The involvement of the Mid1/Cch1/Yvc1 calcium channels in Aspergillus fumigatus virulence

PLoS One. 2014 Aug 1;9(8):e103957. doi: 10.1371/journal.pone.0103957. eCollection 2014.

Abstract

Aspergillus fumigatus is a major opportunistic pathogen and allergen of mammals. Calcium homeostasis and signaling is essential for numerous biological processes and also influences A. fumigatus pathogenicity. The presented study characterized the function of the A. fumigatus homologues of three Saccharomyces cerevisiae calcium channels, voltage-gated Cch1, stretch-activated Mid1 and vacuolar Yvc1. The A. fumigatus calcium channels cchA, midA and yvcA were regulated at transcriptional level by increased calcium levels. The YvcA::GFP fusion protein localized to the vacuoles. Both ΔcchA and ΔmidA mutant strains showed reduced radial growth rate in nutrient-poor minimal media. Interestingly, this growth defect in the ΔcchA strain was rescued by the exogenous addition of CaCl2. The ΔcchA, ΔmidA, and ΔcchA ΔmidA strains were also sensitive to the oxidative stress inducer, paraquat. Restriction of external Ca(2+) through the addition of the Ca(2+)-chelator EGTA impacted upon the growth of the ΔcchA and ΔmidA strains. All the A. fumigatus ΔcchA, ΔmidA, and ΔyvcA strains demonstrated attenuated virulence in a neutropenic murine model of invasive pulmonary aspergillosis. Infection with the parental strain resulted in a 100% mortality rate at 15 days post-infection, while the mortality rate of the ΔcchA, ΔmidA, and ΔyvcA strains after 15 days post-infection was only 25%. Collectively, this investigation strongly indicates that CchA, MidA, and YvcA play a role in A. fumigatus calcium homeostasis and virulence.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antifungal Agents / pharmacology
  • Aspergillus fumigatus / genetics
  • Aspergillus fumigatus / growth & development
  • Aspergillus fumigatus / metabolism*
  • Aspergillus fumigatus / pathogenicity*
  • Calcium Channels / genetics
  • Calcium Channels / metabolism*
  • Cytoplasm / drug effects
  • Cytoplasm / metabolism
  • Disease Models, Animal
  • Female
  • Fungal Proteins / genetics
  • Fungal Proteins / metabolism*
  • Gene Expression Regulation, Fungal / drug effects
  • Green Fluorescent Proteins / metabolism
  • Mice, Inbred BALB C
  • Mutation / genetics
  • Neutropenia / microbiology
  • Neutropenia / pathology
  • RNA, Messenger / genetics
  • RNA, Messenger / metabolism
  • Sequence Homology, Amino Acid
  • Virulence / drug effects

Substances

  • Antifungal Agents
  • Calcium Channels
  • Fungal Proteins
  • RNA, Messenger
  • Green Fluorescent Proteins

Grant support

This work was supported by Fundação de Amparo a Pesquisa do Estado de São Paulo (FAPESP, www.fapesp.br) and Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq, www.cnpq.br), Brazil. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.