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Tenaglia AH, Luján LA, Ríos DN, Molina CR, Midlej V, Iribarren PA, Berazategui MA, Torri A, Saura A, Peralta DO, Rodríguez-Walker M, Fernández EA, Petiti JP, Serradell MC, Gargantini PR, Sparwasser T, Alvarez VE, de Souza W, Luján HD. Antibodies to variable surface antigens induce antigenic variation in the intestinal parasite Giardia lamblia. Nat Commun 2023; 14:2537. [PMID: 37137944 PMCID: PMC10156722 DOI: 10.1038/s41467-023-38317-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2023] [Accepted: 04/25/2023] [Indexed: 05/05/2023] Open
Abstract
The genomes of most protozoa encode families of variant surface antigens. In some parasitic microorganisms, it has been demonstrated that mutually exclusive changes in the expression of these antigens allow parasites to evade the host's immune response. It is widely assumed that antigenic variation in protozoan parasites is accomplished by the spontaneous appearance within the population of cells expressing antigenic variants that escape antibody-mediated cytotoxicity. Here we show, both in vitro and in animal infections, that antibodies to Variant-specific Surface Proteins (VSPs) of the intestinal parasite Giardia lamblia are not cytotoxic, inducing instead VSP clustering into liquid-ordered phase membrane microdomains that trigger a massive release of microvesicles carrying the original VSP and switch in expression to different VSPs by a calcium-dependent mechanism. This novel mechanism of surface antigen clearance throughout its release into microvesicles coupled to the stochastic induction of new phenotypic variants not only changes current paradigms of antigenic switching but also provides a new framework for understanding the course of protozoan infections as a host/parasite adaptive process.
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Affiliation(s)
- Albano H Tenaglia
- Centro de Investigación y Desarrollo en Inmunología y Enfermedades Infecciosas (CIDIE), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)/Universidad Católica de Córdoba (UCC), X5016HDK, Córdoba, Argentina
- Centro de Investigaciones en Química Biológica de Córdoba (CIQUIBIC), CONICET, Universidad Nacional de Córdoba, Córdoba, Argentina
| | - Lucas A Luján
- Centro de Investigación y Desarrollo en Inmunología y Enfermedades Infecciosas (CIDIE), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)/Universidad Católica de Córdoba (UCC), X5016HDK, Córdoba, Argentina
| | - Diego N Ríos
- Centro de Investigación y Desarrollo en Inmunología y Enfermedades Infecciosas (CIDIE), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)/Universidad Católica de Córdoba (UCC), X5016HDK, Córdoba, Argentina
- Clínica Universitaria Reina Fabiola, Universidad Católica de Córdoba, Córdoba, Argentina
| | - Cecilia R Molina
- Centro de Investigación y Desarrollo en Inmunología y Enfermedades Infecciosas (CIDIE), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)/Universidad Católica de Córdoba (UCC), X5016HDK, Córdoba, Argentina
| | - Victor Midlej
- Instituto de Biofísica Carlos Chagas Filho and Centro Nacional de Biologia Estrutural e Bioimagem (CENABIO), Universidade Federal do Rio de Janeiro (UFRJ), 21941-170, Rio de Janeiro, Brazil
- Instituto Oswaldo Cruz, Fundação Oswaldo Cruz (FIOCRUZ), 21040-900, Rio de Janeiro, Brazil
| | - Paula A Iribarren
- Instituto de Investigaciones Biotecnológicas (IIBIO), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)/Universidad Nacional de General San Martín (UNSAM), B1650HMP, Buenos Aires, Argentina
| | - María A Berazategui
- Instituto de Investigaciones Biotecnológicas (IIBIO), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)/Universidad Nacional de General San Martín (UNSAM), B1650HMP, Buenos Aires, Argentina
- Department of Life Sciences, Sir Alexander Fleming Building, Imperial College London, London, UK
| | - Alessandro Torri
- Centro de Investigación y Desarrollo en Inmunología y Enfermedades Infecciosas (CIDIE), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)/Universidad Católica de Córdoba (UCC), X5016HDK, Córdoba, Argentina
- Viruses and RNA Interference Unit, CNRS Unité Mixte de Recherche, Institut Pasteur, Paris, France
| | - Alicia Saura
- Centro de Investigación y Desarrollo en Inmunología y Enfermedades Infecciosas (CIDIE), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)/Universidad Católica de Córdoba (UCC), X5016HDK, Córdoba, Argentina
- Cátedra de Química Biológica, Facultad de Ciencias de la Salud, Universidad Nacional de Córdoba, Córdoba, Argentina
| | - Damián O Peralta
- Centro de Investigación y Desarrollo en Inmunología y Enfermedades Infecciosas (CIDIE), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)/Universidad Católica de Córdoba (UCC), X5016HDK, Córdoba, Argentina
| | - Macarena Rodríguez-Walker
- Centro de Investigación y Desarrollo en Inmunología y Enfermedades Infecciosas (CIDIE), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)/Universidad Católica de Córdoba (UCC), X5016HDK, Córdoba, Argentina
| | - Elmer A Fernández
- Centro de Investigación y Desarrollo en Inmunología y Enfermedades Infecciosas (CIDIE), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)/Universidad Católica de Córdoba (UCC), X5016HDK, Córdoba, Argentina
- Fundación para el progreso de la Medicina, Córdoba, Argentina
| | - Juan P Petiti
- Instituto de Investigaciones en Ciencias de la Salud (INICSA), Centro de Microscopía Electrónica, Facultad de Ciencias Médicas. CONICET/Universidad Nacional de Córdoba, X5016HUA, Córdoba, Argentina
| | - Marianela C Serradell
- Centro de Investigación y Desarrollo en Inmunología y Enfermedades Infecciosas (CIDIE), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)/Universidad Católica de Córdoba (UCC), X5016HDK, Córdoba, Argentina
- Laboratorio de Parasitología y Micología, Departamento de Bioquímica Clínica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, X5016HUA, Córdoba, Argentina
| | - Pablo R Gargantini
- Centro de Investigación y Desarrollo en Inmunología y Enfermedades Infecciosas (CIDIE), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)/Universidad Católica de Córdoba (UCC), X5016HDK, Córdoba, Argentina
| | - Tim Sparwasser
- Institute of Medical Microbiology and Hygiene, University Medical Center of the Johannes Gutenberg-University Mainz, Mainz, Germany
| | - Vanina E Alvarez
- Instituto de Investigaciones Biotecnológicas (IIBIO), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)/Universidad Nacional de General San Martín (UNSAM), B1650HMP, Buenos Aires, Argentina
| | - Wanderley de Souza
- Instituto de Biofísica Carlos Chagas Filho and Centro Nacional de Biologia Estrutural e Bioimagem (CENABIO), Universidade Federal do Rio de Janeiro (UFRJ), 21941-170, Rio de Janeiro, Brazil
| | - Hugo D Luján
- Centro de Investigación y Desarrollo en Inmunología y Enfermedades Infecciosas (CIDIE), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)/Universidad Católica de Córdoba (UCC), X5016HDK, Córdoba, Argentina.
