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Possenti A, Di Cristina M, Nicastro C, Lunghi M, Messina V, Piro F, Tramontana L, Cherchi S, Falchi M, Bertuccini L, Spano F. Functional Characterization of the Thrombospondin-Related Paralogous Proteins Rhoptry Discharge Factors 1 and 2 Unveils Phenotypic Plasticity in Toxoplasma gondii Rhoptry Exocytosis. Front Microbiol 2022; 13:899243. [PMID: 35756016 PMCID: PMC9218915 DOI: 10.3389/fmicb.2022.899243] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2022] [Accepted: 05/11/2022] [Indexed: 11/13/2022] Open
Abstract
To gain access to the intracellular cytoplasmic niche essential for their growth and replication, apicomplexan parasites such as Toxoplasma gondii rely on the timely secretion of two types of apical organelles named micronemes and rhoptries. Rhoptry proteins are key to host cell invasion and remodeling, however, the molecular mechanisms underlying the tight control of rhoptry discharge are poorly understood. Here, we report the identification and functional characterization of two novel T. gondii thrombospondin-related proteins implicated in rhoptry exocytosis. The two proteins, already annotated as MIC15 and MIC14, were renamed rhoptry discharge factor 1 (RDF1) and rhoptry discharge factor 2 (RDF2) and found to be exclusive of the Coccidia class of apicomplexan parasites. Furthermore, they were shown to have a paralogous relationship and share a C-terminal transmembrane domain followed by a short cytoplasmic tail. Immunofluorescence analysis of T. gondii tachyzoites revealed that RDF1 presents a diffuse punctate localization not reminiscent of any know subcellular compartment, whereas RDF2 was not detected. Using a conditional knockdown approach, we demonstrated that RDF1 loss caused a marked growth defect. The lack of the protein did not affect parasite gliding motility, host cell attachment, replication and egress, whereas invasion was dramatically reduced. Notably, while RDF1 depletion did not result in altered microneme exocytosis, rhoptry discharge was found to be heavily impaired. Interestingly, rhoptry secretion was reversed by spontaneous upregulation of the RDF2 gene in knockdown parasites grown under constant RDF1 repression. Collectively, our results identify RDF1 and RDF2 as additional key players in the pathway controlling rhoptry discharge. Furthermore, this study unveils a new example of compensatory mechanism contributing to phenotypic plasticity in T. gondii.
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Affiliation(s)
- Alessia Possenti
- Department of Infectious Diseases, Istituto Superiore di Sanità, Rome, Italy
| | - Manlio Di Cristina
- Department of Chemistry, Biology and Biotechnology, University of Perugia, Perugia, Italy
| | - Chiara Nicastro
- Department of Infectious Diseases, Istituto Superiore di Sanità, Rome, Italy
| | - Matteo Lunghi
- Department of Chemistry, Biology and Biotechnology, University of Perugia, Perugia, Italy
| | - Valeria Messina
- Department of Infectious Diseases, Istituto Superiore di Sanità, Rome, Italy
| | - Federica Piro
- Department of Chemistry, Biology and Biotechnology, University of Perugia, Perugia, Italy
| | - Lorenzo Tramontana
- Department of Infectious Diseases, Istituto Superiore di Sanità, Rome, Italy
| | - Simona Cherchi
- Department of Infectious Diseases, Istituto Superiore di Sanità, Rome, Italy
| | - Mario Falchi
- National AIDS Center, Istituto Superiore di Sanità, Rome, Italy
| | | | - Furio Spano
- Department of Infectious Diseases, Istituto Superiore di Sanità, Rome, Italy
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2
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Kuppannan A, Jiang YY, Maier W, Liu C, Lang CF, Cheng CY, Field MC, Zhao M, Zoltner M, Turkewitz AP. A novel membrane complex is required for docking and regulated exocytosis of lysosome-related organelles in Tetrahymena thermophila. PLoS Genet 2022; 18:e1010194. [PMID: 35587496 PMCID: PMC9159632 DOI: 10.1371/journal.pgen.1010194] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2021] [Revised: 06/01/2022] [Accepted: 04/06/2022] [Indexed: 12/20/2022] Open
Abstract
