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Dhembla C, Kumar A, Arya R, Kundu S, Sundd M. Mitochondrial Acyl Carrier Protein of Leishmania major Displays Features Distinct from the Canonical Type II ACP. Biochemistry 2023; 62:3347-3359. [PMID: 37967383 DOI: 10.1021/acs.biochem.3c00455] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2023]
Abstract
Prokaryotes synthesize fatty acids using a type II synthesis pathway (FAS). In this process, the central player, i.e., the acyl carrier protein (ACP), sequesters the growing acyl chain in its internal hydrophobic cavity. As the acyl chain length increases, the cavity expands in size, which is reflected in the NMR chemical shift perturbations and crystal structures of the acyl-ACP intermediates. A few eukaryotic organelles, such as plastids and mitochondria, also harbor type II fatty acid synthesis machinery. Plastid FAS from spinach and Plasmodium falciparum has been characterized at the molecular level, but the mitochondrial pathway remains unexplored. Here, we report NMR studies of the mitochondrial acyl-acyl carrier protein intermediates of Leishmania major (acyl-LmACP). Our studies show that LmACP experiences remarkably small conformational changes upon acylation, with perturbations confined to helices II and III only. CastP determined that the cavity size of apo-LmACP (PDB entry 5ZWT) is less than that of Escherichia coli ACP (PDB 1T8K). Thus, the small chemical shift perturbations observed in the LmACP intermediates, coupled with CastP results, suggest an unusually small cavity when fully expanded. The faster rate of C8-LmACP chain hydrolysis compared to E. coli ACP (EcACP) also supports these convictions. Structure comparison of LmACP with other type II ACP disclosed unique differences in the helix I and loop I conformations, as well as several residues present there. Numerous hydrophobic residues in helix I and loop I (conserved in all mitochondrial ACPs) are substituted with hydrophilic residues in the bacterial/plastid type II ACP. For instance, Phe and leucine at positions 14 and 34 in LmACP are substituted with a hydrophilic residue and Ala in bacterial/plastid type II ACP. Mutation of Leu 34 to Ala (corresponding residue in EcACP) resulted in a complete loss of structure, underscoring its importance in maintaining the ACP fold. Thus, our NMR studies, combined with insights from the crystal structure, highlight several unique features of LmACP, distinct from the prokaryote and plastid type II ACP. Given the high sequence identity, the features might be conserved in all mitochondrial ACPs.
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Affiliation(s)
- Chetna Dhembla
- Department of Biochemistry, University of Delhi South Campus, Benito Juarez Road, New Delhi 110 021, India
| | - Ambrish Kumar
- National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi 110 067, India
| | - Richa Arya
- Department of Biochemistry, University of Delhi South Campus, Benito Juarez Road, New Delhi 110 021, India
| | - Suman Kundu
- Department of Biochemistry, University of Delhi South Campus, Benito Juarez Road, New Delhi 110 021, India
| | - Monica Sundd
- National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi 110 067, India
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2
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Miller JC, Delzell SB, Concepción-Acevedo J, Boucher MJ, Klingbeil MM. A DNA polymerization-independent role for mitochondrial DNA polymerase I-like protein C in African trypanosomes. J Cell Sci 2020; 133:jcs.233072. [PMID: 32079654 DOI: 10.1242/jcs.233072] [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: 08/08/2019] [Accepted: 02/10/2020] [Indexed: 01/01/2023] Open
Abstract
Mitochondrial DNA of Trypanosoma brucei and related parasites is a catenated network containing thousands of minicircles and tens of maxicircles, called kinetoplast DNA (kDNA). Replication of a single nucleoid requires at least three DNA polymerase I-like proteins (i.e. POLIB, POLIC and POLID), each showing discrete localizations near the kDNA during S phase. POLIB and POLID have roles in minicircle replication but the specific role of POLIC in kDNA maintenance is less clear. Here, we use an RNA interference (RNAi)-complementation system to dissect the functions of two distinct POLIC regions, i.e. the conserved family A DNA polymerase (POLA) domain and the uncharacterized N-terminal region (UCR). While RNAi complementation with wild-type POLIC restored kDNA content and cell cycle localization of kDNA, active site point mutations in the POLA domain impaired minicircle replication similar to that of POLIB and POLID depletions. Complementation with POLA domain alone abolished the formation of POLIC foci and partially rescued the RNAi phenotype. Furthermore, we provide evidence that the UCR is crucial in cell cycle-dependent protein localization and facilitates proper distribution of progeny networks. This is the first report of a DNA polymerase that impacts on mitochondrial nucleoid distribution.This article has an associated First Person interview with the first author of the paper.
