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von Känel C, Oeljeklaus S, Wenger C, Stettler P, Harsman A, Warscheid B, Schneider A. Intermembrane space-localized TbTim15 is an essential subunit of the single mitochondrial inner membrane protein translocase of trypanosomes. Mol Microbiol 2024; 121:1112-1126. [PMID: 38622999 DOI: 10.1111/mmi.15262] [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: 01/23/2024] [Revised: 03/24/2024] [Accepted: 03/25/2024] [Indexed: 04/17/2024]
Abstract
All mitochondria import >95% of their proteins from the cytosol. This process is mediated by protein translocases in the mitochondrial membranes, whose subunits are generally highly conserved. Most eukaryotes have two inner membrane protein translocases (TIMs) that are specialized to import either presequence-containing or mitochondrial carrier proteins. In contrast, the parasitic protozoan Trypanosoma brucei has a single TIM complex consisting of one conserved and five unique subunits. Here, we identify candidates for new subunits of the TIM or the presequence translocase-associated motor (PAM) using a protein-protein interaction network of previously characterized TIM and PAM subunits. This analysis reveals that the trypanosomal TIM complex contains an additional trypanosomatid-specific subunit, designated TbTim15. TbTim15 is associated with the TIM complex, lacks transmembrane domains, and localizes to the intermembrane space. TbTim15 is essential for procyclic and bloodstream forms of trypanosomes. It contains two twin CX9C motifs and mediates import of both presequence-containing and mitochondrial carrier proteins. While the precise function of TbTim15 in mitochondrial protein import is unknown, our results are consistent with the notion that it may function as an import receptor for the non-canonical trypanosomal TIM complex.
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Affiliation(s)
- Corinne von Känel
- Department of Chemistry, Biochemistry and Pharmaceutical Sciences, University of Bern, Bern, Switzerland
| | - Silke Oeljeklaus
- Faculty of Chemistry and Pharmacy, Biochemistry II, Theodor Boveri-Institute, University of Würzburg, Würzburg, Germany
| | - Christoph Wenger
- Department of Chemistry, Biochemistry and Pharmaceutical Sciences, University of Bern, Bern, Switzerland
| | - Philip Stettler
- Department of Chemistry, Biochemistry and Pharmaceutical Sciences, University of Bern, Bern, Switzerland
| | - Anke Harsman
- Department of Chemistry, Biochemistry and Pharmaceutical Sciences, University of Bern, Bern, Switzerland
| | - Bettina Warscheid
- Faculty of Chemistry and Pharmacy, Biochemistry II, Theodor Boveri-Institute, University of Würzburg, Würzburg, Germany
| | - André Schneider
- Department of Chemistry, Biochemistry and Pharmaceutical Sciences, University of Bern, Bern, Switzerland
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Quiñones LS, Gonzalez FS, Darden C, Khan M, Tripathi A, Smith JT, Davis J, Misra S, Chaudhuri M. Unique Interactions of the Small Translocases of the Mitochondrial Inner Membrane (Tims) in Trypanosoma brucei. Int J Mol Sci 2024; 25:1415. [PMID: 38338692 PMCID: PMC10855554 DOI: 10.3390/ijms25031415] [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: 10/25/2023] [Revised: 01/10/2024] [Accepted: 01/19/2024] [Indexed: 02/12/2024] Open
Abstract
The infectious agent for African trypanosomiasis, Trypanosoma brucei, possesses a unique and essential translocase of the mitochondrial inner membrane, known as the TbTIM17 complex. TbTim17 associates with six small TbTims (TbTim9, TbTim10, TbTim11, TbTim12, TbTim13, and TbTim8/13). However, the interaction patterns of these smaller TbTims with each other and TbTim17 are not clear. Through yeast two-hybrid (Y2H) and co-immunoprecipitation analyses, we demonstrate that all six small TbTims interact with each other. Stronger interactions were found among TbTim8/13, TbTim9, and TbTim10. However, TbTim10 shows weaker associations with TbTim13, which has a stronger connection with TbTim17. Each of the small TbTims also interacts strongly with the C-terminal region of TbTim17. RNAi studies indicated that among all small TbTims, TbTim13 is most crucial for maintaining the steady-state levels of the TbTIM17 complex. Further analysis of the small TbTim complexes by size exclusion chromatography revealed that each small TbTim, except for TbTim13, is present in ~70 kDa complexes, possibly existing in heterohexameric forms. In contrast, TbTim13 is primarily present in the larger complex (>800 kDa) and co-fractionates with TbTim17. Altogether, our results demonstrate that, relative to other eukaryotes, the architecture and function of the small TbTim complexes are specific to T. brucei.
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Affiliation(s)
- Linda S. Quiñones
- Department of Microbiology, Immunology, and Physiology, School of Medicine, Meharry Medical College, Nashville, TN 37208, USA; (L.S.Q.); (F.S.G.); (M.K.); (A.T.)
| | - Fidel Soto Gonzalez
- Department of Microbiology, Immunology, and Physiology, School of Medicine, Meharry Medical College, Nashville, TN 37208, USA; (L.S.Q.); (F.S.G.); (M.K.); (A.T.)
| | - Chauncey Darden
- Department of Biochemistry, Cancer Biology, Neuroscience, and Pharmacology, School of Medicine, Meharry Medical College, Nashville, TN 37208, USA; (C.D.); (J.D.)
| | - Muhammad Khan
- Department of Microbiology, Immunology, and Physiology, School of Medicine, Meharry Medical College, Nashville, TN 37208, USA; (L.S.Q.); (F.S.G.); (M.K.); (A.T.)
