PKC Signaling Regulates Drug Resistance of the Fungal Pathogen Candida albicans via Circuitry Comprised of Mkc1, Calcineurin, and Hsp90
Figure 6
Compromising PKC-MAPK signaling blocks calcineurin activation in response to ergosterol biosynthesis inhibitors in S. cerevisiae.
(A) Genetically compromising PKC-MAPK signaling by deleting SLT2 blocks calcineurin activation monitored with a 4XCDRE-lacZ reporter. β-galactosidase activity was measured after incubation in SD medium for 24 hours without any antifungal (U) or in the presence of ergosterol biosynthesis inhibitors at the following concentrations: 16 µg/mL fluconazole (FL), 1 µg/mL fenpropimorph (FN), or 25 µg/mL terbinafine (TB). While the WT strain exhibited increased β-galactosidase activity in response to ergosterol biosynthesis inhibitors, deletion of SLT2 or CNB1 (which encodes the regulatory subunit of calcineurin) blocked calcineurin activation. Data are means ± SD for triplicate samples and are representative of two independent experiments. (B) Pharmacological inhibition of PKC signaling with staurosporine (STS) blocks calcineurin activation monitored with a 4XCDRE-lacZ reporter. β-galactosidase activity was measured after incubation in SD medium (-) or in SD with 2.5 µg/mL STS. Cells were then treated with 32 µg/mL FL or were left untreated (U). Data are means ± SD for triplicate samples and are representative of two independent experiments. (C) Simplified schematic of how S. cerevisiae Pkc1 regulates responses to ergosterol biosynthesis inhibitors (EBIs) important for basal tolerance and resistance.