1
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Baptista CG, Hosking S, Gas-Pascual E, Ciampossine L, Abel S, Hakimi MA, Jeffers V, Le Roch K, West CM, Blader IJ. The Toxoplasma gondii F-Box Protein L2 Functions as a Repressor of Stage Specific Gene Expression. PLoS Pathog 2024; 20:e1012269. [PMID: 38814984 PMCID: PMC11166348 DOI: 10.1371/journal.ppat.1012269] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2023] [Revised: 06/11/2024] [Accepted: 05/17/2024] [Indexed: 06/01/2024] Open
Abstract
Toxoplasma gondii is a foodborne pathogen that can cause severe and life-threatening infections in fetuses and immunocompromised patients. Felids are its only definitive hosts, and a wide range of animals, including humans, serve as intermediate hosts. When the transmissible bradyzoite stage is orally ingested by felids, they transform into merozoites that expand asexually, ultimately generating millions of gametes for the parasite sexual cycle. However, bradyzoites in intermediate hosts differentiate exclusively to disease-causing tachyzoites, which rapidly disseminate throughout the host. Though tachyzoites are well-studied, the molecular mechanisms governing transitioning between developmental stages are poorly understood. Each parasite stage can be distinguished by a characteristic transcriptional signature, with one signature being repressed during the other stages. Switching between stages require substantial changes in the proteome, which is achieved in part by ubiquitination. F-box proteins mediate protein poly-ubiquitination by recruiting substrates to SKP1, Cullin-1, F-Box protein E3 ubiquitin ligase (SCF-E3) complexes. We have identified an F-box protein named Toxoplasma gondii F-Box Protein L2 (TgFBXL2), which localizes to distinct perinucleolar sites. TgFBXL2 is stably engaged in an SCF-E3 complex that is surprisingly also associated with a COP9 signalosome complex that negatively regulates SCF-E3 function. At the cellular level, TgFBXL2-depleted parasites are severely defective in centrosome replication and daughter cell development. Most remarkable, RNAseq data show that TgFBXL2 conditional depletion induces the expression of stage-specific genes including a large cohort of genes necessary for sexual commitment. Together, these data suggest that TgFBXL2 is a latent guardian of stage specific gene expression in Toxoplasma and poised to remove conflicting proteins in response to an unknown trigger of development.
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Affiliation(s)
- Carlos G. Baptista
- Department of Microbiology and Immunology, University at Buffalo School of Medicine, Buffalo, New York, United States of America
| | - Sarah Hosking
- Department of Microbiology and Immunology, University at Buffalo School of Medicine, Buffalo, New York, United States of America
| | - Elisabet Gas-Pascual
- Department of Biochemistry & Molecular Biology, Center for Tropical & Emerging Global Diseases, University of Georgia, Athens, Georgia United States of America
| | - Loic Ciampossine
- Department of Molecular, Cell, and Systems Biology, University of California Riverside, Riverside, California, United States of America
| | - Steven Abel
- Department of Molecular, Cell, and Systems Biology, University of California Riverside, Riverside, California, United States of America
| | - Mohamed-Ali Hakimi
- Host-Pathogen Interactions and Immunity to Infection, Institute for Advanced Biosciences (IAB), INSERM U1209, CNRS UMR 5309, Grenoble Alpes University, Grenoble, France
| | - Victoria Jeffers
- Department of Molecular, Cellular and Biomedical Sciences, University of New Hampshire, Durham, New Hampshire, United States of America
| | - Karine Le Roch
- Department of Molecular, Cell, and Systems Biology, University of California Riverside, Riverside, California, United States of America
| | - Christopher M. West
- Department of Biochemistry & Molecular Biology, Center for Tropical & Emerging Global Diseases, University of Georgia, Athens, Georgia United States of America
| | - Ira J. Blader
- Department of Microbiology and Immunology, University at Buffalo School of Medicine, Buffalo, New York, United States of America
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2
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Marsilia C, Batra M, Pokrovskaya ID, Wang C, Chaput D, Naumova DA, Lupashin VV, Suvorova ES. Essential role of the conserved oligomeric Golgi complex in Toxoplasma gondii. mBio 2023; 14:e0251323. [PMID: 37966241 PMCID: PMC10746232 DOI: 10.1128/mbio.02513-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2023] [Accepted: 10/05/2023] [Indexed: 11/16/2023] Open
Abstract
IMPORTANCE The Golgi is an essential eukaryotic organelle and a major place for protein sorting and glycosylation. Among apicomplexan parasites, Toxoplasma gondii retains the most developed Golgi structure and produces many glycosylated factors necessary for parasite survival. Despite its importance, Golgi function received little attention in the past. In the current study, we identified and characterized the conserved oligomeric Golgi complex and its novel partners critical for protein transport in T. gondii tachyzoites. Our results suggest that T. gondii broadened the role of the conserved elements and reinvented the missing components of the trafficking machinery to accommodate the specific needs of the opportunistic parasite T. gondii.
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Affiliation(s)
- Clem Marsilia
- Division of Infectious Diseases, Department of Internal Medicine, Morsani College of Medicine, University of South Florida, Tampa, Florida, USA
| | - Mrinalini Batra
- Division of Infectious Diseases, Department of Internal Medicine, Morsani College of Medicine, University of South Florida, Tampa, Florida, USA
| | - Irina D. Pokrovskaya
- Department of Physiology and Cell Biology, College of Medicine, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA
| | - Changqi Wang
- College of Public Health, University of South Florida, Tampa, Florida, USA
| | - Dale Chaput
- Proteomics Core, College of Arts and Sciences, University of South Florida, Tampa, Florida, USA
| | - Daria A. Naumova
- Division of Infectious Diseases, Department of Internal Medicine, Morsani College of Medicine, University of South Florida, Tampa, Florida, USA
| | - Vladimir V. Lupashin
- Department of Physiology and Cell Biology, College of Medicine, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA
| | - Elena S. Suvorova
- Division of Infectious Diseases, Department of Internal Medicine, Morsani College of Medicine, University of South Florida, Tampa, Florida, USA
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3
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Baptista CG, Hosking S, Gas-Pascual E, Ciampossine L, Abel S, Hakimi MA, Jeffers V, Le Roch K, West CM, Blader IJ. Toxoplasma gondii F-Box Protein L2 Silences Feline-Restricted Genes Necessary for Sexual Commitment. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.12.18.572150. [PMID: 38187549 PMCID: PMC10769283 DOI: 10.1101/2023.12.18.572150] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/09/2024]
Abstract
Toxoplasma gondii is a foodborne pathogen that can cause severe and life-threatening infections in fetuses and immunocompromised patients. Felids are its only definitive hosts, and a wide range of animals, including humans, serve as intermediate hosts. When the transmissible bradyzoite stage is orally ingested by felids, they transform into merozoites that expand asexually, ultimately generating millions of gametes for the parasite sexual cycle. However, bradyzoites in intermediate hosts differentiate exclusively to disease-causing tachyzoites, which rapidly disseminate throughout the host. Though tachyzoites are well-studied, the molecular mechanisms governing transitioning between developmental stages are poorly understood. Each parasite stage can be distinguished by a characteristic transcriptional signature, with one signature being repressed during the other stages. Switching between stages requires substantial changes in the proteome, which is achieved in part by ubiquitination. F-box proteins mediate protein poly-ubiquitination by recruiting substrates to SKP1, Cullin-1, F-Box protein E3 ubiquitin ligase (SCF-E3) complexes. We have identified an F-box protein named Toxoplasma gondii F-Box Protein L2 (TgFBXL2), which localizes to distinct nuclear sites. TgFBXL2 is stably engaged in an SCF-E3 complex that is surprisingly also associated with a COP9 signalosome complex that negatively regulates SCF-E3 function. At the cellular level, TgFBXL2-depleted parasites are severely defective in centrosome replication and daughter cell development. Most remarkable, RNA seq data show that TgFBXL2 conditional depletion induces the expression of genes necessary for sexual commitment. We suggest that TgFBXL2 is a latent guardian of sexual stage development in Toxoplasma and poised to remove conflicting proteins in response to an unknown trigger of sexual development.
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Affiliation(s)
- Carlos G. Baptista
- Department of Microbiology and Immunology, University at Buffalo School of Medicine, Buffalo, NY 14203 USA
| | - Sarah Hosking
- Department of Microbiology and Immunology, University at Buffalo School of Medicine, Buffalo, NY 14203 USA
| | - Elisabet Gas-Pascual
- Department of Biochemistry & Molecular Biology, Center for Tropical & Emerging Global Diseases, University of Georgia, Athens, GA 30602 USA
| | - Loic Ciampossine
- Department of Molecular, Cell, and Systems Biology, University of California Riverside, Riverside, CA, 92521USA
| | - Steven Abel
- Department of Molecular, Cell, and Systems Biology, University of California Riverside, Riverside, CA, 92521USA
| | - Mohamed-Ali Hakimi
- Host-Pathogen Interactions and Immunity to Infection, Institute for Advanced Biosciences (IAB), INSERM U1209, CNRS UMR 5309, Grenoble Alpes University, Grenoble, France
| | - Victoria Jeffers
- Department of Molecular, Cellular and Biomedical Sciences, University of New Hampshire, Durham, NH 03824 USA
| | - Karine Le Roch
- Department of Molecular, Cell, and Systems Biology, University of California Riverside, Riverside, CA, 92521USA
| | - Christopher M. West
- Department of Biochemistry & Molecular Biology, Center for Tropical & Emerging Global Diseases, University of Georgia, Athens, GA 30602 USA
| | - Ira J. Blader
- Department of Microbiology and Immunology, University at Buffalo School of Medicine, Buffalo, NY 14203 USA
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4
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Liang QL, Nie LB, Elsheikha HM, Li TT, Sun LX, Zhang ZW, Wang M, Fu BQ, Zhu XQ, Wang JL. The Toxoplasma protein phosphatase 6 catalytic subunit (TgPP6C) is essential for cell cycle progression and virulence. PLoS Pathog 2023; 19:e1011831. [PMID: 38091362 PMCID: PMC10752510 DOI: 10.1371/journal.ppat.1011831] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2023] [Revised: 12/27/2023] [Accepted: 11/16/2023] [Indexed: 12/28/2023] Open
Abstract
Protein phosphatases are post-translational regulators of Toxoplasma gondii proliferation, tachyzoite-bradyzoite differentiation and pathogenesis. Here, we identify the putative protein phosphatase 6 (TgPP6) subunits of T. gondii and elucidate their role in the parasite lytic cycle. The putative catalytic subunit TgPP6C and regulatory subunit TgPP6R likely form a complex whereas the predicted structural subunit TgPP6S, with low homology to the human PP6 structural subunit, does not coassemble with TgPP6C and TgPP6R. Functional studies showed that TgPP6C and TgPP6R are essential for parasite growth and replication. The ablation of TgPP6C significantly reduced the synchronous division of the parasite's daughter cells during endodyogeny, resulting in disordered rosettes. Moreover, the six conserved motifs of TgPP6C were required for efficient endodyogeny. Phosphoproteomic analysis revealed that ablation of TgPP6C predominately altered the phosphorylation status of proteins involved in the regulation of the parasite cell cycle. Deletion of TgPP6C significantly attenuated the parasite virulence in mice. Immunization of mice with TgPP6C-deficient type I RH strain induced protective immunity against challenge with a lethal dose of RH or PYS tachyzoites and Pru cysts. Taken together, the results show that TgPP6C contributes to the cell division, replication and pathogenicity in T. gondii.
