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Chen PHB, Li XL, Baskin JM. Synthetic Lipid Biology. Chem Rev 2025; 125:2502-2560. [PMID: 39805091 PMCID: PMC11969270 DOI: 10.1021/acs.chemrev.4c00761] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2025]
Abstract
Cells contain thousands of different lipids. Their rapid and redundant metabolism, dynamic movement, and many interactions with other biomolecules have justly earned lipids a reputation as a vexing class of molecules to understand. Further, as the cell's hydrophobic metabolites, lipids assemble into supramolecular structures─most commonly bilayers, or membranes─from which they carry out myriad biological functions. Motivated by this daunting complexity, researchers across disciplines are bringing order to the seeming chaos of biological lipids and membranes. Here, we formalize these efforts as "synthetic lipid biology". Inspired by the idea, central to synthetic biology, that our abilities to understand and build biological systems are intimately connected, we organize studies and approaches across numerous fields to create, manipulate, and analyze lipids and biomembranes. These include construction of lipids and membranes from scratch using chemical and chemoenzymatic synthesis, editing of pre-existing membranes using optogenetics and protein engineering, detection of lipid metabolism and transport using bioorthogonal chemistry, and probing of lipid-protein interactions and membrane biophysical properties. What emerges is a portrait of an incipient field where chemists, biologists, physicists, and engineers work together in proximity─like lipids themselves─to build a clearer description of the properties, behaviors, and functions of lipids and membranes.
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Affiliation(s)
- Po-Hsun Brian Chen
- Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, New York 14853, United States
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853, United States
| | - Xiang-Ling Li
- Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, New York 14853, United States
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853, United States
| | - Jeremy M Baskin
- Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, New York 14853, United States
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853, United States
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2
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Link F, Borges AR, Jones NG, Engstler M. To the Surface and Back: Exo- and Endocytic Pathways in Trypanosoma brucei. Front Cell Dev Biol 2021; 9:720521. [PMID: 34422837 PMCID: PMC8377397 DOI: 10.3389/fcell.2021.720521] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2021] [Accepted: 07/06/2021] [Indexed: 01/10/2023] Open
Abstract
Trypanosoma brucei is one of only a few unicellular pathogens that thrives extracellularly in the vertebrate host. Consequently, the cell surface plays a critical role in both immune recognition and immune evasion. The variant surface glycoprotein (VSG) coats the entire surface of the parasite and acts as a flexible shield to protect invariant proteins against immune recognition. Antigenic variation of the VSG coat is the major virulence mechanism of trypanosomes. In addition, incessant motility of the parasite contributes to its immune evasion, as the resulting fluid flow on the cell surface drags immunocomplexes toward the flagellar pocket, where they are internalized. The flagellar pocket is the sole site of endo- and exocytosis in this organism. After internalization, VSG is rapidly recycled back to the surface, whereas host antibodies are thought to be transported to the lysosome for degradation. For this essential step to work, effective machineries for both sorting and recycling of VSGs must have evolved in trypanosomes. Our understanding of the mechanisms behind VSG recycling and VSG secretion, is by far not complete. This review provides an overview of the trypanosome secretory and endosomal pathways. Longstanding questions are pinpointed that, with the advent of novel technologies, might be answered in the near future.
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Affiliation(s)
- Fabian Link
- Department of Cell and Developmental Biology, Biocenter, University of Würzburg, Würzburg, Germany
| | - Alyssa R Borges
- Department of Cell and Developmental Biology, Biocenter, University of Würzburg, Würzburg, Germany
| | - Nicola G Jones
- Department of Cell and Developmental Biology, Biocenter, University of Würzburg, Würzburg, Germany
| | - Markus Engstler
- Department of Cell and Developmental Biology, Biocenter, University of Würzburg, Würzburg, Germany
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3
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The ancient small GTPase Rab21 functions in intermediate endocytic steps in trypanosomes. EUKARYOTIC CELL 2013; 13:304-19. [PMID: 24376004 DOI: 10.1128/ec.00269-13] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Endocytosis is an essential process in nearly all eukaryotic cells, including the African trypanosome Trypanosoma brucei. Endocytosis in these organisms is exclusively clathrin mediated, although several lineage-specific features indicate that precise mechanisms are distinct from those of higher eukaryotes. T. brucei Rab21 is a member of an ancient, pan-eukaryotic, endocytic Rab clade that is retained by trypanosomes. We show that T. brucei Rab21 (TbRab21) localizes to endosomes, partially colocalizing with TbRab5A, TbRab28, and TbVps23, the latter two being present at late endosomes. TbRab21 expression is essential for cellular proliferation, and its suppression results in a partial block in traffic to the lysosome. RNA interference (RNAi)-mediated knockdown of TbRab21 had no effect on TbRab5A expression or location but did result in decreased in trans expression of ESCRT (trypanosome endosomal sorting complex required for transport) components and TbRab28, while knockdown of ESCRT subunit TbVps23 resulted in decreased TbRab21 expression. These data suggest that TbRab21 acts downstream of TbRab5A and functions in intimate connection with the trypanosome ESCRT system.
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Abstract
Faithful transmission of genetic material is essential for the survival of all organisms. Eukaryotic chromosome segregation is driven by the kinetochore that assembles onto centromeric DNA to capture spindle microtubules and govern the movement of chromosomes. Its molecular mechanism has been actively studied in conventional model eukaryotes, such as yeasts, worms, flies and human. However, these organisms are closely related in the evolutionary time scale and it therefore remains unclear whether all eukaryotes use a similar mechanism. The evolutionary origins of the segregation apparatus also remain enigmatic. To gain insights into these questions, it is critical to perform comparative studies. Here, we review our current understanding of the mitotic mechanism in Trypanosoma brucei, an experimentally tractable kinetoplastid parasite that branched early in eukaryotic history. No canonical kinetochore component has been identified, and the design principle of kinetochores might be fundamentally different in kinetoplastids. Furthermore, these organisms do not appear to possess a functional spindle checkpoint that monitors kinetochore-microtubule attachments. With these unique features and the long evolutionary distance from other eukaryotes, understanding the mechanism of chromosome segregation in T. brucei should reveal fundamental requirements for the eukaryotic segregation machinery, and may also provide hints about the origin and evolution of the segregation apparatus.
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Affiliation(s)
- Bungo Akiyoshi
- Sir William Dunn School of Pathology, University of Oxford, Oxford OX1 3RE, UK
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Vannerum K, De Rycke R, Pollier J, Goossens A, Inzé D, Vyverman AW. CHARACTERIZATION OF A RABE (RAS GENE FROM RAT BRAIN E) GTPASE EXPRESSED DURING MORPHOGENESIS IN THE UNICELLULAR GREEN ALGA MICRASTERIAS DENTICULATA (ZYGNEMATOPHYCEAE, STREPTOPHYTA)(1). JOURNAL OF PHYCOLOGY 2012; 48:682-692. [PMID: 27011085 DOI: 10.1111/j.1529-8817.2012.01170.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Rab GTPases are central regulators of cell shape in land plants by coordinating vesicle trafficking during morphogenesis. To date, relatively little is known about the role of these ubiquitous signaling proteins during cell growth in microalgae, in particular in the related charophyte algae. This article identifies the first charophyte Rab GTPase, MdRABE1, in Micrasterias denticulata Bréb., a convenient model organism for studying morphogenesis. Its expression correlated with the onset of morphogenesis, and structural analysis indicated that it belongs to the RABE (Ras gene from rat brain E) subclass. Confocal fluorescence and immunoelectron microscopy (IEM) of transiently GFP-MdRABE1 overexpressing interphase cells demonstrated that the GFP-MdRABE1 protein was localized to the endoplasmic reticulum, dictyosomes, exocytotic vesicles, the cell margin, the membranes of cell organelles, and in the isthmus zone around the nucleus. Although overexpression phenotyping of both N- and C-terminal green fluorescent protein (GFP) fusions failed to indicate additional functional evidence of the MdRABE1 protein due to mortality of those transgenic cells, its expression profile, bioinformatics, and intracellular localization suggest a role in vesicle trafficking during morphogenesis.
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Affiliation(s)
- Katrijn Vannerum
- Laboratory of Protistology and Aquatic Ecology, Department of Biology, Ghent University, Krijgslaan 281-S8, 9000 Gent, BelgiumDepartment of Plant Systems Biology, VIB, Technologiepark 927, 9052 Gent, BelgiumDepartment of Plant Biotechnology and Bioinformatics, Ghent University, Technologiepark 927, 9052 Gent, Belgium
| | - Riet De Rycke
- Laboratory of Protistology and Aquatic Ecology, Department of Biology, Ghent University, Krijgslaan 281-S8, 9000 Gent, BelgiumDepartment of Plant Systems Biology, VIB, Technologiepark 927, 9052 Gent, BelgiumDepartment of Plant Biotechnology and Bioinformatics, Ghent University, Technologiepark 927, 9052 Gent, Belgium
| | - Jacob Pollier
- Laboratory of Protistology and Aquatic Ecology, Department of Biology, Ghent University, Krijgslaan 281-S8, 9000 Gent, BelgiumDepartment of Plant Systems Biology, VIB, Technologiepark 927, 9052 Gent, BelgiumDepartment of Plant Biotechnology and Bioinformatics, Ghent University, Technologiepark 927, 9052 Gent, Belgium
| | - Alain Goossens
- Laboratory of Protistology and Aquatic Ecology, Department of Biology, Ghent University, Krijgslaan 281-S8, 9000 Gent, BelgiumDepartment of Plant Systems Biology, VIB, Technologiepark 927, 9052 Gent, BelgiumDepartment of Plant Biotechnology and Bioinformatics, Ghent University, Technologiepark 927, 9052 Gent, Belgium
| | - Dirk Inzé
- Laboratory of Protistology and Aquatic Ecology, Department of Biology, Ghent University, Krijgslaan 281-S8, 9000 Gent, BelgiumDepartment of Plant Systems Biology, VIB, Technologiepark 927, 9052 Gent, BelgiumDepartment of Plant Biotechnology and Bioinformatics, Ghent University, Technologiepark 927, 9052 Gent, Belgium
| | - And Wim Vyverman
- Laboratory of Protistology and Aquatic Ecology, Department of Biology, Ghent University, Krijgslaan 281-S8, 9000 Gent, BelgiumDepartment of Plant Systems Biology, VIB, Technologiepark 927, 9052 Gent, BelgiumDepartment of Plant Biotechnology and Bioinformatics, Ghent University, Technologiepark 927, 9052 Gent, Belgium
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The GTPase TcRjl of the human pathogen Trypanosoma cruzi is involved in the cell growth and differentiation. Biochem Biophys Res Commun 2012; 419:38-42. [PMID: 22326867 DOI: 10.1016/j.bbrc.2012.01.119] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2012] [Accepted: 01/25/2012] [Indexed: 11/20/2022]
Abstract
The protozoan parasite Trypanosoma cruzi, the etiological agent of Chagas Disease, undergoes through a complex life cycle where rounds of cell division and differentiation occur initially in the gut of triatominae vectors and, after transmission, inside of infected cells in vertebrate hosts. Members of the Ras superfamily of GTPases are molecular switches which play pivotal regulatory functions in cell growth and differentiation. We have previously described a novel GTPase in T. cruzi, TcRjl, which belongs to the RJL family of Ras-related GTP binding proteins. Here we show that most of TcRjl protein is found bound to GTP nucleotides and may be locked in this stage. In addition, we show that TcRjl is located close to the kinetoplast, in a region corresponding possibly to flagellar pocket of the parasite and the expression of a dominant-negative TcRjl construct (TcRjlS37N) displays a significative growth phenotype in reduced serum medium. Remarkably, overexpression of TcRjl inhibits differentiation of epimastigotes to trypomastigote forms and promotes the accumulation of intermediate differentiation stages. Our data suggest that TcRjl might play a role in the control of the parasite growth and differentiation.
