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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: 30] [Impact Index Per Article: 6.0] [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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Datta SP, Jana K, Mondal A, Ganguly S, Sarkar S. Multiple paralogues of α-SNAP in Giardia lamblia exhibit independent subcellular localization and redistribution during encystation and stress. Parasit Vectors 2018; 11:539. [PMID: 30286802 PMCID: PMC6172762 DOI: 10.1186/s13071-018-3112-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2018] [Accepted: 09/13/2018] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The differently-diverged parasitic protist Giardia lamblia is known to have minimal machinery for vesicular transport. Yet, it has three paralogues of SNAP, a crucial component that together with NSF brings about disassembly of the cis-SNARE complex formed following vesicle fusion to target membranes. Given that most opisthokont hosts of this gut parasite express only one α-SNAP, this study was undertaken to determine whether these giardial SNAP proteins have undergone functional divergence. RESULTS All three SNAP paralogues are expressed in trophozoites, encysting trophozoites and cysts. Even though one of them clusters with γ-SNAP sequences in a phylogenetic tree, functional complementation analysis in yeast indicates that all the three proteins are functionally orthologous to α-SNAP. Localization studies showed a mostly non-overlapping distribution of these α-SNAPs in trophozoites, encysting cells and cysts. In addition, two of the paralogues exhibit substantial subcellular redistribution during encystation, which was also seen following exposure to oxidative stress. However, the expression of the three genes remained unchanged during this redistribution process. There is also a difference in the affinity of each of these α-SNAP paralogues for GlNSF. CONCLUSIONS None of the genes encoding the three α-SNAPs are pseudogenes and the encoded proteins are likely to discharge non-redundant functions in the different morphological states of G. lamblia. Based on the difference in the interaction of individual α-SNAPs with GlNSF and their non-overlapping pattern of subcellular redistribution during encystation and under stress conditions, it may be concluded that the three giardial α-SNAP paralogues have undergone functional divergence. Presence of one of the giardial α-SNAPs at the PDRs of flagella, where neither GlNSF nor any of the SNAREs localize, indicates that this α-SNAP discharges a SNARE-independent role in this gut pathogen.
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Affiliation(s)
- Shankari Prasad Datta
- Department of Biochemistry, Bose Institute, P 1/12 CIT Road Scheme VII M, Kolkata, West Bengal, 700054, India
| | - Kuladip Jana
- Division of Molecular Medicine, Bose Institute, P 1/12 CIT Road Scheme VII M, Kolkata, West Bengal, 700054, India
| | - Avisek Mondal
- Department of Biochemistry, Bose Institute, P 1/12 CIT Road Scheme VII M, Kolkata, West Bengal, 700054, India.,Present Address: Section on Developmental Genetics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, NIH, Bethesda, Maryland, USA
| | - Sandipan Ganguly
- Division of Parasitology, National Institute of Cholera and Enteric Diseases, P-33, CIT Road, Scheme XM, Beliaghata, Kolkata, West Bengal, 700010, India
| | - Srimonti Sarkar
- Department of Biochemistry, Bose Institute, P 1/12 CIT Road Scheme VII M, Kolkata, West Bengal, 700054, India.