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Exosome Biogenesis in the Protozoa Parasite Giardia lamblia: A Model of Reduced Interorganellar Crosstalk. Cells 2019; 8:cells8121600. [PMID: 31835439 PMCID: PMC6953089 DOI: 10.3390/cells8121600] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2019] [Revised: 11/19/2019] [Accepted: 11/20/2019] [Indexed: 11/17/2022] Open
Abstract
: Extracellular vesicles (EVs) facilitate intercellular communication and are considered a promising therapeutic tool for the treatment of infectious diseases. These vesicles involve microvesicles (MVs) and exosomes and selectively transfer proteins, lipids, mRNAs, and microRNAs from one cell to another. While MVs are formed by extrusion of the plasma membrane, exosomes are a population of vesicles of endosomal origin that are stored inside the multivesicular bodies (MVBs) as intraluminal vesicles (ILVs) and are released when the MVBs fuse with the plasma membrane. Biogenesis of exosomes may be driven by the endosomal sorting complex required for transport (ESCRT) machinery or may be ESCRT independent, and it is still debated whether these are entirely separate pathways. In this manuscript, we report that the protozoan parasite, Giardia lamblia, although lacking a classical endo-lysosomal pathway, is able to produce and release exosome-like vesicles (ElV). By using a combination of biochemical and cell biology analyses, we found that the ElVs have the same size, shape, and protein and lipid composition as exosomes described for other eukaryotic cells. Moreover, we established that some endosome/lysosome peripheral vacuoles (PVs) contain ILV during the stationary phase. Our results indicate that ILV formation and ElV release depend on the ESCRT-associated AAA+-ATPase Vps4a, Rab11, and ceramide in this parasite. Interestingly, EIV biogenesis and release seems to occur in Giardia despite the fact that this parasite has lost most of the ESCRT machinery components during evolution and is unable to produce ceramide de novo. The differences in protozoa parasite EV composition, origin, and release may reveal functional and structural properties of EVs and, thus, may provide information on cell-to-cell communication and on survival mechanisms.
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Alvarado ME, Rubiano C, Calvo E, Gómez V, Wasserman M. Experimental and bioinformatic characterization of CaBP2933 an EF-Hand protein of Giardia intestinalis. Mol Biochem Parasitol 2017; 214:65-68. [PMID: 28373093 DOI: 10.1016/j.molbiopara.2017.03.010] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2016] [Revised: 03/27/2017] [Accepted: 03/29/2017] [Indexed: 01/17/2023]
Abstract
Giardia intestinalis is a parasite that inhabits the small intestine of humans. This parasite is a divergent eukaryote with a compact genome. The calcium ion is an essential messenger in cell signaling. Calcium's role as a messenger is mediated through calcium-binding proteins (CaBPs) that decode the message. The most important family of CaBPs is the EF-Hand protein family. In this study we have explored the role of EF-Hand protein CaBP2933. We analyzed its location, confirmed its ability to bind calcium and identified some of its interacting proteins. Take together our results suggest that CaBP2933 is involved in vesicular trafficking during encystation, via an interaction with kinesin-3 motor protein.
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Affiliation(s)
- Magda E Alvarado
- Laboratorio de Investigaciones Básicas en Bioquímica- LIBBIQ, Universidad Nacional de Colombia, Calle 44 No. 45-67, Bogotá, Colombia.
| | - Claudia Rubiano
- Laboratorio de Investigaciones Básicas en Bioquímica- LIBBIQ, Universidad Nacional de Colombia, Calle 44 No. 45-67, Bogotá, Colombia
| | - Eliana Calvo
- Laboratorio de Investigaciones Básicas en Bioquímica- LIBBIQ, Universidad Nacional de Colombia, Calle 44 No. 45-67, Bogotá, Colombia
| | - Vanessa Gómez
- Laboratorio de Investigaciones Básicas en Bioquímica- LIBBIQ, Universidad Nacional de Colombia, Calle 44 No. 45-67, Bogotá, Colombia
| | - Moisés Wasserman
- Laboratorio de Investigaciones Básicas en Bioquímica- LIBBIQ, Universidad Nacional de Colombia, Calle 44 No. 45-67, Bogotá, Colombia
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Touz MC, Rivero MR, Miras SL, Bonifacino JS. Lysosomal protein trafficking in Giardia lamblia: common and distinct features. Front Biosci (Elite Ed) 2012; 4:1898-909. [PMID: 22202006 DOI: 10.2741/511] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Giardia is a flagellated protozoan parasite that has to face different microenvironments during its life cycle in order to survive. All cells exchange materials with the extracellular medium through the reciprocal processes of endocytosis and secretion. Unlike more evolved cells, Giardia lacks a defined endosomal/lysosomal system, but instead possesses peripheral vacuoles that play roles in endocytosis, degradation, recycling, and secretion of proteins during growth and differentiation of the parasite. This review focuses on recent reports defining the role of different molecules involved in protein trafficking to the peripheral vacuoles, and discusses possible mechanisms of receptor recycling. Since Giardia is an early-branching protist, the study of this parasite may lead to a clearer understanding of the minimal machinery required for protein transport in eukaryotic cells.
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Affiliation(s)
- Maria C Touz
- Instituto de Investigacion Medica Mercedes y Martin Ferreyra, INIMEC - CONICET, Friuli 2434, Cordoba, Argentina.