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Affiliation(s)
- Jonathan C Miller
- Department of Microbiology, University of Massachusetts, Amherst, MA 01003, USA
| | - Stephanie B Delzell
- Department of Microbiology, University of Massachusetts, Amherst, MA 01003, USA
| | - Jeniffer Concepción-Acevedo
- Centers for Disease Control and Prevention, National Center for Emerging and Zoonotic Infectious Diseases, 1600 Clifton Road, Atlanta, GA 30329, USA
| | - Michael J Boucher
- Department of Biochemistry and Biophysics, University of California San Francisco, San Francisco, CA 94158, USA
| | - Michele M Klingbeil
- Department of Microbiology, University of Massachusetts, Amherst, MA 01003, USA .,Division of Foodborne,Waterborne, and Environmental Diseases, The Institute of Applied Life Sciences, University of Massachusetts, Amherst, MA 01003, USA
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3
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Mensa-Wilmot K, Hoffman B, Wiedeman J, Sullenberger C, Sharma A. Kinetoplast Division Factors in a Trypanosome. Trends Parasitol 2019; 35:119-128. [PMID: 30638954 DOI: 10.1016/j.pt.2018.11.002] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2018] [Revised: 11/06/2018] [Accepted: 11/11/2018] [Indexed: 02/08/2023]
Abstract
Inheritance of the single mitochondrial nucleoid (kinetoplast) in the trypanosome requires numerous proteins, many of whose precise roles are unclear. By considering kinetoplast DNA (kDNA) as a template for cleavage into two equal-size networks, we predicted sets of mutant kinetoplasts associated with defects in each of the five steps in the kinetoplast cycle. Comparison of these kinetoplasts with those obtained after gene knockdowns enabled assignment of proteins to five classes - kDNA synthesis, site of scission selection, scission, separation, and partitioning. These studies highlight how analysis of mutant kinetoplast phenotypes may be used to predict functional categories of proteins involved in the biogenesis of kinetoplasts.
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Affiliation(s)
- Kojo Mensa-Wilmot
- Department of Cellular Biology, 724 Biological Sciences Building, University of Georgia, Athens, Georgia 30602, USA; Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, Georgia 30602, USA.
| | - Benjamin Hoffman
- Department of Cellular Biology, 724 Biological Sciences Building, University of Georgia, Athens, Georgia 30602, USA; Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, Georgia 30602, USA
| | - Justin Wiedeman
- Department of Cellular Biology, 724 Biological Sciences Building, University of Georgia, Athens, Georgia 30602, USA; Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, Georgia 30602, USA
| | - Catherine Sullenberger
- Department of Cellular Biology, 724 Biological Sciences Building, University of Georgia, Athens, Georgia 30602, USA
| | - Amrita Sharma
- Department of Cellular Biology, 724 Biological Sciences Building, University of Georgia, Athens, Georgia 30602, USA; Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, Georgia 30602, USA
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Schneider A, Ochsenreiter T. Failure is not an option - mitochondrial genome segregation in trypanosomes. J Cell Sci 2018; 131:131/18/jcs221820. [PMID: 30224426 DOI: 10.1242/jcs.221820] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Unlike most other model eukaryotes, Trypanosoma brucei and its relatives have a single mitochondrion with a single-unit mitochondrial genome that is termed kinetoplast DNA (kDNA). Replication of the kDNA is coordinated with the cell cycle. During binary mitochondrial fission and prior to cytokinesis, the replicated kDNA has to be faithfully segregated to the daughter organelles. This process depends on the tripartite attachment complex (TAC) that physically links the kDNA across the two mitochondrial membranes with the basal body of the flagellum. Thus, the TAC couples segregation of the replicated kDNA with segregation of the basal bodies of the old and the new flagellum. In this Review, we provide an overview of the role of the TAC in kDNA inheritance in T. brucei We focus on recent advances regarding the molecular composition of the TAC, and discuss how the TAC is assembled and how its subunits are targeted to their respective TAC subdomains. Finally, we will contrast the segregation of the single-unit kDNA in trypanosomes to mitochondrial genome inheritance in yeast and mammals, both of which have numerous mitochondria that each contain multiple genomes.
