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Brinkmann H, Philippe H. The Diversity Of Eukaryotes And The Root Of The Eukaryotic Tree. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2008; 607:20-37. [DOI: 10.1007/978-0-387-74021-8_2] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
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52
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Jékely G. Origin of the nucleus and Ran-dependent transport to safeguard ribosome biogenesis in a chimeric cell. Biol Direct 2008; 3:31. [PMID: 18652645 PMCID: PMC2503971 DOI: 10.1186/1745-6150-3-31] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2008] [Accepted: 07/24/2008] [Indexed: 11/18/2022] Open
Abstract
Background The origin of the nucleus is a central problem about the origin of eukaryotes. The common ancestry of nuclear pore complexes (NPC) and vesicle coating complexes indicates that the nucleus evolved via the modification of a pre-existing endomembrane system. Such an autogenous scenario is cell biologically feasible, but it is not clear what were the selective or neutral mechanisms that had led to the origin of the nuclear compartment. Results A key selective force during the autogenous origin of the nucleus could have been the need to segregate ribosome factories from the cytoplasm where ribosomal proteins (RPs) of the protomitochondrium were synthesized. After its uptake by an anuclear cell the protomitochondrium transferred several of its RP genes to the host genome. Alphaproteobacterial RPs and archaebacterial-type host ribosomes were consequently synthesized in the same cytoplasm. This could have led to the formation of chimeric ribosomes. I propose that the nucleus evolved when the host cell compartmentalised its ribosome factories and the tightly linked genome to reduce ribosome chimerism. This was achieved in successive stages by first evolving karyopherin and RanGTP dependent chaperoning of RPs, followed by the evolution of a membrane network to serve as a diffusion barrier, and finally a hydrogel sieve to ensure selective permeability at nuclear pores. Computer simulations show that a gradual segregation of cytoplasm and nucleoplasm via these steps can progressively reduce ribosome chimerism. Conclusion Ribosome chimerism can provide a direct link between the selective forces for and the mechanisms of evolving nuclear transport and compartmentalisation. The detailed molecular scenario presented here provides a solution to the gradual evolution of nuclear compartmentalization from an anuclear stage. Reviewers This article was reviewed by Eugene V Koonin, Martijn Huynen, Anthony M. Poole and Patrick Forterre.
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Affiliation(s)
- Gáspár Jékely
- Max Planck Institute for Developmental Biology, Spemannstrasse 35. 72076 Tübingen, Germany.
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53
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Gill EE, Diaz-Triviño S, Barberà MJ, Silberman JD, Stechmann A, Gaston D, Tamas I, Roger AJ. Novel mitochondrion-related organelles in the anaerobic amoeba Mastigamoeba balamuthi. Mol Microbiol 2008; 66:1306-20. [PMID: 18045382 DOI: 10.1111/j.1365-2958.2007.05979.x] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Unicellular eukaryotes that lack mitochondria typically contain related organelles such as hydrogenosomes or mitosomes. To characterize the evolutionary diversity of these organelles, we conducted an expressed sequence tag (EST) survey on the free-living amoeba Mastigamoeba balamuthi, a relative of the human parasite Entamoeba histolytica. From 19 182 ESTs, we identified 21 putative mitochondrial proteins implicated in protein import, amino acid interconversion and carbohydrate metabolism, two components of the iron-sulphur cluster (Fe-S) assembly apparatus as well as two enzymes characteristic of hydrogenosomes. By immunofluorescence microscopy and subcellular fractionation, we show that mitochondrial chaperonin 60 is targeted to small abundant organelles within Mastigamoeba. In transmission electron micrographs, we identified double-membraned compartments that likely correspond to these mitochondrion-derived organelles, The predicted organellar proteome of the Mastigamoeba organelle indicates a unique spectrum of functions that collectively have never been observed in mitochondrion-related organelles. However, like Entamoeba, the Fe-S cluster assembly proteins in Mastigamoeba were acquired by lateral gene transfer from epsilon-proteobacteria and do not possess obvious organellar targeting peptides. These data indicate that the loss of classical aerobic mitochondrial functions and acquisition of anaerobic enzymes and Fe-S cluster assembly proteins occurred in a free-living member of the eukaryote super-kingdom Amoebozoa.
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Affiliation(s)
- Erin E Gill
- Canadian Institute for Advanced Research, Program in Integrated Microbial Biodiversity, Department of Biochemistry and Molecular Biology, Dalhousie University, B3H 1X5, Canada
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A mitosome purification protocol based on percoll density gradients and its use in validating the mitosomal nature of Entamoeba histolytica mitochondrial Hsp70. METHODS IN MOLECULAR BIOLOGY (CLIFTON, N.J.) 2008. [PMID: 17951687 DOI: 10.1007/978-1-59745-466-7_11] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register]
Abstract
Mitochondria are indispensable for aerobic respiration, but many microbial eukaryotes have lost this function through reductive evolution. Their modified mitochondria are known as hydrogenosomes or mitosomes depending on whether or not they produce molecular hydrogen. The intestinal parasite Entamoeba histolytica contains mitosomes whose role in cellular metabolism is unclear. Only three proteins have been shown thus far to reside in these organelles: the molecular chaperones Hsp10 and Hsp60 and an unusual ADP/ATP carrier. Here we describe the isolation of E. histolytica mitosomes by cellular fractionation and density gradient centrifugation and show that the mitochondrial-type chaperone Hsp70 is also housed in Entamoeba mitosomes.
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Clark CG, Alsmark UCM, Tazreiter M, Saito-Nakano Y, Ali V, Marion S, Weber C, Mukherjee C, Bruchhaus I, Tannich E, Leippe M, Sicheritz-Ponten T, Foster PG, Samuelson J, Noël CJ, Hirt RP, Embley TM, Gilchrist CA, Mann BJ, Singh U, Ackers JP, Bhattacharya S, Bhattacharya A, Lohia A, Guillén N, Duchêne M, Nozaki T, Hall N. Structure and content of the Entamoeba histolytica genome. ADVANCES IN PARASITOLOGY 2008; 65:51-190. [PMID: 18063096 DOI: 10.1016/s0065-308x(07)65002-7] [Citation(s) in RCA: 133] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
The intestinal parasite Entamoeba histolytica is one of the first protists for which a draft genome sequence has been published. Although the genome is still incomplete, it is unlikely that many genes are missing from the list of those already identified. In this chapter we summarise the features of the genome as they are currently understood and provide previously unpublished analyses of many of the genes.
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Affiliation(s)
- C G Clark
- Department of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London WC1E 7HT, UK
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Evidence of a continuous endoplasmic reticulum in the protozoan parasite Entamoeba histolytica. EUKARYOTIC CELL 2008; 7:1222-6. [PMID: 18281599 DOI: 10.1128/ec.00007-08] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Entamoeba histolytica, the cause of amebiasis, is believed to have no continuous endoplasmic reticulum (ER), with ER functions occurring in vesicles. Here, using an ER-targeted green fluorescent protein fusion protein and fluorescence loss in photobleaching, we have unambiguously demonstrated the presence of a continuous ER compartment in living E. histolytica trophozoites.
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58
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Green JB, Young JPW. Slipins: ancient origin, duplication and diversification of the stomatin protein family. BMC Evol Biol 2008; 8:44. [PMID: 18267007 PMCID: PMC2258279 DOI: 10.1186/1471-2148-8-44] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2007] [Accepted: 02/11/2008] [Indexed: 12/27/2022] Open
Abstract
Background Stomatin is a membrane protein that was first isolated from human red blood cells. Since then, a number of stomatin-like proteins have been identified in all three domains of life. The conservation among these proteins is remarkable, with bacterial and human homologs sharing 50 % identity. Despite being associated with a variety of diseases such as cancer, kidney failure and anaemia, precise functions of these proteins remain unclear. Results We have constructed a comprehensive phylogeny of all 'stomatin-like' sequences that share a 150 amino acid domain. We show these proteins comprise an ancient family that arose early in prokaryotic evolution, and we propose a new nomenclature that reflects their phylogeny, based on the name "slipin" (stomatin-like protein). Within prokaryotes there are two distinct subfamilies that account for the two different origins of the eight eukaryotic stomatin subfamilies, one of which gave rise to eukaryotic SLP-2, renamed here "paraslipin". This was apparently acquired through the mitochondrial endosymbiosis and is widely distributed amongst the major kingdoms. The other prokaryotic subfamily gave rise to the ancestor of the remaining seven eukaryotic subfamilies. The highly diverged "alloslipin" subfamily is represented only by fungal, viral and ciliate sequences. The remaining six subfamilies, collectively termed "slipins", are confined to metazoa. Protostome stomatin, as well as a newly reported arthropod subfamily slipin-4, are restricted to invertebrate groups, whilst slipin-1 (previously SLP-1) is present in nematodes and higher metazoa. In vertebrates, the stomatin family expanded considerably, with at least two duplication events giving rise to podocin and slipin-3 subfamilies (previously SLP-3), with the retained ancestral sequence giving rise to vertebrate stomatin. Conclusion Stomatin-like proteins have their origin in an ancient duplication event that occurred early on in the evolution of prokaryotes. By constructing a phylogeny of this family, we have identified and named a number of orthologous groups: these can now be used to infer function of stomatin subfamilies in a meaningful way.