| | - Anuj Tripathi
- Department of Microbiology, Immunology, and Physiology, School of Medicine, Meharry Medical College, Nashville, TN 37208, USA; (L.S.Q.); (F.S.G.); (M.K.); (A.T.)
| | - Joseph T. Smith
- Department of Microbiology and Immunology, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo, NY 14203, USA;
| | - Jamaine Davis
- Department of Biochemistry, Cancer Biology, Neuroscience, and Pharmacology, School of Medicine, Meharry Medical College, Nashville, TN 37208, USA; (C.D.); (J.D.)
| | - Smita Misra
- Department of Biomedical Science, School of Graduate Studies, Meharry Medical College, Nashville, TN 37208, USA;
| | - Minu Chaudhuri
- Department of Microbiology, Immunology, and Physiology, School of Medicine, Meharry Medical College, Nashville, TN 37208, USA; (L.S.Q.); (F.S.G.); (M.K.); (A.T.)
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Quiñones Guillén LS, Gonzalez FS, Darden C, Khan M, Tripathi A, Smith JT, Cooley A, Paromov V, Davis J, Misra S, Chaudhuri M. Unique interactions and functions of the mitochondrial small Tims in Trypanosoma brucei. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.05.29.542777. [PMID: 37398442 PMCID: PMC10312748 DOI: 10.1101/2023.05.29.542777] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/04/2023]
Abstract
Trypanosoma brucei is an early divergent parasitic protozoan that causes a fatal disease, African trypanosomiasis. T. brucei possesses a unique and essential translocase of the mitochondrial inner membrane, the TbTIM17 complex. TbTim17 associates with 6 small TbTims, (TbTim9, TbTim10, TbTim11, TbTim12, TbTim13, and TbTim8/13). However, the interaction pattern of the small TbTims with each other and TbTim17 are not clear. Here, we demonstrated by yeast two-hybrid (Y2H) analysis that all six small TbTims interact with each other, but stronger interactions were found among TbTim8/13, TbTim9, and TbTim10. Each of the small TbTims also interact directly with the C-terminal region of TbTim17. RNAi studies indicated that among all small TbTims, TbTim13 is most crucial to maintain the steady-state levels of the TbTIM17 complex. Co-immunoprecipitation analyses from T. brucei mitochondrial extracts also showed that TbTim10 has a stronger association with TbTim9 and TbTim8/13, but a weaker association with TbTim13, whereas TbTim13 has a stronger connection with TbTim17. Analysis of the small TbTim complexes by size exclusion chromatography revealed that each small TbTim, except TbTim13, is present in ∼70 kDa complexes, which could be heterohexameric forms of the small TbTims. However, TbTim13 is primarily present in the larger complex (>800 kDa) and co-fractionated with TbTim17. Altogether, our results demonstrated that TbTim13 is a part of the TbTIM complex and the smaller complexes of the small TbTims likely interact with the larger complex dynamically. Therefore, relative to other eukaryotes, the architecture and function of the small TbTim complexes are specific in T. brucei .
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Wenger C, Harsman A, Niemann M, Oeljeklaus S, von Känel C, Calderaro S, Warscheid B, Schneider A. The Mba1 homologue of Trypanosoma brucei is involved in the biogenesis of oxidative phosphorylation complexes. Mol Microbiol 2023; 119:537-550. [PMID: 36829306 DOI: 10.1111/mmi.15048] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2022] [Revised: 02/16/2023] [Accepted: 02/21/2023] [Indexed: 02/26/2023]
Abstract
Consistent with other eukaryotes, the Trypanosoma brucei mitochondrial genome encodes mainly hydrophobic core subunits of the oxidative phosphorylation system. These proteins must be co-translationally inserted into the inner mitochondrial membrane and are synthesized by the highly unique trypanosomal mitoribosomes, which have a much higher protein to RNA ratio than any other ribosome. Here, we show that the trypanosomal orthologue of the mitoribosome receptor Mba1 (TbMba1) is essential for normal growth of procyclic trypanosomes but redundant in the bloodstream form, which lacks an oxidative phosphorylation system. Proteomic analyses of TbMba1-depleted mitochondria from procyclic cells revealed reduced levels of many components of the oxidative phosphorylation system, most of which belong to the cytochrome c oxidase (Cox) complex, three subunits of which are mitochondrially encoded. However, the integrity of the mitoribosome and its interaction with the inner membrane were not affected. Pull-down experiments showed that TbMba1 forms a dynamic interaction network that includes the trypanosomal Mdm38/Letm1 orthologue and a trypanosome-specific factor that stabilizes the CoxI and CoxII mRNAs. In summary, our study suggests that the function of Mba1 in the biogenesis of membrane subunits of OXPHOS complexes is conserved among yeast, mammals and trypanosomes, which belong to two eukaryotic supergroups.
