1
|
Pan M, Ge CC, Fan YM, Jin QW, Shen B, Huang SY. The determinants regulating Toxoplasma gondii bradyzoite development. Front Microbiol 2022; 13:1027073. [PMID: 36439853 PMCID: PMC9691885 DOI: 10.3389/fmicb.2022.1027073] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2022] [Accepted: 10/24/2022] [Indexed: 11/04/2023] Open
Abstract
Toxoplasma gondii is an obligate intracellular zoonotic pathogen capable of infecting almost all cells of warm-blooded vertebrates. In intermediate hosts, this parasite reproduces asexually in two forms, the tachyzoite form during acute infection that proliferates rapidly and the bradyzoite form during chronic infection that grows slowly. Depending on the growth condition, the two forms can interconvert. The conversion of tachyzoites to bradyzoites is critical for T. gondii transmission, and the reactivation of persistent bradyzoites in intermediate hosts may lead to symptomatic toxoplasmosis. However, the mechanisms that control bradyzoite differentiation have not been well studied. Here, we review recent advances in the study of bradyzoite biology and stage conversion, aiming to highlight the determinants associated with bradyzoite development and provide insights to design better strategies for controlling toxoplasmosis.
Collapse
Affiliation(s)
- Ming Pan
- Institute of Comparative Medicine, College of Veterinary Medicine, Yangzhou University, Yangzhou, China
- Jiangsu Key Laboratory of Zoonosis, Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou, China
| | - Ceng-Ceng Ge
- Institute of Comparative Medicine, College of Veterinary Medicine, Yangzhou University, Yangzhou, China
- Jiangsu Key Laboratory of Zoonosis, Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou, China
| | - Yi-Min Fan
- Institute of Comparative Medicine, College of Veterinary Medicine, Yangzhou University, Yangzhou, China
- Jiangsu Key Laboratory of Zoonosis, Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou, China
| | - Qi-Wang Jin
- Institute of Comparative Medicine, College of Veterinary Medicine, Yangzhou University, Yangzhou, China
- Jiangsu Key Laboratory of Zoonosis, Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou, China
| | - Bang Shen
- State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, China
| | - Si-Yang Huang
- Institute of Comparative Medicine, College of Veterinary Medicine, Yangzhou University, Yangzhou, China
- Jiangsu Key Laboratory of Zoonosis, Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou, China
- Joint International Research Laboratory of Agriculture and Agri-Product Safety, The Ministry of Education of China, Yangzhou University, Yangzhou, China
| |
Collapse
|
2
|
Lyons FMT, Gabriela M, Tham WH, Dietrich MH. Plasmodium 6-Cysteine Proteins: Functional Diversity, Transmission-Blocking Antibodies and Structural Scaffolds. Front Cell Infect Microbiol 2022; 12:945924. [PMID: 35899047 PMCID: PMC9309271 DOI: 10.3389/fcimb.2022.945924] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2022] [Accepted: 06/22/2022] [Indexed: 11/30/2022] Open
Abstract
The 6-cysteine protein family is one of the most abundant surface antigens that are expressed throughout the Plasmodium falciparum life cycle. Many members of the 6-cysteine family have critical roles in parasite development across the life cycle in parasite transmission, evasion of the host immune response and host cell invasion. The common feature of the family is the 6-cysteine domain, also referred to as s48/45 domain, which is conserved across Aconoidasida. This review summarizes the current approaches for recombinant expression for 6-cysteine proteins, monoclonal antibodies against 6-cysteine proteins that block transmission and the growing collection of crystal structures that provide insights into the functional domains of this protein family.
Collapse
Affiliation(s)
- Frankie M. T. Lyons
- The Walter and Eliza Hall Institute of Medical Research, Infectious Diseases and Immune Defence Division, Parkville, VIC, Australia
- Department of Medical Biology, The University of Melbourne, Melbourne, VIC, Australia
| | - Mikha Gabriela
- The Walter and Eliza Hall Institute of Medical Research, Infectious Diseases and Immune Defence Division, Parkville, VIC, Australia
- Department of Medical Biology, The University of Melbourne, Melbourne, VIC, Australia
| | - Wai-Hong Tham
- The Walter and Eliza Hall Institute of Medical Research, Infectious Diseases and Immune Defence Division, Parkville, VIC, Australia
- Department of Medical Biology, The University of Melbourne, Melbourne, VIC, Australia
| | - Melanie H. Dietrich
- The Walter and Eliza Hall Institute of Medical Research, Infectious Diseases and Immune Defence Division, Parkville, VIC, Australia
- Department of Medical Biology, The University of Melbourne, Melbourne, VIC, Australia
| |
Collapse
|
3
|
Identification of Toxoplasma gondii adhesins through a machine learning approach. Exp Parasitol 2022; 238:108261. [PMID: 35460696 DOI: 10.1016/j.exppara.2022.108261] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2021] [Revised: 04/10/2022] [Accepted: 04/14/2022] [Indexed: 11/23/2022]
Abstract
Toxoplasma gondii, as other apicomplexa, employs adhesins transmembrane proteins for binding and invasion to host cells. Search and characterization of adhesins is pivotal in understanding Apicomplexa invasion mechanisms and targeting new druggable candidates. This work developed a machine learning software called ApiPredictor UniQE V2.0, based on two approaches: support vector machines and multilayer perceptron, to predict adhesins proteins from amino acid sequences. By using ApiPredictor UniQE V2.0, five SAG-Related Sequences (SRSs) were identified within the Toxoplasma gondii proteome. One of those candidates, TgSRS12B, was cloned in plasmid pEXP5-CT/TOPO and expressed in E. coli BL21 DE3. The resulting recombinant protein was purified via affinity chromatography. Co-precipitation assays in CaCo and Muller cells showed interactions between TgSRS12B-His-tagged and the membrane fractions from both human cell lines. In conclusion, we demonstrated that ApiPredictor UniQE V2.0, a bioinformatic free software, was able to identify TgSRS12B as a new adhesin protein.