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Affiliation(s)
- André Schneider
- Department of Chemistry and Biochemistry, University of Bern, Freiestr. 3, CH-3012 Bern, Switzerland
| | - Torsten Ochsenreiter
- Institute of Cell Biology, University of Bern, Baltzerstrasse 4, Bern CH-3012, Switzerland
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Molecular model of the mitochondrial genome segregation machinery in Trypanosoma brucei. Proc Natl Acad Sci U S A 2018; 115:E1809-E1818. [PMID: 29434039 PMCID: PMC5828607 DOI: 10.1073/pnas.1716582115] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Mitochondrial genome replication and segregation are essential processes in most eukaryotic cells. While replication has been studied in some detail, much less is known about the molecular machinery required to distribute the replicated genomes. Using superresolution microscopy in combination with molecular biology and biochemistry, we show in which order the segregation machinery is assembled and that it is likely assembled de novo rather than in a semiconservative fashion in the single-celled parasite Trypanosoma brucei. Furthermore, we demonstrate that the mitochondrial genome itself is not required for assembly to occur. It seems that the physical connection of the mitochondrial genome to cytoskeletal elements is a conserved feature in most eukaryotes; however, the molecular components are highly diverse. In almost all eukaryotes, mitochondria maintain their own genome. Despite the discovery more than 50 y ago, still very little is known about how the genome is correctly segregated during cell division. The protozoan parasite Trypanosoma brucei contains a single mitochondrion with a singular genome, the kinetoplast DNA (kDNA). Electron microscopy studies revealed the tripartite attachment complex (TAC) to physically connect the kDNA to the basal body of the flagellum and to ensure correct segregation of the mitochondrial genome via the basal bodies movement, during the cell cycle. Using superresolution microscopy, we precisely localize each of the currently known TAC components. We demonstrate that the TAC is assembled in a hierarchical order from the base of the flagellum toward the mitochondrial genome and that the assembly is not dependent on the kDNA itself. Based on the biochemical analysis, the TAC consists of several nonoverlapping subcomplexes, suggesting an overall size of the TAC exceeding 2.8 mDa. We furthermore demonstrate that the TAC is required for correct mitochondrial organelle positioning but not for organelle biogenesis or segregation.
