1
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Hvorecny KL, Sladewski TE, De La Cruz EM, Kollman JM, Heaslip AT. Toxoplasma gondii actin filaments are tuned for rapid disassembly and turnover. Nat Commun 2024; 15:1840. [PMID: 38418447 PMCID: PMC10902351 DOI: 10.1038/s41467-024-46111-3] [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: 09/11/2023] [Accepted: 02/14/2024] [Indexed: 03/01/2024] Open
Abstract
The cytoskeletal protein actin plays a critical role in the pathogenicity of the intracellular parasite, Toxoplasma gondii, mediating invasion and egress, cargo transport, and organelle inheritance. Advances in live cell imaging have revealed extensive filamentous actin networks in the Apicomplexan parasite, but there are conflicting data regarding the biochemical and biophysical properties of Toxoplasma actin. Here, we imaged the in vitro assembly of individual Toxoplasma actin filaments in real time, showing that native, unstabilized filaments grow tens of microns in length. Unlike skeletal muscle actin, Toxoplasma filaments intrinsically undergo rapid treadmilling due to a high critical concentration, fast monomer dissociation, and rapid nucleotide exchange. Cryo-EM structures of jasplakinolide-stabilized and native (i.e. unstabilized) filaments show an architecture like skeletal actin, with differences in assembly contacts in the D-loop that explain the dynamic nature of the filament, likely a conserved feature of Apicomplexan actin. This work demonstrates that evolutionary changes at assembly interfaces can tune the dynamic properties of actin filaments without disrupting their conserved structure.
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Affiliation(s)
- Kelli L Hvorecny
- Department of Biochemistry, University of Washington, Seattle, WA, USA
| | - Thomas E Sladewski
- Department of Department of Molecular and Cell Biology, University of Connecticut, Storrs, CT, USA
| | - Enrique M De La Cruz
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT, USA
| | - Justin M Kollman
- Department of Biochemistry, University of Washington, Seattle, WA, USA.
| | - Aoife T Heaslip
- Department of Department of Molecular and Cell Biology, University of Connecticut, Storrs, CT, USA.
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2
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Ribeiro R, Costa L, Pinto E, Sousa E, Fernandes C. Therapeutic Potential of Marine-Derived Cyclic Peptides as Antiparasitic Agents. Mar Drugs 2023; 21:609. [PMID: 38132930 PMCID: PMC10745025 DOI: 10.3390/md21120609] [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: 11/02/2023] [Revised: 11/18/2023] [Accepted: 11/23/2023] [Indexed: 12/23/2023] Open
Abstract
Parasitic diseases still compromise human health. Some of the currently available therapeutic drugs have limitations considering their adverse effects, questionable efficacy, and long treatment, which have encouraged drug resistance. There is an urgent need to find new, safe, effective, and affordable antiparasitic drugs. Marine-derived cyclic peptides have been increasingly screened as candidates for developing new drugs. Therefore, in this review, a systematic analysis of the scientific literature was performed and 25 marine-derived cyclic peptides with antiparasitic activity (1-25) were found. Antimalarial activity is the most reported (51%), followed by antileishmanial (27%) and antitrypanosomal (20%) activities. Some compounds showed promising antiparasitic activity at the nM scale, being active against various parasites. The mechanisms of action and targets for some of the compounds have been investigated, revealing different strategies against parasites.
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Affiliation(s)
- Ricardo Ribeiro
- Laboratório de Química Orgânica e Farmacêutica, Departamento de Ciências Químicas, Faculdade de Farmácia, Universidade do Porto, Rua de Jorge Viterbo Ferreira, 228, 4050-313 Porto, Portugal; (R.R.); (L.C.); (E.S.)
- Interdisciplinary Centre of Marine and Environmental Research (CIIMAR), Edifício do Terminal de Cruzeiros do Porto de Leixões, Av. General Norton de Matos s/n, 4050-208 Matosinhos, Portugal;
| | - Lia Costa
- Laboratório de Química Orgânica e Farmacêutica, Departamento de Ciências Químicas, Faculdade de Farmácia, Universidade do Porto, Rua de Jorge Viterbo Ferreira, 228, 4050-313 Porto, Portugal; (R.R.); (L.C.); (E.S.)
| | - Eugénia Pinto
- Interdisciplinary Centre of Marine and Environmental Research (CIIMAR), Edifício do Terminal de Cruzeiros do Porto de Leixões, Av. General Norton de Matos s/n, 4050-208 Matosinhos, Portugal;
- Laboratório de Microbiologia, Departamento de Ciências Biológicas, Faculdade de Farmácia, Universidade do Porto, Rua de Jorge Viterbo Ferreira 228, 4050-313 Porto, Portugal
| | - Emília Sousa
- Laboratório de Química Orgânica e Farmacêutica, Departamento de Ciências Químicas, Faculdade de Farmácia, Universidade do Porto, Rua de Jorge Viterbo Ferreira, 228, 4050-313 Porto, Portugal; (R.R.); (L.C.); (E.S.)
- Interdisciplinary Centre of Marine and Environmental Research (CIIMAR), Edifício do Terminal de Cruzeiros do Porto de Leixões, Av. General Norton de Matos s/n, 4050-208 Matosinhos, Portugal;
| | - Carla Fernandes
- Laboratório de Química Orgânica e Farmacêutica, Departamento de Ciências Químicas, Faculdade de Farmácia, Universidade do Porto, Rua de Jorge Viterbo Ferreira, 228, 4050-313 Porto, Portugal; (R.R.); (L.C.); (E.S.)
- Interdisciplinary Centre of Marine and Environmental Research (CIIMAR), Edifício do Terminal de Cruzeiros do Porto de Leixões, Av. General Norton de Matos s/n, 4050-208 Matosinhos, Portugal;
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3
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Hvorecny KL, Sladewski TE, De La Cruz EM, Kollman JM, Heaslip AT. Toxoplasma gondii actin filaments are tuned for rapid disassembly and turnover. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.08.29.555340. [PMID: 37693530 PMCID: PMC10491163 DOI: 10.1101/2023.08.29.555340] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/12/2023]
Abstract
The cytoskeletal protein actin plays a critical role in the pathogenicity of Toxoplasma gondii, mediating invasion and egress, cargo transport, and organelle inheritance. Advances in live cell imaging have revealed extensive filamentous actin networks in the Apicomplexan parasite, but there is conflicting data regarding the biochemical and biophysical properties of Toxoplasma actin. Here, we imaged the in vitro assembly of individual Toxoplasma actin filaments in real time, showing that native, unstabilized filaments grow tens of microns in length. Unlike skeletal muscle actin, Toxoplasma filaments intrinsically undergo rapid treadmilling due to a high critical concentration, fast monomer dissociation, and rapid nucleotide exchange. Cryo-EM structures of stabilized and unstabilized filaments show an architecture like skeletal actin, with differences in assembly contacts in the D-loop that explain the dynamic nature of the filament, likely a conserved feature of Apicomplexan actin. This work demonstrates that evolutionary changes at assembly interfaces can tune dynamic properties of actin filaments without disrupting their conserved structure.
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Affiliation(s)
- Kelli L Hvorecny
- Department of Biochemistry, University of Washington, Seattle, WA, USA
| | - Thomas E Sladewski
- Department of Department of Molecular and Cell Biology, University of Connecticut, Storrs, Connecticut, USA
| | - Enrique M De La Cruz
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520
| | - Justin M Kollman
- Department of Biochemistry, University of Washington, Seattle, WA, USA
| | - Aoife T Heaslip
- Department of Department of Molecular and Cell Biology, University of Connecticut, Storrs, Connecticut, USA
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4
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Rivera Fernández N, Mondragón Castelán M, González Pozos S, Ramírez Flores CJ, Mondragón González R, Gómez de León CT, Castro Elizalde KN, Marrero Ponce Y, Arán VJ, Martins Alho MA, Mondragón Flores R. A new type of quinoxalinone derivatives affects viability, invasion, and intracellular growth of Toxoplasma gondii tachyzoites in vitro. Parasitol Res 2016; 115:2081-96. [PMID: 26888289 DOI: 10.1007/s00436-016-4953-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2015] [Accepted: 02/04/2016] [Indexed: 12/11/2022]
Abstract
Quinoxalinone derivatives, identified as VAM2 compounds (7-nitroquinoxalin-2-ones), were evaluated against Toxoplasma gondii tachyzoites of the RH strain. The VAM2 compounds were previously synthesized based on the design obtained from an in silico prediction with the software TOMOCOMD-CARDD. From the ten VAM2 drugs tested, several showed a deleterious effect on tachyzoites. However, VAM2-2 showed the highest toxoplasmicidal activity generating a remarkable decrease in tachyzoite viability (in about 91 %) and a minimal alteration in the host cell. An evident inhibition of host cell invasion by tachyzoites previously treated with VAM2-2 was observed in a dose-dependent manner. In addition, remarkable alterations were observed in the pellicle parasite, such as swelling, roughness, and blebbing. Toxoplasma motility was inhibited, and subpellicular cytoskeleton integrity was altered, inducing a release of its components to the soluble fraction. VAM2-2 showed a clear and specific deleterious effect on tachyzoites viability, structural integrity, and invasive capabilities with limited effects in host cells morphology and viability. VAM2-2 minimum inhibitory concentration (MIC50) was determined as 3.3 μM ± 1.8. Effects of quinoxalinone derivatives on T. gondii provide the basis for a future therapeutical alternative in the treatment of toxoplasmosis.
