title: Reductive iron uptake by Candida albicans: role of copper, iron and the TUP1 regulator.
abstract: High-affinity iron uptake by a ferrous permease in the opportunistic pathogen Candida albicans is required for virulence. Here this iron uptake system has been characterized by investigating three distinct activities: an externally directed surface ferric reductase, a membrane-associated PPD (p-phenylenediamine) oxidase and a cellular ferrous iron transport activity. Copper was required for the PPD oxidase and ferrous transport activities. In contrast, copper was not required for iron uptake from siderophores. Addition of iron to the growth medium repressed ferric reductase and ferrous transport, indicating homeostatic regulation. To identify the genes involved, orthologous mutants of Saccharomyces cerevisiae were transformed with a genomic library of C. albicans. CFL95, a gene with sequence similarity to ferric reductases, restored reductase activity to the orthologous S. cerevisiae mutant. CaFTR2 and CaFTR1, genes with homology to ferrous permeases, conferred ferrous transport activity to the orthologous S. cerevisiae mutant. However, neither a genomic library nor CaFET99, a multicopper oxidase homologue and candidate gene for the PPD oxidase, complemented the S. cerevisiae mutant, possibly because of problems with targeting or assembly. Transcripts for CFL95, CaFTR1 and CaFET99 were strongly repressed by iron, whereas the CaFTR2 transcript was induced by iron. Deletion of the TUP1 regulator perturbed the homeostatic control of reductive iron uptake. Incidentally, iron starvation was noted to induce flavin production and this was misregulated in the absence of TUP1 control. The opposite regulation of two iron permease genes and the role of TUP1 indicate that the process of iron acquisition by C. albicans may be more complex and potentially more adaptable than by S. cerevisiae.
authors.affiliation: Department of Medicine, Division of Hematology-Oncology, University of Pennsylvania, Philadelphia, PA 19104, USA1.
authors.forename: Simon A B
authors.initials: SAB
authors.lastname: Knight
authors.affiliation: Laboratoire d'Ingénierie des Protéines et Contrôle Métabolique, Institut Jacques Monod, Tour 43, Université Paris 7/Paris 6, 2 Place Jussieu, 75251 Paris Cedex 05, France2.
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Lesuisse
authors.affiliation: Office of the Director, NCI, National Institutes of Health, Bethesda, MD 20892, USA3.
authors.forename: Robert
authors.initials: R
authors.lastname: Stearman
authors.affiliation: Office of the Director, NCI, National Institutes of Health, Bethesda, MD 20892, USA3.
authors.forename: Richard D
authors.initials: RD
authors.lastname: Klausner
authors.affiliation: Department of Medicine, Division of Hematology-Oncology, University of Pennsylvania, Philadelphia, PA 19104, USA1.
authors.forename: Andrew
authors.initials: A
authors.lastname: Dancis
mesh_terms: D002176:Candida albicans / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D003300:Copper / Q000378:metabolism*; D003470:Culture Media; D038181:FMN Reductase; D005296:Ferrous Compounds / Q000378:metabolism; D005415:Flavins / Q000378:metabolism; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D015966:Gene Expression Regulation, Fungal; D005816:Genetic Complementation Test; D007501:Iron / Q000378:metabolism*; D009247:NADH, NADPH Oxidoreductases / Q000235:genetics / Q000378:metabolism*; D009687:Nuclear Proteins; D010084:Oxidation-Reduction; D000587:Oxidoreductases Acting on CH-NH Group Donors / Q000235:genetics / Q000378:metabolism; D012097:Repressor Proteins; D029701:Saccharomyces cerevisiae Proteins; D017262:Siderophores / Q000378:metabolism
chemical_list: D003470:Culture Media; D005296:Ferrous Compounds; D005415:Flavins; D005656:Fungal Proteins; D009687:Nuclear Proteins; D012097:Repressor Proteins; D029701:Saccharomyces cerevisiae Proteins; D017262:Siderophores; C066502:TUP1 protein, S cerevisiae; D003300:Copper; D007501:Iron; C022345:4-phenylenediamine oxidase; D000587:Oxidoreductases Acting on CH-NH Group Donors; D038181:FMN Reductase; D009247:NADH, NADPH Oxidoreductases; C023903:ferric citrate iron reductase