
- CIBSS-Centre for Integrative Biological Signalling Studies, University of Freiburg, Freiburg, Germany
- BIOSS-Centre for Biological Signalling Studies, University of Freiburg, Freiburg, Germany
| | - Martin van der Laan
- Medical Biochemistry and Molecular Biology, Center for Molecular Signaling, PZMS, Saarland University, Homburg, Germany.
| | - Nils Wiedemann
- Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, Freiburg, Germany.
- CIBSS-Centre for Integrative Biological Signalling Studies, University of Freiburg, Freiburg, Germany.
- BIOSS-Centre for Biological Signalling Studies, University of Freiburg, Freiburg, Germany.
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12
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Makki A, Rehling P. Protein transport along the presequence pathway. Biol Chem 2023; 404:807-812. [PMID: 37155927 DOI: 10.1515/hsz-2023-0133] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2023] [Accepted: 04/25/2023] [Indexed: 05/10/2023]
Abstract
Most mitochondrial proteins are nuclear-encoded and imported by the protein import machinery based on specific targeting signals. The proteins that carry an amino-terminal targeting signal (presequence) are imported via the presequence import pathway that involves the translocases of the outer and inner membranes - TOM and TIM23 complexes. In this article, we discuss how mitochondrial matrix and inner membrane precursor proteins are imported along the presequence pathway in Saccharomyces cerevisiae with a focus on the dynamics of the TIM23 complex, and further update with some of the key findings that advanced the field in the last few years.
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Affiliation(s)
- Abhijith Makki
- Department of Cellular Biochemistry, University Medical Center Göttingen, D-37073 Göttingen, Germany
| | - Peter Rehling
- Department of Cellular Biochemistry, University Medical Center Göttingen, D-37073 Göttingen, Germany
- Cluster of Excellence "Multiscale Bioimaging: from Molecular Machines to Networks of Excitable Cells" (MBExC), University of Göttingen, Göttingen, Germany
- Max Planck Institute for Multidisciplinary Sciences, D-37077 Göttingen, Germany
- Fraunhofer Institute for Translational Medicine and Pharmacology ITMP, Translational Neuroinflammation and Automated Microscopy, Göttingen, Germany
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13
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Mitochondrial protein import and UPR mt in skeletal muscle remodeling and adaptation. Semin Cell Dev Biol 2023; 143:28-36. [PMID: 35063351 DOI: 10.1016/j.semcdb.2022.01.002] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2021] [Revised: 12/20/2021] [Accepted: 01/04/2022] [Indexed: 01/03/2023]
Abstract
The biogenesis of mitochondria requires the coordinated expression of the nuclear and the mitochondrial genomes. However, the vast majority of gene products within the organelle are encoded in the nucleus, synthesized in the cytosol, and imported into mitochondria via the protein import machinery, which permit the entry of proteins to expand the mitochondrial network. Once inside, proteins undergo a maturation and folding process brought about by enzymes comprising the unfolded protein response (UPRmt). Protein import and UPRmt activity must be synchronized and matched with mtDNA-encoded subunit synthesis for proper assembly of electron transport chain complexes to avoid proteotoxicity. This review discusses the functions of the import and UPRmt systems in mammalian skeletal muscle, as well as how exercise alters the equilibrium of these pathways in a time-dependent manner, leading to a new steady state of mitochondrial content resulting in enhanced oxidative capacity and improved muscle health.
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14
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Magistrati M, Gilea AI, Gerra MC, Baruffini E, Dallabona C. Drug Drop Test: How to Quickly Identify Potential Therapeutic Compounds for Mitochondrial Diseases Using Yeast Saccharomyces cerevisiae. Int J Mol Sci 2023; 24:10696. [PMID: 37445873 DOI: 10.3390/ijms241310696] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2023] [Revised: 06/22/2023] [Accepted: 06/25/2023] [Indexed: 07/15/2023] Open
Abstract
Mitochondrial diseases (MDs) refer to a group of clinically and genetically heterogeneous pathologies characterized by defective mitochondrial function and energy production. Unfortunately, there is no effective treatment for most MDs, and current therapeutic management is limited to relieving symptoms. The yeast Saccharomyces cerevisiae has been efficiently used as a model organism to study mitochondria-related disorders thanks to its easy manipulation and well-known mitochondrial biogenesis and metabolism. It has been successfully exploited both to validate alleged pathogenic variants identified in patients and to discover potential beneficial molecules for their treatment. The so-called "drug drop test", a phenotype-based high-throughput screening, especially if coupled with a drug repurposing approach, allows the identification of molecules with high translational potential in a cost-effective and time-saving manner. In addition to drug identification, S. cerevisiae can be used to point out the drug's target or pathway. To date, drug drop tests have been successfully carried out for a variety of disease models, leading to very promising results. The most relevant aspect is that studies on more complex model organisms confirmed the effectiveness of the drugs, strengthening the results obtained in yeast and demonstrating the usefulness of this screening as a novel approach to revealing new therapeutic molecules for MDs.
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Affiliation(s)
- Martina Magistrati
- Department of Chemistry, Life Sciences and Environmental Sustainability, University of Parma, Parco Area delle Scienze 11/A, 43124 Parma, Italy
| | - Alexandru Ionut Gilea
- Department of Chemistry, Life Sciences and Environmental Sustainability, University of Parma, Parco Area delle Scienze 11/A, 43124 Parma, Italy
| | - Maria Carla Gerra
- Department of Chemistry, Life Sciences and Environmental Sustainability, University of Parma, Parco Area delle Scienze 11/A, 43124 Parma, Italy
| | - Enrico Baruffini
- Department of Chemistry, Life Sciences and Environmental Sustainability, University of Parma, Parco Area delle Scienze 11/A, 43124 Parma, Italy
| | - Cristina Dallabona
- Department of Chemistry, Life Sciences and Environmental Sustainability, University of Parma, Parco Area delle Scienze 11/A, 43124 Parma, Italy
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15
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The Journey of Mitochondrial Protein Import and the Roadmap to Follow. Int J Mol Sci 2023; 24:ijms24032479. [PMID: 36768800 PMCID: PMC9916854 DOI: 10.3390/ijms24032479] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2022] [Revised: 01/19/2023] [Accepted: 01/25/2023] [Indexed: 01/31/2023] Open
Abstract
Mitochondria are double membrane-bound organelles that play critical functions in cells including metabolism, energy production, regulation of intrinsic apoptosis, and maintenance of calcium homeostasis. Mitochondria are fascinatingly equipped with their own genome and machinery for transcribing and translating 13 essential proteins of the oxidative phosphorylation system (OXPHOS). The rest of the proteins (99%) that function in mitochondria in the various pathways described above are nuclear-transcribed and synthesized as precursors in the cytosol. These proteins are imported into the mitochondria by the unique mitochondrial protein import system that consists of seven machineries. Proper functioning of the mitochondrial protein import system is crucial for optimal mitochondrial deliverables, as well as mitochondrial and cellular homeostasis. Impaired mitochondrial protein import leads to proteotoxic stress in both mitochondria and cytosol, inducing mitochondrial unfolded protein response (UPRmt). Altered UPRmt is associated with the development of various disease conditions including neurodegenerative and cardiovascular diseases, as well as cancer. This review sheds light on the molecular mechanisms underlying the import of nuclear-encoded mitochondrial proteins, the consequences of defective mitochondrial protein import, and the pathological conditions that arise due to altered UPRmt.