Collapse
|
4
|
Dietrich MH, Chan LJ, Adair A, Boulet C, O'Neill MT, Tan LL, Keremane S, Mok YF, Lo AW, Gilson P, Tham WH. Structure of the Pf12 and Pf41 heterodimeric complex of Plasmodium falciparum 6-cysteine proteins. FEMS MICROBES 2022; 3:xtac005. [PMID: 35308105 PMCID: PMC8930183 DOI: 10.1093/femsmc/xtac005] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2021] [Revised: 01/19/2022] [Accepted: 02/10/2022] [Indexed: 11/16/2022] Open
Abstract
During the different stages of the Plasmodium life cycle, surface-associated proteins establish key interactions with the host and play critical roles in parasite survival. The 6-cysteine (6-cys) protein family is one of the most abundant surface antigens and expressed throughout the Plasmodium falciparum life cycle. This protein family is conserved across Plasmodium species and plays critical roles in parasite transmission, evasion of the host immune response and host cell invasion. Several 6-cys proteins are present on the parasite surface as hetero-complexes but it is not known how two 6-cys proteins interact together. Here, we present a crystal structure of Pf12 bound to Pf41 at 2.85 Å resolution, two P. falciparum proteins usually found on the parasite surface of late schizonts and merozoites. Our structure revealed two critical interfaces required for complex formation with important implications on how different 6-cysteine proteins may interact with each other. Using structure-function analyses, we identified important residues for Pf12-Pf41 complex formation. In addition, we generated 16 nanobodies against Pf12 and Pf41 and showed that several Pf12-specific nanobodies inhibit Pf12-Pf41 complex formation. Using X-ray crystallography, we were able to describe the structural mechanism of an inhibitory nanobody in blocking Pf12-Pf41 complex formation. Future studies using these inhibitory nanobodies will be useful to determine the functional role of these two 6-cys proteins in malaria parasites.
Collapse
Affiliation(s)
- Melanie H Dietrich
- The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia
- Department of Medical Biology, The University of Melbourne, Melbourne, Victoria, Australia
| | - Li-Jin Chan
- The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia
- Department of Medical Biology, The University of Melbourne, Melbourne, Victoria, Australia
| | - Amy Adair
- The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia
| | | | - Matthew T O'Neill
- The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia
| | - Li Lynn Tan
- The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia
| | - Sravya Keremane
- The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia
| | - Yee-Foong Mok
- Department of Biochemistry and Molecular Biology and Bio21 Molecular Science and Biotechnology Institute, Melbourne, Australia
| | - Alvin W Lo
- The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia
| | | | - Wai-Hong Tham
- The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia
- Department of Medical Biology, The University of Melbourne, Melbourne, Victoria, Australia
| |
Collapse
|
5
|
Rojas-Pirela M, Medina L, Rojas MV, Liempi AI, Castillo C, Pérez-Pérez E, Guerrero-Muñoz J, Araneda S, Kemmerling U. Congenital Transmission of Apicomplexan Parasites: A Review. Front Microbiol 2021; 12:751648. [PMID: 34659187 PMCID: PMC8519608 DOI: 10.3389/fmicb.2021.751648] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2021] [Accepted: 09/01/2021] [Indexed: 12/17/2022] Open
Abstract
Apicomplexans are a group of pathogenic protists that cause various diseases in humans and animals that cause economic losses worldwide. These unicellular eukaryotes are characterized by having a complex life cycle and the ability to evade the immune system of their host organism. Infections caused by some of these parasites affect millions of pregnant women worldwide, leading to various adverse maternal and fetal/placental effects. Unfortunately, the exact pathogenesis of congenital apicomplexan diseases is far from being understood, including the mechanisms of how they cross the placental barrier. In this review, we highlight important aspects of the diseases caused by species of Plasmodium, Babesia, Toxoplasma, and Neospora, their infection during pregnancy, emphasizing the possible role played by the placenta in the host-pathogen interaction.