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Faso C, Hehl AB. Membrane trafficking and organelle biogenesis in Giardia lamblia: use it or lose it. Int J Parasitol 2011; 41:471-80. [PMID: 21296082 DOI: 10.1016/j.ijpara.2010.12.014] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2010] [Revised: 12/23/2010] [Accepted: 12/24/2010] [Indexed: 01/06/2023]
Abstract
The secretory transport capacity of Giardia trophozoites is perfectly adapted to the changing environment in the small intestine of the host and is able to deploy essential protective surface coats as well as molecules which act on epithelia. These lumen-dwelling parasites take up nutrients by bulk endocytosis through peripheral vesicles or by receptor-mediated transport. The environmentally-resistant cyst form is quiescent but poised for activation following stomach passage. Its versatility and fidelity notwithstanding, the giardial trafficking systems appear to be the product of a general secondary reduction process geared towards minimization of all components and machineries identified to date. Since membrane transport is directly linked to organelle biogenesis and maintenance, less complexity also means loss of organelle structures and functions. A case in point is the Golgi apparatus which is missing as a steady-state organelle system. Only a few basic Golgi functions have been experimentally demonstrated in trophozoites undergoing encystation. Similarly, mitochondrial remnants have reached a terminally minimized state and appear to be functionally restricted to essential iron-sulfur protein maturation processes. Giardia's minimized organization combined with its genetic tractability provides unique opportunities to study basic principles of secretory transport in an uncluttered cellular environment. Not surprisingly, Giardia is gaining increasing attention as a model for the investigation of gene regulation, organelle biogenesis, and export of simple but highly protective cell wall biopolymers, a hallmark of all perorally transmitted protozoan and metazoan parasites.
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Affiliation(s)
- Carmen Faso
- Institute of Parasitology, University of Zurich, Winterthurerstrasse 266a, 8057 Zurich, Switzerland
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Giardia intestinalis: Expression of ubiquitin, glucosamine-6-phosphate and cyst wall protein genes during the encystment process. Exp Parasitol 2011; 127:382-6. [DOI: 10.1016/j.exppara.2010.08.017] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2010] [Revised: 08/16/2010] [Accepted: 08/19/2010] [Indexed: 11/23/2022]
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Rivero MR, Miras SL, Quiroga R, Rópolo AS, Touz MC. Giardia lamblia low-density lipoprotein receptor-related protein is involved in selective lipoprotein endocytosis and parasite replication. Mol Microbiol 2011; 79:1204-19. [PMID: 21205007 DOI: 10.1111/j.1365-2958.2010.07512.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
As Giardia lamblia is unable to synthesize cholesterol de novo, this steroid might be obtained from the host's intestinal milieu by endocytosis of lipoproteins. In this work, we identified a putative Giardia lamblia low-density lipoprotein receptor-related proteins (GlLRP), a type I membrane protein, which shares the substrate N-terminal binding domain and a FXNPXY-type endocytic motif with human LRPs. Expression of tagged GlLRP showed that it was localized predominantly in the endoplasmic reticulum, lysosomal-like peripheral vacuoles and plasma membrane. However, the FXNPXY-deleted GlLRP was retained at the plasma membrane suggesting that it is abnormally transported and processed. The low-density lipoprotein and chylomicrons interacted with GlLRP, with this interaction being necessary for lipoprotein internalization and cell proliferation. Finally, we show that GlLRP binds directly to the medium subunit of Giardia adaptor protein 2, indicating that receptor-mediated internalization occurs through an adaptin mechanism.
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Affiliation(s)
- Maria R Rivero
- Instituto de Investigación Médica Mercedes y Martín Ferreyra, INIMEC - CONICET, Friuli 2434, Córdoba, Argentina
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Davids BJ, Gilbert MA, Liu Q, Reiner DS, Smith AJ, Lauwaet T, Lee C, McArthur AG, Gillin FD. An atypical proprotein convertase in Giardia lamblia differentiation. Mol Biochem Parasitol 2010; 175:169-80. [PMID: 21075147 DOI: 10.1016/j.molbiopara.2010.11.008] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2009] [Revised: 10/29/2010] [Accepted: 11/05/2010] [Indexed: 01/24/2023]
Abstract
Proteolytic activity is important in the lifecycles of parasites and their interactions with hosts. Cysteine proteases have been best studied in Giardia, but other protease classes have been implicated in growth and/or differentiation. In this study, we employed bioinformatics to reveal the complete set of putative proteases in the Giardia genome. We identified 73 peptidase homologs distributed over 5 catalytic classes in the genome. Serial analysis of gene expression of the G. lamblia lifecycle found thirteen protease genes with significant transcriptional variation over the lifecycle, with only one serine protease transcript upregulated late in encystation. The translated gene sequence of this encystation-specific transcript was most similar to eukaryotic subtilisin-like proprotein convertases (SPC), although the typical catalytic triad was not identified. Epitope-tagged gSPC protein expressed in Giardia under its own promoter was upregulated during encystation with highest expression in cysts and it localized to encystation-specific secretory vesicles (ESV). Total gSPC from encysting cells produced proteolysis in gelatin gels that co-migrated with the epitope-tagged protease in immunoblots. Immuno-purified gSPC also had gelatinase activity. To test whether endogenous gSPC activity is involved in differentiation, trophozoites and cysts were exposed to the specific serine proteinase inhibitor 4-(2-aminoethyl)-benzenesulfonyl fluoride hydrochloride (AEBSF). After 21 h encystation, a significant decrease in ESV was observed with 1mM AEBSF and by 42 h the number of cysts was significantly reduced, but trophozoite growth was not inhibited. Concurrently, levels of cyst wall proteins 1 and 2, and AU1-tagged gSPC protein itself were decreased. Excystation of G. muris cysts was also significantly reduced in the presence of AEBSF. These results support the idea that serine protease activity is essential for Giardia encystation and excystation.
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Affiliation(s)
- B J Davids
- Department of Pathology, University of California, San Diego, CA 92103-8416, USA.
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Rivero MR, Kulakova L, Touz MC. Long double-stranded RNA produces specific gene downregulation in Giardia lamblia. J Parasitol 2010; 96:815-9. [PMID: 20476805 DOI: 10.1645/ge-2406.1] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
In many eukaryotes, the introduction of double-stranded RNA (dsRNA) into cells triggers the degradation of mRNAs through a post-transcriptional gene-silencing mechanism called RNA interference or RNAi. In the present study, we found that endogenous long-dsRNA was substantially more effective at producing interference than endogenous, or exogenous, short-dsRNA expression in Giardia lamblia . The effects of this interference were not evident in the highly expressed protein tubulin or the stage-specific cyst wall protein 2. However, long-dsRNA caused potent and specific interference in the medium subunits of adaptins, the RNA-dependent RNA polymerase, and the exogenous green fluorescence protein. Our results suggest that the ability of dsRNA antisense to inhibit the expression of these specific types of proteins is indicative of a gene-specific mechanism.
