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Updated: Aug 14, 2026
Surface Spreading and Immunostaining of Yeast Chromosomes
Published on: August 9, 2015
Surface localization of the Yps3p protein of Histoplasma capsulatum
1Department of Medical Microbiology and Immunology, University of Wisconsin Medical School, Madison, Wisconsin 53706-1532, USA.
Abstract:
The YPS3 gene of Histoplasma capsulatum encodes a protein that is both resident in the cell wall and also released into the culture medium. This protein is produced only during the pathogenic yeast phase of infection and is also expressed differently in H. capsulatum strains that differ in virulence. We investigated the cellular localization of Yps3p. We demonstrated that the cell wall fraction of Yps3p was surface localized in restriction fragment length polymorphism class 2 strains. We also established that Yps3p released into the G217B culture supernatant binds to the surface of strains that do not naturally express the protein. This binding was saturable and occurred within 5 min of exposure and occurred similarly with live and heat-killed H. capsulatum. Flow cytometric analysis of H. capsulatum after enzymatic treatments was consistent with Yps3p binding to chitin, a carbohydrate polymer that is a component of fungal cell walls. Polysaccharide binding assays demonstrated that chitin but not cellulose binds to and extracts Yps3p from culture supernatants.
Insights
Histoplasma capsulatum
Area of Science:
- Mycology
- Fungal Pathogenesis
- Molecular Biology
Background:
- The YPS3 gene in Histoplasma capsulatum encodes a protein (Yps3p) involved in the pathogenic yeast phase.
- Yps3p is found in the cell wall and released into the culture medium, with expression varying by virulence.
- Understanding Yps3p's localization is crucial for understanding Histoplasma pathogenesis.
Purpose of the Study:
- To investigate the cellular localization of Yps3p in Histoplasma capsulatum.
- To determine the binding characteristics and substrate specificity of secreted Yps3p.
Main Methods:
- Cell wall fractionation and surface localization analysis.
- Binding assays with culture supernatant and H. capsulatum strains.
- Flow cytometry and enzymatic treatments.
- Polysaccharide binding assays.
Main Results:
- Yps3p is surface-localized in the cell wall of certain H. capsulatum strains.
- Secreted Yps3p binds rapidly and saturably to the surface of H. capsulatum strains lacking natural expression.
- Binding is consistent with Yps3p interacting with chitin in the fungal cell wall.
- Yps3p specifically binds chitin, not cellulose.
Conclusions:
- Yps3p exhibits surface localization and can bind to chitin on the H. capsulatum cell wall.
- This chitin-binding property may play a role in Histoplasma capsulatum virulence and cell wall structure.
- Further research into Yps3p's function could reveal new therapeutic targets.
