The Role of Ergosterol and Sphingolipids in the Localization and Activity of Candida albicans’ Multidrug Transporter Cdr1p and Plasma Membrane ATPase Pma1p

Abstract

Opportunistic pathogen <i>Candida albicans</i> causes systemic infections named candidiasis. Due to the increasing number of multi-drug resistant clinical isolates of <i>Candida</i> sp., currently employed antifungals (e.g., azoles) are insufficient for combating fungal infection. One of the resistance mechanisms toward azoles is increased expression of plasma membrane (PM) transporters (e.g., Cdr1p), and such an effect was observed in <i>C. albicans</i> clinical isolates. At the same time, it has been proven that a decrease in PMs sphingolipids (SLs) content correlates with altered sensitivity to azoles and diminished Cdr1p levels. This indicates an important role for SL in maintaining the properties of PM and gaining resistance to antifungal agents. Here, we prove using a novel spot variation fluorescence correlation spectroscopy (svFCS) technique that CaCdr1p localizes in detergent resistant microdomains (DRMs). Immunoblot analysis confirmed the localization of CaCdr1p in DRMs fraction in both the <i>C. albicans</i> WT and <i>erg11Δ/Δ</i> strains after 14 and 24 h of culture. We also show that the <i>C. albicans</i><i>erg11Δ/Δ</i> strain is more sensitive to the inhibitor of SLs synthesis; aureobasidin A (AbA). AbA treatment leads to a diminished amount of SLs in <i>C. albicans</i> WT and <i>erg11Δ/Δ</i> PM, while, for <i>C. albicans</i><i>erg11Δ/Δ</i>, the general levels of mannose-inositol-P-ceramide and inositol-P-ceramide are significantly lower than for the <i>C. albicans</i> WT strain. Simultaneously, the level of ergosterol in the <i>C. albicans</i> WT strain after adding of AbA remains unchanged, compared to the control conditions. Analysis of PM permeabilization revealed that treatment with AbA correlates with the disruption of PM integrity in <i>C. albicans</i><i>erg11Δ/Δ</i> but not in the <i>C. albicans</i> WT strain. Additionally, in the <i>C. albicans</i> WT strain, we observed lower activity of H⁺-ATPase, correlated with the delocalization of both CaCdr1p and CaPma1p.