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Lorestani A, Ivey FD, Thirugnanam S, Busby MA, Marth GT, Cheeseman IM, Gubbels MJ. Targeted proteomic dissection of Toxoplasma cytoskeleton sub-compartments using MORN1. Cytoskeleton (Hoboken) 2012; 69:1069-85. [PMID: 23027733 DOI: 10.1002/cm.21077] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2012] [Revised: 09/06/2012] [Accepted: 09/10/2012] [Indexed: 12/25/2022]
Abstract
The basal complex in Toxoplasma functions as the contractile ring in the cell division process. Basal complex contraction tapers the daughter cytoskeleton toward the basal end and is required for daughter segregation. We have previously shown that the protein MORN1 is essential for basal complex assembly and likely acts as a scaffolding protein. To further our understanding of the basal complex, we combined subcellular fractionation with an affinity purification of the MORN1 complex and identified its protein composition. We identified two new components of the basal complex, one of which uniquely associated with the basal complex in mature parasites, the first of its kind. In addition, we identified several other novel cytoskeleton proteins with different spatiotemporal dynamics throughout cell division. Since many of these proteins are unique to Apicomplexa this study significantly contributes to the annotation of their unique cytoskeleton. Furthermore, we show that G-actin binding protein TgCAP is localized at the apical cap region in intracellular parasites, but quickly redistributes to a cytoplasmic localization pattern upon egress. © 2012 Wiley Periodicals, Inc.
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52
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Jacot D, Soldati-Favre D. Does protein phosphorylation govern host cell entry and egress by the Apicomplexa? Int J Med Microbiol 2012; 302:195-202. [DOI: 10.1016/j.ijmm.2012.07.012] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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53
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Olshina MA, Wong W, Baum J. Holding back the microfilament--structural insights into actin and the actin-monomer-binding proteins of apicomplexan parasites. IUBMB Life 2012; 64:370-7. [PMID: 22454107 DOI: 10.1002/iub.1014] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2012] [Accepted: 02/03/2012] [Indexed: 01/02/2023]
Abstract
Parasites from the phylum Apicomplexa are responsible for several major diseases of man, including malaria and toxoplasmosis. These highly motile protozoa use a conserved actomyosin-based mode of movement to power tissue traversal and host cell invasion. The mode termed as 'gliding motility' relies on the dynamic turnover of actin, whose polymerisation state is controlled by a markedly limited number of identifiable regulators when compared with other eukaryotic cells. Recent studies of apicomplexan actin regulator structure-in particular those of the core triad of monomer-binding proteins, actin-depolymerising factor/cofilin, cyclase-associated protein/Srv2, and profilin-have provided new insights into possible mechanisms of actin regulation in parasite cells, highlighting divergent structural features and functions to regulators from other cellular systems. Furthermore, the unusual nature of apicomplexan actin itself is increasingly coming into the spotlight. Here, we review recent advances in understanding of the structure and function of actin and its regulators in apicomplexan parasites. In particular we explore the paradox between there being an abundance of unpolymerised actin, its having a seemingly increased potential to form filaments relative to vertebrate actin, and the apparent lack of visible, stable filaments in parasite cells.
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Affiliation(s)
- Maya A Olshina
- Division of Infection and Immunity, The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia
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Skillman KM, Daher W, Ma CI, Soldati-Favre D, Sibley LD. Toxoplasma gondii profilin acts primarily to sequester G-actin while formins efficiently nucleate actin filament formation in vitro. Biochemistry 2012; 51:2486-95. [PMID: 22397711 DOI: 10.1021/bi201704y] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Apicomplexan parasites employ gliding motility that depends on the polymerization of parasite actin filaments for host cell entry. Despite this requirement, parasite actin remains almost entirely unpolymerized at steady state; formation of filaments required for motility relies on a small repertoire of actin-binding proteins. Previous studies have shown that apicomplexan formins and profilin exhibit canonical functions on heterologous actins from higher eukaryotes; however, their biochemical properties on parasite actins are unknown. We therefore analyzed the impact of T. gondii profilin (TgPRF) and FH1-FH2 domains of two formin isoforms in T. gondii (TgFRM1 and TgFRM2) on the polymerization of T. gondii actin (TgACTI). Our findings based on in vitro assays demonstrate that TgFRM1-FH1-FH2 and TgFRM2-FH1-FH2 dramatically enhanced TgACTI polymerization in the absence of profilin, making them the sole protein factors known to initiate polymerization of this normally unstable actin. In addition, T. gondii formin domains were shown to both initiate polymerization and induce bundling of TgACTI filaments; however, they did not rely on TgPRF for these activities. In contrast, TgPRF sequestered TgACTI monomers, thus inhibiting polymerization even in the presence of formins. Collectively, these findings provide insight into the unusual control mechanisms of actin dynamics within the parasite.