Collapse
Affiliation(s)
- Maura Rojas-Pirela
- Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile, Santiago, Chile.,Instituto de Biología, Pontificia Universidad Católica de Valparaíso, Valparaíso, Chile.,Facultad de Farmacia y Bioanálisis, Universidad de Los Andes, Mérida, Venezuela
| | - Lisvaneth Medina
- Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile, Santiago, Chile
| | - Maria Verónica Rojas
- Instituto de Biología, Pontificia Universidad Católica de Valparaíso, Valparaíso, Chile
| | - Ana Isabel Liempi
- Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile, Santiago, Chile
| | - Christian Castillo
- Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile, Santiago, Chile.,Núcleo de Investigación Aplicada en Ciencias Veterinarias y Agronómicas, Facultad de Medicina Veterinaria y Agronomía, Universidad de Las Américas, Santiago, Chile
| | | | - Jesús Guerrero-Muñoz
- Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile, Santiago, Chile
| | - Sebastian Araneda
- Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile, Santiago, Chile.,Facultad de Salud y Odontología, Universidad Diego Portales, Santiago, Chile
| | - Ulrike Kemmerling
- Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile, Santiago, Chile
| |
Collapse
|
6
|
Nanobody generation and structural characterization of Plasmodium falciparum 6-cysteine protein Pf12p. Biochem J 2021; 478:579-595. [PMID: 33480416 PMCID: PMC7886318 DOI: 10.1042/bcj20200415] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2020] [Revised: 01/20/2021] [Accepted: 01/22/2021] [Indexed: 01/09/2023]
Abstract
Surface-associated proteins play critical roles in the Plasmodium parasite life cycle and are major targets for vaccine development. The 6-cysteine (6-cys) protein family is expressed in a stage-specific manner throughout Plasmodium falciparum life cycle and characterized by the presence of 6-cys domains, which are β-sandwich domains with conserved sets of disulfide bonds. Although several 6-cys family members have been implicated to play a role in sexual stages, mosquito transmission, evasion of the host immune response and host cell invasion, the precise function of many family members is still unknown and structural information is only available for four 6-cys proteins. Here, we present to the best of our knowledge, the first crystal structure of the 6-cys protein Pf12p determined at 2.8 Å resolution. The monomeric molecule folds into two domains, D1 and D2, both of which adopt the canonical 6-cys domain fold. Although the structural fold is similar to that of Pf12, its paralog in P. falciparum, we show that Pf12p does not complex with Pf41, which is a known interaction partner of Pf12. We generated 10 distinct Pf12p-specific nanobodies which map into two separate epitope groups; one group which binds within the D2 domain, while several members of the second group bind at the interface of the D1 and D2 domain of Pf12p. Characterization of the structural features of the 6-cys family and their associated nanobodies provide a framework for generating new tools to study the diverse functions of the 6-cys protein family in the Plasmodium life cycle.
Collapse
|
7
|
The structure of a major surface antigen SAG19 from Eimeria tenella unifies the Eimeria SAG family. Commun Biol 2021; 4:376. [PMID: 33742128 PMCID: PMC7979774 DOI: 10.1038/s42003-021-01904-w] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2020] [Accepted: 02/19/2021] [Indexed: 01/31/2023] Open
Abstract
In infections by apicomplexan parasites including Plasmodium, Toxoplasma gondii, and Eimeria, host interactions are mediated by proteins including families of membrane-anchored cysteine-rich surface antigens (SAGs) and SAG-related sequences (SRS). Eimeria tenella causes caecal coccidiosis in chickens and has a SAG family with over 80 members making up 1% of the proteome. We have solved the structure of a representative E. tenella SAG, EtSAG19, revealing that, despite a low level of sequence similarity, the entire Eimeria SAG family is unified by its three-layer αβα fold which is related to that of the CAP superfamily. Furthermore, sequence comparisons show that the Eimeria SAG fold is conserved in surface antigens of the human coccidial parasite Cyclospora cayetanensis but this fold is unrelated to that of the SAGs/SRS proteins expressed in other apicomplexans including Plasmodium species and the cyst-forming coccidia Toxoplasma gondii, Neospora caninum and Besnoitia besnoiti. However, despite having very different structures, Consurf analysis showed that Eimeria SAG and Toxoplasma SRS families each exhibit marked hotspots of sequence hypervariability that map to their surfaces distal to the membrane anchor. This suggests that the primary and convergent purpose of the different structures is to provide a platform onto which sequence variability can be imposed.
Collapse
|
8
|
Cruz-Mirón R, Ramírez-Flores CJ, Lagunas-Cortés N, Mondragón-Castelán M, Ríos-Castro E, González-Pozos S, Aguirre-García MM, Mondragón-Flores R. Proteomic characterization of the pellicle of Toxoplasma gondii. J Proteomics 2021; 237:104146. [PMID: 33588107 DOI: 10.1016/j.jprot.2021.104146] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2020] [Revised: 01/15/2021] [Accepted: 02/02/2021] [Indexed: 01/09/2023]
Abstract
Toxoplasma gondii is one of the most successful intracellular parasites in the world. The dynamic, adhesion, invasion, and even replication capabilities of Toxoplasma are based on dynamic machinery located in the pellicle, a three membrane complex that surrounds the parasite. Among the proteins that carry out these processes are inner membrane complex (IMC) proteins, gliding-associated proteins (GAP), diverse myosins, actin, tubulin, and SRS proteins. Despite the importance of the pellicle, the knowledge of its composition is limited. Broad protein identification from an enriched pellicle fraction was obtained by independent digestion with trypsin and chymotrypsin and quantified by mass spectrometry. By trypsin digestion, 548 proteins were identified, while by chymotrypsin digestion, additional 22 proteins were identified. Besides, a group of "sequences related to SAG1" proteins (SRS) were detected together with unidentified new proteins. From identified SRS proteins, SRS51 was chosen for analysis and modeling as its similarities with crystallized adhesion proteins, exhibiting the presence of a spatial groove that is apparently involved in adhesion and cell invasion. As SRS proteins have been reported to be involved in the activation of the host's immune response, further studies could consider them as targets in the design of vaccines or of drugs against Toxoplasma. SIGNIFICANCE: To date, the proteomic composition of the pellicle of Toxoplasma is unknown. Most proteins reported in Toxoplasma pellicle have been poorly studied, and many others remain unidentified. Herein, a group of new SRS proteins is described. Some SRS proteins previously described from pellicle fraction have adhesion properties to the host cell membrane, so their study would provide data related to invasion mechanism and to open possibilities for considering them as targets in the design of immunoprotective strategies or the design of new pharmacological treatments.
