1
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Quan JJ, Nikolov LA, Sha J, Wohlschlegel JA, Coppens I, Bradley PJ. Systematic characterization of all Toxoplasma gondii TBC domain-containing proteins identifies an essential regulator of Rab2 in the secretory pathway. PLoS Biol 2024; 22:e3002634. [PMID: 38713739 PMCID: PMC11101121 DOI: 10.1371/journal.pbio.3002634] [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: 06/04/2023] [Revised: 05/17/2024] [Accepted: 04/22/2024] [Indexed: 05/09/2024] Open
Abstract
Toxoplasma gondii resides in its intracellular niche by employing a series of specialized secretory organelles that play roles in invasion, host cell manipulation, and parasite replication. Rab GTPases are major regulators of the parasite's secretory traffic that function as nucleotide-dependent molecular switches to control vesicle trafficking. While many of the Rab proteins have been characterized in T. gondii, precisely how these Rabs are regulated remains poorly understood. To better understand the parasite's secretory traffic, we investigated the entire family of Tre2-Bub2-Cdc16 (TBC) domain-containing proteins, which are known to be involved in vesicle fusion and secretory protein trafficking. We first determined the localization of all 18 TBC domain-containing proteins to discrete regions of the secretory pathway or other vesicles in the parasite. Second, we use an auxin-inducible degron approach to demonstrate that the protozoan-specific TgTBC9 protein, which localizes to the endoplasmic reticulum (ER), is essential for parasite survival. Knockdown of TgTBC9 results in parasite growth arrest and affects the organization of the ER and mitochondrial morphology. TgTBC9 knockdown also results in the formation of large lipid droplets (LDs) and multi-membranous structures surrounded by ER membranes, further indicating a disruption of ER functions. We show that the conserved dual-finger active site in the TBC domain of the protein is critical for its GTPase-activating protein (GAP) function and that the Plasmodium falciparum orthologue of TgTBC9 can rescue the lethal knockdown. We additionally show by immunoprecipitation and yeast 2 hybrid analyses that TgTBC9 preferentially binds Rab2, indicating that the TBC9-Rab2 pair controls ER morphology and vesicular trafficking in the parasite. Together, these studies identify the first essential TBC protein described in any protozoan and provide new insight into intracellular vesicle trafficking in T. gondii.
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Affiliation(s)
- Justin J. Quan
- Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, Los Angeles, California, United States of America
| | - Lachezar A. Nikolov
- Department of Biology, Indiana University, Bloomington, Indiana, United States of America
| | - Jihui Sha
- Department of Biological Chemistry and Institute of Genomics and Proteomics, University of California, Los Angeles, Los Angeles, California, United States of America
| | - James A. Wohlschlegel
- Department of Biological Chemistry and Institute of Genomics and Proteomics, 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
| | - Peter J. Bradley
- Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, Los Angeles, California, United States of America
- Molecular Biology Institute, University of California, Los Angeles, Los Angeles, California, United States of America
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2
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Chan AW, Broncel M, Yifrach E, Haseley NR, Chakladar S, Andree E, Herneisen AL, Shortt E, Treeck M, Lourido S. Analysis of CDPK1 targets identifies a trafficking adaptor complex that regulates microneme exocytosis in Toxoplasma. eLife 2023; 12:RP85654. [PMID: 37933960 PMCID: PMC10629828 DOI: 10.7554/elife.85654] [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] [Indexed: 11/08/2023] Open
Abstract
Apicomplexan parasites use Ca2+-regulated exocytosis to secrete essential virulence factors from specialized organelles called micronemes. Ca2+-dependent protein kinases (CDPKs) are required for microneme exocytosis; however, the molecular events that regulate trafficking and fusion of micronemes with the plasma membrane remain unresolved. Here, we combine sub-minute resolution phosphoproteomics and bio-orthogonal labeling of kinase substrates in Toxoplasma gondii to identify 163 proteins phosphorylated in a CDPK1-dependent manner. In addition to known regulators of secretion, we identify uncharacterized targets with predicted functions across signaling, gene expression, trafficking, metabolism, and ion homeostasis. One of the CDPK1 targets is a putative HOOK activating adaptor. In other eukaryotes, HOOK homologs form the FHF complex with FTS and FHIP to activate dynein-mediated trafficking of endosomes along microtubules. We show the FHF complex is partially conserved in T. gondii, consisting of HOOK, an FTS homolog, and two parasite-specific proteins (TGGT1_306920 and TGGT1_316650). CDPK1 kinase activity and HOOK are required for the rapid apical trafficking of micronemes as parasites initiate motility. Moreover, parasites lacking HOOK or FTS display impaired microneme protein secretion, leading to a block in the invasion of host cells. Taken together, our work provides a comprehensive catalog of CDPK1 targets and reveals how vesicular trafficking has been tuned to support a parasitic lifestyle.
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Affiliation(s)
- Alex W Chan
- Whitehead Institute for Biomedical ResearchCambridgeUnited States
- Biology Department, Massachusetts Institute of TechnologyCambridgeUnited States
| | - Malgorzata Broncel
- Signaling in Apicomplexan Parasites Laboratory, The Francis Crick InstituteLondonUnited Kingdom
| | - Eden Yifrach
- Whitehead Institute for Biomedical ResearchCambridgeUnited States
| | - Nicole R Haseley
- Whitehead Institute for Biomedical ResearchCambridgeUnited States
| | | | - Elena Andree
- Whitehead Institute for Biomedical ResearchCambridgeUnited States
| | - Alice L Herneisen
- Whitehead Institute for Biomedical ResearchCambridgeUnited States
- Biology Department, Massachusetts Institute of TechnologyCambridgeUnited States
| | - Emily Shortt
- Whitehead Institute for Biomedical ResearchCambridgeUnited States
| | - Moritz Treeck
- Signaling in Apicomplexan Parasites Laboratory, The Francis Crick InstituteLondonUnited Kingdom
| | - Sebastian Lourido
- Whitehead Institute for Biomedical ResearchCambridgeUnited States
- Biology Department, Massachusetts Institute of TechnologyCambridgeUnited States
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3
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Pasquarelli RR, Back PS, Sha J, Wohlschlegel JA, Bradley PJ. Identification of IMC43, a novel IMC protein that collaborates with IMC32 to form an essential daughter bud assembly complex in Toxoplasma gondii. PLoS Pathog 2023; 19:e1011707. [PMID: 37782662 PMCID: PMC10569561 DOI: 10.1371/journal.ppat.1011707] [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: 07/26/2023] [Revised: 10/12/2023] [Accepted: 09/23/2023] [Indexed: 10/04/2023] Open
Abstract
The inner membrane complex (IMC) of Toxoplasma gondii is essential for all phases of the parasite's life cycle. One of its most critical roles is to act as a scaffold for the assembly of daughter buds during replication by endodyogeny. While many daughter IMC proteins have been identified, most are recruited after bud initiation and are not essential for parasite fitness. Here, we report the identification of IMC43, a novel daughter IMC protein that is recruited at the earliest stages of daughter bud initiation. Using an auxin-inducible degron system we show that depletion of IMC43 results in aberrant morphology, dysregulation of endodyogeny, and an extreme defect in replication. Deletion analyses reveal a region of IMC43 that plays a role in localization and a C-terminal domain that is essential for the protein's function. TurboID proximity labelling and a yeast two-hybrid screen using IMC43 as bait identify 30 candidate IMC43 binding partners. We investigate two of these: the essential daughter protein IMC32 and a novel daughter IMC protein we named IMC44. We show that IMC43 is responsible for regulating the localization of both IMC32 and IMC44 at specific stages of endodyogeny and that this regulation is dependent on the essential C-terminal domain of IMC43. Using pairwise yeast two-hybrid assays, we determine that this region is also sufficient for binding to both IMC32 and IMC44. As IMC43 and IMC32 are both essential proteins, this work reveals the existence of a bud assembly complex that forms the foundation of the daughter IMC during endodyogeny.
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Affiliation(s)
- Rebecca R. Pasquarelli
- Molecular Biology Institute, University of California, Los Angeles, California, United States of America
| | - Peter S. Back
- Molecular Biology Institute, University of California, Los Angeles, California, United States of America
| | - Jihui Sha
- Department of Biological Chemistry and Institute of Genomics and Proteomics, University of California, Los Angeles, California, United States of America
| | - James A. Wohlschlegel
- Department of Biological Chemistry and Institute of Genomics and Proteomics, University of California, Los Angeles, California, United States of America
| | - Peter J. Bradley
- Molecular Biology Institute, University of California, Los Angeles, California, United States of America
- Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles, California, United States of America
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4
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Chan AW, Broncel M, Yifrach E, Haseley N, Chakladar S, Andree E, Herneisen AL, Shortt E, Treeck M, Lourido S. Analysis of CDPK1 targets identifies a trafficking adaptor complex that regulates microneme exocytosis in Toxoplasma. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.01.11.523553. [PMID: 36712004 PMCID: PMC9882037 DOI: 10.1101/2023.01.11.523553] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Apicomplexan parasites use Ca2+-regulated exocytosis to secrete essential virulence factors from specialized organelles called micronemes. Ca2+-dependent protein kinases (CDPKs) are required for microneme exocytosis; however, the molecular events that regulate trafficking and fusion of micronemes with the plasma membrane remain unresolved. Here, we combine sub-minute resolution phosphoproteomics and bio-orthogonal labeling of kinase substrates in Toxoplasma gondii to identify 163 proteins phosphorylated in a CDPK1-dependent manner. In addition to known regulators of secretion, we identify uncharacterized targets with predicted functions across signaling, gene expression, trafficking, metabolism, and ion homeostasis. One of the CDPK1 targets is a putative HOOK activating adaptor. In other eukaryotes, HOOK homologs form the FHF complex with FTS and FHIP to activate dynein-mediated trafficking of endosomes along microtubules. We show the FHF complex is partially conserved in T. gondii, consisting of HOOK, an FTS homolog, and two parasite-specific proteins (TGGT1_306920 and TGGT1_316650). CDPK1 kinase activity and HOOK are required for the rapid apical trafficking of micronemes as parasites initiate motility. Moreover, parasites lacking HOOK or FTS display impaired microneme protein secretion, leading to a block in the invasion of host cells. Taken together, our work provides a comprehensive catalog of CDPK1 targets and reveals how vesicular trafficking has been tuned to support a parasitic lifestyle.
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Affiliation(s)
- Alex W Chan
- Whitehead Institute for Biomedical Research, Cambridge, MA, USA
- Biology Department, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Malgorzata Broncel
- Signaling in Apicomplexan Parasites Laboratory, The Francis Crick Institute, London, UK
| | - Eden Yifrach
- Whitehead Institute for Biomedical Research, Cambridge, MA, USA
| | - Nicole Haseley
- Whitehead Institute for Biomedical Research, Cambridge, MA, USA
| | | | - Elena Andree
- Whitehead Institute for Biomedical Research, Cambridge, MA, USA
| | - Alice L Herneisen
- Whitehead Institute for Biomedical Research, Cambridge, MA, USA
- Biology Department, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Emily Shortt
- Whitehead Institute for Biomedical Research, Cambridge, MA, USA
| | - Moritz Treeck
- Signaling in Apicomplexan Parasites Laboratory, The Francis Crick Institute, London, UK
| | - Sebastian Lourido
- Whitehead Institute for Biomedical Research, Cambridge, MA, USA
- Biology Department, Massachusetts Institute of Technology, Cambridge, MA, USA
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5
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Back PS, Senthilkumar V, Choi CP, Ly AM, Snyder AK, Lau JG, Ward GE, Bradley PJ. The Toxoplasma subpellicular network is highly interconnected and defines parasite shape for efficient motility and replication. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.08.10.552545. [PMID: 37609316 PMCID: PMC10441382 DOI: 10.1101/2023.08.10.552545] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/24/2023]
Abstract
Apicomplexan parasites possess several specialized structures to invade their host cells and replicate successfully. One of these is the inner membrane complex (IMC), a peripheral membrane-cytoskeletal system underneath the plasma membrane. It is composed of a series of flattened, membrane-bound vesicles and a cytoskeletal subpellicular network (SPN) comprised of intermediate filament-like proteins called alveolins. While the alveolin proteins are conserved throughout the Apicomplexa and the broader Alveolata, their precise functions and interactions remain poorly understood. Here, we describe the function of one of these alveolin proteins, TgIMC6. Disruption of IMC6 resulted in striking morphological defects that led to aberrant motility, invasion, and replication. Deletion analyses revealed that the alveolin domain alone is largely sufficient to restore localization and partially sufficient for function. As this highlights the importance of the IMC6 alveolin domain, we implemented unnatural amino acid photoreactive crosslinking to the alveolin domain and identified multiple binding interfaces between IMC6 and two other cytoskeletal proteins - IMC3 and ILP1. To our knowledge, this provides the first direct evidence of protein-protein interactions in the alveolin domain and supports the long-held hypothesis that the alveolin domain is responsible for filament formation. Collectively, our study features the conserved alveolin proteins as critical components that maintain the parasite's structural integrity and highlights the alveolin domain as a key mediator of SPN architecture.
