Sphingolipid Homeostasis, Mitochondrial Activity, and PKA Signaling Drive an Azole-Tolerant State

Antifungal therapies frequently fail, resulting in persistent infections caused by the important opportunistic pathogen, Candida albicans, which is highly tolerant to azole drugs. Tolerance arises from a subpopulation of cells that survive prolonged drug exposure, yet the underlying mechanisms remain poorly defined. Here, transcription factor mutant library screens identified Mnl1 as a key repressor of tolerance. Loss of MNL1 elevated cAMP levels and activated the PKA pathway, linking Mnl1 to growth control and stress responses. Additionally, mnl1 cells exhibited altered sphingolipid composition, implicating Mnl1 in regulating membrane permeability, a key determinant of drug efflux and membrane integrity. Increased tolerance in mnl1 cells was also linked to increased mitochondrial function. Thus, Mnl1 regulates tolerance through coordinated control of sphingolipid metabolism, mitochondrial activity, and PKA signaling, highlighting that tolerant cells adopt a distinct physiological state primed to withstand antifungal stress.