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Affiliation(s)
- Norma Rivera Fernández
- Departamento de Microbiología y Parasitología, Facultad de Medicina, Universidad Nacional Autónoma de México, Coyoacán 04510, DF, México
- Departamento de Bioquímica, Centro de Investigación y de Estudios Avanzados del IPN (CINVESTAV), Avenida IPN No 2508 Delegación Gustavo A Madero, 07360, DF, México
| | - Mónica Mondragón Castelán
- Departamento de Bioquímica, Centro de Investigación y de Estudios Avanzados del IPN (CINVESTAV), Avenida IPN No 2508 Delegación Gustavo A Madero, 07360, DF, México
| | | | - Carlos J Ramírez Flores
- Departamento de Bioquímica, Centro de Investigación y de Estudios Avanzados del IPN (CINVESTAV), Avenida IPN No 2508 Delegación Gustavo A Madero, 07360, DF, México
| | | | - Carmen T Gómez de León
- Departamento de Bioquímica, Centro de Investigación y de Estudios Avanzados del IPN (CINVESTAV), Avenida IPN No 2508 Delegación Gustavo A Madero, 07360, DF, México
| | - Kitzia N Castro Elizalde
- Departamento de Bioquímica, Centro de Investigación y de Estudios Avanzados del IPN (CINVESTAV), Avenida IPN No 2508 Delegación Gustavo A Madero, 07360, DF, México
| | - Yovani Marrero Ponce
- Edificio de Especialidades Médicas, Hospital de los Valles, Colegio de Ciencias de la Salud, Universidad de San Francisco de Quito, Av. Interoceánica Km 12 1/2 Cumbayá, Quito, Ecuador
| | - Vicente J Arán
- Instituto de Química Médica, CSIC, c/ Juan de la Cierva 3, 28006, Madrid, España
| | - Miriam A Martins Alho
- Instituto de Química Médica, CSIC, c/ Juan de la Cierva 3, 28006, Madrid, España
- Centro de Investigaciones en Hidratos de Carbono (CIHIDECAR-CONICET), Departamento de Química Orgánica, FCEN y LabMOr - INTECIN, FI, UBA, Paseo Colón 850, 5to. Piso, CP C1063ACV, Buenos Aires, Argentina
| | - Ricardo Mondragón Flores
- Departamento de Bioquímica, Centro de Investigación y de Estudios Avanzados del IPN (CINVESTAV), Avenida IPN No 2508 Delegación Gustavo A Madero, 07360, DF, México.
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5
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Gliding motility in apicomplexan parasites. Semin Cell Dev Biol 2015; 46:135-42. [DOI: 10.1016/j.semcdb.2015.09.020] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2015] [Accepted: 09/25/2015] [Indexed: 11/22/2022]
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6
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Salamun J, Kallio JP, Daher W, Soldati-Favre D, Kursula I. Structure of Toxoplasma gondii coronin, an actin-binding protein that relocalizes to the posterior pole of invasive parasites and contributes to invasion and egress. FASEB J 2014; 28:4729-47. [PMID: 25114175 DOI: 10.1096/fj.14-252569] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Coronins are involved in the regulation of actin dynamics in a multifaceted way, participating in cell migration and vesicular trafficking. Apicomplexan parasites, which exhibit an actin-dependent gliding motility that is essential for traversal through tissues, as well as invasion of and egress from host cells, express only a single coronin, whereas higher eukaryotes possess several isoforms. We set out to characterize the 3-D structure, biochemical function, subcellular localization, and genetic ablation of Toxoplasma gondii coronin (TgCOR), to shed light on its biological role. A combination of X-ray crystallography, small-angle scattering of X-rays, and light scattering revealed the atomic structure of the conserved WD40 domain and the dimeric arrangement of the full-length protein. TgCOR binds to F-actin and increases the rate and extent of actin polymerization. In vivo, TgCOR relocalizes transiently to the posterior pole of motile and invading parasites, independent of actin dynamics, but concomitant to microneme secretory organelle discharge. TgCOR contributes to, but is not essential for, invasion and egress. Taken together, our data point toward a role for TgCOR in stabilizing newly formed, short filaments and F-actin cross-linking, as well as functions linked to endocytosis and recycling of membranes.
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Affiliation(s)
- Julien Salamun
- Department of Microbiology and Molecular Medicine, Faculty of Medicine, University of Geneva, Geneva, Switzerland
| | - Juha P Kallio
- Centre for Structural Systems Biology, Helmholtz Centre for Infection Research and German Electron Synchrotron (DESY), Hamburg, Germany; and
| | - Wassim Daher
- Department of Microbiology and Molecular Medicine, Faculty of Medicine, University of Geneva, Geneva, Switzerland
| | - Dominique Soldati-Favre
- Department of Microbiology and Molecular Medicine, Faculty of Medicine, University of Geneva, Geneva, Switzerland;
| | - Inari Kursula
- Centre for Structural Systems Biology, Helmholtz Centre for Infection Research and German Electron Synchrotron (DESY), Hamburg, Germany; and Faculty of Biochemistry and Molecular Medicine, University of Oulu, Oulu, Finland
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7
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Ma C, Diraviyam K, Maier ME, Sept D, Sibley LD. Synthetic chondramide A analogues stabilize filamentous actin and block invasion by Toxoplasma gondii. JOURNAL OF NATURAL PRODUCTS 2013; 76:1565-1572. [PMID: 24020843 PMCID: PMC3787807 DOI: 10.1021/np400196w] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/07/2013] [Indexed: 05/31/2023]
Abstract
Apicomplexan parasites such as Toxoplasma gondii rely on actin-based motility to cross biological barriers and invade host cells. Key structural and biochemical differences in host and parasite actins make this an attractive target for small-molecule inhibitors. Here we took advantage of recent advances in the synthesis of cyclic depsipeptide compounds that stabilize filamentous actin to test the ability of chondramides to disrupt growth of T. gondii in vitro. Structural modeling of chondramide A (2) binding to an actin filament model revealed variations in the binding site between host and parasite actins. A series of 10 previously synthesized analogues (2b-k) with substitutions in the β-tyrosine moiety blocked parasite growth on host cell monolayers with EC₅₀ values that ranged from 0.3 to 1.3 μM. In vitro polymerization assays using highly purified recombinant actin from T. gondii verified that synthetic and natural product chondramides target the actin cytoskeleton. Consistent with this, chondramide treatment blocked parasite invasion into host cells and was more rapidly effective than pyrimethamine, a standard therapeutic agent. Although the current compounds lack specificity for parasite vs host actin, these studies provide a platform for the future design and synthesis of synthetic cyclic peptide inhibitors that selectively disrupt actin dynamics in parasites.
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Affiliation(s)
- Christopher
I. Ma
- Department
of Molecular Microbiology, Washington University
School of Medicine, St. Louis, Missouri 63110, United States
| | - Karthikeyan Diraviyam
- Department
of Biomedical Engineering and Center for Computational Medicine and
Bioinformatics, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Martin E. Maier
- Institut
für Organische Chemie, Universität
Tübingen, 72076 Tübingen, Germany
| | - David Sept
- Department
of Biomedical Engineering and Center for Computational Medicine and
Bioinformatics, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - L. David Sibley
- Department
of Molecular Microbiology, Washington University
School of Medicine, St. Louis, Missouri 63110, United States
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8
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Azevedo E, Oliveira LT, Castro Lima AK, Terra R, Dutra PML, Salerno VP. Interactions between Leishmania braziliensis and Macrophages Are Dependent on the Cytoskeleton and Myosin Va. J Parasitol Res 2012; 2012:275436. [PMID: 22792440 PMCID: PMC3391898 DOI: 10.1155/2012/275436] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2012] [Revised: 05/06/2012] [Accepted: 05/07/2012] [Indexed: 11/18/2022] Open
Abstract
Leishmaniasis is a neglected tropical disease with no effective vaccines. Actin, microtubules and the actin-based molecular motor myosin Va were investigated for their involvement in Leishmania braziliensis macrophage interactions. Results showed a decrease in the association index when macrophages were without F-actin or microtubules regardless of the activation state of the macrophage. In the absence of F-actin, the production of NO in non-activated cells increased, while in activated cells, the production of NO was reduced independent of parasites. The opposite effect of an increased NO production was observed in the absence of microtubules. In activated cells, the loss of cytoskeletal components inhibited the release of IL-10 during parasite interactions. The production of IL-10 also decreased in the absence of actin or microtubules in non-activated macrophages. Only the disruption of actin altered the production of TNF-α in activated macrophages. The expression of myosin Va tail resulted in an acute decrease in the association index between transfected macrophages and L. braziliensis promastigotes. These data reveal the importance of F-actin, microtubules, and myosin-Va suggesting that modulation of the cytoskeleton may be a mechanism used by L. braziliensis to overcome the natural responses of macrophages to establish infections.
