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Benchimol M, Gadelha AP, de Souza W. Unusual Cell Structures and Organelles in Giardia intestinalis and Trichomonas vaginalis Are Potential Drug Targets. Microorganisms 2022; 10:2176. [PMID: 36363768 PMCID: PMC9698047 DOI: 10.3390/microorganisms10112176] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2022] [Revised: 10/28/2022] [Accepted: 10/31/2022] [Indexed: 09/29/2023] Open
Abstract
This review presents the main cell organelles and structures of two important protist parasites, Giardia intestinalis, and Trichomonas vaginalis; many are unusual and are not found in other eukaryotic cells, thus could be good candidates for new drug targets aimed at improvement of the chemotherapy of diseases caused by these eukaryotic protists. For example, in Giardia, the ventral disc is a specific structure to this parasite and is fundamental for the adhesion and pathogenicity to the host. In Trichomonas, the hydrogenosome, a double membrane-bounded organelle that produces ATP, also can be a good target. Other structures include mitosomes, ribosomes, and proteasomes. Metronidazole is the most frequent compound used to kill many anaerobic organisms, including Giardia and Trichomonas. It enters the cell by passive diffusion and needs to find a highly reductive environment to be reduced to the nitro radicals to be active. However, it provokes several side effects, and some strains present metronidazole resistance. Therefore, to improve the quality of the chemotherapy against parasitic protozoa is important to invest in the development of highly specific compounds that interfere with key steps of essential metabolic pathways or in the functional macromolecular complexes which are most often associated with cell structures and organelles.
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Affiliation(s)
- Marlene Benchimol
- Laboratorio de Ultraestrutura Celular Hertha Meyer, Centro de Ciêcias da Saúde, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Cidade Universitaria, Rio de Janeiro 96200-000, Brazil
- Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro 21941-901, Brazil
- Instituto Nacional de Ciência e Tecnologia em Biologia Estrutural e Bioimagens e Centro Nacional de Biologia Estrutural e Bioimagens, Universidade Federal do Rio de Janeiro, Rio de Janeiro 21941-901, Brazil
| | - Ana Paula Gadelha
- Diretoria de Metrologia Aplicada as Ciências da Vida, Instituto Nacional de Metrologia, Qualidade e Tecnologia (INMETRO), Rio de Janeiro 25250-020, Brazil
| | - Wanderley de Souza
- Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro 21941-901, Brazil
- Instituto Nacional de Ciência e Tecnologia em Biologia Estrutural e Bioimagens e Centro Nacional de Biologia Estrutural e Bioimagens, Universidade Federal do Rio de Janeiro, Rio de Janeiro 21941-901, Brazil
- CMABio, Escola Superior de Saúde, Universidade do Estado do Amazonas-UEA, Manaus 69850-000, Brazil
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Benchimol M, de Souza W. Giardia intestinalis and its Endomembrane System. J Eukaryot Microbiol 2022; 69:e12893. [PMID: 35148450 DOI: 10.1111/jeu.12893] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2022] [Revised: 02/08/2022] [Accepted: 02/08/2022] [Indexed: 11/29/2022]
Abstract
Giardia intestinalis has unique characteristics, even in the absence of certain organelles. For instance, Golgi and mitochondria are not found. On the other hand, there is a network of peripheral vacuoles (PVs) and mitosomes. The endoplasmic reticulum (ER), nuclear membrane, peroxisomes, and lipid bodies are present. The peripheral vacuole system seems to play several simultaneous roles. It is involved in the endocytic activity of the trophozoite but also has characteristics of early and late endosomes and even lysosomes, establishing a connection with the ER. Some of the PVs contain small vesicles, acting as multivesicular bodies, including the release of exosomes. The mitosomes are surrounded by two membranes, divide during mitosis, and are distributed throughout the cell. They do not contain DNA, enzymes involved in the citric acid cycle, respiratory chain, or ATP synthesis. However, they contain the iron-sulfur complex and transporters as TOM and TIM. Some mitosomes are linked to flagellar axonemes through a fibrillar connection. During encystation, two types of larger cytoplasmic vesicles appear. One originating from the ER contains the cyst wall proteins. Another contains carbohydrates. Both migrate to the cell periphery and fuse with plasma membrane secreting their contents to give rise to the cell wall.