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Affiliation(s)
- Kristen M Skillman
- Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri 63110, United States
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55
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Ignatev A, Bhargav SP, Vahokoski J, Kursula P, Kursula I. The lasso segment is required for functional dimerization of the Plasmodium formin 1 FH2 domain. PLoS One 2012; 7:e33586. [PMID: 22428073 PMCID: PMC3302767 DOI: 10.1371/journal.pone.0033586] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2011] [Accepted: 02/16/2012] [Indexed: 11/25/2022] Open
Abstract
Apicomplexan parasites, such as the malaria-causing Plasmodium species, utilize a unique way of locomotion and host cell invasion. This substrate-dependent gliding motility requires rapid cycling of actin between the monomeric state and very short, unbranched filaments. Despite the crucial role of actin polymerization for the survival of the malaria parasite, the majority of Plasmodium cellular actin is present in the monomeric form. Plasmodium lacks most of the canonical actin nucleators, and formins are essentially the only candidates for this function in all Apicomplexa. The malaria parasite has two formins, containing conserved formin homology (FH) 2 and rudimentary FH1 domains. Here, we show that Plasmodium falciparum formin 1 associates with and nucleates both mammalian and Plasmodium actin filaments. Although Plasmodium profilin alone sequesters actin monomers, thus inhibiting polymerization, its monomer-sequestering activity does not compete with the nucleating activity of formin 1 at an equimolar profilin-actin ratio. We have determined solution structures of P. falciparum formin 1 FH2 domain both in the presence and absence of the lasso segment and the FH1 domain, and show that the lasso is required for the assembly of functional dimers.
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Affiliation(s)
| | | | - Juha Vahokoski
- Department of Biochemistry, University of Oulu, Oulu, Finland
| | - Petri Kursula
- Department of Biochemistry, University of Oulu, Oulu, Finland
- Biocenter Oulu, University of Oulu, Oulu, Finland
- Department of Chemistry, Centre for Structural Systems Biology, Helmholtz Centre for Infection Research, University of Hamburg, and German Electron Synchrotron (DESY), Hamburg, Germany
| | - Inari Kursula
- Department of Biochemistry, University of Oulu, Oulu, Finland
- Department of Chemistry, Centre for Structural Systems Biology, Helmholtz Centre for Infection Research, University of Hamburg, and German Electron Synchrotron (DESY), Hamburg, Germany
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56
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Angrisano F, Riglar DT, Sturm A, Volz JC, Delves MJ, Zuccala ES, Turnbull L, Dekiwadia C, Olshina MA, Marapana DS, Wong W, Mollard V, Bradin CH, Tonkin CJ, Gunning PW, Ralph SA, Whitchurch CB, Sinden RE, Cowman AF, McFadden GI, Baum J. Spatial localisation of actin filaments across developmental stages of the malaria parasite. PLoS One 2012; 7:e32188. [PMID: 22389687 PMCID: PMC3289632 DOI: 10.1371/journal.pone.0032188] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2011] [Accepted: 01/23/2012] [Indexed: 02/02/2023] Open
Abstract
Actin dynamics have been implicated in a variety of developmental processes during the malaria parasite lifecycle. Parasite motility, in particular, is thought to critically depend on an actomyosin motor located in the outer pellicle of the parasite cell. Efforts to understand the diverse roles actin plays have, however, been hampered by an inability to detect microfilaments under native conditions. To visualise the spatial dynamics of actin we generated a parasite-specific actin antibody that shows preferential recognition of filamentous actin and applied this tool to different lifecycle stages (merozoites, sporozoites and ookinetes) of the human and mouse malaria parasite species Plasmodium falciparum and P. berghei along with tachyzoites from the related apicomplexan parasite Toxoplasma gondii. Actin filament distribution was found associated with three core compartments: the nuclear periphery, pellicular membranes of motile or invasive parasite forms and in a ring-like distribution at the tight junction during merozoite invasion of erythrocytes in both human and mouse malaria parasites. Localisation at the nuclear periphery is consistent with an emerging role of actin in facilitating parasite gene regulation. During invasion, we show that the actin ring at the parasite-host cell tight junction is dependent on dynamic filament turnover. Super-resolution imaging places this ring posterior to, and not concentric with, the junction marker rhoptry neck protein 4. This implies motor force relies on the engagement of dynamic microfilaments at zones of traction, though not necessarily directly through receptor-ligand interactions at sites of adhesion during invasion. Combined, these observations extend current understanding of the diverse roles actin plays in malaria parasite development and apicomplexan cell motility, in particular refining understanding on the linkage of the internal parasite gliding motor with the extra-cellular milieu.
