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Muneretto G, Plazzi F, Passamonti M. Mitochondrion-to-nucleus communication mediated by RNA export: a survey of potential mechanisms and players across eukaryotes. Biol Lett 2024; 20:20240147. [PMID: 38982851 PMCID: PMC11283861 DOI: 10.1098/rsbl.2024.0147] [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: 03/20/2024] [Revised: 05/16/2024] [Accepted: 06/06/2024] [Indexed: 07/11/2024] Open
Abstract
The nucleus interacts with the other organelles to perform essential functions of the eukaryotic cell. Mitochondria have their own genome and communicate back to the nucleus in what is known as mitochondrial retrograde response. Information is transferred to the nucleus in many ways, leading to wide-ranging changes in nuclear gene expression and culminating with changes in metabolic, regulatory or stress-related pathways. RNAs are emerging molecules involved in this signalling. RNAs encode precise information and are involved in highly target-specific signalling, through a wide range of processes known as RNA interference. RNA-mediated mitochondrial retrograde response requires these molecules to exit the mitochondrion, a process that is still mostly unknown. We suggest that the proteins/complexes translocases of the inner membrane, polynucleotide phosphorylase, mitochondrial permeability transition pore, and the subunits of oxidative phosphorylation complexes may be responsible for RNA export.
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Affiliation(s)
- Giorgio Muneretto
- Department of Biological, Geological and Environmental Sciences, University of Bologna, Bologna, Italy
| | - Federico Plazzi
- Department of Biological, Geological and Environmental Sciences, University of Bologna, Bologna, Italy
| | - Marco Passamonti
- Department of Biological, Geological and Environmental Sciences, University of Bologna, Bologna, Italy
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2
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Ghosh S, Hom Choudhury S, Mukherjee K, Bhattacharyya SN. HuR-miRNA complex activates RAS GTPase RalA to facilitate endosome targeting and extracellular export of miRNAs. J Biol Chem 2024; 300:105750. [PMID: 38360271 PMCID: PMC10956062 DOI: 10.1016/j.jbc.2024.105750] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2023] [Revised: 02/01/2024] [Accepted: 02/07/2024] [Indexed: 02/17/2024] Open
Abstract
Extracellular vesicles-mediated exchange of miRNA cargos between diverse types of mammalian cells is a major mechanism of controlling cellular miRNA levels and activity, thus regulating the expression of miRNA-target genes in both donor and recipient cells. Despite tremendous excitement related to extracellular vesicles-associated miRNAs as biomarkers or having therapeutic potential, the mechanism of selective packaging of miRNAs into endosomes and multivesicular bodies for subsequent extracellular export is poorly studied due to the lack of an in vitro assay system. Here, we have developed an in vitro assay with endosomes isolated from mammalian macrophage cells to follow miRNA packaging into endocytic organelles. The synthetic miRNAs, used in the assay, get imported inside the isolated endosomes during the in vitro reaction and become protected from RNase in a time- and concentration-dependent manner. The selective miRNA accumulation inside endosomes requires both ATP and GTP hydrolysis and the miRNA-binding protein HuR. The HuR-miRNA complex binds and stimulates the endosomal RalA GTPase to facilitate the import of miRNAs into endosomes and their subsequent export as part of the extracellular vesicles. The endosomal targeting of miRNAs is also very much dependent on the endosome maturation process that is controlled by Rab5 protein and ATP. In summary, we provide an in vitro method to aid in the investigation of the mechanism of miRNA packaging process for its export from mammalian macrophage cells.
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Affiliation(s)
- Syamantak Ghosh
- RNA Biology Research Laboratory, Molecular Genetics Division, CSIR-Indian Institute of Chemical Biology, Kolkata, India
| | - Sourav Hom Choudhury
- RNA Biology Research Laboratory, Molecular Genetics Division, CSIR-Indian Institute of Chemical Biology, Kolkata, India
| | - Kamalika Mukherjee
- RNA Biology Research Laboratory, Molecular Genetics Division, CSIR-Indian Institute of Chemical Biology, Kolkata, India; Department of Pharmacology and Experimental Neuroscience, University of Nebraska Medical Center (UNMC), Nebraska, USA.
| | - Suvendra N Bhattacharyya
- RNA Biology Research Laboratory, Molecular Genetics Division, CSIR-Indian Institute of Chemical Biology, Kolkata, India; Department of Pharmacology and Experimental Neuroscience, University of Nebraska Medical Center (UNMC), Nebraska, USA.