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Touz MC, Zamponi N. Sorting without a Golgi complex. Traffic 2017; 18:637-645. [DOI: 10.1111/tra.12500] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2017] [Revised: 07/01/2017] [Accepted: 07/06/2017] [Indexed: 12/22/2022]
Affiliation(s)
- Maria C. Touz
- Instituto de Investigación Médica Mercedes y Martín Ferreyra, INIMEC - CONICET; Universidad Nacional de Córdoba; Córdoba Argentina
| | - Nahuel Zamponi
- Instituto de Investigación Médica Mercedes y Martín Ferreyra, INIMEC - CONICET; Universidad Nacional de Córdoba; Córdoba Argentina
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Shanmugam SK, Kumar K, Singh PK, Rastogi R, Mukhopadhyay A. Single GDP-dissociation Inhibitor Protein regulates endocytic and secretory pathways in Leishmania. Sci Rep 2016; 6:37058. [PMID: 27841328 PMCID: PMC5107955 DOI: 10.1038/srep37058] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2016] [Accepted: 10/07/2016] [Indexed: 11/09/2022] Open
Abstract
The role of GDP dissociation inhibitor (GDI) protein in regulation of Rab cycle in Leishmania is not known. Here, we have cloned and characterized the functions of GDI homologue in vivo in Leishmania. Our results have shown that LdGDI:WT along with GDP removes the Rab5 from purified endosomes and inhibits the homotypic fusion between early endosomes. Whereas, LdGDI:R239A, a dominant negative mutant of GDI, under the same condition neither removes the Rab5 from endosome nor inhibits fusion. To determine the role of Ld-GDI in vivo, transgenic parasites overexpressing GFP-LdGDI:WT or GFP-LdGDI:R239A, are co-expressed with RFP-LdRab5:WT, RFP-LdRab7:WT or RFP-LdRab1:WT. Our results have shown that overexpression of GFP-LdGDI:WT extracts the RFP-LdRab5, RFP-LdRab7 or RFP-LdRab1 from their discrete endomembrane predominantly into cytosol. No change in the distribution of indicated Rabs is detected with overexpression of GFP-LdGDI:R239A. To determine the functional significance, we have used hemoglobin as an endocytic marker and gp63 as a marker for secretory pathway. We have found that overexpression of GFP-LdGDI:WT enhances the lysosomal targeting of internalized hemoglobin and the secretion of gp63 in the parasites possibly by triggering Rab cycle. This is the first demonstration of a single GDI ubiquitously regulating both endocytic and secretory pathways in Leishmania.
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Affiliation(s)
| | - Kamal Kumar
- National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi 110067, India
| | - Pawan Kishor Singh
- National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi 110067, India
| | - Ruchir Rastogi
- National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi 110067, India
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Bahl S, Parashar S, Malhotra H, Raje M, Mukhopadhyay A. Functional Characterization of Monomeric GTPase Rab1 in the Secretory Pathway of Leishmania. J Biol Chem 2015; 290:29993-30005. [PMID: 26499792 DOI: 10.1074/jbc.m115.670018] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2015] [Indexed: 12/20/2022] Open
Abstract
Leishmania secretes a large number of its effectors to the extracellular milieu. However, regulation of the secretory pathway in Leishmania is not well characterized. Here, we report the cloning, expression, and characterization of the Rab1 homologue from Leishmania. We have found that LdRab1 localizes in Golgi in Leishmania. To understand the role of LdRab1 in the secretory pathway of Leishmania, we have generated transgenic parasites overexpressing GFP-LdRab1:WT, GFP-LdRab1:Q67L (a GTPase-deficient dominant positive mutant of Rab1), and GFP-LdRab1:S22N (a GDP-locked dominant negative mutant of Rab1). Surprisingly, our results have shown that overexpression of GFP-LdRab1:Q67L or GFP-LdRab1:S22N does not disrupt the trafficking and localization of hemoglobin receptor in Leishmania. To determine whether the Rab1-dependent secretory pathway is conserved in parasites, we have analyzed the role of LdRab1 in the secretion of secretory acid phosphatase and Ldgp63 in Leishmania. Our results have shown that overexpression of GFP-LdRab1:Q67L or GFP-LdRab1:S22N significantly inhibits the secretion of secretory acid phosphatase by Leishmania. We have also found that overexpression of GFP-LdRab1:Q67L or GFP-LdRab1:S22N retains RFP-Ldgp63 in Golgi and blocks the secretion of Ldgp63, whereas the trafficking of RFP-Ldgp63 in GFP-LdRab1:WT-expressing cells is unaltered in comparison with control cells. Taken together, our results have shown that the Rab1-regulated secretory pathway is well conserved, and hemoglobin receptor trafficking follows an Rab1-independent secretory pathway in Leishmania.