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16
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Molecular and Cellular Interactions in Pathogenesis of Sporadic Parkinson Disease. Int J Mol Sci 2022; 23:ijms232113043. [PMID: 36361826 PMCID: PMC9657547 DOI: 10.3390/ijms232113043] [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: 08/20/2022] [Revised: 10/16/2022] [Accepted: 10/25/2022] [Indexed: 11/23/2022] Open
Abstract
An increasing number of the population all around the world suffer from age-associated neurodegenerative diseases including Parkinson’s disease (PD). This disorder presents different signs of genetic, epigenetic and environmental origin, and molecular, cellular and intracellular dysfunction. At the molecular level, α-synuclein (αSyn) was identified as the principal molecule constituting the Lewy bodies (LB). The gut microbiota participates in the pathogenesis of PD and may contribute to the loss of dopaminergic neurons through mitochondrial dysfunction. The most important pathogenetic link is an imbalance of Ca2+ ions, which is associated with redox imbalance in the cells and increased generation of reactive oxygen species (ROS). In this review, genetic, epigenetic and environmental factors that cause these disorders and their cause-and-effect relationships are considered. As a constituent of environmental factors, the example of organophosphates (OPs) is also reviewed. The role of endothelial damage in the pathogenesis of PD is discussed, and a ‘triple hit hypothesis’ is proposed as a modification of Braak’s dual hit one. In the absence of effective therapies for neurodegenerative diseases, more and more evidence is emerging about the positive impact of nutritional structure and healthy lifestyle on the state of blood vessels and the risk of developing these diseases.
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17
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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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18
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Hoffmann JJ, Becker T. Crosstalk between Mitochondrial Protein Import and Lipids. Int J Mol Sci 2022; 23:ijms23095274. [PMID: 35563660 PMCID: PMC9101885 DOI: 10.3390/ijms23095274] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2022] [Revised: 04/29/2022] [Accepted: 05/05/2022] [Indexed: 12/10/2022] Open
Abstract
Mitochondria import about 1000 precursor proteins from the cytosol. The translocase of the outer membrane (TOM complex) forms the major entry site for precursor proteins. Subsequently, membrane-bound protein translocases sort the precursor proteins into the outer and inner membrane, the intermembrane space, and the matrix. The phospholipid composition of mitochondrial membranes is critical for protein import. Structural and biochemical data revealed that phospholipids affect the stability and activity of mitochondrial protein translocases. Integration of proteins into the target membrane involves rearrangement of phospholipids and distortion of the lipid bilayer. Phospholipids are present in the interface between subunits of protein translocases and affect the dynamic coupling of partner proteins. Phospholipids are required for full activity of the respiratory chain to generate membrane potential, which in turn drives protein import across and into the inner membrane. Finally, outer membrane protein translocases are closely linked to organellar contact sites that mediate lipid trafficking. Altogether, intensive crosstalk between mitochondrial protein import and lipid biogenesis controls mitochondrial biogenesis.
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19
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Crinum latifolium extract inhibits lipopolysaccharide-induced inflammation in human macrophages. REV ROMANA MED LAB 2022. [DOI: 10.2478/rrlm-2022-0015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Abstract
Introduction: Crinum latifolium is a natural plant showing the anti-inflammatory effects. We aimed to evaluate the effects of Crinum latifolium extract on proinflammatory cytokine production and maturation of early and late endosomes in the lipopolysaccharide (LPS)-induced human macrophages at light microscopic and biochemical levels.
Material and Methods: The effects of Crinum latifolium extract in human macrophages stimulated with LPS was evaluated to optic densities of the lysosome-associated membrane protein-1 (LAMP-1) and early endo-some antigen 1 (EEA1) by immunohistochemistry staining and to level of the proinflammatory cytokine interleukin (IL)-6 by enzyme-linked immunosorbent assay (ELISA).
Results: Crinum latifolium group exhibited a significant decreased in the levels of IL-6 in the supernatant as compared to the LPS group for 2 and 72 hours (p<0.0001). Crinum latifolium group exhibited a significant increased in the optic density of the EEA1 and LAMP-1 in coverslips as compared to the control and lipopolysaccharide groups after 2 and 72 hours (p<0.0001).
Conclusions: Crinum latifolium may a therapeutic plant in the inflammatory diseases, such as sepsis, through anti-inflammatory effects, such as decrease in production of the proinflammatory cytokine and increase in maturations of the early and late endosomes in macrophages.
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20
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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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21
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Eldeeb MA, Thomas RA, Ragheb MA, Fallahi A, Fon EA. Mitochondrial quality control in health and in Parkinson's disease. Physiol Rev 2022; 102:1721-1755. [PMID: 35466694 DOI: 10.1152/physrev.00041.2021] [Citation(s) in RCA: 86] [Impact Index Per Article: 43.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
As a central hub for cellular metabolism and intracellular signalling, the mitochondrion is a pivotal organelle, dysfunction of which has been linked to several human diseases including neurodegenerative disorders, and in particular Parkinson's disease. An inherent challenge that mitochondria face is the continuous exposure to diverse stresses which increase their likelihood of dysregulation. In response, eukaryotic cells have evolved sophisticated quality control mechanisms to monitor, identify, repair and/or eliminate abnormal or misfolded proteins within the mitochondrion and/or the dysfunctional mitochondrion itself. Chaperones identify unstable or otherwise abnormal conformations in mitochondrial proteins and can promote their refolding to recover their correct conformation and stability. However, if repair is not possible, the abnormal protein is selectively degraded to prevent potentially damaging interactions with other proteins or its oligomerization into toxic multimeric complexes. The autophagic-lysosomal system and the ubiquitin-proteasome system mediate the selective and targeted degradation of such abnormal or misfolded protein species. Mitophagy (a specific kind of autophagy) mediates the selective elimination of dysfunctional mitochondria, in order to prevent the deleterious effects the dysfunctional organelles within the cell. Despite our increasing understanding of the molecular responses toward dysfunctional mitochondria, many key aspects remain relatively poorly understood. Herein, we review the emerging mechanisms of mitochondrial quality control including quality control strategies coupled to mitochondrial import mechanisms. In addition, we review the molecular mechanisms regulating mitophagy with an emphasis on the regulation of PINK1/PARKIN-mediated mitophagy in cellular physiology and in the context of Parkinson's disease cell biology.
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Affiliation(s)
- Mohamed A Eldeeb
- McGill Parkinson Program, Neurodegenerative Diseases Group, Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada
| | - Rhalena A Thomas
- McGill Parkinson Program, Neurodegenerative Diseases Group, Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada
| | - Mohamed A Ragheb
- Chemistry Department (Biochemistry Division), Faculty of Science, Cairo University, Giza, Egypt
| | - Armaan Fallahi
- McGill Parkinson Program, Neurodegenerative Diseases Group, Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada
| | - Edward A Fon
- McGill Parkinson Program, Neurodegenerative Diseases Group, Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada
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22
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Priesnitz C, Böttinger L, Zufall N, Gebert M, Guiard B, van der Laan M, Becker T. Coupling to Pam16 differentially controls the dual role of Pam18 in protein import and respiratory chain formation. Cell Rep 2022; 39:110619. [PMID: 35385740 DOI: 10.1016/j.celrep.2022.110619] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2021] [Revised: 01/31/2022] [Accepted: 03/15/2022] [Indexed: 11/03/2022] Open
Abstract
The presequence translocase (TIM23 complex) imports precursor proteins into the mitochondrial inner membrane and matrix. The presequence translocase-associated motor (PAM) provides a driving force for transport into the matrix. The J-protein Pam18 stimulates the ATPase activity of the mitochondrial Hsp70 (mtHsp70). Pam16 recruits Pam18 to the TIM23 complex to ensure protein import. The Pam16-Pam18 module also associates with components of the respiratory chain, but the function of the dual localization of Pam16-Pam18 is largely unknown. Here, we show that disruption of the Pam16-Pam18 heterodimer causes redistribution of Pam18 to the respiratory chain supercomplexes, where it forms a homodimer. Redistribution of Pam18 decreases protein import into mitochondria but stimulates mtHsp70-dependent assembly of respiratory chain complexes. We conclude that coupling to Pam16 differentially controls the dual function of Pam18. It recruits Pam18 to the TIM23 complex to promote protein import but attenuates the Pam18 function in the assembly of respiratory chain complexes.
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Affiliation(s)
- Chantal Priesnitz
- Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany; Faculty of Biology, University of Freiburg, 79104 Freiburg, Germany
| | - Lena Böttinger
- Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany
| | - Nicole Zufall
- Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany
| | - Michael Gebert
- Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany
| | | | - Martin van der Laan
- Medical Biochemistry and Molecular Biology, Center for Molecular Signaling, PZMS, Faculty of Medicine, Saarland University, 66421 Homburg, Germany
| | - Thomas Becker
- Institute of Biochemistry and Molecular Biology, Faculty of Medicine, University of Bonn, 53115 Bonn, Germany.