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Affiliation(s)
- Christoph Wenger
- Department of Chemistry, Biochemistry and Pharmaceutical Sciences, University of Bern, Bern, Switzerland
| | - Anke Harsman
- Department of Chemistry, Biochemistry and Pharmaceutical Sciences, University of Bern, Bern, Switzerland
| | - Moritz Niemann
- Department of Chemistry, Biochemistry and Pharmaceutical Sciences, University of Bern, Bern, Switzerland
| | - Silke Oeljeklaus
- Faculty of Chemistry and Pharmacy, Biochemistry II, Theodor Boveri-Institute, University of Würzburg, Würzburg, Germany
| | - Corinne von Känel
- Department of Chemistry, Biochemistry and Pharmaceutical Sciences, University of Bern, Bern, Switzerland
| | - Salvatore Calderaro
- Department of Chemistry, Biochemistry and Pharmaceutical Sciences, University of Bern, Bern, Switzerland
| | - Bettina Warscheid
- Faculty of Chemistry and Pharmacy, Biochemistry II, Theodor Boveri-Institute, University of Würzburg, Würzburg, Germany.,CIBSS Centre for Integrative Biological Signalling Studies, University of Freiburg, Freiburg, Germany
| | - André Schneider
- Department of Chemistry, Biochemistry and Pharmaceutical Sciences, University of Bern, Bern, Switzerland.,Institute for Advanced Study (Wissenschaftskolleg) Berlin, Berlin, Germany
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Soto-Gonzalez F, Tripathi A, Cooley A, Paromov V, Rana T, Chaudhuri M. A novel connection between Trypanosoma brucei mitochondrial proteins TbTim17 and TbTRAP1 is discovered using Biotinylation Identification (BioID). J Biol Chem 2022; 298:102647. [PMID: 36309084 PMCID: PMC9694106 DOI: 10.1016/j.jbc.2022.102647] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2022] [Revised: 10/12/2022] [Accepted: 10/14/2022] [Indexed: 11/25/2022] Open
Abstract
The protein translocase of the mitochondrial inner membrane in Trypanosoma brucei, TbTIM17, forms a modular complex in association with several other trypanosome-specific proteins. To identify transiently interacting proximal partner(s) of TbTim17, we used Biotinylation Identification (BioID) by expressing a modified biotin ligase-TbTim17 (BirA∗-TbTim17) fusion protein in T. brucei. BirA∗-TbTim17 was targeted to mitochondria and assembled in the TbTIM complex. In the presence of biotin, BirA∗-TbTim17 biotinylated several mitochondrial proteins. Interestingly, TbHsp84/TbTRAP1, a mitochondrial Hsp90 homolog, was identified as the highest enriched biotinylated proteins. We validated that interaction and colocalization of TbTim17 and TbHsp84 in T. brucei mitochondria by coimmunoprecipitation analysis and confocal microscopy, respectively. TbTim17 association with TbTRAP1 increased several folds during denaturation/renaturation of mitochondrial proteins in vitro, suggesting TbTRAP1 acts as a chaperone for TbTim17 refolding. We demonstrated that knockdown of TbTRAP1 reduced cell growth and decreased the levels of the TbTIM17, TbTim62, and mitochondrial (m)Hsp70 complexes. However, ATPase, VDAC, and Atom69 complexes were minimally affected. Additionally, the steady state levels of TbTim17, TbTim62, and mHsp70 were reduced significantly, but Atom69, ATPase β, and RBP16 were mostly unaltered due to TbTRAP1 knockdown. Quantitative proteomics analysis also showed significant reduction of TbTim62 along with a few other mitochondrial proteins due to TbTRAP1 knockdown. Finally, TbTRAP1 depletion did not hamper the import of the ectopically expressed TbTim17-2xMyc into mitochondria but reduced its assembly into the TbTIM17 complex, indicating TbTRAP1 is critical for assembly of TbTim17. This is the first report showing the role of TRAP1 in the TIM complex assembly in eukaryotes.
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Affiliation(s)
- Fidel Soto-Gonzalez
- Department of Microbiology, Immunology, and Physiology, School of Medicine, Meharry Medical College, Nashville, Tennessee, USA
| | - Anuj Tripathi
- Department of Microbiology, Immunology, and Physiology, School of Medicine, Meharry Medical College, Nashville, Tennessee, USA
| | - Ayorinde Cooley
- Department of Microbiology, Immunology, and Physiology, School of Medicine, Meharry Medical College, Nashville, Tennessee, USA
| | - Victor Paromov
- Department of Microbiology, Immunology, and Physiology, School of Medicine, Meharry Medical College, Nashville, Tennessee, USA
| | - Tanu Rana
- Department of Microbiology, Immunology, and Physiology, School of Medicine, Meharry Medical College, Nashville, Tennessee, USA
| | - Minu Chaudhuri
- Department of Microbiology, Immunology, and Physiology, School of Medicine, Meharry Medical College, Nashville, Tennessee, USA.
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Pedra-Rezende Y, Bombaça ACS, Menna-Barreto/ RFS. Is the mitochondrion a promising drug target in trypanosomatids? Mem Inst Oswaldo Cruz 2022; 117:e210379. [PMID: 35195164 PMCID: PMC8862782 DOI: 10.1590/0074-02760210379] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2021] [Accepted: 12/13/2021] [Indexed: 12/23/2022] Open
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Trypanosoma brucei Tim50 Possesses PAP Activity and Plays a Critical Role in Cell Cycle Regulation and Parasite Infectivity. mBio 2021; 12:e0159221. [PMID: 34517757 PMCID: PMC8546626 DOI: 10.1128/mbio.01592-21] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Trypanosoma brucei, the infective agent for African trypanosomiasis, possesses a homologue of the translocase of the mitochondrial inner membrane 50 (TbTim50). It has a pair of characteristic phosphatase signature motifs, DXDX(T/V). Here, we demonstrated that, besides its protein phosphatase activity, the recombinant TbTim50 binds and hydrolyzes phosphatidic acid in a concentration-dependent manner. Mutations of D242 and D244, but not of D345and D347, to alanine abolished these activities. In silico structural homology models identified the putative binding interfaces that may accommodate different phosphosubstrates. Interestingly, TbTim50 depletion in the bloodstream form (BF) of T. brucei reduced cardiolipin (CL) levels and decreased mitochondrial membrane potential (ΔΨ). TbTim50 knockdown (KD) also reduced the population of G2/M phase and increased that of G1 phase cells; inhibited segregation and caused overreplication of kinetoplast DNA (kDNA), and reduced BF cell growth. Depletion of TbTim50 increased the levels of AMPK phosphorylation, and parasite morphology was changed with upregulation of expression of a few stumpy marker genes. Importantly, we observed that TbTim50-depleted parasites were unable to establish infection in mice. Proteomics analysis showed reductions in levels of the translation factors, flagellar transport proteins, and many proteasomal subunits, including those of the mitochondrial heat shock locus ATPase (HslVU), which is known to play a role in regulation of kinetoplast DNA (kDNA) replication. Reduction of the level of HslV in TbTim50 KD cells was further validated by immunoblot analysis. Together, our results showed that TbTim50 is essential for mitochondrial function, regulation of kDNA replication, and the cell cycle in the BF. Therefore, TbTim50 is an important target for structure-based drug design to combat African trypanosomiasis.