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TAC102 Is a Novel Component of the Mitochondrial Genome Segregation Machinery in Trypanosomes. PLoS Pathog 2016; 12:e1005586. [PMID: 27168148 PMCID: PMC4864229 DOI: 10.1371/journal.ppat.1005586] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2015] [Accepted: 03/30/2016] [Indexed: 11/19/2022] Open
Abstract
Trypanosomes show an intriguing organization of their mitochondrial DNA into a catenated network, the kinetoplast DNA (kDNA). While more than 30 proteins involved in kDNA replication have been described, only few components of kDNA segregation machinery are currently known. Electron microscopy studies identified a high-order structure, the tripartite attachment complex (TAC), linking the basal body of the flagellum via the mitochondrial membranes to the kDNA. Here we describe TAC102, a novel core component of the TAC, which is essential for proper kDNA segregation during cell division. Loss of TAC102 leads to mitochondrial genome missegregation but has no impact on proper organelle biogenesis and segregation. The protein is present throughout the cell cycle and is assembled into the newly developing TAC only after the pro-basal body has matured indicating a hierarchy in the assembly process. Furthermore, we provide evidence that the TAC is replicated de novo rather than using a semi-conservative mechanism. Lastly, we demonstrate that TAC102 lacks an N-terminal mitochondrial targeting sequence and requires sequences in the C-terminal part of the protein for its proper localization. Proper segregation of the mitochondrial genome during cell division is a prerequisite of healthy eukaryotic cells. However, the mechanism underlying the segregation process is only poorly understood. We use the single celled parasite Trypanosoma brucei, which, unlike most model organisms, harbors a single large mitochondrion with a single mitochondrial genome, also called kinetoplast DNA (kDNA), to study this question. In trypanosomes, kDNA replication and segregation are tightly integrated into the cell cycle and thus can be studied alongside cell cycle markers. Furthermore, previous studies using electron microscopy have characterized the tripartite attachment complex (TAC) as a structural element of the mitochondrial genome segregation machinery. Here, we characterize TAC102, a novel trypanosome protein localized to the TAC. The protein is essential for proper kDNA segregation and cell growth. We analyze the presence of this protein using super resolution microscopy and show that TAC102 is a mitochondrial protein localized between the kDNA and the basal body of the cell’s flagellum. In addition, we characterize different parts of the protein and show that the C-terminus of TAC102 is important for its proper localization. The data and resources presented will allow a more detailed characterization of the dynamics and hierarchy of the TAC in the future and might open new avenues for drug discovery targeting this structure.
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7
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Grewal JS, McLuskey K, Das D, Myburgh E, Wilkes J, Brown E, Lemgruber L, Gould MK, Burchmore RJ, Coombs GH, Schnaufer A, Mottram JC. PNT1 Is a C11 Cysteine Peptidase Essential for Replication of the Trypanosome Kinetoplast. J Biol Chem 2016; 291:9492-500. [PMID: 26940875 PMCID: PMC4850289 DOI: 10.1074/jbc.m116.714972] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2016] [Indexed: 11/16/2022] Open
Abstract
The structure of a C11 peptidase PmC11 from the gut bacterium, Parabacteroides merdae, has recently been determined, enabling the identification and characterization of a C11 orthologue, PNT1, in the parasitic protozoon Trypanosoma brucei. A phylogenetic analysis identified PmC11 orthologues in bacteria, archaea, Chromerids, Coccidia, and Kinetoplastida, the latter being the most divergent. A primary sequence alignment of PNT1 with clostripain and PmC11 revealed the position of the characteristic His-Cys catalytic dyad (His99 and Cys136), and an Asp (Asp134) in the potential S1 binding site. Immunofluorescence and cryoelectron microscopy revealed that PNT1 localizes to the kinetoplast, an organelle containing the mitochondrial genome of the parasite (kDNA), with an accumulation of the protein at or near the antipodal sites. Depletion of PNT1 by RNAi in the T. brucei bloodstream form was lethal both in in vitro culture and in vivo in mice and the induced population accumulated cells lacking a kinetoplast. In contrast, overexpression of PNT1 led to cells having mislocated kinetoplasts. RNAi depletion of PNT1 in a kDNA independent cell line resulted in kinetoplast loss but was viable, indicating that PNT1 is required exclusively for kinetoplast maintenance. Expression of a recoded wild-type PNT1 allele, but not of an active site mutant restored parasite viability after induction in vitro and in vivo confirming that the peptidase activity of PNT1 is essential for parasite survival. These data provide evidence that PNT1 is a cysteine peptidase that is required exclusively for maintenance of the trypanosome kinetoplast.
