Transcriptional Profiling of Candida glabrata during Phagocytosis by Neutrophils and in the Infected Mouse Spleen

Expression microarray analysis of Candida glabrata following phagocytosis by human neutrophils was performed, and results were compared with those from C. glabrata incubated under conditions of carbohydrate or nitrogen deprivation. Twenty genes were selected to represent the major cell processes altered by phagocytosis or nutrient deprivation. Quantitative real-time PCR (qRT-PCR) with TaqMan chemistry was used to assess expression of the same genes in spleens of mice infected intravenously with Candida glabrata. The results in spleen closely paralleled gene expression in neutrophils or following carbohydrate deprivation. Fungal cells responded by upregulating alternative energy sources through gluconeogenesis, glyoxylate cycle, and long-chain fatty acid metabolism. Autophagy was likely employed to conserve intracellular resources. Aspartyl protease upregulation occurred and may represent defense against attacks on cell wall integrity. Downregulated genes were in the pathways of protein and ergosterol synthesis. Upregulation of the sterol transport gene AUS1 suggested that murine cholesterol may have been used to replace ergosterol, as has been reported in vitro. C. glabrata isolates in spleens of gp91(phox-/-) knockout mice with reduced oxidative phagocyte defenses were grossly similar although with a reduced level of response. These results are consistent with reported results of other fungi responding to phagocytosis, indicating that a rapid shift in metabolism is required for growth in a carbohydrate-limited intracellular environment.