Collapse
Affiliation(s)
- Rosalba Cruz-Mirón
- Departamento de Bioquímica, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional (CINVESTAV-IPN), Av. IPN No. 2508, Ciudad de México C.P. 07360, Mexico
| | - Carlos J Ramírez-Flores
- Departamento de Bioquímica, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional (CINVESTAV-IPN), Av. IPN No. 2508, Ciudad de México C.P. 07360, Mexico; Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Noé Lagunas-Cortés
- Departamento de Bioquímica, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional (CINVESTAV-IPN), Av. IPN No. 2508, Ciudad de México C.P. 07360, Mexico
| | - Mónica Mondragón-Castelán
- Departamento de Bioquímica, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional (CINVESTAV-IPN), Av. IPN No. 2508, Ciudad de México C.P. 07360, Mexico
| | | | | | - M Magdalena Aguirre-García
- Unidad de Investigación UNAM-INC, División de Investigación, Facultad de Medicina, Instituto Nacional de Cardiología Ignacio Chávez, Ciudad de México, Mexico
| | - Ricardo Mondragón-Flores
- Departamento de Bioquímica, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional (CINVESTAV-IPN), Av. IPN No. 2508, Ciudad de México C.P. 07360, Mexico.
| |
Collapse
|
9
|
Tu V, Yakubu R, Weiss LM. Observations on bradyzoite biology. Microbes Infect 2018; 20:466-476. [PMID: 29287987 PMCID: PMC6019562 DOI: 10.1016/j.micinf.2017.12.003] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2017] [Revised: 12/13/2017] [Accepted: 12/15/2017] [Indexed: 02/06/2023]
Abstract
Tachyzoites of the Apicomplexan Toxoplasma gondii cause acute infection, disseminate widely in their host, and eventually differentiate into a latent encysted form called bradyzoites that are found within tissue cysts. During latent infection, whenever transformation to tachyzoites occurs, any tachyzoites that develop are removed by the immune system. In contrast, cysts containing bradyzoites are sequestered from the immune system. In the absence of an effective immune response released organisms that differentiate into tachyzoites cause acute infection. Tissue cysts, therefore, serve as a reservoir for the reactivation of toxoplasmosis when the host becomes immunocompromised by conditions such as HIV infection, organ transplantation, or due to the impaired immune response that occurs when pathogens are acquired in utero. While tachyzoites and bradyzoites are well defined morphologically, there is no clear consensus on how interconversion occurs or what exact signal(s) mediate this transformation. Advances in research methods have facilitated studies on T. gondii bradyzoites providing important new insights into the biology of latent infection.
Collapse
Affiliation(s)
- Vincent Tu
- Department of Pathology, Albert Einstein College of Medicine, Bronx, NY 10461, USA
| | - Rama Yakubu
- Department of Pathology, Albert Einstein College of Medicine, Bronx, NY 10461, USA
| | - Louis M Weiss
- Department of Pathology, Albert Einstein College of Medicine, Bronx, NY 10461, USA; Department of Medicine, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
| |
Collapse
|
10
|
Bezerra MA, Pereira LM, Bononi A, Biella CA, Baroni L, Pollo-Oliveira L, Yatsuda AP. Constitutive expression and characterization of a surface SRS (NcSRS67) protein of Neospora caninum with no orthologue in Toxoplasma gondii. Parasitol Int 2017; 66:173-180. [PMID: 28108401 DOI: 10.1016/j.parint.2017.01.010] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2016] [Revised: 12/22/2016] [Accepted: 01/17/2017] [Indexed: 02/06/2023]
Abstract
Neospora caninum is a parasite of the Apicomplexa phylum responsible for abortion and losses of fertility in cattle. As part of its intracellular cycle, the first interaction of the parasite with the target cell is performed with the surface proteins known as the SRS superfamily (Surface Antigen Glycoprotein - Related Sequences). SAG related or SRS proteins have been a target of intense research due to its immunodominant pattern, exhibiting potential as diagnostic and/or vaccine candidates. The aim of this study was the cloning, expression and characterization of the gene NcSRS67 of N. caninum using a novel designed plasmid. The coding sequence of NcSRS67 (without the signal peptide and the GPI anchor) was cloned and expressed constitutively instead of the ccdB system of pCR-Blunt II-TOPO. The protein was purified in a nickel sepharose column and identified by mass spectrometry (MS/MS). The constitutive expression did not affect the final bacterial growth, with a similar OD 600nm compared to the non-transformed strains. The recombinant NcSRS67 was over expressed and the native form was detected by the anti-rNcSRS67 serum on 1D western blot as a single band of approximately 38kDa as predicted. On an in vitro assay, the inhibitory effect of the polyclonal antiserum anti-rNcSRS67 was nearly 20% on adhesion/invasion of host cells. The NcSRS67 native protein was localised on part of the surface of N. caninum tachyzoite when compared to the nucleus by confocal immunofluorescence.
Collapse
Affiliation(s)
- Marcos Alexandre Bezerra
- Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, Av do café, s/n, 14040-903 Ribeirão Preto, SP, Brazil
| | - Luiz Miguel Pereira
- Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, Av do café, s/n, 14040-903 Ribeirão Preto, SP, Brazil
| | - Aline Bononi
- Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, Av do café, s/n, 14040-903 Ribeirão Preto, SP, Brazil
| | - Carla Agostino Biella
- Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, Av do café, s/n, 14040-903 Ribeirão Preto, SP, Brazil
| | - Luciana Baroni
- Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, Av do café, s/n, 14040-903 Ribeirão Preto, SP, Brazil
| | - Leticia Pollo-Oliveira
- Núcleo de Apoio à Pesquisa em Produtos Naturais e Sintéticos, Universidade de São Paulo, Ribeirão Preto, SP, Brazil
| | - Ana Patrícia Yatsuda
- Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, Av do café, s/n, 14040-903 Ribeirão Preto, SP, Brazil; Núcleo de Apoio à Pesquisa em Produtos Naturais e Sintéticos, Universidade de São Paulo, Ribeirão Preto, SP, Brazil.
