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Divergent targets of Aspergillus fumigatus AcuK and AcuM transcription factors during growth in vitro versus invasive disease.

ABSTRACT: In Aspergillus nidulans, the AcuK and AcuM transcription factors form a complex that regulates gluconeogenesis. In Aspergillus fumigatus, AcuM governs gluconeogenesis and iron acquisition in vitro and virulence in immunosuppressed mice. However, the function of AcuK was previously unknown. Through in vitro studies, we found that A. fumigatus ?acuK single and ?acuK ?acuM double mutants had impaired gluconeogenesis and iron acquisition, similar to the ?acuM mutant. Also, the ?acuK, ?acuM, and ?acuK ?acuM mutants had similar virulence defects in mice. However, the ?acuK mutant had a milder defect in extracellular siderophore activity and induction of epithelial cell damage in vitro than did the ?acuM mutant. Moreover, overexpression of acuM in the ?acuK mutant altered expression of 3 genes and partially restored growth under iron-limited conditions, suggesting that AcuM can govern some genes independently of AcuK. Although the ?acuK and ?acuM mutants had very similar transcriptional profiles in vitro, their transcriptional profiles during murine pulmonary infection differed both from their in vitro profiles and from each other. While AcuK and AcuM governed the expression of only a few iron-responsive genes in vivo, they influenced the expression of other virulence-related genes, such as hexA and dvrA. Therefore, in A. fumigatus, while AcuK and AcuM likely function as part of the same complex, they can also function independently of each other. Furthermore, AcuK and AcuM have different target genes in vivo than in vitro, suggesting that in vivo infection stimulates unique transcriptional regulatory pathways in A. fumigatus.

SUBMITTER: Pongpom M

PROVIDER: S-EPMC4333448 | biostudies-literature | 2015 Mar

REPOSITORIES: biostudies-literature

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Divergent targets of Aspergillus fumigatus AcuK and AcuM transcription factors during growth in vitro versus invasive disease.

Pongpom Monsicha M Liu Hong H Xu Wenjie W Snarr Brendan D BD Sheppard Donald C DC Mitchell Aaron P AP Filler Scott G SG

Infection and immunity 20141222 3

In Aspergillus nidulans, the AcuK and AcuM transcription factors form a complex that regulates gluconeogenesis. In Aspergillus fumigatus, AcuM governs gluconeogenesis and iron acquisition in vitro and virulence in immunosuppressed mice. However, the function of AcuK was previously unknown. Through in vitro studies, we found that A. fumigatus ΔacuK single and ΔacuK ΔacuM double mutants had impaired gluconeogenesis and iron acquisition, similar to the ΔacuM mutant. Also, the ΔacuK, ΔacuM, and Δacu ...[more]

PMID: 25534941

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Project description:BackgroundCalcineurin, a serine/threonine-specific protein phosphatase, plays an important role in the control of cell morphology and virulence in fungi. Calcineurin regulates localization and activity of a transcription factor called CRZ1. Recently, we characterize Aspergillus fumigatus CRZ1 homologue, AfCrzA. Here, we investigate which pathways are influenced by A. fumigatus AfCrzA during a short pulse of calcium by comparatively determining the transcriptional profile of A. fumigatus wild type and DeltaAfcrzA mutant strains.ResultsWe were able to observe 3,622 genes modulated in at least one timepoint in the mutant when compared to the wild type strain (3,211 and 411 at 10 and 30 minutes, respectively). Decreased mRNA abundance in the DeltacrzA was seen for genes encoding calcium transporters, transcription factors and genes that could be directly or indirectly involved in calcium metabolism. Increased mRNA accumulation was observed for some genes encoding proteins involved in stress response. AfCrzA overexpression in A. fumigatus increases the expression of several of these genes. The deleted strain of one of these genes, AfRcnA, belonging to a class of endogenous calcineurin regulators, calcipressins, had more calcineurin activity after exposure to calcium and was less sensitive to menadione 30 microM, hydrogen peroxide 2.5 mM, EGTA 25 mM, and MnCl2 25 mM. We constructed deletion, overexpression, and GFP fusion protein for the closely related A. nidulans AnRcnA. GFP::RcnA was mostly detected along the germling, did not accumulate in the nuclei and its location is not affected by the cellular response to calcium chloride.ConclusionWe have performed a transcriptional profiling analysis of the A. fumigatus DeltaAfcrzA mutant strain exposed to calcium stress. This provided an excellent opportunity to identify genes and pathways that are under the influence of AfCrzA. AfRcnA, one of these selected genes, encodes a modulator of calcineurin activity. Concomitantly with A. fumigatus AfrcnA molecular analysis, we decided to exploit the conserved features of A. nidulans calcineurin system and investigated the A. nidulans AnRcnA homologue. A. nidulans AnRcnA mutation is suppressing CnaA mutation and it is responsible for modulating the calcineurin activity and mRNA accumulation of genes encoding calcium transporters.

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Divergent targets of Aspergillus fumigatus AcuK and AcuM transcription factors during growth in vitro versus invasive disease.

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Divergent targets of Aspergillus fumigatus AcuK and AcuM transcription factors during growth in vitro versus invasive disease.

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