title: Calcineurin controls drug tolerance, hyphal growth, and virulence in Candida dubliniensis.
abstract: Candida dubliniensis is an emerging pathogenic yeast species closely related to Candida albicans and frequently found colonizing or infecting the oral cavities of HIV/AIDS patients. Drug resistance during C. dubliniensis infection is common and constitutes a significant therapeutic challenge. The calcineurin inhibitor FK506 exhibits synergistic fungicidal activity with azoles or echinocandins in the fungal pathogens C. albicans, Cryptococcus neoformans, and Aspergillus fumigatus. In this study, we show that calcineurin is required for cell wall integrity and wild-type tolerance of C. dubliniensis to azoles and echinocandins; hence, these drugs are candidates for combination therapy with calcineurin inhibitors. In contrast to C. albicans, in which the roles of calcineurin and Crz1 in hyphal growth are unclear, here we show that calcineurin and Crz1 play a clearly demonstrable role in hyphal growth in response to nutrient limitation in C. dubliniensis. We further demonstrate that thigmotropism is controlled by Crz1, but not calcineurin, in C. dubliniensis. Similar to C. albicans, C. dubliniensis calcineurin enhances survival in serum. C. dubliniensis calcineurin and crz1/crz1 mutants exhibit attenuated virulence in a murine systemic infection model, likely attributable to defects in cell wall integrity, hyphal growth, and serum survival. Furthermore, we show that C. dubliniensis calcineurin mutants are unable to establish murine ocular infection or form biofilms in a rat denture model. That calcineurin is required for drug tolerance and virulence makes fungus-specific calcineurin inhibitors attractive candidates for combination therapy with azoles or echinocandins against emerging C. dubliniensis infections.
authors.affiliation: Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC 27710, USA.
authors.forename: Ying-Lien
authors.initials: YL
authors.lastname: Chen
authors.forename: Alexandra
authors.initials: A
authors.lastname: Brand
authors.forename: Emma L
authors.initials: EL
authors.lastname: Morrison
authors.forename: Fitz Gerald S
authors.initials: FG
authors.lastname: Silao
authors.forename: Ursela G
authors.initials: UG
authors.lastname: Bigol
authors.forename: Fedelino F
authors.initials: FF
authors.lastname: Malbas
authors.forename: Jeniel E
authors.initials: JE
authors.lastname: Nett
authors.forename: David R
authors.initials: DR
authors.lastname: Andes
authors.forename: Norma V
authors.initials: NV
authors.lastname: Solis
authors.forename: Scott G
authors.initials: SG
authors.lastname: Filler
authors.forename: Anna
authors.initials: A
authors.lastname: Averette
authors.forename: Joseph
authors.initials: J
authors.lastname: Heitman
mesh_terms: D000818:Animals; D000935:Antifungal Agents / Q000494:pharmacology; D018441:Biofilms / Q000254:growth & development*; D019703:Calcineurin / Q000235:genetics* / Q000378:metabolism; D002175:Candida / Q000187:drug effects / Q000254:growth & development / Q000472:pathogenicity*; D058387:Candidemia / Q000382:microbiology; D002180:Candidiasis, Oral / Q000382:microbiology; D000077336:Caspofungin; D015169:Colony Count, Microbial; D003778:Dentures; D025141:Drug Resistance, Fungal / Q000235:genetics*; D054714:Echinocandins / Q000494:pharmacology; D015821:Eye Infections, Fungal / Q000382:microbiology; D015725:Fluconazole / Q000494:pharmacology; D055785:Gene Knockdown Techniques; D006801:Humans; D025301:Hyphae / Q000235:genetics*; D055666:Lipopeptides; D008297:Male; D051379:Mice; D008813:Mice, Inbred ICR; D050296:Microbial Viability; D009036:Moths / Q000382:microbiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D014774:Virulence
chemical_list: D000935:Antifungal Agents; D054714:Echinocandins; D055666:Lipopeptides; D015725:Fluconazole; D019703:Calcineurin; D000077336:Caspofungin