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O’Shaughnessy WJ, Hu X, Henriquez SA, Reese ML. Toxoplasma ERK7 protects the apical complex from premature degradation. J Cell Biol 2023; 222:e202209098. [PMID: 37027006 PMCID: PMC10083718 DOI: 10.1083/jcb.202209098] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2022] [Revised: 02/01/2023] [Accepted: 03/17/2023] [Indexed: 04/08/2023] Open
Abstract
Accurate cellular replication balances the biogenesis and turnover of complex structures. In the apicomplexan parasite Toxoplasma gondii, daughter cells form within an intact mother cell, creating additional challenges to ensuring fidelity of division. The apical complex is critical to parasite infectivity and consists of apical secretory organelles and specialized cytoskeletal structures. We previously identified the kinase ERK7 as required for maturation of the apical complex in Toxoplasma. Here, we define the Toxoplasma ERK7 interactome, including a putative E3 ligase, CSAR1. Genetic disruption of CSAR1 fully suppresses loss of the apical complex upon ERK7 knockdown. Furthermore, we show that CSAR1 is normally responsible for turnover of maternal cytoskeleton during cytokinesis, and that its aberrant function is driven by mislocalization from the parasite residual body to the apical complex. These data identify a protein homeostasis pathway critical for Toxoplasma replication and fitness and suggest an unappreciated role for the parasite residual body in compartmentalizing processes that threaten the fidelity of parasite development.
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Affiliation(s)
| | - Xiaoyu Hu
- Department of Pharmacology, University of Texas, Southwestern Medical Center, Dallas, TX, USA
| | - Sarah Ana Henriquez
- Department of Pharmacology, University of Texas, Southwestern Medical Center, Dallas, TX, USA
| | - Michael L. Reese
- Department of Pharmacology, University of Texas, Southwestern Medical Center, Dallas, TX, USA
- Department of Biochemistry, University of Texas, Southwestern Medical Center, Dallas, TX, USA
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7
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Quan JJ, Nikolov LA, Sha J, Wohlschlegel JA, Bradley PJ. Toxoplasma gondii encodes an array of TBC-domain containing proteins including an essential regulator that targets Rab2 in the secretory pathway. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.05.28.542599. [PMID: 37398139 PMCID: PMC10312441 DOI: 10.1101/2023.05.28.542599] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/04/2023]
Abstract
Toxoplasma gondii resides in its intracellular niche by employing a series of specialized secretory organelles that play roles in invasion, host-cell manipulation and parasite replication. Rab GTPases are major regulators of the parasite's secretory traffic that function as nucleotide dependent molecular switches to control vesicle trafficking. While many of the Rab proteins have been characterized in T. gondii , precisely how these Rabs are regulated remains poorly understood. To better understand the parasite's secretory traffic, we investigated the entire family of Tre2-Bub2-Cdc16 (TBC)-domain containing proteins, which are known to be involved in vesicle fusion and secretory protein trafficking. We first determined the localization of all 18 TBC-domain containing proteins to discrete regions of the secretory pathway or other vesicles in the parasite. We then use an auxin-inducible degron approach to demonstrate that the protozoan-specific TgTBC9 protein that localizes to the ER is essential for parasite survival. Knockdown of TgTBC9 results in parasite growth arrest and affects the organization of the ER and Golgi apparatus. We show that the conserved dual-finger active site in the TBC-domain of the protein is critical for its GTPase-activating protein (GAP) function and that the P. falciparum orthologue of TgTBC9 can rescue the lethal knockdown. We additionally show by immunoprecipitation and yeast two hybrid analyses that TgTBC9 directly binds Rab2, indicating that this TBC-Rab pair controls ER to Golgi traffic in the parasite. Together, these studies identify the first essential TBC protein described in any protozoan, provide new insight into intracellular vesicle trafficking in T. gondii , and reveal promising targets for the design of novel therapeutics that can specifically target apicomplexan parasites.
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Santos FA, Cruz GS, Vieira FA, Queiroz BR, Freitas CD, Mesquita FP, Souza PF. Systematic Review of Antiprotozoal Potential of Antimicrobial Peptides. Acta Trop 2022; 236:106675. [DOI: 10.1016/j.actatropica.2022.106675] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2022] [Revised: 08/29/2022] [Accepted: 08/30/2022] [Indexed: 11/01/2022]
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9
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Alves MLF, Ferreira MRA, Donassolo RA, Rodrigues RR, Conceição FR. Clostridium septicum: A review in the light of alpha-toxin and development of vaccines. Vaccine 2021; 39:4949-4956. [PMID: 34312008 DOI: 10.1016/j.vaccine.2021.07.019] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2021] [Revised: 05/31/2021] [Accepted: 07/08/2021] [Indexed: 10/20/2022]
Abstract
Clostridium septicum (CS) is a pathogen that can cause the death of animals in livestock worldwide through its main virulence factor, alpha-toxin (ATX). The aspects involved in diseases caused by ATX, such as economic impact, prevalence, and rapid clinical course, require that animals should be systematically immunized. This review provides an overview of CS in livestock farming and discusses current immunization methods. Currently, commercial vaccines available against CS involve the cultivation and inactivation of microorganisms and toxins using a time-consuming, expensive, and high biological risk-carrying production platform, and some have been reported to be ineffective. An alternative to this process is the recombinant DNA technology, although recombinant ATX obtained thus far is no longer efficient in stimulating protective antibody titers despite improvements in the production methods. On the other hand, immunized animals have highly favorable levels of survival when subjected to challenge tests, suggesting that high titers of circulating serum antibodies may not be representative of protection after immunization and that the non-immune cellular defenses associated with the particularities of the mechanism of action of ATX may be involved in the immune response of the host. To contribute to the future of global livestock farming through the development of more efficient recombinant vaccines, we suggest novel perspectives and strategies, such as the location of immunodominant epitopes, expression of relevant functional domains, and construction of chimeras, in the rational design of recombinant ATX.
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Affiliation(s)
- Mariliana Luiza Ferreira Alves
- Instituto Federal Sul-rio-grandense - IFSUL, Praça Vinte de Setembro, 455, Centro, CEP 96.015-360, Pelotas, RS, Brazil; Centro de Desenvolvimento Tecnológico, Núcleo de Biotecnologia, Universidade Federal de Pelotas, CP 354, CEP 96160-000, Pelotas, RS, Brazil.
| | - Marcos Roberto Alves Ferreira
- Centro de Desenvolvimento Tecnológico, Núcleo de Biotecnologia, Universidade Federal de Pelotas, CP 354, CEP 96160-000, Pelotas, RS, Brazil
| | - Rafael Amaral Donassolo
- Centro de Desenvolvimento Tecnológico, Núcleo de Biotecnologia, Universidade Federal de Pelotas, CP 354, CEP 96160-000, Pelotas, RS, Brazil
| | - Rafael Rodrigues Rodrigues
- Centro de Desenvolvimento Tecnológico, Núcleo de Biotecnologia, Universidade Federal de Pelotas, CP 354, CEP 96160-000, Pelotas, RS, Brazil
| | - Fabricio Rochedo Conceição
- Centro de Desenvolvimento Tecnológico, Núcleo de Biotecnologia, Universidade Federal de Pelotas, CP 354, CEP 96160-000, Pelotas, RS, Brazil
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Blocking Palmitoylation of Toxoplasma gondii Myosin Light Chain 1 Disrupts Glideosome Composition but Has Little Impact on Parasite Motility. mSphere 2021; 6:6/3/e00823-20. [PMID: 34011689 PMCID: PMC8265671 DOI: 10.1128/msphere.00823-20] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Toxoplasma gondii is a widespread apicomplexan parasite that causes severe disease in immunocompromised individuals and the developing fetus. Like other apicomplexans, T. gondii uses an unusual form of substrate-dependent gliding motility to invade cells of its hosts and to disseminate throughout the body during infection. It is well established that a myosin motor consisting of a class XIVa heavy chain (TgMyoA) and two light chains (TgMLC1 and TgELC1/2) plays an important role in parasite motility. The ability of the motor to generate force at the parasite periphery is thought to be reliant upon its anchoring and immobilization within a peripheral membrane-bound compartment, the inner membrane complex (IMC). The motor does not insert into the IMC directly; rather, this interaction is believed to be mediated by the binding of TgMLC1 to the IMC-anchored protein, TgGAP45. Therefore, the binding of TgMLC1 to TgGAP45 is considered a key element in the force transduction machinery of the parasite. TgMLC1 is palmitoylated, and we show here that palmitoylation occurs on two N-terminal cysteine residues, C8 and C11. Mutations that block TgMLC1 palmitoylation completely abrogate the binding of TgMLC1 to TgGAP45. Surprisingly, the loss of TgMLC1 binding to TgGAP45 in these mutant parasites has little effect on their ability to initiate or sustain movement. These results question a key tenet of the current model of apicomplexan motility and suggest that our understanding of gliding motility in this important group of human and animal pathogens is not yet complete. IMPORTANCE Gliding motility plays a central role in the life cycle of T. gondii and other apicomplexan parasites. The myosin motor thought to power motility is essential for virulence but distinctly different from the myosins found in humans. Consequently, an understanding of the mechanism(s) underlying parasite motility and the role played by this unusual myosin may reveal points of vulnerability that can be targeted for disease prevention or treatment. We show here that mutations that uncouple the motor from what is thought to be a key structural component of the motility machinery have little impact on parasite motility. This finding runs counter to predictions of the current, widely held “linear motor” model of motility, highlighting the need for further studies to fully understand how apicomplexan parasites generate the forces necessary to move into, out of, and between cells of the hosts they infect.
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11
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Maclean AE, Bridges HR, Silva MF, Ding S, Ovciarikova J, Hirst J, Sheiner L. Complexome profile of Toxoplasma gondii mitochondria identifies divergent subunits of respiratory chain complexes including new subunits of cytochrome bc1 complex. PLoS Pathog 2021; 17:e1009301. [PMID: 33651838 PMCID: PMC7987180 DOI: 10.1371/journal.ppat.1009301] [Citation(s) in RCA: 29] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2020] [Revised: 03/23/2021] [Accepted: 01/11/2021] [Indexed: 12/30/2022] Open
Abstract
The mitochondrial electron transport chain (mETC) and F1Fo-ATP synthase are of central importance for energy and metabolism in eukaryotic cells. The Apicomplexa, important pathogens of humans causing diseases such as toxoplasmosis and malaria, depend on their mETC in every known stage of their complicated life cycles. Here, using a complexome profiling proteomic approach, we have characterised the Toxoplasma mETC complexes and F1Fo-ATP synthase. We identified and assigned 60 proteins to complexes II, IV and F1Fo-ATP synthase of Toxoplasma, of which 16 have not been identified previously. Notably, our complexome profile elucidates the composition of the Toxoplasma complex III, the target of clinically used drugs such as atovaquone. We identified two new homologous subunits and two new parasite-specific subunits, one of which is broadly conserved in myzozoans. We demonstrate all four proteins are essential for complex III stability and parasite growth, and show their depletion leads to decreased mitochondrial potential, supporting their assignment as complex III subunits. Our study highlights the divergent subunit composition of the apicomplexan mETC and F1Fo-ATP synthase complexes and sets the stage for future structural and drug discovery studies.