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Affiliation(s)
- Marlene Benchimol
- Universidade do Grande Rio (UNIGRANRIO), Rio de Janeiro Duque de Caxias, RJ, Brazil.,Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, Brazil.,Instituto Nacional de Ciência e Tecnologia em Biologia Estrutural e Bioimagens, Centro Nacional de Biologia Estrutural e Bioimagens, CENABIO-Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, Brazil
| | - Wanderley de Souza
- Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, Brazil.,Instituto Nacional de Ciência e Tecnologia em Biologia Estrutural e Bioimagens, Centro Nacional de Biologia Estrutural e Bioimagens, CENABIO-Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, Brazil
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Li X, Zhang N, Wu N, Li J, Yang J, Yu Y, Zheng J, Li X, Wang X, Gong P, Zhang X. Identification of GdRFC1 as a novel regulator of telomerase in Giardia duodenalis. Parasitol Res 2020; 119:1035-1041. [PMID: 32072328 DOI: 10.1007/s00436-020-06610-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2019] [Accepted: 01/15/2020] [Indexed: 11/25/2022]
Abstract
Telomerase plays a crucial role in ageing and tumourigenesis. However, the regulatory network of its activity is complicated and not fully understood. In the present study, a yeast two-hybrid screen identified a homologue of human replication factor C subunit 1 (RFC1) as a novel interacting protein of Giardia duodenalis GdTRBD (Giardia duodenalis telomerase ribonucleoprotein complex RNA binding domain GdTRBD). This interaction was further verified via GST pull-down in vitro and co-immunoprecipitation (Co-IP) and bimolecular fluorescence complementation (BiFC) in vivo. We also found that GdRFC1 (Giardia duodenalis replication factor C subunit 1) only interacted with GdTRBD in one nucleus in Giardia duodenalis via a proximity ligation assay (PLA). We reasoned that the two nuclei might have significant heterogeneity in their functional activities during the trophozoite stage and that the two molecules might be involved in other unidentified functions in addition to telomerase activity. In addition, knockdown of GdRFC1 decreased telomerase activity. Collectively, our results indicate that GdRFC1 is a novel binding partner and positive regulator of telomerase in Giardia duodenalis.
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Affiliation(s)
- Xianhe Li
- Key Laboratory of Zoonosis Research, Ministry of Education, College of Veterinary Medicine, Institute of Zoonosis, Jilin University, Changchun, 130062, China
| | - Nan Zhang
- Key Laboratory of Zoonosis Research, Ministry of Education, College of Veterinary Medicine, Institute of Zoonosis, Jilin University, Changchun, 130062, China
- The First Bethune Hospital, Jilin University, Changchun, 130021, China
| | - Na Wu
- Key Laboratory of Zoonosis Research, Ministry of Education, College of Veterinary Medicine, Institute of Zoonosis, Jilin University, Changchun, 130062, China
| | - Jianhua Li
- Key Laboratory of Zoonosis Research, Ministry of Education, College of Veterinary Medicine, Institute of Zoonosis, Jilin University, Changchun, 130062, China
| | - Ju Yang
- Key Laboratory of Zoonosis Research, Ministry of Education, College of Veterinary Medicine, Institute of Zoonosis, Jilin University, Changchun, 130062, China
| | - Yanhui Yu
- Key Laboratory of Zoonosis Research, Ministry of Education, College of Veterinary Medicine, Institute of Zoonosis, Jilin University, Changchun, 130062, China
| | - Jingtong Zheng
- Key Laboratory of Zoonosis Research, Ministry of Education, College of Veterinary Medicine, Institute of Zoonosis, Jilin University, Changchun, 130062, China
| | - Xin Li
- Key Laboratory of Zoonosis Research, Ministry of Education, College of Veterinary Medicine, Institute of Zoonosis, Jilin University, Changchun, 130062, China
| | - Xiaocen Wang
- Key Laboratory of Zoonosis Research, Ministry of Education, College of Veterinary Medicine, Institute of Zoonosis, Jilin University, Changchun, 130062, China
| | - Pengtao Gong
- Key Laboratory of Zoonosis Research, Ministry of Education, College of Veterinary Medicine, Institute of Zoonosis, Jilin University, Changchun, 130062, China.
