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Extracellular Toxoplasma gondii tachyzoites metabolize and incorporate unnatural sugars into cellular proteins.

ABSTRACT: Toxoplasma gondii is an obligate intracellular parasite that infects all nucleated cell types in diverse warm-blooded organisms. Many of the surface antigens and effector molecules secreted by the parasite during invasion and intracellular growth are modified by glycans. Glycosylated proteins in the nucleus and cytoplasm have also been reported. Despite their prevalence, the complete inventory and biological significance of glycosylated proteins in Toxoplasma remain unknown. In this study, we aimed to globally profile parasite glycoproteins using a bioorthogonal chemical reporter strategy. This strategy involves the metabolic incorporation of unnatural functional groups (i.e., "chemical reporters") into Toxoplasma glycans, followed by covalent labeling with visual probes or affinity tags. The two-step approach enables the visualization and identification of newly biosynthesized glycoconjugates in the parasite. Using a buffer that mimics intracellular conditions, extracellular Toxoplasma tachyzoites were found to metabolize and incorporate unnatural sugars (equipped with bioorthogonal functional groups) into diverse proteins. Covalent chemistries were used to visualize and retrieve these labeled structures. Subsequent mass spectrometry analysis revealed 89 unique proteins. This survey identified novel proteins as well as previously characterized proteins from lectin affinity analyses.

SUBMITTER: Nazarova LA

PROVIDER: S-EPMC5337115 | biostudies-literature | 2016 Mar

REPOSITORIES: biostudies-literature

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Extracellular Toxoplasma gondii tachyzoites metabolize and incorporate unnatural sugars into cellular proteins.

Nazarova Lidia A LA Ochoa Roxanna J RJ Jones Krysten A KA Morrissette Naomi S NS Prescher Jennifer A JA

Microbes and infection 20151211 3

Toxoplasma gondii is an obligate intracellular parasite that infects all nucleated cell types in diverse warm-blooded organisms. Many of the surface antigens and effector molecules secreted by the parasite during invasion and intracellular growth are modified by glycans. Glycosylated proteins in the nucleus and cytoplasm have also been reported. Despite their prevalence, the complete inventory and biological significance of glycosylated proteins in Toxoplasma remain unknown. In this study, we ai ...[more]

PMID: 26687036

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Project description:Toxoplasma gondii is a globally distributed obligate intracellular parasite which can cause zoonotic toxoplasmosis with great harms. The average death time of mice that infected with Toxoplasma gondii RH strain tachyzoites recovered from the liquid nitrogen was shortened after multiple generations. It has been reported that the parasite is in a state of static virulence during cryopreservation and the virulence of the protozoan parasite can be enhanced after continuous passages in hosts under laboratory conditions. However, no research has been conducted to elucidate its biological mechanism. Herein, we sequenced the T. gondii transcriptome using RNA-Seq technology and performed de novo assembly to investigated the virulence factors expression changes by comparing gene expression profiles between incipiently recovered and completely resuscitated tachyzoites. Transcriptome analysis identified 1,951 differentially expressed transcripts in infected liver, of which 1,752 were significantly downregulated and 199 upregulated. We identified many differentially expressed proteins and genes, including serine/threonine kinase, calnexin, myosin and microtubule-associated protein which have previously been reported to be either involved in cell adhesion, parasite gliding or participate in cell invasion. The great majority of the virulence factors including microneme proteins, rhoptry proteins and dense granule proteins were upregulated in fully recovered tachyzoites. The enhanced virulence of recovered Toxoplasma gondii RH strain from the liquid nitrogen is associated with the up-regulated expression of MICs, ROPs and GRAs. Our data will facilitate future genomic research and in-depth annotation of Toxoplasma gondii RH strain genomes. This study provides a profile of the candidate genes that are suspected to be involved with virulence enhancement of recovered Toxoplasma gondii RH strain tachyzoites. Many further studies should be carried out to confirm the function of the candidate genes. Moreover, the preliminary identification of genes and pathways exhibiting differential expression in complete resuscitation stage may further our general understanding of virulence enhancement in this parasite.

Project description:Toxoplasma gondii is an obligate intracellular parasite which can cause toxoplasmosis. Surface and secreted proteins of T. gondii play important roles in infection and immunity, and also are antigen targets in immunological diagnosis and vaccine development. However, it is difficult to investigate identities and antigenicities of surface and secreted proteins due to limitation of surface protein extraction methods. In this study, a total of 785 potential surface and secreted proteins of T. gondii RH tachyzoites were identified using a method combination of biotin labeling, avidin chromatography isolation, and high flux proteomics (LC-MS/MS). Among the highly-expressed 65 proteins, 43 proteins (66%) were originally annotated as surface or secreted proteins in the released T. gondii genomes, which proved the method combination to be a credible strategy. Furthermore, the transcriptomic responses and cytokine secretions induced by the isolated proteins, the live T. gondii RH tachyzoites infection, and the live pathogenic E. coli infection, in the human peripheral blood monocyte THP-1 cell lines, were comparatively analyzed to reveal antigenicities and immunobiological properties of T. gondii surface and secreted proteins. The transciptomic profiles induced by the isolated proteins were similar to those induced by the live bacterium infection, but were different from those induced by the live parasite infection. Contrary to the low cytokine secretion induced by the live parasite infection, the isolated proteins induced significant cytokine and chemokines secretion. Especially, the secretions of several chemokines induced by the isolated proteins were even higher than those induced by the live bacterium infection. These data suggested that T. gondii surface and secreted proteins were effective antigens, while the live parasite could evade the host innate immunity. This study comprehensively revealed the identities and antigenicities of T. gondii surface and secreted proteins, which laid foundation for further screening new T. gondii antigens, developing immunological diagnosis methods, and studying host immune response to T. gondii infection.

Dataset Information

Extracellular Toxoplasma gondii tachyzoites metabolize and incorporate unnatural sugars into cellular proteins.

Publications

Extracellular Toxoplasma gondii tachyzoites metabolize and incorporate unnatural sugars into cellular proteins.

Similar Datasets

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