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Affiliation(s)
- Andrew E. Maclean
- Wellcome Centre for Integrative Parasitology, University of Glasgow, Glasgow, United Kingdom
| | - Hannah R. Bridges
- MRC Mitochondrial Biology Unit, University of Cambridge, Cambridge, United Kingdom
| | - Mariana F. Silva
- Wellcome Centre for Integrative Parasitology, University of Glasgow, Glasgow, United Kingdom
- Institute of Biomedical Sciences, Federal University of Uberlândia, Uberlândia, Brazil
| | - Shujing Ding
- MRC Mitochondrial Biology Unit, University of Cambridge, Cambridge, United Kingdom
| | - Jana Ovciarikova
- Wellcome Centre for Integrative Parasitology, University of Glasgow, Glasgow, United Kingdom
| | - Judy Hirst
- MRC Mitochondrial Biology Unit, University of Cambridge, Cambridge, United Kingdom
| | - Lilach Sheiner
- Wellcome Centre for Integrative Parasitology, University of Glasgow, Glasgow, United Kingdom
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12
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Multivalent Interactions Drive the Toxoplasma AC9:AC10:ERK7 Complex To Concentrate ERK7 in the Apical Cap. mBio 2021; 13:e0286421. [PMID: 35130732 PMCID: PMC8822341 DOI: 10.1128/mbio.02864-21] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
The Toxoplasma inner membrane complex (IMC) is a specialized organelle that is crucial for the parasite to establish an intracellular lifestyle and ultimately cause disease. The IMC is composed of both membrane and cytoskeletal components, further delineated into the apical cap, body, and basal subcompartments. The apical cap cytoskeleton was recently demonstrated to govern the stability of the apical complex, which controls parasite motility, invasion, and egress. While this role was determined by individually assessing the apical cap proteins AC9, AC10, and the mitogen-activated protein kinase ERK7, how the three proteins collaborate to stabilize the apical complex is unknown. In this study, we use a combination of deletion analyses and yeast two-hybrid experiments to establish that these proteins form an essential complex in the apical cap. We show that AC10 is a foundational component of the AC9:AC10:ERK7 complex and demonstrate that the interactions among them are critical to maintaining the apical complex. Importantly, we identify multiple independent regions of pairwise interaction between each of the three proteins, suggesting that the AC9:AC10:ERK7 complex is organized by multivalent interactions. Together, these data support a model in which multiple interacting domains enable the oligomerization of the AC9:AC10:ERK7 complex and its assembly into the cytoskeletal IMC, which serves as a structural scaffold that concentrates ERK7 kinase activity in the apical cap. IMPORTANCE The phylum Apicomplexa consists of obligate, intracellular parasites, including the causative agents of toxoplasmosis, malaria, and cryptosporidiosis. Hallmarks of these parasites are the IMC and the apical complex, both of which are unique structures that are conserved throughout the phylum and required for parasite survival. The apical cap portion of the IMC has previously been shown to stabilize the apical complex. Here, we expand on those studies to determine the precise protein-protein interactions of the apical cap complex that confer this essential function. We describe the multivalent nature of these interactions and show that the resulting protein oligomers likely tether ERK7 in the apical cap. This study represents the first description of the architecture of the apical cap at a molecular level, expanding our understanding of the unique cell biology that drives Toxoplasma infections.
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Namdar F, Khanahmad H, Ghayour Z, Mirzaei F, Namdar A, Aghaei M, Izadi S, Khamesipour F, Hejazi SH. Evaluation of the Anti-Leishmanial Effect of Recombinant Clostridium α-Toxin. Infect Drug Resist 2020; 13:2355-2364. [PMID: 32765010 PMCID: PMC7369417 DOI: 10.2147/idr.s257561] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2020] [Accepted: 06/24/2020] [Indexed: 02/05/2023] Open
Abstract
BACKGROUND Leishmaniasis is an infectious disease common in tropical and subtropical regions caused by the genus Leishmania, which is transmitted by the bite of female sandflies. In this study, we evaluate the anti-leishmanial effect of recombinant Clostridium α-toxin protein alone and the combination with glucantime through in vitro and in vivo. MATERIALS AND METHODS Production, expression, and purification of recombinant α-toxin were evaluated by SDS-PAGE and Western blotting techniques. The antileishmanial activities of the purified α-toxin plus and without glucantime were examined in vitro and in vivo. RESULTS The results indicated successful expression of α-toxin as a 48 kDa band on SDS-PAGE and Western blot methods. Also, evaluation of α-toxin IC50 showed the strong fatal effect of it, and glucantime on medium proliferated Leishmania promastigotes at lower concentrations compared with glucantime or α-toxin alone. Moreover, in vivo surveys showed that at the end of treatment courses, the mean of lesion size diminished in glucantime plus α-toxin treated mice versus negative control groups (p < 0.001). Also, there was a significant difference in the parasite burden of the spleen and liver of the control versus the test groups (p < 0.001). CONCLUSION The results showed recombinant α-toxin has synergistic effects with glucantime in destroying Leishmania parasites.
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Affiliation(s)
- Fatemeh Namdar
- Department of Parasitology and Mycology, School of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran
| | - Hossein Khanahmad
- Department of Genetics and Molecular Biology, School of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran
| | - Zahra Ghayour
- Department of Parasitology and Mycology, School of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran
| | - Farzaneh Mirzaei
- Department of Parasitology and Mycology, School of Medicine, Shahid Sadoughi University of Medical Sciences, Yazd, Iran
| | - Azam Namdar
- Department of Community Medicine, School of Medicine, Fasa University of Medical Sciences, Fasa, Iran
| | - Maryam Aghaei
- Skin Diseases and Leishmaniasis Research Center, Isfahan University of Medical Sciences, Isfahan, Iran
| | - Shahrokh Izadi
- Department of Medical Parasitology and Mycology, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran
| | - Faham Khamesipour
- Cellular and Molecular Research Center, Sabzevar University of Medical Sciences, Sabzevar, Iran
- Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Seyed Hossein Hejazi
- Department of Parasitology and Mycology, School of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran
- Skin Diseases and Leishmaniasis Research Center, Department of Parasitology and Mycology, School of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran
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14
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Fathi Najaf M, Hemmaty M, Navidmehr J, Afsharian M, Farhoodi M, Zibaee S. Improvement in the Growth and α-toxin Production of Clostridium septicum by Magnesium Sulfate. ARCHIVES OF RAZI INSTITUTE 2020; 75:219-225. [PMID: 32621451 DOI: 10.22092/ari.2019.124567.1284] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 06/27/2020] [Accepted: 07/23/2019] [Indexed: 09/30/2022]
Abstract
Clostridium septicum, the anaerobic toxigenic bacterium is the agent that causes dangerous disease in man and animals. There is a lethal toxin of the bacterium namely alpha toxin. The ɑ-toxin has hemolytic, necrotic and lethal activities. Today, Razi Vaccine and Serum Research Institute of Iran produced the C. septicum vaccine in the form of bacterin/toxoid. Because of some problems, the vaccine needs to improve on an industrial scale. The study is going to find an appropriate supplement to improve growth and ɑ-toxin production. Three strains of C. septicum (vaccine, NH1 and NH8 strains) were cultured in the basic vaccine media. Magnesium sulfate, Copper, Ferrous, yeast extract, and trace elements plus vitamins&#39; solution were added to the basic vaccine media in different cultures. The effect of the ingredients on the growth was measured by a spectrophotometer and the &alpha;-toxin secretion was assayed by hemolysin test. Growth of the bacterium and &alpha;-toxin secretion were increased by Magnesium (80 mg/l) in NH8 and vaccine strains significantly. The black precipitate was difficult to dissolve in magnesium media that must be solved. Trace elements plus vitamins solution mildly influence on NH1strain growth and toxin secretion. Other supplements (Cu, Fe, yeast extract) were not showen any significant changes in the growth and &alpha;-toxin production of C. septicum. Overflowing peptone (4%) in the vaccine media, fixes essentials of proteolysis activity, allows the sufficient growth and toxin production without Cu, Fe, and yeast extract. Due to essentially of Mg for growth, extra magnesium was added for improvement of media culture. The study suggests for Magnesium addition in the C. septicum vaccine media during production procedure after precipitation solving problem.
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Affiliation(s)
- M Fathi Najaf
- Salim Immune Product Company, Mashhad Branch, Razi Technology Incubator, Razi Vaccine and Serum Research Institute of Mashhad, Agricultural Research, Education and Extension Organization (AREEO), Mashhad, Iran.,Mashhad Branch, Razi Vaccine and Serum Research Institute, Agricultural Research, Education and Extension Organization (AREEO), Mashhad, Iran
| | - M Hemmaty
- Salim Immune Product Company, Mashhad Branch, Razi Technology Incubator, Razi Vaccine and Serum Research Institute of Mashhad, Agricultural Research, Education and Extension Organization (AREEO), Mashhad, Iran.,Mashhad Branch, Razi Vaccine and Serum Research Institute, Agricultural Research, Education and Extension Organization (AREEO), Mashhad, Iran.,Salim Immune Product Company, Mashhad Branch, Razi Technology Incubator, Razi Vaccine and Serum Research Institute of Mashhad, Agricultural Research, Education and Extension Organization (AREEO), Mashhad, Iran
| | - J Navidmehr
- Salim Immune Product Company, Mashhad Branch, Razi Technology Incubator, Razi Vaccine and Serum Research Institute of Mashhad, Agricultural Research, Education and Extension Organization (AREEO), Mashhad, Iran
| | - M Afsharian
- Salim Immune Product Company, Mashhad Branch, Razi Technology Incubator, Razi Vaccine and Serum Research Institute of Mashhad, Agricultural Research, Education and Extension Organization (AREEO), Mashhad, Iran
| | - M Farhoodi
- Mashhad Branch, Razi Vaccine and Serum Research Institute, Agricultural Research, Education and Extension Organization (AREEO), Mashhad, Iran
| | - S Zibaee
- Mashhad Branch, Razi Vaccine and Serum Research Institute, Agricultural Research, Education and Extension Organization (AREEO), Mashhad, Iran
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15
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Stasic AJ, Chasen NM, Dykes EJ, Vella SA, Asady B, Starai VJ, Moreno SNJ. The Toxoplasma Vacuolar H +-ATPase Regulates Intracellular pH and Impacts the Maturation of Essential Secretory Proteins. Cell Rep 2020; 27:2132-2146.e7. [PMID: 31091451 PMCID: PMC6760873 DOI: 10.1016/j.celrep.2019.04.038] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2018] [Revised: 10/31/2018] [Accepted: 04/05/2019] [Indexed: 12/20/2022] Open
Abstract
Vacuolar-proton ATPases (V-ATPases) are conserved complexes that couple the hydrolysis of ATP to the pumping of protons across membranes. V-ATPases are known to play diverse roles in cellular physiology. We studied the Toxoplasma gondii V-ATPase complex and discovered a dual role of the pump in protecting parasites against ionic stress and in the maturation of secretory proteins in endosomal-like compartments. Toxoplasma V-ATPase subunits localize to the plasma membrane and to acidic vesicles, and characterization of conditional mutants of the a1 subunit highlighted the functionality of the complex at both locations. Microneme and rhoptry proteins are required for invasion and modulation of host cells, and they traffic via endosome-like compartments in which proteolytic maturation occurs. We show that the V-ATPase supports the maturation of rhoptry and microneme proteins, and their maturases, during their traffic to their corresponding organelles. This work underscores a role for V-ATPases in regulating virulence pathways. Stasic et al. characterize the function of the vacuolar proton ATPase in the life cycle of Toxoplasma gondii, a widespread parasite that infects almost one-third of the world’s population. The work presents molecular evidence of the pump’s role in the synthesis of virulence factors of a highly successful pathogen.
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Affiliation(s)
- Andrew J Stasic
- Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, GA 30602-7400, USA; Department of Microbiology, University of Georgia, Athens, GA 30602-7400, USA
| | - Nathan M Chasen
- Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, GA 30602-7400, USA; Department of Infectious Diseases, University of Georgia, Athens, GA 30602-7400, USA
| | - Eric J Dykes
- Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, GA 30602-7400, USA
| | - Stephen A Vella
- Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, GA 30602-7400, USA; Department of Microbiology, University of Georgia, Athens, GA 30602-7400, USA
| | - Beejan Asady
- Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, GA 30602-7400, USA
| | - Vincent J Starai
- Department of Microbiology, University of Georgia, Athens, GA 30602-7400, USA; Department of Infectious Diseases, University of Georgia, Athens, GA 30602-7400, USA
| | - Silvia N J Moreno
- Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, GA 30602-7400, USA; Department of Cellular Biology, University of Georgia, Athens, GA 30602-7400, USA.