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Affiliation(s)
- Surbhi Bahl
- From the National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi 110067, India and
| | - Smriti Parashar
- From the National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi 110067, India and
| | | | - Manoj Raje
- the Institute of Microbial Technology, Chandigarh 160036, India
| | - Amitabha Mukhopadhyay
- From the National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi 110067, India and
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The generation gap: Proteome changes and strain variation during encystation in Giardia duodenalis. Mol Biochem Parasitol 2015; 201:47-56. [DOI: 10.1016/j.molbiopara.2015.05.007] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2015] [Revised: 05/26/2015] [Accepted: 05/28/2015] [Indexed: 12/26/2022]
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Baum DA, Baum B. An inside-out origin for the eukaryotic cell. BMC Biol 2014; 12:76. [PMID: 25350791 PMCID: PMC4210606 DOI: 10.1186/s12915-014-0076-2] [Citation(s) in RCA: 95] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2014] [Accepted: 09/17/2014] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Although the origin of the eukaryotic cell has long been recognized as the single most profound change in cellular organization during the evolution of life on earth, this transition remains poorly understood. Models have always assumed that the nucleus and endomembrane system evolved within the cytoplasm of a prokaryotic cell. RESULTS Drawing on diverse aspects of cell biology and phylogenetic data, we invert the traditional interpretation of eukaryotic cell evolution. We propose that an ancestral prokaryotic cell, homologous to the modern-day nucleus, extruded membrane-bound blebs beyond its cell wall. These blebs functioned to facilitate material exchange with ectosymbiotic proto-mitochondria. The cytoplasm was then formed through the expansion of blebs around proto-mitochondria, with continuous spaces between the blebs giving rise to the endoplasmic reticulum, which later evolved into the eukaryotic secretory system. Further bleb-fusion steps yielded a continuous plasma membrane, which served to isolate the endoplasmic reticulum from the environment. CONCLUSIONS The inside-out theory is consistent with diverse kinds of data and provides an alternative framework by which to explore and understand the dynamic organization of modern eukaryotic cells. It also helps to explain a number of previously enigmatic features of cell biology, including the autonomy of nuclei in syncytia and the subcellular localization of protein N-glycosylation, and makes many predictions, including a novel mechanism of interphase nuclear pore insertion.
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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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Castillo-Romero A, Leon-Avila G, Wang CC, Perez Rangel A, Camacho Nuez M, Garcia Tovar C, Ayala-Sumuano JT, Luna-Arias JP, Hernandez JM. Rab11 and actin cytoskeleton participate in Giardia lamblia encystation, guiding the specific vesicles to the cyst wall. PLoS Negl Trop Dis 2010; 4:e697. [PMID: 20532229 PMCID: PMC2879372 DOI: 10.1371/journal.pntd.0000697] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2009] [Accepted: 04/06/2010] [Indexed: 12/30/2022] Open
Abstract
Background Giardia passes through two stages during its life cycle, the trophozoite and the cyst. Cyst formation involves the synthesis of cyst wall proteins (CWPs) and the transport of CWPs into encystation-specific vesicles (ESVs). Active vesicular trafficking is essential for encystation, but the molecular machinery driving vesicular trafficking remains unknown. The Rab proteins are involved in the targeting of vesicles to several intracellular compartments through their association with cytoskeletal motor proteins. Methodology and Principal Findings In this study, we found a relationship between Rab11 and the actin cytoskeleton in CWP1 transport. Confocal microscopy showed Rab11 was distributed throughout the entire trophozoite, while in cysts it was translocated to the periphery of the cell, where it colocalized with ESVs and microfilaments. Encystation was also accompanied by changes in rab11 mRNA expression. To evaluate the role of microfilaments in encystation, the cells were treated with latrunculin A. Scanning electron microscopy showed this treatment resulted in morphological damages to encysted parasites. The intensity of fluorescence-labeled Rab11 and CWP1 in ESVs and cyst walls was reduced, and rab11 and cwp1 mRNA levels were down-regulated. Furthermore, knocking down Rab11 with a hammerhead ribozyme resulted