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Abstract
The biogenesis of the ER Exit Site/Golgi Junction (EGJ) in bloodstream-form African trypanosomes is investigated using tagged markers for ER Exit Sites, the Golgi and the bilobe structure. The typical pattern is two EGJ in G1 phase (1 kinetoplast/1 nucleus, 1K1N) through S-phase (2K1N), duplication to four EGJ in post-mitotic cells (2K2N) and segregation of two EGJ to each daughter. Lesser cell percentages have elevated EGJ copy numbers in all stages, and blocking cell cycle progression results in even higher copy numbers. EGJs are closely aligned with the flagellar attachment zone (FAZ) indicating nucleation on the FAZ-associated ER (FAZ:ER). Only the most posterior EGJ in each cell is in proximity to the bilobe, which is located at the base of the FAZ filament near the mouth of the flagellar pocket. These results indicate that EGJ replication in bloodstream trypanosomes is not tightly coupled to the cell cycle. Furthermore, segregation of EGJ is not obligately mediated by the bilobe, rather assembly of the EGJ on the FAZ:ER, which is coupled to the flagellar cytoskeleton, apparently ensures segregation with fidelity during cytokinesis. These findings differ markedly from procyclic-form trypanosomes, and models highlighting these stage-specific differences in EGJ biogenesis are proposed.
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Affiliation(s)
- James D Bangs
- Department of Medical Microbiology & Immunology, University of Wisconsin School of Medicine and Public Health, Madison, WI 53706, USA.
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8
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Silverman JS, Schwartz KJ, Hajduk SL, Bangs JD. Late endosomal Rab7 regulates lysosomal trafficking of endocytic but not biosynthetic cargo in Trypanosoma brucei. Mol Microbiol 2011; 82:664-78. [PMID: 21923766 DOI: 10.1111/j.1365-2958.2011.07842.x] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
We present the first functional analysis of the small GTPase, TbRab7, in Trypanosoma brucei. TbRab7 defines discrete late endosomes closely juxtaposed to the terminal p67(+) lysosome. RNAi indicates that TbRab7 is essential in bloodstream trypanosomes. Initial rates of endocytosis were unaffected, but lysosomal delivery of cargo, including tomato lectin (TL) and trypanolytic factor (TLF) were blocked. These accumulate in a dispersed internal compartment of elevated pH, likely derived from the late endosome. Surface binding of TL but not TLF was reduced, suggesting that cellular distribution of flagellar pocket receptors is differentially regulated by TbRab7. TLF activity was reduced approximately threefold confirming that lysosomal delivery is critical for trypanotoxicity. Unexpectedly, delivery of endogenous proteins, p67 and TbCatL, were unaffected indicating that TbRab7 does not regulate biosynthetic lysosomal trafficking. Thus, unlike mammalian cells and yeast, lysosomal trafficking of endocytosed and endogenous proteins occur via different routes and/or are regulated differentially. TbRab7 silencing had no effect on a cryptic default pathway to the lysosome, suggesting that the default lysosomal reporters p67ΔTM, p67ΔCD and VSGΔGPI do not utilize the endocytic pathway as previously proposed. Surprisingly, conditional knockout indicates that TbRab7 may be non-essential in procyclic insect form trypanosomes.
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Affiliation(s)
- Jason S Silverman
- Department of Medical Microbiology and Immunology, University of Wisconsin School of Medicine and Public Health, Madison, WI 53706, USA
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9
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Gabernet-Castello C, DuBois KN, Nimmo C, Field MC. Rab11 function in Trypanosoma brucei: identification of conserved and novel interaction partners. EUKARYOTIC CELL 2011; 10:1082-94. [PMID: 21642507 PMCID: PMC3165442 DOI: 10.1128/ec.05098-11] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 04/30/2011] [Accepted: 05/24/2011] [Indexed: 11/20/2022]
Abstract
The Ras-like GTPase Rab11 is implicated in multiple aspects of intracellular transport, including maintenance of plasma membrane composition and cytokinesis. In metazoans, these functions are mediated in part via coiled-coil Rab11-interacting proteins (FIPs) acting as Rab11 effectors. Additional interaction between Rab11 and the exocyst subunit Sec15 connects Rab11 with exocytosis. We find that FIPs are metazoan specific, suggesting that other factors mediate Rab11 functions in nonmetazoans. We examined Rab11 interactions in Trypanosoma brucei, where endocytosis is well studied and the role of Rab11 in recycling well documented. TbSec15 and TbRab11 interact, demonstrating evolutionary conservation. By yeast two-hybrid screening, we identified additional Rab11 interaction partners. Tb927.5.1640 (designated RBP74) interacted with both Rab11 and Rab5. RBP74 shares a coiled-coil architecture with metazoan FIPs but is unrelated by sequence and appears to play a role in coordinating endocytosis and recycling. A second coiled-coil protein, Tb09.211.4830 (TbAZI1), orthologous to AZI1 in Homo sapiens, interacts exclusively with Rab11. AZI1 is restricted to taxa with motile cilia/flagella. These data suggest that Rab11 functions are mediated by evolutionarily conserved (i.e., AZI1 and Sec15) and potentially lineage-specific (RBP74) interactions essential for the integration of the endomembrane system.
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Affiliation(s)
- Carme Gabernet-Castello
- Department of Pathology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QP, United Kingdom
| | - Kelly N. DuBois
- Department of Pathology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QP, United Kingdom
| | - Camus Nimmo
- Department of Pathology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QP, United Kingdom
| | - Mark C. Field
- Department of Pathology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QP, United Kingdom
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Ulrich PN, Jimenez V, Park M, Martins VP, Atwood J, Moles K, Collins D, Rohloff P, Tarleton R, Moreno SNJ, Orlando R, Docampo R. Identification of contractile vacuole proteins in Trypanosoma cruzi. PLoS One 2011; 6:e18013. [PMID: 21437209 PMCID: PMC3060929 DOI: 10.1371/journal.pone.0018013] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2010] [Accepted: 02/22/2011] [Indexed: 11/19/2022] Open
Abstract
Contractile vacuole complexes are critical components of cell volume regulation
and have been shown to have other functional roles in several free-living
protists. However, very little is known about the functions of the contractile
vacuole complex of the parasite Trypanosoma cruzi, the
etiologic agent of Chagas disease, other than a role in osmoregulation.
Identification of the protein composition of these organelles is important for
understanding their physiological roles. We applied a combined proteomic and
bioinfomatic approach to identify proteins localized to the contractile vacuole.
Proteomic analysis of a T. cruzi fraction enriched for
contractile vacuoles and analyzed by one-dimensional gel electrophoresis and
LC-MS/MS resulted in the addition of 109 newly detected proteins to the group of
expressed proteins of epimastigotes. We also identified different peptides that
map to at least 39 members of the dispersed gene family 1 (DGF-1) providing
evidence that many members of this family are simultaneously expressed in
epimastigotes. Of the proteins present in the fraction we selected several
homologues with known localizations in contractile vacuoles of other organisms
and others that we expected to be present in these vacuoles on the basis of
their potential roles. We determined the localization of each by expression as
GFP-fusion proteins or with specific antibodies. Six of these putative proteins
(Rab11, Rab32, AP180, ATPase subunit B, VAMP1, and phosphate transporter)
predominantly localized to the vacuole bladder. TcSNARE2.1, TcSNARE2.2, and
calmodulin localized to the spongiome. Calmodulin was also cytosolic. Our
results demonstrate the utility of combining subcellular fractionation,
proteomic analysis, and bioinformatic approaches for localization of organellar
proteins that are difficult to detect with whole cell methodologies. The CV
localization of the proteins investigated revealed potential novel roles of
these organelles in phosphate metabolism and provided information on the
potential participation of adaptor protein complexes in their biogenesis.