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23
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Araiso Y, Imai K, Endo T. Role of the TOM Complex in Protein Import into Mitochondria: Structural Views. Annu Rev Biochem 2022; 91:679-703. [PMID: 35287471 DOI: 10.1146/annurev-biochem-032620-104527] [Citation(s) in RCA: 23] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Mitochondria are central to energy production, metabolism and signaling, and apoptosis. To make new mitochondria from preexisting mitochondria, the cell needs to import mitochondrial proteins from the cytosol into the mitochondria with the aid of translocators in the mitochondrial membranes. The translocase of the outer membrane (TOM) complex, an outer membrane translocator, functions as an entry gate for most mitochondrial proteins. Although high-resolution structures of the receptor subunits of the TOM complex were deposited in the early 2000s, those of entire TOM complexes became available only in 2019. The structural details of these TOM complexes, consisting of the dimer of the β-barrel import channel Tom40 and four α-helical membrane proteins, revealed the presence of several distinct paths and exits for the translocation of over 1,000 different mitochondrial precursor proteins. High-resolution structures of TOM complexes now open up a new era of studies on the structures, functions, and dynamics of the mitochondrial import system. Expected final online publication date for the Annual Review of Biochemistry, Volume 91 is June 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.
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Affiliation(s)
- Yuhei Araiso
- Department of Clinical Laboratory Science, Division of Health Sciences, Graduate School of Medical Science, Kanazawa University, Kanazawa, Ishikawa, Japan
| | - Kenichiro Imai
- Cellular and Molecular Biotechnology Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Tokyo, Japan
| | - Toshiya Endo
- Faculty of Life Sciences, Kyoto Sangyo University, Kyoto, Japan; .,Institute for Protein Dynamics, Kyoto Sangyo University, Kyoto, Japan
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24
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Eaglesfield R, Tokatlidis K. Targeting and Insertion of Membrane Proteins in Mitochondria. Front Cell Dev Biol 2022; 9:803205. [PMID: 35004695 PMCID: PMC8740019 DOI: 10.3389/fcell.2021.803205] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2021] [Accepted: 12/09/2021] [Indexed: 01/26/2023] Open
Abstract
Mitochondrial membrane proteins play an essential role in all major mitochondrial functions. The respiratory complexes of the inner membrane are key for the generation of energy. The carrier proteins for the influx/efflux of essential metabolites to/from the matrix. Many other inner membrane proteins play critical roles in the import and processing of nuclear encoded proteins (∼99% of all mitochondrial proteins). The outer membrane provides another lipidic barrier to nuclear-encoded protein translocation and is home to many proteins involved in the import process, maintenance of ionic balance, as well as the assembly of outer membrane components. While many aspects of the import and assembly pathways of mitochondrial membrane proteins have been elucidated, many open questions remain, especially surrounding the assembly of the respiratory complexes where certain highly hydrophobic subunits are encoded by the mitochondrial DNA and synthesised and inserted into the membrane from the matrix side. This review will examine the various assembly pathways for inner and outer mitochondrial membrane proteins while discussing the most recent structural and biochemical data examining the biogenesis process.
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Affiliation(s)
- Ross Eaglesfield
- Institute of Molecular Cell and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, University Avenue, Scotland, United Kingdom
| | - Kostas Tokatlidis
- Institute of Molecular Cell and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, University Avenue, Scotland, United Kingdom
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25
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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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26
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Morgenstern M, Peikert CD, Lübbert P, Suppanz I, Klemm C, Alka O, Steiert C, Naumenko N, Schendzielorz A, Melchionda L, Mühlhäuser WWD, Knapp B, Busch JD, Stiller SB, Dannenmaier S, Lindau C, Licheva M, Eickhorst C, Galbusera R, Zerbes RM, Ryan MT, Kraft C, Kozjak-Pavlovic V, Drepper F, Dennerlein S, Oeljeklaus S, Pfanner N, Wiedemann N, Warscheid B. Quantitative high-confidence human mitochondrial proteome and its dynamics in cellular context. Cell Metab 2021; 33:2464-2483.e18. [PMID: 34800366 PMCID: PMC8664129 DOI: 10.1016/j.cmet.2021.11.001] [Citation(s) in RCA: 112] [Impact Index Per Article: 37.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/12/2020] [Revised: 09/01/2021] [Accepted: 11/01/2021] [Indexed: 12/18/2022]
Abstract
Mitochondria are key organelles for cellular energetics, metabolism, signaling, and quality control and have been linked to various diseases. Different views exist on the composition of the human mitochondrial proteome. We classified >8,000 proteins in mitochondrial preparations of human cells and defined a mitochondrial high-confidence proteome of >1,100 proteins (MitoCoP). We identified interactors of translocases, respiratory chain, and ATP synthase assembly factors. The abundance of MitoCoP proteins covers six orders of magnitude and amounts to 7% of the cellular proteome with the chaperones HSP60-HSP10 being the most abundant mitochondrial proteins. MitoCoP dynamics spans three orders of magnitudes, with half-lives from hours to months, and suggests a rapid regulation of biosynthesis and assembly processes. 460 MitoCoP genes are linked to human diseases with a strong prevalence for the central nervous system and metabolism. MitoCoP will provide a high-confidence resource for placing dynamics, functions, and dysfunctions of mitochondria into the cellular context.
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Affiliation(s)
- Marcel Morgenstern
- Institute of Biology II, Biochemistry and Functional Proteomics, Faculty of Biology, University of Freiburg, 79104 Freiburg, Germany
| | - Christian D Peikert
- Institute of Biology II, Biochemistry and Functional Proteomics, Faculty of Biology, University of Freiburg, 79104 Freiburg, Germany
| | - Philipp Lübbert
- Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany; Faculty of Biology, University of Freiburg, 79104 Freiburg, Germany
| | - Ida Suppanz
- Institute of Biology II, Biochemistry and Functional Proteomics, Faculty of Biology, University of Freiburg, 79104 Freiburg, Germany
| | - Cinzia Klemm
- Institute of Biology II, Biochemistry and Functional Proteomics, Faculty of Biology, University of Freiburg, 79104 Freiburg, Germany
| | - Oliver Alka
- Institute of Biology II, Biochemistry and Functional Proteomics, Faculty of Biology, University of Freiburg, 79104 Freiburg, Germany
| | - Conny Steiert
- Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany
| | - Nataliia Naumenko
- Department of Cellular Biochemistry, University Medical Center Göttingen, 37073 Göttingen, Germany
| | - Alexander Schendzielorz
- Institute of Biology II, Biochemistry and Functional Proteomics, Faculty of Biology, University of Freiburg, 79104 Freiburg, Germany
| | - Laura Melchionda
- Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany; CIBSS Centre for Integrative Biological Signalling Studies, University of Freiburg, 79104 Freiburg, Germany
| | - Wignand W D Mühlhäuser
- Institute of Biology II, Biochemistry and Functional Proteomics, Faculty of Biology, University of Freiburg, 79104 Freiburg, Germany
| | - Bettina Knapp
- Institute of Biology II, Biochemistry and Functional Proteomics, Faculty of Biology, University of Freiburg, 79104 Freiburg, Germany
| | - Jakob D Busch
- Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany
| | - Sebastian B Stiller
- Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany
| | - Stefan Dannenmaier
- Institute of Biology II, Biochemistry and Functional Proteomics, Faculty of Biology, University of Freiburg, 79104 Freiburg, Germany
| | - Caroline Lindau
- Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany
| | - Mariya Licheva
- Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany; Faculty of Biology, University of Freiburg, 79104 Freiburg, Germany
| | - Christopher Eickhorst
- Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany; Faculty of Biology, University of Freiburg, 79104 Freiburg, Germany; Spemann Graduate School of Biology and Medicine (SGBM), University of Freiburg, Freiburg, Germany
| | - Riccardo Galbusera
- Neurologic Clinic and Policlinic, Departments of Medicine, Clinical Research and Biomedical Engineering, University Hospital Basel and University of Basel, Basel, Switzerland
| | - Ralf M Zerbes
- Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany
| | - Michael T Ryan
- Department of Biochemistry and Molecular Biology, Monash Biomedicine Discovery Institute, Monash University, 3800 Melbourne, VIC, Australia
| | - Claudine Kraft
- Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany; CIBSS Centre for Integrative Biological Signalling Studies, University of Freiburg, 79104 Freiburg, Germany
| | - Vera Kozjak-Pavlovic
- Department of Microbiology, Biocenter, University of Würzburg, 97074 Würzburg, Germany
| | - Friedel Drepper
- Institute of Biology II, Biochemistry and Functional Proteomics, Faculty of Biology, University of Freiburg, 79104 Freiburg, Germany
| | - Sven Dennerlein
- Department of Cellular Biochemistry, University Medical Center Göttingen, 37073 Göttingen, Germany
| | - Silke Oeljeklaus
- Institute of Biology II, Biochemistry and Functional Proteomics, Faculty of Biology, University of Freiburg, 79104 Freiburg, Germany
| | - Nikolaus Pfanner
- Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany; CIBSS Centre for Integrative Biological Signalling Studies, University of Freiburg, 79104 Freiburg, Germany; BIOSS Centre for Biological Signalling Studies, University of Freiburg, 79104 Freiburg, Germany
| | - Nils Wiedemann
- Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany; CIBSS Centre for Integrative Biological Signalling Studies, University of Freiburg, 79104 Freiburg, Germany; BIOSS Centre for Biological Signalling Studies, University of Freiburg, 79104 Freiburg, Germany.