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3
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Ashrafmansouri M, Amiri‐Dashatan N, Ahmadi N, Rezaei‐Tavirani M, SeyyedTabaei S, Haghighi A. Quantitative proteomic analysis to determine differentially expressed proteins in axenic amastigotes of
Leishmania tropica
and
Leishmania major. IUBMB Life 2020; 72:1715-1724. [DOI: 10.1002/iub.2300] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2019] [Revised: 03/25/2020] [Accepted: 04/17/2020] [Indexed: 12/12/2022]
Affiliation(s)
- Marzieh Ashrafmansouri
- Department of Medical Parasitology and Mycology, Student Research Committee, School of MedicineShahid Beheshti University of Medical Sciences Tehran Iran
- Diagnostic Laboratory Sciences and Technology Research Center, Faculty of Paramedical SciencesShiraz University of Medical Sciences Shiraz Iran
| | - Nasrin Amiri‐Dashatan
- Proteomics Research Center, Faculty of Paramedical SciencesShahid Beheshti University of Medical Sciences Tehran Iran
| | - Nayebali Ahmadi
- Proteomics Research Center, Faculty of Paramedical SciencesShahid Beheshti University of Medical Sciences Tehran Iran
| | - Mostafa Rezaei‐Tavirani
- Proteomics Research Center, Faculty of Paramedical SciencesShahid Beheshti University of Medical Sciences Tehran Iran
| | - Seyyedjavad SeyyedTabaei
- Department of Medical Parasitology and Mycology, School of MedicineShahid Beheshti University of Medical Sciences Tehran Iran
| | - Ali Haghighi
- Department of Medical Parasitology and Mycology, School of MedicineShahid Beheshti University of Medical Sciences Tehran Iran
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4
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Abstract
Intracellular trafficking of viruses and proteins commonly occurs via the early endosome in a process involving Rab5. The RNA Import Complex (RIC)-RNA complex is taken up by mammalian cells and targeted to mitochondria. Through RNA interference, it was shown that mito-targeting of the ribonucleoprotein (RNP) was dependent on caveolin 1 (Cav1), dynamin 2, Filamin A and NSF. Although a minor fraction of the RNP was transported to endosomes in a Rab5-dependent manner, mito-targeting was independent of Rab5 or other endosomal proteins, suggesting that endosomal uptake and mito-targeting occur independently. Sequential immunoprecipitation of the cytosolic vesicles showed the sorting of the RNP away from Cav1 in a process that was independent of the endosomal effector EEA1 but sensitive to nocodazole. However, the RNP was in two types of vesicle with or without Cav1, with membrane-bound, asymmetrically orientated RIC and entrapped RNA, but no endosomal components, suggesting vesicular sorting rather than escape of free RNP from endosomes. In vitro, RNP was directly transferred from the Type 2 vesicles to mitochondria. Live-cell imaging captured spherical Cav1− RNP vesicles emerging from the fission of large Cav+ particles. Thus, RNP appears to traffic by a different route than the classical Rab5-dependent pathway of viral transport.
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Affiliation(s)
- Joyita Mukherjee
- Genetic Engineering Laboratory, CSIR-Indian Institute of Chemical Biology, 4 Raja S. C. Mullick Road, Calcutta 700032, India Present address: Penn Institute for Regenerative Medicine, University of Pennsylvania, 3800 Spruce Street, Philadelphia, PA 19104, USA
| | - Biraj Mahato
- Present address: Penn Institute for Regenerative Medicine, University of Pennsylvania, 3800 Spruce Street, Philadelphia, PA 19104, USA
| | - Samit Adhya
- Genetic Engineering Laboratory, CSIR-Indian Institute of Chemical Biology, 4 Raja S. C. Mullick Road, Calcutta 700032, India Present address: Penn Institute for Regenerative Medicine, University of Pennsylvania, 3800 Spruce Street, Philadelphia, PA 19104, USA.