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Affiliation(s)
- Fiona Angrisano
- The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia
- Department of Medical Biology, University of Melbourne, Parkville, Victoria, Australia
| | - David T. Riglar
- The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia
- Department of Medical Biology, University of Melbourne, Parkville, Victoria, Australia
| | - Angelika Sturm
- School of Botany University of Melbourne, Parkville, Victoria, Australia
| | - Jennifer C. Volz
- The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia
- Department of Medical Biology, University of Melbourne, Parkville, Victoria, Australia
| | - Michael J. Delves
- Department of Biological Sciences, Imperial College of Science, Technology and Medicine, London, United Kingdom
| | - Elizabeth S. Zuccala
- The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia
- Department of Medical Biology, University of Melbourne, Parkville, Victoria, Australia
| | - Lynne Turnbull
- The ithree Institute, University of Technology Sydney, Sydney, New South Wales, Australia
| | - Chaitali Dekiwadia
- Department of Biochemistry and Molecular Biology, Bio21 Molecular Science and Biotechnology Institute, University of Melbourne, Parkville, Victoria, Australia
| | - Maya A. Olshina
- The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia
- Department of Medical Biology, University of Melbourne, Parkville, Victoria, Australia
| | - Danushka S. Marapana
- The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia
| | - Wilson Wong
- The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia
| | - Vanessa Mollard
- Department of Biological Sciences, Imperial College of Science, Technology and Medicine, London, United Kingdom
| | - Clare H. Bradin
- The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia
| | - Christopher J. Tonkin
- The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia
- Department of Medical Biology, University of Melbourne, Parkville, Victoria, Australia
| | - Peter W. Gunning
- Department of Pharmacology, School of Medical Sciences, University of New South Wales, Sydney, New South Wales, Australia
| | - Stuart A. Ralph
- Department of Biochemistry and Molecular Biology, Bio21 Molecular Science and Biotechnology Institute, University of Melbourne, Parkville, Victoria, Australia
| | - Cynthia B. Whitchurch
- The ithree Institute, University of Technology Sydney, Sydney, New South Wales, Australia
| | - Robert E. Sinden
- School of Botany University of Melbourne, Parkville, Victoria, Australia
| | - Alan F. Cowman
- The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia
- Department of Medical Biology, University of Melbourne, Parkville, Victoria, Australia
| | - Geoffrey I. McFadden
- Department of Biological Sciences, Imperial College of Science, Technology and Medicine, London, United Kingdom
| | - Jake Baum
- The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia
- Department of Medical Biology, University of Melbourne, Parkville, Victoria, Australia
- * E-mail:
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Molecular characterization of Toxoplasma gondii formin 3, an actin nucleator dispensable for tachyzoite growth and motility. EUKARYOTIC CELL 2011; 11:343-52. [PMID: 22210829 DOI: 10.1128/ec.05192-11] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Toxoplasma gondii belongs to the phylum Apicomplexa, a group of obligate intracellular parasites that rely on gliding motility to enter host cells. Drugs interfering with the actin cytoskeleton block parasite motility, host cell invasion, and egress from infected cells. Myosin A, profilin, formin 1, formin 2, and actin-depolymerizing factor have all been implicated in parasite motility, yet little is known regarding the importance of actin polymerization and other myosins for the remaining steps of the parasite lytic cycle. Here we establish that T. gondii formin 3 (TgFRM3), a newly described formin homology 2 domain (FH2)-containing protein, binds to Toxoplasma actin and nucleates rabbit actin assembly in vitro. TgFRM3 expressed as a transgene exhibits a patchy localization at several distinct structures within the parasite. Disruption of the TgFRM3 gene by double homologous recombination in a ku80-ko strain reveals no vital function for tachyzoite propagation in vitro, which is consistent with its weak level of expression in this life stage. Conditional stabilization of truncated forms of TgFRM3 suggests that different regions of the molecule contribute to distinct localizations. Moreover, expression of TgFRM3 lacking the C-terminal domain severely affects parasite growth and replication. This work provides a first insight into how this specialized formin, restricted to the group of coccidia, completes its actin-nucleating activity.