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Affiliation(s)
- Qin-Li Liang
- State Key Laboratory for Animal Disease Control and Prevention, Key Laboratory of Veterinary Parasitology of Gansu Province, Lanzhou Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Lanzhou, China
| | - Lan-Bi Nie
- State Key Laboratory for Animal Disease Control and Prevention, Key Laboratory of Veterinary Parasitology of Gansu Province, Lanzhou Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Lanzhou, China
| | - Hany M. Elsheikha
- Faculty of Medicine and Health Sciences, School of Veterinary Medicine and Science, University of Nottingham, Loughborough, United Kingdom
| | - Ting-Ting Li
- State Key Laboratory for Animal Disease Control and Prevention, Key Laboratory of Veterinary Parasitology of Gansu Province, Lanzhou Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Lanzhou, China
- Institute of Urban Agriculture, Chinese Academy of Agricultural Sciences, Chengdu, China
| | - Li-Xiu Sun
- State Key Laboratory for Animal Disease Control and Prevention, Key Laboratory of Veterinary Parasitology of Gansu Province, Lanzhou Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Lanzhou, China
| | - Zhi-Wei Zhang
- State Key Laboratory for Animal Disease Control and Prevention, Key Laboratory of Veterinary Parasitology of Gansu Province, Lanzhou Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Lanzhou, China
| | - Meng Wang
- State Key Laboratory for Animal Disease Control and Prevention, Key Laboratory of Veterinary Parasitology of Gansu Province, Lanzhou Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Lanzhou, China
- Institute of Urban Agriculture, Chinese Academy of Agricultural Sciences, Chengdu, China
| | - Bao-Quan Fu
- State Key Laboratory for Animal Disease Control and Prevention, Key Laboratory of Veterinary Parasitology of Gansu Province, Lanzhou Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Lanzhou, China
- Institute of Urban Agriculture, Chinese Academy of Agricultural Sciences, Chengdu, China
| | - Xing-Quan Zhu
- Laboratory of Parasitic Diseases, College of Veterinary Medicine, Shanxi Agricultural University, Taigu, China
| | - Jin-Lei Wang
- State Key Laboratory for Animal Disease Control and Prevention, Key Laboratory of Veterinary Parasitology of Gansu Province, Lanzhou Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Lanzhou, China
- Institute of Urban Agriculture, Chinese Academy of Agricultural Sciences, Chengdu, China
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Devarakonda PM, Sarmiento V, Heaslip AT. F-actin and myosin F control apicoplast elongation dynamics which drive apicoplast-centrosome association in Toxoplasma gondii. mBio 2023; 14:e0164023. [PMID: 37732764 PMCID: PMC10653800 DOI: 10.1128/mbio.01640-23] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2023] [Accepted: 07/26/2023] [Indexed: 09/22/2023] Open
Abstract
IMPORTANCE Toxoplasma gondii and most other parasites in the phylum Apicomplexa contain an apicoplast, a non-photosynthetic plastid organelle required for fatty acid, isoprenoid, iron-sulfur cluster, and heme synthesis. Perturbation of apicoplast function results in parasite death. Thus, parasite survival critically depends on two cellular processes: apicoplast division to ensure every daughter parasite inherits a single apicoplast, and trafficking of nuclear encoded proteins to the apicoplast. Despite the importance of these processes, there are significant knowledge gaps in regards to the molecular mechanisms which control these processes; this is particularly true for trafficking of nuclear-encoded apicoplast proteins. This study provides crucial new insight into the timing of apicoplast protein synthesis and trafficking to the apicoplast. In addition, this study demonstrates how apicoplast-centrosome association, a key step in the apicoplast division cycle, is controlled by the actomyosin cytoskeleton.
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Affiliation(s)
| | - Valeria Sarmiento
- Department of Molecular and Cell Biology, University of Connecticut, Storrs, Connecticut, USA
| | - Aoife T. Heaslip
- Department of Molecular and Cell Biology, University of Connecticut, Storrs, Connecticut, USA
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6
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Devarakonda PM, Sarmiento V, Heaslip AT. F-actin and Myosin F control apicoplast elongation dynamics which drive apicoplast-centrosome association in Toxoplasma gondii. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.01.01.521342. [PMID: 36711828 PMCID: PMC9881852 DOI: 10.1101/2023.01.01.521342] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Toxoplasma gondii contains an essential plastid organelle called the apicoplast that is necessary for fatty acid, isoprenoid, and heme synthesis. Perturbations affecting apicoplast function or inheritance lead to parasite death. The apicoplast is a single copy organelle and therefore must be divided so that each daughter parasite inherits an apicoplast during cell division. In this study we identify new roles for F-actin and an unconventional myosin motor, TgMyoF, in this process. First, loss of TgMyoF and actin lead to an accumulation of apicoplast vesicles in the cytosol indicating a role for this actomyosin system in apicoplast protein trafficking or morphological integrity of the organelle. Second, live cell imaging reveals that during division the apicoplast is highly dynamic, exhibiting branched, U-shaped and linear morphologies that are dependent on TgMyoF and actin. In parasites where movement was inhibited by the depletion of TgMyoF, the apicoplast fails to associate with the parasite centrosomes. Thus, this study provides crucial new insight into mechanisms controlling apicoplast-centrosome association, a vital step in the apicoplast division cycle, which ensures that each daughter inherits a single apicoplast.
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Separate To Operate: the Centriole-Free Inner Core of the Centrosome Regulates the Assembly of the Intranuclear Spindle in Toxoplasma gondii. mBio 2022; 13:e0185922. [PMID: 36069445 PMCID: PMC9600614 DOI: 10.1128/mbio.01859-22] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Centrosomes are the main microtubule-organizing center of the cell. They are normally formed by two centrioles, embedded in a cloud of proteins known as pericentriolar material (PCM). The PCM ascribes centrioles with their microtubule nucleation capacity. Toxoplasma gondii, the causative agent of toxoplasmosis, divides by endodyogeny. Successful cell division is critical for pathogenesis. The centrosome, one of the microtubule organizing centers of the cell, plays central roles in orchestrating the temporal and physical coordination of major organelle segregation and daughter cell formation during endodyogeny. The Toxoplasma centrosome is constituted by multiple domains: an outer core, distal from the nucleus; a middle core; and an inner core, proximal to the nucleus. This modular organization has been proposed to underlie T. gondii's cell division plasticity. However, the role of the inner core remains undeciphered. Here, we focus on understanding the function of the inner core by finely studying the localization and role of its only known molecular marker; TgCep250L1. We show that upon conditional degradation of TgCep250L1 parasites are unable to survive. Mutants exhibit severe nuclear segregation defects. In addition, the rest of the centrosome, defined by the position of the centrioles, disconnects from the nucleus. We explore the structural defects underlying these phenotypes by ultrastructure expansion microscopy. We show that TgCep250L1's location changes with respect to other markers, and these changes encompass the formation of the mitotic spindle. Moreover, we show that in the absence of TgCep250L1, the microtubule binding protein TgEB1, fails to localize at the mitotic spindle, while unsegregated nuclei accumulate at the residual body. Overall, our data support a model in which the inner core of the T. gondii centrosome critically participates in cell division by directly impacting the formation or stability of the mitotic spindle. IMPORTANCE Toxoplasma gondii parasites cause toxoplasmosis, arguably the most widespread and prevalent parasitosis of humans and animals. During the clinically relevant stage of its life cycle, the parasites divide by endodyogeny. In this mode of division, the nucleus, containing loosely packed chromatin and a virtually intact nuclear envelope, parcels into two daughter cells generated within a common mother cell cytoplasm. The centrosome is a microtubule-organizing center critical for orchestrating the multiple simultaneously occurring events of endodyogeny. It is organized in two distinct domains: the outer and inner cores. We demonstrate here that the inner core protein TgCEP250L1 is required for replication of T. gondii. Lack of TgCEP250L1 renders parasites able to form daughter cells, while unable to segregate their nuclei. We determine that, in the absence of TgCEP250L1, the mitotic spindle, which is responsible for karyokinesis, does not assemble. Our results support a role for the inner core in nucleation or stabilization of the mitotic spindle in T. gondii.
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Abstract
Apicomplexan parasites, such as Toxoplasma gondii and Plasmodium falciparum, are the cause of many important human and animal diseases. While T. gondii tachyzoites replicate through endodyogeny, during which two daughter cells are formed within the parental cell, P. falciparum replicates through schizogony, where up to 32 parasites are formed in a single infected red blood cell and even thousands of daughter cells during mosquito- or liver-stage development. These processes require a tightly orchestrated division and distribution over the daughter parasites of one-per-cell organelles such as the mitochondrion and apicoplast. Although proper organelle segregation is highly essential, the molecular mechanism and the key proteins involved remain largely unknown. In this review, we describe organelle dynamics during cell division in T. gondii and P. falciparum, summarize the current understanding of the molecular mechanisms underlying organelle fission in these parasites, and introduce candidate fission proteins.
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Gubbels MJ, Coppens I, Zarringhalam K, Duraisingh MT, Engelberg K. The Modular Circuitry of Apicomplexan Cell Division Plasticity. Front Cell Infect Microbiol 2021; 11:670049. [PMID: 33912479 PMCID: PMC8072463 DOI: 10.3389/fcimb.2021.670049] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2021] [Accepted: 03/22/2021] [Indexed: 12/31/2022] Open
Abstract
The close-knit group of apicomplexan parasites displays a wide variety of cell division modes, which differ between parasites as well as between different life stages within a single parasite species. The beginning and endpoint of the asexual replication cycles is a 'zoite' harboring the defining apical organelles required for host cell invasion. However, the number of zoites produced per division round varies dramatically and can unfold in several different ways. This plasticity of the cell division cycle originates from a combination of hard-wired developmental programs modulated by environmental triggers. Although the environmental triggers and sensors differ between species and developmental stages, widely conserved secondary messengers mediate the signal transduction pathways. These environmental and genetic input integrate in division-mode specific chromosome organization and chromatin modifications that set the stage for each division mode. Cell cycle progression is conveyed by a smorgasbord of positively and negatively acting transcription factors, often acting in concert with epigenetic reader complexes, that can vary dramatically between species as well as division modes. A unique set of cell cycle regulators with spatially distinct localization patterns insert discrete check points which permit individual control and can uncouple general cell cycle progression from nuclear amplification. Clusters of expressed genes are grouped into four functional modules seen in all division modes: 1. mother cytoskeleton disassembly; 2. DNA replication and segregation (D&S); 3. karyokinesis; 4. zoite assembly. A plug-and-play strategy results in the variety of extant division modes. The timing of mother cytoskeleton disassembly is hard-wired at the species level for asexual division modes: it is either the first step, or it is the last step. In the former scenario zoite assembly occurs at the plasma membrane (external budding), and in the latter scenario zoites are assembled in the cytoplasm (internal budding). The number of times each other module is repeated can vary regardless of this first decision, and defines the modes of cell division: schizogony, binary fission, endodyogeny, endopolygeny.
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Affiliation(s)
- Marc-Jan Gubbels
- Department of Biology, Boston College, Chestnut Hill, MA, United States
| | - Isabelle Coppens
- Department of Molecular Microbiology and Immunology, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD, United States
| | - Kourosh Zarringhalam
- Department of Mathematics, University of Massachusetts Boston, Boston, MA, United States
| | - Manoj T. Duraisingh
- Department of Immunology and Infectious Diseases, Harvard T. H. Chan School of Public Health, Boston, MA, United States
| | - Klemens Engelberg
- Department of Biology, Boston College, Chestnut Hill, MA, United States
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10
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Martins-Duarte ÉS, Sheiner L, Reiff SB, de Souza W, Striepen B. Replication and partitioning of the apicoplast genome of Toxoplasma gondii is linked to the cell cycle and requires DNA polymerase and gyrase. Int J Parasitol 2021; 51:493-504. [PMID: 33581138 PMCID: PMC8113025 DOI: 10.1016/j.ijpara.2020.11.004] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2020] [Revised: 10/30/2020] [Accepted: 11/08/2020] [Indexed: 10/26/2022]
Abstract
Apicomplexans are the causative agents of numerous important infectious diseases including malaria and toxoplasmosis. Most of them harbour a chloroplast-like organelle called the apicoplast that is essential for the parasites' metabolism and survival. While most apicoplast proteins are nuclear encoded, the organelle also maintains its own genome, a 35 kb circle. In this study we used Toxoplasma gondii to identify and characterise essential proteins involved in apicoplast genome replication and to understand how apicoplast genome segregation unfolds over time. We demonstrated that the DNA replication enzymes Prex, DNA gyrase and DNA single stranded binding protein localise to the apicoplast. We show in knockdown experiments that apicoplast DNA Gyrase A and B, and Prex are required for apicoplast genome replication and growth of the parasite. Analysis of apicoplast genome replication by structured illumination microscopy in T. gondii tachyzoites showed that apicoplast nucleoid division and segregation initiate at the beginning of S phase and conclude during mitosis. Thus, the replication and division of the apicoplast nucleoid is highly coordinated with nuclear genome replication and mitosis. Our observations highlight essential components of apicoplast genome maintenance and shed light on the timing of this process in the context of the overall parasite cell cycle.
