Hyphal induction in the human fungal pathogen Candida albicans reveals a characteristic wall protein profile

The ability of Candida albicans to switch from yeast to hyphal growth is essential for its virulence. The walls and especially the covalently attached wall proteins are involved in the primary host-pathogen interactions. Three hyphal induction methods were compared, based on fetal calf serum, the amino sugar N-acetylglucosamine (GlcNAc) and the mammalian cell culture medium Iscove's modified Dulbecco's medium (IMDM). GlcNAc and IMDM were preferred, allowing stable hyphal growth over a prolonged period without significant reversion to yeast growth and with high biomass yields. We employed Fourier transform-MS combined with a (15)N-metabolically labelled reference culture as internal standard for relative quantification of changes in the wall proteome upon hyphal induction. A total of 21 wall proteins were quantified. Our induction methods triggered a similar response characterized by (i) a category of wall proteins showing strongly increased incorporation levels (Als3, Hwp2, Hyr1, Plb5 and Sod5), (ii) another category with strongly decreased levels (Rhd3, Sod4 and Ywp1) and (iii) a third one enriched for carbohydrate-active enzymes (including Cht2, Crh11, Mp65, Pga4, Phr1, Phr2 and Utr2) and showing only a limited response. This is, to our knowledge, the first systematic, quantitative analysis of the changes in the wall proteome of C. albicans upon hyphal induction. Finally, we propose new wall-protein-derived candidates for vaccine development.