In the ciliate Tetrahymena thermophila, lysosome-related organelles called mucocysts accumulate at the cell periphery where they secrete their contents in response to extracellular events, a phenomenon called regulated exocytosis. The molecular bases underlying regulated exocytosis have been extensively described in animals but it is not clear whether similar mechanisms exist in ciliates or their sister lineage, the Apicomplexan parasites, which together belong to the ecologically and medically important superphylum Alveolata. Beginning with a T. thermophila mutant in mucocyst exocytosis, we used a forward genetic approach to uncover MDL1 (Mucocyst Discharge with a LamG domain), a novel gene that is essential for regulated exocytosis of mucocysts. Mdl1p is a 40 kDa membrane glycoprotein that localizes to mucocysts, and specifically to a tip domain that contacts the plasma membrane when the mucocyst is docked. This sub-localization of Mdl1p, which occurs prior to docking, underscores a functional asymmetry in mucocysts that is strikingly similar to that of highly polarized secretory organelles in other Alveolates. A mis-sense mutation in the LamG domain results in mucocysts that dock but only undergo inefficient exocytosis. In contrast, complete knockout of MDL1 largely prevents mucocyst docking itself. Mdl1p is physically associated with 9 other proteins, all of them novel and largely restricted to Alveolates, and sedimentation analysis supports the idea that they form a large complex. Analysis of three other members of this putative complex, called MDD (for Mucocyst Docking and Discharge), shows that they also localize to mucocysts. Negative staining of purified MDD complexes revealed distinct particles with a central channel. Our results uncover a novel macromolecular complex whose subunits are conserved within alveolates but not in other lineages, that is essential for regulated exocytosis in T. thermophila.
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Affiliation(s)
- Aarthi Kuppannan
- Molecular Genetics and Cell Biology, The University of Chicago, Chicago, Illinois, United State of America
| | - Yu-Yang Jiang
- Molecular Genetics and Cell Biology, The University of Chicago, Chicago, Illinois, United State of America
| | - Wolfgang Maier
- Bio3/Bioinformatics and Molecular Genetics, Faculty of Biology and ZBMZ, Faculty of Medicine, Albert-Ludwigs-University of Freiburg, Freiburg, Germany
| | - Chang Liu
- Biochemistry and Molecular Biology, The University of Chicago, Chicago, Illinois, United States of America
| | - Charles F. Lang
- Committee on Genetics, Genomics, and Systems Biology, The University of Chicago, Chicago, Illinois, United States of America
| | - Chao-Yin Cheng
- Molecular Genetics and Cell Biology, The University of Chicago, Chicago, Illinois, United State of America
| | - Mark C. Field
- School of Life Sciences, University of Dundee, Dundee, Scotland, United Kingdom
- Institute of Parasitology, Biology Centre, Czech Academy of Sciences, České Budějovice, Czech Republic
| | - Minglei Zhao
- Biochemistry and Molecular Biology, The University of Chicago, Chicago, Illinois, United States of America
| | - Martin Zoltner
- Biotechnology and Biomedicine Centre of the Academy of Sciences and Charles University (BIOCEV), Vestec, Czech Republic
| | - Aaron P. Turkewitz
- Molecular Genetics and Cell Biology, The University of Chicago, Chicago, Illinois, United State of America
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3
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Mageswaran SK, Guérin A, Theveny LM, Chen WD, Martinez M, Lebrun M, Striepen B, Chang YW. In situ ultrastructures of two evolutionarily distant apicomplexan rhoptry secretion systems. Nat Commun 2021; 12:4983. [PMID: 34404783 PMCID: PMC8371170 DOI: 10.1038/s41467-021-25309-9] [Citation(s) in RCA: 31] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2020] [Accepted: 08/03/2021] [Indexed: 12/03/2022] Open
Abstract
Parasites of the phylum Apicomplexa cause important diseases including malaria, cryptosporidiosis and toxoplasmosis. These intracellular pathogens inject the contents of an essential organelle, the rhoptry, into host cells to facilitate invasion and infection. However, the structure and mechanism of this eukaryotic secretion system remain elusive. Here, using cryo-electron tomography and subtomogram averaging, we report the conserved architecture of the rhoptry secretion system in the invasive stages of two evolutionarily distant apicomplexans, Cryptosporidium parvum and Toxoplasma gondii. In both species, we identify helical filaments, which appear to shape and compartmentalize the rhoptries, and an apical vesicle (AV), which facilitates docking of the rhoptry tip at the parasite's apical region with the help of an elaborate ultrastructure named the rhoptry secretory apparatus (RSA); the RSA anchors the AV at the parasite plasma membrane. Depletion of T. gondii Nd9, a protein required for rhoptry secretion, disrupts the RSA ultrastructure and AV-anchoring. Moreover, T. gondii contains a line of AV-like vesicles, which interact with a pair of microtubules and accumulate towards the AV, leading to a working model for AV-reloading and discharging of multiple rhoptries. Together, our analyses provide an ultrastructural framework to understand how these important parasites deliver effectors into host cells.