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Affiliation(s)
- Elisama Azevedo
- Laboratório de Imunologia e Bioquímica de Protozoários, Departamento de Microbiologia, Imunologia e Parasitologia, FCM, UERJ, Avenida Professor Manuel de Abreu 444 5° andar. Vila Isabel, 20550-170 Rio de Janeiro, RJ, Brazil
- Programa de Pós-Graduação em Microbiologia Médica, Faculdade de Ciências Médicas, UERJ, 20550-170 Rio de Janerio, RJ, Brazil
| | - Leandro Teixeira Oliveira
- Departamento Biociências, Escola de Educação Física e Desportos, Universidade Federal do Rio de Janeiro, 21941-599 Rio de Janerio, RJ, Brazil
| | - Ana Karina Castro Lima
- Laboratório de Imunologia e Bioquímica de Protozoários, Departamento de Microbiologia, Imunologia e Parasitologia, FCM, UERJ, Avenida Professor Manuel de Abreu 444 5° andar. Vila Isabel, 20550-170 Rio de Janeiro, RJ, Brazil
- Programa de Pós-Graduação em Microbiologia Médica, Faculdade de Ciências Médicas, UERJ, 20550-170 Rio de Janerio, RJ, Brazil
| | - Rodrigo Terra
- Laboratório de Imunologia e Bioquímica de Protozoários, Departamento de Microbiologia, Imunologia e Parasitologia, FCM, UERJ, Avenida Professor Manuel de Abreu 444 5° andar. Vila Isabel, 20550-170 Rio de Janeiro, RJ, Brazil
- Programa de Pós-Graduação em Biodinâmica do Movimento, EEFD, UFRJ, 21941-599 Rio de Janerio, RJ, Brazil
| | - Patrícia Maria Lourenço Dutra
- Laboratório de Imunologia e Bioquímica de Protozoários, Departamento de Microbiologia, Imunologia e Parasitologia, FCM, UERJ, Avenida Professor Manuel de Abreu 444 5° andar. Vila Isabel, 20550-170 Rio de Janeiro, RJ, Brazil
| | - Verônica P. Salerno
- Departamento Biociências, Escola de Educação Física e Desportos, Universidade Federal do Rio de Janeiro, 21941-599 Rio de Janerio, RJ, Brazil
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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 DOI: 10.1016/b978-0-12-394309-5.00001-8] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [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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Sattler JM, Ganter M, Hliscs M, Matuschewski K, Schüler H. Actin regulation in the malaria parasite. Eur J Cell Biol 2011; 90:966-71. [DOI: 10.1016/j.ejcb.2010.11.011] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2010] [Revised: 11/22/2010] [Accepted: 11/23/2010] [Indexed: 10/18/2022] Open
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11
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Evolutionarily divergent, unstable filamentous actin is essential for gliding motility in apicomplexan parasites. PLoS Pathog 2011; 7:e1002280. [PMID: 21998582 PMCID: PMC3188518 DOI: 10.1371/journal.ppat.1002280] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2011] [Accepted: 08/17/2011] [Indexed: 01/05/2023] Open
Abstract
Apicomplexan parasites rely on a novel form of actin-based motility called gliding, which depends on parasite actin polymerization, to migrate through their hosts and invade cells. However, parasite actins are divergent both in sequence and function and only form short, unstable filaments in contrast to the stability of conventional actin filaments. The molecular basis for parasite actin filament instability and its relationship to gliding motility remain unresolved. We demonstrate that recombinant Toxoplasma (TgACTI) and Plasmodium (PfACTI and PfACTII) actins polymerized into very short filaments in vitro but were induced to form long, stable filaments by addition of equimolar levels of phalloidin. Parasite actins contain a conserved phalloidin-binding site as determined by molecular modeling and computational docking, yet vary in several residues that are predicted to impact filament stability. In particular, two residues were identified that form intermolecular contacts between different protomers in conventional actin filaments and these residues showed non-conservative differences in apicomplexan parasites. Substitution of divergent residues found in TgACTI with those from mammalian actin resulted in formation of longer, more stable filaments in vitro. Expression of these stabilized actins in T. gondii increased sensitivity to the actin-stabilizing compound jasplakinolide and disrupted normal gliding motility in the absence of treatment. These results identify the molecular basis for short, dynamic filaments in apicomplexan parasites and demonstrate that inherent instability of parasite actin filaments is a critical adaptation for gliding motility.
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12
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Yadav R, Pathak PP, Shukla VK, Jain A, Srivastava S, Tripathi S, Krishna Pulavarti SVSR, Mehta S, Sibley LD, Arora A. Solution structure and dynamics of ADF from Toxoplasma gondii. J Struct Biol 2011; 176:97-111. [PMID: 21820516 DOI: 10.1016/j.jsb.2011.07.011] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2011] [Revised: 07/13/2011] [Accepted: 07/19/2011] [Indexed: 12/01/2022]
Abstract
Toxoplasma gondii ADF (TgADF) belongs to a functional subtype characterized by strong G-actin sequestering activity and low F-actin severing activity. Among the characterized ADF/cofilin proteins, TgADF has the shortest length and is missing a C-terminal helix implicated in F-actin binding. In order to understand its characteristic properties, we have determined the solution structure of TgADF and studied its backbone dynamics from ¹⁵N-relaxation measurements. TgADF has conserved ADF/cofilin fold consisting of a central mixed β-sheet comprised of six β-strands that are partially surrounded by three α-helices and a C-terminal helical turn. The high G-actin sequestering activity of TgADF relies on highly structurally and dynamically optimized interactions between G-actin and G-actin binding surface of TgADF. The equilibrium dissociation constant for TgADF and rabbit muscle G-actin was 23.81 nM, as measured by ITC, which reflects very strong affinity of TgADF and G-actin interactions. The F-actin binding site of TgADF is partially formed, with a shortened F-loop that does not project out of the ellipsoid structure and a C-terminal helical turn in place of the C-terminal helix α4. Yet, it is more rigid than the F-actin binding site of Leishmania donovani cofilin. Experimental observations and structural features do not support the interaction of PIP2 with TgADF, and PIP2 does not affect the interaction of TgADF with G-actin. Overall, this study suggests that conformational flexibility of G-actin binding sites enhances the affinity of TgADF for G-actin, while conformational rigidity of F-actin binding sites of conventional ADF/cofilins is necessary for stable binding to F-actin.
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Affiliation(s)
- Rahul Yadav
- Molecular and Structural Biology Division, CSIR-Central Drug Research Institute, Lucknow 226001, India
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13
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Mehta S, Sibley LD. Actin depolymerizing factor controls actin turnover and gliding motility in Toxoplasma gondii. Mol Biol Cell 2011; 22:1290-9. [PMID: 21346192 PMCID: PMC3078074 DOI: 10.1091/mbc.e10-12-0939] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Actin-based motility is vital for host cell invasion by protozoan parasites such as Toxoplasma, which provides a model for studying actin-based motility in parasites. Our study reveals that, in addition to intrinsic differences in actin dynamics, regulatory proteins like actin depolymerizing factor are required to regulate this process in vivo. Apicomplexan parasites rely on actin-based gliding motility to move across the substratum, cross biological barriers, and invade their host cells. Gliding motility depends on polymerization of parasite actin filaments, yet ∼98% of actin is nonfilamentous in resting parasites. Previous studies suggest that the lack of actin filaments in the parasite is due to inherent instability, leaving uncertain the role of actin-binding proteins in controlling dynamics. We have previously shown that the single allele of Toxoplasma gondii actin depolymerizing factor (TgADF) has strong actin monomer–sequestering and weak filament-severing activities in vitro. Here we used a conditional knockout strategy to investigate the role of TgADF in vivo. Suppression of TgADF led to accumulation of actin-rich filaments that were detected by immunofluorescence and electron microscopy. Parasites deficient in TgADF showed reduced speed of motility, increased aberrant patterns of motion, and inhibition of sustained helical gliding. Lack of TgADF also led to severe defects in entry and egress from host cells, thus blocking infection in vitro. These studies establish that the absence of stable actin structures in the parasite are not simply the result of intrinsic instability, but that TgADF is required for the rapid turnover of parasite actin filaments, gliding motility, and cell invasion.
