Taxonomic group: protista / Apicomplexa
(Phylum: Apicomplexa)
Host organism: Felis catus; Gallus gallus
Organ / tissue: the inner layer of the oocyst wallAssociated disease: infection due to Toxoplasma gondii [ICD11:
1F57 
, ICD11:
XN896 ]
The structure was elucidated in this paperNCBI PubMed ID: 23015739Publication DOI: 10.1128/mBio.00258-12Journal NLM ID: 101519231Publisher: Washington, DC: American Society for Microbiology
Correspondence: John Samuelson <jsamuels
bu.edu>
Institutions: Department of Molecular and Cell Biology, Boston University Goldman School of Dental Medicine, Boston, Massachusetts, USA, Department of Biology, Boston College, Chestnut Hill, Massachusetts, USA, Animal Parasitic Diseases Laboratory, Animal Natural Resources Institute, Agricultural Research Service, U.S. Department of Agriculture, Beltsville, MD, USA, Department of Physiology and Biophysics, Boston University School of Medicine, Massachusetts, USA, Mass Spectrometry Resource and Department of Biochemistry, Boston University School of Medicine, Boston, Massachusetts, USA
The walls of infectious pathogens, which are essential for transmission, pathogenesis, and diagnosis, contain sugar polymers that are defining structural features, e.g., β-1,3-glucan and chitin in fungi, chitin in Entamoeba cysts, β-1,3-GalNAc in Giardia cysts, and peptidoglycans in bacteria. The goal here was to determine in which of three walled forms of Toxoplasma gondii (oocyst, sporocyst, or tissue cyst) is β-1,3-glucan, the product of glucan synthases and glucan hydrolases predicted by whole-genome sequences of the parasite. The three most important discoveries were as follows. (i) β-1,3-glucan is present in oocyst walls of Toxoplasma and Eimeria (a chicken parasite that is a model for intestinal stages of Toxoplasma) but is absent from sporocyst and tissue cyst walls. (ii) Fibrils of β-1,3-glucan are part of a trabecular scaffold in the inner layer of the oocyst wall, which also includes a glucan hydrolase that has a novel glucan-binding domain. (iii) Echinocandins, which target the glucan synthase and kill fungi, arrest development of the Eimeria oocyst wall and prevent release of the parasites into the intestinal lumen. In summary, β-1,3-glucan, which can be targeted by drugs, is an important component of oocyst walls of Toxoplasma but is not a component of sporocyst and tissue cyst walls. Importance: We show here that walls of Toxoplasma oocysts, the infectious stage shed by cats, contain β-1,3-glucan, a sugar polymer that is a major component of fungal walls. In contrast to fungi, β-1,3-glucan is part of a trabecular scaffold in the inner layer of the oocyst wall that is independent of the permeability barrier formed by the outer layer of the wall. While glucan synthase inhibitors kill fungi, these inhibitors arrest the development of the oocyst walls of Eimeria (an important chicken pathogen that is a surrogate for Toxoplasma) and block release of oocysts into the intestinal lumen. The absence of β-1,3-glucan in tissue cysts of Toxoplasma suggests that drugs targeted at the glucan synthase might be used to treat Eimeria in chickens but not to treat Toxoplasma in people.
mass spectrometry, parasites, β-1, 3-glucan, Toxoplasma, Toxoplasma gondii, Cyst wall, Eimeria
Structure type: structural motif or average structure
Location inside paper: abstract, p. e00258-12-4
Trivial name: β-1,3-glucan
Compound class: EPS, O-polysaccharide, cell wall polysaccharide, glucan
Contained glycoepitopes: IEDB_1397514,IEDB_142488,IEDB_146664,IEDB_153543,IEDB_158555,IEDB_161166,IEDB_2278476,IEDB_2278477,IEDB_558869,IEDB_857743,IEDB_983931,SB_192
Methods: GC-MS, MALDI-TOF MS, RT-PCR, fluorescence microscopy, TEM
NCBI Taxonomy refs (TaxIDs): 5811,
5802Reference(s) to other database(s): GTC:G51056AN
Show glycosyltransferases
There is only one chemically distinct structure:
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