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Affiliation(s)
- Shrawan Kumar Mageswaran
- Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Amandine Guérin
- Department of Pathobiology, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Liam M Theveny
- Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - William David Chen
- Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Matthew Martinez
- Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Maryse Lebrun
- LPHI, UMR 5235 CNRS, Université de Montpellier, Montpellier, France
| | - Boris Striepen
- Department of Pathobiology, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Yi-Wei Chang
- Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA.
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4
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Sparvoli D, Lebrun M. Unraveling the Elusive Rhoptry Exocytic Mechanism of Apicomplexa. Trends Parasitol 2021; 37:622-637. [PMID: 34045149 DOI: 10.1016/j.pt.2021.04.011] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2021] [Revised: 04/19/2021] [Accepted: 04/19/2021] [Indexed: 12/11/2022]
Abstract
Apicomplexan parasites are unicellular eukaryotes that invade the cells in which they proliferate. The development of genetic tools in Toxoplasma, and then in Plasmodium, in the 1990s allowed the first description of the molecular machinery used for motility and invasion, revealing a crucial role for two different secretory organelles, micronemes and rhoptries. Rhoptry proteins are injected directly into the host cytoplasm not only to promote invasion but also to manipulate host functions. Nonetheless, the injection machinery has remained mysterious, a major conundrum in the field. Here we review recent progress in uncovering structural components and proteins implicated in rhoptry exocytosis and explain how revisiting early findings and considering the evolutionary origins of Apicomplexa contributed to some of these discoveries.
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Affiliation(s)
- Daniela Sparvoli
- LPHI UMR5235, Univ Montpellier, CNRS, F-34095 Montpellier, France
| | - Maryse Lebrun
- LPHI UMR5235, Univ Montpellier, CNRS, F-34095 Montpellier, France.
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5
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Aquilini E, Cova MM, Mageswaran SK, Dos Santos Pacheco N, Sparvoli D, Penarete-Vargas DM, Najm R, Graindorge A, Suarez C, Maynadier M, Berry-Sterkers L, Urbach S, Fahy PR, Guérin AN, Striepen B, Dubremetz JF, Chang YW, Turkewitz AP, Lebrun M. An Alveolata secretory machinery adapted to parasite host cell invasion. Nat Microbiol 2021; 6:425-434. [PMID: 33495622 PMCID: PMC8886610 DOI: 10.1038/s41564-020-00854-z] [Citation(s) in RCA: 39] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2020] [Accepted: 12/14/2020] [Indexed: 01/29/2023]
Abstract
Apicomplexa are unicellular eukaryotes and obligate intracellular parasites, including Plasmodium (the causative agent of malaria) and Toxoplasma (one of the most widespread zoonotic pathogens). Rhoptries, one of their specialized secretory organelles, undergo regulated exocytosis during invasion1. Rhoptry proteins are injected directly into the host cell to support invasion and subversion of host immune function2. The mechanism by which they are discharged is unclear and appears distinct from those in bacteria, yeast, animals and plants. Here, we show that rhoptry secretion in Apicomplexa shares structural and genetic elements with the exocytic machinery of ciliates, their free-living relatives. Rhoptry exocytosis depends on intramembranous particles in the shape of a rosette embedded into the plasma membrane of the parasite apex. Formation of this rosette requires multiple non-discharge (Nd) proteins conserved and restricted to Ciliata, Dinoflagellata and Apicomplexa that together constitute the superphylum Alveolata. We identified Nd6 at the site of exocytosis in association with an apical vesicle. Sandwiched between the rosette and the tip of the rhoptry, this vesicle appears as a central element of the rhoptry secretion machine. Our results describe a conserved secretion system that was adapted to provide defence for free-living unicellular eukaryotes and host cell injection in intracellular parasites.