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Affiliation(s)
- Paul N. Ulrich
- Center for Tropical and Emerging Global
Diseases and Department of Cellular Biology, University of Georgia, Athens,
Georgia, United States of America
| | - Veronica Jimenez
- Center for Tropical and Emerging Global
Diseases and Department of Cellular Biology, University of Georgia, Athens,
Georgia, United States of America
| | - Miyoung Park
- Center for Tropical and Emerging Global
Diseases and Department of Cellular Biology, University of Georgia, Athens,
Georgia, United States of America
| | - Vicente P. Martins
- Center for Tropical and Emerging Global
Diseases and Department of Cellular Biology, University of Georgia, Athens,
Georgia, United States of America
| | - James Atwood
- Complex Carbohydrate Research Center,
University of Georgia, Athens, Georgia, United States of America
| | - Kristen Moles
- Center for Tropical and Emerging Global
Diseases and Department of Cellular Biology, University of Georgia, Athens,
Georgia, United States of America
| | - Dalis Collins
- Center for Tropical and Emerging Global
Diseases and Department of Cellular Biology, University of Georgia, Athens,
Georgia, United States of America
| | - Peter Rohloff
- Center for Tropical and Emerging Global
Diseases and Department of Cellular Biology, University of Georgia, Athens,
Georgia, United States of America
| | - Rick Tarleton
- Center for Tropical and Emerging Global
Diseases and Department of Cellular Biology, University of Georgia, Athens,
Georgia, United States of America
| | - Silvia N. J. Moreno
- Center for Tropical and Emerging Global
Diseases and Department of Cellular Biology, University of Georgia, Athens,
Georgia, United States of America
| | - Ron Orlando
- Complex Carbohydrate Research Center,
University of Georgia, Athens, Georgia, United States of America
| | - Roberto Docampo
- Center for Tropical and Emerging Global
Diseases and Department of Cellular Biology, University of Georgia, Athens,
Georgia, United States of America
- * E-mail:
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de Paulo Martins V, Okura M, Maric D, Engman DM, Vieira M, Docampo R, Moreno SNJ. Acylation-dependent export of Trypanosoma cruzi phosphoinositide-specific phospholipase C to the outer surface of amastigotes. J Biol Chem 2010; 285:30906-17. [PMID: 20647312 DOI: 10.1074/jbc.m110.142190] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Phosphoinositide phospholipase C (PI-PLC) plays an essential role in cell signaling. A unique Trypanosoma cruzi PI-PLC (TcPI-PLC) is lipid-modified in its N terminus and localizes to the plasma membrane of amastigotes. Here, we show that TcPI-PLC is located onto the extracellular phase of the plasma membrane of amastigotes and that its N-terminal 20 amino acids are necessary and sufficient to target the fused GFP to the outer surface of the parasite. Mutagenesis of the predicted acylated residues confirmed that myristoylation of a glycine residue in the 2nd position and acyl modification of a cysteine in the 4th but not in the 8th or 15th position of the coding sequence are required for correct plasma membrane localization in T. cruzi epimastigotes or amastigotes. Interestingly, mutagenesis of the cysteine at the 8th position increased its flagellar localization. When expressed as fusion constructs with GFP, the N-terminal 6 and 10 amino acids fused to GFP are predominantly located in the cytosol and concentrated in a compartment that co-localizes with a Golgi complex marker. The N-terminal 20 amino acids of TcPI-PLC associate with lipid rafts when dually acylated. Taken together, these results indicate that N-terminal acyl modifications serve as a molecular addressing system for sending TcPI-PLC to the outer surface of the cell.
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Affiliation(s)
- Vicente de Paulo Martins
- Department of Cellular Biology, University of Georgia, Center for Tropical and Emerging Global Diseases, Athens, Georgia 30602, USA
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13
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Natesan SKA, Peacock L, Leung KF, Matthews KR, Gibson W, Field MC. The trypanosome Rab-related proteins RabX1 and RabX2 play no role in intracellular trafficking but may be involved in fly infectivity. PLoS One 2009; 4:e7217. [PMID: 19787065 PMCID: PMC2748683 DOI: 10.1371/journal.pone.0007217] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2009] [Accepted: 09/03/2009] [Indexed: 01/17/2023] Open
Abstract
Background Rab GTPases constitute the largest subgroup of the Ras superfamily and are primarily involved in vesicle targeting. The full extent of Rab family function is unexplored. Several divergent Rab-like proteins are known but few have been characterized. In Trypanosoma brucei there are sixteen Rab genes, but RabX1, RabX2 and RabX3 are divergent within canonical sequence regions. Where known, trypanosome Rab functions are broadly conserved when orthologous relationships may be robustly established, but specific functions for RabX1, X2 and X3 have yet to be determined. RabX1 and RabX2 originated via tandem duplication and subcellular localization places RabX1 at the endoplasmic reticulum, while RabX2 is at the Golgi complex, suggesting distinct functions. We wished to determine whether RabX1 and RabX2 are involved in vesicle transport or other cellular processes. Methodology/Principal Findings Using comparative genomics we find that RabX1 and RabX2 are restricted to trypanosomatids. Gene knockout indicates that RabX1 and RabX2 are non-essential. Simultaneous RNAi knockdown of both RabX1 and RabX2, while partial, was also non-lethal and may suggest non-redundant function, consistent with the distinct locations of the proteins. Analysis of the knockout cell lines unexpectedly failed to uncover a defect in exocytosis, endocytosis or in the morphology or location of multiple markers for the endomembrane system, suggesting that neither RabX1 nor RabX2 has a major role in intracellular transport. However, it was apparent that RabX1 and RabX2 knockout cells displayed somewhat enhanced survival within flies. Conclusions/Significance RabX1 and RabX2, two members of the trypanosome Rab subfamily, were shown to have no major detectable role in intracellular transport, despite the localization of each gene product to highly specific endomembrane compartments. These data extend the functional scope of Rab proteins in trypanosomes to include non-canonical roles in differentiation-associated processes in protozoa.
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Affiliation(s)
| | - Lori Peacock
- School of Biological Sciences, University of Bristol, Bristol, United Kingdom
| | - Ka Fai Leung
- Department of Pathology, University of Cambridge, Cambridge, United Kingdom
| | - Keith R. Matthews
- Institute of Immunology and Infection Research, University of Edinburgh, Edinburgh, United Kingdom
| | - Wendy Gibson
- School of Biological Sciences, University of Bristol, Bristol, United Kingdom
| | - Mark C. Field
- Department of Pathology, University of Cambridge, Cambridge, United Kingdom
- * E-mail:
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14
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Abstract
Golgi duplication in the protozoan parasite Trypanosoma brucei has been tracked using serial thin section three-dimensional reconstructions of transmission electron micrographs. The old Golgi maintains a constant size (approximately 0.060 microm(3)) throughout the cell cycle. A morphologically identifiable new Golgi appears at approximately 0.20 of the cell cycle (defined by the size of the nucleus and lasting about 9 h) and grows from approximately 0.018 microm(3) until it is the same size as the old Golgi (by approximately 0.55 of the cell cycle). Morphologically identifiable late Golgi appear at approximately 0.58 of the cell cycle, but their volume ( approximately 0.036 microm(3)) did not change significantly. Cryoimmunoelectron microscopy was used to identify candidates for the earliest new Golgi structures, and these comprised clusters of vesicles containing Golgi reassembly stacking protein (GRASP) near an endoplasmic reticulum exit site. These results, combined with earlier fluorescence data, suggest that the new Golgi begins functioning before cisternal stacks are formed.
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Affiliation(s)
- Jordan T Yelinek
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT, USA
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15
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Field MC, Lumb JH, Adung'a VO, Jones NG, Engstler M. Chapter 1 Macromolecular Trafficking and Immune Evasion in African Trypanosomes. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2009; 278:1-67. [DOI: 10.1016/s1937-6448(09)78001-3] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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16
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Marks DL, Bittman R, Pagano RE. Use of Bodipy-labeled sphingolipid and cholesterol analogs to examine membrane microdomains in cells. Histochem Cell Biol 2008; 130:819-32. [PMID: 18820942 PMCID: PMC3922293 DOI: 10.1007/s00418-008-0509-5] [Citation(s) in RCA: 101] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/09/2008] [Indexed: 01/28/2023]
Abstract
Much evidence has accumulated to show that cellular membranes such as the plasma membrane, contain multiple "microdomains" of differing lipid and protein composition and function. These domains are sometimes enriched in cholesterol and sphingolipids and are believed to be important structures for the regulation of many biological and pathological processes. This review focuses on the use of fluorescent (Bodipy) labeled analogs of sphingolipids and cholesterol to study such domains. We discuss the similarities between the behavior of Bodipy-cholesterol and natural cholesterol in artificial bilayers and in cultured cells, and the use of Bodipy-sphingolipid analogs to visualize membrane domains in living cells based on the concentration-dependent monomer-excimer fluorescence properties of the Bodipy-fluorophore. The use of Bodipy-D-erythro-lactosylceramide is highlighted for detection of domains on the plasma membrane and endosome membranes, and the importance of the sphingolipid stereochemistry in modulating domain formation is discussed. Finally, we suggest that Bodipy-sphingolipids may be useful in future studies to examine the relationship between membrane domains at the cell surface and domains enriched in other lipids and proteins on the inner leaflet of the plasma membrane.
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Affiliation(s)
- David L. Marks
- Thoracic Diseases Research Unit, Department of Medicine, Mayo Clinic College of Medicine, Stabile 8, 200 First Street, SW, Rochester, MN 55905-0001, USA
- Department of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine, Stabile 8, 200 First Street, SW, Rochester, MN 55905-0001, USA
| | - Robert Bittman
- Department of Chemistry and Biochemistry, Queens College, The City University of New York, Flushing, NY 11367, USA
| | - Richard E. Pagano
- Thoracic Diseases Research Unit, Department of Medicine, Mayo Clinic College of Medicine, Stabile 8, 200 First Street, SW, Rochester, MN 55905-0001, USA
- Department of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine, Stabile 8, 200 First Street, SW, Rochester, MN 55905-0001, USA
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17
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Abstract
Undoubtedly, there are fundamental processes driving the structural mechanics of cell division in eukaryotic organisms that have been conserved throughout evolution and are being revealed by studies on organisms such as yeast and mammalian cells. Precision of structural mechanics of cytokinesis is however probably no better illustrated than in the protozoa. A dramatic example of this is the protozoan parasite Trypanosoma brucei, a unicellular flagellated parasite that causes a devastating disease (African sleeping sickness) across Sub-Saharan Africa in both man and animals. As trypanosomes migrate between and within a mammalian host and the tsetse vector, there are periods of cell proliferation and cell differentiation involving at least five morphologically distinct cell types. Much of the existing cytoskeleton remains intact during these processes, necessitating a very precise temporal and spatial duplication and segregation of the many single-copy organelles. This structural precision is aiding progress in understanding these processes as we apply the excellent reverse genetics and post-genomic technologies available in this system. Here we outline our current understanding of some of the structural aspects of cell division in this fascinating organism.