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Affiliation(s)
- Maria R Rivero
- Instituto de Investigación Médica Mercedes y Martín Ferreyra, INIMEC-CONICET, Friuli 2434, Córdoba, Argentina
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Abstract
The eukaryotic intestinal parasite Giardia intestinalis was first described in 1681, when Antonie van Leeuwenhoek undertook a microscopic examination of his own diarrhoeal stool. Nowadays, although G. intestinalis is recognized as a major worldwide contributor to diarrhoeal disease in humans and other mammals, the disease mechanisms are still poorly understood. Owing to its reduced complexity and proposed early evolutionary divergence, G. intestinalis is used as a model eukaryotic system for studying many basic cellular processes. In this Review we discuss recent discoveries in the molecular cell biology and pathogenesis of G. intestinalis.
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Xiao Y, Yin J, Jiang N, Xiang M, Hao L, Lu H, Sang H, Liu X, Xu H, Ankarklev J, Lindh J, Chen Q. Seroepidemiology of human Toxoplasma gondii infection in China. BMC Infect Dis 2010; 10:4. [PMID: 20055991 PMCID: PMC2818656 DOI: 10.1186/1471-2334-10-4] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2009] [Accepted: 01/07/2010] [Indexed: 12/24/2022] Open
Abstract
BACKGROUND Toxoplasmosis is an important zoonotic parasitic disease worldwide. In immune competent individuals, Toxoplasma gondii preferentially infects tissues of central nervous systems, which might be an adding factor of certain psychiatric disorders. Congenital transmission of T. gondii during pregnancy has been regarded as a risk factor for the health of newborn infants. While in immune-compromised individuals, the parasite can cause life-threatening infections. This study aims to investigate the prevalence of T. gondii infection among clinically healthy individuals and patients with psychiatric disorders in China and to identify the potential risk factors related to the vulnerability of infection in the population. METHODS Serum samples from 2634 healthy individuals and 547 patients with certain psychiatric disorders in Changchun and Daqing in the northeast, and in Shanghai in the south of China were examined respectively for the levels of anti-T. gondii IgG by indirect ELISA and a direct agglutination assay. Prevalence of T. gondii infection in the Chinese population in respect of gender, age, residence and health status was systematically analyzed. RESULTS The overall anti-T. gondii IgG prevalence in the study population was 12.3%. In the clinically healthy population 12.5% was sero-positive and in the group with psychiatric disorders 11.3% of these patients were positive with anti-T. gondii IgG. A significant difference (P = 0.004) was found between male and female in the healthy population, the seroprevalence was 10.5% in men versus 14.3% in women. Furthermore, the difference of T. gondii infection rate between male and female in the 20-19 year's group was more obvious, with 6.4% in male population and 14.6% in female population. CONCLUSION A significant higher prevalence of T. gondii infection was observed in female in the clinically healthy population. No correlation was found between T. gondii infection and psychiatric disorders in this study. Results suggest that women are more exposed to T. gondii infection than men in China. The data argue for deeper investigations for the potential risk factors that threat the female populations.
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Affiliation(s)
- Yue Xiao
- Key Laboratory of Zoonosis, Ministry of Education, Jilin University, Xi An Da Lu 5333, Changchun 130062, PR China
| | - Jigang Yin
- Key Laboratory of Zoonosis, Ministry of Education, Jilin University, Xi An Da Lu 5333, Changchun 130062, PR China
| | - Ning Jiang
- Key Laboratory of Zoonosis, Ministry of Education, Jilin University, Xi An Da Lu 5333, Changchun 130062, PR China
| | - Mei Xiang
- The Second Hospital of Jilin University, Ziqiang Street 218, Changchun 10041, PR China
| | - Lili Hao
- Institute of Pathogen Biology, Chinese Academy of Medical Sciences, Beijing, Dong Dan San Tiao, Beijing 100730, PR China
| | - Huijun Lu
- Key Laboratory of Zoonosis, Ministry of Education, Jilin University, Xi An Da Lu 5333, Changchun 130062, PR China
| | - Hong Sang
- The Sixth Hospital of Changchun City, North Round Road 4596, Changchun 130040, PR China
| | - Xianying Liu
- The Second Hospital of Jilin University, Ziqiang Street 218, Changchun 10041, PR China
| | - Huiji Xu
- Changzheng Hospital, Shanghai, Fengyang Road 415, Shanghai 200003, PR China
| | - Johan Ankarklev
- Department of Parasitology, Mycology and Environmental Microbiology, Swedish Institute for Infectious Disease Control, Nobels väg 18, 171 82 Solna, Sweden
| | - Johan Lindh
- Department of Parasitology, Mycology and Environmental Microbiology, Swedish Institute for Infectious Disease Control, Nobels väg 18, 171 82 Solna, Sweden
| | - Qijun Chen
- Key Laboratory of Zoonosis, Ministry of Education, Jilin University, Xi An Da Lu 5333, Changchun 130062, PR China
- Institute of Pathogen Biology, Chinese Academy of Medical Sciences, Beijing, Dong Dan San Tiao, Beijing 100730, PR China
- Department of Parasitology, Mycology and Environmental Microbiology, Swedish Institute for Infectious Disease Control, Nobels väg 18, 171 82 Solna, Sweden
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Carranza PG, Lujan HD. New insights regarding the biology of Giardia lamblia. Microbes Infect 2010; 12:71-80. [DOI: 10.1016/j.micinf.2009.09.008] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2009] [Accepted: 09/15/2009] [Indexed: 10/20/2022]
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Carpenter ML, Cande WZ. Using morpholinos for gene knockdown in Giardia intestinalis. EUKARYOTIC CELL 2009; 8:916-9. [PMID: 19377039 PMCID: PMC2698301 DOI: 10.1128/ec.00041-09] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/02/2009] [Accepted: 04/02/2009] [Indexed: 11/20/2022]
Abstract
We used translation-blocking morpholinos to reduce protein levels in Giardia intestinalis. Twenty-four hours after electroporation with morpholinos targeting either green fluorescent protein or kinesin-2b, levels of these proteins were reduced by 60%. An epitope-tagged transgene can also be used as a reporter for morpholino efficacy with targets lacking specific antibodies.