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Affiliation(s)
- Jaspreet S Grewal
- From the Wellcome Trust Centre for Molecular Parasitology, Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8TA, United Kingdom, the Department of Biology, Centre for Immunology and Infection, University of York, Wentworth Way, Heslington, York YO10 5DD, United Kingdom
| | - Karen McLuskey
- From the Wellcome Trust Centre for Molecular Parasitology, Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8TA, United Kingdom
| | - Debanu Das
- the Joint Center for Structural Genomics, Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, California 94025
| | - Elmarie Myburgh
- From the Wellcome Trust Centre for Molecular Parasitology, Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8TA, United Kingdom, the Department of Biology, Centre for Immunology and Infection, University of York, Wentworth Way, Heslington, York YO10 5DD, United Kingdom
| | - Jonathan Wilkes
- From the Wellcome Trust Centre for Molecular Parasitology, Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8TA, United Kingdom
| | - Elaine Brown
- From the Wellcome Trust Centre for Molecular Parasitology, Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8TA, United Kingdom, the Department of Biology, Centre for Immunology and Infection, University of York, Wentworth Way, Heslington, York YO10 5DD, United Kingdom
| | - Leandro Lemgruber
- From the Wellcome Trust Centre for Molecular Parasitology, Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8TA, United Kingdom
| | - Matthew K Gould
- the Institute of Immunology and Infection Research and Centre for Immunity, Infection, and Evolution, University of Edinburgh, Edinburgh EH9 3FL, United Kingdom
| | - Richard J Burchmore
- From the Wellcome Trust Centre for Molecular Parasitology, Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8TA, United Kingdom
| | - Graham H Coombs
- the Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow G4 0RE, United Kingdom
| | - Achim Schnaufer
- the Institute of Immunology and Infection Research and Centre for Immunity, Infection, and Evolution, University of Edinburgh, Edinburgh EH9 3FL, United Kingdom
| | - Jeremy C Mottram
- From the Wellcome Trust Centre for Molecular Parasitology, Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8TA, United Kingdom, the Department of Biology, Centre for Immunology and Infection, University of York, Wentworth Way, Heslington, York YO10 5DD, United Kingdom,
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8
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Matthews KR. 25 years of African trypanosome research: From description to molecular dissection and new drug discovery. Mol Biochem Parasitol 2015; 200:30-40. [PMID: 25736427 PMCID: PMC4509711 DOI: 10.1016/j.molbiopara.2015.01.006] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2014] [Revised: 01/09/2015] [Accepted: 01/13/2015] [Indexed: 01/27/2023]
Abstract
The Molecular Parasitology conference was first held at the Marine Biological laboratory, Woods Hole, USA 25 years ago. Since that first meeting, the conference has evolved and expanded but has remained the showcase for the latest research developments in molecular parasitology. In this perspective, I reflect on the scientific discoveries focussed on African trypanosomes (Trypanosoma brucei spp.) that have occurred since the inaugural MPM meeting and discuss the current and future status of research on these parasites.
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Affiliation(s)
- Keith R Matthews
- Centre for Immunity, Infection and Evolution, Institute for Immunology and Infection Research, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3JT, UK.
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9
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Uttaro AD. Acquisition and biosynthesis of saturated and unsaturated fatty acids by trypanosomatids. Mol Biochem Parasitol 2014; 196:61-70. [DOI: 10.1016/j.molbiopara.2014.04.001] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2013] [Revised: 03/28/2014] [Accepted: 04/01/2014] [Indexed: 12/21/2022]
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Duarte M, Tomás AM. The mitochondrial complex I of trypanosomatids--an overview of current knowledge. J Bioenerg Biomembr 2014; 46:299-311. [PMID: 24961227 DOI: 10.1007/s10863-014-9556-x] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2014] [Accepted: 06/17/2014] [Indexed: 01/23/2023]
Abstract
The contribution of trypanosomatid mitochondrial complex I for energy transduction has long been debated. Herein, we summarize current knowledge on the composition and relevance of this enzyme. Bioinformatic and proteomic analyses allowed the identification of many conserved and trypanosomatid-specific subunits of NADH:ubiquinone oxidoreductase, revealing a multifunctional enzyme capable of performing bioenergetic activities and possibly, also of functioning in fatty acid metabolism. A multimeric structure organized in 5 domains of more than 2 MDa is predicted, in contrast to the 1 MDa described for mammalian complex I. The relevance of mitochondrial complex I within the Trypanosomatidae family is quite diverse with its NADH oxidation activity being dispensable for both procyclic and bloodstream Trypanosoma brucei, whereas in Phytomonas serpens the enzyme is the only respiratory complex able to sustain membrane potential. Aside from complex I, trypanosomatid mitochondria contain a type II NADH dehydrogenase and a NADH-dependent fumarate reductase as alternative electron entry points into the respiratory chain and thus, some trypanosomatids may have bypassed the need for complex I. The involvement of each of these enzymes in the maintenance of the mitochondrial redox balance in trypanosomatids is still an open question and requires further investigation.