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Evolutionarily divergent, unstable filamentous actin is essential for gliding motility in apicomplexan parasites. PLoS Pathog 2011; 7:e1002280. [PMID: 21998582 PMCID: PMC3188518 DOI: 10.1371/journal.ppat.1002280] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2011] [Accepted: 08/17/2011] [Indexed: 01/05/2023] Open
Abstract
Apicomplexan parasites rely on a novel form of actin-based motility called gliding, which depends on parasite actin polymerization, to migrate through their hosts and invade cells. However, parasite actins are divergent both in sequence and function and only form short, unstable filaments in contrast to the stability of conventional actin filaments. The molecular basis for parasite actin filament instability and its relationship to gliding motility remain unresolved. We demonstrate that recombinant Toxoplasma (TgACTI) and Plasmodium (PfACTI and PfACTII) actins polymerized into very short filaments in vitro but were induced to form long, stable filaments by addition of equimolar levels of phalloidin. Parasite actins contain a conserved phalloidin-binding site as determined by molecular modeling and computational docking, yet vary in several residues that are predicted to impact filament stability. In particular, two residues were identified that form intermolecular contacts between different protomers in conventional actin filaments and these residues showed non-conservative differences in apicomplexan parasites. Substitution of divergent residues found in TgACTI with those from mammalian actin resulted in formation of longer, more stable filaments in vitro. Expression of these stabilized actins in T. gondii increased sensitivity to the actin-stabilizing compound jasplakinolide and disrupted normal gliding motility in the absence of treatment. These results identify the molecular basis for short, dynamic filaments in apicomplexan parasites and demonstrate that inherent instability of parasite actin filaments is a critical adaptation for gliding motility.
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Nuclear actin-related protein is required for chromosome segregation in Toxoplasma gondii. Mol Biochem Parasitol 2011; 181:7-16. [PMID: 21963440 DOI: 10.1016/j.molbiopara.2011.09.006] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2011] [Revised: 09/10/2011] [Accepted: 09/15/2011] [Indexed: 12/30/2022]
Abstract
Apicomplexa parasites use complex cell cycles to replicate that are not well understood mechanistically. We have established a robust forward genetic strategy to identify the essential components of parasite cell division. Here we describe a novel temperature sensitive Toxoplasma strain, mutant 13-20C2, which growth arrests due to a defect in mitosis. The primary phenotype is the mis-segregation of duplicated chromosomes with chromosome loss during nuclear division. This defect is conditional-lethal with respect to temperature, although relatively mild in regard to the preservation of the major microtubule organizing centers. Despite severe DNA loss many of the physical structures associated with daughter budding and the assembly of invasion structures formed and operated normally at the non-permissive temperature before completely arresting. These results suggest there are coordinating mechanisms that govern the timing of these events in the parasite cell cycle. The defect in mutant 13-20C2 was mapped by genetic complementation to Toxoplasma chromosome III and to a specific mutation in the gene encoding an ortholog of nuclear actin-related protein 4. A change in a conserved isoleucine to threonine in the helical structure of this nuclear actin related protein leads to protein instability and cellular mis-localization at the higher temperature. Given the age of this protist family, the results indicate a key role for nuclear actin-related proteins in chromosome segregation was established very early in the evolution of eukaryotes.
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60
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Mesplet M, Palmer GH, Pedroni MJ, Echaide I, Florin-Christensen M, Schnittger L, Lau AOT. Genome-wide analysis of peptidase content and expression in a virulent and attenuated Babesia bovis strain pair. Mol Biochem Parasitol 2011; 179:111-3. [PMID: 21741414 PMCID: PMC3167272 DOI: 10.1016/j.molbiopara.2011.06.005] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2011] [Revised: 06/20/2011] [Accepted: 06/21/2011] [Indexed: 12/31/2022]
Abstract
Identifying virulence determinants in Apicomplexan parasites remains a major gap in knowledge for members within this phylum. We hypothesized that peptidases would segregate with virulence between a virulent parent Babesia bovis strain and an attenuated daughter strain derived by rapid in vivo passage. Using the complete genome sequence of the virulent T2Bo strain, 66 peptidases were identified and active sites confirmed. The presence, sequence identity and expression levels were tested for each of the 66 peptidases in the virulent parent and attenuated daughter T2Bo strains using whole genome, targeted sequencing approaches and microarrays analyses. Quantitative PCR revealed that there was no significant difference in peptidase expression between the virulent and attenuated strains. We conclude that while peptidases may well play a required role in B. bovis pathogenesis, neither loss of peptidase gene content nor reduced gene expression underlies the loss of virulence associated with in vivo passage and attenuation.