| |
Collapse
|
11
|
The Structure of Treponema pallidum Tp0624 Reveals a Modular Assembly of Divergently Functionalized and Previously Uncharacterized Domains. PLoS One 2016; 11:e0166274. [PMID: 27832149 PMCID: PMC5104382 DOI: 10.1371/journal.pone.0166274] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2016] [Accepted: 10/25/2016] [Indexed: 02/03/2023] Open
Abstract
Treponema pallidum subspecies pallidum is the causative agent of syphilis, a chronic, multistage, systemic infection that remains a major global health concern. The molecular mechanisms underlying T. pallidum pathogenesis are incompletely understood, partially due to the phylogenetic divergence of T. pallidum. One aspect of T. pallidum that differentiates it from conventional Gram-negative bacteria, and is believed to play an important role in pathogenesis, is its unusual cell envelope ultrastructure; in particular, the T. pallidum peptidoglycan layer is chemically distinct, thinner and more distal to the outer membrane. Established functional roles for peptidoglycan include contributing to the structural integrity of the cell envelope and stabilization of the flagellar motor complex, which are typically mediated by the OmpA domain-containing family of proteins. To gain insight into the molecular mechanisms that govern peptidoglycan binding and cell envelope biogenesis in T. pallidum we report here the structural characterization of the putative OmpA-like domain-containing protein, Tp0624. Analysis of the 1.70 Å resolution Tp0624 crystal structure reveals a multi-modular architecture comprised of three distinct domains including a C-terminal divergent OmpA-like domain, which we show is unable to bind the conventional peptidoglycan component diaminopimelic acid, and a previously uncharacterized tandem domain unit. Intriguingly, bioinformatic analysis indicates that the three domains together are found in all orthologs from pathogenic treponemes, but are not observed together in genera outside Treponema. These findings provide the first structural insight into a multi-modular treponemal protein containing an OmpA-like domain and its potential role in peptidoglycan coordination and stabilization of the T. pallidum cell envelope.
Collapse
|
12
|
Parker ML, Peng F, Boulanger MJ. The Structure of Plasmodium falciparum Blood-Stage 6-Cys Protein Pf41 Reveals an Unexpected Intra-Domain Insertion Required for Pf12 Coordination. PLoS One 2015; 10:e0139407. [PMID: 26414347 PMCID: PMC4587554 DOI: 10.1371/journal.pone.0139407] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2015] [Accepted: 09/11/2015] [Indexed: 01/27/2023] Open
Abstract
Plasmodium falciparum is an apicomplexan parasite and the etiological agent of severe human malaria. The complex P. falciparum life cycle is supported by a diverse repertoire of surface proteins including the family of 6-Cys s48/45 antigens. Of these, Pf41 is localized to the surface of the blood-stage merozoite through its interaction with the glycophosphatidylinositol-anchored Pf12. Our recent structural characterization of Pf12 revealed two juxtaposed 6-Cys domains (D1 and D2). Pf41, however, contains an additional segment of 120 residues predicted to form a large spacer separating its two 6-Cys domains. To gain insight into the assembly mechanism and overall architecture of the Pf12-Pf41 complex, we first determined the 2.45 Å resolution crystal structure of Pf41 using zinc single-wavelength anomalous dispersion. Structural analysis revealed an unexpected domain organization where the Pf41 6-Cys domains are, in fact, intimately associated and the additional residues instead map predominately to an inserted domain-like region (ID) located between two β-strands in D1. Notably, the ID is largely proteolyzed in the final structure suggesting inherent flexibility. To assess the contribution of the ID to complex formation, we engineered a form of Pf41 where the ID was replaced by a short glycine-serine linker and showed by isothermal titration calorimetry that binding to Pf12 was abrogated. Finally, protease protection assays showed that the proteolytic susceptibility of the ID was significantly reduced in the complex, consistent with the Pf41 ID directly engaging Pf12. Collectively, these data establish the architectural organization of Pf41 and define an essential role for the Pf41 ID in promoting assembly of the Pf12-Pf41 heterodimeric complex.
Collapse
Affiliation(s)
- Michelle L. Parker
- Department of Biochemistry & Microbiology, University of Victoria, Victoria, British Columbia, Canada
| | - Fangni Peng
- Department of Biochemistry & Microbiology, University of Victoria, Victoria, British Columbia, Canada
| | - Martin J. Boulanger
- Department of Biochemistry & Microbiology, University of Victoria, Victoria, British Columbia, Canada
- * E-mail:
| |
Collapse
|
13
|
Paing MM, Tolia NH. Multimeric assembly of host-pathogen adhesion complexes involved in apicomplexan invasion. PLoS Pathog 2014; 10:e1004120. [PMID: 24945143 PMCID: PMC4055764 DOI: 10.1371/journal.ppat.1004120] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Affiliation(s)
- May M. Paing
- Department of Molecular Microbiology and Microbial Pathogenesis, Washington University School of Medicine, Saint Louis, Missouri, United States of America
| | - Niraj H. Tolia
- Department of Molecular Microbiology and Microbial Pathogenesis, Washington University School of Medicine, Saint Louis, Missouri, United States of America
- * E-mail:
| |
Collapse
|
14
|
Ramly NZ, Rouzheinikov SN, Sedelnikova SE, Baker PJ, Chow YP, Wan KL, Nathan S, Rice DW. Crystallization and preliminary crystallographic analysis of a surface antigen glycoprotein, SAG19, from Eimeria tenella. Acta Crystallogr Sect F Struct Biol Cryst Commun 2013; 69:1380-3. [PMID: 24316835 DOI: 10.1107/s1744309113029734] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2013] [Accepted: 10/29/2013] [Indexed: 01/17/2023]
Abstract
Coccidiosis in chickens is caused by the apicomplexan parasite Eimeria tenella and is thought to involve a role for a superfamily of more than 20 cysteine-rich surface antigen glycoproteins (SAGs) in host-parasite interactions. A representative member of the family, SAG19, has been overexpressed in Escherichia coli, purified and crystallized by the hanging-drop method of vapour diffusion using ammonium sulfate as the precipitant. Crystals of SAG19 diffracted to beyond 1.50 Å resolution and belonged to space group I4, with unit-cell parameters a = b = 108.2, c = 37.5 Å. Calculation of possible values of VM suggests that there is a single molecule in the asymmetric unit.
