Aspergillus fumigatus Copper Export Machinery and Reactive Oxygen Intermediate Defense Counter Host Copper-Mediated Oxidative Antimicrobial Offense

Abstract

Summary The Fenton-chemistry generating properties of copper ions are considered a potent phagolysosome defense against pathogenic microbes, yet our understanding of underlying host/microbe dynamics remains unclear. We address this issue in invasive aspergillosis and demonstrate that host and fungal responses inextricably connect copper and reactive oxygen intermediate (ROI) mechanisms. Loss of the copper-binding transcription factor AceA yields an A. fumigatus strain displaying increased sensitivity to copper and ROI in vitro, increased intracellular copper concentrations, decreased survival in challenge with murine alveolar macrophages and reduced virulence in a non-neutropenic murine model. ΔaceA survival is remediated by dampening of host ROI (chemically or genetically) or enhancement of copper-exporting activity (CrpA) in A. fumigatus. Our study exposes a complex host/microbe multifactorial interplay that highlights the importance of host immune status and reveals key targetable A. fumigatus counter-defenses.

Contribution of ATPase copper transporters in animal but not plant virulence of the crossover pathogen Aspergillus flavus

“…The Cu exporter P1-type ATPase is the primary means for Cu detoxification in A. fumigatus [15]. To identify the Cu P1-type ATPase in Aspergillus species, the available protein sequences of the heavy-metal ATPases (HMA) from Aspergillus species available from the NCBI database were retrieved (http://www.aspgd.org).…”

“…On the other hand, Cu homeostasis has been shown to support the virulence of many fungal pathogens, which share many of the elements found in mammalian Cu regulatory systems including Cu-binding transcriptional factors (TFs), Cu-importers/exporters and Cu-metallothioneins (MTs)[2,15]. Fungal Cu-binding TFs tightly control expression levels of genes involved in Cu uptake and export under Cu-deficient conditions or Cu-excess respectively.…”

“…In Candida albicans , a membrane-localized P-type Cu ATPase, Crp1, is responsible for Cu resistance along with the MT Cup1, both of which are transcriptionally activated by Ace1 under high Cu conditions [19–21]. Recent studies also illustrated the regulation of Cu homeostasis in the filamentous fungi Aspergillus fumigatus and A. nidulans , both of which possess the same Cu export machinery [15,22,23]. In A. fumigatus and A. nidulans , the Cu-fist binding TF AceA senses high levels of Cu, and induces the Cu P-type ATPase CrpA as a detoxification mechanism [15,22].…”

“…Recent studies also illustrated the regulation of Cu homeostasis in the filamentous fungi Aspergillus fumigatus and A. nidulans , both of which possess the same Cu export machinery [15,22,23]. In A. fumigatus and A. nidulans , the Cu-fist binding TF AceA senses high levels of Cu, and induces the Cu P-type ATPase CrpA as a detoxification mechanism [15,22]. Both AceA and CrpA are virulence factors for the human pathogenic A. fumigatus .…”

“…As we have recently found that deletion of the Cu export machinery severely impairs A. fumigatus virulence [15], we queried if the same proteins were also important for virulence of A. flavus , both in its role as a plant and mammalian pathogen. Unexpectedly we found that A. flavus possesses two copies of the Cu exporter P1-type ATPase, CrpA and CrpB which results in greater tolerance of Cu in this species than other Aspergilli.…”