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Affiliation(s)
- Érica S Martins-Duarte
- Laboratório de Quimioterapia de Protozoários Egler Chiari, Departamento de Parasitologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil; Núcleo de Biologia Estrutural e Bioimagens (CENABIO) - Instituto Nacional de Ciência e Tecnologia em Biologia Estrutural e Biomagens (INBEB), Rio de Janeiro, RJ, Brazil.
| | - Lilach Sheiner
- Wellcome Centre for Integrative Parasitology, University of Glasgow, 120 University Place Glasgow, United Kingdom
| | - Sarah B Reiff
- Department of Cellular Biology, University of Georgia, Athens, GA, USA
| | - Wanderley de Souza
- Núcleo de Biologia Estrutural e Bioimagens (CENABIO) - Instituto Nacional de Ciência e Tecnologia em Biologia Estrutural e Biomagens (INBEB), Rio de Janeiro, RJ, Brazil; Laboratório de Ultraestrutura Celular Hertha Meyer, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, Brazil
| | - Boris Striepen
- Department of Cellular Biology, University of Georgia, Athens, GA, USA; Department of Pathobiology, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, PA. USA
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11
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Carmeille R, Schiano Lomoriello P, Devarakonda PM, Kellermeier JA, Heaslip AT. Actin and an unconventional myosin motor, TgMyoF, control the organization and dynamics of the endomembrane network in Toxoplasma gondii. PLoS Pathog 2021; 17:e1008787. [PMID: 33529198 PMCID: PMC7880465 DOI: 10.1371/journal.ppat.1008787] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2020] [Revised: 02/12/2021] [Accepted: 01/07/2021] [Indexed: 12/25/2022] Open
Abstract
Toxoplasma gondii is an obligate intracellular parasite that relies on three distinct secretory organelles, the micronemes, rhoptries, and dense granules, for parasite survival and disease pathogenesis. Secretory proteins destined for these organelles are synthesized in the endoplasmic reticulum (ER) and sequentially trafficked through a highly polarized endomembrane network that consists of the Golgi and multiple post-Golgi compartments. Currently, little is known about how the parasite cytoskeleton controls the positioning of the organelles in this pathway, or how vesicular cargo is trafficked between organelles. Here we show that F-actin and an unconventional myosin motor, TgMyoF, control the dynamics and organization of the organelles in the secretory pathway, specifically ER tubule movement, apical positioning of the Golgi and post-Golgi compartments, apical positioning of the rhoptries, and finally, the directed transport of Rab6-positive and Rop1-positive vesicles. Thus, this study identifies TgMyoF and actin as the key cytoskeletal components that organize the endomembrane system in T. gondii. Endomembrane trafficking is a vital cellular process in all eukaryotic cells. In most cases the molecular motors myosin, kinesin, and dynein transport cargo including vesicles, organelles and transcripts along actin and microtubule filaments in a manner analogous to a train moving on its tracks. For the unicellular eukaryote Toxoplasma gondii, the accurate trafficking of proteins through the endomembrane system is vital for parasite survival and pathogenicity. However, the mechanisms of cargo transport in this parasite are poorly understood. In this study, we fluorescently labeled multiple endomembrane organelles and imaged their movements using live cell microscopy. We demonstrate that filamentous actin and an unconventional myosin motor named TgMyoF control both the positioning of organelles in this pathway and the movement of transport vesicles throughout the parasite cytosol. This data provides new insight into the mechanisms of cargo transport in this important pathogen and expands our understanding of the biological roles of actin in the intracellular phase of the parasite’s growth cycle.
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Affiliation(s)
- Romain Carmeille
- Department of Cell and Molecular Biology, University of Connecticut, Storrs, Connecticut, United States of America
| | - Porfirio Schiano Lomoriello
- Department of Cell and Molecular Biology, University of Connecticut, Storrs, Connecticut, United States of America
| | - Parvathi M. Devarakonda
- Department of Cell and Molecular Biology, University of Connecticut, Storrs, Connecticut, United States of America
| | - Jacob A. Kellermeier
- Department of Cell and Molecular Biology, University of Connecticut, Storrs, Connecticut, United States of America
| | - Aoife T. Heaslip
- Department of Cell and Molecular Biology, University of Connecticut, Storrs, Connecticut, United States of America
- * E-mail:
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12
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Abstract
Mitogen-activated protein kinases (MAPKs) are a conserved family of protein kinases that regulate signal transduction, proliferation, and development throughout eukaryotes. The apicomplexan parasite Toxoplasma gondii expresses three MAPKs. Two of these, extracellular signal-regulated kinase 7 (ERK7) and MAPKL1, have been implicated in the regulation of conoid biogenesis and centrosome duplication, respectively. The third kinase, MAPK2, is specific to and conserved throughout the Alveolata, although its function is unknown. We used the auxin-inducible degron system to determine phenotypes associated with MAPK2 loss of function in Toxoplasma We observed that parasites lacking MAPK2 failed to duplicate their centrosomes and therefore did not initiate daughter cell budding, which ultimately led to parasite death. MAPK2-deficient parasites initiated but did not complete DNA replication and arrested prior to mitosis. Surprisingly, the parasites continued to grow and replicate their Golgi apparatus, mitochondria, and apicoplasts. We found that the failure in centrosome duplication is distinct from the phenotype caused by the depletion of MAPKL1. As we did not observe MAPK2 localization at the centrosome at any point in the cell cycle, our data suggest that MAPK2 regulates a process at a distal site that is required for the completion of centrosome duplication and the initiation of parasite mitosis.IMPORTANCE Toxoplasma gondii is a ubiquitous intracellular protozoan parasite that can cause severe and fatal disease in immunocompromised patients and the developing fetus. Rapid parasite replication is critical for establishing a productive infection. Here, we demonstrate that a Toxoplasma protein kinase called MAPK2 is conserved throughout the Alveolata and essential for parasite replication. We found that parasites lacking MAPK2 protein were defective in the initiation of daughter cell budding and were rendered inviable. Specifically, T. gondii MAPK2 (TgMAPK2) appears to be required for centrosome replication at the basal end of the nucleus, and its loss causes arrest early in parasite division. MAPK2 is unique to the Alveolata and not found in metazoa and likely is a critical component of an essential parasite-specific signaling network.
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13
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Abstract
Apicomplexans are obligate intracellular parasites harboring three sets of unique secretory organelles termed micronemes, rhoptries, and dense granules that are dedicated to the establishment of infection in the host cell. Apicomplexans rely on the endolysosomal system to generate the secretory organelles and to ingest and digest host cell proteins. These parasites also possess a metabolically relevant secondary endosymbiotic organelle, the apicoplast, which relies on vesicular trafficking for correct incorporation of nuclear-encoded proteins into the organelle. Here, we demonstrate that the trafficking and destination of vesicles to the unique and specialized parasite compartments depend on SNARE proteins that interact with tethering factors. Specifically, all secreted proteins depend on the function of SLY1 at the Golgi. In addition to a critical role in trafficking of endocytosed host proteins, TgVps45 is implicated in the biogenesis of the inner membrane complex (alveoli) in both Toxoplasma gondii and Plasmodium falciparum, likely acting in a coordinated manner with Stx16 and Stx6. Finally, Stx12 localizes to the endosomal-like compartment and is involved in the trafficking of proteins to the apical secretory organelles rhoptries and micronemes as well as to the apicoplast.IMPORTANCE The phylum of Apicomplexa groups medically relevant parasites such as those responsible for malaria and toxoplasmosis. As members of the Alveolata superphylum, these protozoans possess specialized organelles in addition to those found in all members of the eukaryotic kingdom. Vesicular trafficking is the major route of communication between membranous organelles. Neither the molecular mechanism that allows communication between organelles nor the vesicular fusion events that underlie it are completely understood in Apicomplexa. Here, we assessed the function of SEC1/Munc18 and SNARE proteins to identify factors involved in the trafficking of vesicles between these various organelles. We show that SEC1/Munc18 in interaction with SNARE proteins allows targeting of vesicles to the inner membrane complex, prerhoptries, micronemes, apicoplast, and vacuolar compartment from the endoplasmic reticulum, Golgi apparatus, or endosomal-like compartment. These data provide an exciting look at the "ZIP code" of vesicular trafficking in apicomplexans, essential for precise organelle biogenesis, homeostasis, and inheritance.
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14
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Bombardi L, Pedretti M, Conter C, Dominici P, Astegno A. Distinct Calcium Binding and Structural Properties of Two Centrin Isoforms from Toxoplasma gondii. Biomolecules 2020; 10:E1142. [PMID: 32759683 PMCID: PMC7465447 DOI: 10.3390/biom10081142] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2020] [Revised: 07/27/2020] [Accepted: 07/31/2020] [Indexed: 11/16/2022] Open
Abstract
Centrins are calcium (Ca2+)-binding proteins that have been implicated in several regulatory functions. In the protozoan parasite Toxoplasma gondii, the causative agent of toxoplasmosis, three isoforms of centrin have been identified. While increasing information is now available that links the function of centrins with defined parasite biological processes, knowledge is still limited on the metal-binding and structural properties of these proteins. Herein, using biophysical and structural approaches, we explored the Ca2+ binding abilities and the subsequent effects of Ca2+ on the structure of a conserved (TgCEN1) and a more divergent (TgCEN2) centrin isoform from T. gondii. Our data showed that TgCEN1 and TgCEN2 possess diverse molecular features, suggesting that they play nonredundant roles in parasite physiology. TgCEN1 binds two Ca2+ ions with high/medium affinity, while TgCEN2 binds one Ca2+ with low affinity. TgCEN1 undergoes significant Ca2+-dependent conformational changes that expose hydrophobic patches, supporting a role as a Ca2+ sensor in toxoplasma. In contrast, Ca2+ binding has a subtle influence on conformational features of TgCEN2 without resulting in hydrophobic exposure, suggesting a different Ca2+ relay mode for this isoform. Furthermore, TgCEN1 displays a Ca2+-dependent ability to self-assemble, while TgCEN2 did not. We discuss our findings in the context of Ca2+ signaling in toxoplasma.
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Affiliation(s)
| | | | | | | | - Alessandra Astegno
- Department of Biotechnology, University of Verona, Strada Le Grazie 15, 37134 Verona, Italy; (L.B.); (M.P.); (C.C.); (P.D.)
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15
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Semenovskaya K, Lévêque MF, Berry L, Bordat Y, Dubremetz JF, Lebrun M, Besteiro S. TgZFP2 is a novel zinc finger protein involved in coordinating mitosis and budding in Toxoplasma. Cell Microbiol 2019; 22:e13120. [PMID: 31628778 DOI: 10.1111/cmi.13120] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2019] [Revised: 09/09/2019] [Accepted: 09/23/2019] [Indexed: 12/13/2022]
Abstract
Zinc finger proteins (ZFPs) are one of the most abundant groups of proteins with a wide range of molecular functions. We have characterised a Toxoplasma protein that we named TgZFP2, as it bears a zinc finger domain conserved in eukaryotes. However, this protein has little homology outside this region and contains no other conserved domain that could hint for a particular function. We thus investigated TgZFP2 function by generating a conditional mutant. We showed that depletion of TgZFP2 leads to a drastic arrest in the parasite cell cycle, and complementation assays demonstrated the zinc finger domain is essential for TgZFP2 function. More precisely, whereas replication of the nuclear material is initially essentially unaltered, daughter cell budding is seriously impaired: to a large extent newly formed buds fail to incorporate nuclear material. TgZFP2 is found at the basal complex in extracellular parasites and after invasion, but as the parasites progress into cell division, it relocalises to cytoplasmic punctate structures and, strikingly, accumulates in the pericentrosomal area at the onset of daughter cell elongation. Centrosomes have emerged as major coordinators of the budding and nuclear cycles in Toxoplasma, and our study identifies a novel and important component of this machinery.