| | - Bettina Warscheid
- Institute of Biology II, Biochemistry and Functional Proteomics, Faculty of Biology, University of Freiburg, 79104 Freiburg, Germany; CIBSS Centre for Integrative Biological Signalling Studies, University of Freiburg, 79104 Freiburg, Germany; BIOSS Centre for Biological Signalling Studies, University of Freiburg, 79104 Freiburg, Germany.
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27
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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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28
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Mapping protein interactions in the active TOM-TIM23 supercomplex. Nat Commun 2021; 12:5715. [PMID: 34588454 PMCID: PMC8481542 DOI: 10.1038/s41467-021-26016-1] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2020] [Accepted: 08/19/2021] [Indexed: 11/10/2022] Open
Abstract
Nuclear-encoded mitochondrial proteins destined for the matrix have to be transported across two membranes. The TOM and TIM23 complexes facilitate the transport of precursor proteins with N-terminal targeting signals into the matrix. During transport, precursors are recognized by the TIM23 complex in the inner membrane for handover from the TOM complex. However, we have little knowledge on the organization of the TOM-TIM23 transition zone and on how precursor transfer between the translocases occurs. Here, we have designed a precursor protein that is stalled during matrix transport in a TOM-TIM23-spanning manner and enables purification of the translocation intermediate. Combining chemical cross-linking with mass spectrometric analyses and structural modeling allows us to map the molecular environment of the intermembrane space interface of TOM and TIM23 as well as the import motor interactions with amino acid resolution. Our analyses provide a framework for understanding presequence handover and translocation during matrix protein transport. The TOM and TIM23 complexes facilitate the transport of nuclear-encoded proteins into the mitochondrial matrix. Here, the authors use a stalled client protein to purify the translocation supercomplex and gain insight into the TOM-TIM23 interface and the mechanism of protein handover from the TOM to the TIM23 complex.
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29
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The Role of Hsp70s in the Development and Pathogenicity of Plasmodium falciparum. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2021. [PMID: 34569021 DOI: 10.1007/978-3-030-78397-6_3] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/24/2024]
Abstract
The main agent of human malaria, the protozoa, Plasmodium falciparum is known to infect liver cells, subsequently invading the host erythrocyte, leading to the manifestation of clinical outcomes of the disease. As part of its survival in the human host, P. falciparum employs several heat shock protein (Hsp) families whose primary purpose is to ensure cytoprotection through their molecular chaperone role. The parasite expresses six Hsp70s that localise to various subcellular organelles of the parasite, with one, PfHsp70-x, being exported to the infected human erythrocyte. The role of these Hsp70s in the survival and pathogenicity of malaria has received immense research attention. Several studies have reported on their structure-function features, network partnerships, and elucidation of their potential substrates. Apart from their role in cytoprotection and pathogenicity, Hsp70s are implicated in antimalarial drug resistance. As such, they are deemed potential antimalarial drug candidates, especially suited for co-targeting in combination therapies. In addition, Hsp70 is implicated in host immune modulation. The current report highlights the various structure-function features of these proteins, their roles in the development of malaria, current and prospective efforts being employed towards targeting them in malaria intervention efforts.
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30
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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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31
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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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32
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Palmer CS, Lou J, Kouskousis B, Pandzic E, Anderson AJ, Kang Y, Hinde E, Stojanovski D. Super-resolution microscopy reveals the arrangement of inner membrane protein complexes in mammalian mitochondria. J Cell Sci 2021; 134:jcs252197. [PMID: 34313317 DOI: 10.1242/jcs.252197] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2020] [Accepted: 06/03/2021] [Indexed: 12/24/2022] Open
Abstract
The mitochondrial inner membrane is a protein-rich environment containing large multimeric complexes, including complexes of the mitochondrial electron transport chain, mitochondrial translocases and quality control machineries. Although the inner membrane is highly proteinaceous, with 40-60% of all mitochondrial proteins localised to this compartment, little is known about the spatial distribution and organisation of complexes in this environment. We set out to survey the arrangement of inner membrane complexes using stochastic optical reconstruction microscopy (STORM). We reveal that subunits of the TIM23 complex, TIM23 and TIM44 (also known as TIMM23 and TIMM44, respectively), and the complex IV subunit COXIV, form organised clusters and show properties distinct from the outer membrane protein TOM20 (also known as TOMM20). Density based cluster analysis indicated a bimodal distribution of TIM44 that is distinct from TIM23, suggesting distinct TIM23 subcomplexes. COXIV is arranged in larger clusters that are disrupted upon disruption of complex IV assembly. Thus, STORM super-resolution microscopy is a powerful tool for examining the nanoscale distribution of mitochondrial inner membrane complexes, providing a 'visual' approach for obtaining pivotal information on how mitochondrial complexes exist in a cellular context.
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Affiliation(s)
- Catherine S Palmer
- Department of Biochemistry and Pharmacology and The Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Parkville, Victoria 3010, Australia
| | - Jieqiong Lou
- Department of Biochemistry and Pharmacology and The Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Parkville, Victoria 3010, Australia
- School of Physics, The University of Melbourne, Parkville, Victoria 3010, Australia
| | - Betty Kouskousis
- Macfarlane Burnet Institute for Medical Research and Public Health, Melbourne, Victoria 3004, Australia
- Monash Micro Imaging, Monash University, Clayton, Victoria 3168, Australia
| | - Elvis Pandzic
- Biomedical Imaging Facility, Mark Wainwright Analytical Centre, University of New South Wales, Sydney, NSW 2052, Australia
| | - Alexander J Anderson
- Department of Biochemistry and Pharmacology and The Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Parkville, Victoria 3010, Australia
| | - Yilin Kang
- Department of Biochemistry and Pharmacology and The Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Parkville, Victoria 3010, Australia
| | - Elizabeth Hinde
- Department of Biochemistry and Pharmacology and The Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Parkville, Victoria 3010, Australia
- School of Physics, The University of Melbourne, Parkville, Victoria 3010, Australia
| | - Diana Stojanovski
- Department of Biochemistry and Pharmacology and The Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Parkville, Victoria 3010, Australia
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33
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Schlagowski AM, Knöringer K, Morlot S, Sánchez Vicente A, Flohr T, Krämer L, Boos F, Khalid N, Ahmed S, Schramm J, Murschall LM, Haberkant P, Stein F, Riemer J, Westermann B, Braun RJ, Winklhofer KF, Charvin G, Herrmann JM. Increased levels of mitochondrial import factor Mia40 prevent the aggregation of polyQ proteins in the cytosol. EMBO J 2021; 40:e107913. [PMID: 34191328 PMCID: PMC8365258 DOI: 10.15252/embj.2021107913] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2021] [Revised: 05/25/2021] [Accepted: 05/31/2021] [Indexed: 12/11/2022] Open
Abstract
The formation of protein aggregates is a hallmark of neurodegenerative diseases. Observations on patient samples and model systems demonstrated links between aggregate formation and declining mitochondrial functionality, but causalities remain unclear. We used Saccharomyces cerevisiae to analyze how mitochondrial processes regulate the behavior of aggregation‐prone polyQ protein derived from human huntingtin. Expression of Q97‐GFP rapidly led to insoluble cytosolic aggregates and cell death. Although aggregation impaired mitochondrial respiration only slightly, it considerably interfered with the import of mitochondrial precursor proteins. Mutants in the import component Mia40 were hypersensitive to Q97‐GFP, whereas Mia40 overexpression strongly suppressed the formation of toxic Q97‐GFP aggregates both in yeast and in human cells. Based on these observations, we propose that the post‐translational import of mitochondrial precursor proteins into mitochondria competes with aggregation‐prone cytosolic proteins for chaperones and proteasome capacity. Mia40 regulates this competition as it has a rate‐limiting role in mitochondrial protein import. Therefore, Mia40 is a dynamic regulator in mitochondrial biogenesis that can be exploited to stabilize cytosolic proteostasis.