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Chaudhuri M, Tripathi A, Gonzalez FS. Diverse Functions of Tim50, a Component of the Mitochondrial Inner Membrane Protein Translocase. Int J Mol Sci 2021; 22:7779. [PMID: 34360547 PMCID: PMC8346121 DOI: 10.3390/ijms22157779] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2021] [Revised: 07/14/2021] [Accepted: 07/16/2021] [Indexed: 12/17/2022] Open
Abstract
Mitochondria are essential in eukaryotes. Besides producing 80% of total cellular ATP, mitochondria are involved in various cellular functions such as apoptosis, inflammation, innate immunity, stress tolerance, and Ca2+ homeostasis. Mitochondria are also the site for many critical metabolic pathways and are integrated into the signaling network to maintain cellular homeostasis under stress. Mitochondria require hundreds of proteins to perform all these functions. Since the mitochondrial genome only encodes a handful of proteins, most mitochondrial proteins are imported from the cytosol via receptor/translocase complexes on the mitochondrial outer and inner membranes known as TOMs and TIMs. Many of the subunits of these protein complexes are essential for cell survival in model yeast and other unicellular eukaryotes. Defects in the mitochondrial import machineries are also associated with various metabolic, developmental, and neurodegenerative disorders in multicellular organisms. In addition to their canonical functions, these protein translocases also help maintain mitochondrial structure and dynamics, lipid metabolism, and stress response. This review focuses on the role of Tim50, the receptor component of one of the TIM complexes, in different cellular functions, with an emphasis on the Tim50 homologue in parasitic protozoan Trypanosoma brucei.
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Affiliation(s)
- Minu Chaudhuri
- Department of Microbiology, Immunology, and Physiology, Meharry Medical College, Nashville, TN 37208, USA; (A.T.); (F.S.G.)
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Wenger C, Schneider A. Minimal peptide length required to span the mitochondrial protein translocases in Trypanosoma brucei. Mol Biochem Parasitol 2021; 244:111393. [PMID: 34197864 DOI: 10.1016/j.molbiopara.2021.111393] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2021] [Revised: 06/23/2021] [Accepted: 06/24/2021] [Indexed: 10/21/2022]
Abstract
Mitochondrial protein import depends on heterooligomeric translocases in the outer and inner membranes. Using import substrates consisting of various lengths of the N-terminal part of mitochondrial dihydrolipoamide dehydrogenase (LDH) fused to dihydrofolate reductase we present an in vivo analysis showing that in Trypanosoma brucei at least 96 aa of mature LDH are required to efficiently produce an import intermediate that spans both translocases. This is different to yeast, where around 50 aa are sufficient to achieve the same task and likely reflects the different arrangement and architecture of the trypanosomal mitochondrial translocases. Furthermore, we show that formation of the stuck import intermediate leads to a strong growth inhibition suggesting that, depending on the length of the LDH, the import channels in the translocases are quantitatively blocked.
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Affiliation(s)
- Christoph Wenger
- Department of Chemistry, Biochemistry and Pharmaceutical Sciences, University of Bern, Freiestr. 3, CH-3012, Bern, Switzerland
| | - André Schneider
- Department of Chemistry, Biochemistry and Pharmaceutical Sciences, University of Bern, Freiestr. 3, CH-3012, Bern, Switzerland.
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Amodeo S, Kalichava A, Fradera-Sola A, Bertiaux-Lequoy E, Guichard P, Butter F, Ochsenreiter T. Characterization of the novel mitochondrial genome segregation factor TAP110 in Trypanosoma brucei. J Cell Sci 2021; 134:jcs254300. [PMID: 33589495 PMCID: PMC7970207 DOI: 10.1242/jcs.254300] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2020] [Accepted: 02/03/2021] [Indexed: 12/18/2022] Open
Abstract
Proper mitochondrial genome inheritance is important for eukaryotic cell survival. Trypanosoma brucei, a protozoan parasite, contains a singular mitochondrial genome, the kinetoplast (k)DNA. The kDNA is anchored to the basal body via the tripartite attachment complex (TAC) to ensure proper segregation. Several components of the TAC have been described; however, the connection of the TAC to the kDNA remains elusive. Here, we characterize the TAC-associated protein TAP110. We find that both depletion and overexpression of TAP110 leads to a delay in the separation of the replicated kDNA networks. Proteome analysis after TAP110 overexpression identified several kDNA-associated proteins that changed in abundance, including a TEX-like protein that dually localizes to the nucleus and the kDNA, potentially linking replication and segregation in the two compartments. The assembly of TAP110 into the TAC region seems to require the TAC but not the kDNA itself; however, once TAP110 has been assembled, it also interacts with the kDNA. Finally, we use ultrastructure expansion microscopy in trypanosomes for the first time, and reveal the precise position of TAP110 between TAC102 and the kDNA, showcasing the potential of this approach.This article has an associated First Person interview with the first author of the paper.