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Affiliation(s)
- Ksenia Semenovskaya
- Laboratory of Pathogen Host Interactions UMR5235, CNRS, Université de Montpellier, Montpellier, France
| | - Maude F Lévêque
- Laboratory of Pathogen Host Interactions UMR5235, CNRS, Université de Montpellier, Montpellier, France.,MiVEGEC, Université de Montpellier, CNRS, IRD, CHU de Montpellier, Montpellier, France
| | - Laurence Berry
- Laboratory of Pathogen Host Interactions UMR5235, CNRS, Université de Montpellier, Montpellier, France
| | - Yann Bordat
- Laboratory of Pathogen Host Interactions UMR5235, CNRS, Université de Montpellier, Montpellier, France
| | - Jean-François Dubremetz
- Laboratory of Pathogen Host Interactions UMR5235, CNRS, Université de Montpellier, Montpellier, France
| | - Maryse Lebrun
- Laboratory of Pathogen Host Interactions UMR5235, CNRS, Université de Montpellier, Montpellier, France
| | - Sébastien Besteiro
- Laboratory of Pathogen Host Interactions UMR5235, CNRS, Université de Montpellier, Montpellier, France
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16
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Kibria KMK, Ferdous J, Sardar R, Panda A, Gupta D, Mohmmed A, Malhotra P. A genome-wide analysis of coatomer protein (COP) subunits of apicomplexan parasites and their evolutionary relationships. BMC Genomics 2019; 20:98. [PMID: 30704415 PMCID: PMC6357402 DOI: 10.1186/s12864-019-5463-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2018] [Accepted: 01/17/2019] [Indexed: 02/08/2023] Open
Abstract
Background Protein secretion is an essential process in all eukaryotes including organisms belonging to the phylum Apicomplexa, which includes many intracellular parasites. The apicomplexan parasites possess a specialized collection of secretory organelles that release a number of proteins to facilitate the invasion of host cells and some of these proteins also participate in immune evasion. Like in other eukaryotes, these parasites possess a series of membrane-bound compartments, namely the endoplasmic reticulum (ER), the intermediate compartments (IC) or vesicular tubular clusters (VTS) and Golgi complex through which proteins pass in a sequential and vectorial fashion. Two sets of proteins; COPI and COPII are important for directing the sequential transfer of material between the ER and Golgi complex. Results Here, using in silico approaches, we identify the components of COPI and COPII complexes in the genome of apicomplexan organisms. The results showed that the COPI and COPII protein complexes are conserved in most apicomplexan genomes with few exceptions. Diversity among the components of COPI and COPII complexes in apicomplexan is either due to the absence of a subunit or due to the difference in the number of protein domains. For example, the COPI epsilon subunit and COPII sec13 subunit is absent in Babesia bovis, Theileria parva, and Theileria annulata genomes. Phylogenetic and domain analyses for all the proteins of COPI and COPII complexes was performed to predict their evolutionary relationship and functional significance. Conclusions The study thus provides insights into the apicomplexan COPI and COPII coating machinery, which is crucial for parasites secretory network needed for the invasion of host cells. Electronic supplementary material The online version of this article (10.1186/s12864-019-5463-1) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- K M Kaderi Kibria
- Department of Biotechnology and Genetic Engineering, Mawlana Bhashani Science and Technology University, Santosh, Tangail, 1902, Bangladesh.
| | - Jannatul Ferdous
- Department of Biotechnology and Genetic Engineering, Mawlana Bhashani Science and Technology University, Santosh, Tangail, 1902, Bangladesh
| | - Rahila Sardar
- Translational Bioinformatics Group, International Centre for Genetic Engineering and Biotechnology, P. O. Box 10504, Aruna Asaf Ali Marg, New Delhi, 110067, India
| | - Ashutosh Panda
- Department of Microbiology, All India Institute of Medical Science, New Delhi, 29, India
| | - Dinesh Gupta
- Translational Bioinformatics Group, International Centre for Genetic Engineering and Biotechnology, P. O. Box 10504, Aruna Asaf Ali Marg, New Delhi, 110067, India
| | - Asif Mohmmed
- Malaria Group, International Centre for Genetic Engineering and Biotechnology, P. O. Box 10504, Aruna Asaf Ali Marg, New Delhi, 110067, India
| | - Pawan Malhotra
- Malaria Group, International Centre for Genetic Engineering and Biotechnology, P. O. Box 10504, Aruna Asaf Ali Marg, New Delhi, 110067, India
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17
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Yakubu RR, Nieves E, Weiss LM. The Methods Employed in Mass Spectrometric Analysis of Posttranslational Modifications (PTMs) and Protein-Protein Interactions (PPIs). ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2019; 1140:169-198. [PMID: 31347048 DOI: 10.1007/978-3-030-15950-4_10] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Mass Spectrometry (MS) has revolutionized the way we study biomolecules, especially proteins, their interactions and posttranslational modifications (PTM). As such MS has established itself as the leading tool for the analysis of PTMs mainly because this approach is highly sensitive, amenable to high throughput and is capable of assigning PTMs to specific sites in the amino acid sequence of proteins and peptides. Along with the advances in MS methodology there have been improvements in biochemical, genetic and cell biological approaches to mapping the interactome which are discussed with consideration for both the practical and technical considerations of these techniques. The interactome of a species is generally understood to represent the sum of all potential protein-protein interactions. There are still a number of barriers to the elucidation of the human interactome or any other species as physical contact between protein pairs that occur by selective molecular docking in a particular spatiotemporal biological context are not easily captured and measured.PTMs massively increase the complexity of organismal proteomes and play a role in almost all aspects of cell biology, allowing for fine-tuning of protein structure, function and localization. There are an estimated 300 PTMS with a predicted 5% of the eukaryotic genome coding for enzymes involved in protein modification, however we have not yet been able to reliably map PTM proteomes due to limitations in sample preparation, analytical techniques, data analysis, and the substoichiometric and transient nature of some PTMs. Improvements in proteomic and mass spectrometry methods, as well as sample preparation, have been exploited in a large number of proteome-wide surveys of PTMs in many different organisms. Here we focus on previously published global PTM proteome studies in the Apicomplexan parasites T. gondii and P. falciparum which offer numerous insights into the abundance and function of each of the studied PTM in the Apicomplexa. Integration of these datasets provide a more complete picture of the relative importance of PTM and crosstalk between them and how together PTM globally change the cellular biology of the Apicomplexan protozoa. A multitude of techniques used to investigate PTMs, mostly techniques in MS-based proteomics, are discussed for their ability to uncover relevant biological function.
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Affiliation(s)
- Rama R Yakubu
- Department of Pathology, Albert Einstein College of Medicine, Bronx, NY, USA
| | - Edward Nieves
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, NY, USA.,Department of Developmental and Molecular Biology, Albert Einstein College of Medicine, Bronx, NY, USA
| | - Louis M Weiss
- Department of Pathology, Albert Einstein College of Medicine, Bronx, NY, USA. .,Department of Medicine, Albert Einstein College of Medicine, Bronx, NY, USA.
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18
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Venugopal K, Marion S. Secretory organelle trafficking in Toxoplasma gondii: A long story for a short travel. Int J Med Microbiol 2018; 308:751-760. [DOI: 10.1016/j.ijmm.2018.07.007] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2018] [Revised: 07/10/2018] [Accepted: 07/15/2018] [Indexed: 12/15/2022] Open
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19
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Hortua Triana MA, Márquez-Nogueras KM, Vella SA, Moreno SNJ. Calcium signaling and the lytic cycle of the Apicomplexan parasite Toxoplasma gondii. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2018; 1865:1846-1856. [PMID: 30992126 DOI: 10.1016/j.bbamcr.2018.08.004] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/15/2018] [Revised: 08/06/2018] [Accepted: 08/07/2018] [Indexed: 01/24/2023]
Abstract
Toxoplasma gondii has a complex life cycle involving different hosts and is dependent on fast responses, as the parasite reacts to changing environmental conditions. T. gondii causes disease by lysing the host cells that it infects and it does this by reiterating its lytic cycle, which consists of host cell invasion, replication inside the host cell, and egress causing host cell lysis. Calcium ion (Ca2+) signaling triggers activation of molecules involved in the stimulation and enhancement of each step of the parasite lytic cycle. Ca2+ signaling is essential for the cellular and developmental changes that support T. gondii parasitism. The characterization of the molecular players and pathways directly activated by Ca2+ signaling in Toxoplasma is sketchy and incomplete. The evolutionary distance between Toxoplasma and other eukaryotic model systems makes the comparison sometimes not informative. The advent of new genomic information and new genetic tools applicable for studying Toxoplasma biology is rapidly changing this scenario. The Toxoplasma genome reveals the presence of many genes potentially involved in Ca2+ signaling, even though the role of most of them is not known. The use of Genetically Encoded Calcium Indicators (GECIs) has allowed studies on the role of novel calcium-related proteins on egress, an essential step for the virulence and dissemination of Toxoplasma. In addition, the discovery of new Ca2+ players is generating novel targets for drugs, vaccines, and diagnostic tools and a better understanding of the biology of these parasites.
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Affiliation(s)
| | | | - Stephen A Vella
- Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, GA 30602, USA
| | - Silvia N J Moreno
- Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, GA 30602, USA; Department of Cellular Biology, University of Georgia, Athens, GA 30602, USA.
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20
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Courjol F, Gissot M. A coiled-coil protein is required for coordination of karyokinesis and cytokinesis in Toxoplasma gondii. Cell Microbiol 2018; 20:e12832. [PMID: 29447426 DOI: 10.1111/cmi.12832] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2017] [Revised: 01/19/2018] [Accepted: 02/07/2018] [Indexed: 12/11/2022]
Abstract
Toxoplasma gondii is a unicellular eukaryotic pathogen that belongs to the Apicomplexa phylum, which encompasses some of the deadliest pathogens of medical and veterinary importance. The centrosome is key to the organisation and coordination of the cell cycle and division of apicomplexan parasites. The T. gondii centrosome possesses a particular bipartite structure (outer and inner cores). One of the main roles of the centrosome is to ensure proper coordination of karyokinesis. However, how these 2 events are coordinated is still unknown in T. gondii, for which the centrosome components are poorly described. To gain more insights into the biology and the composition of the T. gondii centrosome, we characterised a protein that resides at the interface of the outer and inner core centrosomes. TgCep530 is a large coiled-coil protein with an essential role in the survival of the parasite. Depletion of this protein leads to the accumulation of parasites lacking nuclei and disruption of the normal cell cycle. Lack of TgCep530 results in a discoordination between the nuclear cycle and the budding cycle that yields fully formed parasites without nuclei. TgCep530 has a crucial role in the coordination of karyokinesis and cytokinesis.
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Affiliation(s)
- Flavie Courjol
- CNRS, Inserm, CHU Lille, Institut Pasteur de Lille, U1019 - UMR 8204 - CIIL - Centre d'Infection et d'Immunité de Lille, Univ. Lille, Lille, France
| | - Mathieu Gissot
- CNRS, Inserm, CHU Lille, Institut Pasteur de Lille, U1019 - UMR 8204 - CIIL - Centre d'Infection et d'Immunité de Lille, Univ. Lille, Lille, France
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21
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Yakubu RR, Weiss LM, Silmon de Monerri NC. Post-translational modifications as key regulators of apicomplexan biology: insights from proteome-wide studies. Mol Microbiol 2017; 107:1-23. [PMID: 29052917 DOI: 10.1111/mmi.13867] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2017] [Revised: 10/12/2017] [Accepted: 10/16/2017] [Indexed: 12/12/2022]
Abstract
Parasites of the Apicomplexa phylum, such as Plasmodium spp. and Toxoplasma gondii, undergo complex life cycles involving multiple stages with distinct biology and morphologies. Post-translational modifications (PTMs), such as phosphorylation, acetylation and glycosylation, regulate numerous cellular processes, playing a role in every aspect of cell biology. PTMs can occur on proteins at any time in their lifespan and through alterations of target protein activity, localization, protein-protein interactions, among other functions, dramatically increase proteome diversity and complexity. In addition, PTMs can be induced or removed on changes in cellular environment and state. Thus, PTMs are likely to be key regulators of developmental transitions, biology and pathogenesis of apicomplexan parasites. In this review we examine the roles of PTMs in both parasite-specific and conserved eukaryotic processes, and the potential crosstalk between PTMs, that together regulate the intricate lives of these protozoa.
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Affiliation(s)
- Rama R Yakubu
- Department of Pathology, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY, 10128, USA.,Department of Medicine, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY, 10128, USA
| | - Louis M Weiss
- Department of Pathology, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY, 10128, USA.,Department of Medicine, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY, 10128, USA
| | - Natalie C Silmon de Monerri
- Department of Pathology, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY, 10128, USA.,Department of Medicine, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY, 10128, USA
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22
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Morlon-Guyot J, Francia ME, Dubremetz JF, Daher W. Towards a molecular architecture of the centrosome in Toxoplasma gondii. Cytoskeleton (Hoboken) 2017; 74:55-71. [PMID: 28026138 DOI: 10.1002/cm.21353] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2016] [Revised: 12/14/2016] [Accepted: 12/15/2016] [Indexed: 12/21/2022]
Abstract
Toxoplasma gondii is the causative agent of toxoplasmosis. The pathogenicity of this unicellular parasite is tightly linked to its ability to efficiently proliferate within its host. Tachyzoites, the fast dividing form of the parasite, divide by endodyogeny. This process involves a single round of DNA replication, closed nuclear mitosis, and assembly of two daughter cells within a mother. The successful completion of endodyogeny relies on the temporal and spatial coordination of a plethora of simultaneous events. It has been shown that the Toxoplasma centrosome serves as signaling hub which nucleates spindle microtubules during mitosis and organizes the scaffolding of daughter cells components during cytokinesis. In addition, the centrosome is essential for inheriting both the apicoplast (a chloroplast-like organelle) and the Golgi apparatus. A growing body of evidence supports the notion that the T. gondii centrosome diverges in protein composition, structure and organization from its counterparts in higher eukaryotes making it an attractive source of potentially druggable targets. Here, we summarize the current knowledge on T. gondii centrosomal proteins and extend the putative centrosomal protein repertoire by in silico identification of mammalian centrosomal protein orthologs. We propose a working model for the organization and architecture of the centrosome in Toxoplasma parasites. Experimental validation of our proposed model will uncover how each predicted protein translates into the biology of centrosome, cytokinesis, karyokinesis, and organelle inheritance in Toxoplasma parasites.