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18
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de Graffenried CL, Ho HH, Warren G. Polo-like kinase is required for Golgi and bilobe biogenesis in Trypanosoma brucei. J Cell Biol 2008; 181:431-8. [PMID: 18443217 PMCID: PMC2364693 DOI: 10.1083/jcb.200708082] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2007] [Accepted: 03/27/2008] [Indexed: 11/22/2022] Open
Abstract
A bilobed structure marked by TbCentrin2 regulates Golgi duplication in the protozoan parasite Trypanosoma brucei. This structure must itself duplicate during the cell cycle for Golgi inheritance to proceed normally. We show here that duplication of the bilobed structure is dependent on the single polo-like kinase (PLK) homologue in T. brucei (TbPLK). Depletion of TbPLK leads to malformed bilobed structures, which is consistent with an inhibition of duplication and an increase in the number of dispersed Golgi structures with associated endoplasmic reticulum exit sites. These data suggest that the bilobe may act as a scaffold for the controlled assembly of the duplicating Golgi.
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19
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Ramirez IBR, de Graffenried CL, Ebersberger I, Yelinek J, He CY, Price A, Warren G. TbG63, a golgin involved in Golgi architecture in Trypanosoma brucei. J Cell Sci 2008; 121:1538-46. [PMID: 18411253 DOI: 10.1242/jcs.014324] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Golgins are coiled-coil proteins that have been implicated in the structure and function of the Golgi complex. Here, we identify and characterize a trypanosomal golgin, TbG63, showing that it has a C-terminal membrane anchor and an N-terminus that projects into the cytoplasm. TbG63 in procyclic parasites is localized to the Golgi and interacts with the active, GTP-form of TbRab1A. Overexpression of TbG63 has dramatic effects on Golgi architecture -- effects that require the N-terminus -- whereas depletion has little, if any, effect on the growth rate. By contrast, in the bloodstream form of the parasite, depletion of TbG63 slows growth, although it has no obvious effect on the transport of a variant surface glycoprotein (VSG) or on Golgi structure. TbG63 might be a useful tool to study the structure and functioning of the Golgi complex.
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20
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Selvapandiyan A, Kumar P, Morris JC, Salisbury JL, Wang CC, Nakhasi HL. Centrin1 is required for organelle segregation and cytokinesis in Trypanosoma brucei. Mol Biol Cell 2007; 18:3290-301. [PMID: 17567955 PMCID: PMC1951761 DOI: 10.1091/mbc.e07-01-0022] [Citation(s) in RCA: 80] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Centrin is a calcium-binding centrosome/basal body-associated protein involved in duplication and segregation of these organelles in eukaryotes. We had shown that disruption of one of the centrin genes (centrin1) in Leishmania amastigotes resulted in failure of both basal body duplication and cytokinesis. Here, we undertook to define the role of centrin1 (TbCen1) in the duplication and segregation of basal body and its associated organelles kinetoplast and Golgi, as well as its role in cytokinesis of the procyclic form of Trypanosoma brucei by depleting its protein using RNA inhibition methodology. TbCen1-depleted cells showed significant reduction in growth compared with control cells. Morphological analysis of these cells showed they were large and pleomorphic with multiple detached flagella. Both immunofluorescence assays using organelle-specific antibodies and electron microscopic analysis showed that TbCen1-deficient cells contained multiple basal bodies, kinetoplasts, Golgi, and nuclei. These multiple organelles were, however, closely clustered together, indicating duplication without segregation in the absence of centrin. This failure in organelle segregation may be the likely cause of inhibition of cytokinesis, suggesting for the first time a new and unique role for centrin in the segregation of organelles without affecting their multiplication in the procyclic form of T. brucei.
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Affiliation(s)
- Angamuthu Selvapandiyan
- *Division of Emerging and Transfusion Transmitted Diseases, Center for Biologics Evaluation and Research, Food and Drug Administration, Bethesda, MD 20892
| | - Praveen Kumar
- Department of Pharmaceutical Chemistry, University of California, San Francisco, CA 94143
| | - James C. Morris
- Department of Genetics and Biochemistry, Clemson University, Clemson, SC 29634; and
| | | | - Ching C. Wang
- Department of Pharmaceutical Chemistry, University of California, San Francisco, CA 94143
| | - Hira L. Nakhasi
- *Division of Emerging and Transfusion Transmitted Diseases, Center for Biologics Evaluation and Research, Food and Drug Administration, Bethesda, MD 20892
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21
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Abstract
Trypanosomes are members of the kinetoplastida, a group of divergent protozoan parasites responsible for considerable morbidity and mortality worldwide. These organisms have highly complex life cycles requiring modification of their cell surface together with engagement of immune evasion systems to effect survival; both processes intimately involve the membrane trafficking system. The completion of three trypanosomatid and several additional protist genomes in the last few years is providing an exciting opportunity to evaluate, at the molecular level, the evolution and diversity of membrane trafficking across deep evolutionary time as well as to analyse in unprecedented detail the membrane trafficking systems of trypanosomes.
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Affiliation(s)
- Mark C Field
- Department of Pathology, University of Cambridge, Tennis Court Road, Cambridge, CB2 1QP, UK.
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22
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Abstract
The accurate duplication of cellular organelles is important to ensure propagation through successive generations. The semi-conserved replication of DNA and DNA-containing organelles has been well studied, but the mechanisms used to duplicate most other organelles remain elusive. These include the centrosomes, which act as microtubule organizing centres during interphase and orient the mitotic spindle poles during mitosis. Centrosomes can also act as basal bodies, nucleating the growth of cilia or flagella. Even less understood are the mechanisms used to duplicate membrane-bound organelles that do not contain DNA. These include organelles involved in the secretory pathway such as the endoplasmic reticulum and the Golgi apparatus. This review will summarize the current knowledge of Golgi biogenesis in simple eukaryotic organisms, in particular, two protozoan parasites, Toxoplasma gondii and Trypanosoma brucei.
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Affiliation(s)
- Cynthia Y He
- Department of Cell Biology, Ludwig Institute for Cancer Research, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520-8002, USA.
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23
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Lodhi IJ, Chiang SH, Chang L, Vollenweider D, Watson RT, Inoue M, Pessin JE, Saltiel AR. Gapex-5, a Rab31 guanine nucleotide exchange factor that regulates Glut4 trafficking in adipocytes. Cell Metab 2007; 5:59-72. [PMID: 17189207 PMCID: PMC1779820 DOI: 10.1016/j.cmet.2006.12.006] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/17/2006] [Revised: 10/27/2006] [Accepted: 12/11/2006] [Indexed: 10/23/2022]
Abstract
Insulin stimulates glucose uptake by promoting translocation of the Glut4 glucose transporter from intracellular storage compartments to the plasma membrane. In the absence of insulin, Glut4 is retained intracellularly; the mechanism underlying this process remains uncertain. Using the TC10-interacting protein CIP4 as bait in a yeast two-hybrid screen, we cloned a RasGAP and VPS9 domain-containing protein, Gapex-5/RME-6. The VPS9 domain is a guanine nucleotide exchange factor for Rab31, a Rab5 subfamily GTPase implicated in trans-Golgi network (TGN)-to-endosome trafficking. Overexpression of Rab31 blocks insulin-stimulated Glut4 translocation, whereas knockdown of Rab31 potentiates insulin-stimulated Glut4 translocation and glucose uptake. Gapex-5 is predominantly cytosolic in untreated cells; its overexpression promotes intracellular retention of Glut4 in adipocytes. Insulin recruits the CIP4/Gapex-5 complex to the plasma membrane, thus reducing Rab31 activity and permitting Glut4 vesicles to translocate to the cell surface, where Glut4 docks and fuses to transport glucose into the cell.
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Affiliation(s)
- Irfan J. Lodhi
- Life Sciences Institute
- Cellular and Molecular Biology Program University of Michigan Ann Arbor, MI 48109
| | | | | | - Daniel Vollenweider
- Department of Pharmacological Sciences Stony Brook University Stony Brook, NY 11794
| | - Robert T. Watson
- Department of Pharmacological Sciences Stony Brook University Stony Brook, NY 11794
| | | | - Jeffrey E. Pessin
- Department of Pharmacological Sciences Stony Brook University Stony Brook, NY 11794
| | - Alan R. Saltiel
- Life Sciences Institute
- Departments of Internal Medicine and Molecular and Integrative Physiology
- Cellular and Molecular Biology Program University of Michigan Ann Arbor, MI 48109
- *Corresponding author: Alan R. Saltiel Life Sciences Institute University of Michigan 210 Washtenaw Ave. Ann Arbor, MI 48109
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24
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Subramanya S, Mensa-Wilmot K. Regulated cleavage of intracellular glycosylphosphatidylinositol in a trypanosome. Peroxisome-to-endoplasmic reticulum translocation of a phospholipase C. FEBS J 2006; 273:2110-26. [PMID: 16649989 DOI: 10.1111/j.1742-4658.2006.05225.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Cell exposure to hypo-osmolarity and alkalinity triggers a spectrum of responses including activation of phospholipases. Glycosylphosphatidylinositol-specific phospholipase C (GPI-PLC) is expressed in Trypanosoma brucei, a protozoan parasite that causes human African trypanosomiasis. We examined possible contributions of GPI-PLC to the response of T. brucei to hypo-osmotic or mildly alkaline conditions. GPIs were detected at the endoplasmic reticulum (ER). They were cleaved after exposure of T. brucei to hypo-osmolarity or mild alkalinity, which also, strikingly, caused translocation of GPI-PLC from glycosomes (peroxisomes) to the ER. A catalytically inactive Gln81Leu mutant of GPI-PLC failed to cleave GPIs despite being transported from glycosomes to the ER after hypo-osmotic or mild alkaline treatment of the parasites. In contrast, a Cys347Ser mutant of the enzyme could not exit glycosomes after treatment of cells expressing the protein with mild base or hypo-osmotic buffer. We conclude that: (a) GPI-PLC contributes to loss of GPIs in T. brucei treated with hypo-osmotic or mildly alkaline buffer; (b) access of GPI-PLC to its substrate in vivo can be regulated post-translationally; (c) translocation of GPI-PLC from glycosomes to the ER is important for in vivo cleavage of GPIs; (d) Cys347 is part of a peptide motif required for post-translational targeting of GPI-PLC to the ER. Glycosome-to-ER movement of GPI-PLC reveals a novel pathway for intracellular protein traffic. The physiological significance of GPI digestion in cells exposed to mildly alkalinity or hypo-osmolarity is discussed.