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16
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Ancient MAPK ERK7 is regulated by an unusual inhibitory scaffold required for Toxoplasma apical complex biogenesis. Proc Natl Acad Sci U S A 2020; 117:12164-12173. [PMID: 32409604 PMCID: PMC7275706 DOI: 10.1073/pnas.1921245117] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Apicomplexan parasites include organisms that cause widespread and devastating human diseases such as malaria, cryptosporidiosis, and toxoplasmosis. These parasites are named for a structure, called the “apical complex,” that organizes their invasion and secretory machinery. We found that two proteins, apical cap protein 9 (AC9) and an enzyme called ERK7, work together to facilitate apical complex assembly. Intriguingly, ERK7 is an ancient molecule that is found throughout Eukaryota, though its regulation and function are poorly understood. AC9 is a scaffold that concentrates ERK7 at the base of the developing apical complex. In addition, AC9 binding likely confers substrate selectivity upon ERK7. This simple competitive regulatory model may be a powerful but largely overlooked mechanism throughout biology. Apicomplexan parasites use a specialized cilium structure called the apical complex to organize their secretory organelles and invasion machinery. The apical complex is integrally associated with both the parasite plasma membrane and an intermediate filament cytoskeleton called the inner-membrane complex (IMC). While the apical complex is essential to the parasitic lifestyle, little is known about the regulation of apical complex biogenesis. Here, we identify AC9 (apical cap protein 9), a largely intrinsically disordered component of the Toxoplasma gondii IMC, as essential for apical complex development, and therefore for host cell invasion and egress. Parasites lacking AC9 fail to successfully assemble the tubulin-rich core of their apical complex, called the conoid. We use proximity biotinylation to identify the AC9 interaction network, which includes the kinase extracellular signal-regulated kinase 7 (ERK7). Like AC9, ERK7 is required for apical complex biogenesis. We demonstrate that AC9 directly binds ERK7 through a conserved C-terminal motif and that this interaction is essential for ERK7 localization and function at the apical cap. The crystal structure of the ERK7–AC9 complex reveals that AC9 is not only a scaffold but also inhibits ERK7 through an unusual set of contacts that displaces nucleotide from the kinase active site. ERK7 is an ancient and autoactivating member of the mitogen-activated kinase (MAPK) family and its regulation is poorly understood in all organisms. We propose that AC9 dually regulates ERK7 by scaffolding and concentrating it at its site of action while maintaining it in an “off” state until the specific binding of a true substrate.
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17
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Choi CP, Moon AS, Back PS, Jami‐Alahmadi Y, Vashisht AA, Wohlschlegel JA, Bradley PJ. A photoactivatable crosslinking system reveals protein interactions in the Toxoplasma gondii inner membrane complex. PLoS Biol 2019; 17:e3000475. [PMID: 31584943 PMCID: PMC6795473 DOI: 10.1371/journal.pbio.3000475] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2019] [Revised: 10/16/2019] [Accepted: 09/13/2019] [Indexed: 11/18/2022] Open
Abstract
The Toxoplasma gondii inner membrane complex (IMC) is an important organelle involved in parasite motility and replication. The IMC resides beneath the parasite’s plasma membrane and is composed of both membrane and cytoskeletal components. Although the protein composition of the IMC is becoming better understood, the protein–protein associations that enable proper functioning of the organelle remain largely unknown. Determining protein interactions in the IMC cytoskeletal network is particularly challenging, as disrupting the cytoskeleton requires conditions that disrupt protein complexes. To circumvent this problem, we demonstrate the application of a photoreactive unnatural amino acid (UAA) crosslinking system to capture protein interactions in the native intracellular environment. In addition to identifying binding partners, the UAA approach maps the binding interface of the bait protein used for crosslinking, providing structural information of the interacting proteins. We apply this technology to the essential IMC protein ILP1 and demonstrate that distinct regions of its C-terminal coiled-coil domain crosslink to the alveolins IMC3 and IMC6, as well as IMC27. We also show that the IMC3 C-terminal domain and the IMC6 N-terminal domain are necessary for binding to ILP1, further mapping interactions between ILP1 and the cytoskeleton. Together, this study develops a new approach to study protein–protein interactions in Toxoplasma and provides the first insight into the architecture of the cytoskeletal network of the apicomplexan IMC. The inner membrane complex of the human parasite Toxoplasma gondii is an important organelle involved in motility and replication. This study expands the genetic code of Toxoplasma, allowing the use of photoactivatable unnatural amino acids to uncover interactions within the apicomplexan inner membrane complex.
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Affiliation(s)
- Charles Paul Choi
- Molecular Biology Institute, University of California, Los Angeles, Los Angeles, California, United States of America
| | - Andy Seong Moon
- Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, Los Angeles, California, United States of America
| | - Peter Sungmin Back
- Molecular Biology Institute, University of California, Los Angeles, Los Angeles, California, United States of America
| | - Yasaman Jami‐Alahmadi
- Department of Biological Chemistry, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California, United States of America
| | - Ajay Amar Vashisht
- Department of Biological Chemistry, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California, United States of America
| | - James Akira Wohlschlegel
- Molecular Biology Institute, University of California, Los Angeles, Los Angeles, California, United States of America
- Department of Biological Chemistry, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California, United States of America
| | - Peter John Bradley
- Molecular Biology Institute, University of California, Los Angeles, Los Angeles, California, United States of America
- 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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18
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Kumar V, Behl A, Kapoor P, Nayak B, Singh G, Singh AP, Mishra S, Kang TS, Mishra PC, Hora R. Inner membrane complex 1l protein of Plasmodium falciparum links membrane lipids with cytoskeletal element 'actin' and its associated motor 'myosin'. Int J Biol Macromol 2018; 126:673-684. [PMID: 30599160 DOI: 10.1016/j.ijbiomac.2018.12.239] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2018] [Revised: 12/25/2018] [Accepted: 12/26/2018] [Indexed: 01/14/2023]
Abstract
The inner membrane complex (IMC) is a defining feature of apicomplexans comprising of lipid and protein components involved in gliding motility and host cell invasion. Motility of Plasmodium parasites is accomplished by an actin and myosin based glideosome machinery situated between the parasite plasma membrane (PPM) and IMC. Here, we have studied in vivo expression and localization of a Plasmodium falciparum (Pf) IMC protein 'PfIMC1l' and characterized it functionally by using biochemical assays. We have identified cytoskeletal protein 'actin' and motor protein 'myosin' as novel binding partners of PfIMC1l, alongside its interaction with the lipids 'cholesterol' and 'phosphatidyl-inositol 4, 5 bisphosphate' (PIP2). While actin and myosin compete for interaction with PfIMC1l, actin and either of the lipids (cholesterol or PIP2) simultaneously bind PfIMC1l. Interestingly, PfIMC1l showed enhanced binding with actin in the presence of calcium ions, and displayed direct binding with calcium. Based on our in silico analysis and experimental data showing PfIMC1l-actin/myosin and PfIMC1l-lipid interactions, we propose that this protein may anchor the IMC membrane with the parasite gliding apparatus. Considering its binding with key proteins involved in motility viz. myosin and actin (with calcium dependence), we suggest that PfIMC1l may have a role in the locomotion of Plasmodium.
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Affiliation(s)
- Vikash Kumar
- Department of Molecular Biology and Biochemistry, Guru Nanak Dev University, Amritsar, Punjab, India
| | - Ankita Behl
- Department of Biotechnology, Guru Nanak Dev University, Amritsar, Punjab, India
| | - Payal Kapoor
- Department of Molecular Biology and Biochemistry, Guru Nanak Dev University, Amritsar, Punjab, India
| | - Bandita Nayak
- CSIR-Central Drug Research Institute, Lucknow, Uttar Pradesh, India
| | - Gurbir Singh
- Department of Chemistry, Guru Nanak Dev University, Amritsar, Punjab, India
| | - Amrit Pal Singh
- Department of Pharmaceutical Science, Guru Nanak Dev University, Amritsar, Punjab, India
| | - Satish Mishra
- CSIR-Central Drug Research Institute, Lucknow, Uttar Pradesh, India
| | - Tejwant Singh Kang
- Department of Chemistry, Guru Nanak Dev University, Amritsar, Punjab, India
| | | | - Rachna Hora
- Department of Molecular Biology and Biochemistry, Guru Nanak Dev University, Amritsar, Punjab, India.
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19
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Functional Analyses of a Putative, Membrane-Bound, Peroxisomal Protein Import Mechanism from the Apicomplexan Protozoan Toxoplasma gondii. Genes (Basel) 2018; 9:genes9090434. [PMID: 30158461 PMCID: PMC6162456 DOI: 10.3390/genes9090434] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2018] [Revised: 08/17/2018] [Accepted: 08/21/2018] [Indexed: 01/28/2023] Open
Abstract
Peroxisomes are central to eukaryotic metabolism, including the oxidation of fatty acids—which subsequently provide an important source of metabolic energy—and in the biosynthesis of cholesterol and plasmalogens. However, the presence and nature of peroxisomes in the parasitic apicomplexan protozoa remains controversial. A survey of the available genomes revealed that genes encoding peroxisome biogenesis factors, so-called peroxins (Pex), are only present in a subset of these parasites, the coccidia. The basic principle of peroxisomal protein import is evolutionarily conserved, proteins harbouring a peroxisomal-targeting signal 1 (PTS1) interact in the cytosol with the shuttling receptor Pex5 and are then imported into the peroxisome via the membrane-bound protein complex formed by Pex13 and Pex14. Surprisingly, whilst Pex5 is clearly identifiable, Pex13 and, perhaps, Pex14 are apparently absent from the coccidian genomes. To investigate the functionality of the PTS1 import mechanism in these parasites, expression of Pex5 from the model coccidian Toxoplasma gondii was shown to rescue the import defect of Pex5-deleted Saccharomyces cerevisiae. In support of these data, green fluorescent protein (GFP) bearing the enhanced (e)PTS1 known to efficiently localise to peroxisomes in yeast, localised to peroxisome-like bodies when expressed in Toxoplasma. Furthermore, the PTS1-binding domain of Pex5 and a PTS1 ligand from the putatively peroxisome-localised Toxoplasma sterol carrier protein (SCP2) were shown to interact in vitro. Taken together, these data demonstrate that the Pex5–PTS1 interaction is functional in the coccidia and indicate that a nonconventional peroxisomal import mechanism may operate in the absence of Pex13 and Pex14.
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20
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Vázquez-Iglesias L, Estefanell-Ucha B, Barcia-Castro L, Páez de la Cadena M, Álvarez-Chaver P, Ayude-Vázquez D, Rodríguez-Berrocal FJ. A simple electroelution method for rapid protein purification: isolation and antibody production of alpha toxin from Clostridium septicum. PeerJ 2017; 5:e3407. [PMID: 28652930 PMCID: PMC5483040 DOI: 10.7717/peerj.3407] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2017] [Accepted: 05/11/2017] [Indexed: 12/16/2022] Open
Abstract
Clostridium septicum produces a number of diseases in human and farm animals which, in most of the cases, are fatal without clinical intervention. Alpha toxin is an important agent and the unique lethal virulent factor produced by Clostridium septicum. This toxin is haemolytic, highly lethal and necrotizing activities but is being used as an antigen to develop animal vaccines. The aim of this study was to isolate the alpha toxin of Clostridium septicum and produce highly specific antibodies against it. In this work, we have developed a simple and efficient method for alpha toxin purification, based on electroelution that can be used as a time-saving method for purifying proteins. This technique avoids contamination by other proteins that could appear during other protein purification techniques such chromatography. The highly purified toxin was used to produce polyclonal antibodies. The specificity of the antibodies was tested by western blot and these antibodies can be applied to the quantitative determination of alpha toxin by slot blot.
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Affiliation(s)
- Lorena Vázquez-Iglesias
- Department of Biochemistry, Genetics and Immunology, Facultad de Biología, Universidad de Vigo, Vigo, Spain
| | - Borja Estefanell-Ucha
- Department of Biochemistry, Genetics and Immunology, Facultad de Biología, Universidad de Vigo, Vigo, Spain
| | - Leticia Barcia-Castro
- Department of Biochemistry, Genetics and Immunology, Facultad de Biología, Universidad de Vigo, Vigo, Spain
| | - María Páez de la Cadena
- Department of Biochemistry, Genetics and Immunology, Facultad de Biología, Universidad de Vigo, Vigo, Spain
| | - Paula Álvarez-Chaver
- Unidad de Proteómica, Servicio de Determinación Estructural, Proteómica y Genómica, CACTI, Universidad de Vigo, Spain
| | - Daniel Ayude-Vázquez
- Department of Biochemistry, Genetics and Immunology, Facultad de Biología, Universidad de Vigo, Vigo, Spain
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21
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Calmodulin-like proteins localized to the conoid regulate motility and cell invasion by Toxoplasma gondii. PLoS Pathog 2017; 13:e1006379. [PMID: 28475612 PMCID: PMC5435356 DOI: 10.1371/journal.ppat.1006379] [Citation(s) in RCA: 59] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2017] [Revised: 05/17/2017] [Accepted: 04/26/2017] [Indexed: 01/09/2023] Open
Abstract
Toxoplasma gondii contains an expanded number of calmodulin (CaM)-like proteins whose functions are poorly understood. Using a combination of CRISPR/Cas9-mediated gene editing and a plant-like auxin-induced degron (AID) system, we examined the roles of three apically localized CaMs. CaM1 and CaM2 were individually dispensable, but loss of both resulted in a synthetic lethal phenotype. CaM3 was refractory to deletion, suggesting it is essential. Consistent with this prediction auxin-induced degradation of CaM3 blocked growth. Phenotypic analysis revealed that all three CaMs contribute to parasite motility, invasion, and egress from host cells, and that they act downstream of microneme and rhoptry secretion. Super-resolution microscopy localized all three CaMs to the conoid where they overlap with myosin H (MyoH), a motor protein that is required for invasion. Biotinylation using BirA fusions with the CaMs labeled a number of apical proteins including MyoH and its light chain MLC7, suggesting they may interact. Consistent with this hypothesis, disruption of MyoH led to degradation of CaM3, or redistribution of CaM1 and CaM2. Collectively, our findings suggest these CaMs may interact with MyoH to control motility and cell invasion. One of the most common motifs that binds calcium to transduce intracellular signals is called an EF hand- named after the globular domain structure first characterized in ovalbumin. A conserved cluster of four EF hands, each of which that binds one calcium atom, is a conserved feature of calmodulin, centrins, and calmodulin-like proteins, including myosin light chains. Although the presence of EF hands is predictive of calcium binding, it alone does not allow classification of biological function as this set of conserved proteins have very diverse functions. Here we used modified editing procedures based on CRISPR/Cas9 combined with a plant-like degradation system to define the roles of three calmodulin-like proteins in T. gondii. These proteins all localized to a specialized apical structure called the conoid where they overlap with the motor protein called MyoH. Additionally, biochemical and genetic studies suggest they coordinately regulate cell invasion. These new genomic editing tools, combined with an efficient system for protein degradation, expand the functional tool kit for an analysis of essential genes and proteins in T. gondii.
