title: Hsp90 governs dispersion and drug resistance of fungal biofilms.
abstract: Fungal biofilms are a major cause of human mortality and are recalcitrant to most treatments due to intrinsic drug resistance. These complex communities of multiple cell types form on indwelling medical devices and their eradication often requires surgical removal of infected devices. Here we implicate the molecular chaperone Hsp90 as a key regulator of biofilm dispersion and drug resistance. We previously established that in the leading human fungal pathogen, Candida albicans, Hsp90 enables the emergence and maintenance of drug resistance in planktonic conditions by stabilizing the protein phosphatase calcineurin and MAPK Mkc1. Hsp90 also regulates temperature-dependent C. albicans morphogenesis through repression of cAMP-PKA signalling. Here we demonstrate that genetic depletion of Hsp90 reduced C. albicans biofilm growth and maturation in vitro and impaired dispersal of biofilm cells. Further, compromising Hsp90 function in vitro abrogated resistance of C. albicans biofilms to the most widely deployed class of antifungal drugs, the azoles. Depletion of Hsp90 led to reduction of calcineurin and Mkc1 in planktonic but not biofilm conditions, suggesting that Hsp90 regulates drug resistance through different mechanisms in these distinct cellular states. Reduction of Hsp90 levels led to a marked decrease in matrix glucan levels, providing a compelling mechanism through which Hsp90 might regulate biofilm azole resistance. Impairment of Hsp90 function genetically or pharmacologically transformed fluconazole from ineffectual to highly effective in eradicating biofilms in a rat venous catheter infection model. Finally, inhibition of Hsp90 reduced resistance of biofilms of the most lethal mould, Aspergillus fumigatus, to the newest class of antifungals to reach the clinic, the echinocandins. Thus, we establish a novel mechanism regulating biofilm drug resistance and dispersion and that targeting Hsp90 provides a much-needed strategy for improving clinical outcome in the treatment of biofilm infections.
authors.affiliation: Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Nicole
authors.initials: N
authors.lastname: Robbins
authors.forename: Priya
authors.initials: P
authors.lastname: Uppuluri
authors.forename: Jeniel
authors.initials: J
authors.lastname: Nett
authors.forename: Ranjith
authors.initials: R
authors.lastname: Rajendran
authors.forename: Gordon
authors.initials: G
authors.lastname: Ramage
authors.forename: Jose L
authors.initials: JL
authors.lastname: Lopez-Ribot
authors.forename: David
authors.initials: D
authors.lastname: Andes
authors.forename: Leah E
authors.initials: LE
authors.lastname: Cowen
mesh_terms: D000935:Antifungal Agents / Q000494:pharmacology; D001232:Aspergillus fumigatus / Q000187:drug effects / Q000235:genetics* / Q000254:growth & development; D001393:Azoles / Q000494:pharmacology; D018441:Biofilms / Q000187:drug effects* / Q000254:growth & development; D019703:Calcineurin / Q000235:genetics / Q000378:metabolism; D002176:Candida albicans / Q000187:drug effects / Q000235:genetics* / Q000254:growth & development; D025141:Drug Resistance, Fungal / Q000235:genetics; D054714:Echinocandins / Q000378:metabolism; D015725:Fluconazole / Q000494:pharmacology; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D015966:Gene Expression Regulation, Fungal; D018841:HSP90 Heat-Shock Proteins / Q000235:genetics* / Q000378:metabolism; D018613:Microscopy, Confocal; D008855:Microscopy, Electron, Scanning
chemical_list: D000935:Antifungal Agents; D001393:Azoles; D054714:Echinocandins; D005656:Fungal Proteins; D018841:HSP90 Heat-Shock Proteins; D015725:Fluconazole; D019703:Calcineurin