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Affiliation(s)
- Juliette Morlon-Guyot
- Dynamique des Interactions Membranaires Normales et Pathologiques, UMR5235 CNRS, Université Montpellier, Montpellier, France
| | - Maria E Francia
- Molecular Biology Unit, Institut Pasteur de Montevideo, Mataojo 2020, Montevideo, 11400, Uruguay
| | - Jean-François Dubremetz
- Dynamique des Interactions Membranaires Normales et Pathologiques, UMR5235 CNRS, Université Montpellier, Montpellier, France
| | - Wassim Daher
- Dynamique des Interactions Membranaires Normales et Pathologiques, UMR5235 CNRS, Université Montpellier, Montpellier, France
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An evolutionarily conserved SSNA1/DIP13 homologue is a component of both basal and apical complexes of Toxoplasma gondii. Sci Rep 2016; 6:27809. [PMID: 27324377 PMCID: PMC4914967 DOI: 10.1038/srep27809] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2016] [Accepted: 05/25/2016] [Indexed: 12/19/2022] Open
Abstract
Microtubule-based cytoskeletal structures have fundamental roles in several essential eukaryotic processes, including transport of intracellular constituents as well as ciliary and flagellar mobility. Temporal and spatial organisation of microtubules is determined by microtubule organising centers and a number of appendages and accessory proteins. Members of the SSNA1/DIP13 family are coiled coil proteins that are known to localise to microtubular structures like centrosomes and flagella, but are otherwise poorly characterised. We have identified a homologue of SSNA1/DIP13 in the parasitic protist Toxoplasma gondii and found it localises to parasite-specific cytoskeletal structures: the conoid in the apical complex of mature and dividing cells, and the basal complex in elongating daughter cells during cell division. This protein is dispensable for parasite growth in vitro. However, quite remarkably, this coiled coil protein is able to self-associate into higher order structures both in vitro and in vivo, and its overexpression is impairing parasite division.
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Autophagy-Related Protein ATG8 Has a Noncanonical Function for Apicoplast Inheritance in Toxoplasma gondii. mBio 2015; 6:e01446-15. [PMID: 26507233 PMCID: PMC4626856 DOI: 10.1128/mbio.01446-15] [Citation(s) in RCA: 59] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED Autophagy is a catabolic process widely conserved among eukaryotes that permits the rapid degradation of unwanted proteins and organelles through the lysosomal pathway. This mechanism involves the formation of a double-membrane structure called the autophagosome that sequesters cellular components to be degraded. To orchestrate this process, yeasts and animals rely on a conserved set of autophagy-related proteins (ATGs). Key among these factors is ATG8, a cytoplasmic protein that is recruited to nascent autophagosomal membranes upon the induction of autophagy. Toxoplasma gondii is a potentially harmful human pathogen in which only a subset of ATGs appears to be present. Although this eukaryotic parasite seems able to generate autophagosomes upon stresses such as nutrient starvation, the full functionality and biological relevance of a canonical autophagy pathway are as yet unclear. Intriguingly, in T. gondii, ATG8 localizes to the apicoplast under normal intracellular growth conditions. The apicoplast is a nonphotosynthetic plastid enclosed by four membranes resulting from a secondary endosymbiosis. Using superresolution microscopy and biochemical techniques, we show that TgATG8 localizes to the outermost membrane of this organelle. We investigated the unusual function of TgATG8 at the apicoplast by generating a conditional knockdown mutant. Depletion of TgATG8 led to rapid loss of the organelle and subsequent intracellular replication defects, indicating that the protein is essential for maintaining apicoplast homeostasis and thus for survival of the tachyzoite stage. More precisely, loss of TgATG8 led to abnormal segregation of the apicoplast into the progeny because of a loss of physical interactions of the organelle with the centrosomes. IMPORTANCE By definition, autophagy is a catabolic process that leads to the digestion and recycling of eukaryotic cellular components. The molecular machinery of autophagy was identified mainly in model organisms such as yeasts but remains poorly characterized in phylogenetically distant apicomplexan parasites. We have uncovered an unusual function for autophagy-related protein ATG8 in Toxoplasma gondii: TgATG8 is crucial for normal replication of the parasite inside its host cell. Seemingly unrelated to the catabolic autophagy process, TgATG8 associates with the outer membrane of the nonphotosynthetic plastid harbored by the parasite called the apicoplast, and there it plays an important role in the centrosome-driven inheritance of the organelle during cell division. This not only reveals an unexpected function for an autophagy-related protein but also sheds new light on the division process of an organelle that is vital to a group of important human and animal pathogens.
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Chen CT, Kelly M, Leon JD, Nwagbara B, Ebbert P, Ferguson DJP, Lowery LA, Morrissette N, Gubbels MJ. Compartmentalized Toxoplasma EB1 bundles spindle microtubules to secure accurate chromosome segregation. Mol Biol Cell 2015; 26:4562-76. [PMID: 26466679 PMCID: PMC4678015 DOI: 10.1091/mbc.e15-06-0437] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2015] [Accepted: 10/02/2015] [Indexed: 11/11/2022] Open
Abstract
The opportunistic apicomplexan parasite Toxoplasma gondii divides by intertwined closed mitosis and internal budding. Centrosome positioning and MT acetylation control spindle dynamics, and the MT-associated protein TgEB1 residing in the nucleus contributes to mitotic fidelity by bundling the spindle MTs. Toxoplasma gondii replicates asexually by a unique internal budding process characterized by interwoven closed mitosis and cytokinesis. Although it is known that the centrosome coordinates these processes, the spatiotemporal organization of mitosis remains poorly defined. Here we demonstrate that centrosome positioning around the nucleus may signal spindle assembly: spindle microtubules (MTs) are first assembled when the centrosome moves to the basal side and become extensively acetylated after the duplicated centrosomes reposition to the apical side. We also tracked the spindle MTs using the MT plus end–binding protein TgEB1. Endowed by a C-terminal NLS, TgEB1 resides in the nucleoplasm in interphase and associates with the spindle MTs during mitosis. TgEB1 also associates with the subpellicular MTs at the growing end of daughter buds toward the completion of karyokinesis. Depletion of TgEB1 results in escalated disintegration of kinetochore clustering. Furthermore, we show that TgEB1’s MT association in Toxoplasma and in a heterologous system (Xenopus) is based on the same principles. Finally, overexpression of a high-MT-affinity TgEB1 mutant promotes the formation of overstabilized MT bundles, resulting in avulsion of otherwise tightly clustered kinetochores. Overall we conclude that centrosome position controls spindle activity and that TgEB1 is critical for mitotic integrity.
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Affiliation(s)
- Chun-Ti Chen
- Department of Biology, Boston College, Chestnut Hill, MA 02467
| | - Megan Kelly
- Department of Biology, Boston College, Chestnut Hill, MA 02467
| | - Jessica de Leon
- Molecular Biology and Biochemistry, University of California, Irvine, Irvine, CA 92697
| | | | - Patrick Ebbert
- Department of Biology, Boston College, Chestnut Hill, MA 02467
| | - David J P Ferguson
- Nuffield Department of Clinical Laboratory Science, University of Oxford, John Radcliffe Hospital, Oxford OX3 9DU, United Kingdom
| | | | - Naomi Morrissette
- Molecular Biology and Biochemistry, University of California, Irvine, Irvine, CA 92697
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Abstract
Toxoplasmosis is the clinical and pathological consequence of acute infection with the obligate intracellular apicomplexan parasite Toxoplasma gondii. Symptoms result from tissue destruction that accompanies lytic parasite growth. This review updates current understanding of the host cell invasion, parasite replication, and eventual egress that constitute the lytic cycle, as well as the ways T. gondii manipulates host cells to ensure its survival. Since the publication of a previous iteration of this review 15 years ago, important advances have been made in our molecular understanding of parasite growth and mechanisms of host cell egress, and knowledge of the parasite's manipulation of the host has rapidly progressed. Here we cover molecular advances and current conceptual frameworks that include each of these topics, with an eye to what may be known 15 years from now.
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Affiliation(s)
- Ira J Blader
- Department of Microbiology and Immunology, University at Buffalo, Buffalo, New York 14127;
| | - Bradley I Coleman
- Department of Biology, Boston College, Chestnut Hill, Massachusetts 02467; , ,
| | - Chun-Ti Chen
- Department of Biology, Boston College, Chestnut Hill, Massachusetts 02467; , ,
| | - Marc-Jan Gubbels
- Department of Biology, Boston College, Chestnut Hill, Massachusetts 02467; , ,
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Chen CT, Gubbels MJ. Apicomplexan cell cycle flexibility: centrosome controls the clutch. Trends Parasitol 2015; 31:229-30. [PMID: 25899747 DOI: 10.1016/j.pt.2015.04.003] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2015] [Accepted: 04/07/2015] [Indexed: 12/14/2022]
Abstract
The centrosome serves as a central hub coordinating multiple cellular events in eukaryotes. A recent study in Toxoplasma gondii revealed a unique bipartite structure of the centrosome, which coordinates the nuclear cycle (S-phase and mitosis) and budding cycle (cytokinesis) of the parasite, and deciphers the principle behind flexible apicomplexan cell division modes.
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Affiliation(s)
- Chun-Ti Chen
- Department of Biology, Boston College, Chestnut Hill, MA 02467, USA
| | - Marc-Jan Gubbels
- Department of Biology, Boston College, Chestnut Hill, MA 02467, USA.
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Lourido S, Moreno SNJ. The calcium signaling toolkit of the Apicomplexan parasites Toxoplasma gondii and Plasmodium spp. Cell Calcium 2014; 57:186-93. [PMID: 25605521 DOI: 10.1016/j.ceca.2014.12.010] [Citation(s) in RCA: 104] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2014] [Accepted: 12/15/2014] [Indexed: 12/21/2022]
Abstract
Apicomplexan parasites have complex life cycles, frequently split between different hosts and reliant on rapid responses as the parasites react to changing environmental conditions. Calcium ion (Ca(2+)) signaling is consequently essential for the cellular and developmental changes that support Apicomplexan parasitism. Apicomplexan genomes reveal a rich repertoire of genes involved in calcium signaling, although many of the genes responsible for observed physiological changes remain unknown. There is evidence, for example, for the presence of a nifedipine-sensitive calcium entry mechanism in Toxoplasma, but the molecular components involved in Ca(2+) entry in both Toxoplasma and Plasmodium, have not been identified. The major calcium stores are the endoplasmic reticulum (ER), the acidocalcisomes, and the plant-like vacuole in Toxoplasma, or the food vacuole in Plasmodium spp. Pharmacological evidence suggests that Ca(2+) release from intracellular stores may be mediated by inositol 1,4,5-trisphosphate (IP3) or cyclic ADP ribose (cADPR) although there is no molecular evidence for the presence of receptors for these second messengers in the parasites. Several Ca(2+)-ATPases are present in Apicomplexans and a putative mitochondrial Ca(2+)/H(+) exchanger has been identified. Apicomplexan genomes contain numerous genes encoding Ca(2+)-binding proteins, with the notable expansion of calcium-dependent protein kinases (CDPKs), whose study has revealed roles in gliding motility, microneme secretion, host cell invasion and egress, and parasite differentiation. Microneme secretion has also been shown to depend on the C2 domain containing protein DOC2 in both Plasmodium spp. and Toxoplasma, providing further evidence for the complex transduction of Ca(2+) signals in these organisms. The characterization of these pathways could lead to the discovery of novel drug targets and to a better understanding of the role of Ca(2+) in these parasites.
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Affiliation(s)
- Sebastian Lourido
- Whitehead Institute for Biomedical Research, Cambridge, MA 02142, USA
| | - Silvia N J Moreno
- Center for Tropical and Emerging Global Diseases, Department of Cellular Biology, University of Georgia, Athens, GA 30602, USA.