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Affiliation(s)
- Maria Mesplet
- Instituto de Patobiología, CICVyA, INTA-Castelar, Buenos Aires, Argentina
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61
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Besteiro S, Dubremetz JF, Lebrun M. The moving junction of apicomplexan parasites: a key structure for invasion. Cell Microbiol 2011; 13:797-805. [DOI: 10.1111/j.1462-5822.2011.01597.x] [Citation(s) in RCA: 224] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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62
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Olguin-Lamas A, Madec E, Hovasse A, Werkmeister E, Callebaut I, Slomianny C, Delhaye S, Mouveaux T, Schaeffer-Reiss C, Van Dorsselaer A, Tomavo S. A novel Toxoplasma gondii nuclear factor TgNF3 is a dynamic chromatin-associated component, modulator of nucleolar architecture and parasite virulence. PLoS Pathog 2011; 7:e1001328. [PMID: 21483487 PMCID: PMC3068996 DOI: 10.1371/journal.ppat.1001328] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2010] [Accepted: 03/01/2011] [Indexed: 01/13/2023] Open
Abstract
In Toxoplasma gondii, cis-acting elements present in promoter sequences of genes that are stage-specifically regulated have been described. However, the nuclear factors that bind to these cis-acting elements and regulate promoter activities have not been identified. In the present study, we performed affinity purification, followed by proteomic analysis, to identify nuclear factors that bind to a stage-specific promoter in T. gondii. This led to the identification of several nuclear factors in T. gondii including a novel factor, designated herein as TgNF3. The N-terminal domain of TgNF3 shares similarities with the N-terminus of yeast nuclear FK506-binding protein (FKBP), known as a histone chaperone regulating gene silencing. Using anti-TgNF3 antibodies, HA-FLAG and YFP-tagged TgNF3, we show that TgNF3 is predominantly a parasite nucleolar, chromatin-associated protein that binds specifically to T. gondii gene promoters in vivo. Genome-wide analysis using chromatin immunoprecipitation followed by high-throughput sequencing (ChIP-seq) identified promoter occupancies by TgNF3. In addition, TgNF3 has a direct role in transcriptional control of genes involved in parasite metabolism, transcription and translation. The ectopic expression of TgNF3 in the tachyzoites revealed dynamic changes in the size of the nucleolus, leading to a severe attenuation of virulence in vivo. We demonstrate that TgNF3 physically interacts with H3, H4 and H2A/H2B assembled into bona fide core and nucleosome-associated histones. Furthermore, TgNF3 interacts specifically to histones in the context of stage-specific gene silencing of a promoter that lacks active epigenetic acetylated histone marks. In contrast to virulent tachyzoites, which express the majority of TgNF3 in the nucleolus, the protein is exclusively located in the cytoplasm of the avirulent bradyzoites. We propose a model where TgNF3 acts essentially to coordinate nucleolus and nuclear functions by modulating nucleosome activities during the intracellular proliferation of the virulent tachyzoites of T. gondii. Apicomplexa including Toxoplasma gondii are responsible for a variety of deadly infections. These intracellular parasites have complex life cycles within different hosts and their infectivity relies on their capacity to regulate gene expression in response to different environments. However, to date, little is known about nuclear factors that regulate their gene expression. Here, we have characterized parasite nuclear factors that bind to a stage-specific promoter. We identified several nuclear factors including a novel factor, designated herein as TgNF3. The N-terminal domain of TgNF3 shares similarities with the N-terminus of yeast nuclear FK506-binding protein (FKBP), known as a histone chaperone regulating gene silencing. We show that TgNF3 is predominantly a nucleolar, chromatin-associated protein that specifically binds to T. gondii nucleosome-associated histones and promoters. Genome-wide analysis identified promoter occupancies by TgNF3 and we demonstrated a direct role for this factor in transcriptional control of genes involved in parasite metabolism, transcription and translation. Ectopic expression of TgNF3 induces dynamic changes in the size of the nucleolus, and a severe attenuation of parasite virulence in vivo. In avirulent bradyzoites, TgNF3 is found exclusively in the cytoplasm, suggesting a potential role in regulating nucleolar and nuclear functions in the virulent tachyzoites of T. gondii.