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Affiliation(s)
- Simren Mehta
- Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, MO 63110, USA
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14
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Schmitz S, Schaap IAT, Kleinjung J, Harder S, Grainger M, Calder L, Rosenthal PB, Holder AA, Veigel C. Malaria parasite actin polymerization and filament structure. J Biol Chem 2010; 285:36577-85. [PMID: 20826799 PMCID: PMC2978586 DOI: 10.1074/jbc.m110.142638] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2010] [Revised: 09/02/2010] [Indexed: 11/06/2022] Open
Abstract
A novel form of acto-myosin regulation has been proposed in which polymerization of new actin filaments regulates motility of parasites of the apicomplexan class of protozoa. In vivo and in vitro parasite F-actin is very short and unstable, but the structural basis and details of filament dynamics remain unknown. Here, we show that long actin filaments can be obtained by polymerizing unlabeled rabbit skeletal actin (RS-actin) onto both ends of the short rhodamine-phalloidin-stabilized Plasmodium falciparum actin I (Pf-actin) filaments. Following annealing, hybrid filaments of micron length and "zebra-striped" appearance are observed by fluorescence microscopy that are stable enough to move over myosin class II motors in a gliding filament assay. Using negative stain electron microscopy we find that pure Pf-actin stabilized by jasplakinolide (JAS) also forms long filaments, indistinguishable in length from RS-actin filaments, and long enough to be characterized structurally. To compare structures in near physiological conditions in aqueous solution we imaged Pf-actin and RS-actin filaments by atomic force microscopy (AFM). We found the monomer stacking to be distinctly different for Pf-actin compared with RS-actin, such that the pitch of the double helix of Pf-actin filaments was 10% larger. Our results can be explained by a rotational angle between subunits that is larger in the parasite compared with RS-actin. Modeling of the AFM data using high-resolution actin filament models supports our interpretation of the data. The structural differences reported here may be a consequence of weaker inter- and intra-strand contacts, and may be critical for differences in filament dynamics and for regulation of parasite motility.
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Affiliation(s)
| | | | | | - Simone Harder
- From the Division of Physical Biochemistry
- the Division of Parasitology, National Institute for Medical Research, Mill Hill, London NW7 1AA, United Kingdom
| | - Munira Grainger
- the Division of Parasitology, National Institute for Medical Research, Mill Hill, London NW7 1AA, United Kingdom
| | | | | | - Anthony A. Holder
- the Division of Parasitology, National Institute for Medical Research, Mill Hill, London NW7 1AA, United Kingdom
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15
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Holzinger A. Jasplakinolide: an actin-specific reagent that promotes actin polymerization. Methods Mol Biol 2010; 586:71-87. [PMID: 19768425 DOI: 10.1007/978-1-60761-376-3_4] [Citation(s) in RCA: 88] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Jasplakinolide, a cyclo-depsipeptide is a commonly used actin filament polymerizing and stabilizing drug. The substance has originally been isolated from a marine sponge, and can now be synthesized and has become commercially available. This, together with the benefit that jasplakinolide is membrane permeable has made it a commonly used tool in cell biology, when actin filament stabilization or polymerization has to be achieved. This may either be the case in studies on morphogenesis, motility, organelle movement, or when apoptosis has to be induced. Its use as a potent anticancer drug is discussed. The direct action on actin filaments may have further consequences in golgi body and membrane raft protein organization. In this chapter, the visualization of jasplaklinolide effects by different fluorescent and transmission electron microscopic methods is described. As competitive binding capacities of jasplakinolide and phalloidin make the detection of actin filaments by fluorescently labeled phalloidin problematic, alternatives are given here.
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Affiliation(s)
- Andreas Holzinger
- Institute of Botany, Department of Physiology and Cell Physiology, University of Innsbruck, Innsbruck, Austria
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16
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Hegge S, Munter S, Steinbüchel M, Heiss K, Engel U, Matuschewski K, Frischknecht F. Multistep adhesion of
Plasmodium
sporozoites. FASEB J 2010; 24:2222-34. [DOI: 10.1096/fj.09-148700] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Stephan Hegge
- Department of ParasitologyHygiene InstituteUniversity of Heidelberg Medical SchoolHeidelbergGermany
| | - Sylvia Munter
- Department of ParasitologyHygiene InstituteUniversity of Heidelberg Medical SchoolHeidelbergGermany
| | - Marion Steinbüchel
- Department of ParasitologyHygiene InstituteUniversity of Heidelberg Medical SchoolHeidelbergGermany
| | - Kirsten Heiss
- Department of ParasitologyHygiene InstituteUniversity of Heidelberg Medical SchoolHeidelbergGermany
| | | | - Kai Matuschewski
- Department of ParasitologyHygiene InstituteUniversity of Heidelberg Medical SchoolHeidelbergGermany
| | - Friedrich Frischknecht
- Department of ParasitologyHygiene InstituteUniversity of Heidelberg Medical SchoolHeidelbergGermany
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17
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Mehta S, Sibley LD. Toxoplasma gondii actin depolymerizing factor acts primarily to sequester G-actin. J Biol Chem 2009; 285:6835-47. [PMID: 20042603 DOI: 10.1074/jbc.m109.068155] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Toxoplasma gondii is a protozoan parasite belonging to the phylum Apicomplexa. Parasites in this phylum utilize a unique process of motility termed gliding, which is dependent on parasite actin filaments. Surprisingly, 98% of parasite actin is maintained as G-actin, suggesting that filaments are rapidly assembled and turned over. Little is known about the regulated disassembly of filaments in the Apicomplexa. In higher eukaryotes, the related actin depolymerizing factor (ADF) and cofilin proteins are essential regulators of actin filament turnover. ADF is one of the few actin-binding proteins conserved in apicomplexan parasites. In this study we examined the mechanism by which T. gondii ADF (TgADF) regulates actin filament turnover. Unlike other members of the ADF/cofilin (AC) family, apicomplexan ADFs lack key F-actin binding sites. Surprisingly, this promotes their enhanced disassembly of actin filaments. Restoration of the C-terminal F-actin binding site to TgADF stabilized its interaction with filaments but reduced its net filament disassembly activity. Analysis of severing activity revealed that TgADF is a weak severing protein, requiring much higher concentrations than typical AC proteins. Investigation of TgADF interaction with T. gondii actin (TgACT) revealed that TgADF disassembled short TgACT oligomers. Kinetic and steady-state polymerization assays demonstrated that TgADF has strong monomer-sequestering activity, inhibiting TgACT polymerization at very low concentrations. Collectively these data indicate that TgADF promoted the efficient turnover of actin filaments via weak severing of filaments and strong sequestering of monomers. This suggests a dual role for TgADF in maintaining high G-actin concentrations and effecting rapid filament turnover.
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Affiliation(s)
- Simren Mehta
- Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri 63110, USA
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18
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Frénal K, Soldati-Favre D. Role of the parasite and host cytoskeleton in apicomplexa parasitism. Cell Host Microbe 2009; 5:602-11. [PMID: 19527887 DOI: 10.1016/j.chom.2009.05.013] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2009] [Revised: 05/22/2009] [Accepted: 05/28/2009] [Indexed: 11/25/2022]
Abstract
The phylum Apicomplexa includes a large and diverse group of obligate intracellular parasites that rely on actomyosin-based motility to migrate, enter host cells, and egress from infected cells. To ensure their intracellular survival and replication, the apicomplexans have evolved sophisticated strategies for subversion of the host cytoskeleton. Given the properties in common between the host and parasite cytoskeleton, dissecting their individual contribution to the establishment of parasitic infection has been challenging. Nevertheless, recent studies have provided new insights into the mechanisms by which parasites subvert the dynamic properties of host actin and tubulin to promote their entry, development, and egress.
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Affiliation(s)
- Karine Frénal
- Department of Microbiology and Molecular Medicine, CMU, University of Geneva, 1 rue Michel-Servet, 1211 Geneva 4, Switzerland.