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Møller AB, Asp T, Holm PB, Palmgren MG. Phylogenetic analysis of P5 P-type ATPases, a eukaryotic lineage of secretory pathway pumps. Mol Phylogenet Evol 2008; 46:619-34. [DOI: 10.1016/j.ympev.2007.10.023] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2007] [Revised: 09/20/2007] [Accepted: 10/26/2007] [Indexed: 01/26/2023]
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Williams BA, Haferkamp I, Keeling PJ. An ADP/ATP-Specific Mitochondrial Carrier Protein in the Microsporidian Antonospora locustae. J Mol Biol 2008; 375:1249-57. [DOI: 10.1016/j.jmb.2007.11.005] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2007] [Revised: 11/01/2007] [Accepted: 11/05/2007] [Indexed: 11/27/2022]
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61
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Hampl V, Silberman JD, Stechmann A, Diaz-Triviño S, Johnson PJ, Roger AJ. Genetic evidence for a mitochondriate ancestry in the 'amitochondriate' flagellate Trimastix pyriformis. PLoS One 2008; 3:e1383. [PMID: 18167542 PMCID: PMC2148110 DOI: 10.1371/journal.pone.0001383] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2007] [Accepted: 12/07/2007] [Indexed: 11/24/2022] Open
Abstract
Most modern eukaryotes diverged from a common ancestor that contained the α-proteobacterial endosymbiont that gave rise to mitochondria. The ‘amitochondriate’ anaerobic protist parasites that have been studied to date, such as Giardia and Trichomonas harbor mitochondrion-related organelles, such as mitosomes or hydrogenosomes. Yet there is one remaining group of mitochondrion-lacking flagellates known as the Preaxostyla that could represent a primitive ‘pre-mitochondrial’ lineage of eukaryotes. To test this hypothesis, we conducted an expressed sequence tag (EST) survey on the preaxostylid flagellate Trimastix pyriformis, a poorly-studied free-living anaerobe. Among the ESTs we detected 19 proteins that, in other eukaryotes, typically function in mitochondria, hydrogenosomes or mitosomes, 12 of which are found exclusively within these organelles. Interestingly, one of the proteins, aconitase, functions in the tricarboxylic acid cycle typical of aerobic mitochondria, whereas others, such as pyruvate:ferredoxin oxidoreductase and [FeFe] hydrogenase, are characteristic of anaerobic hydrogenosomes. Since Trimastix retains genetic evidence of a mitochondriate ancestry, we can now say definitively that all known living eukaryote lineages descend from a common ancestor that had mitochondria.
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Affiliation(s)
- Vladimir Hampl
- Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Jeffrey D. Silberman
- Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, Nova Scotia, Canada
- Department of Biological Sciences, University of Arkansas, Fayetteville, Arkansas, United States of America
| | - Alexandra Stechmann
- Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Sara Diaz-Triviño
- Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Patricia J. Johnson
- Department of Microbiology, Immunology, and Molecular Genetics, University of California at Los Angeles, Los Angeles, California, United States of America
| | - Andrew J. Roger
- Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, Nova Scotia, Canada
- * To whom correspondence should be addressed. E-mail:
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Aguilera P, Barry T, Tovar J. Entamoeba histolytica mitosomes: Organelles in search of a function. Exp Parasitol 2008; 118:10-6. [PMID: 17880942 DOI: 10.1016/j.exppara.2007.08.004] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2007] [Revised: 08/07/2007] [Accepted: 08/08/2007] [Indexed: 11/23/2022]
Abstract
It has been more than eight years since the discovery of mitosomes (mitochondrial remnant organelles) in the intestinal human pathogen Entamoeba histolytica. Despite detailed knowledge about the biochemistry of this parasite and the completion of the E. histolytica genome sequencing project no physiological function has yet been unequivocally assigned to these organelles. Entamoeba mitosomes seem to be the most degenerate of all endosymbiosis-derived organelles studied to date. They do not appear to participate in energy metabolism and may have dispensed completely with the proteins required for iron-sulphur cluster biosynthesis. However, the large number of mitosomes found in E. histolytica trophozoites hints at a significant biological role for these organelles in their natural environment. Identifying the protein complement of mitosomes will provide answers as to their biological significance and the reason(s) for their retention in this parasite.
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Affiliation(s)
- Penelope Aguilera
- School of Biological Sciences, Royal Holloway University of London, Egham TW20 0EX, United Kingdom
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63
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Dacks JB, Walker G, Field MC. Implications of the new eukaryotic systematics for parasitologists. Parasitol Int 2007; 57:97-104. [PMID: 18180199 DOI: 10.1016/j.parint.2007.11.004] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2007] [Revised: 11/15/2007] [Accepted: 11/16/2007] [Indexed: 11/24/2022]
Abstract
An accurate understanding of evolutionary relationships is central in biology. For parasitologists, understanding the relationships among eukaryotic organisms allows the prediction of virulence mechanisms, reconstruction of metabolic pathways, identification of potential drug targets, elucidation of parasite-specific cellular processes and understanding of interactions with the host or vector. Here we consider the impact of major recent revisions of eukaryotic systematics and taxonomy on parasitology. The previous, ladder-like model placed some protists as early diverging, with the remaining eukaryotes "progressing" towards a "crown radiation" of animals, plants, Fungi and some additional protistan lineages. This model has been robustly disproven. The new model is based on vastly increased amounts of molecular sequence data, integration with morphological information and the rigorous application of phylogenetic methods to those data. It now divides eukaryotes into six major supergroups; the relationships between those groups and the order of branching remain unknown. This new eukaryotic phylogeny emphasizes that organisms including Giardia, Trypanosoma and Trichomonas are not primitive, but instead highly evolved and specialised for their specific environments. The wealth of newly available comparative genomic data has also allowed the reconstruction of ancient suites of characteristics and mapping of character evolution in diverse parasites. For example, the last common eukaryotic ancestor was apparently complex, suggesting that lineage-specific adaptations and secondary losses have been important in the evolution of protistan parasites. Referring to the best evidence-based models for eukaryotic evolution will allow parasitologists to make more accurate and reliable inferences about pathogens that cause significant morbidity and mortality.
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Affiliation(s)
- Joel B Dacks
- The Molteno Building, Department of Pathology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QP, UK
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64
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Byers J, Eichinger D. Acetylation of the Entamoeba histone H4 N-terminal domain is influenced by short-chain fatty acids that enter trophozoites in a pH-dependent manner. Int J Parasitol 2007; 38:57-64. [PMID: 17706222 PMCID: PMC2763443 DOI: 10.1016/j.ijpara.2007.06.007] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2007] [Revised: 06/14/2007] [Accepted: 06/29/2007] [Indexed: 10/23/2022]
Abstract
Treatment of higher eukaryotic cells with short-chain fatty acids (SCFA) such as butyrate causes decreased levels of histone deacetylase (HDAC) activity and hyperacetylation of histones, and thereby affects gene expression, cell growth and differentiation. Entamoeba parasites encounter high levels of SCFA in the host colon, and in vitro these compounds allow trophozoite stage parasites to multiply but prevent their differentiation into infectious cysts. The Entamoeba invadens IP-1 histone H4 protein has an unusual number of lysines in its N-terminus, and these become hyperacetylated in trophozoites exposed to the HDAC inhibitors trichostatin A (TSA) or HC-toxin, but not in trophozoites exposed to butyrate. We have now found that several other commonly studied isolates of Entamoeba parasites also have an extended set of histone H4 acetylation sites that become hyperacetylated in response to TSA, but hypoacetylated in response to butyrate, suggesting an unusual sensitivity of this parasite's histone modifying enzymes to SCFA. Butyrate was found to enter trophozoites in a pH-dependent manner consistent with diffusive entry of the un-ionised form of the fatty acid into the amoebae. Transit of the Entamoeba organism through areas of the host intestine with distinct pH and SCFA concentrations would therefore result in very different levels of SCFA within the parasite. Entamoeba appears to have acquired unique alterations of its histone acetylation mechanism that may allow for its growth in the presence of varying amounts of the bacterial fermentation products.
