Fig. 8: Model of NPD827 mechanism of action.

(Left) Under normal physiological conditions, ergosterol and sphingolipids exist within the plasma membrane as lipid microdomains (yellow shadow). These microdomains harbor membrane-bound proteins, including drug-efflux pumps such as Cdr1. (Middle) NPD827 inserts into the plasma membrane and alters the biophysical properties of the membrane, reducing lateral mobility and impairing the function of membrane-bound proteins (i.e., Cdr1). Internalization of NPD827-associated membrane fragments disrupts the endomembrane system and induces vacuolar fragmentation, thereby perturbing lipid recycling throughout the cell. This disruption results in accumulation of toxic long-chain sphingoid bases, depletion of downstream sphingolipids, such as OH-Ceramide and Glucosylceramide, and induction of membrane-associated stress responses (i.e., lipid droplets, UPR, calcineurin-dependent stress responses). (Right) Due to impairment of drug-efflux by Cdr1, fluconazole accumulates within the cell further perturbing lipid homeostasis. The combination of effects ultimately halts growth of C. albicans in a synergistic manner.