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5
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Koley S, Adhya S. A voltage-gated pore for translocation of tRNA. Biochem Biophys Res Commun 2013; 439:23-9. [PMID: 23958303 DOI: 10.1016/j.bbrc.2013.08.036] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2013] [Accepted: 08/10/2013] [Indexed: 10/26/2022]
Abstract
Very little is known about how nucleic acids are translocated across membranes. The multi-subunit RNA Import Complex (RIC) from mitochondria of the kinetoplastid protozoon Leishmania tropica induces translocation of tRNAs across artificial or natural membranes, but the nature of the translocation pore remains unknown. We show that subunits RIC6 and RIC9 assemble on the membrane in presence of subunit RIC4A to form complex R3. Atomic Force Microscopy of R3 revealed particles with an asymmetric surface groove of ∼20 nm rim diameter and ∼1 nm depth. R3 induced translocation of tRNA into liposomes when the pH of the medium was lowered to ∼6 in the absence of ATP. R3-mediated tRNA translocation could also be induced at neutral pH by a K(+) diffusion potential with an optimum of 60-70 mV. Point mutations in the Cys2-His2 Fe-binding motif of RIC6, which is homologous to the respiratory Complex III Fe-S protein, abrogated import induced by low pH but not by K(+) diffusion potential. These results indicate that the R3 complex forms a pore that is gated by a proton-generated membrane potential and that the Fe-S binding region of RIC6 has a role in proton translocation. The tRNA import complex of L. tropica thus contains a novel macromolecular channel distinct from the mitochondrial protein import pore that is apparently involved in tRNA import in some species.
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Affiliation(s)
- Sandip Koley
- Genetic Engineering Laboratory, Molecular and Human Genetics Division, CSIR-Indian Institute of Chemical Biology, 4 Raja S.C. Mullick Road, Calcutta 700 032, India
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6
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Rubio MAT, Hopper AK. Transfer RNA travels from the cytoplasm to organelles. WILEY INTERDISCIPLINARY REVIEWS-RNA 2011; 2:802-17. [PMID: 21976284 DOI: 10.1002/wrna.93] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Transfer RNAs (tRNAs) encoded by the nuclear genome are surprisingly dynamic. Although tRNAs function in protein synthesis occurring on cytoplasmic ribosomes, tRNAs can transit from the cytoplasm to the nucleus and then again return to the cytoplasm by a process known as the tRNA retrograde process. Subsets of the cytoplasmic tRNAs are also imported into mitochondria and function in mitochondrial protein synthesis. The numbers of tRNA species that are imported into mitochondria differ among organisms, ranging from just a few to the entire set needed to decode mitochondrially encoded mRNAs. For some tRNAs, import is dependent on the mitochondrial protein import machinery, whereas the majority of tRNA mitochondrial import is independent of this machinery. Although cytoplasmic proteins and proteins located on the mitochondrial surface participating in the tRNA import process have been described for several organisms, the identity of these proteins differ among organisms. Likewise, the tRNA determinants required for mitochondrial import differ among tRNA species and organisms. Here, we present an overview and discuss the current state of knowledge regarding the mechanisms involved in the tRNA retrograde process and continue with an overview of tRNA import into mitochondria. Finally, we highlight areas of future research to understand the function and regulation of movement of tRNAs between the cytoplasm and organelles.
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Affiliation(s)
- Mary Anne T Rubio
- Department of Microbiology and Center for RNA Biology, Ohio State University, Columbus, OH 43210, USA
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7
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RNA-mediated restoration of mitochondrial function in cells harboring a Kearns Sayre Syndrome mutation. Mitochondrion 2011; 11:564-74. [PMID: 21406250 DOI: 10.1016/j.mito.2011.03.006] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2010] [Accepted: 03/03/2011] [Indexed: 11/20/2022]
Abstract
Mutations in mitochondrial DNA (mtDNA) generate multi-system disorders due to failure of ATP production. A cybrid containing a 1.9-kb mtDNA deletion from a patient with Kearns Sayre Syndrome is respiration-defective and grows glycolytically. When treated with a ribonucleoprotein (RNP) complex of polycistronic RNA 1 (pcRNA1) containing mtDNA-encoded genes and a multi-subunit carrier complex R8, full-length pcRNA1 was transported to mitochondria. Translation of the pcRNA1-encoded mRNAs was observed in mitochondria from RNP-treated cells. Respiration of the cybrid was rescued to approximately 90% of normal within hours, switching the cells to aerobic growth. These findings have implications for the development of effective mitochondrial gene therapy.
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8
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Alfonzo JD, Söll D. Mitochondrial tRNA import--the challenge to understand has just begun. Biol Chem 2009; 390:717-22. [PMID: 19558325 DOI: 10.1515/bc.2009.101] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Mitochondrial translation is important for the synthesis of proteins involved in oxidative phosphorylation, which yields the bulk of the ATP made in cells. During evolution most mitochondria-containing organisms have lost tRNA genes from their mitochondrial genomes. Thus, to support the essential process of nuanced mitochondrial translation, mechanisms to actively transport tRNAs from the cytoplasm across the mitochondrial membranes into the mitochondrion have evolved. Here, we review the currently known tRNA import mechanisms, comment on recent discoveries of various import factors, and suggest a rationale for forces that lie behind the evolution of mitochondrial tRNA import.