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Affiliation(s)
- Jennifer Byers
- Department of Medical Parasitology, New York University School of Medicine, New York, NY USA
| | - Daniel Eichinger
- Department of Medical Parasitology, New York University School of Medicine, New York, NY USA
- Corresponding author. Department of Medical Parasitology, New York University School of Medicine, 341 East, 25 Street, New York, NY 10010 USA, Tel.: +1-212-263-8171; fax: +1-212-263-8116. E-mail address:
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Jékely G. Origin of phagotrophic eukaryotes as social cheaters in microbial biofilms. Biol Direct 2007; 2:3. [PMID: 17239231 PMCID: PMC1794243 DOI: 10.1186/1745-6150-2-3] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2007] [Accepted: 01/19/2007] [Indexed: 12/28/2022] Open
Abstract
BACKGROUND The origin of eukaryotic cells was one of the most dramatic evolutionary transitions in the history of life. It is generally assumed that eukaryotes evolved later then prokaryotes by the transformation or fusion of prokaryotic lineages. However, as yet there is no consensus regarding the nature of the prokaryotic group(s) ancestral to eukaryotes. Regardless of this, a hardly debatable fundamental novel characteristic of the last eukaryotic common ancestor was the ability to exploit prokaryotic biomass by the ingestion of entire cells, i.e. phagocytosis. The recent advances in our understanding of the social life of prokaryotes may help to explain the origin of this form of total exploitation. PRESENTATION OF THE HYPOTHESIS Here I propose that eukaryotic cells originated in a social environment, a differentiated microbial mat or biofilm that was maintained by the cooperative action of its members. Cooperation was costly (e.g. the production of developmental signals or an extracellular matrix) but yielded benefits that increased the overall fitness of the social group. I propose that eukaryotes originated as selfish cheaters that enjoyed the benefits of social aggregation but did not contribute to it themselves. The cheaters later evolved into predators that lysed other cells and eventually became professional phagotrophs. During several cycles of social aggregation and dispersal the number of cheaters was contained by a chicken game situation, i.e. reproductive success of cheaters was high when they were in low abundance but was reduced when they were over-represented. Radical changes in cell structure, including the loss of the rigid prokaryotic cell wall and the development of endomembranes, allowed the protoeukaryotes to avoid cheater control and to exploit nutrients more efficiently. Cellular changes were buffered by both the social benefits and the protective physico-chemical milieu of the interior of biofilms. Symbiosis with the mitochondial ancestor evolved after phagotrophy as alphaproteobacterial prey developed post-ingestion defence mechanisms to circumvent digestion in the food vacuole. Mitochondrial symbiosis triggered the origin of the nucleus. Cilia evolved last and allowed eukaryotes to predate also on planktonic prey. I will discuss how this scenario may possibly fit into the contrasting phylogenetic frameworks that have been proposed. TESTING THE HYPOTHESIS Some aspects of the hypothesis can be tested experimentally by studying the level of exploitation cheaters can reach in social microbes. It would be interesting to test whether absorption of nutrients from lysed fellow colony members can happen and if cheaters can evolve into predators that actively digest neighbouring cells. IMPLICATIONS OF THE HYPOTHESIS The hypothesis highlights the importance of social exploitation in cell evolution and how a social environment can buffer drastic cellular transformations that would be lethal for planktonic forms.
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Affiliation(s)
- Gáspár Jékely
- European Molecular Biology Laboratory, Meyerhofstrasse 1, 69117 Heidelberg, Germany.
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Ali V, Nozaki T. Current therapeutics, their problems, and sulfur-containing-amino-acid metabolism as a novel target against infections by "amitochondriate" protozoan parasites. Clin Microbiol Rev 2007; 20:164-87. [PMID: 17223627 PMCID: PMC1797636 DOI: 10.1128/cmr.00019-06] [Citation(s) in RCA: 127] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
The "amitochondriate" protozoan parasites of humans Entamoeba histolytica, Giardia intestinalis, and Trichomonas vaginalis share many biochemical features, e.g., energy and amino acid metabolism, a spectrum of drugs for their treatment, and the occurrence of drug resistance. These parasites possess metabolic pathways that are divergent from those of their mammalian hosts and are often considered to be good targets for drug development. Sulfur-containing-amino-acid metabolism represents one such divergent metabolic pathway, namely, the cysteine biosynthetic pathway and methionine gamma-lyase-mediated catabolism of sulfur-containing amino acids, which are present in T. vaginalis and E. histolytica but absent in G. intestinalis. These pathways are potentially exploitable for development of drugs against amoebiasis and trichomoniasis. For instance, L-trifluoromethionine, which is catalyzed by methionine gamma-lyase and produces a toxic product, is effective against T. vaginalis and E. histolytica parasites in vitro and in vivo and may represent a good lead compound. In this review, we summarize the biology of these microaerophilic parasites, their clinical manifestation and epidemiology of disease, chemotherapeutics, the modes of action of representative drugs, and problems related to these drugs, including drug resistance. We further discuss our approach to exploit unique sulfur-containing-amino-acid metabolism, focusing on development of drugs against E. histolytica.
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Affiliation(s)
- Vahab Ali
- Department of Parasitology, Gunma University Graduate School of Medicine, 3-39-22 Showa-machi, Maebashi, Gunma 371-8511, Japan
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68
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Burri L, Keeling PJ. Protein targeting in parasites with cryptic mitochondria. Int J Parasitol 2006; 37:265-72. [PMID: 17250838 DOI: 10.1016/j.ijpara.2006.12.004] [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] [Received: 10/04/2006] [Revised: 12/05/2006] [Accepted: 12/11/2006] [Indexed: 11/22/2022]
Abstract
Many highly specialised parasites have adapted to their environments by simplifying different aspects of their morphology or biochemistry. One interesting case is the mitochondrion, which has been subject to strong reductive evolution in parallel in several different parasitic groups. In extreme cases, mitochondria have degenerated so much in physical size and functional complexity that they were not immediately recognised as mitochondria, and are now referred to as 'cryptic'. Cryptic mitochondrion-derived organelles can be classified as either hydrogenosomes or mitosomes. In nearly all cases they lack a genome and all organellar proteins are nucleus-encoded and expressed in the cytosol. The same is true for the majority of proteins in canonical mitochondria, where the proteins are directed to the organelle by specific targeting sequences (transit peptides) that are recognised by translocases in the mitochondrial membrane. In this review, we compare targeting sequences of different parasitic systems with highly reduced mitochondria and give an overview of how the import machinery has been modified in hydrogenosomes and mitosomes.
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Affiliation(s)
- Lena Burri
- Canadian Institute for Advanced Research, Department of Botany, University of British Columbia, 3529-6270 University Boulevard, Vancouver, BC, Canada V6T 1Z4
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Embley TM. Multiple secondary origins of the anaerobic lifestyle in eukaryotes. Philos Trans R Soc Lond B Biol Sci 2006; 361:1055-67. [PMID: 16754614 PMCID: PMC1578728 DOI: 10.1098/rstb.2006.1844] [Citation(s) in RCA: 102] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Classical ideas for early eukaryotic evolution often posited a period of anaerobic evolution producing a nucleated phagocytic cell to engulf the mitochondrial endosymbiont, whose presence allowed the host to colonize emerging aerobic environments. This idea was given credence by the existence of contemporary anaerobic eukaryotes that were thought to primitively lack mitochondria, thus providing examples of the type of host cell needed. However, the groups key to this hypothesis have now been shown to contain previously overlooked mitochondrial homologues called hydrogenosomes or mitosomes; organelles that share common ancestry with mitochondria but which do not carry out aerobic respiration. Mapping these data on the unfolding eukaryotic tree reveals that secondary adaptation to anaerobic habitats is a reoccurring theme among eukaryotes. The apparent ubiquity of mitochondrial homologues bears testament to the importance of the mitochondrial endosymbiosis, perhaps as a founding event, in eukaryotic evolution. Comparative study of different mitochondrial homologues is needed to determine their fundamental importance for contemporary eukaryotic cells.
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Affiliation(s)
- T Martin Embley
- The Devonshire Building, University of Newcastle upon Tyne, Division of Biology, NE1 7RU, UK.
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Hackstein JHP, Tjaden J, Huynen M. Mitochondria, hydrogenosomes and mitosomes: products of evolutionary tinkering! Curr Genet 2006; 50:225-45. [PMID: 16897087 DOI: 10.1007/s00294-006-0088-8] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2006] [Revised: 06/29/2006] [Accepted: 07/02/2006] [Indexed: 11/29/2022]
Affiliation(s)
- Johannes H P Hackstein
- Department of Evolutionary Microbiology, Faculty of Science, Radboud University Nijmegen, Toernooiveld 1, 6525, ED Nijmegen, The Netherlands.