| | - Xichen Zhang
- Key Laboratory of Zoonosis Research, Ministry of Education, College of Veterinary Medicine, Institute of Zoonosis, Jilin University, Changchun, 130062, China.
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Rópolo AS, Feliziani C, Touz MC. Unusual proteins in Giardia duodenalis and their role in survival. ADVANCES IN PARASITOLOGY 2019; 106:1-50. [PMID: 31630755 DOI: 10.1016/bs.apar.2019.07.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
The capacity of the parasite Giardia duodenalis to perform complex functions with minimal amounts of proteins and organelles has attracted increasing numbers of scientists worldwide, trying to explain how this parasite adapts to internal and external changes to survive. One explanation could be that G. duodenalis evolved from a structurally complex ancestor by reductive evolution, resulting in adaptation to its parasitic lifestyle. Reductive evolution involves the loss of genes, organelles, and functions that commonly occur in many parasites, by which the host renders some structures and functions redundant. However, there is increasing data that Giardia possesses proteins able to perform more than one function. During recent decades, the concept of moonlighting was described for multitasking proteins, which involves only proteins with an extra independent function(s). In this chapter, we provide an overview of unusual proteins in Giardia that present multifunctional properties depending on the location and/or parasite requirement. We also discuss experimental evidence that may allow some giardial proteins to be classified as moonlighting proteins by examining the properties of moonlighting proteins in general. Up to date, Giardia does not seem to require the numerous redundant proteins present in other organisms to accomplish its normal functions, and thus this parasite may be an appropriate model for understanding different aspects of moonlighting proteins, which may be helpful in the design of drug targets.
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Affiliation(s)
- Andrea S Rópolo
- Instituto de Investigación Médica Mercedes y Martín Ferreyra, INIMEC-CONICET-Universidad Nacional de Córdoba, Córdoba, Argentina
| | - Constanza Feliziani
- Instituto de Investigación Médica Mercedes y Martín Ferreyra, INIMEC-CONICET-Universidad Nacional de Córdoba, Córdoba, Argentina
| | - María C Touz
- Instituto de Investigación Médica Mercedes y Martín Ferreyra, INIMEC-CONICET-Universidad Nacional de Córdoba, Córdoba, Argentina.
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Feliziani C, Zamponi N, Gottig N, Rópolo AS, Lanfredi-Rangel A, Touz MC. The giardial ENTH protein participates in lysosomal protein trafficking and endocytosis. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2015; 1853:646-59. [PMID: 25576518 DOI: 10.1016/j.bbamcr.2014.12.034] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/05/2014] [Revised: 12/18/2014] [Accepted: 12/30/2014] [Indexed: 12/01/2022]
Abstract
In the protozoa parasite Giardia lamblia, endocytosis and lysosomal protein trafficking are vital parasite-specific processes that involve the action of the adaptor complexes AP-1 and AP-2 and clathrin. In this work, we have identified a single gene in Giardia encoding a protein containing an ENTH domain that defines monomeric adaptor proteins of the epsin family. This domain is present in the epsin or epsin-related (epsinR) adaptor proteins, which are implicated in endocytosis and Golgi-to-endosome protein trafficking, respectively, in other eukaryotic cells. We found that GlENTHp (for G. lamblia ENTH protein) localized in the cytosol, strongly interacted with PI3,4,5P3, was associated with the alpha subunit of AP-2, clathrin and ubiquitin and was involved in receptor-mediated endocytosis. It also bonded PI4P, the gamma subunit of AP-1 and was implicated in ER-to-PV trafficking. Alteration of the GlENTHp function severely affected trophozoite growth showing an unusual accumulation of dense material in the lysosome-like peripheral vacuoles (PVs), indicating that GlENTHp might be implicated in the maintenance of PV homeostasis. In this study, we showed evidence suggesting that GlENTHp might function as a monomeric adaptor protein supporting the findings of other group indicating that GlENTHp might be placed at the beginning of the ENTH family.