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Affiliation(s)
- Meredith L Carpenter
- Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720, USA
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Biogenesis of Dense-Core Secretory Granules. TRAFFICKING INSIDE CELLS 2009. [PMCID: PMC7122546 DOI: 10.1007/978-0-387-93877-6_10] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Dense core granules (DCGs) are vesicular organelles derived from outbound traffic through the eukaryotic secretory pathway. As DCGs are formed, the secretory pathway can also give rise to other types of vesicles, such as those bound for endosomes, lysosomes, and the cell surface. DCGs differ from these other vesicular carriers in both content and function, storing highly concentrated cores’ of condensed cargo in vesicles that are stably maintained within the cell until a specific extracellular stimulus causes their fusion with the plasma membrane. These unique features are imparted by the activities of membrane and lumenal proteins that are specifically delivered to the vesicles during synthesis. This chapter will describe the DCG biogenesis pathway, beginning with the sorting of DCG proteins from proteins that are destined for other types of vesicle carriers. In the trans-Golgi network (TGN), sorting occurs as DCG proteins aggregate, causing physical separation from non-DCG proteins. Recent work addresses the nature of interactions that produce these aggregates, as well as potentially important interactions with membranes and membrane proteins. DCG proteins are released from the TGN in vesicles called immature secretory granules (ISGs). The mechanism of ISG formation is largely unclear but is not believed to rely on the assembly of vesicle coats like those observed in other secretory pathways. The required cytosolic factors are now beginning to be identified using in vitro systems with purified cellular components. ISG transformation into a mature fusion-competent, stimulus-dependent DCG occurs as endoproteolytic processing of many DCG proteins causes continued condensation of the lumenal contents. At the same time, proteins that fail to be incorporated into the condensing core are removed by a coat-mediated budding mechanism, which also serves to remove excess membrane and membrane proteins from the maturing vesicle. This chapter will summarize the work leading to our current view of granule synthesis, and will discuss questions that need to be addressed in order to gain a more complete understanding of the pathway.
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Prucca CG, Slavin I, Quiroga R, Elías EV, Rivero FD, Saura A, Carranza PG, Luján HD. Antigenic variation in Giardia lamblia is regulated by RNA interference. Nature 2008; 456:750-4. [DOI: 10.1038/nature07585] [Citation(s) in RCA: 175] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2008] [Accepted: 10/06/2008] [Indexed: 12/25/2022]
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Elias EV, Quiroga R, Gottig N, Nakanishi H, Nash TE, Neiman A, Lujan HD. Characterization of SNAREs determines the absence of a typical Golgi apparatus in the ancient eukaryote Giardia lamblia. J Biol Chem 2008; 283:35996-6010. [PMID: 18930915 DOI: 10.1074/jbc.m806545200] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Giardia is a eukaryotic protozoal parasite with unusual characteristics, such as the absence of a morphologically evident Golgi apparatus. Although both constitutive and regulated pathways for protein secretion are evident in Giardia, little is known about the mechanisms involved in vesicular docking and fusion. In higher eukaryotes, soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs) of the vesicle-associated membrane protein and syntaxin families play essential roles in these processes. In this work we identified and characterized genes for 17 SNAREs in Giardia to define the minimal set of subcellular organelles present during growth and encystation, in particular the presence or not of a Golgi apparatus. Expression and localization of all Giardia SNAREs demonstrate their presence in distinct subcellular compartments, which may represent the extent of the endomembrane system in eukaryotes. Remarkably, Giardia SNAREs, homologous to Golgi SNAREs from other organisms, do not allow the detection of a typical Golgi apparatus in either proliferating or differentiating trophozoites. However, some features of the Golgi, such as the packaging and sorting function, seem to be performed by the endoplasmic reticulum and/or the nuclear envelope. Moreover, depletion of individual genes demonstrated that several SNAREs are essential for viability, whereas others are dispensable. Thus, Giardia requires a smaller number of SNAREs compared with other eukaryotes to accomplish all of the vesicle trafficking events that are critical for the growth and differentiation of this important human pathogen.
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Affiliation(s)
- Eliana V Elias
- Laboratory of Biochemistry and Molecular Biology, School of Medicine, Catholic University of Cordoba/National Council for Science and Technology, Cordoba CP X5004ASK, Argentina
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17
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Encystation of Giardia lamblia: a model for other parasites. Curr Opin Microbiol 2007; 10:554-9. [PMID: 17981075 DOI: 10.1016/j.mib.2007.09.011] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2007] [Revised: 09/20/2007] [Accepted: 09/20/2007] [Indexed: 01/24/2023]
Abstract
To colonize the human small intestine, Giardia lamblia monitors a dynamic environment. Trophozoites attach to enterocytes that mature and die. The parasites must 'decide' whether to re-attach or differentiate into cysts that survive in the environment and re-activate when ingested. Other intestinal parasites face similar challenges. Study of these parasites is limited because they do not encyst in vitro. Giardia trophozoites were persuaded to encyst in vitro by mimicking physiological stimuli. Cysts are dormant, yet 'spring-loaded for action' to excyst upon ingestion. Giardial encystation has been studied from morphological, cell biological, biochemical, and molecular viewpoints. Yet important gaps remain and the mechanisms that co-ordinate responses to external signals remain enigmatic.
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18
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Gaechter V, Schraner E, Wild P, Hehl AB. The single dynamin family protein in the primitive protozoan Giardia lamblia is essential for stage conversion and endocytic transport. Traffic 2007; 9:57-71. [PMID: 17892527 DOI: 10.1111/j.1600-0854.2007.00657.x] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Dynamins are universally conserved large guanosine triphosphatases, which function as mechanoenzymes in membrane scission. The primitive protozoan Giardia lamblia has a single dynamin-related protein (GlDRP) with an unusual domain structure. Giardia lacks a Golgi apparatus but generates transient Golgi-like delay compartments dubbed encystation-specific vesicles (ESVs), which serve to accumulate and mature cyst wall proteins during differentiation to infectious cyst forms. Here, we analyze the function of GlDRP during growth and encystation and demonstrate that it relocalizes from peripheral endosomal-lysosomal compartments to nascent ESVs. We show that GlDRP is necessary for secretion of the cyst wall material and ESV homeostasis. Expression of a dominant-negative GlDRP variant does not interfere with ESV formation but blocks cyst formation completely prior to regulated exocytosis. GlDRP colocalizes with clathrin at the cell periphery and is necessary for endocytosis of surface proteins to endosomal-lysosomal organelles in trophozoites. Electron microscopy and live cell imaging reveal gross morphological changes as well as functional impairment of the endocytic system in cells expressing the dominant-negative GlDRP. Thus, giardial DRP plays a key role in two distinct trafficking pathways and in organelle homeostasis, both essential functions for the proliferation of the parasite in the gut and its transmission to a new host.