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Affiliation(s)
- Margarida Duarte
- IBMC - Instituto de Biologia Molecular e Celular, Universidade do Porto, Rua do Campo Alegre 823, 4150-180, Porto, Portugal,
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11
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Povelones ML. Beyond replication: division and segregation of mitochondrial DNA in kinetoplastids. Mol Biochem Parasitol 2014; 196:53-60. [PMID: 24704441 DOI: 10.1016/j.molbiopara.2014.03.008] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2014] [Revised: 03/18/2014] [Accepted: 03/25/2014] [Indexed: 11/29/2022]
Abstract
The mitochondrial genome of kinetoplastids, called kinetoplast DNA (kDNA) is a complex structure that must be faithfully duplicated exactly once per cell cycle. Despite many years of thorough investigation into the kDNA replication mechanism, many of the molecular details of the later stages of the process, particularly kDNA division and segregation, remain mysterious. In addition, perturbation of several cellular activities, some only indirectly related to kDNA, can lead to asymmetric kDNA division and other segregation defects. This review will examine unifying features and possible explanations for these phenotypes in the context of current models for kDNA division and segregation.
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Kovárová J, Horáková E, Changmai P, Vancová M, Lukeš J. Mitochondrial and nucleolar localization of cysteine desulfurase Nfs and the scaffold protein Isu in Trypanosoma brucei. EUKARYOTIC CELL 2014; 13:353-62. [PMID: 24243795 PMCID: PMC3957590 DOI: 10.1128/ec.00235-13] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/05/2013] [Accepted: 11/12/2013] [Indexed: 01/09/2023]
Abstract
Trypanosoma brucei has a complex life cycle during which its single mitochondrion is subjected to major metabolic and morphological changes. While the procyclic stage (PS) of the insect vector contains a large and reticulated mitochondrion, its counterpart in the bloodstream stage (BS) parasitizing mammals is highly reduced and seems to be devoid of most functions. We show here that key Fe-S cluster assembly proteins are still present and active in this organelle and that produced clusters are incorporated into overexpressed enzymes. Importantly, the cysteine desulfurase Nfs, equipped with the nuclear localization signal, was detected in the nucleolus of both T. brucei life stages. The scaffold protein Isu, an interacting partner of Nfs, was also found to have a dual localization in the mitochondrion and the nucleolus, while frataxin and both ferredoxins are confined to the mitochondrion. Moreover, upon depletion of Isu, cytosolic tRNA thiolation dropped in the PS but not BS parasites.
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Affiliation(s)
- Julie Kovárová
- Biology Center, Institute of Parasitology, Czech Academy of Sciences and Faculty of Sciences, University of South Bohemia, České Budějovice (Budweis), Czech Republic
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13
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Hashimi H, McDonald L, Stríbrná E, Lukeš J. Trypanosome Letm1 protein is essential for mitochondrial potassium homeostasis. J Biol Chem 2013; 288:26914-25. [PMID: 23893410 DOI: 10.1074/jbc.m113.495119] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Letm1 is a conserved protein in eukaryotes bearing energized mitochondria. Hemizygous deletion of its gene has been implicated in symptoms of the human disease Wolf-Hirschhorn syndrome. Studies almost exclusively performed in opisthokonts have attributed several roles to Letm1, including maintaining mitochondrial morphology, mediating either calcium or potassium/proton antiport, and facilitating mitochondrial translation. We address the ancestral function of Letm1 in the highly diverged protist and significant pathogen, Trypanosoma brucei. We demonstrate that Letm1 is involved in maintaining mitochondrial volume via potassium/proton exchange across the inner membrane. This role is essential in the vector-dwelling procyclic and mammal-infecting bloodstream stages as well as in Trypanosoma brucei evansi, a form of the latter stage lacking an organellar genome. In the pathogenic bloodstream stage, the mitochondrion consumes ATP to maintain an energized state, whereas that of T. brucei evansi also lacks a conventional proton-driven membrane potential. Thus, Letm1 performs its function in different physiological states, suggesting that ion homeostasis is among the few characterized essential pathways of the mitochondrion at this T. brucei life stage. Interestingly, Letm1 depletion in the procyclic stage can be complemented by exogenous expression of its human counterpart, highlighting the conservation of protein function between highly divergent species. Furthermore, although mitochondrial translation is affected upon Letm1 ablation, it is an indirect consequence of K(+) accumulation in the matrix.
