Purpurin-induced changes in the proteome of Candida albicans

Abstract

OBJECTIVES: To identify the changes in protein abundance in Candida albicans after exposure to purpurin. METHODS: The optimal inhibitory dose of purpurin for proteomic analysis of C. albicans was determined by measuring fungal growth in YPD broth in the presence of a range of purpurin concentration (1-5 μg/mL) for 16 h. For proteomic analysis, total soluble proteins of purpurin-treated and untreated (DMSO only) fungal cells were extracted by mechanical disruption. In the first dimension IEF analysis, protein extract (200 μg) was focused on IPG strips (pH 3-10). The second dimension SDS-PAGE was performed on a 12% gel. The relative protein abundance was determined after silver staining. Highly reproducible spots showing (> 1.5-fold) up- or down-regulation were selected for identification using a MALDI-TOF mass spectrometer. The peak lists were searched against NCBI database using an in-house MASCOT searching engine. RESULTS: We identified 12 differentially (five up-regulated; seven down-regulated) expressed protein spots in the purpurin-treated C. albicans. These proteins are involved in stress and heat shock responses, TCA cycle, amino acid and aldehyde metabolism, and mitochondrial functions. Of special interest was a substantial increase (> 3 fold) of the cellular level of aryl alcohol dehydrogenase. CONCLUSIONS: Purpurin induces changes in the proteome of C. albicans. Comparison of the differential protein expression patterns of the purpurin-treated C. albicans provides a better understanding of the antifungal mechanisms. The inhibitory effect of purpurin on Candida morphogenesis may be attributed to the up-regulation of aryl alcohol dehydrogenase, a crucial enzyme involved in the synthesis of quorum sensing molecules.