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Affiliation(s)
| | | | - Sandrine Morlot
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, Illkirch, France.,Centre National de la Recherche Scientifique, UMR7104, Illkirch, France.,Institut National de la Santé et de la Recherche Médicale, U964, Illkirch, France.,Université de Strasbourg, Illkirch, France
| | - Ana Sánchez Vicente
- Department of Molecular Cell Biology, Institute of Biochemistry and Pathobiochemistry, Ruhr University Bochum, Bochum, Germany
| | - Tamara Flohr
- Cell Biology, University of Kaiserslautern, Kaiserslautern, Germany
| | - Lena Krämer
- Cell Biology, University of Kaiserslautern, Kaiserslautern, Germany
| | - Felix Boos
- Cell Biology, University of Kaiserslautern, Kaiserslautern, Germany
| | - Nabeel Khalid
- German Research Center for Artificial Intelligence DFKI, Kaiserslautern, Germany
| | - Sheraz Ahmed
- German Research Center for Artificial Intelligence DFKI, Kaiserslautern, Germany
| | - Jana Schramm
- Cell Biology, University of Bayreuth, Bayreuth, Germany
| | | | - Per Haberkant
- Proteomics Core Facility, EMBL Heidelberg, Heidelberg, Germany
| | - Frank Stein
- Proteomics Core Facility, EMBL Heidelberg, Heidelberg, Germany
| | - Jan Riemer
- Biochemistry, University of Cologne, Cologne, Germany
| | | | - Ralf J Braun
- Cell Biology, University of Bayreuth, Bayreuth, Germany.,Neurodegeneration, Danube Private University, Krems/Donau, Austria
| | - Konstanze F Winklhofer
- Department of Molecular Cell Biology, Institute of Biochemistry and Pathobiochemistry, Ruhr University Bochum, Bochum, Germany
| | - Gilles Charvin
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, Illkirch, France.,Centre National de la Recherche Scientifique, UMR7104, Illkirch, France.,Institut National de la Santé et de la Recherche Médicale, U964, Illkirch, France.,Université de Strasbourg, Illkirch, France
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34
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Grevel A, Becker T. Porins as helpers in mitochondrial protein translocation. Biol Chem 2021; 401:699-708. [PMID: 31967957 DOI: 10.1515/hsz-2019-0438] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2019] [Accepted: 01/15/2020] [Indexed: 12/22/2022]
Abstract
Mitochondria import the vast majority of their proteins via dedicated protein machineries. The translocase of the outer membrane (TOM complex) forms the main entry site for precursor proteins that are produced on cytosolic ribosomes. Subsequently, different protein sorting machineries transfer the incoming preproteins to the mitochondrial outer and inner membranes, the intermembrane space, and the matrix. In this review, we highlight the recently discovered role of porin, also termed voltage-dependent anion channel (VDAC), in mitochondrial protein biogenesis. Porin forms the major channel for metabolites and ions in the outer membrane of mitochondria. Two different functions of porin in protein translocation have been reported. First, it controls the formation of the TOM complex by modulating the integration of the central receptor Tom22 into the mature translocase. Second, porin promotes the transport of carrier proteins toward the carrier translocase (TIM22 complex), which inserts these preproteins into the inner membrane. Therefore, porin acts as a coupling factor to spatially coordinate outer and inner membrane transport steps. Thus, porin links metabolite transport to protein import, which are both essential for mitochondrial function and biogenesis.
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Affiliation(s)
- Alexander Grevel
- Institute of Biochemistry und Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany.,Faculty of Biology, University of Freiburg, 79104 Freiburg, Germany
| | - Thomas Becker
- Institute of Biochemistry und Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany.,CIBSS Centre for Integrative Biological Signalling Studies, University of Freiburg, 79104 Freiburg, Germany
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35
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Callegari S, Cruz-Zaragoza LD, Rehling P. From TOM to the TIM23 complex - handing over of a precursor. Biol Chem 2021; 401:709-721. [PMID: 32074073 DOI: 10.1515/hsz-2020-0101] [Citation(s) in RCA: 30] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2020] [Accepted: 02/13/2020] [Indexed: 12/31/2022]
Abstract
Mitochondrial precursor proteins with amino-terminal presequences are imported via the presequence pathway, utilizing the TIM23 complex for inner membrane translocation. Initially, the precursors pass the outer membrane through the TOM complex and are handed over to the TIM23 complex where they are sorted into the inner membrane or translocated into the matrix. This handover process depends on the receptor proteins at the inner membrane, Tim50 and Tim23, which are critical for efficient import. In this review, we summarize key findings that shaped the current concepts of protein translocation along the presequence import pathway, with a particular focus on the precursor handover process from TOM to the TIM23 complex. In addition, we discuss functions of the human TIM23 pathway and the recently uncovered pathogenic mutations in TIM50.
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Affiliation(s)
- Sylvie Callegari
- Department of Cellular Biochemistry, University Medical Center Göttingen, D-37073 Göttingen, Germany
| | - Luis Daniel Cruz-Zaragoza
- Department of Cellular Biochemistry, University Medical Center Göttingen, D-37073 Göttingen, Germany
| | - Peter Rehling
- Department of Cellular Biochemistry, University Medical Center Göttingen, D-37073 Göttingen, Germany.,Max Planck Institute for Biophysical Chemistry, D-37077 Göttingen, Germany
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36
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Needs HI, Protasoni M, Henley JM, Prudent J, Collinson I, Pereira GC. Interplay between Mitochondrial Protein Import and Respiratory Complexes Assembly in Neuronal Health and Degeneration. Life (Basel) 2021; 11:432. [PMID: 34064758 PMCID: PMC8151517 DOI: 10.3390/life11050432] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2021] [Revised: 04/27/2021] [Accepted: 05/02/2021] [Indexed: 12/14/2022] Open
Abstract
The fact that >99% of mitochondrial proteins are encoded by the nuclear genome and synthesised in the cytosol renders the process of mitochondrial protein import fundamental for normal organelle physiology. In addition to this, the nuclear genome comprises most of the proteins required for respiratory complex assembly and function. This means that without fully functional protein import, mitochondrial respiration will be defective, and the major cellular ATP source depleted. When mitochondrial protein import is impaired, a number of stress response pathways are activated in order to overcome the dysfunction and restore mitochondrial and cellular proteostasis. However, prolonged impaired mitochondrial protein import and subsequent defective respiratory chain function contributes to a number of diseases including primary mitochondrial diseases and neurodegeneration. This review focuses on how the processes of mitochondrial protein translocation and respiratory complex assembly and function are interlinked, how they are regulated, and their importance in health and disease.