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Affiliation(s)
- Constanza Feliziani
- Instituto de Investigación Médica Mercedes y Martín Ferreyra, INIMEC, CONICET, Universidad Nacional de Córdoba, Friuli 2434, Córdoba, Argentina
| | - Nahuel Zamponi
- Instituto de Investigación Médica Mercedes y Martín Ferreyra, INIMEC, CONICET, Universidad Nacional de Córdoba, Friuli 2434, Córdoba, Argentina
| | - Natalia Gottig
- Molecular Biology Division, Facultad de Ciencias Bioquímicas y Farmacéuticas, Instituto de Biología Molecular y Celular de Rosario, CONICET, Universidad Nacional de Rosario, Rosario, Argentina
| | - Andrea S Rópolo
- Instituto de Investigación Médica Mercedes y Martín Ferreyra, INIMEC, CONICET, Universidad Nacional de Córdoba, Friuli 2434, Córdoba, Argentina
| | | | - Maria C Touz
- Instituto de Investigación Médica Mercedes y Martín Ferreyra, INIMEC, CONICET, Universidad Nacional de Córdoba, Friuli 2434, Córdoba, Argentina.
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Effects of therapeutic ultrasound on the nuclear envelope and nuclear pore complexes. J Appl Biomed 2013. [DOI: 10.2478/v10136-012-0042-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
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Neumann N, Lundin D, Poole AM. Comparative genomic evidence for a complete nuclear pore complex in the last eukaryotic common ancestor. PLoS One 2010; 5:e13241. [PMID: 20949036 PMCID: PMC2951903 DOI: 10.1371/journal.pone.0013241] [Citation(s) in RCA: 110] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2010] [Accepted: 09/15/2010] [Indexed: 11/26/2022] Open
Abstract
BACKGROUND The Nuclear Pore Complex (NPC) facilitates molecular trafficking between nucleus and cytoplasm and is an integral feature of the eukaryote cell. It exhibits eight-fold rotational symmetry and is comprised of approximately 30 nucleoporins (Nups) in different stoichiometries. Nups are broadly conserved between yeast, vertebrates and plants, but few have been identified among other major eukaryotic groups. METHODOLOGY/PRINCIPAL FINDINGS We screened for Nups across 60 eukaryote genomes and report that 19 Nups (spanning all major protein subcomplexes) are found in all eukaryote supergroups represented in our study (Opisthokonts, Amoebozoa, Viridiplantae, Chromalveolates and Excavates). Based on parsimony, between 23 and 26 of 31 Nups can be placed in LECA. Notably, they include central components of the anchoring system (Ndc1 and Gp210) indicating that the anchoring system did not evolve by convergence, as has previously been suggested. These results significantly extend earlier results and, importantly, unambiguously place a fully-fledged NPC in LECA. We also test the proposal that transmembrane Pom proteins in vertebrates and yeasts may account for their variant forms of mitosis (open mitoses in vertebrates, closed among yeasts). The distribution of homologues of vertebrate Pom121 and yeast Pom152 is not consistent with this suggestion, but the distribution of fungal Pom34 fits a scenario wherein it was integral to the evolution of closed mitosis in ascomycetes. We also report an updated screen for vesicle coating complexes, which share a common evolutionary origin with Nups, and can be traced back to LECA. Surprisingly, we find only three supergroup-level differences (one gain and two losses) between the constituents of COPI, COPII and Clathrin complexes. CONCLUSIONS/SIGNIFICANCE Our results indicate that all major protein subcomplexes in the Nuclear Pore Complex are traceable to the Last Eukaryotic Common Ancestor (LECA). In contrast to previous screens, we demonstrate that our conclusions hold regardless of the position of the root of the eukaryote tree.
