Project description:Fungal spores and hyphal fragments are major contributors to the allergic response in the human lung. In this study, using a trypsin-shaving-proteomics approach, we identified the surface-exposed and secreted/shed proteins of Aspergillus fumigatus conidia and investigated the dynamics of the surface proteome under different conditions, including temperature variation and germination. We find that the surface proteome of resting A. fumigatus conidia is quite dynamic, as evidenced by drastically different surface proteomes under different growth conditions. We further investigated two observed A. fumigatus surface proteins, ScwA and CweA; ScwA is specific to the Aspergillus genus and only expressed on conidia grown at higher temperatures, whereas CweA is found throughout the Aspergillus and Penicillium genera. We extended our analysis of the surface proteome of A. fumigatus to other allergy-inducing pathogens; Alternaria alternata, Penicillium rubens, and Cladosporium herbarum, and performed comparative proteomics on resting and swollen conidia, as well as secreted proteins from germinating conidia. In this dataset, we detected 125 protein orthologs in the extracellular region of all four organisms, and 42 nonorthologous proteins produced by A. fumigatus, which may be useful in the development of future diagnostics. This study highlights the dynamic nature of the conidial surface and implicates growth conditions in the antigenicity of fungal conidia.
Project description:We have focused our investigation on the characterization of the role of the fungal specific SWI/SNF subunit, Snf6. Our data show that, although the C. albicans subunit has only limited sequence similarity to other fungal orthologs, Snf6 was copurified with SWI/SNF complex subunits including the catalytic ATPase subunit, Snf2. We show that Snf6 plays a critical role in biological processes that are essential for fungal pathogenesis including carbon metabolic flexibility, stress response and morphogenesis. The Snf6 regulon was determined by combining both genome-wide location (ChIP-chip) and transcriptional profiling (microarrays) to identify targets of the SWI/SNF complex under both yeast- and hyphal-promoting conditions.
Project description:Regulation of iron acquisition genes is critical for microbial survival under both iron-limiting conditions (to acquire essential iron) and iron-replete conditions (to limit iron toxicity). In fungi, iron acquisition genes are repressed under iron-replete conditions by a conserved GATA transcriptional regulator. Here we investigate the role of this transcription factor, Sre1, in the cellular responses of the fungal pathogen Histoplasma capsulatum to iron. We showed that cells in which SRE1 levels were diminished by RNA interference were unable to repress siderophore biosynthesis and utilization genes in the presence of abundant iron, and thus produced siderophores even under iron-replete conditions. Mutation of a GATA-containing consensus site found in the promoters of these genes also resulted in inappropriate gene expression under iron-replete conditions. Microarray analysis comparing control and SRE1-depleted strains under conditions of iron limitation or abundance revealed both iron-responsive genes and Sre1-dependent genes, which comprised distinct but overlapping sets. Iron-responsive genes included putative oxidoreductases, metabolic and mitochondrial enzymes, superoxide dismutase, and nitrosative-stress response genes; Sre1-dependent genes were of diverse function. Genes regulated by iron levels and Sre1 included all of the siderophore biosynthetic genes, a gene involved in reductive iron acquisition, an iron-responsive transcription factor, and two catalases. Based on transcriptional profiling and phenotypic analyses, we conclude that Sre1 plays a critical role in the regulation of both traditional iron-responsive genes and iron-independent pathways such as regulation of cell morphology. These data highlight the evolving realization that the effect of Sre1 orthologs on fungal biology extends beyond the iron regulon.
Project description:RATIONALE: Gathering information about how often fungal infections of the blood occur in patients with cancer or in patients who have undergone stem cell transplant may help doctors learn more about the disease.
PURPOSE: This natural history study is collecting information about fungal infections of the blood over time from patients with cancer or from patients who have undergone a stem cell transplant.
Project description:As transition metal availability is very limited inside the human host, fungal pathogens have evolved sophisticated mechanisms to uptake and utilize these micronutrients at the infection interface. While considerable attention was turned into iron, copper and zinc acquisition mechanisms and their importance in fungal fitness, less was done regarding either the role of Mn in infectious processes or the cellular mechanism by which fungal cells achieve their Mn-homeostasis. Here, we undertook a transcriptional profiling of the pathogenic fungus Candida albicans experiencing both Mn starvation and excess to comprehensibly capture biological processes that are modulated by Mn. We uncovered that Mn scarcity influence diverse biological processes associated with fungal fitness including morphogenetic switch, invasion of host cells and antifungal sensitivity. We also uncovered that Mn levels influence the abundance of iron and zinc emphasizing the complex crosstalk between ions metals. Deletion of SMF12, a member of Mn Nramp transporters confirmed its contribution to Mn uptake. In accordance with the RNA-seq data, smf12 was unable to form hyphae and damage host cells, and exhibited sensitivity to azole antifungals. We also found that unfolded protein response (UPR), likely activated by decreased glycosylation under Mn limitation, was essential to promote C. albicans growth. RNA-seq profiling of cells exposed to Mn excess uncovered that the UPR signaling was also essential to bypass Mn toxicity. Collectively, this study underscores the importance of Mn homeostasis in fungal virulence, and comprehensively provides a transcriptional portrait of biological functions that are modulated by Mn in a fungal pathogen.