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Affiliation(s)
- Hope I. Needs
- School of Biochemistry, University of Bristol, Bristol BS8 1TD, UK; (H.I.N.); (J.M.H.)
| | - Margherita Protasoni
- Medical Research Council-Mitochondrial Biology Unit, University of Cambridge, Cambridge CB2 0XY, UK; (M.P.); (J.P.)
| | - Jeremy M. Henley
- School of Biochemistry, University of Bristol, Bristol BS8 1TD, UK; (H.I.N.); (J.M.H.)
- Centre for Neuroscience and Regenerative Medicine, Faculty of Science, University of Technology Sydney, Ultimo, NSW 2007, Australia
| | - Julien Prudent
- Medical Research Council-Mitochondrial Biology Unit, University of Cambridge, Cambridge CB2 0XY, UK; (M.P.); (J.P.)
| | - Ian Collinson
- School of Biochemistry, University of Bristol, Bristol BS8 1TD, UK; (H.I.N.); (J.M.H.)
| | - Gonçalo C. Pereira
- Medical Research Council-Mitochondrial Biology Unit, University of Cambridge, Cambridge CB2 0XY, UK; (M.P.); (J.P.)
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37
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Maity S, Chakrabarti O. Mitochondrial protein import as a quality control sensor. Biol Cell 2021; 113:375-400. [PMID: 33870508 DOI: 10.1111/boc.202100002] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2021] [Revised: 03/04/2021] [Accepted: 04/09/2021] [Indexed: 12/17/2022]
Abstract
Mitochondria are organelles involved in various functions related to cellular metabolism and homoeostasis. Though mitochondria contain own genome, their nuclear counterparts encode most of the different mitochondrial proteins. These are synthesised as precursors in the cytosol and have to be delivered into the mitochondria. These organelles hence have elaborate machineries for the import of precursor proteins from cytosol. The protein import machineries present in both mitochondrial membrane and aqueous compartments show great variability in pre-protein recognition, translocation and sorting across or into it. Mitochondrial protein import machineries also interact transiently with other protein complexes of the respiratory chain or those involved in the maintenance of membrane architecture. Hence mitochondrial protein translocation is an indispensable part of the regulatory network that maintains protein biogenesis, bioenergetics, membrane dynamics and quality control of the organelle. Various stress conditions and diseases that are associated with mitochondrial import defects lead to changes in cellular transcriptomic and proteomic profiles. Dysfunction in mitochondrial protein import also causes over-accumulation of precursor proteins and their aggregation in the cytosol. Multiple pathways may be activated for buffering these harmful consequences. Here, we present a comprehensive picture of import machinery and its role in cellular quality control in response to defective mitochondrial import. We also discuss the pathological consequences of dysfunctional mitochondrial protein import in neurodegeneration and cancer.
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Affiliation(s)
- Sebabrata Maity
- Biophysics & Structural Genomics Division, Saha Institute of Nuclear Physics, Kolkata, 700064, India.,Homi Bhabha National Institute, India
| | - Oishee Chakrabarti
- Biophysics & Structural Genomics Division, Saha Institute of Nuclear Physics, Kolkata, 700064, India.,Homi Bhabha National Institute, India
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38
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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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39
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Jonsdottir TK, Gabriela M, Gilson PR. The Role of Malaria Parasite Heat Shock Proteins in Protein Trafficking and Remodelling of Red Blood Cells. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2021; 1340:141-167. [PMID: 34569024 DOI: 10.1007/978-3-030-78397-6_6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
The genus Plasmodium comprises intracellular eukaryotic parasites that infect many vertebrate groups and cause deadly malaria disease in humans. The parasites employ a suite of heat shock proteins to help traffic other proteins to different compartments within their own cells and that of the host cells they parasitise. This review will cover the role of these chaperones in protein export and host cell modification in the asexual blood stage of the human parasite P. falciparum which is the most deadly and well-studied parasite species. We will examine the role chaperones play in the import of proteins into the secretory pathway from where they are escorted to the vacuole space surrounding the intraerythrocytic parasite. Here, other heat shock proteins unfold protein cargoes and extrude them into the red blood cell (RBC) cytosol from where additional chaperones of parasite and possibly host origin refold the cargo proteins and guide them to their final functional destinations within their RBC host cells. The secretory pathway also serves as a launch pad for proteins targeted to the non-photosynthetic apicoplast organelle of endosymbiotic origin, and the role of heat shock proteins in trafficking proteins here will be reviewed. Finally, the function of chaperones in protein trafficking into the mitochondrion, the remaining organelle of endosymbiotic origin, will be discussed.
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Affiliation(s)
- Thorey K Jonsdottir
- Burnet Institute, Melbourne, VIC, Australia.,Department of Microbiology and Immunology, University of Melbourne, Parkville, VIC, Australia
| | - Mikha Gabriela
- Burnet Institute, Melbourne, VIC, Australia.,School of Medicine, Deakin University, Waurn Ponds, VIC, Australia
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40
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Chaudhuri M, Darden C, Soto Gonzalez F, Singha UK, Quinones L, Tripathi A. Tim17 Updates: A Comprehensive Review of an Ancient Mitochondrial Protein Translocator. Biomolecules 2020; 10:E1643. [PMID: 33297490 PMCID: PMC7762337 DOI: 10.3390/biom10121643] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2020] [Revised: 12/02/2020] [Accepted: 12/03/2020] [Indexed: 02/06/2023] Open
Abstract
The translocases of the mitochondrial outer and inner membranes, the TOM and TIMs, import hundreds of nucleus-encoded proteins into mitochondria. TOM and TIMs are multi-subunit protein complexes that work in cooperation with other complexes to import proteins in different sub-mitochondrial destinations. The overall architecture of these protein complexes is conserved among yeast/fungi, animals, and plants. Recent studies have revealed unique characteristics of this machinery, particularly in the eukaryotic supergroup Excavata. Despite multiple differences, homologues of Tim17, an essential component of one of the TIM complexes and a member of the Tim17/Tim22/Tim23 family, have been found in all eukaryotes. Here, we review the structure and function of Tim17 and Tim17-containing protein complexes in different eukaryotes, and then compare them to the single homologue of this protein found in Trypanosoma brucei, a unicellular parasitic protozoan.
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Affiliation(s)
- Minu Chaudhuri
- Department of Microbiology, Immunology, and Physiology, Meharry Medical College, 1005 Dr. D.B. Todd, Jr., Blvd, Nashville, TN 37208, USA; (C.D.); (F.S.G.); (U.K.S.); (L.Q.); (A.T.)
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41
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Zöller E, Laborenz J, Krämer L, Boos F, Räschle M, Alexander RT, Herrmann JM. The intermembrane space protein Mix23 is a novel stress-induced mitochondrial import factor. J Biol Chem 2020; 295:14686-14697. [PMID: 32826315 PMCID: PMC7586232 DOI: 10.1074/jbc.ra120.014247] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2020] [Revised: 08/19/2020] [Indexed: 12/20/2022] Open
Abstract
The biogenesis of mitochondria requires the import of hundreds of precursor proteins. These proteins are transported post-translationally with the help of chaperones, meaning that the overproduction of mitochondrial proteins or the limited availability of chaperones can lead to the accumulation of cytosolic precursor proteins. This imposes a severe challenge to cytosolic proteostasis and triggers a specific transcription program called the mitoprotein-induced stress response, which activates the proteasome system. This coincides with the repression of mitochondrial proteins, including many proteins of the intermembrane space. In contrast, herein we report that the so-far-uncharacterized intermembrane space protein Mix23 is considerably up-regulated when mitochondrial import is perturbed. Mix23 is evolutionarily conserved and a homolog of the human protein CCDC58. We found that, like the subunits of the proteasome, Mix23 is under control of the transcription factor Rpn4. It is imported into mitochondria by the mitochondrial disulfide relay. Mix23 is critical for the efficient import of proteins into the mitochondrial matrix, particularly if the function of the translocase of the inner membrane 23 is compromised such as in temperature-sensitive mutants of Tim17. Our observations identify Mix23 as a novel regulator or stabilizer of the mitochondrial protein import machinery that is specifically up-regulated upon mitoprotein-induced stress conditions.