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Affiliation(s)
- Nadja Neumann
- Department of Molecular Biology and Functional Genomics, Stockholm University, Stockholm, Sweden
| | - Daniel Lundin
- Department of Molecular Biology and Functional Genomics, Stockholm University, Stockholm, Sweden
| | - Anthony M. Poole
- Department of Molecular Biology and Functional Genomics, Stockholm University, Stockholm, Sweden
- School of Biological Sciences and Biomolecular Interaction Centre, University of Canterbury, Christchurch, New Zealand
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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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A contiguous compartment functions as endoplasmic reticulum and endosome/lysosome in Giardia lamblia. EUKARYOTIC CELL 2009; 8:1665-76. [PMID: 19749174 DOI: 10.1128/ec.00123-09] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The dynamic evolution of organelle compartmentalization in eukaryotes and how strictly compartmentalization is maintained are matters of ongoing debate. While the endoplasmic reticulum (ER) is classically envisioned as the site of protein cotranslational translocation, it has recently been proposed to have pluripotent functions. Using transfected reporter constructs, organelle-specific markers, and functional enzyme assays, we now show that in an early-diverging protozoan, Giardia lamblia, endocytosis and subsequent degradation of exogenous proteins occur in the ER or in an adjacent and communicating compartment. The Giardia endomembrane system is simple compared to those of typical eukaryotes. It lacks peroxisomes, a classical Golgi apparatus, and canonical lysosomes. Giardia orthologues of mammalian lysosomal proteases function within an ER-like tubulovesicular compartment, which itself can dynamically communicate with clathrin-containing vacuoles at the periphery of the cell to receive endocytosed proteins. These primitive characteristics support Giardia's proposed early branching and could serve as a model to study the compartmentalization of endocytic and lysosomal functions into organelles distinct from the ER. This system also may have functional similarity to the retrograde transport of toxins and major histocompatibility complex class I function in the ER of mammals.
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Saraiya AA, Wang CC. snoRNA, a novel precursor of microRNA in Giardia lamblia. PLoS Pathog 2008; 4:e1000224. [PMID: 19043559 PMCID: PMC2583053 DOI: 10.1371/journal.ppat.1000224] [Citation(s) in RCA: 190] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2008] [Accepted: 10/31/2008] [Indexed: 12/05/2022] Open
Abstract
An Argonaute homolog and a functional Dicer have been identified in the ancient eukaryote Giardia lamblia, which apparently lacks the ability to perform RNA interference (RNAi). The Giardia Argonaute plays an essential role in growth and is capable of binding specifically to the m7G-cap, suggesting a potential involvement in microRNA (miRNA)-mediated translational repression. To test such a possibility, small RNAs were isolated from Giardia trophozoites, cloned, and sequenced. A 26-nucleotide (nt) small RNA (miR2) was identified as a product of Dicer-processed snoRNA GlsR17 and localized to the cytoplasm by fluorescence in situ hybridization, whereas GlsR17 was found primarily in the nucleolus of only one of the two nuclei in Giardia. Three other small RNAs were also identified as products of snoRNAs, suggesting that the latter could be novel precursors of miRNAs in Giardia. Putative miR2 target sites were identified at the 3′-untranslated regions (UTR) of 22 variant surface protein mRNAs using the miRanda program. In vivo expression of Renilla luciferase mRNA containing six identical miR2 target sites in the 3′-UTR was reduced by 40% when co-transfected with synthetic miR2, while the level of luciferase mRNA remained unaffected. Thus, miR2 likely affects translation but not mRNA stability. This repression, however, was not observed when Argonaute was knocked down in Giardia using a ribozyme-antisense RNA. Instead, an enhancement of luciferase expression was observed, suggesting a loss of endogenous