in an up to 80% down-regulation of rab11 mRNA. Although this knockdown did not appear lethal for trophozoites and did not affect cwp1 expression during the encystation, confocal images showed CWP1 was redistributed throughout the cytosol. Conclusions and Significance Our results indicate that Rab11 participates in the early and late encystation stages by regulating CWP1 localization and the actin-mediated transport of ESVs towards the periphery. In addition, alterations in the dynamics of actin affected rab11 and cwp1 expression. Our results provide new information about the molecules involved in Giardia encystation and suggest that Rab11 and actin may be useful as novel pharmacological targets. The encystation process is crucial for survival and transmission of Giardia lamblia to new hosts. During this process, vesicular trafficking and the cytoskeleton play important roles. In eukaryotic cells, intracellular transport is regulated by proteins, including Rab-GTPases and SNAREs, which regulate vesicle formation along with recognition of and binding to the target membrane. Cytoskeletal structures are also involved in these processes. In this study, we demonstrate the participation of Rab11 in the transport of encystation-specific vesicles (ESVs). Additionally, we demonstrate that disruption of actin microfilaments affects ESVs transport. The modification of actin dynamics was also correlated with a reduction in rab11 and cwp1 expression. Furthermore, down-regulation of rab11 mRNA by a specific hammerhead ribozyme caused nonspecific localization of CWP1. We thus provide new information about the molecular machinery that regulates Giardia lamblia encystation. Given our findings, Rab11 and actin may be useful targets to block Giardia encystation.
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Affiliation(s)
- Araceli Castillo-Romero
- Departamento de Biología Celular, Centro de Investigación y de Estudios Avanzados del IPN, México DF, México
| | - Gloria Leon-Avila
- Departamento de Zoología, Escuela Nacional de Ciencias Biológicas del Instituto Politécnico Nacional, México DF, México
| | - Ching C. Wang
- Chemistry and Chemical Biology Graduate Program, Department of Pharmaceutical Chemistry, University of California San Francisco, San Francisco, California, United States of America
| | - Armando Perez Rangel
- Departamento de Biología Celular, Centro de Investigación y de Estudios Avanzados del IPN, México DF, México
| | - Minerva Camacho Nuez
- Departamento de Ciencias Genómicas, Universidad Autónoma de la Ciudad de México, México DF, México
| | - Carlos Garcia Tovar
- Departamento de Ciencias Biológicas, FES-Cuautitlán Universidad Nacional Autónoma de México, México, México
| | | | - Juan Pedro Luna-Arias
- Departamento de Biología Celular, Centro de Investigación y de Estudios Avanzados del IPN, México DF, México
| | - Jose Manuel Hernandez
- Departamento de Biología Celular, Centro de Investigación y de Estudios Avanzados del IPN, México DF, México
- * E-mail:
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Elias M, Patron NJ, Keeling PJ. The RAB family GTPase Rab1A from Plasmodium falciparum defines a unique paralog shared by chromalveolates and rhizaria. J Eukaryot Microbiol 2009; 56:348-56. [PMID: 19602080 DOI: 10.1111/j.1550-7408.2009.00408.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
The RAB GTPases, which are involved in regulation of endomembrane trafficking, exhibit a complex but incompletely understood evolutionary history. We elucidated the evolution of the RAB1 subfamily ancestrally implicated in the endoplasmic reticulum-to-Golgi traffic. We found that RAB1 paralogs have been generated over the course of eukaryotic evolution, with some duplications coinciding with the advent of major eukaryotic lineages (e.g. Metazoa, haptophytes). We also identified a unique, derived RAB1 paralog, orthologous to the Plasmodium Rab1A, that occurs in stramenopiles, alveolates, and Rhizaria, represented by the chlorarachniophyte Gymnochlora stellata. This finding is consistent with the recently documented existence of a major eukaryotic clade ("SAR") comprising these three lineages. We further found a Rab1A-like protein in the cryptophyte Guillardia theta, but it exhibits unusual features among RAB proteins: absence of a C-terminal prenylation motif and an N-terminal extension with two MSP domains; and its phylogenetic relationships could not be established convincingly due to its divergent nature. Our results nevertheless point to a unique membrane trafficking pathway shared by at least some lineages of chromalveolates and Rhizaria, an insight that has implications towards interpreting the early evolution of eukaryotes and the endomembrane system.
