C14DM Ablation Leads to Reduced Tolerance to Plasma Membrane Stress and Increased Drug Sensitivity in Leishmania major

Sterol biosynthesis is crucial for the function of biological membranes and an important target for anti-protozoan/anti-fungal drugs. In the trypanosomatid parasite Leishmania major, deletion of sterol C14-demethylase (C14DM) results in hypersensitivity to heat, increased plasma membrane fluidity, profound mitochondrial dysfunctions, and reduced virulence in mice. In this study, we show that C14DM-null mutants are defective in their tolerance to membrane disrupting agents and osmotic stress and their ability to form autophagosomes. In addition, C14DM-null mutants exhibit heightened sensitivity to anti-trypanosomatid drugs including antimony, ethidium bromide and pentamidine. Combination of itraconazole (a C14DM antagonist) and pentamidine synergistically inhibit the growth of Leishmania parasites. These findings reveal new insight into the roles of sterol synthesis in protozoan pathogens and highlight the potential of using drug combinations to achieve better treatment outcome.