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19
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Liu WT, Ng J, Meluzzi D, Bandeira N, Gutierrez M, Simmons TL, Schultz AW, Linington RG, Moore BS, Gerwick WH, Pevzner PA, Dorrestein PC. Interpretation of tandem mass spectra obtained from cyclic nonribosomal peptides. Anal Chem 2009; 81:4200-9. [PMID: 19413302 PMCID: PMC2765223 DOI: 10.1021/ac900114t] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Natural and non-natural cyclic peptides are a crucial component in drug discovery programs because of their considerable pharmaceutical properties. Cyclosporin, microcystins, and nodularins are all notable pharmacologically important cyclic peptides. Because these biologically active peptides are often biosynthesized nonribosomally, they often contain nonstandard amino acids, thus increasing the complexity of the resulting tandem mass spectrometry data. In addition, because of the cyclic nature, the fragmentation patterns of many of these peptides showed much higher complexity when compared to related counterparts. Therefore, at the present time it is still difficult to annotate cyclic peptides MS/MS spectra. In this current work, an annotation program was developed for the annotation and characterization of tandem mass spectra obtained from cyclic peptides. This program, which we call MS-CPA is available as a web tool (http://lol.ucsd.edu/ms-cpa_v1/Input.py). Using this program, we have successfully annotated the sequence of representative cyclic peptides, such as seglitide, tyrothricin, desmethoxymajusculamide C, dudawalamide A, and cyclomarins, in a rapid manner and also were able to provide the first-pass structure evidence of a newly discovered natural product based on predicted sequence. This compound is not available in sufficient quantities for structural elucidation by other means such as NMR. In addition to the development of this cyclic annotation program, it was observed that some cyclic peptides fragmented in unexpected ways resulting in the scrambling of sequences. In summary, MS-CPA not only provides a platform for rapid confirmation and annotation of tandem mass spectrometry data obtained with cyclic peptides but also enables quantitative analysis of the ion intensities. This program facilitates cyclic peptide analysis, sequencing, and also acts as a useful tool to investigate the uncommon fragmentation phenomena of cyclic peptides and aids the characterization of newly discovered cyclic peptides encountered in drug discovery programs.
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Affiliation(s)
- Wei-Ting Liu
- Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, CA 92093-0636, USA
| | - Julio Ng
- Department of Computer Science and Engineering, University of California, San Diego, La Jolla, CA 92093-0404, USA
| | - Dario Meluzzi
- Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, CA 92093-0636, USA
| | - Nuno Bandeira
- Department of Computer Science and Engineering, University of California, San Diego, La Jolla, CA 92093-0404, USA
| | - Marcelino Gutierrez
- Center for Marine Biotechnology and Biomedicine, Scripps Institution of Oceanography, University of California, San Diego, La Jolla, California 92093-0204, USA
| | - Thomas L. Simmons
- Center for Marine Biotechnology and Biomedicine, Scripps Institution of Oceanography, University of California, San Diego, La Jolla, California 92093-0204, USA
| | - Andrew W. Schultz
- Center for Marine Biotechnology and Biomedicine, Scripps Institution of Oceanography, University of California, San Diego, La Jolla, California 92093-0204, USA
| | - Roger G. Linington
- Department of Chemistry and Biochemistry, University of California, Santa Cruz, Santa Cruz, CA 95064 USA
| | - Bradley S. Moore
- Center for Marine Biotechnology and Biomedicine, Scripps Institution of Oceanography, University of California, San Diego, La Jolla, California 92093-0204, USA
- Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California at San Diego, La Jolla, CA 92093-0636, USA
| | - William H. Gerwick
- Center for Marine Biotechnology and Biomedicine, Scripps Institution of Oceanography, University of California, San Diego, La Jolla, California 92093-0204, USA
- Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California at San Diego, La Jolla, CA 92093-0636, USA
| | - Pavel A. Pevzner
- Department of Computer Science and Engineering, University of California, San Diego, La Jolla, CA 92093-0404, USA
| | - Pieter C. Dorrestein
- Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, CA 92093-0636, USA
- Center for Marine Biotechnology and Biomedicine, Scripps Institution of Oceanography, University of California, San Diego, La Jolla, California 92093-0204, USA
- Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California at San Diego, La Jolla, CA 92093-0636, USA
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20
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Lazarus MD, Schneider TG, Taraschi TF. A new model for hemoglobin ingestion and transport by the human malaria parasite Plasmodium falciparum. J Cell Sci 2008; 121:1937-49. [PMID: 18477610 PMCID: PMC5105679 DOI: 10.1242/jcs.023150] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
The current model for hemoglobin ingestion and transport by intraerythrocytic Plasmodium falciparum malaria parasites shares similarities with endocytosis. However, the model is largely hypothetical, and the mechanisms responsible for the ingestion and transport of host cell hemoglobin to the lysosome-like food vacuole (FV) of the parasite are poorly understood. Because actin dynamics play key roles in vesicle formation and transport in endocytosis, we used the actin-perturbing agents jasplakinolide and cytochalasin D to investigate the role of parasite actin in hemoglobin ingestion and transport to the FV. In addition, we tested the current hemoglobin trafficking model through extensive analysis of serial thin sections of parasitized erythrocytes (PE) by electron microscopy. We find that actin dynamics play multiple, important roles in the hemoglobin transport pathway, and that hemoglobin delivery to the FV via the cytostomes might be required for parasite survival. Evidence is provided for a new model, in which hemoglobin transport to the FV occurs by a vesicle-independent process.
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Affiliation(s)
- Michelle D. Lazarus
- Department of Pathology, Anatomy, and Cell Biology, Thomas Jefferson University, Philadelphia, PA 19107, USA
| | - Timothy G. Schneider
- Department of Pathology, Anatomy, and Cell Biology, Thomas Jefferson University, Philadelphia, PA 19107, USA
| | - Theodore F. Taraschi
- Department of Pathology, Anatomy, and Cell Biology, Thomas Jefferson University, Philadelphia, PA 19107, USA
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21
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Plattner F, Yarovinsky F, Romero S, Didry D, Carlier MF, Sher A, Soldati-Favre D. Toxoplasma profilin is essential for host cell invasion and TLR11-dependent induction of an interleukin-12 response. Cell Host Microbe 2008; 3:77-87. [PMID: 18312842 DOI: 10.1016/j.chom.2008.01.001] [Citation(s) in RCA: 261] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2007] [Revised: 11/14/2007] [Accepted: 01/08/2008] [Indexed: 11/24/2022]
Abstract
Apicomplexan parasites exhibit actin-dependent gliding motility that is essential for migration across biological barriers and host cell invasion. Profilins are key contributors to actin polymerization, and the parasite Toxoplasma gondii possesses a profilin-like protein that is recognized by Toll-like receptor TLR11 in the host innate immune system. Here, we show by conditional disruption of the corresponding gene that T.gondii profilin, while not required for intracellular growth, is indispensable for gliding motility, host cell invasion, active egress from host cells, and virulence in mice. Furthermore, parasites lacking profilin are unable to induce TLR11-dependent production in vitro and in vivo of the defensive host cytokine interleukin-12. Thus, profilin is an essential element of two aspects of T. gondii infection. Like bacterial flagellin, profilin plays a role in motility while serving as a microbial ligand recognized by the host innate immune system.
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Affiliation(s)
- Fabienne Plattner
- Department of Microbiology and Molecular Medicine, CMU, University of Geneva, 1 rue Michel-Servet, 1211 Geneva 4, Switzerland
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22
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Schüler H, Matuschewski K. Regulation of apicomplexan microfilament dynamics by a minimal set of actin-binding proteins. Traffic 2006; 7:1433-9. [PMID: 17010119 DOI: 10.1111/j.1600-0854.2006.00484.x] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Efficient and rapid host cell invasion is a prerequisite for an intracellular parasitic life style. Pathogens typically induce receptor-mediated endocytosis and hijack the force-transducing system of a host cell to gain access to a replication-competent niche. In striking contrast, apicomplexan parasites such as Plasmodium, the causative agent of malaria, and the human and animal pathogens Toxoplasma and Cryptosporidium employ their own actomyosin motor machinery to propel themselves into prospective host cells. Understanding the regulation and dynamics of actin-based motility of these parasites is therefore central to understanding their pathogenesis. The parasite genomes harbour surprisingly few potential actin-regulatory proteins indicating that a basic repertoire meets the requirements to regulate actin dynamics. In this article, we summarize our current knowledge of Plasmodium microfilament dynamics and describe its potential players.
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Affiliation(s)
- Herwig Schüler
- Max Delbrück Center for Molecular Medicine, Berlin 13125, Germany.
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23
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Heintzelman MB. Cellular and Molecular Mechanics of Gliding Locomotion in Eukaryotes. INTERNATIONAL REVIEW OF CYTOLOGY 2006; 251:79-129. [PMID: 16939778 DOI: 10.1016/s0074-7696(06)51003-4] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Gliding is a form of substrate-dependent cell locomotion exploited by a variety of disparate cell types. Cells may glide at rates well in excess of 1 microm/sec and do so without the gross distortion of cellular form typical of amoeboid crawling. In the absence of a discrete locomotory organelle, gliding depends upon an assemblage of molecules that links cytoplasmic motor proteins to the cell membrane and thence to the appropriate substrate. Gliding has been most thoroughly studied in the apicomplexan parasites, including Plasmodium and Toxoplasma, which employ a unique assortment of proteins dubbed the glideosome, at the heart of which is a class XIV myosin motor. Actin and myosin also drive the gliding locomotion of raphid diatoms (Bacillariophyceae) as well as the intriguing form of gliding displayed by the spindle-shaped cells of the primitive colonial protist Labyrinthula. Chlamydomonas and other flagellated protists are also able to abandon their more familiar swimming locomotion for gliding, during which time they recruit a motility apparatus independent of that driving flagellar beating.