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Gilchrist CA, Houpt E, Trapaidze N, Fei Z, Crasta O, Asgharpour A, Evans C, Martino-Catt S, Baba DJ, Stroup S, Hamano S, Ehrenkaufer G, Okada M, Singh U, Nozaki T, Mann BJ, Petri WA. Impact of intestinal colonization and invasion on the Entamoeba histolytica transcriptome. Mol Biochem Parasitol 2006; 147:163-76. [PMID: 16569449 DOI: 10.1016/j.molbiopara.2006.02.007] [Citation(s) in RCA: 135] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2005] [Revised: 02/07/2006] [Accepted: 02/08/2006] [Indexed: 11/17/2022]
Abstract
A genome-wide transcriptional analysis of Entamoeba histolytica was performed on trophozoites isolated from the colon of six infected mice and from in vitro culture. An Affymetrix platform gene expression array was designed for this analysis that included probe sets for 9435 open reading frames (ORFs) and 9066 5' and 3' flanking regions. Transcripts were detected for > 80% of all ORFs. A total of 523 transcripts (5.2% of all E. histolytica genes) were significantly changed in amebae isolated from the intestine on Days 1 and 29 after infection: 326 and 109 solely on Days 1 and 29, and 88 on both days. Quantitative real-time reverse transcriptase PCR confirmed these changes in 11/12 genes tested using mRNA isolated from an additional six mice. Adaptation to the intestinal environment was accompanied by increases in a subset of cell signaling genes including transmembrane kinases, ras and rho family GTPases, and calcium binding proteins. Significant decreases in mRNA abundance for genes involved in glycolysis and concomitant increases in lipases were consistent with a change in energy metabolism. Defense against bacteria present in the intestine (but lacking from in vitro culture) was suggested by alterations in mRNA levels of genes similar to the AIG1 plant antibacterial proteins. Decreases in oxygen detoxification pathways were observed as expected in the anaerobic colonic lumen. Of the known virulence factors the most remarkable changes were a 20-35-fold increase in a cysteine proteinase four-like gene, and a 2-3-fold decrease in two members of the Gal/GalNAc lectin light subunit family. Control of the observed changes in mRNA abundance in the intestine might potentially rest with four related proteins with DNA binding domains that were down-regulated 6-16-fold in the intestinal environment. In conclusion, the first genome-wide analysis of the transcriptome of E. histolytica demonstrated that the vast majority of genes are transcribed in trophozoites, and that in the host intestine trophozoites altered the expression of mRNAs for genes implicated in metabolism, oxygen defense, cell signaling, virulence, antibacterial activity, and DNA binding.
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Affiliation(s)
- Carol A Gilchrist
- Department of Internal Medicine, University of Virginia, Charlottesville, VA 22908-1340, USA.
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72
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Abstract
Large-scale comparative genomics in harness with proteomics has substantiated fundamental features of eukaryote cellular evolution. The evolutionary trajectory of modern eukaryotes is distinct from that of prokaryotes. Data from many sources give no direct evidence that eukaryotes evolved by genome fusion between archaea and bacteria. Comparative genomics shows that, under certain ecological settings, sequence loss and cellular simplification are common modes of evolution. Subcellular architecture of eukaryote cells is in part a physical-chemical consequence of molecular crowding; subcellular compartmentation with specialized proteomes is required for the efficient functioning of proteins.
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Affiliation(s)
- C G Kurland
- Department of Microbial Ecology, Lund University, Lund, Sweden
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73
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Okada M, Nozaki T. New insights into molecular mechanisms of phagocytosis in Entamoeba histolytica by proteomic analysis. Arch Med Res 2006; 37:244-52. [PMID: 16380325 DOI: 10.1016/j.arcmed.2005.10.003] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2005] [Accepted: 10/11/2005] [Indexed: 11/19/2022]
Abstract
The protozoan parasite Entamoeba histolytica ingests microorganisms and mammalian cells. Phagocytosis is essential for cell growth and is implicated in pathogenesis of E. histolytica. Phagocytosis consists of a number of steps including recognition of and binding to ligands on the target cells via a galactose/N-acetylgalactosamine-specific lectin, activation of a signaling pathway leading to cytoskeletal reorganization, and vesicle trafficking, all of which play distinct but coordinated roles in phagocytosis. Recent studies of proteomic analysis of purified phagosomes or affinity-purified Gal/GalNAc-binding proteins using reversed phase capillary liquid chromatography and ion trap tandem mass spectrometry enabled high throughput identification of proteins involved in phagosome biogenesis. These studies provided a list of proteins involved in the pathway and also shed light on the dynamic process of phagosome maturation. These approaches should provide significant insights into molecular mechanisms of phagosome biogenesis and help to elucidate the pathogenesis of this important parasite.
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Affiliation(s)
- Mami Okada
- Department of Parasitology, Gunma University Graduate School of Medicine, Showa-machi, Maebashi, Gunma, Japan
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74
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Abstract
The idea that some eukaryotes primitively lacked mitochondria and were true intermediates in the prokaryote-to-eukaryote transition was an exciting prospect. It spawned major advances in understanding anaerobic and parasitic eukaryotes and those with previously overlooked mitochondria. But the evolutionary gap between prokaryotes and eukaryotes is now deeper, and the nature of the host that acquired the mitochondrion more obscure, than ever before.
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Affiliation(s)
- T Martin Embley
- School of Biology, The Devonshire Building, University of Newcastle upon Tyne, Newcastle NE1 7RU, UK.
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75
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Wilson R, Obiozo UM, Quirk PG, Besra GS, Jackson JB. A hybrid of the transhydrogenases from Rhodospirillum rubrum and Mycobacterium tuberculosis catalyses rapid hydride transfer but not the complete, proton-translocating reaction. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2006; 1757:215-23. [PMID: 16624251 DOI: 10.1016/j.bbabio.2006.03.004] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/20/2006] [Revised: 02/24/2006] [Accepted: 03/05/2006] [Indexed: 11/28/2022]
Abstract
All transhydrogenases appear to have three components: dI, which binds NAD(H), and dIII, which binds NADP(H), protrude from the membrane, and dII spans the membrane. However, the polypeptide composition of the enzymes varies amongst species. The transhydrogenases of Mycobacterium tuberculosis and of Rhodospirillum rubrum have three polypeptides. Sequence analysis indicates that an ancestral three-polypeptide enzyme evolved into transhydrogenases with either two polypeptides (such as the Escherichia coli enzyme) or one polypeptide (such as the mitochondrial enzyme). The fusion steps in each case probably led to the development of an additional transmembrane helix. A hybrid transhydrogenase was constructed from the dI component of the M. tuberculosis enzyme and the dII and dIII components of the R. rubrum enzyme. The hybrid catalyses cyclic transhydrogenation but not the proton-translocating, reverse reaction. This shows that nucleotide-binding/release at the NAD(H) site, and hydride transfer, are fully functional but that events associated with NADP(H) binding/release are compromised. It is concluded that sequence mismatch in the hybrid prevents a conformational change between dI and dIII which is essential for the step accompanying proton translocation.
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Affiliation(s)
- Rosalind Wilson
- School of Biosciences, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK
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76
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van der Giezen M, León-Avila G, Tovar J. Characterization of chaperonin 10 (Cpn10) from the intestinal human pathogen Entamoeba histolytica. MICROBIOLOGY-SGM 2005; 151:3107-3115. [PMID: 16151221 DOI: 10.1099/mic.0.28068-0] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Entamoeba histolytica is the causative agent of amoebiasis, a poverty-related disease that kills an estimated 100 000 people each year. E. histolytica does not contain "standard mitochondria", but harbours mitochondrial remnant organelles called mitosomes. These organelles are characterized by the presence of mitochondrial chaperonin Cpn60, but little else is known about the functions and molecular composition of mitosomes. In this study, a gene encoding molecular chaperonin Cpn10--the functional partner of Cpn60--was cloned, and its structure and expression were characterized, as well as the cellular localization of its encoded protein. The 5' untranslated region of the gene contains all of the structural promoter elements required for transcription in this organism. The amoebic Cpn10, like Cpn60, is not significantly upregulated upon heat-shock treatment. Computer-assisted protein modelling, and specific antibodies against Cpn10 and Cpn60, suggest that both proteins interact with each other, and that they function in the same intracellular compartment. Thus, E. histolytica appears to have retained at least two of the key molecular components required for the refolding of imported mitosomal proteins.