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Affiliation(s)
- Eleonora Aquilini
- Laboratory of Pathogen Host Interactions UMR 5235, Université de Montpellier and CNRS, Montpellier, France
| | - Marta Mendonça Cova
- Laboratory of Pathogen Host Interactions UMR 5235, Université de Montpellier and CNRS, Montpellier, France
| | - Shrawan Kumar Mageswaran
- Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Nicolas Dos Santos Pacheco
- Laboratory of Pathogen Host Interactions UMR 5235, Université de Montpellier and CNRS, Montpellier, France
| | - Daniela Sparvoli
- Laboratory of Pathogen Host Interactions UMR 5235, Université de Montpellier and CNRS, Montpellier, France
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL, USA
| | | | - Rania Najm
- Laboratory of Pathogen Host Interactions UMR 5235, Université de Montpellier and CNRS, Montpellier, France
| | - Arnault Graindorge
- Laboratory of Pathogen Host Interactions UMR 5235, Université de Montpellier and CNRS, Montpellier, France
| | - Catherine Suarez
- Laboratory of Pathogen Host Interactions UMR 5235, Université de Montpellier and CNRS, Montpellier, France
| | - Marjorie Maynadier
- Laboratory of Pathogen Host Interactions UMR 5235, Université de Montpellier and CNRS, Montpellier, France
| | - Laurence Berry-Sterkers
- Laboratory of Pathogen Host Interactions UMR 5235, Université de Montpellier and CNRS, Montpellier, France
| | - Serge Urbach
- Institut de Génomique Fonctionnelle (IGF), Université de Montpellier, CNRS and INSERM, Montpellier, France
| | - Pilar Ruga Fahy
- Pôle Facultaire de Microscopie Ultrastructurale, Geneva, Switzerland
| | - Amandine N Guérin
- Department of Pathobiology, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Boris Striepen
- Department of Pathobiology, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Jean-François Dubremetz
- Laboratory of Pathogen Host Interactions UMR 5235, Université de Montpellier and CNRS, Montpellier, France
| | - Yi-Wei Chang
- Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Aaron P Turkewitz
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL, USA
| | - Maryse Lebrun
- Laboratory of Pathogen Host Interactions UMR 5235, Université de Montpellier and CNRS, Montpellier, France.
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6
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Environmental Temperature Controls Accumulation of Transacting siRNAs Involved in Heterochromatin Formation. Genes (Basel) 2018; 9:genes9020117. [PMID: 29466322 PMCID: PMC5852613 DOI: 10.3390/genes9020117] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2018] [Revised: 02/06/2018] [Accepted: 02/12/2018] [Indexed: 12/25/2022] Open
Abstract
Genes or alleles can interact by small RNAs in a homology dependent manner meaning that short interfering (siRNAs) can act in trans at the chromatin level producing stable and heritable silencing phenotypes. Because of the puzzling data on endogenous paramutations, their impact contributing to adaptive evolution in a Lamarckian manner remains unknown. An increasing number of studies characterizes the underlying siRNA accumulation pathways using transgene experiments. Also in the ciliate Paramecium tetraurelia, we induce trans silencing on the chromatin level by injection of truncated transgenes. Here, we characterize the efficiency of this mechanism at different temperatures showing that silencing of the endogenous genes is temperature dependent. Analyzing different transgene constructs at different copy numbers, we dissected whether silencing efficiency is due to varying precursor RNAs or siRNA accumulation. Our data shows that silencing efficiency correlates with more efficient accumulation of primary siRNAs at higher temperatures rather than higher expression of precursor RNAs. Due to higher primary levels, secondary siRNAs also show temperature dependency and interestingly increase their relative proportion to primary siRNAs. Our data shows that efficient trans silencing on the chromatin level in P. tetraurelia depends on environmental parameters, thus being an important epigenetic factor limiting regulatory effects of siRNAs.