Collapse
Affiliation(s)
- Nur Zazarina Ramly
- Krebs Institute for Biomolecular Research, Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield S10 2TN, England
| | | | | | | | | | | | | | | |
Collapse
|
15
|
Zhang M, Zhao L, Song J, Li Y, Zhao Q, He S, Cong H. DNA vaccine encoding the Toxoplasma gondii bradyzoite-specific surface antigens SAG2CDX protect BALB/c mice against type II parasite infection. Vaccine 2013; 31:4536-40. [PMID: 23933373 DOI: 10.1016/j.vaccine.2013.07.065] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2013] [Revised: 07/21/2013] [Accepted: 07/25/2013] [Indexed: 02/07/2023]
Abstract
The surface antigens SAG2C, SAG2D, and SAG2X, which expressed specifically on bradyzoite stage of Toxoplasma gondii, have been demonstrated to be important for persistence of cyst in the brain. In this study, DNA vaccines expressing SAG2C, SAG2D, and SAG2X of T. gondii were constructed and their protective efficacy were evaluated in BALB/c mice. Mice vaccinated with pVAX1-SAG2C (pSAG2C), pVAX1-2D (pSAG2D) or pVAX1-2X (pSAG2C) showed higher levels of serum IgG antibodies and lymphocyte proliferation response compared to PBS and pVAX1 treated mice (p<0.05). The immune response was characterized by a strong Th1 response and increased cytokine production of IL-2 and IFN-γ. Vaccinated mice displayed significant protection against the challenge with the cyst of T. gondii genotype II strain of PRU (cyst-forming in mouse). A significant reduction in the brain cyst burden was detected in the mice immunized with pSAG2C (72%), pSAG2D (23%), pSAG2X (69%) alone and even more reduction rate, 77%, was achieved in the combination group compared to PBS treated mice. The results implied that immunization with DNA vaccines expressing SAG2C, SAG2D, and SAG2X, and, in particular, a combination of all three DNA plasmids, could effectively protect the mice against T. gondii chronic infection.
Collapse
Affiliation(s)
- Min Zhang
- Department of Human Parasitology, Shandong University School of Medicine, No. 44 Wenhuaxi Road, Jinan, Shandong 250012, PR China
| | | | | | | | | | | | | |
Collapse
|
16
|
Macêdo AG, Cunha JP, Cardoso THS, Silva MV, Santiago FM, Silva JS, Pirovani CP, Silva DAO, Mineo JR, Mineo TWP. SAG2A protein from Toxoplasma gondii interacts with both innate and adaptive immune compartments of infected hosts. Parasit Vectors 2013; 6:163. [PMID: 23735002 PMCID: PMC3706231 DOI: 10.1186/1756-3305-6-163] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2013] [Accepted: 05/26/2013] [Indexed: 11/26/2022] Open
Abstract
Background Toxoplasma gondii is an intracellular parasite that causes relevant clinical disease in humans and animals. Several studies have been performed in order to understand the interactions between proteins of the parasite and host cells. SAG2A is a 22 kDa protein that is mainly found in the surface of tachyzoites. In the present work, our aim was to correlate the predicted three-dimensional structure of this protein with the immune system of infected hosts. Methods To accomplish our goals, we performed in silico analysis of the amino acid sequence of SAG2A, correlating the predictions with in vitro stimulation of antigen presenting cells and serological assays. Results Structure modeling predicts that SAG2A protein possesses an unfolded C-terminal end, which varies its conformation within distinct strain types of T. gondii. This structure within the protein shelters a known B-cell immunodominant epitope, which presents low identity with its closest phyllogenetically related protein, an orthologue predicted in Neospora caninum. In agreement with the in silico observations, sera of known T. gondii infected mice and goats recognized recombinant SAG2A, whereas no serological cross-reactivity was observed with samples from N. caninum animals. Additionally, the C-terminal end of the protein was able to down-modulate pro-inflammatory responses of activated macrophages and dendritic cells. Conclusions Altogether, we demonstrate herein that recombinant SAG2A protein from T. gondii is immunologically relevant in the host-parasite interface and may be targeted in therapeutic and diagnostic procedures designed against the infection.