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Affiliation(s)
- Hassan Hashimi
- From the Institute of Parasitology, Biology Centre, Czech Academy of Sciences and
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14
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Lipid synthesis in protozoan parasites: a comparison between kinetoplastids and apicomplexans. Prog Lipid Res 2013; 52:488-512. [PMID: 23827884 DOI: 10.1016/j.plipres.2013.06.003] [Citation(s) in RCA: 103] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2013] [Revised: 06/16/2013] [Accepted: 06/17/2013] [Indexed: 12/22/2022]
Abstract
Lipid metabolism is of crucial importance for pathogens. Lipids serve as cellular building blocks, signalling molecules, energy stores, posttranslational modifiers, and pathogenesis factors. Parasites rely on a complex system of uptake and synthesis mechanisms to satisfy their lipid needs. The parameters of this system change dramatically as the parasite transits through the various stages of its life cycle. Here we discuss the tremendous recent advances that have been made in the understanding of the synthesis and uptake pathways for fatty acids and phospholipids in apicomplexan and kinetoplastid parasites, including Plasmodium, Toxoplasma, Cryptosporidium, Trypanosoma and Leishmania. Lipid synthesis differs in significant ways between parasites from both phyla and the human host. Parasites have acquired novel pathways through endosymbiosis, as in the case of the apicoplast, have dramatically reshaped substrate and product profiles, and have evolved specialized lipids to interact with or manipulate the host. These differences potentially provide opportunities for drug development. We outline the lipid pathways for key species in detail as they progress through the developmental cycle and highlight those that are of particular importance to the biology of the pathogens and/or are the most promising targets for parasite-specific treatment.
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15
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Povelones ML, Tiengwe C, Gluenz E, Gull K, Englund PT, Jensen RE. Mitochondrial shape and function in trypanosomes requires the outer membrane protein, TbLOK1. Mol Microbiol 2013; 87:713-29. [PMID: 23336702 DOI: 10.1111/mmi.12089] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/03/2012] [Indexed: 01/01/2023]
Abstract
In an RNAi library screen for loss of kinetoplast DNA (kDNA), we identified an uncharacterized Trypanosoma brucei protein, named TbLOK1, required for maintenance of mitochondrial shape and function. We found the TbLOK1 protein located in discrete patches in the mitochondrial outer membrane. Knock-down of TbLOK1 in procyclic trypanosomes caused the highly interconnected mitochondrial structure to collapse, forming an unbranched tubule remarkably similar to the streamlined organelle seen in the bloodstream form. Following RNAi, defects in mitochondrial respiration, inner membrane potential and mitochondrial transcription were observed. At later times following TbLOK1 depletion, kDNA was lost and a more drastic alteration in mitochondrial structure was found. Our results demonstrate the close relationship between organelle structure and function in trypanosomes.