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Affiliation(s)
- Verena Gaechter
- Institute of Parasitology, University of Zürich, Winterthurerstrasse 266a, 8057 Zürich, Switzerland
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19
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Gottig N, Elías EV, Quiroga R, Nores MJ, Solari AJ, Touz MC, Luján HD. Active and passive mechanisms drive secretory granule biogenesis during differentiation of the intestinal parasite Giardia lamblia. J Biol Chem 2006; 281:18156-66. [PMID: 16611634 DOI: 10.1074/jbc.m602081200] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The parasitic protozoan Giardia lamblia undergoes important changes to survive outside the intestine of its host by differentiating into infective cysts. During encystation, three cyst wall proteins (CWPs) are specifically expressed and concentrated within encystation-specific secretory vesicles (ESVs). ESVs are electron-dense secretory granules that transport CWPs before exocytosis and extracellular polymerization into a rigid cyst wall. Because secretory granules form at the trans-Golgi in higher eukaryotes and because Giardia lacks an identifiable Golgi apparatus, the aim of this work was to investigate the molecular basis of secretory granule formation in Giardia by examining the role of CWPs in this process. Although CWP1, CWP2, and CWP3 are structurally similar in their 26-kDa leucine-rich overlapping region, CWP2 is distinguished by the presence of a 13-kDa C-terminal basic extension. In non-encysting trophozoites, expression of different CWP chimeras showed that the CWP2 basic extension is necessary for biogenesis of ESVs, which occurs in a compartment derived from the endoplasmic reticulum. Nevertheless, the CWP2 basic extension per se is insufficient to trigger ESV formation, indicating that other domains in CWPs are also required. We found that CWP2 is a key regulator of ESV formation by acting as an aggregation factor for CWP1 and CWP3 through interactions mediated by its conserved region. CWP2 also acts as a ligand for sorting via its C-terminal basic extension. These findings show that granule biogenesis requires complex interactions among granule components and membrane receptors.
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Affiliation(s)
- Natalia Gottig
- Instituto de Investigaciones Médicas Mercedes y Martín Ferreyra, Consejo Nacional de Investigaciones Científicas y Técnicas, Friuli 2434, CP 5000 Córdoba, Argentina
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20
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von Allmen N, Bienz M, Hemphill A, Müller N. Quantitative assessment of sense and antisense transcripts from genes involved in antigenic variation (vsp genes) and encystation (cwp 1 gene) of Giardia lamblia clone GS/M-83-H7. Parasitology 2005; 130:389-96. [PMID: 15830812 DOI: 10.1017/s0031182004006742] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Antigenic variation of the intestinal protozoan parasite Giardia lamblia is caused by an exchange of the parasite's variant surface protein (VSP) coat. Many investigations on antigenic variation were performed with G. lamblia clone GS/M-83-H7 which produces surface antigen VSP H7. To generate novel information on giardial vsp gene transcription, vsp RNA levels were assessed by quantitative reverse transcription-(RT)-PCR in both axenic VSP H7-type trophozoites and subvariants obtained after negative selection of GS/M-83-H7 trophozoites by treatment with a cytotoxic, VSP H7-specific monoclonal antibody. Our investigation was not restricted to the assessment of the sense vsp transcript levels but also included an approach aimed at the detection of complementary antisense vsp transcripts within the two trophozoite populations. We found that sense vsp H7 RNA predominated in VSP H7-type trophozoites while sense RNA from only one (vsp IVg) of 8 subvariant vsp genes totally analysed predominated in subvariant-type trophozoites. Interestingly, the two trophozoite populations exhibited a similar relative distribution regarding the vsp H7 and vsp IVg antisense RNA molecules. An analogous sense versus antisense RNA pattern was also observed when the transcripts of gene cwp 1 (encoding cyst wall protein 1) were investigated. Here, both types of RNA molecules only appeared after cwp 1 had been induced through in vitro encystation of the parasite. These findings for the first time demonstrated that giardial antisense RNA production did not occur in a constitutive manner but was directly linked to complementary sense RNA production after activation of the respective gene systems.
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Affiliation(s)
- N von Allmen
- Institute of Parasitology, University of Berne, Länggass-Strasse 122, CH-3012 Berne, Switzerland
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21
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Weiland MEL, McArthur AG, Morrison HG, Sogin ML, Svärd SG. Annexin-like alpha giardins: a new cytoskeletal gene family in Giardia lamblia. Int J Parasitol 2005; 35:617-26. [PMID: 15862575 DOI: 10.1016/j.ijpara.2004.12.009] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2004] [Revised: 12/10/2004] [Accepted: 12/14/2004] [Indexed: 10/25/2022]
Abstract
Through a genome survey and phylogenetic analysis, we have identified and sequenced 14 new coding regions for alpha-giardins in Giardia lamblia. These proteins are related to annexins and comprise a multi-gene family with 21 members. Many alpha giardins are highly expressed proteins that are very immunogenic during acute giardiasis in humans. However, little is known about the function of these proteins. By using PCR with different combinations of gene-specific primers, we demonstrated that several of the genes localised to the same chromosomal fragment. These data point towards a molecular evolution through gene duplication and subsequent functional divergence. Semi-quantitative reverse transcriptase-PCR analysis of the Giardia life cycle revealed large differences in mRNA expression levels of the alpha giardins. Epitope tagging of the alpha-giardins localised them to different cytoskeletal components, such as the flagella and the adhesive disc, but also to the plasma membrane. These localisation experiments suggest alpha-giardins play a role in cell motility, attachment and membrane stability.
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Affiliation(s)
- Malin E-L Weiland
- Microbiology and Tumor Biology Center, Karolinska Institutet, Stockholm, Sweden
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22
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Abstract
Early diverged extant organisms, which may serve as convenient laboratory models to look for and study evolutionary ancient features of eukaryotic cell biology, are rare. The diplomonad Giardia intestinalis, a protozoan parasite known to cause diarrhoeal disease, has become an increasingly popular object of basic research in cell biology, not least because of a genome sequencing project nearing completion. Commensurate with its phylogenetic status, the Giardia trophozoite has a very basic secretory system and even lacks hallmark structures such as a morphologically identifiable Golgi apparatus. The cell's capacity for protein sorting is nevertheless unimpeded, exemplified by its ability to cope with massive amounts of newly synthesized cyst wall proteins and glycans, which are sorted to dedicated Golgi-like compartments termed encystation-specific vesicles (ESVs) generated from endoplasmic reticulum (ER)-derived transport intermediates. This soluble bulk cargo is kept strictly separate from constitutively transported variant surface proteins during export, a function that is dependent on the stage-specific recognition of trafficking signals. Encysting Giardia therefore provide a unique system for the study of unconventional, Golgi-independent protein trafficking mechanisms in the broader context of eukaryotic endomembrane organization and evolution.