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Affiliation(s)
- Mark van der Giezen
- School of Biological Sciences, Royal Holloway, University of London, Egham, Surrey TW20 0EX, UK
| | - Gloria León-Avila
- School of Biological Sciences, Royal Holloway, University of London, Egham, Surrey TW20 0EX, UK
| | - Jorge Tovar
- School of Biological Sciences, Royal Holloway, University of London, Egham, Surrey TW20 0EX, UK
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77
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Okada M, Huston CD, Oue M, Mann BJ, Petri WA, Kita K, Nozaki T. Kinetics and strain variation of phagosome proteins of Entamoeba histolytica by proteomic analysis. Mol Biochem Parasitol 2005; 145:171-83. [PMID: 16290089 DOI: 10.1016/j.molbiopara.2005.10.001] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2005] [Revised: 09/29/2005] [Accepted: 10/03/2005] [Indexed: 12/01/2022]
Abstract
The protozoan parasite Entamoeba histolytica ingests and feeds on microorganisms and mammalian cells. Phagocytosis is essential for cell growth and implicated in pathogenesis of E. histolytica. We report here the dynamic changes of phagosome proteins during phagosome maturation by proteomic analysis using reversed-phase capillary liquid chromatography and ion trap tandem mass spectrometry. Phagosomes were isolated at various intervals after internalization of latex beads. Immunoblot analysis and electron microscopy verified successful isolation of phagosomes. A total of 159 proteins were identified from the reference strain HM1 at different stages of phagosome maturation. Approximately 70% of them were detected in a time-dependent fashion, suggesting dynamism of phagosome biogenesis. The kinetics of representative proteins were verified by immunoblots and also by video microscopy of live transgenic amebae expressing green fluorescent protein-fused EhRab7A. Furthermore, we observed significant differences in phagosome profiles between HM1 and two recent clinical isolates. Approximately 60% of 229 proteins detected in at least one of these three strains were identified only in one strain, while approximately 20% of these proteins were detected in all three strains. These data should provide significant insights into molecular characterization of phagosome biogenesis, and help to elucidate the pathogenesis of this important infection.
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Affiliation(s)
- Mami Okada
- Department of Parasitology, Gunma University Graduate School of Medicine, 3-39-22 Showa-machi, Maebashi, Gunma 371-8511, Japan
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78
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Fischer WM, Palmer JD. Evidence from small-subunit ribosomal RNA sequences for a fungal origin of Microsporidia. Mol Phylogenet Evol 2005; 36:606-22. [PMID: 15923129 DOI: 10.1016/j.ympev.2005.03.031] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2004] [Revised: 03/24/2005] [Accepted: 03/27/2005] [Indexed: 10/25/2022]
Abstract
The phylum Microsporidia comprises a species-rich group of minute, single-celled, and intra-cellular parasites. Lacking normal mitochondria and with unique cytology, microsporidians have sometimes been thought to be a lineage of ancient eukaryotes. Although phylogenetic analyses using small-subunit ribosomal RNA (SSU-rRNA) genes almost invariably place the Microsporidia among the earliest branches on the eukaryotic tree, many other molecules suggest instead a relationship with fungi. Using maximum likelihood methods and a diverse SSU-rRNA data set, we have re-evaluated the phylogenetic affiliations of Microsporidia. We demonstrate that tree topologies used to estimate likelihood model parameters can materially affect phylogenetic searches. We present a procedure for reducing this bias: "tree-based site partitioning," in which a comprehensive set of alternative topologies is used to estimate sequence data partitions based on inferred evolutionary rates. This hypothesis-driven approach appears to be capable of utilizing phylogenetic information that is not available to standard likelihood implementations (e.g., approximation to a gamma distribution); we have employed it in maximum likelihood and Bayesian analysis. Applying our method to a phylogenetically diverse SSU-rRNA data set revealed that the early diverging ("deep") placement of Microsporidia typically found in SSU-rRNA trees is no better than a fungal placement, and that the likeliest placement of Microsporidia among non-long-branch eukaryotic taxa is actually within fungi. These results illustrate the importance of hypothesis testing in parameter estimation, provide a way to address certain problems in difficult data sets, and support a fungal origin for the Microsporidia.
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Affiliation(s)
- William M Fischer
- Biology Department, Indiana University, Jordan Hall 142, Bloomington, IN 47405-3700, USA.
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79
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Okada M, Huston CD, Mann BJ, Petri WA, Kita K, Nozaki T. Proteomic analysis of phagocytosis in the enteric protozoan parasite Entamoeba histolytica. EUKARYOTIC CELL 2005; 4:827-31. [PMID: 15821141 PMCID: PMC1087816 DOI: 10.1128/ec.4.4.827-831.2005] [Citation(s) in RCA: 101] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Proteomic analysis of phagosomes isolated from Entamoeba histolytica by liquid chromatography and mass spectrometry identified 85 proteins involved in surface recognition, actin cytoskeleton rearrangement, vesicular trafficking, and degradation. Phagosome localization of representative proteins was verified by immunofluorescence assay. This study should provide a basis for molecular identification and characterization of phagosome biogenesis.
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Affiliation(s)
- Mami Okada
- Department of Parasitology, Gunma University Graduate School of Medicine, 3-39-22 Showa-machi, Maebashi, Gunma 371-8511, Japan
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80
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Hampl V, Horner DS, Dyal P, Kulda J, Flegr J, Foster PG, Embley TM. Inference of the Phylogenetic Position of Oxymonads Based on Nine Genes: Support for Metamonada and Excavata. Mol Biol Evol 2005; 22:2508-18. [PMID: 16120804 DOI: 10.1093/molbev/msi245] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Circumscribing major eukaryote groups and resolving higher order relationships between them are among the most challenging tasks facing molecular evolutionists. Recently, evidence suggesting a new supergroup (the Excavata) comprising a wide array of flagellates has been collected. This group consists of diplomonads, retortamonads, Carpediemonas, heteroloboseans, Trimastix, jakobids, and Malawimonas, all of which possess a particular type of ventral feeding groove that is proposed to be homologous. Euglenozoans, parabasalids, and oxymonads have also been associated with Excavata as their relationships to one or more core excavate taxa were demonstrated. However, the main barrier to the general acceptance of Excavata is that its existence is founded primarily on cytoskeletal similarities, without consistent support from molecular phylogenetics. In gene trees, Excavata are typically not recovered together. In this paper, we present an analysis of the phylogenetic position of oxymonads (genus Monocercomonoides) based on concatenation of eight protein sequences (alpha-tubulin, beta-tubulin, gamma-tubulin, EF-1alpha, EF-2, cytosolic (cyt) HSP70, HSP90, and ubiquitin) and 18S rRNA. We demonstrate that the genes are in conflict regarding the position of oxymonads. Concatenation of alpha- and beta-tubulin placed oxymonads in the plant-chromist part of the tree, while the concatenation of other genes recovered a well-supported group of Metamonada (oxymonads, diplomonads, and parabasalids) that branched weakly with euglenozoans--connecting all four excavates included in the analyses and thus providing conditional support for the existence of Excavata.
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Affiliation(s)
- Vladimír Hampl
- Department of Parasitology, Faculty of Science, Charles University in Prague, Prague, Czech Republic.
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81
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Chan KW, Slotboom DJ, Cox S, Embley TM, Fabre O, van der Giezen M, Harding M, Horner DS, Kunji ERS, León-Avila G, Tovar J. A novel ADP/ATP transporter in the mitosome of the microaerophilic human parasite Entamoeba histolytica. Curr Biol 2005; 15:737-42. [PMID: 15854906 DOI: 10.1016/j.cub.2005.02.068] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2004] [Revised: 02/21/2005] [Accepted: 02/21/2005] [Indexed: 11/23/2022]
Abstract
Recent data suggest that microaerophilic and parasitic protozoa, which lack oxidative phosphorylation, nevertheless contain mitochondrial homologs [1-6], organelles that share common ancestry with mitochondria. Such widespread retention suggests there may be a common function for mitochondrial homologs that makes them essential for eukaryotic cells. We determined the mitochondrial carrier family (MCF) complement of the Entamoeba histolytica mitochondrial homolog, also known as a crypton [5] or more commonly as a mitosome [3]. MCF proteins support mitochondrial metabolic energy generation, DNA replication, and amino-acid metabolism by linking biochemical pathways in the mitochondrial matrix with those in the cytosol [7]. MCF diversity thus closely mirrors important facets of mitochondrial metabolic diversity. The Entamoeba histolytica mitosome has lost all but a single type of MCF protein, which transports ATP and ADP via a novel mechanism that is not reliant on a membrane potential. Phylogenetic analyses confirm that the Entamoeba ADP/ATP carrier is distinct from archetypal mitochondrial ADP/ATP carriers, an observation that is supported by its different substrate and inhibitor specificity. Because many functions of yeast and human mitochondria rely on solutes transported by specialized members of this family, the Entamoeba mitosome must contain only a small subset of these processes requiring adenine nucleotide exchange.