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29
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Targeting Toxoplasma tubules: tubulin, microtubules, and associated proteins in a human pathogen. EUKARYOTIC CELL 2014; 14:2-12. [PMID: 25380753 DOI: 10.1128/ec.00225-14] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Toxoplasma gondii is an obligate intracellular parasite that causes serious opportunistic infections, birth defects, and blindness in humans. Microtubules are critically important components of diverse structures that are used throughout the Toxoplasma life cycle. As in other eukaryotes, spindle microtubules are required for chromosome segregation during replication. Additionally, a set of membrane-associated microtubules is essential for the elongated shape of invasive "zoites," and motility follows a spiral trajectory that reflects the path of these microtubules. Toxoplasma zoites also construct an intricate, tubulin-based apical structure, termed the conoid, which is important for host cell invasion and associates with proteins typically found in the flagellar apparatus. Last, microgametes specifically construct a microtubule-containing flagellar axoneme in order to fertilize macrogametes, permitting genetic recombination. The specialized roles of these microtubule populations are mediated by distinct sets of associated proteins. This review summarizes our current understanding of the role of tubulin, microtubule populations, and associated proteins in Toxoplasma; these components are used for both novel and broadly conserved processes that are essential for parasite survival.
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The apical complex provides a regulated gateway for secretion of invasion factors in Toxoplasma. PLoS Pathog 2014; 10:e1004074. [PMID: 24743791 PMCID: PMC3990729 DOI: 10.1371/journal.ppat.1004074] [Citation(s) in RCA: 77] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2013] [Accepted: 03/04/2014] [Indexed: 11/19/2022] Open
Abstract
The apical complex is the definitive cell structure of phylum Apicomplexa, and is the focus of the events of host cell penetration and the establishment of intracellular parasitism. Despite the importance of this structure, its molecular composition is relatively poorly known and few studies have experimentally tested its functions. We have characterized a novel Toxoplasma gondii protein, RNG2, that is located at the apical polar ring--the common structural element of apical complexes. During cell division, RNG2 is first recruited to centrosomes immediately after their duplication, confirming that assembly of the new apical complex commences as one of the earliest events of cell replication. RNG2 subsequently forms a ring, with the carboxy- and amino-termini anchored to the apical polar ring and mobile conoid, respectively, linking these two structures. Super-resolution microscopy resolves these two termini, and reveals that RNG2 orientation flips during invasion when the conoid is extruded. Inducible knockdown of RNG2 strongly inhibits host cell invasion. Consistent with this, secretion of micronemes is prevented in the absence of RNG2. This block, however, can be fully or partially overcome by exogenous stimulation of calcium or cGMP signaling pathways, respectively, implicating the apical complex directly in these signaling events. RNG2 demonstrates for the first time a role for the apical complex in controlling secretion of invasion factors in this important group of parasites.
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Abstract
Toxoplasma gondii and Plasmodium falciparum are important human pathogens. These parasites and many of their apicomplexan relatives undergo a complex developmental process in the cells of their hosts, which includes genome replication, cell division and the assembly of new invasive stages. Apicomplexan cell cycle progression is both globally and locally regulated. Global regulation is carried out throughout the cytoplasm by diffusible factors that include cell cycle-specific kinases, cyclins and transcription factors. Local regulation acts on individual nuclei and daughter cells that are developing inside the mother cell. We propose that the centrosome is a master regulator that physically tethers cellular components and that provides spatial and temporal control of apicomplexan cell division.
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Affiliation(s)
- Maria E Francia
- Department of Cellular Biology, University of Georgia, Athens, Georgia 30602, USA
| | - Boris Striepen
- 1] Department of Cellular Biology, University of Georgia, Athens, Georgia 30602, USA. [2] Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, Georgia 30602, USA
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Farrell M, Gubbels MJ. The Toxoplasma gondii kinetochore is required for centrosome association with the centrocone (spindle pole). Cell Microbiol 2013; 16:78-94. [PMID: 24015880 DOI: 10.1111/cmi.12185] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2013] [Revised: 08/01/2013] [Accepted: 08/14/2013] [Indexed: 12/17/2022]
Abstract
The kinetochore is a multi-protein structure assembled on eukaryotic centromeres mediating chromosome attachment to spindle microtubules. Here we identified the kinetochore proteins Nuf2 and Ndc80 in the apicomplexan parasite Toxoplasma gondii. Localization revealed that kinetochores remain clustered throughout the cell cycle and colocalize with clustered centromeres at the centrocone, a structure containing the spindle pole embedded in the nuclear envelope. Pharmacological disruption of microtubules resulted in partial loss of some kinetochore and centromere clustering, indicating microtubules are necessary but not strictly required for kinetochore clustering. Generation of a TgNuf2 conditional knock-down strain revealed it is essential for chromosome segregation, but dispensable for centromere clustering. The centromeres actually remained associated with the centrocone suggesting microtubule binding is not required for their interaction with the spindle pole. The most striking observation upon TgNuf2 depletion was that the centrosome behaved normally, but that it lost its association with the centrocone. This suggests that microtubules are essential to maintain contact between the centrosome and chromosomes, and this interaction is critical for the partitioning of the nuclei into the two daughter parasites. Finally, genetic complementation experiments with mutated TgNuf2 constructs highlighted an apicomplexan-specific motif with a putative role in nuclear localization.
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Affiliation(s)
- Megan Farrell
- Department of Biology, Boston College, 140 Commonwealth Avenue, Higgins Hall 355, Chestnut Hill, MA, 02467, USA
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33
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Morlon-Guyot J, Berry L, Chen CT, Gubbels MJ, Lebrun M, Daher W. The Toxoplasma gondii calcium-dependent protein kinase 7 is involved in early steps of parasite division and is crucial for parasite survival. Cell Microbiol 2013; 16:95-114. [PMID: 24011186 DOI: 10.1111/cmi.12186] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2013] [Revised: 08/12/2013] [Accepted: 08/14/2013] [Indexed: 12/22/2022]
Abstract
Apicomplexan parasites express various calcium-dependent protein kinases (CDPKs), and some of them play essential roles in invasion and egress. Five of the six CDPKs conserved in most Apicomplexa have been studied at the molecular and cellular levels in Plasmodium species and/or in Toxoplasma gondii parasites, but the function of CDPK7 was so far uncharacterized. In T. gondii, during intracellular replication, two parasites are formed within a mother cell through a unique process called endodyogeny. Here we demonstrate that the knock-down of CDPK7 protein in T. gondii results in pronounced defects in parasite division and a major growth deficiency, while it is dispensable for motility, egress and microneme exocytosis. In cdpk7-depleted parasites, the overall DNA content was not impaired, but the polarity of daughter cells budding and the fate of several subcellular structures or proteins involved in cell division were affected, such as the centrosomes and the kinetochore. Overall, our data suggest that CDPK7 is crucial for proper maintenance of centrosome integrity required for the initiation of endodyogeny. Our findings provide a first insight into the probable role of calcium-dependent signalling in parasite multiplication, in addition to its more widely explored role in invasion and egress.
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Affiliation(s)
- Juliette Morlon-Guyot
- Dynamique des Interactions Membranaires Normales et Pathologiques, UMR5235 CNRS, Université de Montpellier I et II, Montpellier, France
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Jacot D, Daher W, Soldati-Favre D. Toxoplasma gondii myosin F, an essential motor for centrosomes positioning and apicoplast inheritance. EMBO J 2013; 32:1702-16. [PMID: 23695356 DOI: 10.1038/emboj.2013.113] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2012] [Accepted: 04/22/2013] [Indexed: 11/09/2022] Open
Abstract
Members of the Apicomplexa phylum possess an organelle surrounded by four membranes, originating from the secondary endosymbiosis of a red alga. This so-called apicoplast hosts essential metabolic pathways. We report here that apicoplast inheritance is an actin-based process. Concordantly, parasites depleted in either profilin or actin depolymerizing factor, or parasites overexpressing the FH2 domain of formin 2, result in loss of the apicoplast. The class XXII myosin F (MyoF) is conserved across the phylum and localizes in the vicinity of the Toxoplasma gondii apicoplast during division. Conditional knockdown of TgMyoF severely affects apicoplast turnover, leading to parasite death. This recapitulates the phenotype observed upon perturbation of actin dynamics that led to the accumulation of the apicoplast and secretory organelles in enlarged residual bodies. To further dissect the mode of action of this motor, we conditionally stabilized the tail of MyoF, which forms an inactive heterodimer with endogenous TgMyoF. This dominant negative mutant reveals a central role of this motor in the positioning of the two centrosomes prior to daughter cell formation and in apicoplast segregation.
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Affiliation(s)
- Damien Jacot
- Department of Microbiology and Molecular Medicine, CMU, University of Geneva, Geneva, Switzerland
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A SAS-6-like protein suggests that the Toxoplasma conoid complex evolved from flagellar components. EUKARYOTIC CELL 2013; 12:1009-19. [PMID: 23687115 PMCID: PMC3697468 DOI: 10.1128/ec.00096-13] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
SAS-6 is required for centriole biogenesis in diverse eukaryotes. Here, we describe a novel family of SAS-6-like (SAS6L) proteins that share an N-terminal domain with SAS-6 but lack coiled-coil tails. SAS6L proteins are found in a subset of eukaryotes that contain SAS-6, including diverse protozoa and green algae. In the apicomplexan parasite Toxoplasma gondii, SAS-6 localizes to the centriole but SAS6L is found above the conoid, an enigmatic tubulin-containing structure found at the apex of a subset of alveolate organisms. Loss of SAS6L causes reduced fitness in Toxoplasma. The Trypanosoma brucei homolog of SAS6L localizes to the basal-plate region, the site in the axoneme where the central-pair microtubules are nucleated. When endogenous SAS6L is overexpressed in Toxoplasma tachyzoites or Trypanosoma trypomastigotes, it forms prominent filaments that extend through the cell cytoplasm, indicating that it retains a capacity to form higher-order structures despite lacking a coiled-coil domain. We conclude that although SAS6L proteins share a conserved domain with SAS-6, they are a functionally distinct family that predates the last common ancestor of eukaryotes. Moreover, the distinct localization of the SAS6L protein in Trypanosoma and Toxoplasma adds weight to the hypothesis that the conoid complex evolved from flagellar components.
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36
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Beck JR, Fung C, Straub KW, Coppens I, Vashisht AA, Wohlschlegel JA, Bradley PJ. A Toxoplasma palmitoyl acyl transferase and the palmitoylated armadillo repeat protein TgARO govern apical rhoptry tethering and reveal a critical role for the rhoptries in host cell invasion but not egress. PLoS Pathog 2013; 9:e1003162. [PMID: 23408890 PMCID: PMC3567180 DOI: 10.1371/journal.ppat.1003162] [Citation(s) in RCA: 70] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2012] [Accepted: 12/13/2012] [Indexed: 11/19/2022] Open
Abstract
Apicomplexans are obligate intracellular parasites that actively penetrate their host cells to create an intracellular niche for replication. Commitment to invasion is thought to be mediated by the rhoptries, specialized apical secretory organelles that inject a protein complex into the host cell to form a tight-junction for parasite entry. Little is known about the molecular factors that govern rhoptry biogenesis, their subcellular organization at the apical end of the parasite and subsequent release of this organelle during invasion. We have identified a Toxoplasma palmitoyl acyltransferase, TgDHHC7, which localizes to the rhoptries. Strikingly, conditional knockdown of TgDHHC7 results in dispersed rhoptries that fail to organize at the apical end of the parasite and are instead scattered throughout the cell. While the morphology and content of these rhoptries appears normal, failure to tether at the apex results in a complete block in host cell invasion. In contrast, attachment and egress are unaffected in the knockdown, demonstrating that the rhoptries are not required for these processes. We show that rhoptry targeting of TgDHHC7 requires a short, highly conserved C-terminal region while a large, divergent N-terminal domain is dispensable for both targeting and function. Additionally, a point mutant lacking a key residue predicted to be critical for enzyme activity fails to rescue apical rhoptry tethering, strongly suggesting that tethering of the organelle is dependent upon TgDHHC7 palmitoylation activity. We tie the importance of this activity to the palmitoylated Armadillo Repeats-Only (TgARO) rhoptry protein by showing that conditional knockdown of TgARO recapitulates the dispersed rhoptry phenotype of TgDHHC7 knockdown. The unexpected finding that apicomplexans have exploited protein palmitoylation for apical organelle tethering yields new insight into the biogenesis and function of rhoptries and may provide new avenues for therapeutic intervention against Toxoplasma and related apicomplexan parasites. Apicomplexans possess a highly polarized secretory pathway that is critical for their ability to invade host cells and cause disease. This unique cellular organization enables delivery of protein cargo to specialized secretory organelles called micronemes and rhoptries that drive forward penetration into the host cell. The rhoptries are tethered in a bundle at the apex of the parasite, but how these organelles are organized in this manner is unknown. In this work, we identify a rhoptry-localized palmitoyl acyl transferase (named TgDHHC7) that functions to properly affix the rhoptries at the apical end of the parasite. Conditional disruption of TgDHHC7 results in a failure to tether the rhoptries at the cell apex and a corresponding loss of rhoptry function. We exploit this mutant to clearly demonstrate a critical role for the rhoptries in host invasion but not attachment or egress. Additionally, we find that mutation of a key residue predicted to be required for catalytic activity renders TgDHHC7 non-functional and that knockdown of the candidate substrate TgARO produces an identical phenotype to loss of TgDHHC7. The finding that Toxoplasma employs protein palmitoylation to position the rhoptries at the cell apex provides new insight into the molecular mechanisms that underlie apicomplexan cell polarity, host invasion and pathogenesis.