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22
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Chen AL, Moon AS, Bell HN, Huang AS, Vashisht AA, Toh JY, Lin AH, Nadipuram SM, Kim EW, Choi CP, Wohlschlegel JA, Bradley PJ. Novel insights into the composition and function of the Toxoplasma IMC sutures. Cell Microbiol 2017; 19:10.1111/cmi.12678. [PMID: 27696623 PMCID: PMC5909696 DOI: 10.1111/cmi.12678] [Citation(s) in RCA: 46] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2016] [Revised: 08/19/2016] [Accepted: 09/28/2016] [Indexed: 12/29/2022]
Abstract
The Toxoplasma inner membrane complex (IMC) is a specialized organelle underlying the parasite's plasma membrane that consists of flattened rectangular membrane sacs that are sutured together and positioned atop a supportive cytoskeleton. We have previously identified a novel class of proteins localizing to the transverse and longitudinal sutures of the IMC, which we named IMC sutures components (ISCs). Here, we have used proximity-dependent biotin identification at the sutures to better define the composition of this IMC subcompartment. Using ISC4 as bait, we demonstrate biotin-dependent labeling of the sutures and have uncovered two new ISCs. We also identified five new proteins that exclusively localize to the transverse sutures that we named transverse sutures components (TSCs), demonstrating that components of the IMC sutures consist of two groups: those that localize to the transverse and longitudinal sutures (ISCs) and those residing only in the transverse sutures (TSCs). In addition, we functionally analyze the ISC protein ISC3 and demonstrate that ISC3-null parasites have morphological defects and reduced fitness in vitro. Most importantly, Δisc3 parasites exhibit a complete loss of virulence in vivo. These studies expand the known composition of the IMC sutures and highlight the contribution of ISCs to the ability of the parasite to proliferate and cause disease.
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Affiliation(s)
- Allan L. Chen
- Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, Los Angeles, California, USA 90095
| | - Andy S. Moon
- Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, Los Angeles, California, USA 90095
| | - Hannah N. Bell
- Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, Los Angeles, California, USA 90095
| | - Amy S. Huang
- Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, Los Angeles, California, USA 90095
| | - Ajay A. Vashisht
- Department of Biological Chemistry and Institute of Genomics and Proteomics, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California, USA 90095
| | - Justin Y. Toh
- Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, Los Angeles, California, USA 90095
| | - Andrew H. Lin
- Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, Los Angeles, California, USA 90095
| | - Santhosh M. Nadipuram
- Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, Los Angeles, California, USA 90095
| | - Elliot W. Kim
- Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, Los Angeles, California, USA 90095
- Molecular Biology Institute, University of California, Los Angeles, Los Angeles, California, USA 90095
| | - Charles P. Choi
- Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, Los Angeles, California, USA 90095
- Molecular Biology Institute, University of California, Los Angeles, Los Angeles, California, USA 90095
| | - James A. Wohlschlegel
- Department of Biological Chemistry and Institute of Genomics and Proteomics, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California, USA 90095
- Molecular Biology Institute, University of California, Los Angeles, Los Angeles, California, USA 90095
| | - Peter J. Bradley
- Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, Los Angeles, California, USA 90095
- Molecular Biology Institute, University of California, Los Angeles, Los Angeles, California, USA 90095
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Mitochondrial behaviour throughout the lytic cycle of Toxoplasma gondii. Sci Rep 2017; 7:42746. [PMID: 28202940 PMCID: PMC5311943 DOI: 10.1038/srep42746] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2016] [Accepted: 01/12/2017] [Indexed: 01/11/2023] Open
Abstract
Mitochondria distribution in cells controls cellular physiology in health and disease. Here we describe the mitochondrial morphology and positioning found in the different stages of the lytic cycle of the eukaryotic single-cell parasite Toxoplasma gondii. The lytic cycle, driven by the tachyzoite life stage, is responsible for acute toxoplasmosis. It is known that whilst inside a host cell the tachyzoite maintains its single mitochondrion at its periphery. We found that upon parasite transition from the host cell to the extracellular matrix, mitochondrion morphology radically changes, resulting in a reduction in peripheral proximity. This change is reversible upon return to the host, indicating that an active mechanism maintains the peripheral positioning found in the intracellular stages. Comparison between the two states by electron microscopy identified regions of coupling between the mitochondrion outer membrane and the parasite pellicle, whose features suggest the presence of membrane contact sites, and whose abundance changes during the transition between intra- and extra-cellular states. These novel observations pave the way for future research to identify molecular mechanisms involved in mitochondrial distribution in Toxoplasma and the consequences of these mitochondrion changes on parasite physiology.
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Jia Y, Benjamin S, Liu Q, Xu Y, Dogga SK, Liu J, Matthews S, Soldati-Favre D. Toxoplasma gondii immune mapped protein 1 is anchored to the inner leaflet of the plasma membrane and adopts a novel protein fold. BIOCHIMICA ET BIOPHYSICA ACTA. PROTEINS AND PROTEOMICS 2017; 1865:208-219. [PMID: 27888074 PMCID: PMC5716462 DOI: 10.1016/j.bbapap.2016.11.010] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/23/2016] [Revised: 11/14/2016] [Accepted: 11/21/2016] [Indexed: 01/30/2023]
Abstract
The immune mapped protein 1 (IMP1) was first identified as a protective antigen in Eimeria maxima and described as vaccine candidate and invasion factor in Toxoplasma gondii. We show here that TgIMP1 localizes to the inner leaflet of plasma membrane (PM) via dual acylation. Mutations either in the N-terminal myristoylation or palmitoylation sites (G2 and C5) cause relocalization of TgIMP1 to the cytosol. The first 11 amino acids are sufficient for PM targeting and the presence of lysine (K7) is critical. Disruption of TgIMP1 gene by double homologous recombination revealed no invasion defect or any measurable alteration in the lytic cycle of tachyzoites. Following immunization with TgIMP1 DNA vaccine, mice challenged with either wild type or IMP1-ko parasites showed no significant difference in protection. The sequence analysis identified a structured C-terminal domain that is present in a broader family of IMP1-like proteins conserved across the members of Apicomplexa. We present the solution structure of this domain determined from NMR data and describe a new protein fold not seen before.
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Affiliation(s)
- Yonggen Jia
- Department of Microbiology and Molecular Medicine, CMU, University of Geneva, Rue Michel-Servet 1, CH-1211 Geneva, Switzerland
| | - Stefi Benjamin
- Department of Life Sciences, Imperial College London, South Kensington, London SW7 2AZ, UK
| | - Qun Liu
- Key Laboratory of Animal Epidemiology and Zoonosis, Ministry of Agriculture, College of Veterinary Medicine, China Agricultural University, Beijing 100193, China
| | - Yingqi Xu
- Department of Life Sciences, Imperial College London, South Kensington, London SW7 2AZ, UK
| | - Sunil Kumar Dogga
- Department of Microbiology and Molecular Medicine, CMU, University of Geneva, Rue Michel-Servet 1, CH-1211 Geneva, Switzerland
| | - Jing Liu
- Key Laboratory of Animal Epidemiology and Zoonosis, Ministry of Agriculture, College of Veterinary Medicine, China Agricultural University, Beijing 100193, China
| | - Stephen Matthews
- Department of Life Sciences, Imperial College London, South Kensington, London SW7 2AZ, UK.
| | - Dominique Soldati-Favre
- Department of Microbiology and Molecular Medicine, CMU, University of Geneva, Rue Michel-Servet 1, CH-1211 Geneva, Switzerland.
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Abstract
The inner membrane complex (IMC) of Toxoplasma gondii is a peripheral membrane system that is composed of flattened alveolar sacs that underlie the plasma membrane, coupled to a supporting cytoskeletal network. The IMC plays important roles in parasite replication, motility, and host cell invasion. Despite these central roles in the biology of the parasite, the proteins that constitute the IMC are largely unknown. In this study, we have adapted a technique named proximity-dependent biotin identification (BioID) for use in T. gondii to identify novel components of the IMC. Using IMC proteins in both the alveoli and the cytoskeletal network as bait, we have uncovered a total of 19 new IMC proteins in both of these suborganellar compartments, two of which we functionally evaluate by gene knockout. Importantly, labeling of IMC proteins using this approach has revealed a group of proteins that localize to the sutures of the alveolar sacs that have been seen in their entirety in Toxoplasma species only by freeze fracture electron microscopy. Collectively, our study greatly expands the repertoire of known proteins in the IMC and experimentally validates BioID as a strategy for discovering novel constituents of specific cellular compartments of T. gondii. The identification of binding partners is critical for determining protein function within cellular compartments. However, discovery of protein-protein interactions within membrane or cytoskeletal compartments is challenging, particularly for transient or unstable interactions that are often disrupted by experimental manipulation of these compartments. To circumvent these problems, we adapted an in vivo biotinylation technique called BioID for Toxoplasma species to identify binding partners and proximal proteins within native cellular environments. We used BioID to identify 19 novel proteins in the parasite IMC, an organelle consisting of fused membrane sacs and an underlying cytoskeleton, whose protein composition is largely unknown. We also demonstrate the power of BioID for targeted discovery of proteins within specific compartments, such as the IMC cytoskeleton. In addition, we uncovered a new group of proteins localizing to the alveolar sutures of the IMC. BioID promises to reveal new insights on protein constituents and interactions within cellular compartments of Toxoplasma.
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Garcia JP, Moore J, Loukopoulos P, Diab SS, Uzal FA. Necrotizing gastritis associated with Clostridium septicum in a rabbit. J Vet Diagn Invest 2014; 26:669-73. [DOI: 10.1177/1040638714547255] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Clostridium septicum is the causative agent of histotoxic infections, including malignant edema and braxy (necrotizing abomasitis) in several animal species. The carcass of a 2-year–old, female New Zealand white rabbit with a history of acute depression and obtundation followed by death was received at the California Animal Health and Food Safety Laboratory System (San Bernardino, California) for necropsy and diagnostic workup. No gross lesions were detected at necropsy. Microscopically, there was moderate to severe, multifocal fibrinonecrotizing, transmural gastritis with numerous intralesional Gram-positive, sporulated rods, and disseminated thrombosis of the brain, lungs, heart, and liver, with occasional intravascular rods. The rods observed within the gastric wall and thrombi in the stomach and lung were positive for C. septicum by immunohistochemical staining. However, this microorganism was not isolated from stomach content. Clostridium septicum should be included in the list of possible etiologies of gastritis in rabbits.
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Affiliation(s)
- Jorge P. Garcia
- California Animal Health and Food Safety Laboratory System, School of Veterinary Medicine, University of California Davis, San Bernardino, CA
| | - Janet Moore
- California Animal Health and Food Safety Laboratory System, School of Veterinary Medicine, University of California Davis, San Bernardino, CA
| | - Panayiotis Loukopoulos
- California Animal Health and Food Safety Laboratory System, School of Veterinary Medicine, University of California Davis, San Bernardino, CA
| | - Santiago S. Diab
- California Animal Health and Food Safety Laboratory System, School of Veterinary Medicine, University of California Davis, San Bernardino, CA
| | - Francisco A. Uzal
- California Animal Health and Food Safety Laboratory System, School of Veterinary Medicine, University of California Davis, San Bernardino, CA
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27
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Abstract
Unlike most cells, protozoa in the phylum Apicomplexa divide by a distinctive process in which multiple daughters are assembled within the mother (schizogony or endodyogeny), using scaffolding known as the inner membrane complex (IMC). The IMC underlies the plasma membrane during interphase, but new daughters develop in the cytoplasm, as cytoskeletal filaments associate with flattened membrane cisternae (alveolae), which elongate rapidly to encapsulate subcellular organelles. Newly assembled daughters acquire their plasma membrane as they emerge from the mother, leaving behind vestiges of the maternal cell. Although the maternal plasma membrane remains intact throughout this process, the maternal IMC disappears – is it degraded, or recycled to form the daughter IMC? Exploiting fluorescently tagged IMC markers, we have used live-cell imaging, fluorescence recovery after photobleaching (FRAP) and mEos2 photoactivation to monitor the dynamics of IMC biogenesis and turnover during the replication of Toxoplasma gondii tachyzoites. These studies reveal that the formation of the T. gondii IMC involves two distinct steps – de novo assembly during daughter IMC elongation within the mother cell, followed by recycling of maternal IMC membranes after the emergence of daughters from the mother cell.