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Affiliation(s)
- Ka Wai Chan
- Dunn Human Nutrition Unit, Medical Research Council, Cambridge, UK
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82
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Keithly JS, Langreth SG, Buttle KF, Mannella CA. Electron tomographic and ultrastructural analysis of the Cryptosporidium parvum relict mitochondrion, its associated membranes, and organelles. J Eukaryot Microbiol 2005; 52:132-40. [PMID: 15817118 DOI: 10.1111/j.1550-7408.2005.04-3317.x] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Sporozoites of the apicomplexan Cryptosporidium parvum possess a small, membranous organelle sandwiched between the nucleus and crystalloid body. Based upon immunolabelling data, this organelle was identified as a relict mitochondrion. Transmission electron microscopy and tomographic reconstruction reveal the complex arrangement of membranes in the vicinity of this organelle, as well as its internal organization. The mitochondrion is enveloped by multiple segments of rough endoplasmic reticulum that extend from the outer nuclear envelope. In tomographic reconstructions of the mitochondrion, there is either a single, highly-folded inner membrane or multiple internal subcompartments (which might merge outside the reconstructed volume). The infoldings of the inner membrane lack the tubular "crista junctions" found in typical metazoan, fungal, and protist mitochondria. The absence of this highly conserved structural feature is congruent with the loss, through reductive evolution, of the normal oxidative phosphorylation machinery in C. parvum. It is proposed that the retention of a relict mitochondrion in C. parvum is a strategy for compartmentalizing away from the cytosol toxic ferrous iron and sulfide, which are needed for iron sulfur cluster biosynthesis, an essential function of mitochondria in all eukaryotes.
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Affiliation(s)
- Janet S Keithly
- Division of Infectious Diseases, Wadsworth Center, New York State Department of Health, Albany, New York 12201, USA.
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83
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Libros-Ziv P, Villalobo E, Mirelman D. Entamoeba histolytica: Identification and characterization of an N-ethylmaleimide sensitive fusion protein homologue. Exp Parasitol 2005; 110:276-9. [PMID: 15955324 DOI: 10.1016/j.exppara.2005.02.018] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2005] [Revised: 02/20/2005] [Accepted: 02/23/2005] [Indexed: 11/22/2022]
Abstract
Entamoeba histolytica is a phagocytic cell with numerous vesicles of different sizes and shapes but without a well-defined Golgi apparatus. Despite this, genes implied in membrane trafficking have been identified in the genome of this parasite. One of these genes is homologous to the N-ethylmaleimide sensitive fusion factor (NSF), whose protein has been shown to play an important role in vesicle fusion in other eukaryotic cells. In this report, we investigated the NSF homologue gene from a pathogenic E. histolytica, characterized its protein product and two of its activities, ATPase and in vitro intra-Golgi transport. The finding of an active NSF protein in E. histolytica indicates that a simple or primordial Golgi apparatus probably exists in this microorganism, as has been proposed by others.
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Affiliation(s)
- Pazit Libros-Ziv
- Department of Biological Chemistry, Weizmann Institute of Science, Rehovot, Israel
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84
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Regoes A, Zourmpanou D, León-Avila G, van der Giezen M, Tovar J, Hehl AB. Protein import, replication, and inheritance of a vestigial mitochondrion. J Biol Chem 2005; 280:30557-63. [PMID: 15985435 DOI: 10.1074/jbc.m500787200] [Citation(s) in RCA: 94] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Mitochondrial remnant organelles (mitosomes) that exist in a range of "amitochondrial" eukaryotic organisms represent ideal models for the study of mitochondrial evolution and for the establishment of the minimal set of proteins required for the biogenesis of an endosymbiosis-derived organelle. Giardia intestinalis, often described as the earliest branching eukaryote, contains double membrane-bounded structures involved in iron-sulfur cluster biosynthesis, an essential function of mitochondria. Here we present evidence that Giardia mitosomes also harbor Cpn60, mtHsp70, and ferredoxin and that despite their advanced state of reductive evolution they have retained vestiges of presequence-dependent and -independent protein import pathways akin to those that operate in mammalian mitochondria. Although import of IscU and ferredoxin is still reliant on their amino-terminal presequences, targeting of Giardia Cpn60, IscS, or mtHsp70 into mitosomes no longer requires cleavable presequences, a derived feature from their mitochondrial homologues. In addition, we found that division and segregation of a single centrally positioned mitosome tightly associated with the microtubular cytoskeleton is coordinated with the cell cycle, whereas peripherally located mitosomes are inherited into daughter cells stochastically.
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Affiliation(s)
- Attila Regoes
- Institute of Parasitology, University of Zürich, Winterthurerstrasse 266a, CH-8057 Zürich, Switzerland
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85
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Thomarat F, Vivarès CP, Gouy M. Phylogenetic analysis of the complete genome sequence of Encephalitozoon cuniculi supports the fungal origin of microsporidia and reveals a high frequency of fast-evolving genes. J Mol Evol 2005; 59:780-91. [PMID: 15599510 DOI: 10.1007/s00239-004-2673-0] [Citation(s) in RCA: 86] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2003] [Accepted: 06/29/2004] [Indexed: 10/26/2022]
Abstract
Microsporidia are unicellular eukaryotes living as obligate intracellular parasites. Lacking mitochondria, they were initially considered as having diverged before the endosymbiosis at the origin of mitochondria. That microsporidia were primitively amitochondriate was first questioned by the discovery of microsporidial sequences homologous to genes encoding mitochondrial proteins and then refuted by the identification of remnants of mitochondria in their cytoplasm. Various molecular phylogenies also cast doubt on the early divergence of microsporidia, these organisms forming a monophyletic group with or within the fungi. The 2001 proteins putatively encoded by the complete genome of Encephalitozoon cuniculi provided powerful data to test this hypothesis. Phylogenetic analysis of 99 proteins selected as adequate phylogenetic markers indicated that the E. cuniculi sequences having the lowest evolutionary rates preferentially clustered with fungal sequences or, more rarely, with both animal and fungal sequences. Because sequences with low evolutionary rates are less sensitive to the long-branch attraction artifact, we concluded that microsporidia are evolutionarily related to fungi. This analysis also allowed comparing the accuracy of several phylogenetic algorithms for a fast-evolving lineage with real rather than simulated sequences.
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Affiliation(s)
- Fabienne Thomarat
- Laboratoire de Biométrie et Biologie Evolutive, UMR CNRS 5558, Université Claude Bernard Lyon I, 43 boulevard du 11 Novembre 1918, 69622 Villeurbanne, France
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86
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van der Giezen M, Tovar J, Clark CG. Mitochondrion‐Derived Organelles in Protists and Fungi. INTERNATIONAL REVIEW OF CYTOLOGY 2005; 244:175-225. [PMID: 16157181 DOI: 10.1016/s0074-7696(05)44005-x] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/12/2023]
Abstract
The mitochondrion is generally considered to be a defining feature of eukaryotic cells, yet most anaerobic eukaryotes lack this organelle. Many of these were previously thought to derive from eukaryotes that diverged prior to acquisition of the organelle through endosymbiosis. It is now known that all extant eukaryotes are descended from an ancestor that had a mitochondrion and that in anaerobic eukaryotes the organelle has been modified into either hydrogenosomes, which continue to generate energy for the host cell, or mitosomes, which do not. These organelles have each arisen independently several times. Recent evidence suggests a shared derived characteristic that may be responsible for the retention of the organelles in the absence of the better-known mitochondrial functions--iron-sulfur cluster assembly. This review explores the events leading to this new understanding of mitochondrion-derived organelles in amitochondriate eukaryotes, the current state of our knowledge, and future areas for investigation.
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Affiliation(s)
- Mark van der Giezen
- School of Biological Sciences, Royal Holloway, University of London, Egham, Surrey TW20 0EX, United Kingdom
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87
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Nozaki T, Ali V, Tokoro M. Sulfur-Containing Amino Acid Metabolism in Parasitic Protozoa. ADVANCES IN PARASITOLOGY 2005; 60:1-99. [PMID: 16230102 DOI: 10.1016/s0065-308x(05)60001-2] [Citation(s) in RCA: 80] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Sulfur-containing amino acids play indispensable roles in a wide variety of biological activities including protein synthesis, methylation, and biosynthesis of polyamines and glutathione. Biosynthesis and catabolism of these amino acids need to be carefully regulated to achieve the requirement of the above-mentioned activities and also to eliminate toxicity attributable to the amino acids. Genome-wide analyses of enzymes involved in the metabolic pathways of sulfur-containing amino acids, including transsulfuration, sulfur assimilatory de novo cysteine biosynthesis, methionine cycle, and degradation, using genome databases available from a variety of parasitic protozoa, reveal remarkable diversity between protozoan parasites and their mammalian hosts. Thus, the sulfur-containing amino acid metabolic pathways are a rational target for the development of novel chemotherapeutic and prophylactic agents against diseases caused by protozoan parasites. These pathways also demonstrate notable heterogeneity among parasites, suggesting that the metabolism of sulfur-containing amino acids reflects the diversity of parasitism among parasite species, and probably influences their biology and pathophysiology such as virulence competence and stress defense.