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7
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Plattner H. Trichocysts-Paramecium'sProjectile-like Secretory Organelles. J Eukaryot Microbiol 2016; 64:106-133. [DOI: 10.1111/jeu.12332] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2016] [Revised: 05/09/2016] [Accepted: 05/21/2016] [Indexed: 12/31/2022]
Affiliation(s)
- Helmut Plattner
- Department of Biology; University of Konstanz; PO Box M625 78457 Konstanz Germany
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8
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Plattner H. Signalling in ciliates: long- and short-range signals and molecular determinants for cellular dynamics. Biol Rev Camb Philos Soc 2015; 92:60-107. [PMID: 26487631 DOI: 10.1111/brv.12218] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2015] [Revised: 07/28/2015] [Accepted: 08/21/2015] [Indexed: 12/30/2022]
Abstract
In ciliates, unicellular representatives of the bikont branch of evolution, inter- and intracellular signalling pathways have been analysed mainly in Paramecium tetraurelia, Paramecium multimicronucleatum and Tetrahymena thermophila and in part also in Euplotes raikovi. Electrophysiology of ciliary activity in Paramecium spp. is a most successful example. Established signalling mechanisms include plasmalemmal ion channels, recently established intracellular Ca2+ -release channels, as well as signalling by cyclic nucleotides and Ca2+ . Ca2+ -binding proteins (calmodulin, centrin) and Ca2+ -activated enzymes (kinases, phosphatases) are involved. Many organelles are endowed with specific molecules cooperating in signalling for intracellular transport and targeted delivery. Among them are recently specified soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs), monomeric GTPases, H+ -ATPase/pump, actin, etc. Little specification is available for some key signal transducers including mechanosensitive Ca2+ -channels, exocyst complexes and Ca2+ -sensor proteins for vesicle-vesicle/membrane interactions. The existence of heterotrimeric G-proteins and of G-protein-coupled receptors is still under considerable debate. Serine/threonine kinases dominate by far over tyrosine kinases (some predicted by phosphoproteomic analyses). Besides short-range signalling, long-range signalling also exists, e.g. as firmly installed microtubular transport rails within epigenetically determined patterns, thus facilitating targeted vesicle delivery. By envisaging widely different phenomena of signalling and subcellular dynamics, it will be shown (i) that important pathways of signalling and cellular dynamics are established already in ciliates, (ii) that some mechanisms diverge from higher eukaryotes and (iii) that considerable uncertainties still exist about some essential aspects of signalling.
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Affiliation(s)
- Helmut Plattner
- Department of Biology, University of Konstanz, PO Box M625, 78457, Konstanz, Germany
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9
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Marker S, Carradec Q, Tanty V, Arnaiz O, Meyer E. A forward genetic screen reveals essential and non-essential RNAi factors in Paramecium tetraurelia. Nucleic Acids Res 2014; 42:7268-80. [PMID: 24860163 PMCID: PMC4066745 DOI: 10.1093/nar/gku223] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
In most eukaryotes, small RNA-mediated gene silencing pathways form complex interacting networks. In the ciliate Paramecium tetraurelia, at least two RNA interference (RNAi) mechanisms coexist, involving distinct but overlapping sets of protein factors and producing different types of short interfering RNAs (siRNAs). One is specifically triggered by high-copy transgenes, and the other by feeding cells with double-stranded RNA (dsRNA)-producing bacteria. In this study, we designed a forward genetic screen for mutants deficient in dsRNA-induced silencing, and a powerful method to identify the relevant mutations by whole-genome sequencing. We present a set of 47 mutant alleles for five genes, revealing two previously unknown RNAi factors: a novel Paramecium-specific protein (Pds1) and a Cid1-like nucleotidyl transferase. Analyses of allelic diversity distinguish non-essential and essential genes and suggest that the screen is saturated for non-essential, single-copy genes. We show that non-essential genes are specifically involved in dsRNA-induced RNAi while essential ones are also involved in transgene-induced RNAi. One of the latter, the RNA-dependent RNA polymerase RDR2, is further shown to be required for all known types of siRNAs, as well as for sexual reproduction. These results open the way for the dissection of the genetic complexity, interconnection, mechanisms and natural functions of RNAi pathways in P. tetraurelia.