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Affiliation(s)
- Matthew B Heintzelman
- Department of Biology, Program in Cell Biology and Biochemistry, Bucknell University, Lewisburg, PA 17837, USA
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24
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Gordon JL, Sibley LD. Comparative genome analysis reveals a conserved family of actin-like proteins in apicomplexan parasites. BMC Genomics 2005; 6:179. [PMID: 16343347 PMCID: PMC1334187 DOI: 10.1186/1471-2164-6-179] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2005] [Accepted: 12/12/2005] [Indexed: 01/24/2023] Open
Abstract
Background The phylum Apicomplexa is an early-branching eukaryotic lineage that contains a number of important human and animal pathogens. Their complex life cycles and unique cytoskeletal features distinguish them from other model eukaryotes. Apicomplexans rely on actin-based motility for cell invasion, yet the regulation of this system remains largely unknown. Consequently, we focused our efforts on identifying actin-related proteins in the recently completed genomes of Toxoplasma gondii, Plasmodium spp., Cryptosporidium spp., and Theileria spp. Results Comparative genomic and phylogenetic studies of apicomplexan genomes reveals that most contain only a single conventional actin and yet they each have 8–10 additional actin-related proteins. Among these are a highly conserved Arp1 protein (likely part of a conserved dynactin complex), and Arp4 and Arp6 homologues (subunits of the chromatin-remodeling machinery). In contrast, apicomplexans lack canonical Arp2 or Arp3 proteins, suggesting they lost the Arp2/3 actin polymerization complex on their evolutionary path towards intracellular parasitism. Seven of these actin-like proteins (ALPs) are novel to apicomplexans. They show no phylogenetic associations to the known Arp groups and likely serve functions specific to this important group of intracellular parasites. Conclusion The large diversity of actin-like proteins in apicomplexans suggests that the actin protein family has diverged to fulfill various roles in the unique biology of intracellular parasites. Conserved Arps likely participate in vesicular transport and gene expression, while apicomplexan-specific ALPs may control unique biological traits such as actin-based gliding motility.
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Affiliation(s)
- Jennifer L Gordon
- Department of Molecular Microbiology, Washington University, School of Medicine, 660 S. Euclid Ave. St, Louis, MO, USA
| | - L David Sibley
- Department of Molecular Microbiology, Washington University, School of Medicine, 660 S. Euclid Ave. St, Louis, MO, USA
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25
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Sahoo N, Beatty W, Heuser J, Sept D, Sibley LD. Unusual kinetic and structural properties control rapid assembly and turnover of actin in the parasite Toxoplasma gondii. Mol Biol Cell 2005; 17:895-906. [PMID: 16319175 PMCID: PMC1356598 DOI: 10.1091/mbc.e05-06-0512] [Citation(s) in RCA: 102] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Toxoplasma is a protozoan parasite in the phylum Apicomplexa, which contains a number of medically important parasites that rely on a highly unusual form of motility termed gliding to actively penetrate their host cells. Parasite actin filaments regulate gliding motility, yet paradoxically filamentous actin is rarely detected in these parasites. To investigate the kinetics of this unusual parasite actin, we expressed TgACT1 in baculovirus and purified it to homogeneity. Biochemical analysis showed that Toxoplasma actin (TgACT1) rapidly polymerized into filaments at a critical concentration that was 3-4-fold lower than conventional actins, yet it failed to copolymerize with mammalian actin. Electron microscopic analysis revealed that TgACT1 filaments were 10 times shorter and less stable than rabbit actin. Phylogenetic comparison of actins revealed a limited number of apicomplexan-specific residues that likely govern the unusual behavior of parasite actin. Molecular modeling identified several key alterations that affect interactions between monomers and that are predicted to destabilize filaments. Our findings suggest that conserved molecular differences in parasite actin favor rapid cycles of assembly and disassembly that govern the unusual form of gliding motility utilized by apicomplexans.
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Affiliation(s)
- Nivedita Sahoo
- Department of Molecular Microbiology, Center for Infectious Diseases, Washington University School of Medicine, St. Louis, MO 63110, USA
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26
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Canton DA, Litchfield DW. The shape of things to come: an emerging role for protein kinase CK2 in the regulation of cell morphology and the cytoskeleton. Cell Signal 2005; 18:267-75. [PMID: 16126370 DOI: 10.1016/j.cellsig.2005.07.008] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2005] [Revised: 07/04/2005] [Accepted: 07/18/2005] [Indexed: 01/24/2023]
Abstract
Protein kinase CK2 is a highly conserved, pleiotropic, protein serine/threonine kinase that is essential for life in eukaryotes. CK2 has been implicated in diverse cellular processes such as cell cycle regulation, circadian rhythms, apoptosis, transformation and tumorigenesis. In addition, there is increasing evidence that CK2 is involved in the maintenance of cell morphology and cell polarity, and in the regulation of the actin and tubulin cytoskeletons. Accordingly, this review will highlight published evidence in experimental models ranging from yeast to mammals documenting the emerging roles of protein kinase CK2 in the regulation of cell polarity, cell morphology and the cytoskeleton.
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Affiliation(s)
- David A Canton
- Regulatory Biology and Functional Genomics Group, Siebens-Drake Medical Research Institute, Department of Biochemistry, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario, Canada N6A 5C1
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27
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Patrón S A, Mondragón M, González S, Ambrosio JR, Guerrero B AL, Mondragón R. Identification and purification of actin from the subpellicular network of Toxoplasma gondii tachyzoites. Int J Parasitol 2005; 35:883-94. [PMID: 15970197 DOI: 10.1016/j.ijpara.2005.03.016] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2005] [Revised: 03/22/2005] [Accepted: 03/31/2005] [Indexed: 11/16/2022]
Abstract
Toxoplasma gondii infects cells through dynamic events dependent on actin. Although the presence of cortical actin has been widely suggested, visualisation and localisation of actin filaments has not been reported. The subpellicular cytoskeleton network is a recently described structure possibly involved in the dynamic events. Using non-ionic detergent extractions, the cortical cytoskeleton network was enriched and used for the isolation and identification of actin. Actin was detected by Western blots in extracts of cytoskeleton networks, and it was localised by gold staining in the network and in both the apical end and the posterior polar ring. Actin was isolated from subpellicular cytoskeleton extracts by binding to DNase I, and it polymerised in vitro as filaments that were gold-decorated by a monoclonal anti-actin antibody. Filaments bound the subfragment 1 of heavy meromyosin, although with atypical arrangements in comparison with the arrowheads observed in muscle actin filaments. Treatment with cytochalasin D and colchicine altered the structural organisation of the subpellicular network indicating the participation of actin filaments and microtubules in the maintenance of its structure. Actin filaments and microtubules, in the subpellicular network, participate reciprocally in the maintaining of the parasite's shape and the gliding motility.
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Affiliation(s)
- Araceli Patrón S
- Departamento de Bioquímica, Centro de Investigación y Estudios Avanzados del IPN. Av. Instituto Politécnico Nacional No 2508. Col. Sn Pedro Zacatenco, Del. Gustavo A. Madero., México
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28
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Schmitz S, Grainger M, Howell S, Calder LJ, Gaeb M, Pinder JC, Holder AA, Veigel C. Malaria Parasite Actin Filaments are Very Short. J Mol Biol 2005; 349:113-25. [PMID: 15876372 DOI: 10.1016/j.jmb.2005.03.056] [Citation(s) in RCA: 119] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2005] [Revised: 03/17/2005] [Accepted: 03/21/2005] [Indexed: 11/19/2022]
Abstract
A novel form of actomyosin regulation has recently been proposed in which the polymerisation of new actin filaments regulates apicomplexan parasite motility. Here, we identified actin I in the merozoites of Plasmodium falciparum by mass spectrometry. The only post-translational modification is acetylation of the N terminus (acetyl-Gly-Glu-actin), while methylation of histidine 73, a common modification for actin, is absent. Results obtained with anti-actin antibodies suggest that, in contrast to a previous report, there is no actin-ubiquitin conjugate in merozoites. About half of the extracted monomeric actin polymerised and actin filaments could be sedimented at 500,000g. In contrast, centrifugation at 100,000g, conditions commonly used to sediment filamentous actin, yielded very little F-actin. In a functional characterisation using an in vitro motility assay, actin filaments moved over myosin at a velocity indistinguishable from that of rabbit skeletal actin. Filament length, however, was too short to be resolved by conventional fluorescence microscopy. On electron micrographs an average filament length of approximately 100nm was determined. We also identified by mass spectrometry proteins co-purifying with filamentous actin, which are potential actin-binding proteins. Our results demonstrate differences in actin filament dynamics for an apicomplexan parasite, which could be due to specific properties of the actin and/or actin-regulatory proteins.