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Affiliation(s)
- Tomoyoshi Nozaki
- Department of Parasitology, Gunma University Graduate School of Medicine, 3-39-22 Showa-machi, Maebashi, Gunma, 371-8511, Japan
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88
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Hackstein JHP, Yarlett N. Hydrogenosomes and symbiosis. PROGRESS IN MOLECULAR AND SUBCELLULAR BIOLOGY 2005; 41:117-42. [PMID: 16623392 DOI: 10.1007/3-540-28221-1_7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Affiliation(s)
- Johannes H P Hackstein
- Department of Evolutionary Microbiology, Faculty of Science, Radboud University Nijmegen, Toernooiveld 1, NL 6525 ED Nijmegen, The Netherlands.
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89
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Abstract
Over the past several decades, our knowledge of the origin and evolution of mitochondria has been greatly advanced by determination of complete mitochondrial genome sequences. Among the most informative mitochondrial genomes have been those of protists (primarily unicellular eukaryotes), some of which harbor the most gene-rich and most eubacteria-like mitochondrial DNAs (mtDNAs) known. Comparison of mtDNA sequence data has provided insights into the radically diverse trends in mitochondrial genome evolution exhibited by different phylogenetically coherent groupings of eukaryotes, and has allowed us to pinpoint specific protist relatives of the multicellular eukaryotic lineages (animals, plants, and fungi). This comparative genomics approach has also revealed unique and fascinating aspects of mitochondrial gene expression, highlighting the mitochondrion as an evolutionary playground par excellence.
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Affiliation(s)
- Michael W Gray
- Robert Cedergren Center, Program in Evolutionary Biology, Canadian Institute for Advanced Research, Canada.
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90
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Dong J, Wen J, Xin D, Lu S. Evolutionary status ofEntamoeba. CHINESE SCIENCE BULLETIN-CHINESE 2004. [DOI: 10.1007/bf03183412] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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91
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Lyons EJ, Carlton JM. Mind the gap: bridging the divide between clinical and molecular studies of the trichomonads. Trends Parasitol 2004; 20:204-7. [PMID: 15105016 DOI: 10.1016/j.pt.2004.03.005] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Emily J Lyons
- The Institute for Genomic Research, 9712 Medical Center Drive, Rockville, MD 20850, USA
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92
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Saelens X, Festjens N, Vande Walle L, van Gurp M, van Loo G, Vandenabeele P. Toxic proteins released from mitochondria in cell death. Oncogene 2004; 23:2861-74. [PMID: 15077149 DOI: 10.1038/sj.onc.1207523] [Citation(s) in RCA: 633] [Impact Index Per Article: 31.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
A plethora of apoptotic stimuli converge on the mitochondria and affect their membrane integrity. As a consequence, multiple death-promoting factors residing in the mitochondrial intermembrane space are liberated in the cytosol. Pro- and antiapoptotic Bcl-2 family proteins control the release of these mitochondrial proteins by inducing or preventing permeabilization of the outer mitochondrial membrane. Once released into the cytosol, these mitochondrial proteins activate both caspase-dependent and -independent cell death pathways. Cytochrome c was the first protein shown to be released from the mitochondria into the cytosol, where it induces apoptosome formation. Other released mitochondrial proteins include apoptosis-inducing factor (AIF) and endonuclease G, both of which contribute to apoptotic nuclear DNA damage in a caspase-independent way. Other examples are Smac/DIABLO (second mitochondria-derived activator of caspase/direct IAP-binding protein with low PI) and the serine protease HtrA2/OMI (high-temperature requirement protein A2), which both promote caspase activation and instigate caspase-independent cytotoxicity. The precise mode of action and importance of cytochrome c in apoptosis in mammalian cells has become clear through biochemical, structural and genetic studies. More recently identified factors, for example HtrA2/OMI and Smac/DIABLO, are still being studied intensively in order to delineate their functions in apoptosis. A better understanding of these functions may help to develop new strategies to treat cancer.
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Affiliation(s)
- Xavier Saelens
- Department for Molecular Biomedical Research, VIB and Ghent University, Fiers-Shell-Van Montagu Building, Ghent B9052, Belgium
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93
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León-Avila G, Tovar J. Mitosomes of Entamoeba histolytica are abundant mitochondrion-related remnant organelles that lack a detectable organellar genome. Microbiology (Reading) 2004; 150:1245-1250. [PMID: 15133087 DOI: 10.1099/mic.0.26923-0] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The existence of mitochondrion-related relict organelles (mitosomes) in the amitochondrial human pathogen Entamoeba histolytica and the detection of extranuclear DNA-containing cytoplasmic structures (EhKOs) has led to the suggestion that a remnant genome from the original mitochondrial endosymbiont might have been retained in this organism. This study reports on the mutually exclusive distribution of Cpn60 and extranuclear DNA in E. histolytica and on the distribution of Cpn60-containing mitosomes in this parasite. In situ nick-translation coupled to immunofluorescence microscopy failed to detect the presence of DNA in mitosomes, either in fixed parasite trophozoites or in partially purified organellar fractions. These results indicate that a remnant organellar genome has not been retained in E. histolytica mitosomes and demonstrate unequivocally that EhKOs and mitosomes are distinct and unrelated cellular structures.
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Affiliation(s)
- Gloria León-Avila
- School of Biological Sciences, Royal Holloway, University of London, Egham TW20 0EX, UK
| | - Jorge Tovar
- School of Biological Sciences, Royal Holloway, University of London, Egham TW20 0EX, UK
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94
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van der Giezen M, Cox S, Tovar J. The iron-sulfur cluster assembly genes iscS and iscU of Entamoeba histolytica were acquired by horizontal gene transfer. BMC Evol Biol 2004; 4:7. [PMID: 15040816 PMCID: PMC373444 DOI: 10.1186/1471-2148-4-7] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2003] [Accepted: 02/20/2004] [Indexed: 11/10/2022] Open
Abstract
Background Iron-sulfur (FeS) proteins are present in all living organisms and play important roles in electron transport and metalloenzyme catalysis. The maturation of FeS proteins in eukaryotes is an essential function of mitochondria, but little is known about this process in amitochondriate eukaryotes. Here we report on the identification and analysis of two genes encoding critical FeS cluster (Isc) biosynthetic proteins from the amitochondriate human pathogen Entamoeba histolytica. Results E. histolytica IscU and IscS were found to contain all features considered essential for their biological activity, including amino acid residues involved in substrate and/or co-factor binding. The IscU protein differs significantly from other eukaryotic homologs and resembles the long type isoforms encountered in some bacteria. Phylogenetic analyses of E. histolytica IscS and IscU showed a close relationship with homologs from Helicobacter pylori and Campylobacter jejuni, to the exclusion of mitochondrial isoforms. Conclusions The bacterial-type FeS cluster assembly genes of E. histolytica suggest their lateral acquisition from epsilon proteobacteria. This is a clear example of horizontal gene transfer (HGT) from eubacteria to unicellular eukaryotic organisms, a phenomenon known to contribute significantly to the evolution of eukaryotic genomes.
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Affiliation(s)
- Mark van der Giezen
- School of Biological Sciences, Royal Holloway, University of London, Egham, Surrey TW20 0EX, UK
| | - Siân Cox
- School of Biological Sciences, Royal Holloway, University of London, Egham, Surrey TW20 0EX, UK
| | - Jorge Tovar
- School of Biological Sciences, Royal Holloway, University of London, Egham, Surrey TW20 0EX, UK
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95
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Abstract
Glutathione (GSH; gamma-L-glutamyl-L-cysteinyl-glycine), a non-protein thiol with a very low redox potential (E'0 = 240 mV for thiol-disulfide exchange), is present in high concentration up to 10 mM in yeasts and filamentous fungi. GSH is concerned with basic cellular functions as well as the maintenance of mitochondrial structure, membrane integrity, and in cell differentiation and development. GSH plays key roles in the response to several stress situations in fungi. For example, GSH is an important antioxidant molecule, which reacts non-enzymatically with a series of reactive oxygen species. In addition, the response to oxidative stress also involves GSH biosynthesis enzymes, NADPH-dependent GSH-regenerating reductase, glutathione S-transferase along with peroxide-eliminating glutathione peroxidase and glutaredoxins. Some components of the GSH-dependent antioxidative defence system confer resistance against heat shock and osmotic stress. Formation of protein-SSG mixed disulfides results in protection against desiccation-induced oxidative injuries in lichens. Intracellular GSH and GSH-derived phytochelatins hinder the progression of heavy metal-initiated cell injuries by chelating and sequestering the metal ions themselves and/or by eliminating reactive oxygen species. In fungi, GSH is mobilized to ensure cellular maintenance under sulfur or nitrogen starvation. Moreover, adaptation to carbon deprivation stress results in an increased tolerance to oxidative stress, which involves the induction of GSH-dependent elements of the antioxidant defence system. GSH-dependent detoxification processes concern the elimination of toxic endogenous metabolites, such as excess formaldehyde produced during the growth of the methylotrophic yeasts, by formaldehyde dehydrogenase and methylglyoxal, a by-product of glycolysis, by the glyoxalase pathway. Detoxification of xenobiotics, such as halogenated aromatic and alkylating agents, relies on glutathione S-transferases. In yeast, these enzymes may participate in the elimination of toxic intermediates that accumulate in stationary phase and/or act in a similar fashion as heat shock proteins. GSH S-conjugates may also form in a glutathione S-transferases-independent way, e.g. through chemical reaction between GSH and the antifugal agent Thiram. GSH-dependent detoxification of penicillin side-chain precursors was shown in Penicillium sp. GSH controls aging and autolysis in several fungal species, and possesses an anti-apoptotic feature.