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Affiliation(s)
- Simona Amodeo
- Institute of Cell Biology, University of Bern, 3012 Bern, Switzerland
- Graduate School for Cellular and Biomedical Sciences, University of Bern, 3012 Bern, Switzerland
| | - Ana Kalichava
- Institute of Cell Biology, University of Bern, 3012 Bern, Switzerland
- Graduate School for Cellular and Biomedical Sciences, University of Bern, 3012 Bern, Switzerland
| | | | - Eloïse Bertiaux-Lequoy
- Department of Cell Biology, University of Geneva, Sciences III, 1211 Geneva, Switzerland
| | - Paul Guichard
- Department of Cell Biology, University of Geneva, Sciences III, 1211 Geneva, Switzerland
| | - Falk Butter
- Institute of Molecular Biology, 55128 Mainz, Germany
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Singha UK, Tripathi A, Smith JT, Quinones L, Saha A, Singha T, Chaudhuri M. Novel IM-associated protein Tim54 plays a role in the mitochondrial import of internal signal-containing proteins in Trypanosoma brucei. Biol Cell 2021; 113:39-57. [PMID: 33084070 PMCID: PMC8265390 DOI: 10.1111/boc.202000054] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2020] [Accepted: 08/28/2020] [Indexed: 01/16/2023]
Abstract
BACKGROUND The translocase of the mitochondrial inner membrane (TIM) imports most of the nucleus-encoded proteins that are destined for the matrix, inner membrane (IM) and the intermembrane space (IMS). Trypanosoma brucei, the infectious agent for African trypanosomiasis, possesses a unique TIM complex consisting of several novel proteins in association with a relatively conserved protein TbTim17. Tandem affinity purification of the TbTim17 protein complex revealed TbTim54 as a potential component of this complex. RESULTS TbTim54, a trypanosome-specific IMS protein, is peripherally associated with the IM and is present in a protein complex slightly larger than the TbTim17 complex. TbTim54 knockdown (KD) reduced the import of TbTim17 and compromised the integrity of the TbTim17 complex. TbTim54 KD inhibited the in vitro mitochondrial import and assembly of the internal signal-containing mitochondrial carrier proteins MCP3, MCP5 and MCP11 to a greater extent than TbTim17 KD. Furthermore, TbTim54 KD, but not TbTim17 KD, significantly hampered the mitochondrial targeting of ectopically expressed MCP3 and MCP11. These observations along with our previous finding that the mitochondrial import of N-terminal signal-containing proteins like cytochrome oxidase subunit 4 and MRP2 was affected to a greater extent by TbTim17 KD than TbTim54 KD indicating a substrate-specificity of TbTim54 for internal-signal containing mitochondrial proteins. In other organisms, small Tim chaperones in the IMS are known to participate in the translocation of MCPs. We found that TbTim54 can directly interact with at least two of the six known small TbTim proteins, TbTim11 and TbTim13, as well as with the N-terminal domain of TbTim17. CONCLUSION TbTim54 interacts with TbTim17. It also plays a crucial role in the mitochondrial import and complex assembly of internal signal-containing IM proteins in T. brucei. SIGNIFICANCE We are the first to characterise TbTim54, a novel TbTim that is involved primarily in the mitochondrial import of MCPs and TbTim17 in T. brucei.
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Shikha S, Huot JL, Schneider A, Niemann M. tRNA import across the mitochondrial inner membrane in T. brucei requires TIM subunits but is independent of protein import. Nucleic Acids Res 2020; 48:12269-12281. [PMID: 33231678 PMCID: PMC7708065 DOI: 10.1093/nar/gkaa1098] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2020] [Revised: 10/20/2020] [Accepted: 11/03/2020] [Indexed: 01/27/2023] Open
Abstract
Mitochondrial tRNA import is widespread, but mechanistic insights of how tRNAs are translocated across mitochondrial membranes remain scarce. The parasitic protozoan T. brucei lacks mitochondrial tRNA genes. Consequently, it imports all organellar tRNAs from the cytosol. Here we investigated the connection between tRNA and protein translocation across the mitochondrial inner membrane. Trypanosomes have a single inner membrane protein translocase that consists of three heterooligomeric submodules, which all are required for import of matrix proteins. In vivo depletion of individual submodules shows that surprisingly only the integral membrane core module, including the protein import pore, but not the presequence-associated import motor are required for mitochondrial tRNA import. Thus we could uncouple import of matrix proteins from import of tRNAs even though both substrates are imported into the same mitochondrial subcompartment. This is reminiscent to the outer membrane where the main protein translocase but not on-going protein translocation is required for tRNA import. We also show that import of tRNAs across the outer and inner membranes are coupled to each other. Taken together, these data support the 'alternate import model', which states that tRNA and protein import while mechanistically independent use the same translocation pores but not at the same time.