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Affiliation(s)
- Juan D Alfonzo
- Department of Microbiology, Ohio State University Biochemistry Program and The Center for RNA Biology, The Ohio State University, Columbus, OH 43210-1292, USA.
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9
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Paris Z, Rubio MAT, Lukes J, Alfonzo JD. Mitochondrial tRNA import in Trypanosoma brucei is independent of thiolation and the Rieske protein. RNA (NEW YORK, N.Y.) 2009; 15:1398-1406. [PMID: 19465685 PMCID: PMC2704085 DOI: 10.1261/rna.1589109] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/05/2009] [Accepted: 04/13/2009] [Indexed: 05/27/2023]
Abstract
Due to a complete lack of the tRNA genes in the mitochondrial genome of Trypanosoma brucei, all tRNAs needed for mitochondrial translation have to be imported into the organelle from the cytosol. A previous study showed that the modified nucleotide s(2)U could act as a negative determinant for mitochondrial tRNA import in another kinetoplastid, Leishmania tarentolae. We have investigated whether the same type of cytosolic control for tRNA retention exists in T. brucei. Based on Northern analysis with subcellular RNA fractions and in vitro import assays, we demonstrate that silencing of the cysteine desulfurase, TbNfs (TbIscS), the key enzyme in tRNA thiolation (s(2)U) and Fe-S cluster formation in vivo, has no effect on tRNA partitioning. This observation is especially surprising in light of a recent report suggesting that in L. tropica the Rieske Fe-S protein is an essential component of the RNA import complex (RIC). In line with the above observation, we also show that down-regulation of the Rieske protein by RNA interference, similar to the TbNfs knockdowns, has no effect on import. The data presented here supports the view that in T. brucei: (1) s(2)U is not a negative determinant for tRNA import; (2) the Rieske protein is not an essential component of the import machinery, and (3) since the Rieske protein is essential for respiration and maintenance of inner mitochondrial membrane potential, neither process plays a critical role in tRNA import. We therefore suggest that the T. brucei import machinery differs substantially from what has been described in Leishmania.
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Affiliation(s)
- Zdenek Paris
- Biology Centre, Institute of Parasitology, Czech Academy of Sciences, 37005 Ceské Budejovice (Budweis), Czech Republic
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10
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Basu S, Mukherjee S, Adhya S. Proton-guided movements of tRNA within the Leishmania mitochondrial RNA import complex. Nucleic Acids Res 2008; 36:1599-609. [PMID: 18250088 PMCID: PMC2275131 DOI: 10.1093/nar/gkn010] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The RNA import complex (RIC) from the mitochondrion of the kinetoplastid protozoan Leishmania tropica contains two subunits that directly bind to import signals on two distinct subsets of tRNA and interact with each other allosterically. What happens to the tRNA subsequent to its loading on the complex is unknown. A third subunit-RIC9-has intrinsic affinity for both types of tRNA and is essential for import in vivo. Here we show that antibody against RIC9 inhibited the import of both types of tRNA into mitoplasts in vitro, but failed to inhibit the binding of these tRNAs to their respective receptors, indicating that RIC9 acts in a subsequent step. Using photoaffinity crosslinking-immunoprecipitation to detect translocation intermediates, it was observed that tRNA was transferred from its cognate receptor to RIC9, followed by translocation across the membrane and release as free tRNA in the inner compartment. Transfer required elevated temperatures and ATP, but ATP was substituted by acid pH. These tRNA movements were sensitive to uncouplers and inhibitors, suggesting distinct roles of the electrical and chemical components of the proton motive force generated by vectorial proton translocation accompanying ATP hydrolysis. By analysis of partially assembled complexes in L. tropica depleted of various subunits, and in vitro assembly assays, RIC9 was shown to make stable contacts with RIC8A, a tRNA receptor and RIC6, a membrane-embedded component. The results have implications for the mechanism of tRNA import.