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Affiliation(s)
- Adrian B Hehl
- Institute of Parasitology, University of Zürich, Winterthurerstrasse 266a, CH-8057 Zürich, Switzerland.
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23
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de Souza W, Lanfredi-Rangel A, Campanati L. Contribution of microscopy to a better knowledge of the biology of Giardia lamblia. MICROSCOPY AND MICROANALYSIS : THE OFFICIAL JOURNAL OF MICROSCOPY SOCIETY OF AMERICA, MICROBEAM ANALYSIS SOCIETY, MICROSCOPICAL SOCIETY OF CANADA 2004; 10:513-527. [PMID: 15525427 DOI: 10.1017/s1431927604040954] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/27/2002] [Indexed: 05/24/2023]
Abstract
Giardia lamblia is a flagellated protozoan of great medical and biological importance. It is the causative agent of giardiasis, one of the most prevalent diarrheal disease both in developed and third-world countries. Morphological studies have shown that G. lamblia does not present structures such as peroxisomes, mitochondria, and a well-elaborated Golgi complex. In this review, special emphasis is given to the contribution made by various microscopic techniques to a better knowledge of the biology of the protozoan. The application of video microscopy, immunofluorescence confocal laser scanning microscopy, and several techniques associated with transmission electron microscopy (thin section, enzyme cytochemistry, freeze-fracture, deep-etching, fracture-flip) to the study of the cell surface, peripheral vesicles, endoplasmic reticulum-Golgi complex system, and of the encystation vesicles found in trophozoites and during the process of trophozoite-cyst transformation are discussed.
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Affiliation(s)
- Wanderley de Souza
- Laboratório de Ultraestrutura Celular, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, CCS-Bloco G, 21949-900, Rio de Janeiro-RJ, Brazil.
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24
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Dacks JB, Doolittle WF. Molecular and phylogenetic characterization of syntaxin genes from parasitic protozoa. Mol Biochem Parasitol 2004; 136:123-36. [PMID: 15478792 DOI: 10.1016/j.molbiopara.2004.02.014] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Vesicular transport is an integral process in eukaryotic cells and the syntaxins, a member of the SNARE protein superfamily, are a critical piece of the vesicular transport machinery. We have obtained syntaxin homologues from diverse protozoan parasites (including Entamoeba, Giardia, Trichomonas and Trypanosoma), determined the paralogue affinity of the homologues by molecular phylogenetics and compared functionally critical amino acid sites identified in other syntaxins. Surprisingly, three sequences deviate at the signature glutamine residue position, conserved in all previously identified syntaxin homologues. It is known that, despite conserved structure and function of both the syntaxins and the proteins of the regulatory SM superfamily, the various syntaxin paralogues bind their respective SM partners at different regions of the syntaxin molecule. These sites of interactions have been identified down to the individual residues. The pattern of conservation at these residues, in our evolutionarily diverse sampling of syntaxin paralogues, is therefore used to gain further insight into the interaction of these proteins. Phylogenetic analysis confirms and extends previous conclusions that the syntaxin families are present in diverse eukaryotes and that the syntaxin sub-families diverged early in eukaryotic evolution. This result is expanded with the inclusion of new homologues for previously sampled taxa, newly sampled taxa, and newly sampled syntaxin sub-families. Because of their integral role in membrane trafficking, the syntaxin genes represent a valuable potential molecular marker for the experimental study of the endomembrane system of disease-causing protists.
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Affiliation(s)
- Joel B Dacks
- Program in Evolutionary Biology, Department of Biochemistry and Molecular Biology, Dalhousie University, 5850 College Street, Halifax, NS, Canada B3H 1X5.
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Touz MC, Kulakova L, Nash TE. Adaptor protein complex 1 mediates the transport of lysosomal proteins from a Golgi-like organelle to peripheral vacuoles in the primitive eukaryote Giardia lamblia. Mol Biol Cell 2004; 15:3053-60. [PMID: 15107467 PMCID: PMC452563 DOI: 10.1091/mbc.e03-10-0744] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Giardia lamblia is an early branching protist that possesses peripheral vacuoles (PVs) with characteristics of lysosome-like organelles, located underneath the plasma membrane. In more evolved cells, lysosomal protein trafficking is achieved by cargo recognition involving adaptor protein (AP) complexes that recognize specific amino acid sequences (tyrosine and/or dileucine motifs) within the cytoplasmic tail of membrane proteins. Previously, we reported that Giardia has a tyrosine-based sorting system, which mediates the targeting of a membrane-associated cysteine protease (encystation-specific cysteine protease, ESCP) to the PVs. Here, we show that Giardia AP1 mediates the transport of ESCP and the soluble acid phosphatase (AcPh) to the PVs. By using the yeast two-hybrid assay we found that the ESCP tyrosine-based motif interacts specifically with the medium subunit of AP1 (Gimicroa). Hemagglutinin-tagged Gimicroa colocalizes with ESCP and AcPh and coimmunoprecipitates with clathrin, suggesting that protein trafficking toward the PVs is clathrin-adaptin dependent. Targeted disruption of Gimicroa results in mislocalization of ESCP and AcPh but not of variant-specific surface proteins. Our results suggest that, unlike mammalian cells, only AP1 is involved in anterograde protein trafficking to the PVs in Giardia. Moreover, even though Giardia trophozoites lack a morphologically discernible Golgi apparatus, the presence of a clathrin-adaptor system suggests that this parasite possess a primitive secretory organelle capable of sorting proteins similar to that of more evolved cells.
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Affiliation(s)
- María C Touz
- Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA.