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Affiliation(s)
- Dinkorma T Ouologuem
- Department of Biology, University of Pennsylvania, Philadelphia, PA 19104, USA Malaria Research & Training Centre, Department of Epidemiology of Parasitic Diseases, Bamako, BP 1805, Mali
| | - David S Roos
- Department of Biology, University of Pennsylvania, Philadelphia, PA 19104, USA
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28
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Harding CR, Meissner M. The inner membrane complex through development of Toxoplasma gondii and Plasmodium. Cell Microbiol 2014; 16:632-41. [PMID: 24612102 PMCID: PMC4286798 DOI: 10.1111/cmi.12285] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2014] [Revised: 02/20/2014] [Accepted: 02/20/2014] [Indexed: 12/30/2022]
Abstract
Plasmodium spp. and Toxoplasma gondii are important human and veterinary pathogens. These parasites possess an unusual double membrane structure located directly below the plasma membrane named the inner membrane complex (IMC). First identified in early electron micrograph studies, huge advances in genetic manipulation of the Apicomplexa have allowed the visualization of a dynamic, highly structured cellular compartment with important roles in maintaining the structure and motility of these parasites. This review summarizes recent advances in the field and highlights the changes the IMC undergoes during the complex life cycles of the Apicomplexa.
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Affiliation(s)
- Clare R Harding
- Wellcome Trust Centre for Molecular Parasitology, Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, The University of Glasgow, Glasgow, UK
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Mukamoto M, Kimura R, Hang'ombe MB, Kohda T, Kozaki S. Analysis of tryptophan-rich region in Clostridium septicum alpha-toxin involved with binding to glycosylphosphatidylinositol-anchored proteins. Microbiol Immunol 2013; 57:163-9. [PMID: 23278518 DOI: 10.1111/1348-0421.12017] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2012] [Revised: 11/18/2012] [Accepted: 12/06/2012] [Indexed: 11/27/2022]
Abstract
Clostridium septicum alpha-toxin has a unique tryptophan-rich region ((302)NGYSEWDWKWV(312)) that consists of 11 amino acid residues near the C-terminus. Using mutant toxins, the contribution of individual amino acids in the tryptophan-rich region to cytotoxicity and binding to glycosylphosphatidylinositol (GPI)-anchored proteins was examined. For retention of maximum cytotoxic activity, W307 and W311 are essential residues and residue 309 has to be hydrophobic and possess an aromatic side chain, such as tryptophan or phenylalanine. When residue 308, which lies between tryptophans (W307 and W309) is changed from an acidic to a basic amino acid, the cytotoxic activity of the mutant is reduced to less than that of the wild type. It was shown by a toxin overlay assay that the cytotoxic activity of each mutant toxin correlates closely with affinity to GPI-anchored proteins. These findings indicate that the WDW_W sequence in the tryptophan-rich region plays an important role in the cytotoxic mechanism of alpha-toxin, especially in the binding to GPI-anchored proteins as cell receptors.
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Affiliation(s)
- Masafumi Mukamoto
- Laboratory of Veterinary Epidemiology, Department of Veterinary Science, Graduate School of Life and Environmental Sciences, Osaka Prefecture University, 1-58 Rinku Orai-kita, Izumisano, Osaka, 598-8531, Japan. ‐u.ac.jp
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30
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De Napoli MG, de Miguel N, Lebrun M, Moreno SNJ, Angel SO, Corvi MM. N-terminal palmitoylation is required for Toxoplasma gondii HSP20 inner membrane complex localization. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2013; 1833:1329-37. [PMID: 23485398 DOI: 10.1016/j.bbamcr.2013.02.022] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/23/2012] [Revised: 02/14/2013] [Accepted: 02/19/2013] [Indexed: 12/11/2022]
Abstract
Toxoplasma gondii is an obligate intracellular parasite and the causative agent of toxoplasmosis. Protein palmitoylation is known to play roles in signal transduction and in enhancing the hydrophobicity of proteins thus contributing to their membrane association. Global inhibition of protein palmitoylation has been shown to affect T. gondii physiology and invasion of the host cell. However, the proteins affected by this modification have been understudied. This paper shows that the small heat shock protein 20 from T. gondii (TgHSP20) is synthesized as a mature protein in the cytosol and is palmitoylated in three cysteine residues. However, its localization at the inner membrane complex (IMC) is dependent only on N-terminal palmitoylation. Absence or incomplete N-terminal palmitoylation causes TgHSP20 to partially accumulate in a membranous structure. Interestingly, TgHSP20 palmitoylation is not responsible for its interaction with the daughter cells IMCs. Together, our data describe the importance of palmitoylation in protein targeting to the IMC in T. gondii.
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Affiliation(s)
- M G De Napoli
- Universidad Nacional de San Martín, Consejo Nacional de Investigaciones Científicas y Técnicas, Provincia de Buenos Aires, Argentina
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31
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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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Tsai YH, Liu X, Seeberger PH. Chemical biology of glycosylphosphatidylinositol anchors. Angew Chem Int Ed Engl 2012; 51:11438-56. [PMID: 23086912 DOI: 10.1002/anie.201203912] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2012] [Indexed: 01/21/2023]
Abstract
Glycosylphosphatidylinositols (GPIs) are complex glycolipids that are covalently linked to the C-terminus of proteins as a posttranslational modification. They anchor the attached protein to the cell membrane and are essential for normal functioning of eukaryotic cells. GPI-anchored proteins are structurally and functionally diverse. Many GPIs have been structurally characterized but comprehension of their biological functions, beyond the simple physical anchoring, remains largely speculative. Work on functional elucidation at a molecular level is still limited. This Review focuses on the roles of GPI unraveled by using synthetic molecules and summarizes the structural diversity of GPIs, as well as their biological and chemical syntheses.
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Affiliation(s)
- Yu-Hsuan Tsai
- Department of Biomolecular Systems, Max Planck Institute of Colloids and Interfaces, Am Mühlenberg 1, 14424 Potsdam, Germany
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34
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Tsai YH, Liu X, Seeberger PH. Chemische Biologie der Glycosylphosphatidylinosit-Anker. Angew Chem Int Ed Engl 2012. [DOI: 10.1002/ange.201203912] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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35
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Rabbit antibodies against Toxoplasma Hsp20 are able to reduce parasite invasion and gliding motility in Toxoplasma gondii and parasite invasion in Neospora caninum. Exp Parasitol 2012; 132:274-81. [DOI: 10.1016/j.exppara.2012.08.003] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2011] [Revised: 06/14/2012] [Accepted: 08/01/2012] [Indexed: 11/21/2022]
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36
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Fung C, Beck JR, Robertson SD, Gubbels MJ, Bradley PJ. Toxoplasma ISP4 is a central IMC sub-compartment protein whose localization depends on palmitoylation but not myristoylation. Mol Biochem Parasitol 2012; 184:99-108. [PMID: 22659420 DOI: 10.1016/j.molbiopara.2012.05.002] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2012] [Revised: 05/21/2012] [Accepted: 05/22/2012] [Indexed: 12/30/2022]
Abstract
Apicomplexan parasites utilize a peripheral membrane system called the inner membrane complex (IMC) to facilitate host cell invasion and parasite replication. We recently identified a novel family of Toxoplasma IMC Sub-compartment Proteins (ISP1/2/3) that localize to sub-domains of the IMC using a targeting mechanism that is dependent on coordinated myristoylation and palmitoylation of a series of residues in the N-terminus of the protein. While the precise functions of the ISPs are unknown, deletion of ISP2 results in replication defects, suggesting that this family of proteins plays a role in daughter cell formation. Here we have characterized a fourth ISP family member (ISP4) and discovered that this protein localizes to the central IMC sub-compartment, similar to ISP2. Like ISP1/3, ISP4 is dispensable for the tachyzoite lytic cycle as the disruption of ISP4 does not produce any gross replication or growth defects. Surprisingly, targeting of ISP4 to the IMC membranes is dependent on residues predicted for palmitoylation but not myristoylation, setting its trafficking apart from the other ISP proteins and demonstrating distinct mechanisms of protein localization to the IMC membranes, even within a family of highly related proteins.
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Affiliation(s)
- Connie Fung
- Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, Los Angeles, CA 90095-1489, USA
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Türkcan S, Masson JB, Casanova D, Mialon G, Gacoin T, Boilot JP, Popoff MR, Alexandrou A. Observing the confinement potential of bacterial pore-forming toxin receptors inside rafts with nonblinking Eu(3+)-doped oxide nanoparticles. Biophys J 2012; 102:2299-308. [PMID: 22677383 DOI: 10.1016/j.bpj.2012.03.072] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2011] [Revised: 03/20/2012] [Accepted: 03/23/2012] [Indexed: 12/26/2022] Open
Abstract
We track single toxin receptors on the apical cell membrane of MDCK cells with Eu-doped oxide nanoparticles coupled to two toxins of the pore-forming toxin family: α-toxin of Clostridium septicum and ε-toxin of Clostridium perfringens. These nonblinking and photostable labels do not perturb the motion of the toxin receptors and yield long uninterrupted trajectories with mean localization precision of 30 nm for acquisition times of 51.3 ms. We were thus able to study the toxin-cell interaction at the single-molecule level. Toxins bind to receptors that are confined within zones of mean area 0.40 ± 0.05 μm(2). Assuming that the receptors move according to the Langevin equation of motion and using Bayesian inference, we determined mean diffusion coefficients of 0.16 ± 0.01 μm(2)/s for both toxin receptors. Moreover, application of this approach revealed a force field within the domain generated by a springlike confining potential. Both toxin receptors were found to experience forces characterized by a mean spring constant of 0.30 ± 0.03 pN/μm at 37°C. Furthermore, both toxin receptors showed similar distributions of diffusion coefficient, domain area, and spring constant. Control experiments before and after incubation with cholesterol oxidase and sphingomyelinase show that these two enzymes disrupt the confinement domains and lead to quasi-free motion of the toxin receptors. Our control data showing cholesterol and sphingomyelin dependence as well as independence of actin depolymerization and microtubule disruption lead us to attribute the confinement of both receptors to lipid rafts. These toxins require oligomerization to develop their toxic activity. The confined nature of the toxin receptors leads to a local enhancement of the toxin monomer concentration and may thus explain the virulence of this toxin family.
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Affiliation(s)
- Silvan Türkcan
- Laboratoire d'Optique et Biosciences, Ecole Polytechnique, Centre National de la Recherche Scientifique, Institut National de la Santé et de la Recherche Médicale U696, Palaiseau, France.
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Khosroshahi KH, Ghaffarifar F, Sharifi Z, D'Souza S, Dalimi A, Hassan ZM, Khoshzaban F. Comparing the effect of IL-12 genetic adjuvant and alum non-genetic adjuvant on the efficiency of the cocktail DNA vaccine containing plasmids encoding SAG-1 and ROP-2 of Toxoplasma gondii. Parasitol Res 2012; 111:403-11. [PMID: 22350714 DOI: 10.1007/s00436-012-2852-7] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/25/2010] [Accepted: 02/02/2012] [Indexed: 11/28/2022]
Abstract
Various methods are available for enhancing the potency of DNA vaccines, including employment of different forms of adjuvant. The current study was carried out to evaluate and compare the effects of genetic and non-genetic adjuvants on the immune response stimulated by DNA vaccine. Thus, two adjuvants, IL-12 (genetic adjuvant) and aluminum hydroxide (alum, non-genetic adjuvant), were used with cocktail DNA vaccine containing plasmids encoding complete rhoptry antigen 2 (ROP-2) and surface major antigen 1 (SAG-1) of Toxoplasma gondii. The efficacy of pcROP2+pcSAG1 in stimulation of the immune response against toxoplasmosis with and without adjuvant was evaluated in female BALB/c mice by measuring the level of total IgG antibody and cytokines. The results obtained indicated that after challenging the mice with the fatal RH strain of T. gondii, the survival rates of mice immunized with pcROP2+pcSAG1 (DNA cocktail), pcSAG1+pcROP2+alum, and pcSAG1+pcROP2+IL-12 were significantly greater than that of the control groups (p<0.05). Moreover, measurement of total IgG antibody indicated the significant difference between the control and experimental groups (p<0.05). Finally, the results obtained by measurement of cytokines (IFN-γ and IL-4) showed high levels of IFN-γ and low levels of IL-4 in groups vaccinated with pcROP2+pcSAG1 (DNA cocktail), pcSAG1+pcROP2+alum, and pcSAG1+pcROP2+IL-12 as the experiment groups, in comparison with the controls groups (PBS, pc-DNA3, alum+PBS, and pCAGGS-IL-12+pcDNA3). The results of the study showed that use of adjuvants (IL-12 and alum) coincident with DNA cocktail leads to significant change in the survival rates of the experiment groups in comparison with control groups. Also, there is no significant difference between adjuvants to induce immune responses.