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Affiliation(s)
- Sandesh Subramanya
- Department of Cellular Biology, University of Georgia, Athens, GA 30602, USA
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25
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Hall BS, Gabernet-Castello C, Voak A, Goulding D, Natesan SK, Field MC. TbVps34, the trypanosome orthologue of Vps34, is required for Golgi complex segregation. J Biol Chem 2006; 281:27600-12. [PMID: 16835237 DOI: 10.1074/jbc.m602183200] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Phosphoinositides are important regulators of numerous cellular functions. The yeast class III phosphatidylinositol 3-kinase Vps34p, and its human orthologue hVPS34, are implicated in control of several key pathways, including endosome to lysosome transport, retrograde endosome to Golgi traffic, multivesicular body formation, and autophagy. We have identified the Vps34p orthologue in the African trypanosome, TbVps34. Knockdown of TbVps34 expression by RNA interference induces a severe growth defect, with a post-mitotic block to cytokinesis accompanied by a variety of morphological abnormalities. GFP2xFYVE, a chimeric protein that specifically binds phosphatidylinositol 3-phosphate, localizes to the trypanosome endosomal system and is delocalized under TbVps34 RNA interference (RNAi), confirming that TbVps34 is an authentic phosphatidylinositol 3-kinase. Expression of GFP2xFYVE enhances the TbVps34 RNAi-associated growth defect, suggesting a synthetic interaction via competition for phosphatidylinositol 3-phosphate-binding sites with endogenous FYVE domain proteins. Endocytosis of a fluid phase marker is unaffected by TbVps34 RNAi, but receptor-mediated endocytosis of transferrin and transport of concanavalin A to the lysosome are both impaired, confirming a role in membranous endocytic trafficking for TbVps34. TbVps34 knockdown inhibits export of variant surface glycoprotein, indicating a function in exocytic transport. Ultrastructural analysis revealed a highly extended Golgi apparatus following TbVps34 RNAi, whereas expression of the Golgi marker red fluorescent protein-GRASP (Grp1 (general receptor for phosphoinositides-1)-associated scaffold protein) demonstrated that trypanosomes are able to duplicate the Golgi complex but failed to complete segregation during mitosis, despite faithful replication and segregation of basal bodies and the kinetoplast. These observations implicate TbVps34 as having a role in coordinating segregation of the Golgi complex at cell division.
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Affiliation(s)
- Belinda S Hall
- Department of Biological Sciences, Imperial College of Science, Technology and Medicine, London SW7 2AY, UK
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26
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Ho HH, He CY, de Graffenried CL, Murrells LJ, Warren G. Ordered assembly of the duplicating Golgi in Trypanosoma brucei. Proc Natl Acad Sci U S A 2006; 103:7676-81. [PMID: 16672362 PMCID: PMC1472504 DOI: 10.1073/pnas.0602595103] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The new Golgi in the protozoan parasite Trypanosoma brucei grows near to the old and adjacent to the growing new endoplasmic reticulum exit site. Growth is now shown to be at least a two-stage process, in which a representative matrix marker (GRASP) and enzyme (GntB) are delivered to the site of assembly, followed approximately 10 min later by a COPI component (epsilon-COP) and a trans-Golgi network (TGN) marker (GRIP70). A secretory cargo marker (signal sequence-YFP) appeared early near the new endoplasmic reticulum exit site but did not enter the Golgi until the second stage. Together these data suggest that structural and enzymatic components of the new Golgi stack are laid down first, followed by those needed to move and sort the cargo passing through it.
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Affiliation(s)
- Helen H. Ho
- Department of Cell Biology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520
| | - Cynthia Y. He
- Department of Cell Biology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520
| | | | - Lindsay J. Murrells
- Department of Cell Biology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520
| | - Graham Warren
- Department of Cell Biology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520
- *To whom correspondence should be addressed. E-mail:
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27
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Helms MJ, Ambit A, Appleton P, Tetley L, Coombs GH, Mottram JC. Bloodstream form Trypanosoma brucei depend upon multiple metacaspases associated with RAB11-positive endosomes. J Cell Sci 2006; 119:1105-17. [PMID: 16507595 DOI: 10.1242/jcs.02809] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Trypanosoma brucei possesses five metacaspase genes. Of these, MCA2 and MCA3 are expressed only in the mammalian bloodstream form of the parasite, whereas MCA5 is expressed also in the insect procyclic form. Triple RNAi analysis showed MCA2, MCA3 and MCA5 to be essential in the bloodstream form, with parasites accumulating pre-cytokinesis. Nevertheless, triple null mutants (deltamca2/3deltamca5) could be isolated after sequential gene deletion. Thereafter, deltamca2/3deltamca5 mutants were found to grow well both in vitro in culture and in vivo in mice. We hypothesise that metacaspases are essential for bloodstream form parasites, but they have overlapping functions and their progressive loss can be compensated for by activation of alternative biochemical pathways. Analysis of deltamca2/3deltamca5 revealed no greater or lesser susceptibility to stresses reported to initiate programmed cell death, such as treatment with prostaglandin D2. The metacaspases were found to colocalise with RAB11, a marker for recycling endosomes. However, variant surface glycoprotein (VSG) recycling processes and the degradation of internalised anti-VSG antibody were found to occur similarly in wild type, deltamca2/3deltamca5 and triple RNAi induced parasites. Thus, the data provide no support for the direct involvement of T. brucei metacaspases in programmed cell death and suggest that the proteins have a function associated with RAB11 vesicles that is independent of known recycling processes of RAB11-positive endosomes.
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Affiliation(s)
- Matthew J Helms
- Wellcome Centre for Molecular Parasitology, The Anderson College, University of Glasgow, Glasgow G11 6NU, UK
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28
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Oli MW, Cotlin LF, Shiflett AM, Hajduk SL. Serum resistance-associated protein blocks lysosomal targeting of trypanosome lytic factor in Trypanosoma brucei. EUKARYOTIC CELL 2006; 5:132-9. [PMID: 16400175 PMCID: PMC1360256 DOI: 10.1128/ec.5.1.132-139.2006] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Trypanosoma brucei brucei is the causative agent of nagana in cattle and can infect a wide range of mammals but is unable to infect humans because it is susceptible to the innate cytotoxic activity of normal human serum. A minor subfraction of human high-density lipoprotein (HDL) containing apolipoprotein A-I (apoA-I), apolipoprotein L-I (apoL-I), and haptoglobin-related protein (Hpr) provides this innate protection against T. b. brucei infection. This HDL subfraction, called trypanosome lytic factor (TLF), kills T. b. brucei following receptor binding, endocytosis, and lysosomal localization. Trypanosoma brucei rhodesiense, which is morphologically and physiologically indistinguishable from T. b. brucei, is resistant to TLF-mediated killing and causes human African sleeping sickness. Human infectivity by T. b. rhodesiense correlates with the evolution of a resistance-associated protein (SRA) that is able to ablate TLF killing. To examine the mechanism of TLF resistance, we transfected T. b. brucei with an epitope-tagged SRA gene. Transfected T. b. brucei expressed SRA mRNA at levels comparable to those in T. b. rhodesiense and was highly resistant to TLF. In the SRA-transfected cells, intracellular trafficking of TLF was altered, with TLF being mainly localized to a subset of SRA-containing cytoplasmic vesicles but not to the lysosome. These results indicate that the cellular distribution of TLF is influenced by SRA expression and may directly determine the organism's susceptibility to TLF.
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Affiliation(s)
- Monika W Oli
- Global Infectious Disease Program, Josephine Bay Paul Center, Marine Biological Laboratory, 7 MBL Street, Woods Hole, Massachusetts 02543, USA
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29
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Abstract
Centrins are highly conserved components of the centrosome, which in the parasitic protozoan T. brucei comprises the basal body and nucleates the flagellum used for locomotion. Here, we found TbCentrin2 in an additional bi-lobed structure near to the Golgi apparatus. One lobe was associated with the old Golgi, and the other became associated with the newly forming Golgi as the cell grew. Depletion of TbCentrin1 inhibited duplication of the basal body, whereas depletion of TbCentrin2 also inhibited duplication of the Golgi. Thus, a Centrin2-containing structure distinct from the basal body appears to mark the site for new Golgi assembly.