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Affiliation(s)
- Marek Elias
- Department of Botany, Faculty of Science, Charles University in Prague, Prague, Czech Republic.
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Phylogeny of endocytic components yields insight into the process of nonendosymbiotic organelle evolution. Proc Natl Acad Sci U S A 2008; 105:588-93. [PMID: 18182495 DOI: 10.1073/pnas.0707318105] [Citation(s) in RCA: 106] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
The process by which some eukaryotic organelles, for example the endomembrane system, evolved without endosymbiotic input remains poorly understood. This problem largely arises because many major cellular systems predate the last common eukaryotic ancestor (LCEA) and thus do not provide examples of organellogenesis in progress. A model is emerging whereby gene duplication and divergence of multiple "specificity-" or "identity-" encoding proteins for the various endomembranous organelles produced the diversity of nonendosymbiotically derived cellular compartments present in modern eukaryotes. To address this possibility, we analyzed three molecular components of the endocytic membrane-trafficking machinery. Phylogenetic analyses of the endocytic syntaxins, Rab 5, and the beta-adaptins each reveal a pattern of ancestral, undifferentiated endocytic homologues in the LCEA. Subsequently, these undifferentiated progenitors independently duplicated in widely divergent lineages, convergently producing components with similar endocytic roles, e.g., beta1 and beta2-adaptin. In contrast, beta3, beta4, and all other adaptin complex subunits, as well as paralogues of the syntaxins and Rabs specific for the other membrane-trafficking organelles, all evolved before the LCEA. Thus, the process giving rise to the differentiated organelles of the endocytic system appears to have been interrupted by the major speciation event that produced the extant eukaryotic lineages. These results suggest that although many endocytic components evolved before the LCEA, other major features evolved independently and convergently after diversification into the primary eukaryotic supergroups. This finding provides an example of a basic cellular system that was simpler in the LCEA than in many extant eukaryotes and yields insight into nonendosymbiotic organelle evolution.
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Davids BJ, Williams S, Lauwaet T, Palanca T, Gillin FD. Giardia lamblia aurora kinase: a regulator of mitosis in a binucleate parasite. Int J Parasitol 2007; 38:353-69. [PMID: 17964578 DOI: 10.1016/j.ijpara.2007.08.012] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2007] [Revised: 08/21/2007] [Accepted: 08/23/2007] [Indexed: 12/18/2022]
Abstract
Giardia lamblia is a major cause of diarrhoeal disease worldwide. Since it has no known toxin, the ability of trophozoites to colonise the human small intestine is required for its pathogenesis. Mitosis in this protozoan parasite is a unique challenge because its two equivalent nuclei and complex cytoskeleton must be duplicated and segregated accurately. Giardial mitosis is a complex and rapid event that is poorly understood at the cellular and molecular levels. Higher eukaryotes have one to three members of the highly conserved Ser/Thr aurora kinase (AK) family that regulate key aspects of mitosis and cytokinesis. Giardia has a single AK orthologue (gAK) with 61% similarity to human AK A. In addition to the conserved active site residues, activation loop and destruction-box motifs characteristic of AKs, gAK contains a unique insert near the active site region. We epitope-tagged gAK at its C-terminus and expressed it under its own promoter. During interphase, gAK localises exclusively to the nuclei, but is not phosphorylated as shown by lack of staining with an antibody specific to phosphorylated AK A (pAK). In contrast, during mitosis pAK localises to the basal bodies/centrosomes and co-localises with tubulin to the spindle. During specific stages of mitosis, giardial pAK also localised dynamically to cytoskeletal structures unique to Giardia: the paraflagellar dense rods of the anterior flagella and the median body, whose functions are unknown, as well as to the parent attachment disc. Two AK inhibitors significantly decreased giardial growth and increased the numbers of cells arrested in cytokinesis. These inhibitors appeared to increase microtubule nucleation and cell-ploidy. Our data show that gAK is phosphorylated in mitosis and suggest that it plays an important role in the Giardia cell cycle. The pleiotropic localisation of AK suggests that it may co-ordinate the reorganisation and segregation of tubulin-containing structures in mitosis. We believe this is the first report of a signalling protein regulating cell division in Giardia.