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Affiliation(s)
- Sudarshana Basu
- Genetic Engineering Laboratory, Indian Institute of Chemical Biology, 4 Raja S. C. Mullick Road, Calcutta 700 032, India
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11
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Adhya S. Leishmania mitochondrial tRNA importers. Int J Biochem Cell Biol 2007; 40:2681-5. [PMID: 18061510 DOI: 10.1016/j.biocel.2007.10.025] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2007] [Revised: 10/15/2007] [Accepted: 10/16/2007] [Indexed: 11/28/2022]
Abstract
The RNA Import Complex (RIC) is a multi-subunit protein complex from the mitochondria of the kinetoplastid protozoon Leishmania tropica that induces transport of tRNA across natural and artificial membranes. Leishmania, Trypanosoma and related genera of the order Kinetoplastidae are early diverging, atypical eukaryotes with unique RNA metabolic pathways, including the import of nucleus-encoded tRNAs into the mitochondrion to complement the deletion of all organelle-encoded tRNA genes. Biochemical and genetic studies of RIC are contributing to greater understanding of the mechanism of import. Additionally, RIC was shown to act as an efficient delivery vehicle for tRNA and other small RNAs into mitochondria within intact mammalian cells, indicating its applicability to the management of diseases caused by mitochondrial mutations.
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Affiliation(s)
- Samit Adhya
- Genetic Engineering Laboratory, Division of Molecular and Human Genetics, Indian Institute of Chemical Biology, 4 Raja S.C. Mullick Road, Calcutta 700032, India.
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12
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Kamenski PA, Vinogradova EN, Krasheninnikov IA, Tarassov IA. Directed import of macromolecules into mitochondria. Mol Biol 2007. [DOI: 10.1134/s0026893307020021] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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13
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Chatterjee S, Home P, Mukherjee S, Mahata B, Goswami S, Dhar G, Adhya S. An RNA-binding respiratory component mediates import of type II tRNAs into Leishmania mitochondria. J Biol Chem 2006; 281:25270-7. [PMID: 16825195 DOI: 10.1074/jbc.m604126200] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Transport of tRNAs across the inner mitochondrial membrane of the kinetoplastid protozoon Leishmania requires interactions with specific binding proteins (receptors) in a multi-subunit complex. The allosteric model of import regulation proposes cooperative and antagonistic interactions between two or more receptors with binding specificities for distinct tRNA families (types I and II, respectively). To identify the type II receptor, the gene encoding RIC8A, a subunit of the complex, was cloned. The C-terminal region of RIC8A is homologous to subunit 6b of ubiquinol cytochrome c reductase (respiratory complex III), while the N-terminal region has intrinsic affinity for type II, but not for type I, tRNAs. RIC8A is shared by the import complex and complex III, indicating its bi-functionality, but is assembled differently in the two complexes. Knockdown of RIC8A in Leishmania lowered the mitochondrial content of type II tRNAs but raised that of type I tRNAs, with downstream effects on mitochondrial translation and respiration, and cell death. In RIC8A knockdown cells, a subcomplex was formed that interacted with type I tRNA, but the negative regulation by type II tRNA was lost. Mitochondrial extracts from these cells were defective for type II, but not type I, import; import and regulation were restored by purified RIC8A. These results provide evidence for the relevance of allosteric regulation in vivo and indicate that acquisition of new tRNA-binding domains by ancient respiratory components have played a key role in the evolution of mitochondrial tRNA import.
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Affiliation(s)
- Saibal Chatterjee
- Genetic Engineering Laboratory, Indian Institute of Chemical Biology, Calcutta 700032, India
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14
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Goswami S, Adhya S. The alpha-subunit of Leishmania F1 ATP synthase hydrolyzes ATP in presence of tRNA. J Biol Chem 2006; 281:18914-7. [PMID: 16735512 DOI: 10.1074/jbc.c600089200] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Import of tRNAs into the mitochondria of the kinetoplastid protozoon Leishmania requires the tRNA-dependent hydrolysis of ATP leading to the generation of membrane potential through the pumping of protons. Subunit RIC1 of the inner membrane RNA import complex is a bi-functional protein that is identical to the alpha-subunit of F1F0 ATP synthase and specifically binds to a subset (Type I) of importable tRNAs. We show that recombinant, purified RIC1 is a Type I tRNA-dependent ATP hydrolase. The activity was insensitive to oligomycin, sensitive to mutations within the import signal of the tRNA, and required the cooperative interaction between the ATP-binding and C-terminal domains of RIC1. The ATPase activity of the intact complex was inhibited by anti-RIC1 antibody, while knockdown of RIC1 in Leishmania tropica resulted in deficiency of the tRNA-dependent ATPase activity of the mitochondrial inner membrane. Moreover, RIC1 knockdown extracts failed to generate a membrane potential across reconstituted proteoliposomes, as shown by a rhodamine 123 uptake assay, but activity was restored by adding back purified RIC1. These observations identify RIC1 as a novel form of the F1 ATP synthase alpha-subunit that acts as the major energy transducer for tRNA import.