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Affiliation(s)
- Simone Marker
- Ecole Normale Supérieure, Institut de Biologie de l'ENS, IBENS, Inserm, U1024, CNRS, UMR 8197, Paris F-75005, France
| | - Quentin Carradec
- Ecole Normale Supérieure, Institut de Biologie de l'ENS, IBENS, Inserm, U1024, CNRS, UMR 8197, Paris F-75005, France Sorbonne Universités, UPMC Univ., IFD, 4 place Jussieu, F-75252 Paris cedex 05, France
| | - Véronique Tanty
- Ecole Normale Supérieure, Institut de Biologie de l'ENS, IBENS, Inserm, U1024, CNRS, UMR 8197, Paris F-75005, France
| | - Olivier Arnaiz
- CNRS UPR3404 Centre de Génétique Moléculaire, Gif-sur-Yvette F-91198 cedex, France; Université Paris-Sud, Département de Biologie, Orsay, F-91405, France
| | - Eric Meyer
- Ecole Normale Supérieure, Institut de Biologie de l'ENS, IBENS, Inserm, U1024, CNRS, UMR 8197, Paris F-75005, France
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10
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Briguglio JS, Turkewitz AP. Tetrahymena thermophila: a divergent perspective on membrane traffic. JOURNAL OF EXPERIMENTAL ZOOLOGY PART B-MOLECULAR AND DEVELOPMENTAL EVOLUTION 2014; 322:500-16. [PMID: 24634411 DOI: 10.1002/jez.b.22564] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/03/2013] [Revised: 01/13/2014] [Accepted: 01/22/2014] [Indexed: 12/12/2022]
Abstract
Tetrahymena thermophila, a member of the Ciliates, represents a class of organisms distantly related from commonly used model organisms in cell biology, and thus offers an opportunity to explore potentially novel mechanisms and their evolution. Ciliates, like all eukaryotes, possess a complex network of organelles that facilitate both macromolecular uptake and secretion. The underlying endocytic and exocytic pathways are key mediators of a cell's interaction with its environment, and may therefore show niche-specific adaptations. Our laboratory has taken a variety of approaches to identify key molecular determinants for membrane trafficking pathways in Tetrahymena. Studies of Rab GTPases, dynamins, and sortilin-family receptors substantiate the widespread conservation of some features but also uncover surprising roles for lineage-restricted innovation.
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Affiliation(s)
- Joseph S Briguglio
- The Department of Molecular Genetics and Cell Biology, The University of Chicago, Chicago, Illinois
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11
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Cheaib M, Simon M. Dynamic chromatin remodelling of ciliate macronuclear DNA as determined by an optimized chromatin immunoprecipitation (ChIP) method for Paramecium tetraurelia. Appl Microbiol Biotechnol 2013; 97:2661-70. [PMID: 23385475 DOI: 10.1007/s00253-013-4708-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2012] [Revised: 01/04/2013] [Accepted: 01/07/2013] [Indexed: 01/08/2023]
Abstract
We report the detailed evaluation of crucial parameters for chromatin immunoprecipitation (ChIP) of macronuclear DNA in the unicellular eukaryote Paramecium tetraurelia. Optimized parameters include crosslinking conditions, chromatin sonication and antibody titration thus providing a detailed protocol for successful ChIP in P. tetraurelia. As this ciliate is bacterivorous and RNAi by feeding represents a powerful tool for analysis of gene function, we moreover determined the effects of ingested nucleic acids by food bacteria. Feasibility of our protocol is demonstrated by characterisation of chromatin remodelling at promoters of cytosolic HSP70 isoforms during transcriptional activation under heat shock conditions by analyzing RNA abundance, nucleosome occupancy and levels of H3 lysine 9 acetylation.
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Affiliation(s)
- Miriam Cheaib
- Faculty of Biology, Molecular Protistology, University of Kaiserslautern, Gottlieb-Daimler Straße Building 14, 67663 Kaiserslautern, Germany
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12
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Bouhouche K, Gout JF, Kapusta A, Bétermier M, Meyer E. Functional specialization of Piwi proteins in Paramecium tetraurelia from post-transcriptional gene silencing to genome remodelling. Nucleic Acids Res 2011; 39:4249-64. [PMID: 21216825 PMCID: PMC3105430 DOI: 10.1093/nar/gkq1283] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Proteins of the Argonaute family are small RNA carriers that guide regulatory complexes to their targets. The family comprises two major subclades. Members of the Ago subclade, which are present in most eukaryotic phyla, bind different classes of small RNAs and regulate gene expression at both transcriptional and post-transcriptional levels. Piwi subclade members appear to have been lost in plants and fungi and were mostly studied in metazoa, where they bind piRNAs and have essential roles in sexual reproduction. Their presence in ciliates, unicellular organisms harbouring both germline micronuclei and somatic macronuclei, offers an interesting perspective on the evolution of their functions. Here, we report phylogenetic and functional analyses of the 15 Piwi genes from Paramecium tetraurelia. We show that four constitutively expressed proteins are involved in siRNA pathways that mediate gene silencing throughout the life cycle. Two other proteins, specifically expressed during meiosis, are required for accumulation of scnRNAs during sexual reproduction and for programmed genome rearrangements during development of the somatic macronucleus. Our results indicate that Paramecium Piwi proteins have evolved to perform both vegetative and sexual functions through mechanisms ranging from post-transcriptional mRNA cleavage to epigenetic regulation of genome rearrangements.