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Targeted disruption of TgPhIL1 in Toxoplasma gondii results in altered parasite morphology and fitness. PLoS One 2011; 6:e23977. [PMID: 21901148 PMCID: PMC3162014 DOI: 10.1371/journal.pone.0023977] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2011] [Accepted: 08/01/2011] [Indexed: 01/08/2023] Open
Abstract
The inner membrane complex (IMC), a series of flattened vesicles at the periphery of apicomplexan parasites, is thought to be important for parasite shape, motility and replication, but few of the IMC proteins that function in these processes have been identified. TgPhIL1, a Toxoplasma gondii protein that was previously identified through photosensitized labeling with 5-[125I] iodonapthaline-1-azide, associates with the IMC and/or underlying cytoskeleton and is concentrated at the apical end of the parasite. Orthologs of TgPhIL1 are found in other apicomplexans, but the function of this conserved protein family is unknown. As a first step towards determining the function of TgPhIL1 and its orthologs, we generated a T. gondii parasite line in which the single copy of TgPhIL1 was disrupted by homologous recombination. The TgPhIL1 knockout parasites have a distinctly different morphology than wild-type parasites, and normal shape is restored in the knockout background after complementation with the wild-type allele. The knockout parasites are outcompeted in culture by parasites expressing functional TgPhIL1, and they generate a reduced parasite load in the spleen and liver of infected mice. These findings demonstrate a role for TgPhIL1 in the morphology, growth and fitness of T. gondii tachyzoites.
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Frénal K, Polonais V, Marq JB, Stratmann R, Limenitakis J, Soldati-Favre D. Functional dissection of the apicomplexan glideosome molecular architecture. Cell Host Microbe 2011; 8:343-57. [PMID: 20951968 DOI: 10.1016/j.chom.2010.09.002] [Citation(s) in RCA: 208] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2010] [Revised: 07/26/2010] [Accepted: 09/03/2010] [Indexed: 11/24/2022]
Abstract
The glideosome of apicomplexan parasites is an actin- and myosin-based machine located at the pellicle, between the plasma membrane (PM) and inner membrane complex (IMC), that powers parasite motility, migration, and host cell invasion and egress. It is composed of myosin A, its light chain MLC1, and two gliding-associated proteins, GAP50 and GAP45. We identify GAP40, a polytopic protein of the IMC, as an additional glideosome component and show that GAP45 is anchored to the PM and IMC via its N- and C-terminal extremities, respectively. While the C-terminal region of GAP45 recruits MLC1-MyoA to the IMC, the N-terminal acylation and coiled-coil domain preserve pellicle integrity during invasion. GAP45 is essential for gliding, invasion, and egress. The orthologous Plasmodium falciparum GAP45 can fulfill this dual function, as shown by transgenera complementation, whereas the coccidian GAP45 homolog (designated here as) GAP70 specifically recruits the glideosome to the apical cap of the parasite.
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Affiliation(s)
- Karine Frénal
- Department of Microbiology and Molecular Medicine, Centre Medical Universitaire, University of Geneva, CH-1211 Geneva 4, Switzerland
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Polonais V, Javier Foth B, Chinthalapudi K, Marq JB, Manstein DJ, Soldati-Favre D, Frénal K. Unusual anchor of a motor complex (MyoD-MLC2) to the plasma membrane of Toxoplasma gondii. Traffic 2011; 12:287-300. [PMID: 21143563 DOI: 10.1111/j.1600-0854.2010.01148.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Toxoplasma gondii possesses 11 rather atypical myosin heavy chains. The only myosin light chain described to date is MLC1, associated with myosin A, and contributing to gliding motility. In this study, we examined the repertoire of calmodulin-like proteins in Apicomplexans, identified six putative myosin light chains and determined their subcellular localization in T. gondii and Plasmodium falciparum. MLC2, only found in coccidians, is associated with myosin D via its calmodulin (CaM)-like domain and anchored to the plasma membrane of T. gondii via its N-terminal extension. Molecular modeling suggests that the MyoD-MLC2 complex is more compact than the reported structure of Plasmodium MyoA-myosin A tail-interacting protein (MTIP) complex. Anchorage of this MLC2 to the plasma membrane is likely governed by palmitoylation.
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Affiliation(s)
- Valérie Polonais
- Department of Microbiology and Molecular Medicine, CMU, University of Geneva, 1 Rue Michel-Servet, CH-1211 Geneva 4, Switzerland
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Daher W, Plattner F, Carlier MF, Soldati-Favre D. Concerted action of two formins in gliding motility and host cell invasion by Toxoplasma gondii. PLoS Pathog 2010; 6:e1001132. [PMID: 20949068 PMCID: PMC2951370 DOI: 10.1371/journal.ppat.1001132] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2010] [Accepted: 09/06/2010] [Indexed: 12/22/2022] Open
Abstract
The invasive forms of apicomplexan parasites share a conserved form of gliding motility that powers parasite migration across biological barriers, host cell invasion and egress from infected cells. Previous studies have established that the duration and direction of gliding motility are determined by actin polymerization; however, regulators of actin dynamics in apicomplexans remain poorly characterized. In the absence of a complete ARP2/3 complex, the formin homology 2 domain containing proteins and the accessory protein profilin are presumed to orchestrate actin polymerization during host cell invasion. Here, we have undertaken the biochemical and functional characterization of two Toxoplasma gondii formins and established that they act in concert as actin nucleators during invasion. The importance of TgFRM1 for parasite motility has been assessed by conditional gene disruption. The contribution of each formin individually and jointly was revealed by an approach based upon the expression of dominant mutants with modified FH2 domains impaired in actin binding but still able to dimerize with their respective endogenous formin. These mutated FH2 domains were fused to the ligand-controlled destabilization domain (DD-FKBP) to achieve conditional expression. This strategy proved unique in identifying the non-redundant and critical roles of both formins in invasion. These findings provide new insights into how controlled actin polymerization drives the directional movement required for productive penetration of parasites into host cells. Gliding motility is a unique property of the Apicomplexa. Members of this phylum include important human and animal pathogens. An actomyosin-based machine powers parasite motility and is crucial for parasite migration across biological barriers, host cell invasion and egress from infected cells. The timing, duration and orientation of the gliding motility are tightly regulated to insure successful establishment of infection. Controlled polymerization of actin filaments is a key feature of motility, and we demonstrate here the implication of two formins that catalyse actin nucleation and fast assembly of filaments. Both proteins are essential and act in concert during productive penetration of the parasite into host cells.
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Affiliation(s)
- Wassim Daher
- Department of Microbiology and Molecular Medicine, CMU, University of Geneva, Geneva, Switzerland
| | - Fabienne Plattner
- Department of Microbiology and Molecular Medicine, CMU, University of Geneva, Geneva, Switzerland
| | - Marie-France Carlier
- Dynamique du Cytosquelette, Laboratoire d'Enzymologie et Biochimie Structurales UPR A 9063, CNRS, Gif sur Yvette, France
| | - Dominique Soldati-Favre
- Department of Microbiology and Molecular Medicine, CMU, University of Geneva, Geneva, Switzerland
- * E-mail:
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Beck JR, Rodriguez-Fernandez IA, Cruz de Leon J, Huynh MH, Carruthers VB, Morrissette NS, Bradley PJ. A novel family of Toxoplasma IMC proteins displays a hierarchical organization and functions in coordinating parasite division. PLoS Pathog 2010; 6:e1001094. [PMID: 20844581 PMCID: PMC2936552 DOI: 10.1371/journal.ppat.1001094] [Citation(s) in RCA: 155] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2010] [Accepted: 08/10/2010] [Indexed: 12/18/2022] Open
Abstract
Apicomplexans employ a peripheral membrane system called the inner membrane complex (IMC) for critical processes such as host cell invasion and daughter cell formation. We have identified a family of proteins that define novel sub-compartments of the Toxoplasma gondii IMC. These IMC Sub-compartment Proteins, ISP1, 2 and 3, are conserved throughout the Apicomplexa, but do not appear to be present outside the phylum. ISP1 localizes to the apical cap portion of the IMC, while ISP2 localizes to a central IMC region and ISP3 localizes to a central plus basal region of the complex. Targeting of all three ISPs is dependent upon N-terminal residues predicted for coordinated myristoylation and palmitoylation. Surprisingly, we show that disruption of ISP1 results in a dramatic relocalization of ISP2 and ISP3 to the apical cap. Although the N-terminal region of ISP1 is necessary and sufficient for apical cap targeting, exclusion of other family members requires the remaining C-terminal region of the protein. This gate-keeping function of ISP1 reveals an unprecedented mechanism of interactive and hierarchical targeting of proteins to establish these unique sub-compartments in the Toxoplasma IMC. Finally, we show that loss of ISP2 results in severe defects in daughter cell formation during endodyogeny, indicating a role for the ISP proteins in coordinating this unique process of Toxoplasma replication.
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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
| | - Imilce A. Rodriguez-Fernandez
- Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, Los Angeles, California, United States of America
| | - Jessica Cruz de Leon
- Department of Molecular Biology and Biochemistry, University of California, Irvine, Irvine, California, United States of America
| | - My-Hang Huynh
- Department of Microbiology and Immunology, University of Michigan School of Medicine, Ann Arbor, Michigan, United States of America
| | - Vern B. Carruthers
- Department of Microbiology and Immunology, University of Michigan School of Medicine, Ann Arbor, Michigan, United States of America
| | - Naomi S. Morrissette
- Department of Molecular Biology and Biochemistry, University of California, Irvine, Irvine, 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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44
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Heaslip AT, Leung JM, Carey KL, Catti F, Warshaw DM, Westwood NJ, Ballif BA, Ward GE. A small-molecule inhibitor of T. gondii motility induces the posttranslational modification of myosin light chain-1 and inhibits myosin motor activity. PLoS Pathog 2010; 6:e1000720. [PMID: 20084115 PMCID: PMC2800044 DOI: 10.1371/journal.ppat.1000720] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2009] [Accepted: 12/10/2009] [Indexed: 11/22/2022] Open
Abstract
Toxoplasma gondii is an obligate intracellular parasite that enters cells by a process of active penetration. Host cell penetration and parasite motility are driven by a myosin motor complex consisting of four known proteins: TgMyoA, an unconventional Class XIV myosin; TgMLC1, a myosin light chain; and two membrane-associated proteins, TgGAP45 and TgGAP50. Little is known about how the activity of the myosin motor complex is regulated. Here, we show that treatment of parasites with a recently identified small-molecule inhibitor of invasion and motility results in a rapid and irreversible change in the electrophoretic mobility of TgMLC1. While the precise nature of the TgMLC1 modification has not yet been established, it was mapped to the peptide Val46-Arg59. To determine if the TgMLC1 modification is responsible for the motility defect observed in parasites after compound treatment, the activity of myosin motor complexes from control and compound-treated parasites was compared in an in vitro motility assay. TgMyoA motor complexes containing the modified TgMLC1 showed significantly decreased motor activity compared to control complexes. This change in motor activity likely accounts for the motility defects seen in the parasites after compound treatment and provides the first evidence, in any species, that the mechanical activity of Class XIV myosins can be modulated by posttranslational modifications to their associated light chains. Toxoplasma gondii and related parasites within the Phylum Apicomplexa are collectively responsible for a great deal of human disease and death worldwide. The ability of apicomplexan parasites to invade cells of their hosts, disseminate through tissues and cause disease depends critically on parasite motility. Motility is driven by a complex of proteins that is well conserved within the phylum; however, very little is known about how the unconventional myosin motor protein at the heart of this motility machinery is regulated. T. gondii serves as a powerful model system for studying apicomplexan motile mechanisms. We show here that a recently identified pharmacological inhibitor of T. gondii motility induces a posttranslational modification of TgMLC1, a protein that binds to the myosin motor protein, TgMyoA. The compound-induced modification of TgMLC1 is associated with a decrease in TgMyoA mechanical activity. These data provide the first glimpse into how TgMyoA is regulated and how a change in the activity of the T. gondii myosin motor complex can affect the motility and infectivity of this important human pathogen.