Collapse
Affiliation(s)
- Arlindo G Macêdo
- Laboratório de Imunoparasitologia "Dr, Mário Endsfeldz Camargo", Instituto de Ciências Biomédicas, Universidade Federal de Uberlândia, Av, Pará 1720-Bloco 4C, Campus Umuarama, Uberlândia, Minas Gerais 38.400-902, Brazil
| | | | | | | | | | | | | | | | | | | |
Collapse
|
17
|
Tonkin ML, Arredondo SA, Loveless BC, Serpa JJ, Makepeace KA, Sundar N, Petrotchenko EV, Miller LH, Grigg ME, Boulanger MJ. Structural and Biochemical Characterization of Plasmodium falciparum 12 (Pf12) Reveals a Unique Interdomain Organization and the Potential for an Antiparallel Arrangement with Pf41. J Biol Chem 2013; 288:12805-17. [DOI: 10.1074/jbc.m113.455667] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
|
18
|
Analysis of structures and epitopes of surface antigen glycoproteins expressed in bradyzoites of Toxoplasma gondii. BIOMED RESEARCH INTERNATIONAL 2013; 2013:165342. [PMID: 23586017 PMCID: PMC3618923 DOI: 10.1155/2013/165342] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/14/2012] [Accepted: 02/18/2013] [Indexed: 11/17/2022]
Abstract
Toxoplasma gondii is a protozoan parasite capable of infecting humans and animals. Surface antigen glycoproteins, SAG2C, -2D, -2X, and -2Y, are expressed on the surface of bradyzoites. These antigens have been shown to protect bradyzoites against immune responses during chronic infections. We studied structures of SAG2C, -2D, -2X, and -2Y proteins using bioinformatics methods. The protein sequence alignment was performed by T-Coffee method. Secondary structural and functional domains were predicted using software PSIPRED v3.0 and SMART software, and 3D models of proteins were constructed and compared using the I-TASSER server, VMD, and SWISS-spdbv. Our results showed that SAG2C, -2D, -2X, and -2Y are highly homologous proteins. They share the same conserved peptides and HLA-I restricted epitopes. The similarity in structure and domains indicated putative common functions that might stimulate similar immune response in hosts. The conserved peptides and HLA-restricted epitopes could provide important insights on vaccine study and the diagnosis of this disease.
Collapse
|
19
|
Abstract
INTRODUCTION Toxoplasma gondii, the agent that causes toxoplasmosis, is an opportunistic parasite that infects many mammalian species. It is an obligate intracellular parasite that causes severe congenital neurological and ocular disease mostly in immunocompromised humans. The current regimen of therapy includes only a few medications that often lead to hypersensitivity and toxicity. In addition, there are no vaccines available to prevent the transmission of this agent. Therefore, safer and more effective medicines to treat toxoplasmosis are urgently needed. AREAS COVERED The author presents in silico and in vitro strategies that are currently used to screen for novel targets and unique chemotypes against T. gondii. Furthermore, this review highlights the screening technologies and characterization of some novel targets and new chemical entities that could be developed into highly efficacious treatments for toxoplasmosis. EXPERT OPINION A number of diverse methods are being used to design inhibitors against T. gondii. These include ligand-based methods, in which drugs that have been shown to be efficacious against other Apicomplexa parasites can be repurposed to identify lead molecules against T. gondii. In addition, structure-based methods use currently available repertoire of structural information in various databases to rationally design small-molecule inhibitors of T. gondii. Whereas the screening methods have their advantages and limitations, a combination of methods is ideally suited to design small-molecule inhibitors of complex parasites such as T. gondii.
Collapse
Affiliation(s)
- Sandhya Kortagere
- Drexel University College of Medicine, Institute for Molecular Medicine, Department of Microbiology and Immunology, 2900, Queen Lane, PA 19129, USA.
| |
Collapse
|
20
|
Taechalertpaisarn T, Crosnier C, Bartholdson SJ, Hodder AN, Thompson J, Bustamante LY, Wilson DW, Sanders PR, Wright GJ, Rayner JC, Cowman AF, Gilson PR, Crabb BS. Biochemical and functional analysis of two Plasmodium falciparum blood-stage 6-cys proteins: P12 and P41. PLoS One 2012; 7:e41937. [PMID: 22848665 PMCID: PMC3407074 DOI: 10.1371/journal.pone.0041937] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2012] [Accepted: 06/26/2012] [Indexed: 11/19/2022] Open
Abstract
The genomes of Plasmodium parasites that cause malaria in humans, other primates, birds, and rodents all encode multiple 6-cys proteins. Distinct 6-cys protein family members reside on the surface at each extracellular life cycle stage and those on the surface of liver infective and sexual stages have been shown to play important roles in hepatocyte growth and fertilization respectively. However, 6-cys proteins associated with the blood-stage forms of the parasite have no known function. Here we investigate the biochemical nature and function of two blood-stage 6-cys proteins in Plasmodium falciparum, the most pathogenic species to afflict humans. We show that native P12 and P41 form a stable heterodimer on the infective merozoite surface and are secreted following invasion, but could find no evidence that this complex mediates erythrocyte-receptor binding. That P12 and P41 do not appear to have a major role as adhesins to erythrocyte receptors was supported by the observation that antisera to these proteins did not substantially inhibit erythrocyte invasion. To investigate other functional roles for these proteins their genes were successfully disrupted in P. falciparum, however P12 and P41 knockout parasites grew at normal rates in vitro and displayed no other obvious phenotypic changes. It now appears likely that these blood-stage 6-cys proteins operate as a pair and play redundant roles either in erythrocyte invasion or in host-immune interactions.
