The monothiol glutaredoxin GrxD is essential for sensing iron starvation in Aspergillus fumigatus

PLoS Genet. 2019 Sep 16;15(9):e1008379. doi: 10.1371/journal.pgen.1008379. eCollection 2019 Sep.

Abstract

Efficient adaptation to iron starvation is an essential virulence determinant of the most common human mold pathogen, Aspergillus fumigatus. Here, we demonstrate that the cytosolic monothiol glutaredoxin GrxD plays an essential role in iron sensing in this fungus. Our studies revealed that (i) GrxD is essential for growth; (ii) expression of the encoding gene, grxD, is repressed by the transcription factor SreA in iron replete conditions and upregulated during iron starvation; (iii) during iron starvation but not iron sufficiency, GrxD displays predominant nuclear localization; (iv) downregulation of grxD expression results in de-repression of genes involved in iron-dependent pathways and repression of genes involved in iron acquisition during iron starvation, but did not significantly affect these genes during iron sufficiency; (v) GrxD displays protein-protein interaction with components of the cytosolic iron-sulfur cluster biosynthetic machinery, indicating a role in this process, and with the transcription factors SreA and HapX, which mediate iron regulation of iron acquisition and iron-dependent pathways; (vi) UV-Vis spectra of recombinant HapX or the complex of HapX and GrxD indicate coordination of iron-sulfur clusters; (vii) the cysteine required for iron-sulfur cluster coordination in GrxD is in vitro dispensable for interaction with HapX; and (viii) there is a GrxD-independent mechanism for sensing iron sufficiency by HapX; (ix) inactivation of SreA suppresses the lethal effect caused by GrxD inactivation. Taken together, this study demonstrates that GrxD is crucial for iron homeostasis in A. fumigatus.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aspergillus fumigatus / genetics
  • Aspergillus fumigatus / metabolism
  • Fungal Proteins / genetics
  • Gene Expression Regulation, Fungal / genetics
  • Glutaredoxins / genetics*
  • Glutaredoxins / metabolism*
  • Homeostasis
  • Iron / deficiency
  • Iron / metabolism*
  • Starvation
  • Transcription Factors / genetics
  • Virulence

Substances

  • Fungal Proteins
  • Glutaredoxins
  • Transcription Factors
  • Iron

Grant support

This work was supported by the joint D-A-CH program ‘Novel molecular mechanisms of iron sensing and homeostasis in filamentous fungi’, Austrian Science Fund (www.fwf.ac.at) project I1346-B22 to HH, Deutsche Forschungsgemeinschaft (www.dfg.de) project BR 1130/14-1 to AAB, Deutsche Forschungsgemeinschaft (www.dfg.de) project HO 2596/1-1 to PH, and Deutsche Forschungsgemeinschaft (www.dfg.de) Collaborative Research Center/Transregio 124 FungiNet (www.funginet.de) project Z2 to OK. Moreover, this article is based upon work from COST Action 15133: ‘The Biogenesis of Iron-sulfur Proteins: from Cellular Biology to Molecular Aspects’ (FeSBioNet; www.cost.eu/actions/CA15133), supported by COST (European Cooperation in Science and Technology). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.