miR2-mediated repression when this protein is depleted. Additionally, the level of miR2 was significantly reduced when Dicer was knocked down. In all, the evidence indicates the presence of a snoRNA-derived miRNA-mediated translational repression in Giardia. Gene regulation in Giardia lamblia, a primitive parasitic protozoan responsible for the diarrheal disease giardiasis, is poorly understood. There is no consensus promoter sequence. A simple eight–base pair AT-rich region is sufficient to initiate gene transcription in this organism. Thus, the main control of gene expression may occur after the stage of transcription. The presence of Dicer and Argonaute homologs in Giardia suggested that microRNA (miRNA)-mediated translational repression could be one mechanism of gene regulation. In this work, we characterized the presence of the miRNA pathway in Giardia as well as identified the novel use of small nucleolar RNA (snoRNA) as miRNA precursors. Potential target sites for one small RNA (miR2) were identified with the miRanda program. In vivo reporter assays confirmed the specific interaction between the target sites and miR2. A ribozyme-mediated reduction of Dicer and Argonaute in Giardia showed that the former is required for miR2 production whereas the latter functions in mediating the inhibition of reporter expression, which agrees with the roles of these two proteins. This is the first evidence of miRNA-mediated gene regulation in Giardia and the first demonstration of the use of snoRNAs as miRNA precursors.
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Affiliation(s)
- Ashesh A. Saraiya
- Department of Pharmaceutical Chemistry, University of California San Francisco, San Francisco, California, United States of America
| | - Ching C. Wang
- Department of Pharmaceutical Chemistry, University of California San Francisco, San Francisco, California, United States of America
- * E-mail:
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Teodorovic S, Braverman JM, Elmendorf HG. Unusually low levels of genetic variation among Giardia lamblia isolates. EUKARYOTIC CELL 2007; 6:1421-30. [PMID: 17557879 PMCID: PMC1951139 DOI: 10.1128/ec.00138-07] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/23/2007] [Accepted: 05/29/2007] [Indexed: 11/20/2022]
Abstract
Giardia lamblia, an intestinal pathogen of mammals, including humans, is a significant cause of diarrheal disease around the world. Additionally, the parasite is found on a lineage which separated early from the main branch in eukaryotic evolution. The extent of genetic diversity among G. lamblia isolates is insufficiently understood, but this knowledge is a prerequisite to better understand the role of parasite variation in disease etiology and to examine the evolution of mechanisms of genetic exchange among eukaryotes. Intraisolate genetic variation in G. lamblia has never been estimated, and previous studies on interisolate genetic variation have included a limited sample of loci. Here we report a population genetics study of intra- and interisolate genetic diversity based on six coding and four noncoding regions from nine G. lamblia isolates. Our results indicate exceedingly low levels of genetic variation in two out of three G. lamblia groups that infect humans; this variation is sufficient to allow identification of isolate-specific markers. Low genetic diversity at both coding and noncoding regions, with an overall bias towards synonymous substitutions, was discovered. Surprisingly, we found a dichotomous haplotype structure in the third, more variable G. lamblia group, represented by a haplotype shared with one of the homogenous groups and an additional group-specific haplotype. We propose that the distinct patterns of genetic-variation distribution among lineages are a consequence of the presence of genetic exchange. More broadly, our findings have implications for the regulation of gene expression, as well as the mode of reproduction in the parasite.
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Affiliation(s)
- Smilja Teodorovic
- Biology Department, 406 Reiss Bldg., 37th and O Sts. NW, Georgetown University, Washington, DC 20057, USA
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