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Abstract
PURPOSE OF REVIEW Giardia intestinalis (syn. duodenalis or lamblia) is one of the most common intestinal parasites in the world, with an estimated 2.8 x 10(6) infections per year in humans, and it contributes to diarrhea and nutritional deficiencies in children in developing regions. The wide prevalence of Giardia and its unique place in evolutionary biology have led to ongoing research. RECENT FINDINGS Research into the basic biology of Giardia has highlighted some of its unique properties as an 'early-branching' eukaryote. Although Giardia do not contain mitochondria, they have developed pathways to perform some mitochondrial functions. Investigations into encystation and excystation have identified new gene products that are important in cyst wall formation, and signal transduction events that occur during excystation. The ability to transfect Giardia stably will lead to an improved understanding of its development and metabolism. Molecular typing of G. intestinalis isolates indicates that most animal parasites are not associated with human infection. Insights into immunology have helped define the role of IL-6 in the early control of murine giardiasis, and the contributions of IgA in controlling infection. Further studies of giardiasis in poorly nourished children in developing regions supports an important contributing role of Giardia in stunting and cognitive impairment. Finally, new diagnostic assays using antigen detection are being evaluated and a new agent, nitazoxanide, has been approved in the USA for the treatment of giardiasis and cryptosporidiosis in children. SUMMARY Research into the biology of Giardia should increase knowledge about protist differentiation and will complement studies in other biological systems. Continued study of the role of Giardia in chronic diarrhea and malnutrition in developing regions will help focus strategies to improve childhood growth and nutrition.
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Affiliation(s)
- Syed A Ali
- Division of Infectious Diseases, University of Connecticut School of Medicine, Farmington, Connecticut, USA
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Abstract
Given that resistance to antiprotozoal drugs exists and is likely to increase and given that currently no reliable treatments exist for some of these infections, efforts to find new targets for chemotherapy must be continued. In the case of cyst-forming pathogenic protozoa, one such target might be encystment pathways and cyst-wall assembly. Information is increasing on protozoan encystment and, as it does, we can begin to answer the question of whether targeting it for chemotherapy is a viable drug strategy. Currently, there are significant efforts to understand encystment in Giardia and Entamoeba, and potential targets are being discovered as work on their encystment mechanisms progress. We know with certainty now that Giardia and Entamoeba cyst walls contain unique proteins and polysaccharides which differ from those of their hosts and thus make them potentially interesting targets for a variety of chemotherapeutic attacks. Although we lack detailed information about the other protozoan cyst formers, enough evidence exists for Giardia and Entamoeba that it seems prudent to screen them with some of the antifungal drugs, especially those that target mannoproteins, chitin synthesis, and beta (1, 3) glucan synthesis to ascertain if they target elements in these protozoan pathways that are similar to those found in fungi.
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Affiliation(s)
- Edward L Jarroll
- Department of Biology, Northeastern University, 106 Egan Bldg., 360 Huntington Avenue, Boston, MA 02115, USA.
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Abstract
The calcium ion (Ca(2+)) is used as a major signaling molecule in a diverse range of eukaryotic cells including several human parasitic protozoa, such as Trypanosoma cruzi, Trypanosoma brucei, Leishmania spp, Plasmodium spp, Toxoplasma gondii, Cryptosporidium parvum, Entamoeba histolytica, Giardia lamblia and Trichomonas vaginalis. Ca(2+) is critical for invasion of intracellular parasites, and its cytosolic concentration is regulated by the concerted operation of several transporters present in the plasma membrane, endoplasmic reticulum, mitochondria and acidocalcisomes. Recent findings have shed light on the function of these transporters, the roles that they play in cellular metabolism and their potential use for targeting them for new therapies.
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Affiliation(s)
- Silvia N J Moreno
- Laboratory of Molecular Parasitology, Department of Pathobiology and Center for Zoonoses Research, University of Illinois at Urbana-Champaign, Urbana, IL 61802, USA.
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Abstract
Giardia, a protozoan parasite of humans and other vertebrates, is a common cause of intestinal disease worldwide. Besides its medical importance, Giardia is considered an excellent system to study the evolution of fundamental cellular processes because it belongs to the earliest branches of the eukaryotic lineage of descent. Giardia trophozoites lack organelles typical of higher eukaryotes such mitochondria, peroxisomes and compartments involved in intracellular protein trafficking and secretion, such as the Golgi apparatus and secretory granules. Nevertheless, the minimal machinery for protein transport and sorting is present in this parasite. When Giardia undergoes encystation, the biogenesis of secretory organelles necessary to transport cyst wall constituents to the cell surface takes place. Recent studies in both vegetative and encysting trophozoites have provided interesting information regarding the secretory pathway of this important human pathogen.
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Affiliation(s)
- Hugo D Lujan
- Catedra de Bioquimica y Biologia Molecular, Facultad de Ciencias Medicas, Universidad Nacional de Cordoba, Pabellon Argentina 2do piso, Ciudad Universitaria, CP 5000, Cordoba, Argentina.
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Touz MC, Lujan HD, Hayes SF, Nash TE. Sorting of encystation-specific cysteine protease to lysosome-like peripheral vacuoles in Giardia lamblia requires a conserved tyrosine-based motif. J Biol Chem 2003; 278:6420-6. [PMID: 12466276 DOI: 10.1074/jbc.m208354200] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Encystation-specific cysteine protease (ESCP) was the first membrane-associated protein described to be part of the lysosome-like peripheral vacuoles in the intestinal parasite Giardia lamblia. ESCP is homologous to cathepsin C enzymes of higher eukaryotes, but is distinguished from other lysosomal cysteine proteases because it possesses a transmembrane domain and a short cytoplasmic tail. Tyrosine-based motifs within tails of membrane proteins are known to participate in endosomal/lysosomal protein sorting in higher eukaryotes. In this study, we show that a YRPI motif within the ESCP cytoplasmic tail is necessary and sufficient to mediate ESCP sorting to peripheral vacuoles in Giardia. Deletion and point mutation analysis demonstrated that the tyrosine residue is critical for ESCP sorting, whereas amino acids located at the Y+1 (Arg), Y+2 (Pro), and Y+3 (Ile) positions show minimal effect. Loss of the motif resulted in surface localization, whereas addition of the motif to a variant-specific surface protein resulted in lysosomal localization. Although Giardia trophozoites lack a morphologically discernible Golgi apparatus, our findings indicate that this parasite directs proteins to the lysosomes using a conserved sorting signal similar to that used by yeast and mammalian cells. Because Giardia is one of the earliest branching protist, these results demonstrate that sorting motifs for specific protein traffic developed very early during eukaryotic evolution.
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Affiliation(s)
- Maria C Touz
- Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA.
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