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Affiliation(s)
- Alejandro Olguin-Lamas
- Center for Infection and Immunity of Lille, CNRS UMR 8204, INSERM U 1019, Institut Pasteur de Lille, Université Lille Nord de France, Lille, France
- Centre National de la Recherche Scientifique, CNRS UMR 8576, UGSF, Université de Lille 1, Villeneuve d'Ascq, France
| | - Edwige Madec
- Centre National de la Recherche Scientifique, CNRS UMR 8576, UGSF, Université de Lille 1, Villeneuve d'Ascq, France
| | - Agnes Hovasse
- Laboratoire de Spectrométrie de Masse Bioorganique, IPHC, CNRS UMR 7178, Université de Strasbourg, Strasbourg, France
| | - Elisabeth Werkmeister
- Center for Infection and Immunity of Lille, CNRS UMR 8204, INSERM U 1019, Institut Pasteur de Lille, Université Lille Nord de France, Lille, France
| | - Isabelle Callebaut
- Centre National de la Recherche Scientifique, Universités Pierre et Marie Curie-Paris 6 et Denis Diderot-Paris 7, UMR7590, Paris, France
| | - Christian Slomianny
- Laboratoire de Physiologie Cellulaire, INSERM U1003, Université de Lille 1, Villeneuve d'Ascq, France
| | - Stephane Delhaye
- Center for Infection and Immunity of Lille, CNRS UMR 8204, INSERM U 1019, Institut Pasteur de Lille, Université Lille Nord de France, Lille, France
- Centre National de la Recherche Scientifique, CNRS UMR 8576, UGSF, Université de Lille 1, Villeneuve d'Ascq, France
| | - Thomas Mouveaux
- Center for Infection and Immunity of Lille, CNRS UMR 8204, INSERM U 1019, Institut Pasteur de Lille, Université Lille Nord de France, Lille, France
- Centre National de la Recherche Scientifique, CNRS UMR 8576, UGSF, Université de Lille 1, Villeneuve d'Ascq, France
| | - Christine Schaeffer-Reiss
- Laboratoire de Spectrométrie de Masse Bioorganique, IPHC, CNRS UMR 7178, Université de Strasbourg, Strasbourg, France
| | - Alain Van Dorsselaer
- Laboratoire de Spectrométrie de Masse Bioorganique, IPHC, CNRS UMR 7178, Université de Strasbourg, Strasbourg, France
| | - Stanislas Tomavo
- Center for Infection and Immunity of Lille, CNRS UMR 8204, INSERM U 1019, Institut Pasteur de Lille, Université Lille Nord de France, Lille, France
- Centre National de la Recherche Scientifique, CNRS UMR 8576, UGSF, Université de Lille 1, Villeneuve d'Ascq, France
- * E-mail:
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63
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Mehta S, Sibley LD. Actin depolymerizing factor controls actin turnover and gliding motility in Toxoplasma gondii. Mol Biol Cell 2011; 22:1290-9. [PMID: 21346192 PMCID: PMC3078074 DOI: 10.1091/mbc.e10-12-0939] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Actin-based motility is vital for host cell invasion by protozoan parasites such as Toxoplasma, which provides a model for studying actin-based motility in parasites. Our study reveals that, in addition to intrinsic differences in actin dynamics, regulatory proteins like actin depolymerizing factor are required to regulate this process in vivo. Apicomplexan parasites rely on actin-based gliding motility to move across the substratum, cross biological barriers, and invade their host cells. Gliding motility depends on polymerization of parasite actin filaments, yet ∼98% of actin is nonfilamentous in resting parasites. Previous studies suggest that the lack of actin filaments in the parasite is due to inherent instability, leaving uncertain the role of actin-binding proteins in controlling dynamics. We have previously shown that the single allele of Toxoplasma gondii actin depolymerizing factor (TgADF) has strong actin monomer–sequestering and weak filament-severing activities in vitro. Here we used a conditional knockout strategy to investigate the role of TgADF in vivo. Suppression of TgADF led to accumulation of actin-rich filaments that were detected by immunofluorescence and electron microscopy. Parasites deficient in TgADF showed reduced speed of motility, increased aberrant patterns of motion, and inhibition of sustained helical gliding. Lack of TgADF also led to severe defects in entry and egress from host cells, thus blocking infection in vitro. These studies establish that the absence of stable actin structures in the parasite are not simply the result of intrinsic instability, but that TgADF is required for the rapid turnover of parasite actin filaments, gliding motility, and cell invasion.
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Affiliation(s)
- Simren Mehta
- Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, MO 63110, USA
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