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Affiliation(s)
- Josh R. Beck
- Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, Los Angeles, California, United States of America
| | - Connie Fung
- Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, Los Angeles, California, United States of America
| | - Kurtis W. Straub
- Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, Los Angeles, California, United States of America
| | - Isabelle Coppens
- Department of Molecular Microbiology and Immunology, Johns Hopkins University Bloomberg School of Public Health, Baltimore, Maryland, United States of America
| | - Ajay A. Vashisht
- Department of Biological Chemistry, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California, United States of America
| | - James A. Wohlschlegel
- Department of Biological Chemistry, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California, United States of America
| | - Peter J. Bradley
- Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, Los Angeles, California, United States of America
- * E-mail:
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Cell division in Apicomplexan parasites is organized by a homolog of the striated rootlet fiber of algal flagella. PLoS Biol 2012; 10:e1001444. [PMID: 23239939 PMCID: PMC3519896 DOI: 10.1371/journal.pbio.1001444] [Citation(s) in RCA: 88] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2012] [Accepted: 10/30/2012] [Indexed: 01/08/2023] Open
Abstract
Apicomplexan parasites undergo cell division using an evolutionarily conserved mechanism first described in the positioning and assembly of flagella in algae. Apicomplexa are intracellular parasites that cause important human diseases including malaria and toxoplasmosis. During host cell infection new parasites are formed through a budding process that parcels out nuclei and organelles into multiple daughters. Budding is remarkably flexible in output and can produce two to thousands of progeny cells. How genomes and daughters are counted and coordinated is unknown. Apicomplexa evolved from single celled flagellated algae, but with the exception of the gametes, lack flagella. Here we demonstrate that a structure that in the algal ancestor served as the rootlet of the flagellar basal bodies is required for parasite cell division. Parasite striated fiber assemblins (SFA) polymerize into a dynamic fiber that emerges from the centrosomes immediately after their duplication. The fiber grows in a polarized fashion and daughter cells form at its distal tip. As the daughter cell is further elaborated it remains physically tethered at its apical end, the conoid and polar ring. Genetic experiments in Toxoplasma gondii demonstrate two essential components of the fiber, TgSFA2 and 3. In the absence of either of these proteins cytokinesis is blocked at its earliest point, the initiation of the daughter microtubule organizing center (MTOC). Mitosis remains unimpeded and mutant cells accumulate numerous nuclei but fail to form daughter cells. The SFA fiber provides a robust spatial and temporal organizer of parasite cell division, a process that appears hard-wired to the centrosome by multiple tethers. Our findings have broader evolutionary implications. We propose that Apicomplexa abandoned flagella for most stages yet retained the organizing principle of the flagellar MTOC. Instead of ensuring appropriate numbers of flagella, the system now positions the apical invasion complexes. This suggests that elements of the invasion apparatus may be derived from flagella or flagellum associated structures. Malaria, toxoplasmosis, and related diseases are caused by infection with unicellular parasites called Apicomplexa. Their name refers to the elaborate invasion machinery that occupies the apical end of the parasite cell. This apparatus allows the parasite to force its way into the cells of its host, and to deliver factors that will manipulate host cell structure, gene expression, and metabolism. Once in the host cell the parasite will begin to grow. The parasite replicates its genome and organelles numerous times and then loads these various elements into numerous daughter cells that will further spread the infection. Here we report a fiber that coordinates the daughter cell budding process. The fiber links the centrosome, which controls the mitotic spindle, and the genome with the microtubule organizing center of the budding daughter. Parasite mutants lacking the proteins that build the fiber fail to form daughter cells at the earliest step. The fiber and its components are remarkably similar to fibers that coordinate flagella in algae. While Apicomplexa are not flagellated (with the exception of certain gamete stages) they evolved from flagellated algae. We propose that elements of the invasion apparatus evolved from the flagellum or flagellum associated structures.
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38
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Deponte M, Hoppe HC, Lee MC, Maier AG, Richard D, Rug M, Spielmann T, Przyborski JM. Wherever I may roam: Protein and membrane trafficking in P. falciparum-infected red blood cells. Mol Biochem Parasitol 2012; 186:95-116. [DOI: 10.1016/j.molbiopara.2012.09.007] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2012] [Revised: 09/21/2012] [Accepted: 09/24/2012] [Indexed: 11/27/2022]
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39
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Anderson-White B, Beck JR, Chen CT, Meissner M, Bradley PJ, Gubbels MJ. Cytoskeleton assembly in Toxoplasma gondii cell division. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2012; 298:1-31. [PMID: 22878103 PMCID: PMC4066374 DOI: 10.1016/b978-0-12-394309-5.00001-8] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Cell division across members of the protozoan parasite phylum Apicomplexa displays a surprising diversity between different species as well as between different life stages of the same parasite. In most cases, infection of a host cell by a single parasite results in the formation of a polyploid cell from which individual daughters bud in a process dependent on a final round of mitosis. Unlike other apicomplexans, Toxoplasma gondii divides by a binary process consisting of internal budding that results in only two daughter cells per round of division. Since T. gondii is experimentally accessible and displays the simplest division mode, it has manifested itself as a model for apicomplexan daughter formation. Here, we review newly emerging insights in the prominent role that assembly of the cortical cytoskeletal scaffold plays in the process of daughter parasite formation.
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Affiliation(s)
| | - Josh R. Beck
- University of California Los Angeles, Department of Microbiology, Immunology and Molecular Genetics, Los Angeles, CA 90095, USA
| | - Chun-Ti Chen
- Boston College, Department of Biology, Chestnut Hill, MA 02467, USA
| | - Markus Meissner
- Division of Infection and Immunity, Institute of Biomedical Life Sciences, Wellcome Centre for Molecular Parasitology, Glasgow Biomedical Research Centre, University of Glasgow, 120 University Place, Glasgow G12 8TA, UK
| | - Peter J. Bradley
- University of California Los Angeles, Department of Microbiology, Immunology and Molecular Genetics, Los Angeles, CA 90095, USA
| | - Marc-Jan Gubbels
- Boston College, Department of Biology, Chestnut Hill, MA 02467, USA
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SPM1 stabilizes subpellicular microtubules in Toxoplasma gondii. EUKARYOTIC CELL 2011; 11:206-16. [PMID: 22021240 DOI: 10.1128/ec.05161-11] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
We have identified two novel proteins that colocalize with the subpellicular microtubules in the protozoan parasite Toxoplasma gondii and named these proteins SPM1 and SPM2. These proteins have basic isoelectric points and both have homologs in other apicomplexan parasites. SPM1 contains six tandem copies of a 32-amino-acid repeat, whereas SPM2 lacks defined protein signatures. Alignment of Toxoplasma SPM2 with apparent Plasmodium SPM2 homologs indicates that the greatest degree of conservation lies in the carboxy-terminal half of the protein. Analysis of Plasmodium homologs of SPM1 indicates that while the central 32-amino-acid repeats have expanded to different degrees (7, 8, 9, 12, or 13 repeats), the amino- and carboxy-terminal regions remain conserved. In contrast, although the Cryptosporidium SPM1 homolog has a conserved carboxy tail, the five repeats are considerably diverged, and it has a smaller amino-terminal domain. SPM1 is localized along the full length of the subpellicular microtubules but does not associate with the conoid or spindle microtubules. SPM2 has a restricted localization along the middle region of the subpellicular microtubules. Domain deletion analysis indicates that four or more copies of the SPM1 repeat are required for localization to microtubules, and the amino-terminal 63 residues of SPM2 are required for localization to the subpellicular microtubules. Gene deletion studies indicate that neither SPM1 nor SPM2 is essential for tachyzoite viability. However, loss of SPM1 decreases overall parasite fitness and eliminates the stability of subpellicular microtubules to detergent extraction.
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Anderson-White BR, Ivey FD, Cheng K, Szatanek T, Lorestani A, Beckers CJ, Ferguson DJP, Sahoo N, Gubbels MJ. A family of intermediate filament-like proteins is sequentially assembled into the cytoskeleton of Toxoplasma gondii. Cell Microbiol 2011; 13:18-31. [PMID: 20698859 DOI: 10.1111/j.1462-5822.2010.01514.x] [Citation(s) in RCA: 132] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The intracellular protozoan parasite Toxoplasma gondii divides by a unique process of internal budding that involves the assembly of two daughter cells within the mother. The cytoskeleton of Toxoplasma, which is composed of microtubules associated with an inner membrane complex (IMC), has an important role in this process. The IMC, which is directly under the plasma membrane, contains a set of flattened membranous sacs lined on the cytoplasmic side by a network of filamentous proteins. This network contains a family of intermediate filament-like proteins or IMC proteins. In order to elucidate the division process, we have characterized a 14-member subfamily of Toxoplasma IMC proteins that share a repeat motif found in proteins associated with the cortical alveoli in all alveolates. By creating fluorescent protein fusion reporters for the family members we determined the spatiotemporal patterns of all 14 IMC proteins through tachyzoite development. This revealed several distinct distribution patterns and some provide the basis for novel structural models such as the assembly of certain family members into the basal complex. Furthermore we identified IMC15 as an early marker of budding and, lastly, the dynamic patterns observed throughout cytokinesis provide a timeline for daughter parasite development and division.
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Tran JQ, de Leon JC, Li C, Huynh MH, Beatty W, Morrissette NS. RNG1 is a late marker of the apical polar ring in Toxoplasma gondii. Cytoskeleton (Hoboken) 2010; 67:586-98. [PMID: 20658557 DOI: 10.1002/cm.20469] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
The asexually proliferating stages of apicomplexan parasites cause acute symptoms of diseases such as malaria, cryptosporidiosis and toxoplasmosis. These stages are characterized by the presence of two independent microtubule organizing centers (MTOCs). Centrioles are found at the poles of the intranuclear spindle. The apical polar ring (APR), a MTOC unique to apicomplexans, organizes subpellicular microtubules which impose cell shape and apical polarity on these protozoa. Here we describe the characteristics of a novel protein that localizes to the APR of Toxoplasma gondii which we have named ring-1 (RNG1). There are related RNG1 proteins in Neospora caninum and Sarcocystis neurona but no obvious homologs in Plasmodium spp., Cryptosporidium spp. or Babesia spp. RNG1 is a small, low-complexity, detergent-insoluble protein that assembles at the APR very late in the process of daughter parasite replication. We were unable to knock-out the RNG1 gene, suggesting that its gene product is essential. Tagged RNG1 lines have also allowed us to visualize the APR during growth of Toxoplasma in the microtubule-disrupting drug oryzalin. Oryzalin inhibits nuclear division and cytokinesis although Toxoplasma growth continues, and similar to earlier observations of unchecked centriole duplication in oryzalin-treated parasites, the APR continues to duplicate during aberrant parasite growth.