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Affiliation(s)
- Eva Zöller
- Department of Cell Biology, University of Kaiserslautern, Kaiserslautern, Germany
| | - Janina Laborenz
- Department of Cell Biology, University of Kaiserslautern, Kaiserslautern, Germany
| | - Lena Krämer
- Department of Cell Biology, University of Kaiserslautern, Kaiserslautern, Germany
| | - Felix Boos
- Department of Cell Biology, University of Kaiserslautern, Kaiserslautern, Germany
| | - Markus Räschle
- Department of Molecular Genetics, University of Kaiserslautern, Kaiserslautern, Germany
| | - R Todd Alexander
- Department of Pediatrics, University of Alberta, Edmonton, Alberta, Canada
| | - Johannes M Herrmann
- Department of Cell Biology, University of Kaiserslautern, Kaiserslautern, Germany.
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42
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Cupo RR, Shorter J. Skd3 (human ClpB) is a potent mitochondrial protein disaggregase that is inactivated by 3-methylglutaconic aciduria-linked mutations. eLife 2020; 9:e55279. [PMID: 32573439 PMCID: PMC7343390 DOI: 10.7554/elife.55279] [Citation(s) in RCA: 37] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2020] [Accepted: 06/22/2020] [Indexed: 12/14/2022] Open
Abstract
Cells have evolved specialized protein disaggregases to reverse toxic protein aggregation and restore protein functionality. In nonmetazoan eukaryotes, the AAA+ disaggregase Hsp78 resolubilizes and reactivates proteins in mitochondria. Curiously, metazoa lack Hsp78. Hence, whether metazoan mitochondria reactivate aggregated proteins is unknown. Here, we establish that a mitochondrial AAA+ protein, Skd3 (human ClpB), couples ATP hydrolysis to protein disaggregation and reactivation. The Skd3 ankyrin-repeat domain combines with conserved AAA+ elements to enable stand-alone disaggregase activity. A mitochondrial inner-membrane protease, PARL, removes an autoinhibitory peptide from Skd3 to greatly enhance disaggregase activity. Indeed, PARL-activated Skd3 solubilizes α-synuclein fibrils connected to Parkinson's disease. Human cells lacking Skd3 exhibit reduced solubility of various mitochondrial proteins, including anti-apoptotic Hax1. Importantly, Skd3 variants linked to 3-methylglutaconic aciduria, a severe mitochondrial disorder, display diminished disaggregase activity (but not always reduced ATPase activity), which predicts disease severity. Thus, Skd3 is a potent protein disaggregase critical for human health.
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Affiliation(s)
- Ryan R Cupo
- Department of Biochemistry and Biophysics, Perelman School of Medicine at the University of PennsylvaniaPhiladelphiaUnited States
- Pharmacology Graduate Group, Perelman School of Medicine at the University of PennsylvaniaPhiladelphiaUnited States
| | - James Shorter
- Department of Biochemistry and Biophysics, Perelman School of Medicine at the University of PennsylvaniaPhiladelphiaUnited States
- Pharmacology Graduate Group, Perelman School of Medicine at the University of PennsylvaniaPhiladelphiaUnited States
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43
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How to get to the other side of the mitochondrial inner membrane – the protein import motor. Biol Chem 2020; 401:723-736. [DOI: 10.1515/hsz-2020-0106] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2020] [Accepted: 02/25/2020] [Indexed: 12/13/2022]
Abstract
AbstractBiogenesis of mitochondria relies on import of more than 1000 different proteins from the cytosol. Approximately 70% of these proteins follow the presequence pathway – they are synthesized with cleavable N-terminal extensions called presequences and reach the final place of their function within the organelle with the help of the TOM and TIM23 complexes in the outer and inner membranes, respectively. The translocation of proteins along the presequence pathway is powered by the import motor of the TIM23 complex. The import motor of the TIM23 complex is localized at the matrix face of the inner membrane and is likely the most complicated Hsp70-based system identified to date. How it converts the energy of ATP hydrolysis into unidirectional translocation of proteins into mitochondria remains one of the biggest mysteries of this translocation pathway. Here, the knowns and the unknowns of the mitochondrial protein import motor are discussed.
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44
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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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45
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Matta SK, Kumar A, D'Silva P. Mgr2 regulates mitochondrial preprotein import by associating with channel-forming Tim23 subunit. Mol Biol Cell 2020; 31:1112-1123. [PMID: 32186971 PMCID: PMC7353164 DOI: 10.1091/mbc.e19-12-0677] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Mgr2, a newly identified subunit of the TIM23 complex, functions as a gatekeeper of presequence translocase and thereby maintains quality control of inner membrane preproteins sorting. However, precise recruitment of the Mgr2 subunit to the core channel and how it influences the assembly of the TIM23 complex during lateral sorting of preproteins are poorly understood. Present findings provide insights into a direct association of Mgr2 with the channel-forming Tim23 subunit. Furthermore, the mutational analysis uncovers the TM1 region of Mgr2 critically required for association with Tim23 and Tim21. On the other hand, the TM2 region of Mgr2 is involved in bridging respiratory complexes to the TIM23 complex via Tim21. Importantly, both TM regions of Mgr2 are essential for lateral sorting of preprotein into the inner membrane, as well as maintaining mitochondrial morphology. Together, our findings provide mechanistic insights into the role of Mgr2 in regulating the dynamicity of the TIM23 complex assembly required for preprotein import and coupling of respiratory pathways.
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Affiliation(s)
- Srujan Kumar Matta
- Department of Biochemistry, New Biological Sciences Building, Indian Institute of Science, Bangalore-560012, India
| | - Abhishek Kumar
- Department of Biochemistry, New Biological Sciences Building, Indian Institute of Science, Bangalore-560012, India
| | - Patrick D'Silva
- Department of Biochemistry, New Biological Sciences Building, Indian Institute of Science, Bangalore-560012, India
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46
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Laborenz J, Hansen K, Prescianotto-Baschong C, Spang A, Herrmann JM. In vitro import experiments with semi-intact cells suggest a role of the Sec61 paralog Ssh1 in mitochondrial biogenesis. Biol Chem 2020; 400:1229-1240. [PMID: 31199753 DOI: 10.1515/hsz-2019-0196] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2019] [Accepted: 05/03/2019] [Indexed: 12/21/2022]
Abstract
Mitochondrial biogenesis relies on the synthesis of hundreds of different precursor proteins in the cytosol and their subsequent import into the organelle. Recent studies suggest that the surface of the endoplasmic reticulum (ER) actively contributes to the targeting of some mitochondrial precursors. In the past, in vitro import experiments with isolated mitochondria proved to be extremely powerful to elucidate the individual reactions of the mitochondrial import machinery. However, this in vitro approach is not well suited to study the influence of non-mitochondrial membranes. In this study, we describe an in vitro system using semi-intact yeast cells to test a potential import relevance of the ER proteins Erg3, Lcb5 and Ssh1, all being required for efficient mitochondrial respiration. We optimized the conditions of this experimental test system and found that cells lacking Ssh1, a paralog of the Sec61 translocation pore, show a reduced import efficiency of mitochondrial precursor proteins. Our results suggest that Ssh1, directly or indirectly, increases the efficiency of the biogenesis of mitochondrial proteins. Our findings are compatible with a functional interdependence of the mitochondrial and the ER protein translocation systems.
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Affiliation(s)
- Janina Laborenz
- Cell Biology, University of Kaiserslautern, Erwin-Schrödinger-Strasse 13, D-67663 Kaiserslautern, Germany
| | - Katja Hansen
- Cell Biology, University of Kaiserslautern, Erwin-Schrödinger-Strasse 13, D-67663 Kaiserslautern, Germany
| | | | - Anne Spang
- Biozentrum, University of Basel, CH-4056 Basel, Switzerland
| | - Johannes M Herrmann
- Cell Biology, University of Kaiserslautern, Erwin-Schrödinger-Strasse 13, D-67663 Kaiserslautern, Germany
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47
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Abstract
Mitochondria are essential organelles of eukaryotic cells. They consist of hundreds of different proteins that exhibit crucial activities in respiration, catabolic metabolism and the synthesis of amino acids, lipids, heme and iron-sulfur clusters. With the exception of a handful of hydrophobic mitochondrially encoded membrane proteins, all these proteins are synthesized on cytosolic ribosomes, targeted to receptors on the mitochondrial surface, and transported across or inserted into the outer and inner mitochondrial membrane before they are folded and assembled into their final native structure. This review article provides a comprehensive overview of the mechanisms and components of the mitochondrial protein import systems with a particular focus on recent developments in the field.