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Affiliation(s)
- Cynthia Y He
- Department of Cell Biology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520, USA
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30
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Hartmann J, Hu K, He CY, Pelletier L, Roos DS, Warren G. Golgi and centrosome cycles in Toxoplasma gondii. Mol Biochem Parasitol 2005; 145:125-7. [PMID: 16266757 DOI: 10.1016/j.molbiopara.2005.09.015] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2005] [Revised: 09/19/2005] [Accepted: 09/23/2005] [Indexed: 11/21/2022]
Affiliation(s)
- Jan Hartmann
- Department of Cell Biology, Ludwig Institute for Cancer Research, Yale University School of Medicine, New Haven, CT 06520, USA
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31
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Ramos FP, Araripe JR, Urményi TP, Silva R, Cunha e Silva NL, Leite Fontes CF, da Silveira JF, Rondinelli E. Characterization of RAB-like4, the first identified RAB-like protein from Trypanosoma cruzi with GTPase activity. Biochem Biophys Res Commun 2005; 333:808-17. [PMID: 15975556 DOI: 10.1016/j.bbrc.2005.05.183] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2005] [Accepted: 05/26/2005] [Indexed: 11/25/2022]
Abstract
RAB proteins, which belong to the RAS superfamily, regulate exocytic and endocytic pathways of eukaryotic cells, controlling vesicle docking and fusion. Few RAB proteins have been identified in parasites. Molecular markers for cellular compartments are important to studies concerning about the protein traffic in Trypanosoma cruzi, the causal agent of Chagas disease. In this work, we describe the characterization of TcRABL4, the first RAB-like gene identified in T. cruzi (GenBank Accession No.: ), present as a single-copy gene. TcRABL4 contains all five consensus RAB motifs but lacks cysteine residues at the C terminus, which are essential to isoprenylation, an absolute prerequisite for membrane association of these proteins. TcRABL4 is a functional GTPase that is able to bind and hydrolyze GTP, and its gene is transcribed as a single 1.2 kb mRNA in epimastigotes. TcRABL4 appears to be differentially regulated in the three cell forms of the parasite, and the protein is not associated to membranes, unlike other RAB proteins. It is possible that TcRABL4 may be a member of a novel family of small GTPases.
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Affiliation(s)
- Fabiane Pereira Ramos
- Laboratório de Metabolismo Macromolecular Firmino Torres de Castro, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, CCS, Cidade Universitária, Rio de Janeiro 21949-900, Brazil
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32
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Ackers JP, Dhir V, Field MC. A bioinformatic analysis of the RAB genes of Trypanosoma brucei. Mol Biochem Parasitol 2005; 141:89-97. [PMID: 15811530 DOI: 10.1016/j.molbiopara.2005.01.017] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2003] [Revised: 11/30/2003] [Accepted: 01/22/2005] [Indexed: 10/25/2022]
Abstract
RAB proteins are small GTPases with vital roles in eukaryotic intracellular transport; orthologous RABs appear to fulfil similar functions in diverse organisms. Trypanosoma brucei spp., the causative organisms of Old World trypanosomiasis of humans and domestic animals, have extremely effective endocytic and exocytic mechanisms that are likely to be involved in maintenance of infection, making study of these systems of importance. Taking advantage of the essential completion of the T. brucei genome, we have re-examined the T. brucei RABs (TbRABs) so far described and identified a total of 16. BLAST searches and phylogenetic analysis show that nine of the TbRABs can confidently be assigned as orthologues or homologues of known RAB proteins from higher eukaryotes, and four more with reasonable probability. The core endocytic pathway is probably similar in complexity to yeast, whilst the early exocytic pathway appears to be more complex than in yeast. Two of the TbRAB family (RAB23 and 28) with clear mammalian orthologues appear to be unusual, and may be involved in nuclear processes and are described in more detail in an accompanying paper. Three TbRABs appear, however, to have no close homologues and may fulfil specialised functions in this organism. The availability of a complete set of TbRABs--which includes orthologues of the RABs responsible for control of the core of the endomembrane system (i.e. RAB1, 2, 4-7 and 11)--provides a first overview of the trafficking complexity that is present within a kinetoplastid parasite. Based on these homologies we suggest a systematic nomenclature for the TbRABs to reflect their functional homologies. This information is of importance both from the perspective of understanding the evolution and diversity of eukaryotic trafficking, but also in providing a framework by which to understand protein processing, trafficking, endocytosis and other related processes in these parasites.
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Affiliation(s)
- John P Ackers
- Department of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT, UK
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33
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Araripe JR, Ramos FP, Cunha e Silva NL, Urményi TP, Silva R, Leite Fontes CF, da Silveira JF, Rondinelli E. Characterization of a RAB5 homologue in Trypanosoma cruzi. Biochem Biophys Res Commun 2005; 329:638-45. [PMID: 15737633 DOI: 10.1016/j.bbrc.2005.02.021] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2005] [Indexed: 11/30/2022]
Abstract
RAB proteins are small GTPases involved in exocytic and endocytic pathways of eukaryotic cells, controlling vesicle docking and fusion. RABs show a remarkable specificity in subcellular localization, so they can be used as molecular markers for studying protein trafficking in Trypanosoma cruzi, the causal agent of Chagas' disease. RAB5 is a component of early endosomes. It has been identified in kinetoplastids such as Trypanosoma brucei and Leishmania donovani. In this work, we describe the characterization of the complete coding sequence of a RAB5 gene homologue in T. cruzi (TcRAB5, GenBank Accession No. AY730667). It is present as a single copy gene, located at chromosomal bands XIII and XIV. TcRAB5 shares the highest degrees of similarity (71%) and identity (63%) with Trypanosoma brucei rhodesiense RAB5a and contains all five characteristic RAB motifs. TcRAB5 is transcribed as a single 1.5kb mRNA in epimastigotes. Its transcript was also detected in the other two forms of the parasite, metacyclic trypomastigotes and spheromastigotes. The recombinant TcRAB5 protein was able to bind and hydrolyze GTP. The identification of proteins involved in T. cruzi endo- and exocytic pathways may generate cellular compartment markers, an invaluable tool to better understand the vesicular transport in this parasite.
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Affiliation(s)
- Júlia Rolão Araripe
- Laboratório de Metabolismo Macromolecular Firmino Torres de Castro, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, CCS, Cidade Universitária, Rio de Janeiro 21949-900, Brazil
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Dhir V, Allen CL, Field MC. Perturbation of local endogenous expression by insertion of Pol I expression constructs into the genome of Trypanosoma brucei. Exp Parasitol 2005; 109:198-200. [PMID: 15713453 DOI: 10.1016/j.exppara.2004.11.003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2004] [Revised: 11/12/2004] [Accepted: 11/12/2004] [Indexed: 11/25/2022]
Abstract
Manipulation of gene expression is a common tool for the elucidation of biological function. Here we investigated the effects of over-expression in trypanosomes of a small GTPase, TbRABX1, using 2D gel electrophoresis and mass-spectrometry. An over-expression construct was targeting to the tubulin locus of chromosome I for stable integration and expression. Unexpectedly we observed alterations to the expression of gene products, i.e., tubulin, from surrounding regions of the genome; this effect was shown to be general and not dependent on the identity of the ectopic gene being expressed. These data suggest that local perturbation of the genome by insertion of DNA constructs can have wider impacts on gene expression, which need to be monitored.
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Affiliation(s)
- Vivek Dhir
- Department of Biological Sciences, Imperial College, London SW7 2AY, UK
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35
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Engstler M, Boshart M. Cold shock and regulation of surface protein trafficking convey sensitization to inducers of stage differentiation in Trypanosoma brucei. Genes Dev 2004; 18:2798-811. [PMID: 15545633 PMCID: PMC528899 DOI: 10.1101/gad.323404] [Citation(s) in RCA: 138] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Transmission of a protozoan parasite from a vertebrate to invertebrate host is accompanied by cellular differentiation. The signals from the environment that trigger the process are poorly understood. The model parasite Trypanosoma brucei proliferates in the mammalian bloodstream and in the tsetse fly. On ingestion by the tsetse, the trypanosome undergoes a rapid differentiation that is marked by replacement of the variant surface glycoprotein (VSG) coat with GPI-anchored EP and GPEET procyclins. Here we show that a cold shock of DeltaT > 15 degrees C is sufficient to reversibly induce high-level expression of the insect stage-specific EP gene in the mammalian bloodstream stages of T. brucei. The 3'-UTR of the EP mRNA is necessary and sufficient for the increased expression. During cold shock, EP protein accumulates in the endosomal compartment in the proliferating, slender, bloodstream stage, whereas the EP is present on the plasma membrane in the quiescent, stumpy, bloodstream stage. Thus, there is a novel developmentally regulated cell surface access control mechanism for a GPI-anchored protein. In addition to inducing EP expression, cold shock results in the acquisition of sensitivity to micromolar concentrations of cis-aconitate and citrate by stumpy but not slender bloodstream forms. The cis-aconitate and citrate commit stumpy bloodstream cells to differentiation to the procyclic stage along with rapid initial proliferation. We propose a hierarchical model of three events that regulate differentiation after transmission to the tsetse: sensing the temperature change, surface access of a putative receptor, and sensing of a chemical cue.
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Affiliation(s)
- Markus Engstler
- Ludwig-Maximilians-Universität, Department Biologie I, Genetik, 80638 München, Germany
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36
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Araripe JR, Cunha e Silva NL, Leal ST, de Souza W, Rondinelli E. Trypanosoma cruzi: TcRAB7 protein is localized at the Golgi apparatus in epimastigotes. Biochem Biophys Res Commun 2004; 321:397-402. [PMID: 15358190 DOI: 10.1016/j.bbrc.2004.06.159] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2004] [Indexed: 11/15/2022]
Abstract
In mammalian cells, the Rab7 protein is a key element of late endocytic membrane traffic. Several results suggest that it is involved in the transport from early to late endosome or from late endosome to lysosome. We have previously characterized a Rab7 gene homologue (TcRAB7) in Trypanosoma cruzi. Now, using an affinity-purified antibody specific to TcRAB7 protein we have determined that it is localized at the Golgi apparatus of the parasite. Our results indicate that the T. cruzi Rab7 homologue may function in a different route than its counterparts in mammalian cells.
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Affiliation(s)
- Júlia R Araripe
- Lab. Metabolismo Macromolecular Firmino Torres de Castro, Instituto de Biofisica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, Brazil
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37
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Abstract
Trypanosomes belong to the order kinetoplastida, an early diverging group of organisms in the eukaryotic lineage. The principal reasons for interest in these organisms are twofold; they provide a superb distant triangulation point from which to assess global features of eukaryotic biology and, more importantly, they are representative of a number of pathogenic parasitic protozoa with a huge public health impact --Trypanosoma brucei, T. cruzi and Leishmania spp. Recent advances in the study of intracellular transport in T. brucei have been considerable, and a fuller picture of the complexity, function and role that the endomembrane system plays in trypanosomes is finally emerging.