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Affiliation(s)
- Johnson Q Tran
- Department of Molecular Biology and Biochemistry, University of California, Irvine, 92697, USA
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Gaji RY, Behnke MS, Lehmann MM, White MW, Carruthers VB. Cell cycle-dependent, intercellular transmission of Toxoplasma gondii is accompanied by marked changes in parasite gene expression. Mol Microbiol 2010; 79:192-204. [PMID: 21166903 DOI: 10.1111/j.1365-2958.2010.07441.x] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Intracellular microbes have evolved efficient strategies for transitioning from one cell to another in a process termed intercellular transmission. Here we show that host cell transmission of the obligate intracellular parasite Toxoplasma gondii is closely tied to specific cell cycle distributions, with egress and reinvasion occurring most proficiently by parasites in the G1 phase. We also reveal that Toxoplasma undergoes marked changes in mRNA expression when transitioning from the extracellular environment to its intracellular niche. These mRNA level changes reflect a modal switch from expression of proteins involved in invasion, motility and signal transduction in extracellular parasites to expression of metabolic and DNA replication proteins in intracellular parasites. Host cell binding and signalling associated with the discharge of parasite secretory proteins was not sufficient to induce this switch in gene expression, suggesting that the regulatory mechanisms responsible are tied to the establishment of the intracellular environment. The genes whose expression increased after parasite invasion belong to a progressive cascade known to underlie the parasite division cycle indicating that the unique relationship between the G1 phase and invasion effectively synchronizes short-term population growth. This work provides new insight into how this highly successful parasite competently transits from cell to cell.
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Affiliation(s)
- Rajshekhar Y Gaji
- Department of Microbiology and Immunology, University of Michigan Medical School, 1150 W. Medical Center Dr., Ann Arbor, MI 48109, USA
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Lorestani A, Sheiner L, Yang K, Robertson SD, Sahoo N, Brooks CF, Ferguson DJP, Striepen B, Gubbels MJ. A Toxoplasma MORN1 null mutant undergoes repeated divisions but is defective in basal assembly, apicoplast division and cytokinesis. PLoS One 2010; 5:e12302. [PMID: 20808817 PMCID: PMC2924399 DOI: 10.1371/journal.pone.0012302] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2010] [Accepted: 07/27/2010] [Indexed: 01/08/2023] Open
Abstract
The membrane occupation and recognition nexus protein 1 (MORN1) is highly conserved among apicomplexan parasites and is associated with several structures that have a role in cell division. Here we dissected the role of MORN1 using the relatively simple budding process of Toxoplasma gondii as a model. Ablation of MORN1 in a conditional null mutant resulted in pronounced defects suggesting a central role for MORN1 in apicoplast segregation and in daughter cell budding. Lack of MORN1 resulted in double-headed parasites. These Janus-headed parasites form two complete apical complexes but fail to assemble a basal complex. Moreover, these parasites were capable of undergoing several more budding rounds resulting in the formation of up to 16-headed parasites conjoined at the basal end. Despite this segregation defect, the mother's cytoskeleton was completely disassembled in every budding round. Overall this argues that successful completion of the budding is not required for cell cycle progression. None of the known basal complex components, including a set of recently identified inner membrane complex (IMC) proteins, localized correctly in these multi-headed parasites. These data suggest that MORN1 is essential for assembly of the basal complex, and that lack of the basal complex abolishes the contractile capacity assigned to the basal complex late in daughter formation. Consistent with this hypothesis we observe that MORN1 mutants fail to efficiently constrict and divide the apicoplast. We used the null background provided by the mutant to dissect the function of subdomains of the MORN1 protein. This demonstrated that deletion of a single MORN domain already prevented the function of MORN1 whereas a critical role for the short linker between MORN domains 6 and 7 was identified. In conclusion, MORN1 is required for basal complex assembly and loss of MORN1 results in defects in apicoplast division and daughter segregation.
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Affiliation(s)
- Alexander Lorestani
- Department of Biology, Boston College, Chestnut Hill, Massachusetts, United States of America
| | - Lilach Sheiner
- Department of Cellular Biology and Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, Georgia, United States of America
| | - Kevin Yang
- Department of Biology, Boston College, Chestnut Hill, Massachusetts, United States of America
| | - Seth D. Robertson
- Department of Biology, Boston College, Chestnut Hill, Massachusetts, United States of America
| | - Nivedita Sahoo
- Department of Biology, Boston College, Chestnut Hill, Massachusetts, United States of America
| | - Carrie F. Brooks
- Department of Cellular Biology and Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, Georgia, United States of America
| | - David J. P. Ferguson
- Nuffield Department of Clinical Laboratory Science, University of Oxford, John Radcliffe Hospital, Oxford, United Kingdom
| | - Boris Striepen
- Department of Cellular Biology and Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, Georgia, United States of America
| | - Marc-Jan Gubbels
- Department of Biology, Boston College, Chestnut Hill, Massachusetts, United States of America
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3-Methyladenine blocks Toxoplasma gondii division prior to centrosome replication. Mol Biochem Parasitol 2010; 173:142-53. [PMID: 20609430 DOI: 10.1016/j.molbiopara.2010.05.020] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2009] [Revised: 05/21/2010] [Accepted: 05/25/2010] [Indexed: 11/22/2022]
Abstract
The apicomplexan Toxoplasma gondii replicates by endodyogeny, in which replicated organelles assemble into nascent daughter buds within the maternal parasite. The mechanisms governing this complex sequence are not understood. We now report that the kinase inhibitor 3-methlyadenine (3-MA) efficiently blocks T. gondii replication. The inhibition could not be attributed to the effects of 3-MA on mammalian phosphatidylinositol 3-kinase and host cell autophagy. Furthermore, we show that accumulation of host lysosomes around the parasitophorous vacuoles was unaffected. Most 3-MA-treated parasites failed to form daughter buds or replicate DNA, indicating arrest in G1 or early S-phase. Some 3-MA-treated parasites displayed abortive cell division, in which nuclear segregation to malformed daughter buds was incomplete or asymmetrical. Electron microscopy revealed the presence of residual body-like structures in many vacuoles, even in the absence of daughter buds. Most treated parasites had otherwise normal morphology and were able to resume replication upon drug removal. 3-MA-treated and control parasites were similar with respect to the extent of Golgi body division and apicoplast elongation; however, treated parasites rarely possessed replicated centrosomes or apicoplasts. These data are suggestive of a generalized blockade of T. gondii cell cycle progression at stages preceding centrosome replication, rather than arrest at a specific checkpoint. We hypothesize that 3-MA treatment triggers a cell cycle pause program that may serve to protect parasites during periods, such as subsequent to egress, when cell cycle progression might be deleterious. Elucidation of the mechanism of 3-MA inhibition may provide insight into the control of parasite growth.
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Morriswood B, He CY, Sealey-Cardona M, Yelinek J, Pypaert M, Warren G. The bilobe structure of Trypanosoma brucei contains a MORN-repeat protein. Mol Biochem Parasitol 2009; 167:95-103. [PMID: 19445968 DOI: 10.1016/j.molbiopara.2009.05.001] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2008] [Revised: 05/04/2009] [Accepted: 05/05/2009] [Indexed: 11/16/2022]
Abstract
The Golgi of the kinetoplastid parasite Trypanosoma brucei is closely apposed to a bilobe structure containing TbCentrin2 and TbCentrin4 in procyclic cells. However, both are additionally localized to the basal bodies. Here we report the characterization of a membrane occupation and recognition nexus (MORN)-repeat protein, TbMORN1, present at the bilobe but not at the basal body. The anterior part of the TbMORN1 structure partially overlapped with the flagellar attachment zone while the posterior part overlapped with the flagellar pocket. Depletion studies using RNAi showed that there was a modest growth inhibition in procyclic cells but lethality in bloodstream cells, showing that it is an essential protein in the bloodstream form of the organism. TbMORN1 appears to be a useful marker for the bilobe in T. brucei.
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Affiliation(s)
- Brooke Morriswood
- Max F. Perutz Laboratories, University of Vienna, Medical University of Vienna, Dr. Bohr-Gasse 9, A-1030 Vienna, Austria
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The cell cycle and Toxoplasma gondii cell division: tightly knit or loosely stitched? Int J Parasitol 2008; 38:1343-58. [PMID: 18703066 DOI: 10.1016/j.ijpara.2008.06.004] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2008] [Revised: 06/10/2008] [Accepted: 06/13/2008] [Indexed: 01/20/2023]
Abstract
The flexibility displayed by apicomplexan parasites to vary their mode of replication has intrigued biologists since their discovery by electron microscopy in the 1960s and 1970s. Starting in the 1990s we began to understand the cell biology of the cytoskeleton elements driving cytokinesis. By contrast, the molecular mechanisms that regulate the various division modes and how they translate into the budding process that uniquely characterizes this parasite family are much less understood. Although growth mechanisms are a neglected area of study, it is an important pathogenic parameter as fast division rounds are associated with fulminant infection whereas slower growth attenuates virulence, as is exploited in some vaccine strains. In this review we summarize a recent body of cell biological experiments that are rapidly leading to an understanding of the events that yield successful mitosis and cytokinesis in Toxoplasma. We place these observations within a cell cycle context with comments on how these events may be regulated by known eukaryotic checkpoints active in fission and budding yeasts as well as mammalian cells. The presence of cell cycle control mechanisms in the Apicomplexa is supported by our findings that identify several cell cycle checkpoints in Toxoplasma. The progress of the cell cycle is ultimately controlled by cyclin-Cdk pair activities, which are present throughout the Apicomplexa. Although many of the known controllers of cyclin-Cdk activity are present, several key controls cannot readily be identified, suggesting that apicomplexan parasites deviate at these points from the higher eukaryotic models. Altogether, new insights in Toxoplasma replication are reciprocally applied to hypothesize how other division modes in the Toxoplasma life cycle and in other Apicomplexa species could be controlled in terms of cell cycle checkpoint regulation.
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Abstract
The protozoan phylum Apicomplexa encompasses approximately 5000 species of obligate intracellular parasites, including those responsible for malaria and toxoplasmosis. Rather than dividing by binary fission, apicomplexans use a remarkable mechanism for replication, assembling daughters de novo within the cytoplasm. Here, we exploit time-lapse microscopy of fluorescent markers targeted to various subcellular structures in Toxoplasma gondii tachyzoites to determine how these unicellular eukaryotes efficiently package a complete set of organelles, maintaining the highly polarized organization necessary for host cell invasion and pathogenesis. Golgi division and elongation of the apicoplast are among the first morphologically observable events, associated with an unusual pattern of centriolar migration. Daughter parasites are assembled on cytoskeletal scaffolding, whose growth proceeds from the apical end, first encapsulating the divided Golgi. Further extension of the cytoskeletal scaffold results in partitioning of the apicoplast, nucleus, endoplasmic reticulum, and finally the mitochondrion, which enters the developing daughters rapidly, but only very late during the division cycle. The specialized secretory organelles (micronemes and rhoptries) form de novo. This distinctive pattern of replication -- in which organellar segregation spans approximately 75% of the cell cycle, completely encompassing S phase -- suggests an unusual mechanism of cell cycle regulation.
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Affiliation(s)
- Manami Nishi
- Departments of Biology, and Cell and Developmental Biology, University of Pennsylvania, Philadelphia PA 19104, USA
| | | | - John M. Murray
- Departments of Biology, and Cell and Developmental Biology, University of Pennsylvania, Philadelphia PA 19104, USA
| | - David S. Roos
- Departments of Biology, and Cell and Developmental Biology, University of Pennsylvania, Philadelphia PA 19104, USA
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Struck NS, Herrmann S, Schmuck-Barkmann I, de Souza Dias S, Haase S, Cabrera AL, Treeck M, Bruns C, Langer C, Cowman AF, Marti M, Spielmann T, Gilberger TW. Spatial dissection of the cis- and trans-Golgi compartments in the malaria parasite Plasmodium falciparum. Mol Microbiol 2008; 67:1320-30. [DOI: 10.1111/j.1365-2958.2008.06125.x] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
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MORN1 has a conserved role in asexual and sexual development across the apicomplexa. EUKARYOTIC CELL 2008; 7:698-711. [PMID: 18310354 DOI: 10.1128/ec.00021-08] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The gene encoding the membrane occupation and recognition nexus protein MORN1 is conserved across the Apicomplexa. In Toxoplasma gondii, MORN1 is associated with the spindle poles, the anterior and posterior rings of the inner membrane complex (IMC). The present study examines the localization of MORN1 during the coccidian development of T. gondii and three Eimeria species (in the definitive host) and erythrocytic schizogony of Plasmodium falciparum. During asexual proliferation, MORN1 is associated with the posterior ring of the IMCs of the multiple daughters forming during T. gondii endopolygeny and schizogony in Eimeria and P. falciparum. Furthermore, the expression of P. falciparum MORN1 protein peaked in late schizogony. These data fit a model with a conserved role for MORN1 during IMC assembly in all variations of asexual development. An important new observation is the reactivity of MORN1 antibody with certain sexual stages in T. gondii and Eimeria species. Here MORN1 is organized as a ring-like structure where the microgametes bud from the microgametocyte while in mature microgametes it is present near the flagellar basal bodies and mitochondrion. These observations suggest a conserved role for MORN1 in both asexual and sexual development across the Apicomplexa.
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