Surfaceome of pathogenic yeasts, Candida parapsilosis and Candida tropicalis, revealed with the use of cell surface shaving method and shotgun proteomic approach

In the course of infections caused by pathogenic yeasts from the genus Candida, the fungal cell surface is the first line of contact with the human host. As the surface-exposed proteins are the key players in these interactions, their identification can significantly contribute to discovering the mechanisms of pathogenesis of two emerging pathogens from this genus, C. parapsilosis and C. tropicalis. Therefore, the aim of the present study was to identify the cell wall-attached proteins of these two species with the use of cell surface shaving and a shotgun proteomic approach. Different morphological forms of C. parapsilosis and C. tropicalis cells obtained after growth under various conditions were subjected to this treatment. This allowed to indicate the most abundant cell surface proteins on the basis of the normalized spectral abundance factors. In case of yeast-like forms these were, among others, proteins similar to a chitinase, glyceraldehyde-3-phosphate dehydrogenase and an inducible acid phosphatase for C. parapsilosis, and a constitutive acid phosphatase, pyruvate decarboxylase and glyceraldehyde-3-phosphate dehydrogenase for C. tropicalis. In case of pseudohyphal forms, proteins similar to a cell surface mannoprotein Mp65, chitinase and glycosylphosphatidylinositol-anchored transglycosylase Crh11 were identified at the cell surface of C. parapsilosis. The Rbt1 cell wall protein, a hyphally regulated cell wall protein and proteins from agglutinin-like sequence protein family were found as the most abundant on C. tropicalis pseudohyphae. Apart from the abovementioned proteins, several additional covalently bound and atypical cell wall proteins were also identified. These results extend the current knowledge regarding the molecular basis of virulence of these two non-albicans Candida species.