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Affiliation(s)
- Megan L Povelones
- Department of Biological Chemistry, The Johns Hopkins University School of Medicine, Baltimore, MD, USA
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Müller M, Mentel M, van Hellemond JJ, Henze K, Woehle C, Gould SB, Yu RY, van der Giezen M, Tielens AGM, Martin WF. Biochemistry and evolution of anaerobic energy metabolism in eukaryotes. Microbiol Mol Biol Rev 2012; 76:444-95. [PMID: 22688819 PMCID: PMC3372258 DOI: 10.1128/mmbr.05024-11] [Citation(s) in RCA: 498] [Impact Index Per Article: 41.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Major insights into the phylogenetic distribution, biochemistry, and evolutionary significance of organelles involved in ATP synthesis (energy metabolism) in eukaryotes that thrive in anaerobic environments for all or part of their life cycles have accrued in recent years. All known eukaryotic groups possess an organelle of mitochondrial origin, mapping the origin of mitochondria to the eukaryotic common ancestor, and genome sequence data are rapidly accumulating for eukaryotes that possess anaerobic mitochondria, hydrogenosomes, or mitosomes. Here we review the available biochemical data on the enzymes and pathways that eukaryotes use in anaerobic energy metabolism and summarize the metabolic end products that they generate in their anaerobic habitats, focusing on the biochemical roles that their mitochondria play in anaerobic ATP synthesis. We present metabolic maps of compartmentalized energy metabolism for 16 well-studied species. There are currently no enzymes of core anaerobic energy metabolism that are specific to any of the six eukaryotic supergroup lineages; genes present in one supergroup are also found in at least one other supergroup. The gene distribution across lineages thus reflects the presence of anaerobic energy metabolism in the eukaryote common ancestor and differential loss during the specialization of some lineages to oxic niches, just as oxphos capabilities have been differentially lost in specialization to anoxic niches and the parasitic life-style. Some facultative anaerobes have retained both aerobic and anaerobic pathways. Diversified eukaryotic lineages have retained the same enzymes of anaerobic ATP synthesis, in line with geochemical data indicating low environmental oxygen levels while eukaryotes arose and diversified.
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Affiliation(s)
| | - Marek Mentel
- Department of Biochemistry, Faculty of Natural Sciences, Comenius University, Bratislava, Slovakia
| | - Jaap J. van Hellemond
- Department of Medical Microbiology and Infectious Diseases, Erasmus University Medical Center, Rotterdam, Netherlands
| | - Katrin Henze
- Institute of Molecular Evolution, University of Düsseldorf, Düsseldorf, Germany
| | - Christian Woehle
- Institute of Molecular Evolution, University of Düsseldorf, Düsseldorf, Germany
| | - Sven B. Gould
- Institute of Molecular Evolution, University of Düsseldorf, Düsseldorf, Germany
| | - Re-Young Yu
- Institute of Molecular Evolution, University of Düsseldorf, Düsseldorf, Germany
| | - Mark van der Giezen
- Biosciences, College of Life and Environmental Sciences, University of Exeter, Exeter, United Kingdom
| | - Aloysius G. M. Tielens
- Department of Medical Microbiology and Infectious Diseases, Erasmus University Medical Center, Rotterdam, Netherlands
| | - William F. Martin
- Institute of Molecular Evolution, University of Düsseldorf, Düsseldorf, Germany
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Enigmatic presence of mitochondrial complex I in Trypanosoma brucei bloodstream forms. EUKARYOTIC CELL 2011; 11:183-93. [PMID: 22158713 DOI: 10.1128/ec.05282-11] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The presence of mitochondrial respiratory complex I in the pathogenic bloodstream stages of Trypanosoma brucei has been vigorously debated: increased expression of mitochondrially encoded functional complex I mRNAs is countered by low levels of enzymatic activity that show marginal inhibition by the specific inhibitor rotenone. We now show that epitope-tagged versions of multiple complex I subunits assemble into α and β subcomplexes in the bloodstream stage and that these subcomplexes require the mitochondrial genome for their assembly. Despite the presence of these large (740- and 855-kDa) multisubunit complexes, the electron transport activity of complex I is not essential under experimental conditions since null mutants of two core genes (NUBM and NUKM) showed no growth defect in vitro or in mouse infection. Furthermore, the null mutants showed no decrease in NADH:ubiquinone oxidoreductase activity, suggesting that the observed activity is not contributed by complex I. This work conclusively shows that despite the synthesis and assembly of subunit proteins, the enzymatic function of the largest respiratory complex is neither significant nor important in the bloodstream stage. This situation appears to be in striking contrast to that for the other respiratory complexes in this parasite, where physical presence in a life-cycle stage always indicates functional significance.
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