Candida albicans cell shaving uncovers new proteins involved in cell wall integrity, yeast to hypha transition, stress response and host–pathogen interaction

• Two-fold more proteins were identified in hyphae (928) than in yeast (438).
• A higher number of GPI and cell wall proteins were detected on the hyphae surface.
• A phenotypic study of 17 mutants in uncharacterized surface proteins was performed.
• Ali1, Mci4 and 2 Orfs are relevant in stress resistance and dimorphic transition.
• Pst3, Tos1 and 2 Orfs are related to cell wall and host–cell interaction.

The ability to switch from yeast to hyphal growth is essential for virulence in Candida albicans. The cell surface is the initial point of contact between the fungus and the host. In this work, a free-gel proteomic strategy based on tryptic digestion of live yeast and hyphae cells and protein identification using LC–MS/MS methodology was used to identify cell surface proteins. Using this strategy, a total of 943 proteins were identified, of which 438 were in yeast and 928 were in hyphae. Of these proteins, 79 were closely related to the organization and biogenesis of the cell wall, including 28 GPI-anchored proteins, such as Hyr1 and Sod5 which were detected exclusively in hyphae, and Als2 and Sap10which were detected only in yeast. A group of 17 proteins of unknown function were subsequently studied by analysis of the corresponding deletion mutants. We found that four new proteins, Pst3, Tos1, Orf19.3060 and Orf19.5352 are involved in cell wall integrity and in C. albicans' engulfment by macrophages. Moreover, the putative NADH-ubiquinone-related proteins, Ali1, Mci4, Orf19.287 and Orf19.7590, are also involved in osmotic and oxidative resistance, yeast to hypha transition and the ability to damage and invade oral epithelial cells. This article is part of a Special Issue entitled: HUPO 2014.

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