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Affiliation(s)
- Mark C Field
- Department of Biological Sciences, Imperial College, London, UK.
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38
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Field MC, Allen CL, Dhir V, Goulding D, Hall BS, Morgan GW, Veazey P, Engstler M. New approaches to the microscopic imaging of Trypanosoma brucei. MICROSCOPY AND MICROANALYSIS : THE OFFICIAL JOURNAL OF MICROSCOPY SOCIETY OF AMERICA, MICROBEAM ANALYSIS SOCIETY, MICROSCOPICAL SOCIETY OF CANADA 2004; 10:621-636. [PMID: 15525435 DOI: 10.1017/s1431927604040942] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/20/2003] [Indexed: 05/24/2023]
Abstract
Protozoan parasites are fearsome pathogens responsible for a substantial proportion of human mortality, morbidity, and economic hardship. The principal disease agents are members of the orders Apicomplexa (Plasmodium, Toxoplasma, Eimeria) and Kinetoplastida (Trypanosomes, Leishmania). The majority of humans are at risk from infection from one or more of these organisms, with profound effects on the economy, social structure and quality of life in endemic areas; Plasmodium itself accounts for over one million deaths per annum, and an estimated 4 x 10(7) disability-adjusted life years (DALYs), whereas the Kinetoplastida are responsible for over 100,000 deaths per annum and 4 x 10(6) DALYs. Current control strategies are failing due to drug resistance and inadequate implementation of existing public health strategies. Trypanosoma brucei, the African Trypanosome, has emerged as a favored model system for the study of basic cell biology in Kinetoplastida, because of several recent technical advances (transfection, inducible expression systems, and RNA interference), and these advantages, together with genome sequencing efforts are widely anticipated to provide new strategies of therapeutic intervention. Here we describe a suite of methods that have been developed for the microscopic analysis of T. brucei at the light and ultrastructural levels, an essential component of analysis of gene function and hence identification of therapeutic targets.
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Affiliation(s)
- Mark C Field
- Wellcome Trust Laboratories for Molecular Parasitology, Department of Biological Sciences, Imperial College, Exhibition Road, London SW7 2AY, UK.
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39
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Torres C, Pérez-Victoria FJ, Parodi-Talice A, Castanys S, Gamarro F. Characterization of an ABCA-like transporter involved in vesicular trafficking in the protozoan parasite Trypanosoma cruzi. Mol Microbiol 2004; 54:632-46. [PMID: 15491356 DOI: 10.1111/j.1365-2958.2004.04304.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Protozoan parasites are responsible of important healthy problems, among others malaria, leishmaniasis and trypanosomiasis. The present work reports the characterization of the first mammalian ATP-binding cassette transporter, subfamily A (ABCA)-like in Trypanosoma cruzi. TcABC1 is a single copy gene differentially expressed along the life cycle of the parasite, being absent in its infective form. TcABC1 localizes to the plasma membrane, flagellar pocket and intracellular vesicles. Functional studies of TcABC1 in transfected parasites suggest that the protein is implicated in intracellular trafficking, as determined by the analysis of endocytosis and exocytosis events. The accumulation of the endocytic markers FM4-64 and NBD-SM is increased in transfected parasites. Similarly, ectophosphatase and ectoATPase activities are increased in TcABC1 overproducers. Indeed, transmission electronic microscopy analysis showed a higher number of intracellular vesicles in TcABC1 transfectants. Taken together, these results suggest that the protein is involved in the endocytic and exocytic pathways of T. cruzi.
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Affiliation(s)
- Cristina Torres
- Instituto de Parasitología y Biomedicina López-Neyra, Consejo Superior de Investigaciones Científicas, Granada, Spain
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40
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He CY, Ho HH, Malsam J, Chalouni C, West CM, Ullu E, Toomre D, Warren G. Golgi duplication in Trypanosoma brucei. ACTA ACUST UNITED AC 2004; 165:313-21. [PMID: 15138289 PMCID: PMC2172185 DOI: 10.1083/jcb.200311076] [Citation(s) in RCA: 136] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Duplication of the single Golgi apparatus in the protozoan parasite Trypanosoma brucei has been followed by tagging a putative Golgi enzyme and a matrix protein with variants of GFP. Video microscopy shows that the new Golgi appears de novo, near to the old Golgi, about two hours into the cell cycle and grows over a two-hour period until it is the same size as the old Golgi. Duplication of the endoplasmic reticulum (ER) export site follows exactly the same time course. Photobleaching experiments show that the new Golgi is not the exclusive product of the new ER export site. Rather, it is supplied, at least in part, by material directly from the old Golgi. Pharmacological experiments show that the site of the new Golgi and ER export is determined by the location of the new basal body.
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Affiliation(s)
- Cynthia Y He
- Department of Cell Biology, Ludwig Institute for Cancer Research, Yale University School of Medicine, 333 Cedar St., P.O. Box 208002, New Haven, CT 06520-8002, USA
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41
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Morgan GW, Goulding D, Field MC. The Single Dynamin-like Protein of Trypanosoma brucei Regulates Mitochondrial Division and Is Not Required for Endocytosis. J Biol Chem 2004; 279:10692-701. [PMID: 14670954 DOI: 10.1074/jbc.m312178200] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Members of the evolutionarily conserved dynamin-related GTPase family mediate numerous cellular membrane remodeling events. Dynamin family functions include the scission of clathrin-coated pits from the plasma membrane, mitochondrial fission, and chloroplast division. Here we report that the divergent eukaryote Trypanosoma brucei possesses a single dynamin family gene, which we have designated TbDLP. Furthermore, a single dynamin family gene is also found in the Leishmania major and Trypanosoma vivax genomes, indicating that this is a conserved feature among the kinetoplastida. TbDLP is most homologous to the DMN/DRP family of dynamin-like proteins. Indirect immunofluorescence microscopy reveals that TbDLP is distributed in punctate structures within the cell that partially co-localize with the mitochondrion when labeled with MitoTracker. To define TbDLP function, we have used RNA interference to silence the TbDLP gene. Reduction of TbDLP protein levels causes a profound alteration in mitochondrial morphology without affecting the structure of other membrane-bound compartments, including the endocytic and exocytic apparatus. The mitochondrial profiles present in wild type trypanosomes fuse and collapse in the mutant cells, and by electron microscopy the mitochondria are found to contain an accumulation of constriction sites. These findings demonstrate TbDLP functions in division of the mitochondrial membrane. Most significantly, as TbDLP is the sole member of the dynamin family in this organism, scission of clathrin-coated pits involved in protein trafficking through the highly active endocytic system in trypanosomes must function in the absence of dynamin. The evolutionary implications of these findings are discussed.
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Affiliation(s)
- Gareth W Morgan
- Wellcome Trust Laboratories for Molecular Parasitology, Department of Biological Sciences, Imperial College, Exhibition Road, London SW7 2AY, United Kingdom
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42
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Nepomuceno-Silva JL, de Melo LDB, Mendonçã SM, Paixão JC, Lopes UG. RJLs: a new family of Ras-related GTP-binding proteins. Gene 2004; 327:221-32. [PMID: 14980719 DOI: 10.1016/j.gene.2003.11.010] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2003] [Revised: 10/30/2003] [Accepted: 11/14/2003] [Indexed: 10/26/2022]
Abstract
The Ras superfamily of GTP binding proteins encompasses several gene families that regulate a plethora of events in the eukaryotic cell. Here we describe a novel branch of this superfamily which we have named RJLs. These are present in many unicellular organisms and also in deuterostomes but apparently missing in some intermediary phyla, suggesting an intriguing possibility of lateral gene transference between lower and higher eukaryotes. RJLs lack classical membrane targeting signals and the conserved glutamine residue that coordinates GTP hydrolysis in other proteins from the Ras superfamily. Interestingly, chordate orthologues are chimeras fused to "J" domains in their C-terminal, suggesting that these proteins recruit Hsc70 to specific sites in the cell. Expression analysis of RJLs from chordates suggests predominant expression in nervous tissues, possibly reflecting a role for RJLs in the development or maintenance of the sophisticated chordate nervous system.
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Affiliation(s)
- José L Nepomuceno-Silva
- Instituto de Biofísica Carlos Chagas Filho, Universidades Federal do Rio de Janeiro, Rio de Janeiro, RJ 21949-900, Brazil
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43
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Allen CL, Goulding D, Field MC. Clathrin-mediated endocytosis is essential in Trypanosoma brucei. EMBO J 2003; 22:4991-5002. [PMID: 14517238 PMCID: PMC204465 DOI: 10.1093/emboj/cdg481] [Citation(s) in RCA: 191] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2003] [Revised: 05/09/2003] [Accepted: 08/04/2003] [Indexed: 12/15/2022] Open
Abstract
In Trypanosoma brucei, the plasma membrane is dominated by glycosylphosphatidylinositol (GPI)-anchored proteins. Endocytic activity correlates with expression levels of the clathrin heavy chain TbCLH, and additional evidence suggests that rapid endocytosis may play a role in evasion of the immune response. TbCLH is present on both endocytic vesicles and post-Golgi elements, suggesting a similar range of functions in trypanosomes to higher eukaryotes. We have assessed the role of TbCLH using RNA interference (RNAi). Suppression of TbCLH expression results in rapid lethality in the bloodstream stage, the form most active for endocytosis. The flagellar pocket, the site of both endocytosis and exocytosis, becomes massively enlarged, suggesting that membrane delivery is unaffected but removal is blocked. Endocytosis in TbCLHRNAi cells is essentially undetectable, suggesting that clathrin-mediated mechanisms are the major route for endocytosis in T.brucei and hence that GPI-anchored proteins are endocytosed by clathrin-dependent pathways in trypanosomes. In contrast, a massive internal accumulation of vesicles and significant alterations to trafficking of a lysosomal protein were observed in the procyclic stage, indicating developmental variation in clathrin function in trypanosomes.