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Affiliation(s)
- Barbara J Davids
- Department of Pathology, Division of Infectious Diseases, University of California at San Diego, 214 Dickinson Street, San Diego, CA 92103-8416, USA.
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Dacks JB, Field MC. Evolution of the eukaryotic membrane-trafficking system: origin, tempo and mode. J Cell Sci 2007; 120:2977-85. [PMID: 17715154 DOI: 10.1242/jcs.013250] [Citation(s) in RCA: 194] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
The emergence of an endomembrane system was a crucial stage in the prokaryote-to-eukaryote evolutionary transition. Recent genomic and molecular evolutionary analyses have provided insight into how this critical system arrived at its modern configuration. The apparent relative absence of prokaryotic antecedents for the endomembrane machinery contrasts with the situation for mitochondria, plastids and the nucleus. Overall, the evidence suggests an autogenous origin for the eukaryotic membrane-trafficking machinery. The emerging picture is that early eukaryotic ancestors had a complex endomembrane system, which implies that this cellular system evolved relatively rapidly after the proto-eukaryote diverged away from the other prokaryotic lines. Many of the components of the trafficking system are the result of gene duplications that have produced proteins that have similar functions but differ in their subcellular location. A proto-eukaryote possessing a very simple trafficking system could thus have evolved to near modern complexity in the last common eukaryotic ancestor (LCEA) via paralogous gene family expansion of the proteins encoding organelle identity. The descendents of this common ancestor have undergone further modification of the trafficking machinery; unicellular simplicity and multicellular complexity are the prevailing trend, but there are some remarkable counter-examples.
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Affiliation(s)
- Joel B Dacks
- Department of Pathology, University of Cambridge, Tennis Court Road, Cambridge, CB2 1QP, UK.
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Lauwaet T, Davids BJ, Torres‐Escobar A, Birkeland SR, Cipriano MJ, Preheim SP, Palm D, Svärd SG, McArthur AG, Gillin FD. Protein phosphatase 2A plays a crucial role in Giardia lamblia differentiation. Mol Biochem Parasitol 2007; 152:80-9. [PMID: 17204341 PMCID: PMC1964530 DOI: 10.1016/j.molbiopara.2006.12.001] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2006] [Revised: 12/05/2006] [Accepted: 12/06/2006] [Indexed: 01/24/2023]
Abstract
The ability of Giardia lamblia to undergo two distinct differentiations in response to physiologic stimuli is central to its pathogenesis. The giardial cytoskeleton changes drastically during encystation and excystation. However, the signal transduction pathways mediating these transformations are poorly understood. We tested the hypothesis that PP2A, a highly conserved serine/threonine protein phosphatase, might be important in giardial differentiation. We found that in vegetatively growing trophozoites, gPP2A-C protein localizes to basal bodies/centrosomes, and to cytoskeletal structures unique to Giardia: the ventral disk, and the dense rods of the anterior, posterior-lateral, and caudal flagella. During encystation, gPP2A-C protein disappears from only the anterior flagellar dense rods. During excystation, gPP2A-C localizes to the cyst wall in excysting cysts but is not found in the wall of cysts with emerging excyzoites. Transcriptome and immunoblot analyses indicated that gPP2A-C mRNA and protein are upregulated in mature cysts and during the early stage of excystation that models passage through the host stomach. Stable expression of gPP2A-C antisense RNA did not affect vegetative growth, but strongly inhibited the formation of encystation secretory vesicles (ESV) and water-resistant cysts. Moreover, the few cysts that formed were highly defective in excystation. Thus, gPP2A-C localizes to universal cytoskeletal structures and to structures unique to Giardia. It is also important for encystation and excystation, crucial giardial transformations that entail entry into and exit from dormancy.
