Dsc orthologs are required for hypoxia adaptation, triazole drug responses, and fungal virulence in Aspergillus fumigatus

Eukaryot Cell. 2012 Dec;11(12):1557-67. doi: 10.1128/EC.00252-12. Epub 2012 Oct 26.

Abstract

Hypoxia is an environmental stress encountered by Aspergillus fumigatus during invasive pulmonary aspergillosis (IPA). The ability of this mold to adapt to hypoxia is important for fungal virulence and genetically regulated in part by the sterol regulatory element binding protein (SREBP) SrbA. SrbA is required for fungal growth in the murine lung and to ultimately cause lethal disease in murine models of IPA. Here we identified and partially characterized four genes (dscA, dscB, dscC, and dscD, here referred to as dscA-D) with previously unknown functions in A. fumigatus that are orthologs of the Schizosaccharomyces pombe genes dsc1, dsc2, dsc3, and dsc4 (dsc1-4), which encode a Golgi E3 ligase complex critical for SREBP activation by proteolytic cleavage. A. fumigatus null dscA-D mutants displayed remarkable defects in hypoxic growth and increased susceptibility to triazole antifungal drugs. Consistent with the confirmed role of these genes in S. pombe, both ΔdscA and ΔdscC resulted in reduced cleavage of the SrbA precursor protein in A. fumigatus. Inoculation of corticosteroid immunosuppressed mice with ΔdscA and ΔdscC strains revealed that these genes are critical for A. fumigatus virulence. Reintroduction of SrbA amino acids 1 to 425, encompassing the N terminus DNA binding domain, into the ΔdscA strain was able to partially restore virulence, further supporting a mechanistic link between DscA and SrbA function. Thus, we have shown for the first time the importance of a previously uncharacterized group of genes in A. fumigatus that mediate hypoxia adaptation, fungal virulence, and triazole drug susceptibility and that are likely linked to regulation of SrbA function.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptation, Biological / genetics*
  • Anaerobiosis / genetics
  • Animals
  • Antifungal Agents / toxicity
  • Aspergillus fumigatus / genetics
  • Aspergillus fumigatus / metabolism*
  • Aspergillus fumigatus / pathogenicity
  • Drug Resistance, Fungal* / genetics
  • Female
  • Fungal Proteins / chemistry
  • Fungal Proteins / genetics*
  • Fungal Proteins / metabolism
  • Mice
  • Protein Precursors / chemistry
  • Protein Precursors / genetics*
  • Protein Precursors / metabolism
  • Protein Processing, Post-Translational
  • Protein Structure, Tertiary
  • Proteolysis
  • Triazoles / toxicity
  • Ubiquitin-Protein Ligases / chemistry
  • Ubiquitin-Protein Ligases / genetics*
  • Ubiquitin-Protein Ligases / metabolism
  • Virulence / genetics

Substances

  • Antifungal Agents
  • Fungal Proteins
  • Protein Precursors
  • Triazoles
  • Ubiquitin-Protein Ligases