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Affiliation(s)
- Shikha Shikha
- Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, 3012 Bern, Switzerland
| | - Jonathan L Huot
- Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, 3012 Bern, Switzerland
| | - André Schneider
- Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, 3012 Bern, Switzerland
| | - Moritz Niemann
- Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, 3012 Bern, Switzerland
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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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Barozai MYK, Chaudhuri M. Role of the translocase of the mitochondrial inner membrane in the import of tRNAs into mitochondria in Trypanosoma brucei. Gene 2020; 748:144705. [PMID: 32339625 PMCID: PMC7304388 DOI: 10.1016/j.gene.2020.144705] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2019] [Revised: 04/07/2020] [Accepted: 04/21/2020] [Indexed: 02/07/2023]
Abstract
Trypanosomatids are unicellular parasitic protozoa. Many of the species of this genera cause severe diseases in human, such as Leishmaniasis, African trypanosomiasis and Chagas disease. These parasites possess a single reticular mitochondrion with a concatenated structure of mitochondrial DNA known as kinetoplast or kDNA. kDNA encodes few essential mitochondrial proteins but no tRNAs. Therefore, trypanosomatid mitochondrion import a full set of nucleus-encoded tRNAs for mitochondrial translation. Recent advances indicated that mitochondrial protein translocases, particularly the subunits of the ATOM complex, are involved in the import of a tRNA in Trypanosoma brucei. However, the global picture and the role of the translocase components of the mitochondrial inner membrane (TbTims) are not well understood. Here we investigated the relative abundance of 16 different tRNAs in the cytosolic and mitochondrial fractions isolated from the six TbTims knockdown cell lines. We found that knockdown of TbTim17, one of the primary components of the TbTIM complex, reduced the abundance of all of these tRNAs into mitochondria and increased their abundance in the cytosol. Depletion of TbTim62, a TbTim17 associated proteins, also reduced the relative abundance of most of these tRNAs into mitochondria except for tRNAleu, tRNAmet, and tRNAglu. Whereas, knockdown of other TbTims, like TbTim50 and two small TbTims, TbTim10 and TbTim8/13, didn't have any effect on tRNA abundance either in the cytosol or mitochondria. Depletion of any of these TbTims showed minimal effect on the levels of total tRNAs in T. brucei. Absolute quantification of tRNA levels revealed that TbTim17 knockdown reduced the levels of different tRNAs in mitochondria from 3-6% to 0.8-1.4%, which is equivalent to ~70% reduction in average. Whereas, TbTim62 depletion showed somewhat selective effect. Overall, our results suggest that TbTim17 and TbTim62 are essential for tRNA import that further makes a connection between the tRNA and protein import into mitochondria in T. brucei.
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Affiliation(s)
- Muhammad Younas Khan Barozai
- Department of Microbiology, Immunology, and Physiology, Meharry Medical College, Nashville, TN 37208, United States
| | - Minu Chaudhuri
- Department of Microbiology, Immunology, and Physiology, Meharry Medical College, Nashville, TN 37208, United States.
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Schneider A. Evolution of mitochondrial protein import – lessons from trypanosomes. Biol Chem 2020; 401:663-676. [DOI: 10.1515/hsz-2019-0444] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2019] [Accepted: 03/02/2020] [Indexed: 01/02/2023]
Abstract
AbstractThe evolution of mitochondrial protein import and the systems that mediate it marks the boundary between the endosymbiotic ancestor of mitochondria and a true organelle that is under the control of the nucleus. Protein import has been studied in great detail inSaccharomyces cerevisiae. More recently, it has also been extensively investigated in the parasitic protozoanTrypanosoma brucei, making it arguably the second best studied system. A comparative analysis of the protein import complexes of yeast and trypanosomes is provided. Together with data from other systems, this allows to reconstruct the ancestral features of import complexes that were present in the last eukaryotic common ancestor (LECA) and to identify which subunits were added later in evolution. How these data can be translated into plausible scenarios is discussed, providing insights into the evolution of (i) outer membrane protein import receptors, (ii) proteins involved in biogenesis of α-helically anchored outer membrane proteins, and (iii) of the intermembrane space import and assembly system. Finally, it is shown that the unusual presequence-associated import motor of trypanosomes suggests a scenario of how the two ancestral inner membrane protein translocases present in LECA evolved into the single bifunctional one found in extant trypanosomes.
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Affiliation(s)
- André Schneider
- Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, CH-3012 Bern, Switzerland
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von Känel C, Muñoz-Gómez SA, Oeljeklaus S, Wenger C, Warscheid B, Wideman JG, Harsman A, Schneider A. Homologue replacement in the import motor of the mitochondrial inner membrane of trypanosomes. eLife 2020; 9:52560. [PMID: 32105215 PMCID: PMC7064343 DOI: 10.7554/elife.52560] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2019] [Accepted: 02/26/2020] [Indexed: 01/13/2023] Open
Abstract
Many mitochondrial proteins contain N-terminal presequences that direct them to the organelle. The main driving force for their translocation across the inner membrane is provided by the presequence translocase-associated motor (PAM) which contains the J-protein Pam18. Here, we show that in the PAM of Trypanosoma brucei the function of Pam18 has been replaced by the non-orthologous euglenozoan-specific J-protein TbPam27. TbPam27 is specifically required for the import of mitochondrial presequence-containing but not for carrier proteins. Similar to yeast Pam18, TbPam27 requires an intact J-domain to function. Surprisingly, T. brucei still contains a bona fide Pam18 orthologue that, while essential for normal growth, is not involved in protein import. Thus, during evolution of kinetoplastids, Pam18 has been replaced by TbPam27. We propose that this replacement is linked to the transition from two ancestral and functionally distinct TIM complexes, found in most eukaryotes, to the single bifunctional TIM complex present in trypanosomes.