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Affiliation(s)
- Stephan Schmitz
- Division of Physical Biochemistry, National Institute for Medical Research, The Ridgeway, Mill Hill, London NW7 1AA, UK.
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29
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Seabra SH, de Souza W, Damatta RA. Toxoplasma gondii exposes phosphatidylserine inducing a TGF-β1 autocrine effect orchestrating macrophage evasion. Biochem Biophys Res Commun 2004; 324:744-52. [PMID: 15474490 DOI: 10.1016/j.bbrc.2004.09.114] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2004] [Indexed: 11/16/2022]
Abstract
Toxoplasmosis is a worldwide disease caused by Toxoplasma gondii. Activated macrophages control T. gondii growth by nitric oxide (NO) production. However, T. gondii active invasion inhibits NO production, allowing parasite persistence. Here we show that the mechanism used by T. gondii to inhibit NO production persisting in activated macrophages depends on phosphatidylserine (PS) exposure. Masking PS with annexin-V on parasites or activated macrophages abolished NO production inhibition and parasite persistence. NO production inhibition depended on a transforming growth factor-beta1 (TGF-beta1) autocrine effect confirmed by the expression of Smad 2 and 3 in infected macrophages. TGF-beta1 led to inducible nitric oxide synthase (iNOS) degradation, actin filament (F-actin) depolymerization, and lack of nuclear factor-kappaB (NF-kappaB) in the nucleus. All these features were reverted by TGF-beta1 neutralizing antibody treatment. Thus, T. gondii mimics the evasion mechanism used by Leishmania amazonensis and also the anti-inflammatory response evoked by apoptotic cells.
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Affiliation(s)
- Sergio H Seabra
- Laboratório de Biologia Celular e Tecidual, Centro de Biociências e Biotecnologia, Universidade Estadual do Norte Fluminense, 28013-600 Campos dos Goytacazes, RJ, Brazil
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Abstract
Motility is a characteristic of most living organisms and often requires specialized structures like cilia or flagella. An alternative is amoeboid movement, where the polymerization/depolymerization of actin leads to the formation of pseudopodia, filopodia and/or lamellipodia that enable the cell to crawl along a surface. Despite their lack of locomotive organelles and in absence of cell deformation, members of the apicomplexan parasites employ a unique form of locomotion called gliding motility to promote their migration across biological barriers and to power host-cell invasion and egress. Detailed studies in Toxoplasma gondii and Plasmodium species have revealed that this unique mode of movement is dependent on a myosin of class XIV and necessitates actin dynamics and the concerted discharge and processing of adhesive proteins. Gliding is essential for the survival and infectivity of these obligate intracellular parasites, which cause severe disease in humans and animals.
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Affiliation(s)
- Dominique Soldati
- Department of Biological Sciences, Imperial College London, Sir Alexander Fleming Building, South Kensington Campus, London UK, SW7 2AZ.
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31
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Delorme V, Cayla X, Faure G, Garcia A, Tardieux I. Actin dynamics is controlled by a casein kinase II and phosphatase 2C interplay on Toxoplasma gondii Toxofilin. Mol Biol Cell 2003; 14:1900-12. [PMID: 12802063 PMCID: PMC165085 DOI: 10.1091/mbc.e02-08-0462] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Actin polymerization in Apicomplexa protozoa is central to parasite motility and host cell invasion. Toxofilin has been characterized as a protein that sequesters actin monomers and caps actin filaments in Toxoplasma gondii. Herein, we show that Toxofilin properties in vivo as in vitro depend on its phosphorylation. We identify a novel parasitic type 2C phosphatase that binds the Toxofilin/G-actin complex and a casein kinase II-like activity in the cytosol, both of which modulate the phosphorylation status of Toxofilin serine53. The interplay of these two molecules controls Toxofilin binding of G-actin as well as actin dynamics in vivo. Such functional interactions should play a major role in actin sequestration, a central feature of actin dynamics in Apicomplexa that underlies the spectacular speed and nature of parasite gliding motility.
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Affiliation(s)
- Violaine Delorme
- Departement des Maladies Infectieuses, Centre National de la Recherche Scientifique Unité Mixte Recherche 8104, Institut Cochin, 75014 Paris, France
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Wetzel DM, Håkansson S, Hu K, Roos D, Sibley LD. Actin filament polymerization regulates gliding motility by apicomplexan parasites. Mol Biol Cell 2003; 14:396-406. [PMID: 12589042 PMCID: PMC149980 DOI: 10.1091/mbc.e02-08-0458] [Citation(s) in RCA: 143] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Host cell entry by Toxoplasma gondii depends critically on actin filaments in the parasite, yet paradoxically, its actin is almost exclusively monomeric. In contrast to the absence of stable filaments in conventional samples, rapid-freeze electron microscopy revealed that actin filaments were formed beneath the plasma membrane of gliding parasites. To investigate the role of actin filaments in motility, we treated parasites with the filament-stabilizing drug jasplakinolide (JAS) and monitored the distribution of actin in live and fixed cells using yellow fluorescent protein (YFP)-actin. JAS treatment caused YFP-actin to redistribute to the apical and posterior ends, where filaments formed a spiral pattern subtending the plasma membrane. Although previous studies have suggested that JAS induces rigor, videomicroscopy demonstrated that JAS treatment increased the rate of parasite gliding by approximately threefold, indicating that filaments are rate limiting for motility. However, JAS also frequently reversed the normal direction of motility, disrupting forward migration and cell entry. Consistent with this alteration, subcortical filaments in JAS-treated parasites occurred in tangled plaques as opposed to the straight, roughly parallel orientation observed in control cells. These studies reveal that precisely controlled polymerization of actin filaments imparts the correct timing, duration, and directionality of gliding motility in the Apicomplexa.
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Affiliation(s)
- D M Wetzel
- Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri 63110, USA
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Bergman LW, Kaiser K, Fujioka H, Coppens I, Daly TM, Fox S, Matuschewski K, Nussenzweig V, Kappe SHI. Myosin A tail domain interacting protein (MTIP) localizes to the inner membrane complex of Plasmodium sporozoites. J Cell Sci 2003; 116:39-49. [PMID: 12456714 DOI: 10.1242/jcs.00194] [Citation(s) in RCA: 156] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Apicomplexan host cell invasion and gliding motility depend on the parasite's actomyosin system located beneath the plasma membrane of invasive stages. Myosin A (MyoA), a class XIV unconventional myosin, is the motor protein. A model has been proposed to explain how the actomyosin motor operates but little is known about the components, topology and connectivity of the motor complex. Using the MyoA neck and tail domain as bait in a yeast two-hybrid screen we identified MTIP, a novel 24 kDa protein that interacts with MyoA. Deletion analysis shows that the 15 amino-acid C-terminal tail domain of MyoA, rather than the neck domain, specifically interacts with MTIP. In Plasmodium sporozoites MTIP localizes to the inner membrane complex (IMC), where it is found clustered with MyoA. The data support a model for apicomplexan motility and invasion in which the MyoA motor protein is associated via its tail domain with MTIP, immobilizing it at the outer IMC membrane. The head domain of the immobilized MyoA moves actin filaments that, directly or via a bridging protein, connect to the cytoplasmic domain of a transmembrane protein of the TRAP family. The actin/TRAP complex is then redistributed by the stationary MyoA from the anterior to the posterior end of the zoite, leading to its forward movement on a substrate or to penetration of a host cell.
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Affiliation(s)
- Lawrence W Bergman
- Division of Molecular Parasitology, Department of Microbiology & Immunology, Drexel University College of Medicine, Philadelphia, PA 19129, USA.