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Affiliation(s)
- Katja G Hansen
- Cell Biology, University of Kaiserslautern, Erwin-Schrödinger-Strasse 13, 67663, Kaiserslautern, Germany
| | - Johannes M Herrmann
- Cell Biology, University of Kaiserslautern, Erwin-Schrödinger-Strasse 13, 67663, Kaiserslautern, Germany.
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48
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Rampelt H, Sucec I, Bersch B, Horten P, Perschil I, Martinou JC, van der Laan M, Wiedemann N, Schanda P, Pfanner N. The mitochondrial carrier pathway transports non-canonical substrates with an odd number of transmembrane segments. BMC Biol 2020; 18:2. [PMID: 31907035 PMCID: PMC6945462 DOI: 10.1186/s12915-019-0733-6] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2019] [Accepted: 12/17/2019] [Indexed: 02/07/2023] Open
Abstract
BACKGROUND The mitochondrial pyruvate carrier (MPC) plays a central role in energy metabolism by transporting pyruvate across the inner mitochondrial membrane. Its heterodimeric composition and homology to SWEET and semiSWEET transporters set the MPC apart from the canonical mitochondrial carrier family (named MCF or SLC25). The import of the canonical carriers is mediated by the carrier translocase of the inner membrane (TIM22) pathway and is dependent on their structure, which features an even number of transmembrane segments and both termini in the intermembrane space. The import pathway of MPC proteins has not been elucidated. The odd number of transmembrane segments and positioning of the N-terminus in the matrix argues against an import via the TIM22 carrier pathway but favors an import via the flexible presequence pathway. RESULTS Here, we systematically analyzed the import pathways of Mpc2 and Mpc3 and report that, contrary to an expected import via the flexible presequence pathway, yeast MPC proteins with an odd number of transmembrane segments and matrix-exposed N-terminus are imported by the carrier pathway, using the receptor Tom70, small TIM chaperones, and the TIM22 complex. The TIM9·10 complex chaperones MPC proteins through the mitochondrial intermembrane space using conserved hydrophobic motifs that are also required for the interaction with canonical carrier proteins. CONCLUSIONS The carrier pathway can import paired and non-paired transmembrane helices and translocate N-termini to either side of the mitochondrial inner membrane, revealing an unexpected versatility of the mitochondrial import pathway for non-cleavable inner membrane proteins.
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Affiliation(s)
- Heike Rampelt
- Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, 79104, Freiburg, Germany.
- CIBSS Centre for Integrative Biological Signalling Studies, University of Freiburg, 79104, Freiburg, Germany.
| | - Iva Sucec
- Institut de Biologie Structurale (IBS), Univ. Grenoble Alpes, CEA, CNRS, 38000, Grenoble, France
| | - Beate Bersch
- Institut de Biologie Structurale (IBS), Univ. Grenoble Alpes, CEA, CNRS, 38000, Grenoble, France
| | - Patrick Horten
- Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, 79104, Freiburg, Germany
- CIBSS Centre for Integrative Biological Signalling Studies, University of Freiburg, 79104, Freiburg, Germany
- Faculty of Biology, University of Freiburg, 79104, Freiburg, Germany
| | - Inge Perschil
- Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, 79104, Freiburg, Germany
| | | | - Martin van der Laan
- Medical Biochemistry and Molecular Biology, Center for Molecular Signaling, PZMS, Saarland University, 66421 Homburg, Germany
| | - Nils Wiedemann
- Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, 79104, Freiburg, Germany
- CIBSS Centre for Integrative Biological Signalling Studies, University of Freiburg, 79104, Freiburg, Germany
- BIOSS Centre for Biological Signalling Studies, University of Freiburg, 79104, Freiburg, Germany
| | - Paul Schanda
- Institut de Biologie Structurale (IBS), Univ. Grenoble Alpes, CEA, CNRS, 38000, Grenoble, France
| | - Nikolaus Pfanner
- Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, 79104, Freiburg, Germany.
- CIBSS Centre for Integrative Biological Signalling Studies, University of Freiburg, 79104, Freiburg, Germany.
- BIOSS Centre for Biological Signalling Studies, University of Freiburg, 79104, Freiburg, Germany.
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49
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Lee S, Lee H, Yoo S, Ieva R, van der Laan M, von Heijne G, Kim H. The Mgr2 subunit of the TIM23 complex regulates membrane insertion of marginal stop-transfer signals in the mitochondrial inner membrane. FEBS Lett 2019; 594:1081-1087. [PMID: 31764998 DOI: 10.1002/1873-3468.13692] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2019] [Revised: 11/04/2019] [Accepted: 11/12/2019] [Indexed: 11/08/2022]
Abstract
The TIM23 complex mediates membrane insertion of presequence-containing mitochondrial proteins via a stop-transfer mechanism. Stop-transfer signals consist of hydrophobic transmembrane segments and flanking charges. Mgr2 functions as a lateral gatekeeper of the TIM23 complex. However, it remains elusive which features of stop-transfer signals are discriminated by Mgr2. To determine the effects of Mgr2 on the TIM23-mediated stop-transfer pathway, we measured membrane insertion of model transmembrane segments of varied hydrophobicity and flanking charges in Mgr2-deletion or -overexpression yeast strains. We found that upon deletion of Mgr2, the threshold hydrophobicity for membrane insertion, as well as the requirement for matrix-facing positive charges, is reduced. These results imply that the Mgr2-mediated gatekeeper function is important for controlling membrane sorting of marginal stop-transfer signals.
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Affiliation(s)
- Seoeun Lee
- School of Biological Sciences, Seoul National University, South Korea
| | - Hunsang Lee
- School of Biological Sciences, Seoul National University, South Korea.,Donnelly Centre, Toronto, Canada
| | - Suji Yoo
- School of Biological Sciences, Seoul National University, South Korea
| | - Raffaele Ieva
- Laboratoire de Microbiologie et Génétique Moléculaire, Centre de Biologie Intégrative, Université de Toulouse, CNRS, UPS, France
| | - Martin van der Laan
- Medical Biochemistry and Molecular Biology, Center for Molecular Signaling, PZMS, Saarland University, Homburg, Germany
| | - Gunnar von Heijne
- Department of Biochemistry and Biophysics, Stockholm University, Sweden
| | - Hyun Kim
- School of Biological Sciences, Seoul National University, South Korea
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Structure of the mitochondrial import gate reveals distinct preprotein paths. Nature 2019; 575:395-401. [PMID: 31600774 DOI: 10.1038/s41586-019-1680-7] [Citation(s) in RCA: 137] [Impact Index Per Article: 27.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2019] [Accepted: 09/30/2019] [Indexed: 11/08/2022]
Abstract
The translocase of the outer mitochondrial membrane (TOM) is the main entry gate for proteins1-4. Here we use cryo-electron microscopy to report the structure of the yeast TOM core complex5-9 at 3.8-Å resolution. The structure reveals the high-resolution architecture of the translocator consisting of two Tom40 β-barrel channels and α-helical transmembrane subunits, providing insight into critical features that are conserved in all eukaryotes1-3. Each Tom40 β-barrel is surrounded by small TOM subunits, and tethered by two Tom22 subunits and one phospholipid. The N-terminal extension of Tom40 forms a helix inside the channel; mutational analysis reveals its dual role in early and late steps in the biogenesis of intermembrane-space proteins in cooperation with Tom5. Each Tom40 channel possesses two precursor exit sites. Tom22, Tom40 and Tom7 guide presequence-containing preproteins to the exit in the middle of the dimer, whereas Tom5 and the Tom40 N extension guide preproteins lacking a presequence to the exit at the periphery of the dimer.
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