Collapse
Affiliation(s)
- Tana Taechalertpaisarn
- Burnet Institute, Melbourne, Victoria, Australia
- Department of Medical Biology, The University of Melbourne, Victoria, Australia
| | - Cecile Crosnier
- Cell Surface Signalling Laboratory, Wellcome Trust Sanger Institute, Cambridge, United Kingdom
| | - S. Josefin Bartholdson
- Cell Surface Signalling Laboratory, Wellcome Trust Sanger Institute, Cambridge, United Kingdom
| | - Anthony N. Hodder
- The Walter & Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia
| | - Jenny Thompson
- The Walter & Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia
| | - Leyla Y. Bustamante
- Malaria Programme, Wellcome Trust Sanger Institute, Cambridge, United Kingdom
| | - Danny W. Wilson
- The Walter & Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia
| | | | - Gavin J. Wright
- Cell Surface Signalling Laboratory, Wellcome Trust Sanger Institute, Cambridge, United Kingdom
| | - Julian C. Rayner
- Malaria Programme, Wellcome Trust Sanger Institute, Cambridge, United Kingdom
| | - Alan F. Cowman
- Department of Medical Biology, The University of Melbourne, Victoria, Australia
- The Walter & Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia
| | - Paul R. Gilson
- Burnet Institute, Melbourne, Victoria, Australia
- Departments of Immunology and Medicine, Monash University, Victoria, Australia
| | - Brendan S. Crabb
- Burnet Institute, Melbourne, Victoria, Australia
- Departments of Immunology and Medicine, Monash University, Victoria, Australia
- Department of Microbiology and Immunology, The University of Melbourne, Victoria, Australia
- * E-mail:
| |
Collapse
|
21
|
Arredondo SA, Cai M, Takayama Y, MacDonald NJ, Anderson DE, Aravind L, Clore GM, Miller LH. Structure of the Plasmodium 6-cysteine s48/45 domain. Proc Natl Acad Sci U S A 2012; 109:6692-7. [PMID: 22493233 PMCID: PMC3340019 DOI: 10.1073/pnas.1204363109] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The s48/45 domain was first noted in Plasmodium proteins more than 15 y ago. Previously believed to be unique to Plasmodium, the s48/45 domain is present in other aconoidasidans. In Plasmodium, members of the s48/45 family of proteins are localized on the surface of the parasite in different stages, mostly by glycosylphosphatydylinositol-anchoring. Members such as P52 and P36 seem to play a role in invasion of hepatocytes, and Pfs230 and Pfs48/45 are involved in fertilization in the sexual stages and have been consistently studied as targets of transmission-blocking vaccines for years. In this report, we present the molecular structure for the s48/45 domain corresponding to the C-terminal domain of the blood-stage protein Pf12 from Plasmodium falciparum, obtained by NMR. Our results indicate that this domain is a β-sandwich formed by two sheets with a mixture of parallel and antiparallel strands. Of the six conserved cysteines, two pairs link the β-sheets by two disulfide bonds, and the third pair forms a bond outside the core. The structure of the s48/45 domain conforms well to the previously defined surface antigen 1 (SAG1)-related-sequence (SRS) fold observed in the SAG family of surface antigens found in Toxoplasma gondii. Despite extreme sequence divergence, remarkable spatial conservation of one of the disulfide bonds is observed, supporting the hypothesis that the domains have evolved from a common ancestor. Furthermore, a homologous domain is present in ephrins, raising the possibility that the precursor of the s48/45 and SRS domains emerged from an ancient transfer to Apicomplexa from metazoan hosts.
Collapse
Affiliation(s)
| | | | | | | | - D. Eric Anderson
- Mass Spectrometry Facility, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892; and
| | - L. Aravind
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, MD 20894
| | | | - Louis H. Miller
- Laboratory of Malaria Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, MD 20852
| |
Collapse
|
22
|
Boulanger MJ, Tonkin ML, Crawford J. Apicomplexan parasite adhesins: novel strategies for targeting host cell carbohydrates. Curr Opin Struct Biol 2010; 20:551-9. [DOI: 10.1016/j.sbi.2010.08.003] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2010] [Revised: 07/27/2010] [Accepted: 08/12/2010] [Indexed: 11/25/2022]
|
23
|
Crawford J, Lamb E, Wasmuth J, Grujic O, Grigg ME, Boulanger MJ. Structural and functional characterization of SporoSAG: a SAG2-related surface antigen from Toxoplasma gondii. J Biol Chem 2010; 285:12063-70. [PMID: 20164173 DOI: 10.1074/jbc.m109.054866] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Toxoplasma gondii, the etiological agent of toxoplasmosis, utilizes stage-specific expression of antigenically distinct glycosylphosphatidylinositol-tethered surface coat proteins to promote and establish chronic infection. Of the three infective stages of T. gondii, sporozoites are encapsulated in highly infectious oocysts that have been linked to large scale outbreaks of toxoplasmosis. SporoSAG (surface antigen glycoprotein) is the dominant surface coat protein expressed on the surface of sporozoites. Using a bioinformatic approach, we show that SporoSAG clusters with the SAG2 subfamily of the SAG1-related superfamily (SRS) and is non-polymorphic among the 11 haplogroups of T. gondii strains. In contrast to the immunodominant SAG1 protein expressed on tachyzoites, SporoSAG is non-immunogenic during natural infection. We report the 1.60 A resolution crystal structure of SporoSAG solved using cadmium single anomalous dispersion. SporoSAG crystallized as a monomer and displays unique features of the SRS beta-sandwich fold relative to SAG1 and BSR4. Intriguingly, the structural diversity is localized to the upper sheets of the beta-sandwich fold and may have important implications for multimerization and host cell ligand recognition. The structure of SporoSAG also reveals an unexpectedly acidic surface that contrasts with the previously determined SAG1 and BSR4 structures where a basic surface is predicted to play a role in binding negatively charged glycosaminoglycans. Our structural and functional characterization of SporoSAG provides a rationale for the evolutionary divergence of this key SRS family member.
Collapse
Affiliation(s)
- Joanna Crawford
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, British Columbia V8W 3P6, Canada
| | | | | | | | | | | |
Collapse
|