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Delorme V, Garcia A, Cayla X, Tardieux I. A role for Toxoplasma gondii type 1 ser/thr protein phosphatase in host cell invasion. Microbes Infect 2002; 4:271-8. [PMID: 11909736 DOI: 10.1016/s1286-4579(02)01538-1] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Host cell invasion by Toxoplasma gondii tachyzoites relies on many coordinated processes. The tachyzoite participates in invasion by providing an actomyosin-dependent force driving it into the nascent parasitophorous vacuole as well as by releasing molecules which contribute to the vacuole membrane. Exposure to type 1/2A protein phosphatase inhibitors, okadaic acid (OA) or tautomycin significantly impairs tachyzoite invasiveness. Furthermore, the tachyzoite extract contains a biochemically active type 1, but not a type 2A, serine-threonine protein phosphatase, which is immunologically related to eukaryotic phosphatase type 1 catalytic subunit. When tachyzoite extracts are incubated with a monoclonal antibody reactive to human type 1 catalytic subunit, other T. gondii molecules are coprecipitated among which one competes with the inhibitory toxin OA. Finally, in vitro phosphate labelling assays indicate that the biochemically characterized PP1 activity controls the phosphorylation of several proteins. Taken together, these data strongly suggest that the type 1 phosphatase activity detected in invasive tachyzoites is implicated in the control of the host cell invasion process.
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Affiliation(s)
- Violaine Delorme
- Institut Cochin de génétique moléculaire, CNRS-UPR 415, 22, rue Méchain, 75014 Paris, France
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Abstract
The Apicomplexa are a phylum of diverse obligate intracellular parasites including Plasmodium spp., the cause of malaria; Toxoplasma gondii and Cryptosporidium parvum, opportunistic pathogens of immunocompromised individuals; and Eimeria spp. and Theileria spp., parasites of considerable agricultural importance. These protozoan parasites share distinctive morphological features, cytoskeletal organization, and modes of replication, motility, and invasion. This review summarizes our current understanding of the cytoskeletal elements, the properties of cytoskeletal proteins, and the role of the cytoskeleton in polarity, motility, invasion, and replication. We discuss the unusual properties of actin and myosin in the Apicomplexa, the highly stereotyped microtubule populations in apicomplexans, and a network of recently discovered novel intermediate filament-like elements in these parasites.
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Affiliation(s)
- Naomi S Morrissette
- Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
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Brown PJ, Gill AC, Nugent PG, McVey JH, Tomley FM. Domains of invasion organelle proteins from apicomplexan parasites are homologous with the Apple domains of blood coagulation factor XI and plasma pre-kallikrein and are members of the PAN module superfamily. FEBS Lett 2001; 497:31-8. [PMID: 11376658 DOI: 10.1016/s0014-5793(01)02424-3] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Micronemes are specialised organelles, found in all apicomplexan parasites, which secrete molecules that are essential for parasite attachment to and invasion of host cells. Regions of several microneme proteins have sequence similarity to the Apple domains (A-domains) of blood coagulation factor XI (FXI) and plasma pre-kallikrein (PK). We have used mass spectrometry on a recombinant-expressed, putative A-domain from the microneme protein EtMIC5 from Eimeria tenella, to demonstrate that three intramolecular disulphide bridges are formed. These bridges are analogous to those that stabilise A-domains in FXI and PK. The data confirm that the apicomplexan domains are structural homologues of A-domains and are therefore novel members of the PAN module superfamily, which also includes the N-terminal domains of members of the plasminogen/hepatocyte growth factor family. The role of A-domains/PAN modules in apicomplexan parasites is not known, but their presence in the microneme suggests that they may be important for mediating protein-protein or protein-carbohydrate interactions during parasite attachment and host cell invasion.
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Affiliation(s)
- P J Brown
- Institute for Animal Health, Compton Laboratory, Compton, Newbury, Berkshire RG20 7NN, UK
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37
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Abstract
Apicomplexa constitute one of the largest phyla of protozoa. Most Apicomplexa, including those pathogenic to humans, are obligate intracellular parasites. Their extracellular forms, which are highly polarized and elongated cells, share two unique abilities: they glide on solid substrates without changing their shape and reach an intracellular compartment without active participation from the host cell. There is now ample ultrastructural evidence that these processes result from the backward movement of extracellular interactions along the anteroposterior axis of the parasite. Recent work in several Apicomplexa, including genetic studies in the Plasmodium sporozoite, has provided molecular support for this 'capping' model. It appears that the same machinery drives both gliding motility and host cell invasion. The cytoplasmic motor, a transmembrane bridge and surface ligands essential for cell invasion are conserved among the main apicomplexan pathogens.
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Affiliation(s)
- R Ménard
- Laboratoire de Biologie et Génétique du Paludisme, Institut Pasteur, Paris, France.
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Odaka C, Sanders ML, Crews P. Jasplakinolide induces apoptosis in various transformed cell lines by a caspase-3-like protease-dependent pathway. CLINICAL AND DIAGNOSTIC LABORATORY IMMUNOLOGY 2000; 7:947-52. [PMID: 11063504 PMCID: PMC95991 DOI: 10.1128/cdli.7.6.947-952.2000] [Citation(s) in RCA: 99] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
To clarify the mechanisms underlying the antiproliferative effects of jasplakinolide, a cyclic depsipeptide from marine sponges, we examined whether jasplakinolide induces apoptosis in a variety of transformed and nontransformed cells. Jasplakinolide inhibited proliferation of human Jurkat T cells, resulting in cell death. This was accompanied by chromatin condensation and DNA cleavage at the linker regions between the nucleosomes. When caspase-3-like activity in the cytosolic extracts of Jurkat T cells was examined with a fluorescent substrate, DEVD-MAC (N-acetyl-Asp-Glu-Val-Asp-4-methyl-coumaryl-7-amide), the activity in the cells treated with jasplakinolide was remarkably increased in a time-dependent manner. Pretreatment of Jurkat T cells with the caspase inhibitor zVAD [benzyloxycarbonyl(Cbz)-Val-Ala-beta-Asp(OMe)-fluoromethylketone] or DEVD-CHO (N-acetyl-Asp-Glu-Val-Asp-1-aldehyde) prevented the induction of apoptosis by jasplakinolide. Moreover, exposure of various murine transformed cell lines to jasplakinolide resulted in cell death, which was inhibited by zVAD. Although it has been well established that murine immature thymocytes are sensitive to apoptosis when exposed to various apoptotic stimuli, these cells as well as mature T lymphocytes were resistant to jasplakinolide-induced apoptosis. The results suggest that jasplakinolide induces apoptotic cell death through a caspase-3-like protease-dependent pathway. Another important outcome is that transformed cell lines were more susceptible to jasplakinolide-induced apoptosis than normal nontransformed cells.
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Affiliation(s)
- C Odaka
- Department of Bacterial and Blood Products, National Institute of Infectious Diseases, Tokyo, Japan.
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39
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Abstract
Toxoplasma gondii is an obligate intracellular pathogen within the phylum Apicomplexa. This protozoan parasite is one of the most widespread, with a broad host range including many birds and mammals and a geographic range that is nearly worldwide. While infection of healthy adults is usually relatively mild, serious disease can result in utero or when the host is immunocompromised. This sophisticated eukaryote has many specialized features that make it well suited to its intracellular lifestyle. In this review, we describe the current knowledge of how the asexual tachyzoite stage of Toxoplasma attaches to, invades, replicates in, and exits the host cell. Since this process is closely analogous to the way in which viruses reproduce, we refer to it as the Toxoplasma "lytic cycle."
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Affiliation(s)
- M W Black
- Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, California 94305-5124, USA
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Poupel O, Boleti H, Axisa S, Couture-Tosi E, Tardieux I. Toxofilin, a novel actin-binding protein from Toxoplasma gondii, sequesters actin monomers and caps actin filaments. Mol Biol Cell 2000; 11:355-68. [PMID: 10637313 PMCID: PMC14779 DOI: 10.1091/mbc.11.1.355] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Toxoplasma gondii relies on its actin cytoskeleton to glide and enter its host cell. However, T. gondii tachyzoites are known to display a strikingly low amount of actin filaments, which suggests that sequestration of actin monomers could play a key role in parasite actin dynamics. We isolated a 27-kDa tachyzoite protein on the basis of its ability to bind muscle G-actin and demonstrated that it interacts with parasite G-actin. Cloning and sequence analysis of the gene coding for this protein, which we named Toxofilin, showed that it is a novel actin-binding protein. In in vitro assays, Toxofilin not only bound to G-actin and inhibited actin polymerization as an actin-sequestering protein but also slowed down F-actin disassembly through a filament end capping activity. In addition, when green fluorescent protein-tagged Toxofilin was overexpressed in mammalian nonmuscle cells, the dynamics of actin stress fibers was drastically impaired, whereas green fluorescent protein-Toxofilin copurified with G-actin. Finally, in motile parasites, during gliding or host cell entry, Toxofilin was localized in the entire cytoplasm, including the rear end of the parasite, whereas in intracellular tachyzoites, especially before they exit from the parasitophorous vacuole of their host cell, Toxofilin was found to be restricted to the apical end.
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Affiliation(s)
- O Poupel
- Laboratoire de Biochimie et Biologie Moléculaire des Insectes, Unité de Recherche Associée, Centre National de la Recherche Scientifique 1960, 75724 Paris Cedex 15, France
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