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Affiliation(s)
- Khaled Bouhouche
- Institut de Biologie de l'Ecole Normale Supérieure, CNRS UMR8197, INSERM U1024, 46 rue d'Ulm, 75005 Paris, France
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13
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Beisson J, Bétermier M, Bré MH, Cohen J, Duharcourt S, Duret L, Kung C, Malinsky S, Meyer E, Preer JR, Sperling L. Paramecium tetraurelia: the renaissance of an early unicellular model. Cold Spring Harb Protoc 2010; 2010:pdb.emo140. [PMID: 20150105 DOI: 10.1101/pdb.emo140] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Affiliation(s)
- Janine Beisson
- Centre de Génétique Moléculaire, Centre National de la Recherche Scientifique, FRE3144, F-91198 Gif-sur-Yvette, France
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Dotzauer D, Wolfenstetter S, Eibert D, Schneider S, Dietrich P, Sauer N. Novel PSI Domains in Plant and Animal H+-Inositol Symporters. Traffic 2010; 11:767-81. [DOI: 10.1111/j.1600-0854.2010.01057.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
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15
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Plattner H. Membrane Trafficking in Protozoa. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2010; 280:79-184. [DOI: 10.1016/s1937-6448(10)80003-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
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16
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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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17
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Elde NC, Long M, Turkewitz AP. A role for convergent evolution in the secretory life of cells. Trends Cell Biol 2007; 17:157-64. [PMID: 17329106 DOI: 10.1016/j.tcb.2007.02.007] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2006] [Revised: 01/19/2007] [Accepted: 02/14/2007] [Indexed: 10/23/2022]
Abstract
The role of convergent evolution in biological adaptation is increasingly appreciated. Many clear examples have been described at the level of individual proteins and for organismal morphology, and convergent mechanisms have even been invoked to account for similar community structures that are shared between ecosystems. At the cellular level, an important area that has received scant attention is the potential influence of convergent evolution on complex subcellular features, such as organelles. Here, we show that existing data strongly argue that convergent evolution underlies the similar properties of specialized secretory vesicles, called dense core granules, in the animal and ciliate lineages. We discuss both the criteria for judging convergent evolution and the contribution that such evolutionary analysis can make to improve our understanding of processes in cell biology. The elucidation of these underlying evolutionary relationships is vital because cellular structures that are assumed to be analogous, owing to shared features, might in fact be governed by different molecular mechanisms.
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Affiliation(s)
- Nels C Elde
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA
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18
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Azouz A, Gunn TM, Duke-Cohan JS. Juvenile-onset loss of lipid-raft domains in attractin-deficient mice. Exp Cell Res 2006; 313:761-71. [PMID: 17196964 DOI: 10.1016/j.yexcr.2006.11.018] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2006] [Revised: 11/09/2006] [Accepted: 11/27/2006] [Indexed: 11/29/2022]
Abstract
Mutations at the attractin (Atrn) locus in mice result in altered pigmentation on an agouti background, higher basal metabolic rate and juvenile-onset hypomyelination leading to neurodegeneration, while studies on human immune cells indicate a chemotaxis regulatory function. The underlying biochemical defect remains elusive. In this report we identify a role for attractin in plasma membrane maintenance. In attractin's absence there is a decline in plasma membrane glycolipid-enriched rafts from normal levels at 8 weeks to a complete absence by 24 weeks. The structural integrity of lipid rafts depends upon cholesterol and sphingomyelin, and can be identified by partitioning within of ganglioside GM(1). Despite a significant fall in cellular cholesterol with maturity, and a lesser fall in both membrane and total cellular GM(1), these parameters lag behind raft loss, and are normal when hypomyelination/neurodegeneration has already begun thus supporting consequence rather than cause. These findings can be recapitulated in Atrn-deficient cell lines propagated in vitro. Further, signal transduction through complex membrane receptor assemblies is not grossly disturbed despite the complete absence of lipid rafts. We find these results compatible with a role for attractin in plasma membrane maintenance and consistent with the proposal that the juvenile-onset hypomyelination and neurodegeneration represent a defect in attractin-mediated raft-dependent myelin biogenesis.