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Affiliation(s)
- Aoife T. Heaslip
- Department of Microbiology and Molecular Genetics, University of Vermont, Burlington, Vermont, United States of America
| | - Jacqueline M. Leung
- Department of Microbiology and Molecular Genetics, University of Vermont, Burlington, Vermont, United States of America
| | - Kimberly L. Carey
- Department of Microbiology and Molecular Genetics, University of Vermont, Burlington, Vermont, United States of America
| | - Federica Catti
- School of Chemistry and Centre for Biomolecular Sciences, University of St Andrews, North Haugh, St Andrews, Fife, Scotland, United Kingdom
| | - David M. Warshaw
- Department of Molecular Physiology and Biophysics, University of Vermont, Burlington, Vermont, United States of America
| | - Nicholas J. Westwood
- School of Chemistry and Centre for Biomolecular Sciences, University of St Andrews, North Haugh, St Andrews, Fife, Scotland, United Kingdom
| | - Bryan A. Ballif
- Department of Biology and Vermont Genetics Network Proteomics Facility, University of Vermont, Burlington, Vermont, United States of America
| | - Gary E. Ward
- Department of Microbiology and Molecular Genetics, University of Vermont, Burlington, Vermont, United States of America
- * E-mail:
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Abstract
Clostridia produce the highest number of toxins of any type of bacteria and are involved in severe diseases in humans and other animals. Most of the clostridial toxins are pore-forming toxins responsible for gangrenes and gastrointestinal diseases. Among them, perfringolysin has been extensively studied and it is the paradigm of the cholesterol-dependent cytolysins, whereas Clostridium perfringens epsilon-toxin and Clostridium septicum alpha-toxin, which are related to aerolysin, are the prototypes of clostridial toxins that form small pores. Other toxins active on the cell surface possess an enzymatic activity, such as phospholipase C and collagenase, and are involved in the degradation of specific cell-membrane or extracellular-matrix components. Three groups of clostridial toxins have the ability to enter cells: large clostridial glucosylating toxins, binary toxins and neurotoxins. The binary and large clostridial glucosylating toxins alter the actin cytoskeleton by enzymatically modifying the actin monomers and the regulatory proteins from the Rho family, respectively. Clostridial neurotoxins proteolyse key components of neuroexocytosis. Botulinum neurotoxins inhibit neurotransmission at neuromuscular junctions, whereas tetanus toxin targets the inhibitory interneurons of the CNS. The high potency of clostridial toxins results from their specific targets, which have an essential cellular function, and from the type of modification that they induce. In addition, clostridial toxins are useful pharmacological and biological tools.
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Affiliation(s)
- Michel R Popoff
- Institut Pasteur, Bactéries Anaérobies et Toxines, 75724 Paris cedex 15, France.
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46
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Bullen HE, Tonkin CJ, O'Donnell RA, Tham WH, Papenfuss AT, Gould S, Cowman AF, Crabb BS, Gilson PR. A novel family of Apicomplexan glideosome-associated proteins with an inner membrane-anchoring role. J Biol Chem 2009; 284:25353-63. [PMID: 19561073 PMCID: PMC2757237 DOI: 10.1074/jbc.m109.036772] [Citation(s) in RCA: 99] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2009] [Indexed: 11/06/2022] Open
Abstract
The phylum Apicomplexa are a group of obligate intracellular parasites responsible for a wide range of important diseases. Central to the lifecycle of these unicellular parasites is their ability to migrate through animal tissue and invade target host cells. Apicomplexan movement is generated by a unique system of gliding motility in which substrate adhesins and invasion-related proteins are pulled across the plasma membrane by an underlying actin-myosin motor. The myosins of this motor are inserted into a dual membrane layer called the inner membrane complex (IMC) that is sandwiched between the plasma membrane and an underlying cytoskeletal basket. Central to our understanding of gliding motility is the characterization of proteins residing within the IMC, but to date only a few proteins are known. We report here a novel family of six-pass transmembrane proteins, termed the GAPM family, which are highly conserved and specific to Apicomplexa. In Plasmodium falciparum and Toxoplasma gondii the GAPMs localize to the IMC where they form highly SDS-resistant oligomeric complexes. The GAPMs co-purify with the cytoskeletal alveolin proteins and also to some degree with the actin-myosin motor itself. Hence, these proteins are strong candidates for an IMC-anchoring role, either directly or indirectly tethering the motor to the cytoskeleton.
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Affiliation(s)
- Hayley E. Bullen
- From the Macfarlane Burnet Institute for Medical Research & Public Health, 85 Commercial Road, Melbourne, Victoria 3004
- the Department of Medical Biology, The University of Melbourne, Parkville, Victoria 3010
- the Infection and Immunity Division, and
| | | | | | | | - Anthony T. Papenfuss
- the Bioinformatics Division, The Walter & Eliza Hall Institute of Medical Research, 1G Royal Parade, Parkville, Victoria 3050, and
| | - Sven Gould
- the School of Botany, The University of Melbourne, Parkville, Victoria 3050, Australia
| | | | - Brendan S. Crabb
- From the Macfarlane Burnet Institute for Medical Research & Public Health, 85 Commercial Road, Melbourne, Victoria 3004
| | - Paul R. Gilson
- From the Macfarlane Burnet Institute for Medical Research & Public Health, 85 Commercial Road, Melbourne, Victoria 3004
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Knapp O, Maier E, Mkaddem SB, Benz R, Bens M, Chenal A, Geny B, Vandewalle A, Popoff MR. Clostridium septicum alpha-toxin forms pores and induces rapid cell necrosis. Toxicon 2009; 55:61-72. [PMID: 19632260 DOI: 10.1016/j.toxicon.2009.06.037] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2009] [Revised: 06/25/2009] [Accepted: 06/29/2009] [Indexed: 11/25/2022]
Abstract
Alpha-toxin is the unique lethal virulent factor produced by Clostridium septicum, which causes traumatic or non-traumatic gas gangrene and necrotizing enterocolitis in humans. Here, we analyzed channel formation of the recombinant septicum alpha-toxin and characterized its activity on living cells. Recombinant septicum alpha-toxin induces the formation of ion-permeable channels with a single-channel conductance of about 175pS in 0.1M KCl in lipid bilayer membranes, which is typical for a large diffusion pore. Septicum alpha-toxin channels remained mostly in the open configuration, displayed no lipid specificity, and exhibited slight anion selectivity. Septicum alpha-toxin caused a rapid decrease in the transepithelial electrical resistance of MDCK cell monolayers grown on filters, and induced a rapid cell necrosis in a variety of cell lines, characterized by cell permeabilization to propidium iodide without DNA fragmentation and activation of caspase-3. Septicum alpha-toxin also induced a rapid K(+) efflux and ATP depletion. Incubation of the cells in K(+)-enriched medium delayed cell death caused by septicum alpha-toxin or epsilon-toxin, another potent pore-forming toxin, suggesting that the rapid loss of intracellular K(+) represents an early signal of pore-forming toxins-mediated cell necrosis.
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Affiliation(s)
- Oliver Knapp
- Institut Pasteur, Bactéries anaérobies et Toxines, 28 rue du Dr Roux, F-75724 Paris cedex 15, France
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48
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Kennedy CL, Smith DJ, Lyras D, Chakravorty A, Rood JI. Programmed cellular necrosis mediated by the pore-forming alpha-toxin from Clostridium septicum. PLoS Pathog 2009; 5:e1000516. [PMID: 19609357 PMCID: PMC2705182 DOI: 10.1371/journal.ppat.1000516] [Citation(s) in RCA: 90] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2008] [Accepted: 06/19/2009] [Indexed: 02/04/2023] Open
Abstract
Programmed necrosis is a mechanism of cell death that has been described for neuronal excitotoxicity and ischemia/reperfusion injury, but has not been extensively studied in the context of exposure to bacterial exotoxins. The α-toxin of Clostridium septicum is a β-barrel pore-forming toxin and a potent cytotoxin; however, the mechanism by which it induces cell death has not been elucidated in detail. We report that α-toxin formed Ca2+-permeable pores in murine myoblast cells, leading to an increase in intracellular Ca2+ levels. This Ca2+ influx did not induce apoptosis, as has been described for other small pore-forming toxins, but a cascade of events consistent with programmed necrosis. Ca2+ influx was associated with calpain activation and release of cathepsins from lysosomes. We also observed deregulation of mitochondrial activity, leading to increased ROS levels, and dramatically reduced levels of ATP. Finally, the immunostimulatory histone binding protein HMGB1 was found to be released from the nuclei of α-toxin-treated cells. Collectively, these data show that α-toxin initiates a multifaceted necrotic cell death response that is consistent with its essential role in C. septicum-mediated myonecrosis and sepsis. We postulate that cellular intoxication with pore-forming toxins may be a major mechanism by which programmed necrosis is induced. Clostridium septicum is a highly virulent pathogen that causes spontaneous gas gangrene or clostridial myonecrosis. The essential virulence factor of C. septicum is a β-barrel toxin, α-toxin, that forms small pores in host cell membranes. This toxin is frequently described as a hemolysin, because the formation of these pores causes lysis of red blood cell cells due to membrane disruption. However, this description does not recognize additional effects that may be observed in nucleated host cells, which are more sensitive to α-toxin. We investigated how nucleated cells responded to α-toxin by treating a physiologically relevant muscle cell line with purified toxin and monitoring the response using various assays. We observed α-toxin-mediated programmed cellular necrosis that culminated in the release of the immunostimulatory molecule, HMGB1. This mechanism of cell death induction is consistent with the extensive necrosis that is evident in C. septicum-mediated myonecrosis and with the overwhelming sepsis that frequently contributes to the high mortality rate. These results represent an important advance in the understanding of the toxicity of β-barrel pore-forming toxins and how they may contribute to necrotic and systemic disease pathology.
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Affiliation(s)
- Catherine L. Kennedy
- Australian Bacterial Pathogenesis Research Program, Department of Microbiology, Monash University, Clayton, Victoria, Australia
| | - Danielle J. Smith
- Australian Research Council Centre for Excellence in Structural and Functional Microbial Genomics, Department of Microbiology, Monash University, Clayton, Victoria, Australia
- Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria, Australia
| | - Dena Lyras
- Australian Bacterial Pathogenesis Research Program, Department of Microbiology, Monash University, Clayton, Victoria, Australia
| | - Anjana Chakravorty
- Australian Bacterial Pathogenesis Research Program, Department of Microbiology, Monash University, Clayton, Victoria, Australia
| | - Julian I. Rood
- Australian Bacterial Pathogenesis Research Program, Department of Microbiology, Monash University, Clayton, Victoria, Australia
- Australian Research Council Centre for Excellence in Structural and Functional Microbial Genomics, Department of Microbiology, Monash University, Clayton, Victoria, Australia
- * E-mail:
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49
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A transmembrane domain-containing surface protein from Toxoplasma gondii augments replication in activated immune cells and establishment of a chronic infection. Infect Immun 2009; 77:3731-9. [PMID: 19581395 DOI: 10.1128/iai.00450-09] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Toxoplasma gondii mutants identified as defective in the establishment of chronic infection were screened to isolate those specifically impaired in their ability to replicate within activated macrophages. One of the identified mutants contains an insertion in the hypothetical gene TGME49_111670. Genetic complementation restores the ability of the mutant to replicate in immune cells and produce cysts in the brains of mice. While the mutant is more sensitive to nitric oxide than is its parental strain, it is not defective in its ability to suppress nitric oxide. The disrupted protein has no significant homology to proteins with known functions, but is predicted to have one transmembrane domain. Immunofluorescence shows the protein on the parasite surface, even in activated macrophages, colocalizing with a tachyzoite surface antigen, SAG1, and oriented with its C-terminal end external. Western analysis reveals that the protein is downregulated in bradyzoites. Despite the tachyzoite specificity of this protein, mice infected with the mutant succumb to acute infection similarly to those infected with the parent strain. Serum samples from mice with chronic T. gondii infection react to a polypeptide from TGME49_11670, indicating that the protein is seen by the immune system during infection. This study is the first to characterize a T. gondii surface protein that contains a transmembrane domain and show that the protein contributes to parasite replication in activated immune cells and the establishment of chronic infection.
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50
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Wu Q, Guo Z. Glycosylphosphatidylinositols are potential targets for the development of novel inhibitors for aerolysin-type of pore-forming bacterial toxins. Med Res Rev 2009; 30:258-69. [DOI: 10.1002/med.20167] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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