PKC signaling regulates drug resistance of the fungal pathogen Candida albicans via circuitry comprised of Mkc1, calcineurin, and Hsp90.
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Fungal pathogens exploit diverse mechanisms to survive exposure to antifungal drugs. This poses concern given the limited number of clinically useful antifungals and the growing population of immunocompromised individuals vulnerable to life-threatening fungal infection. To identify molecules that abrogate resistance to the most widely deployed class of antifungals, the azoles, we conducted a screen of 1,280 pharmacologically active compounds. Three out of seven hits that abolished azole resistance of a resistant mutant of the model yeast Saccharomyces cerevisiae and a clinical isolate of the leading human fungal pathogen Candida albicans were inhibitors of protein kinase C (PKC), which regulates cell wall integrity during growth, morphogenesis, and response to cell wall stress. Pharmacological or genetic impairment of Pkc1 conferred hypersensitivity to multiple drugs that target synthesis of the key cell membrane sterol ergosterol, including azoles, allylamines, and morpholines. Pkc1 enabled survival of cell membrane stress at least in part via the mitogen activated protein kinase (MAPK) cascade in both species, though through distinct downstream effectors. Strikingly, inhibition of Pkc1 phenocopied inhibition of the molecular chaperone Hsp90 or its client protein calcineurin. PKC signaling was required for calcineurin activation in response to drug exposure in S. cerevisiae. In contrast, Pkc1 and calcineurin independently regulate drug resistance via a common target in C. albicans. We identified an additional level of regulatory control in the C. albicans circuitry linking PKC signaling, Hsp90, and calcineurin as genetic reduction of Hsp90 led to depletion of the terminal MAPK, Mkc1. Deletion of C. albicans PKC1 rendered fungistatic ergosterol biosynthesis inhibitors fungicidal and attenuated virulence in a murine model of systemic candidiasis. This work establishes a new role for PKC signaling in drug resistance, novel circuitry through which Hsp90 regulates drug resistance, and that targeting stress response signaling provides a promising strategy for treating life-threatening fungal infections.
Drug Resistance, Fungal
HSP90 Heat-Shock Proteins
Microbial Sensitivity Tests
Mitogen-Activated Protein Kinases
Protein Kinase C
Reverse Transcriptase Polymerase Chain Reaction
Published Version (Please cite this version)10.1371/journal.ppat.1001069
Publication InfoBetancourt-Quiroz, M; Collins, C; Cowen, LE; Gunatilaka, AA; LaFayette, SL; Perfect, John Robert; ... Zaas, Aimee Kirsch (2010). PKC signaling regulates drug resistance of the fungal pathogen Candida albicans via circuitry comprised of Mkc1, calcineurin, and Hsp90. PLoS Pathog, 6(8). pp. e1001069. 10.1371/journal.ppat.1001069. Retrieved from http://hdl.handle.net/10161/4605.
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James B. Duke Professor of Medicine
Research in my laboratory focuses around several aspects of medical mycology. We are investigating antifungal agents (new and old) in animal models of candida and cryptococcal infections. We have examined clinical correlation of in vitro antifungal susceptibility testing and with in vivo outcome. Our basic science project examines the molecular pathogenesis of cryptococcal infections. We have developed a molecular foundation for C. neoformans, including transformation systems, gene disr
Associate Professor of Medicine
Medical education Genomic applications for diagnosis of infectious diseases Genomic applications for prediction of infectious diseases
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