Multidrug Transporters CaCdr1p and CaMdr1p of <i>Candida albicans</i> Display Different Lipid Specificities: both Ergosterol and Sphingolipids Are Essential for Targeting of CaCdr1p to Membrane Rafts

Abstract

In this study, we compared the effects of altered membrane lipid composition on the localization of two membrane drug transporters from different superfamilies of the pathogenic yeast Candida albicans. We demonstrated that in comparison to the major facilitator superfamily multidrug transporter CaMdr1p, ATP-binding cassette transporter CaCdr1p of C. albicans is preferentially localized within detergent-resistant membrane (DRM) microdomains called 'rafts.' Both CaCdr1p and CaMdr1p were overexpressed as green fluorescent protein (GFP)-tagged proteins in a heterologous host Saccharomyces cerevisiae, wherein either sphingolipid (Deltasur4 or Deltafen1 or Deltaipt1) or ergosterol (Deltaerg24 or Deltaerg6 or Deltaerg4) biosynthesis was compromised. CaCdr1p-GFP, when expressed in the above mutant backgrounds, was not correctly targeted to plasma membranes (PM), which also resulted in severely impaired drug resistance. In contrast, CaMdr1p-GFP displayed no sorting defect in the mutant background and remained properly surface localized and displayed no change in drug resistance. Our data clearly show that CaCdr1p is selectively recruited, over CaMdr1p, to the DRM microdomains of the yeast PM and that any imbalance in the raft lipid constituents results in missorting of CaCdr1p.