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Affiliation(s)
- Clare L Allen
- Wellcome Trust Laboratories for Molecular Parasitology, Department of Biological Sciences, Imperial College, Exhibition Road, London SW7 2AY, UK
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44
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Abstract
Golgi inheritance proceeds via sequential biogenesis and partitioning phases. Although little is known about Golgi growth and replication (biogenesis), ultrastructural and fluorescence analyses have provided a detailed, though still controversial, perspective of Golgi partitioning during mitosis in mammalian cells. Partitioning requires the fragmentation of the juxtanuclear ribbon of interconnected Golgi stacks into a multitude of tubulovesicular clusters. This process is choreographed by a cohort of mitotic kinases and an inhibition of heterotypic and homotypic Golgi membrane-fusion events. Our model posits that accurate partitioning occurs early in mitosis by the equilibration of Golgi components on either side of the metaphase plate. Disseminated Golgi components then coalesce to regenerate Golgi stacks during telophase. Semi-intact cell and cell-free assays have accurately recreated these processes and allowed their molecular dissection. This review attempts to integrate recent findings to depict a more coherent, synthetic molecular picture of mitotic Golgi fragmentation and reassembly. Of particular importance is the emerging concept of a highly regulated and dynamic Golgi structural matrix or template that interfaces with cargo receptors, Golgi enzymes, Rab-GTPases, and SNAREs to tightly couple biosynthetic transport to Golgi architecture. This structural framework may be instructive for Golgi biogenesis and may encode sufficient information to ensure accurate Golgi inheritance, thereby helping to resolve some of the current discrepancies between different workers.
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45
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Grünfelder CG, Engstler M, Weise F, Schwarz H, Stierhof YD, Morgan GW, Field MC, Overath P. Endocytosis of a glycosylphosphatidylinositol-anchored protein via clathrin-coated vesicles, sorting by default in endosomes, and exocytosis via RAB11-positive carriers. Mol Biol Cell 2003; 14:2029-40. [PMID: 12802073 PMCID: PMC165095 DOI: 10.1091/mbc.e02-10-0640] [Citation(s) in RCA: 102] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Recently, proteins linked to glycosylphosphatidylinositol (GPI) residues have received considerable attention both for their association with lipid microdomains and for their specific transport between cellular membranes. Basic features of trafficking of GPI-anchored proteins or glycolipids may be explored in flagellated protozoan parasites, which offer the advantage that their surface is dominated by these components. In Trypanosoma brucei, the GPI-anchored variant surface glycoprotein (VSG) is efficiently sorted at multiple intracellular levels, leading to a 50-fold higher membrane concentration at the cell surface compared with the endoplasmic reticulum. We have studied the membrane and VSG flow at an invagination of the plasma membrane, the flagellar pocket, the sole region for endo- and exocytosis in this organism. VSG enters trypanosomes in large clathrin-coated vesicles (135 nm in diameter), which deliver their cargo to endosomes. In the lumen of cisternal endosomes, VSG is concentrated by default, because a distinct class of small clathrin-coated vesicles (50-60 nm in diameter) budding from the cisternae is depleted in VSG. TbRAB11-positive cisternal endosomes, containing VSG, fragment by an unknown process giving rise to intensely TbRAB11- as well as VSG-positive, disk-like carriers (154 nm in diameter, 34 nm in thickness), which are shown to fuse with the flagellar pocket membrane, thereby recycling VSG back to the cell surface.
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46
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Wilson RJMI. Spotlight: re-evaluating replicating organelles. Protist 2003; 154:3-4. [PMID: 12812365 DOI: 10.1078/143446103764928431] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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47
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Morgan GW, Hall BS, Denny PW, Field MC, Carrington M. The endocytic apparatus of the kinetoplastida. Part II: machinery and components of the system. Trends Parasitol 2002; 18:540-6. [PMID: 12482539 DOI: 10.1016/s1471-4922(02)02392-9] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Endocytic systems within eukaryotic cells are a diverse set of intracellular transport pathways responsible for uptake, recycling, interaction with the exocytic system and degradation of molecules. Each of these pathways requires the interaction of distinct protein components that function in macromolecule sorting, control of transport rates and in membrane biogenesis. In the second of two articles on kinetoplastida endocytosis, the endocytic system in Trypanosoma brucei is considered as a model, and the molecules that control this system and the protein components of the endocytic pathway are discussed. We also consider novel mechanisms for sorting that have been proposed to operate in trypanosomes.
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Affiliation(s)
- Gareth W Morgan
- Wellcome Trust Laboratories for Molecular Parasitology, Dept of Biological Sciences, Imperial College of Science, Technology and Medicine, London, UK
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48
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McConville MJ, Ilgoutz SC, Teasdale RD, Foth BJ, Matthews A, Mullin KA, Gleeson PA. Targeting of the GRIP domain to the trans-Golgi network is conserved from protists to animals. Eur J Cell Biol 2002; 81:485-95. [PMID: 12416725 DOI: 10.1078/0171-9335-00268] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The GRIP domain, found in a family of coiled-coil peripheral membrane Golgi proteins, is a specific targeting sequence for the trans-Golgi network of animal cells. In this study we show that a coiled-coil protein with a GRIP domain occurs in the primitive eukaryote, Trypanosoma brucei, and that reporter proteins containing this domain can be used as a marker for the poorly characterized trans Golgi/trans-Golgi network of trypanosomatid parasites. The T. brucei GRIP domain, when fused to the carboxyl terminus of the green fluorescent protein (GFP-TbGRIP), was efficiently localized to the Golgi apparatus of transfected COS cells. Overexpression of GFP-TbGRIP in COS cells displaced the endogenous GRIP protein, GCC1p, from the Golgi apparatus indicating that the trypanosomatid and mammalian GRIP sequences interact with similar membrane determinants. GFP fusion proteins containing either the T. brucei GRIP domain or the human p230 GRIP (p230GRIP) domain were also expressed in the trypanosomatid parasite, Leishmania mexicana, and localized by fluorescence and immuno-electron microscopy to the trans face of the single Golgi apparatus and a short tubule that extended from the Golgi apparatus. Binding of GFP-p230GRIP to Golgi membranes in L. mexicana was abrogated by mutation of a critical tyrosine residue in the p230 GRIP domain. The levels of GFP-GRIP fusion proteins were dramatically reduced in stationary-phase L. mexicana promastigotes, suggesting that specific Golgi trafficking steps may be down-regulated as the promastigotes cease dividing. This study provides a protein marker for the trans-Golgi network of trypanosomatid parasites and suggests that the GRIP domain binds to a membrane component that has been highly conserved in eukaryotic evolution.
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Affiliation(s)
- Malcolm J McConville
- Russell Grimwade School of Biochemistry and Molecular Biology, University of Melbourne, Victoria, Australia
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49
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Alexander DL, Schwartz KJ, Balber AE, Bangs JD. Developmentally regulated trafficking of the lysosomal membrane protein p67 in Trypanosoma brucei. J Cell Sci 2002; 115:3253-63. [PMID: 12140257 DOI: 10.1242/jcs.115.16.3253] [Citation(s) in RCA: 89] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
p67 is a lysosomal type I membrane glycoprotein of Trypanosoma brucei. In procyclic stage cells p67 trafficks to the lysosome without modification, but in the bloodstream stage Golgi processing adds poly-N-acetyllactosamine to N-glycans. In both stages proteolytic fragmentation occurs in the lysosome, but turnover is approximately nine times faster in bloodstream cells. Trafficking of wildtype p67 and mutants missing the cytoplasmic (p67ΔCD) or cytoplasmic/transmembrane domains (p67ΔTM) was monitored by pulse-chase,surface biotinylation and immunofluorescence. Overexpressed wildtype p67 trafficks normally in procyclics, but some leaks to the cell surface suggesting that the targeting machinery is saturable. p67ΔCD and p67ΔTM are delivered to the cell surface and secreted, respectively. The membrane/cytoplasmic domains function correctly in procyclic cells when fused to GFP indicating that these domains are sufficient for stage-specific lysosomal targeting. In contrast, p67 wildtype and deletion reporters are overwhelmingly targeted to the lysosome and degraded in bloodstream cells. These findings suggest that either redundant developmentally regulated targeting signals/machinery are operative in this stage or that the increased endocytic activity of bloodstream cells prevents export of the deletion reporters.
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Affiliation(s)
- David L Alexander
- The Department of Medical Microbiology and Immunology, University of Wisconsin-Madison Medical School, Madison, WI 53706, USA
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50
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Pelletier L, Stern CA, Pypaert M, Sheff D, Ngô HM, Roper N, He CY, Hu K, Toomre D, Coppens I, Roos DS, Joiner KA, Warren G. Golgi biogenesis in Toxoplasma gondii. Nature 2002; 418:548-52. [PMID: 12152082 DOI: 10.1038/nature00946] [Citation(s) in RCA: 157] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Two models have been put forward to explain the growth of new Golgi during the cell cycle. The first suggests that a new Golgi grows out of the endoplasmic reticulum by de novo synthesis. The second suggests that a pre-existing Golgi is needed for the growth of a new one, that is, the Golgi is an autonomously replicating organelle. To resolve this issue, we have exploited the simplicity of the apicomplexan parasite Toxoplasma gondii, which has only a single Golgi stack. Here we show, by using video fluorescence microscopy and three-dimensional reconstructions of serial thin sections, that the Golgi grows by a process of lateral extension followed by medial fission. Further fission leads to the inheritance by each daughter of a pair of Golgi structures, which then coalesce to re-form a single Golgi. Our results indicate that new Golgi grow by autonomous duplication and raise the possibility that the Golgi is a paired structure that is analogous to centrioles.
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Affiliation(s)
- Laurence Pelletier
- Department of Cell Biology, Ludwig Institute for Cancer Research, Yale University School of Medicine, New Haven, Connecticut 06520, USA
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