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Affiliation(s)
- István Pócsi
- Department of Microbiology and Biotechnology, Faculty of Sciences, University of Debrecen, P.O. Box 63, H-4010 Debrecen, Hungary
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96
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Riordan CE, Ault JG, Langreth SG, Keithly JS. Cryptosporidium parvum Cpn60 targets a relict organelle. Curr Genet 2003; 44:138-47. [PMID: 12928750 DOI: 10.1007/s00294-003-0432-1] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2003] [Revised: 06/30/2003] [Accepted: 07/13/2003] [Indexed: 11/27/2022]
Abstract
Chaperonin 60 (Cpn60) is a well-established marker protein for eukaryotic mitochondria and plastids. In order to determine whether the small double-membrane-bounded organelle posterior to the nucleus in the apicomplexan Cryptosporidium parvum is a mitochondrion, the Cpn60 gene of C. parvum sporozoites ( CpCpn60) was analyzed and antibodies were generated for localization of the peptide. Sequence and phylogenetic analyses indicated that CpCpn60 is a mitochondrial isotype and that antibodies against it localize to the rough endoplasmic reticulum-enveloped remnant organelle of C. parvum sporozoites. These data show this organelle is of mitochondrial origin.
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Affiliation(s)
- Christina E Riordan
- Wadsworth Center, New York State Department of Health, Axelrod Institute for Public Health, 120 New Scotland Avenue, Albany, NY 12208, USA
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97
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Tokoro M, Asai T, Kobayashi S, Takeuchi T, Nozaki T. Identification and characterization of two isoenzymes of methionine gamma-lyase from Entamoeba histolytica: a key enzyme of sulfur-amino acid degradation in an anaerobic parasitic protist that lacks forward and reverse trans-sulfuration pathways. J Biol Chem 2003; 278:42717-27. [PMID: 12920135 DOI: 10.1074/jbc.m212414200] [Citation(s) in RCA: 89] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
To better understand the metabolism of sulfur-containing amino acids, which likely plays a key role in a variety of cell functions, in Entamoeba histolytica, we searched the genome data base for genes encoding putative orthologs of enzymes known to be involved in the metabolism. The search revealed that E. histolytica possesses only incomplete cysteine-methionine conversion pathways in both directions. Instead, this parasite possesses genes encoding two isoenzymes of methionine gamma-lyase (EC 4.4.1.11, EhMGL1/2), which has been implicated in the degradation of sulfur-containing amino acids. The two amebic MGL isoenzymes, showing 69% identity to each other, encode 389- and 392-amino acid polypeptides with predicted molecular masses of 42.3 and 42.7 kDa and pIs of 6.01 and 6.63, respectively. Amino acid comparison and phylogenetic analysis suggested that these amebic MGLs are likely to have been horizontally transferred from the Archaea, whereas an MGL from another anaerobic protist Trichomonas vaginalis has MGL isotypes that share a common ancestor with bacteria. Enzymological and immunoblot analyses of the partially purified native amebic MGL confirmed that both of the MGL isotypes are expressed in a comparable amount predominantly in the cytosol and form a homotetramer. Recombinant EhMGL1 and 2 proteins catalyzed degradation of L-methionine, DL-homocysteine, L-cysteine, and O-acetyl-L-serine to form alpha-keto acid, ammonia, and hydrogen sulfide or methanethiol, whereas activity toward cystathionine was negligible. These two isoenzymes showed notable differences in substrate specificity and pH optimum. In addition, we showed that EhMGL is an ideal target for the development of new chemotherapeutic agents against amebiasis by demonstrating an amebicidal effect of the methionine analog trifluoromethionine on trophozoites in culture (IC50 18 mum) and that this effect of trifluoromethionine was completely abolished by the addition of the MGL-specific inhibitor DL-propargylglycine.
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Affiliation(s)
- Masaharu Tokoro
- Department of Tropical Medicine and Parasitology, Keio University School of Medicine, Tokyo 160-8582, Japan
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98
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Bakatselou C, Beste D, Kadri AO, Somanath S, Clark CG. Analysis of genes of mitochondrial origin in the genus Entamoeba. J Eukaryot Microbiol 2003; 50:210-4. [PMID: 12836878 DOI: 10.1111/j.1550-7408.2003.tb00119.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
The amitochondriate protistan parasite Entamoeba histolytica has lost most mitochondrial functions secondarily but has retained a reduced organelle of mitochondrial origin, the mitosome. We here investigate the presence, origins, and expression in other species of Entamoeba of three genes of mitochondrial origin--pyridine nucleotide transhydrogenase and the mitochondrial-type chaperonins cpn60 and hsp70. The genes appear to be present in all species and specifically related, confirming that the E. histolytica mitosomal genes were not acquired recently by lateral transfer from another organism. Detection of expression was not possible in all cases under the culture conditions used, but several genes were induced during recovery from exposure to a heat shock. This includes the transhydrogenase, which to our knowledge has not been shown previously to be a heat-shock protein.
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Affiliation(s)
- Christina Bakatselou
- Department of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, Keppel Street, London, WC1E 7HT, UK
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99
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Emelyanov VV. Mitochondrial connection to the origin of the eukaryotic cell. EUROPEAN JOURNAL OF BIOCHEMISTRY 2003; 270:1599-618. [PMID: 12694174 DOI: 10.1046/j.1432-1033.2003.03499.x] [Citation(s) in RCA: 86] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Phylogenetic evidence is presented that primitively amitochondriate eukaryotes containing the nucleus, cytoskeleton, and endomembrane system may have never existed. Instead, the primary host for the mitochondrial progenitor may have been a chimeric prokaryote, created by fusion between an archaebacterium and a eubacterium, in which eubacterial energy metabolism (glycolysis and fermentation) was retained. A Rickettsia-like intracellular symbiont, suggested to be the last common ancestor of the family Rickettsiaceae and mitochondria, may have penetrated such a host (pro-eukaryote), surrounded by a single membrane, due to tightly membrane-associated phospholipase activity, as do present-day rickettsiae. The relatively rapid evolutionary conversion of the invader into an organelle may have occurred in a safe milieu via numerous, often dramatic, changes involving both partners, which resulted in successful coupling of the host glycolysis and the symbiont respiration. Establishment of a potent energy-generating organelle made it possible, through rapid dramatic changes, to develop genuine eukaryotic elements. Such sequential, or converging, global events could fill the gap between prokaryotes and eukaryotes known as major evolutionary discontinuity.
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100
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Abstract
Amoebiasis is the second leading cause of death from parasitic disease worldwide. The causative protozoan parasite, Entamoeba histolytica, is a potent pathogen. Secreting proteinases that dissolve host tissues, killing host cells on contact, and engulfing red blood cells, E histolytica trophozoites invade the intestinal mucosa, causing amoebic colitis. In some cases amoebas breach the mucosal barrier and travel through the portal circulation to the liver, where they cause abscesses consisting of a few E histolytica trophozoites surrounding dead and dying hepatocytes and liquefied cellular debris. Amoebic liver abscesses grow inexorably and, at one time, were almost always fatal, but now even large abscesses can be cured by one dose of antibiotic. Evidence that what we thought was a single species based on morphology is, in fact, two genetically distinct species--now termed Entamoeba histolytica (the pathogen) and Entamoeba dispar (a commensal)--has turned conventional wisdom about the epidemiology and diagnosis of amoebiasis upside down. New models of disease have linked E histolytica induction of intestinal inflammation and hepatocyte programmed cell death to the pathogenesis of amoebic colitis and amoebic liver abscess.
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Affiliation(s)
- Samuel L Stanley
- Department of Medicine, Washington University School of Medicine, 660 South Euclid Avenue, St Louis, MO, St Louis, MO 63110, USA.
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