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Affiliation(s)
- Abdallah Azouz
- Department of Medical Oncology, Dana-Farber Cancer Institute, and Department of Medicine, Harvard Medical School, Boston, MA 02115, USA
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19
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Gogendeau D, Keller AM, Yanagi A, Cohen J, Koll F. Nd6p, a novel protein with RCC1-like domains involved in exocytosis in Paramecium tetraurelia. EUKARYOTIC CELL 2006; 4:2129-39. [PMID: 16339730 PMCID: PMC1317492 DOI: 10.1128/ec.4.12.2129-2139.2005] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
In Paramecium tetraurelia, the regulated secretory pathway of dense core granules called trichocysts can be altered by mutation and genetically studied. Seventeen nondischarge (ND) genes controlling exocytosis have already been identified by a genetic approach. The site of action of the studied mutations is one of the three compartments, the cytosol, trichocyst, or plasma membrane. The only ND genes cloned to date correspond to mutants affected in the cytosol or in the trichocyst compartment. In this work, we investigated a representative of the third compartment, the plasma membrane, by cloning the ND6 gene. This gene encodes a 1,925-amino-acid protein containing two domains homologous to the regulator of chromosome condensation 1 (RCC1). In parallel, 10 new alleles of the ND6 gene were isolated. Nine of the 12 available mutations mapped in the RCC1-like domains, showing their importance for the Nd6 protein (Nd6p) function. The RCC1 protein is well known for its guanine exchange factor activity towards the small GTPase Ran but also for its involvement in membrane fusion during nuclear envelope assembly. Other proteins with RCC1-like domains are also involved in intracellular membrane fusion, but none has been described yet as involved in exocytosis. The case of Nd6p is thus the first report of such a protein with a documented role in exocytosis.
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Affiliation(s)
- Delphine Gogendeau
- Centre de Génétique Moléculaire, CNRS, 1 avenue de la terrasse, 91198 Gif-sur-Yvette, France.
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Pomel S, Diogon M, Bouchard P, Pradel L, Ravet V, Coffe G, Viguès B. The Membrane Skeleton in Paramecium: Molecular Characterization of a Novel Epiplasmin Family and Preliminary GFP Expression Results. Protist 2006; 157:61-75. [PMID: 16427359 DOI: 10.1016/j.protis.2005.11.002] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2005] [Revised: 10/23/2005] [Accepted: 10/23/2005] [Indexed: 11/30/2022]
Abstract
Previous attempts to identify the membrane skeleton of Paramecium cells have revealed a protein pattern that is both complex and specific. The most prominent structural elements, epiplasmic scales, are centered around ciliary units and are closely apposed to the cytoplasmic side of the inner alveolar membrane. We sought to characterize epiplasmic scale proteins (epiplasmins) at the molecular level. PCR approaches enabled the cloning and sequencing of two closely related genes by amplifications of sequences from a macronuclear genomic library. Using these two genes (EPI-1 and EPI-2), we have contributed to the annotation of the Paramecium tetraurelia macronuclear genome and identified 39 additional (paralogous) sequences. Two orthologous sequences were found in the Tetrahymena thermophila genome. Structural analysis of the 43 sequences indicates that the hallmark of this new multigenic family is a 79 aa domain flanked by two Q-, P- and V-rich stretches of sequence that are much more variable in amino-acid composition. Such features clearly distinguish members of the multigenic family from epiplasmic proteins previously sequenced in other ciliates. The expression of Green Fluorescent Protein (GFP)-tagged epiplasmin showed significant labeling of epiplasmic scales as well as oral structures. We expect that the GFP construct described herein will prove to be a useful tool for comparative subcellular localization of different putative epiplasmins in Paramecium.
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Affiliation(s)
- Sébastien Pomel
- Laboratoire de Biologie des Protistes, UMR CNRS 6023, Université Blaise Pascal, 63177 Aubière cedex, France
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