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Affiliation(s)
- Corinne von Känel
- Department of Chemistry and Biochemistry, University of Bern, Bern, Switzerland
| | - Sergio A Muñoz-Gómez
- Center for Mechanisms of Evolution, Biodesign Institute, School of Life Sciences, Arizona State University, Tempe, United States
| | - Silke Oeljeklaus
- Biochemistry and Functional Proteomics, Institute of Biology II, Faculty of Biology and Signalling Research Centres BIOSS and CIBSS, University of Freiburg, Freiburg, Germany
| | - Christoph Wenger
- Department of Chemistry and Biochemistry, University of Bern, Bern, Switzerland
| | - Bettina Warscheid
- Biochemistry and Functional Proteomics, Institute of Biology II, Faculty of Biology and Signalling Research Centres BIOSS and CIBSS, University of Freiburg, Freiburg, Germany
| | - Jeremy G Wideman
- Center for Mechanisms of Evolution, Biodesign Institute, School of Life Sciences, Arizona State University, Tempe, United States
| | - Anke Harsman
- Department of Chemistry and Biochemistry, University of Bern, Bern, Switzerland
| | - Andre Schneider
- Department of Chemistry and Biochemistry, University of Bern, Bern, Switzerland
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Eichenberger C, Oeljeklaus S, Bruggisser J, Mani J, Haenni B, Kaurov I, Niemann M, Zuber B, Lukeš J, Hashimi H, Warscheid B, Schimanski B, Schneider A. The highly diverged trypanosomal MICOS complex is organized in a nonessential integral membrane and an essential peripheral module. Mol Microbiol 2019; 112:1731-1743. [DOI: 10.1111/mmi.14389] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/14/2019] [Indexed: 12/18/2022]
Affiliation(s)
- Claudia Eichenberger
- Department of Chemistry and Biochemistry University of Bern Freiestrasse 3 Bern CH‐3012Switzerland
| | - Silke Oeljeklaus
- Department of Biochemistry and Functional Proteomics, Faculty of Biology University of Freiburg Freiburg 79104Germany
- Signalling Research Centres BIOSS and CIBSS University of Freiburg Freiburg 79104Germany
| | - Julia Bruggisser
- Department of Chemistry and Biochemistry University of Bern Freiestrasse 3 Bern CH‐3012Switzerland
| | - Jan Mani
- Department of Chemistry and Biochemistry University of Bern Freiestrasse 3 Bern CH‐3012Switzerland
| | - Beat Haenni
- Institute of Anatomy University of Bern Baltzerstrasse 2 Bern 3012Switzerland
| | - Iosif Kaurov
- Institute of Parasitology, Biology Center Czech Academy of Sciences České Budějovice (Budweis) Czech Republic
- Faculty of Science University of South Bohemia 370 05České Budějovice (Budweis) Czech Republic
| | - Moritz Niemann
- Department of Chemistry and Biochemistry University of Bern Freiestrasse 3 Bern CH‐3012Switzerland
| | - Benoît Zuber
- Institute of Anatomy University of Bern Baltzerstrasse 2 Bern 3012Switzerland
| | - Julius Lukeš
- Institute of Parasitology, Biology Center Czech Academy of Sciences České Budějovice (Budweis) Czech Republic
- Faculty of Science University of South Bohemia 370 05České Budějovice (Budweis) Czech Republic
| | - Hassan Hashimi
- Institute of Parasitology, Biology Center Czech Academy of Sciences České Budějovice (Budweis) Czech Republic
- Faculty of Science University of South Bohemia 370 05České Budějovice (Budweis) Czech Republic
| | - Bettina Warscheid
- Department of Biochemistry and Functional Proteomics, Faculty of Biology University of Freiburg Freiburg 79104Germany
- Signalling Research Centres BIOSS and CIBSS University of Freiburg Freiburg 79104Germany
| | - Bernd Schimanski
- Department of Chemistry and Biochemistry University of Bern Freiestrasse 3 Bern CH‐3012Switzerland
| | - André Schneider
- Department of Chemistry and Biochemistry University of Bern Freiestrasse 3 Bern CH‐3012Switzerland
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Kaurov I, Vancová M, Schimanski B, Cadena LR, Heller J, Bílý T, Potěšil D, Eichenberger C, Bruce H, Oeljeklaus S, Warscheid B, Zdráhal Z, Schneider A, Lukeš J, Hashimi H. The Diverged Trypanosome MICOS Complex as a Hub for Mitochondrial Cristae Shaping and Protein Import. Curr Biol 2018; 28:3393-3407.e5. [PMID: 30415698 DOI: 10.1016/j.cub.2018.09.008] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2018] [Revised: 08/02/2018] [Accepted: 09/04/2018] [Indexed: 12/20/2022]
Abstract
The mitochondrial contact site and cristae organization system (MICOS) is a multiprotein complex responsible for cristae formation. Even though cristae are found in all mitochondria capable of oxidative phosphorylation, only Mic10 and Mic60 appear to be conserved throughout eukaryotes. The remaining 4 or 5 known MICOS subunits are specific to the supergroup Opisthokonta, which includes yeast and mammals that are the only organisms in which this complex has been analyzed experimentally. We have isolated the MICOS from Trypanosoma brucei, a member of the supergroup Excavata that is profoundly diverged from opisthokonts. We show that it is required for the maintenance of the unique discoidal cristae that typify excavates, such as euglenids and kinetoplastids, the latter of which include trypanosomes. The trypanosome MICOS consists of 9 subunits, most of which are essential for normal growth. Unlike in opisthokonts, it contains two distinct Mic10 orthologs and an unconventional putative Mic60 that lacks a mitofilin domain. Interestingly, one of the essential trypanosomatid-specific MICOS subunits called TbMic20 is a thioredoxin-like protein that appears to be involved in import of intermembrane space proteins, including respiratory chain complex assembly factors. This result points to trypanosome MICOS coordinating cristae shaping and population of its membrane with proteins involved in respiration, the latter via the catalytic activity of TbMic20. Thus, trypanosome MICOS allows us to define which of its features are conserved in all eukaryotes and decipher those that represent lineage-specific adaptations.