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Affiliation(s)
- Srikanta Goswami
- Genetic Engineering Laboratory, Indian Institute of Chemical Biology, 4 Raja S.C. Mullick Road, Calcutta 700032, India
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15
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Goswami S, Dhar G, Mukherjee S, Mahata B, Chatterjee S, Home P, Adhya S. A bifunctional tRNA import receptor from Leishmania mitochondria. Proc Natl Acad Sci U S A 2006; 103:8354-9. [PMID: 16714384 PMCID: PMC1482498 DOI: 10.1073/pnas.0510869103] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
In kinetoplastid protozoa, import of cytosolic tRNAs into mitochondria occurs through tRNAs interacting with membrane-bound proteins, the identities of which are unknown. The inner membrane RNA import complex of Leishmania tropica contains multiple proteins and is active for import in vitro. RIC1, the largest subunit of this complex, is structurally homologous to the conserved alpha subunit of F1 ATP synthase. The RIC1 gene complemented an atpA mutation in Escherichia coli. Antisense-mediated knockdown of RIC1/F1alpha in Leishmania resulted in depletion of several mitochondrial tRNAs belonging to distinct subsets (types I and II) that interact cooperatively or antagonistically within the import complex. The knockdown-induced defect in import of type I tRNAs was rectified in a reconstituted system by purified RIC1/F1alpha alone, but recovery of type II tRNA import additionally required a type I tRNA. RIC1/F1alpha formed stable complexes with type I, but not type II, tRNAs through the cooperation of its nucleotide binding and C-terminal domains. Thus, RIC1/F1alpha is a type I tRNA import receptor. As expected of a bifunctional protein, RIC1/F1alpha is shared by both the import complex and by respiratory complex V. Alternative use of ancient respiratory proteins may have been an important step in the evolution of tRNA import.
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Affiliation(s)
- Srikanta Goswami
- Genetic Engineering Laboratory, Indian Institute of Chemical Biology, 4 Raja S.C. Mullick Road, Calcutta 700032, India
| | - Gunjan Dhar
- Genetic Engineering Laboratory, Indian Institute of Chemical Biology, 4 Raja S.C. Mullick Road, Calcutta 700032, India
| | - Saikat Mukherjee
- Genetic Engineering Laboratory, Indian Institute of Chemical Biology, 4 Raja S.C. Mullick Road, Calcutta 700032, India
| | - Bidesh Mahata
- Genetic Engineering Laboratory, Indian Institute of Chemical Biology, 4 Raja S.C. Mullick Road, Calcutta 700032, India
| | - Saibal Chatterjee
- Genetic Engineering Laboratory, Indian Institute of Chemical Biology, 4 Raja S.C. Mullick Road, Calcutta 700032, India
| | - Pratik Home
- Genetic Engineering Laboratory, Indian Institute of Chemical Biology, 4 Raja S.C. Mullick Road, Calcutta 700032, India
| | - Samit Adhya
- Genetic Engineering Laboratory, Indian Institute of Chemical Biology, 4 Raja S.C. Mullick Road, Calcutta 700032, India
- *To whom correspondence should be addressed. E-mail:
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16
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Mahata B, Bhattacharyya SN, Mukherjee S, Adhya S. Correction of translational defects in patient-derived mutant mitochondria by complex-mediated import of a cytoplasmic tRNA. J Biol Chem 2004; 280:5141-4. [PMID: 15619607 DOI: 10.1074/jbc.c400572200] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
A variety of clinical disorders result from mutations in mitochondrial tRNA genes, leading to translational defects. We show here that a protein complex from the kinetoplastid protozoon Leishmania induces specific, ATP-dependent import of human cytoplasmic tRNA(1)(Lys) into human mitochondria in vitro. The imported tRNA undergoes efficient aminoacylation within the organelle and supports organellar protein synthesis. Moreover, translation in mitochondria from patients with myclonic epilepsy with ragged red fibers (MERRF) and Kearns-Sayre syndrome (KSS), containing mutant tRNA(Lys) genes, is stimulated to near-wild-type levels and the formation of aberrant polypeptides suppressed by complex-mediated import. These results suggest a novel way to introduce RNAs for the modulation of mitochondrial gene expression.
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Affiliation(s)
- Bidesh Mahata
- Genetic Engineering Laboratory, Indian Institute of Chemical Biology, 4 Raja S. C. Mullick Road, Calcutta 7000032, India
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