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MESH Headings
- Adaptation, Physiological
- Amino Acid Sequence
- Animals
- Blotting, Western
- Centrosome/chemistry
- Cytoskeleton/chemistry
- DNA, Protozoan/chemistry
- DNA, Protozoan/genetics
- Flagella/chemistry
- Gene Expression Regulation, Developmental
- Giardia lamblia/enzymology
- Giardia lamblia/genetics
- Giardia lamblia/growth & development
- Immunohistochemistry
- Microscopy, Fluorescence
- Molecular Sequence Data
- Morphogenesis/genetics
- Phosphoprotein Phosphatases/biosynthesis
- Phosphoprotein Phosphatases/genetics
- Phosphoprotein Phosphatases/metabolism
- Protein Phosphatase 2
- Protozoan Proteins/analysis
- Protozoan Proteins/genetics
- RNA, Protozoan/analysis
- RNA, Protozoan/genetics
- Sequence Analysis, DNA
- Sequence Homology, Amino Acid
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Affiliation(s)
- Tineke Lauwaet
- Department of Pathology, Division of Infectious Diseases, University of California, San Diego, CA 92103‐8416, USA
| | - Barbara J. Davids
- Department of Pathology, Division of Infectious Diseases, University of California, San Diego, CA 92103‐8416, USA
| | - Ascención Torres‐Escobar
- Department of Pathology, Division of Infectious Diseases, University of California, San Diego, CA 92103‐8416, USA
| | | | | | | | - Daniel Palm
- Department of Cell and Molecular Biology, Uppsala University, SE‐751 24 Uppsala, Sweden
| | - Staffan G. Svärd
- Department of Cell and Molecular Biology, Uppsala University, SE‐751 24 Uppsala, Sweden
| | | | - Frances D. Gillin
- Department of Pathology, Division of Infectious Diseases, University of California, San Diego, CA 92103‐8416, USA
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16
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Lal K, Field MC, Carlton JM, Warwicker J, Hirt RP. Identification of a very large Rab GTPase family in the parasitic protozoan Trichomonas vaginalis. Mol Biochem Parasitol 2005; 143:226-35. [PMID: 16099517 DOI: 10.1016/j.molbiopara.2005.06.008] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2005] [Accepted: 06/23/2005] [Indexed: 10/25/2022]
Abstract
Rab proteins are pivotal components of the membrane trafficking machinery in all eukaryotes. Distinct Rab proteins locate to specific endomembrane compartments and genomic studies suggest that Rab gene diversity correlates with endomembrane system complexity; for example unicellular organisms generally possess 5-20 Rab family members and the size of the repertoire increases to 25-60 in multicellular systems. Here we report 65 open reading frames from the unicellular protozoan Trichomonas vaginalis that encode distinct Rab proteins (TvRabs), indicating a family with complexity that rivals Homo sapiens in number. The detection of gene transcripts for the majority of these genes and conservation of functional motifs strongly suggests that TvRabs retain functionality and likely roles in membrane trafficking. The T. vaginalis Rab family includes orthologues of the conserved subfamilies, Rab1, Rab5, Rab6, Rab7 and Rab11, but the majority of TvRabs are not represented by orthologues in other systems and includes six novel T. vaginalis specific Rab subfamilies (A-F). The extreme size of the T. vaginalis Rab family, the presence of novel subfamilies plus the divergent nature of many TvRab sequences suggest both the presence of a highly complex endomembrane system within Trichomonas and potentially novel Rab functionality. A family of more than 65 Rab genes in a unicellular genome is unexpected, but may be a requirement for progression though an amoeboid life-cycle phase as both Dictyostelium discoideum and Entamoeba histolytica share with T. vaginalis both an amoeboid life cycle stage and very large Rab gene families.