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Affiliation(s)
- Iosif Kaurov
- Institute of Parasitology, Biology Center, Czech Academy of Sciences, 37005 České Budějovice, Czech Republic; Faculty of Science, University of South Bohemia, 37005 České Budějovice, Czech Republic
| | - Marie Vancová
- Institute of Parasitology, Biology Center, Czech Academy of Sciences, 37005 České Budějovice, Czech Republic; Faculty of Science, University of South Bohemia, 37005 České Budějovice, Czech Republic
| | - Bernd Schimanski
- Department of Chemistry and Biochemistry, University of Bern, 3012 Bern, Switzerland
| | - Lawrence Rudy Cadena
- Faculty of Science, University of South Bohemia, 37005 České Budějovice, Czech Republic
| | - Jiří Heller
- Institute of Parasitology, Biology Center, Czech Academy of Sciences, 37005 České Budějovice, Czech Republic
| | - Tomáš Bílý
- Institute of Parasitology, Biology Center, Czech Academy of Sciences, 37005 České Budějovice, Czech Republic; Faculty of Science, University of South Bohemia, 37005 České Budějovice, Czech Republic
| | - David Potěšil
- Central European Institute of Technology, Masaryk University, 62500 Brno, Czech Republic
| | - Claudia Eichenberger
- Department of Chemistry and Biochemistry, University of Bern, 3012 Bern, Switzerland
| | - Hannah Bruce
- Faculty of Science, University of South Bohemia, 37005 České Budějovice, Czech Republic
| | - Silke Oeljeklaus
- Faculty of Biology, Biochemistry and Functional Proteomics, Institute of Biology II, University of Freiburg, 79104 Freiburg, Germany
| | - Bettina Warscheid
- Faculty of Biology, Biochemistry and Functional Proteomics, Institute of Biology II, University of Freiburg, 79104 Freiburg, Germany; BIOSS Centre for Biological Signaling Studies, University of Freiburg, 79104 Freiburg, Germany
| | - Zbyněk Zdráhal
- Central European Institute of Technology, Masaryk University, 62500 Brno, Czech Republic
| | - André Schneider
- Department of Chemistry and Biochemistry, University of Bern, 3012 Bern, Switzerland
| | - Julius Lukeš
- Institute of Parasitology, Biology Center, Czech Academy of Sciences, 37005 České Budějovice, Czech Republic; Faculty of Science, University of South Bohemia, 37005 České Budějovice, Czech Republic
| | - Hassan Hashimi
- Institute of Parasitology, Biology Center, Czech Academy of Sciences, 37005 České Budějovice, Czech Republic; Faculty of Science, University of South Bohemia, 37005 České Budějovice, Czech Republic.
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Divergent Small Tim Homologues Are Associated with TbTim17 and Critical for the Biogenesis of TbTim17 Protein Complexes in Trypanosoma brucei. mSphere 2018; 3:3/3/e00204-18. [PMID: 29925672 PMCID: PMC6010621 DOI: 10.1128/msphere.00204-18] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2018] [Accepted: 05/27/2018] [Indexed: 12/18/2022] Open
Abstract
The small Tim proteins belong to a group of mitochondrial intermembrane space chaperones that aid in the import of mitochondrial inner membrane proteins with internal targeting signals. Trypanosoma brucei, the protozoan parasite that causes African trypanosomiasis, possesses multiple small Tim proteins that include homologues of T. brucei Tim9 (TbTim9) and Tim10 (TbTim10) and a unique small Tim that shares homology with both Tim8 and Tim13 (TbTim8/13). Here, we found that these three small TbTims are expressed as soluble mitochondrial intermembrane space proteins. Coimmunoprecipitation and mass spectrometry analysis showed that the small TbTims stably associated with each other and with TbTim17, the major component of the mitochondrial inner membrane translocase in T. brucei Yeast two-hybrid analysis indicated direct interactions among the small TbTims; however, their interaction patterns appeared to be different from those of their counterparts in yeast and humans. Knockdown of the small TbTims reduced cell growth and decreased the steady-state level of TbTim17 and T. brucei ADP/ATP carrier (TbAAC), two polytopic mitochondrial inner membrane proteins. Knockdown of small TbTims also reduced the matured complexes of TbTim17 in mitochondria. Depletion of any of the small TbTims reduced TbTim17 import moderately but greatly hampered the stability of the TbTim17 complexes in T. brucei Altogether, our results revealed that TbTim9, TbTim10, and TbTim8/13 interact with each other, associate with TbTim17, and play a crucial role in the integrity and maintenance of the levels of TbTim17 complexes.IMPORTANCETrypanosoma brucei is the causative agent of African sleeping sickness. The parasite's mitochondrion represents a useful source for potential chemotherapeutic targets. Similarly to yeast and humans, mitochondrial functions depend on the import of proteins that are encoded in the nucleus and made in the cytosol. Even though the machinery involved in this mitochondrial protein import process is becoming clearer in T. brucei, a comprehensive picture of protein complex composition and function is still lacking. In this study, we characterized three T. brucei small Tim proteins, TbTim9, TbTim10, and TbTim8/13. Although the parasite does not have the classical TIM22 complex that imports mitochondrial inner membrane proteins containing internal targeting signals in yeast or humans, we found that these small TbTims associate with TbTim17, the major subunit of the TbTIM complex in T. brucei, and play an essential role in the stability of the TbTim17 complexes. Therefore, these divergent proteins are critical for mitochondrial protein biogenesis in T. brucei.
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