Exploration of whole-genome responses of the human AIDS-associated yeast pathogen Cryptococcus neoformans var grubii: nitric oxide stress and body temperature

Abstract

Cryptococcus neoformans var grubii is an opportunistic basidiomycete yeast pathogen that is a significant cause of HIV/AIDS-related deaths worldwide. We describe a whole-genome oligonucleotide microarray for this pathogen. These arrays have been used to elucidate the transcriptional responses of the genome to heat shock as well as to two conditions relevant to human infections: body temperature and nitric oxide (NO) stress produced by the NO donor DPTA-NONOate. This analysis revealed an NO-inducible C. neoformans-specific four-gene family that showed a highly similar transcriptional profile to that of FHB1, a previously described NO dioxygenase/flavohemoglobin required for virulence. NO treatment also induced genes involved in the synthesis of the antioxidant mannitol, a polyol that accumulates in the cerebrospinal fluid of infected patients. Exposure to NO also caused increased expression of the sole C. neoformans var grubii protein with HHE/hemerythrin cation binding motifs. Notably, a similar gene in E. coli, ytfE, has been shown to be NO-inducible and protects bacterial cells from killing by NO. Genes induced by NO were highly enriched for those repressed at 37 degrees C, indicating an unexpected interplay between temperature and NO regulation in this basidiomycete. Resources described here should facilitate future investigations of this lethal human yeast pathogen.

Rewiring of Signaling Networks Modulating Thermotolerance in the Human Pathogen Cryptococcus neoformans

“…We compared our array data of the WT strain to those from other microarray analyses performed independently to identify temperature-regulated or heat-shock responsive genes in C. neoformans (Steen et al 2002;Kraus et al 2004;Chow et al 2007). Steen et al (2002) demonstrated that the tag representing cyclophilin A (CPA1 and CPA2) is expressed at higher levels at 37°than at 25°.…”

“…Steen et al (2002) reported that a peroxiredoxin (TSA1) and a superoxide dismutase (SOD) are highly expressed at 37°. Similarly, Chow et al (2007) reported that the expression of the genes involved in the thioredoxin system (TRR1, thioredoxin reductase; TRX3, thioredoxin) is induced by the heat shock response. In addition, Kraus et al (2004) reported that several catalase genes were induced by high temperature.…”

“…Our array analysis confirmed that expression of some of the heat shock genes, including KAR2, HSP104, and HSP78, was strongly induced by temperature shift and also revealed that a number of other heat shock genes, including HSP12, SSB2, SSC1, SSA1-like gene (CNAG_01727), SSE1, AHA1, CDC37, and HSP10, also showed this effect. Chow et al (2007) reported that the expression of genes involved in ergosterol biosynthesis (ERG3, ERG4, ERG502, ERG25, and OSH6) is repressed by heat. In addition to the reported ergosterol biosynthesis genes (ERG3, ERG4, and ERG25), our study also revealed that the expression of a number of other ergosterol biosynthesis genes, including ERG2, ERG5, ERG6, ERG8, ERG10, ERG11, ERG13, ERG20, ERG24, NCP1, and MVD1, was repressed by high temperature.…”

“…We also found that SLG1, MGA2, RDS1, SMG1, TPS1, and RIM15 expression was induced during temperature upshift, while ILV2, ILV5, and URA2 expression was repressed (Table S3 and Table S4). Chow et al (2007) demonstrated that a number of heat shock genes (KAR2, HSC8202, HSP104, HSP78, SSA4, STI101, SSE2, and LHS1) are induced during temperature shift. Our array analysis confirmed that expression of some of the heat shock genes, including KAR2, HSP104, and HSP78, was strongly induced by temperature shift and also revealed that a number of other heat shock genes, including HSP12, SSB2, SSC1, SSA1-like gene (CNAG_01727), SSE1, AHA1, CDC37, and HSP10, also showed this effect.…”

Ccr4 Promotes Resolution of the Endoplasmic Reticulum Stress Response during Host Temperature Adaptation in Cryptococcus neoformans

“…Unifying characteristics of the pathogenic cryptococci include the production of a polysaccharide capsule, the ability to form melanin pigments through the activity of the multicopper oxidase laccase, and the ability to adapt to and thrive at mammalian host temperature. Adaptation of C. neoformans to the host temperature is accompanied by major changes in gene expression as measured by microarray analysis and serial analysis of gene expression (SAGE) (5,19,29). This modulation of gene expression likely requires alterations in mRNA synthesis rates through activation of transcriptional transactivators and repressors, as well as alterations in chromatin structure.…”