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Affiliation(s)
- Kalpana Lal
- Department of Zoology, The Natural History Museum, South Kensington, London SW7 5BD, UK
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17
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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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18
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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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19
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Marti M, Hehl AB. Encystation-specific vesicles in Giardia: a primordial Golgi or just another secretory compartment? Trends Parasitol 2004; 19:440-6. [PMID: 14519581 DOI: 10.1016/s1471-4922(03)00201-0] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Affiliation(s)
- Matthias Marti
- Division of Infection and Immunity, The Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade, Parkville, Victoria 3050, Australia
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20
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Marti M, Regös A, Li Y, Schraner EM, Wild P, Müller N, Knopf LG, Hehl AB. An ancestral secretory apparatus in the protozoan parasite Giardia intestinalis. J Biol Chem 2003; 278:24837-48. [PMID: 12711599 DOI: 10.1074/jbc.m302082200] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The protozoan parasite Giardia intestinalis belongs to one of the earliest diverged eukaryotic lineages. This is also reflected in a simple intracellular organization, as Giardia lacks common subcellular compartments such as mitochondria, peroxisomes, and apparently also a Golgi apparatus. During encystation, developmentally regulated formation of large secretory compartments containing cyst wall material occurs. Despite the lack of any morphological similarities, these encystation-specific vesicles (ESVs) show several biochemical characteristics of maturing Golgi cisternae. Previous studies suggested that Golgi structure and function are induced only during encystation in Giardia, giving rise to the hypothesis that ESVs, as a Giardia Golgi equivalent, are generated de novo. Alternatively, ESV compartments could be built on the template structure of a cryptic Golgi in trophozoites in response to ER export of cyst wall material during encystation. We addressed this question by defining the molecular framework of the Giardia secretory apparatus using a comparative genomic approach. Analysis of the corresponding transcriptome during growth and encystation revealed surprisingly little stage-specific regulation. A panel of antibodies was generated against selected marker proteins to investigate the developmental dynamics of the endomembrane system. We show evidence that Giardia accommodates the export of large amounts of cyst wall material through re-organization of membrane compartment(s) in trophozoites with biochemical similarities to ESVs. This suggests that ESVs are selectively stabilized Golgi-like compartments in a unique and archetypical secretory system, which arise from a structural template in trophozoites rather than being generated de novo.
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Affiliation(s)
- Matthias Marti
- Institute of Parasitology, University of Zürich, Switzerland
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21
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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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22
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McGugan GC, Temesvari LA. Characterization of a Rab11-like GTPase, EhRab11, of Entamoeba histolytica. Mol Biochem Parasitol 2003; 129:137-46. [PMID: 12850258 DOI: 10.1016/s0166-6851(03)00115-4] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The Entamoeba histolytica Rab11 family of small molecular weight GTPases consists of three members, EhRab11, EhRab11B, and EhRab11C. The functions of these Rabs in Entamoeba have not been determined. Therefore, as an approach to elucidate the role of the Rab11 family of GTPases in Entamoeba, immunofluorescence microscopy was undertaken to define the subcellular localization of one member of this family, EhRab11. Under conditions of growth, EhRab11 displayed a punctate pattern in the cytoplasm of trophozoites. EhRab11 did not colocalize with markers for the Golgi apparatus, endoplasmic reticulum, pinosomes, phagosomes, or compartments formed by receptor-mediated endocytosis, suggesting that this Rab may not play a role in vesicle trafficking between these organelles. Under conditions of iron and serum starvation, EhRab11 was translocated to the periphery of the cell. The altered cellular localization was accompanied by multinucleation of the cells as well as the acquisition of detergent resistance by the cells, features that are characteristic of Entamoeba cysts. The translocation of EhRab11 to the periphery of the cell during iron and serum starvation was specific as the subcellular localizations of two other Rab GTPases, EhRab7 and EhRabA, were not altered under the same conditions. In addition, the formation of multinucleated cells by inhibition of cytokinesis was not sufficient to induce the translocation of EhRab11 to the cell periphery. Taken together, the data suggest that iron and serum starvation may induce encystation in E. histolytica and that EhRab11 may play a role in this process. Moreover, these studies are the first to describe a putative role for a Rab GTPase in encystation in Entamoeba sp.
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Affiliation(s)
- Glen C McGugan
- Department of Biological Sciences, Clemson University, 132 Long Hall, Clemson, SC 29634-1903, USA
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