Global Secretome Characterization of the Pathogenic Yeast Candida glabrata

Secretory proteins are key modulators of host–pathogen interaction.
The human opportunistic fungal pathogen Candida glabrata lacks secreted proteolytic activity but possesses 11 glycosylphosphatidylinositol-anchored
aspartyl proteases, also referred to as Yapsins (CgYps1–11),
that are essential for its virulence. To delineate the role of CgYapsins
in interaction with host cells, we have profiled, through liquid chromatography-tandem
mass spectrometry (LC-MS/MS) approach, the total secretome of wild-type and Cgyps1-11Δ mutant.
The wild-type secretome consisted of 119 proteins
which were primarily involved in cell wall organization, carbohydrate
metabolism, proteolysis, and translation processes. Of eight CgYapsins
identified in the secretome, the release of two major CgYapsins, CgYps1
and CgYps7, to the medium was confirmed by Western analysis. Further,
comparative analysis revealed 20 common proteins, probably signifying
the core fungal secretome, among C. glabrata, Saccharomyces cerevisiae, and Candida albicans secretomes. Strikingly, the Cgyps1-11Δ secretome was 4.6-fold larger, and contained
65 differentially abundant proteins, as revealed by label-free quantitative
profiling, with 49 and 16 being high- and low-abundant proteins, respectively,
compared to the wild-type secretome. Importantly,
the CgMsb2 mucin, a putative CgYapsins’ substrate, was six-fold
underrepresented in the mutant secretome. Altogether, we demonstrate
for the first time that CgYapsins are both bona fide constituents
and key modulators of the C. glabrata secretome.