Resist or die: Identification and functional characterization of cell wall integrity determinants important for the survival of Aspergillus fumigatus challenged by neutrophil granulocytes.
Final Report Abstract
The opportunistic pathogenic mold Aspergillus fumigatus poses a significant threat to immunocompromised patients, especially those with impaired neutrophil granulocyte function. The aim of the project was to identify and characterize factors that influence the survival of A. fumigatus upon contact with human granulocytes. Our investigations demonstrated that granulocytes activate the cell wall integrity pathway of A. fumigatus. The cell wall stress sensor MidA and the Rho-GTPase Rho2 play a crucial role for the survival of A. fumigatus hyphae in contact with granulocytes. Overexpression of Rho2 resulted in increased resistance and an altered cell wall composition, but also to reduced growth of the fungus. Continuous activation of Rho2 led to increasing cell wall stress and cell wall changes with excessive accumulation of chitin and was lethal to the fungus in the long term. Azole antifungals trigger similar changes in the cell wall. For this reason, a possible connection between the Rho2- and azole-induced cell wall changes was investigated. Here, among other things, it was shown that the azole-induced cell wall changes are formed independently of Rho2. However, it could not be ruled out that in both cases the same mechanism is responsible for the cell wall changes. Moreover, it was shown that azoles cause the accumulation of the ergosterol intermediate eburicol, which contributes to the formation of cell wall changes. Further investigations focused on the peroxiredoxin Asp f3, which was identified as an important virulence factor and scavenger of reactive oxygen species. Despite increased sensitivity to hydrogen peroxide, reduced Asp f3 expression does not result in increased sensitivity to granulocytes. Instead, a growth defect under iron depletion was detected when Asp f3 expression was reduced. The results of this project demonstrate the importance of the cell wall stress signaling pathway for the survival of A. fumigatus when challenged by human granulocytes and highlight the role of the Rho-GTPase Rho2 in the upregulation of cell wall biosynthesis that allows the fungus to survive under these stress conditions. In addition, we uncovered an unexpected role of peroxiredoxin Asp f3 in the virulence of A. fumigatus and further dissected the mechanisms leading to cell wall alterations in A. fumigatus upon treatment with azole antifungals.
Publications
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Peroxiredoxin Asp f3 Is Essential for Aspergillus fumigatus To Overcome Iron Limitation during Infection. mBio, 12(4).
Brantl, Victor; Boysen, Jana M.; Yap, Annie; Golubtsov, Evgeny; Ruf, Dominik; Heinekamp, Thorsten; Straßburger, Maria; Dichtl, Karl; Haas, Hubertus; Hillmann, Falk & Wagener, Johannes
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Only One of Three Bcs1 Homologs in Aspergillus fumigatus Confers Respiratory Growth. Journal of Fungi, 9(11), 1074.
Klugherz, Isabel; Basch, Marion; Ng, Natanya; Zhu, Zhaojun; Wagener, Nikola & Wagener, Johannes
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Quantifying Isoprenoids in the Ergosterol Biosynthesis by Gas Chromatography–Mass Spectrometry. Journal of Fungi, 9(7), 768.
Liebl, Maximilian; Huber, Ludwig; Elsaman, Hesham; Merschak, Petra; Wagener, Johannes; Gsaller, Fabio & Müller, Christoph
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Toxic eburicol accumulation drives the antifungal activity of azoles against Aspergillus fumigatus. Nature Communications, 15(1).
Elsaman, Hesham; Golubtsov, Evgeny; Brazil, Sean; Ng, Natanya; Klugherz, Isabel; Martin, Ronny; Dichtl, Karl; Müller, Christoph & Wagener, Johannes
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Rho2 regulates granulocyte-triggered stress adaptation and cell wall remodeling in Aspergillus fumigatus. openRxiv.
Ruf, Dominik; Striegler, Kristina; Brazil, Sean; Elsaman, Hesham; Singh, Kalpana; Lepas, Mathieu; Fernando, Liyanage D.; Brantl, Victor; Heß, Patricia; Dichtl, Karl; Aimanianda, Vishukumar; Wang, Tuo & Wagener, Johannes
