Membrane raft lipid constituents affect drug susceptibilities of Candida albicans

Abstract

By exploiting the biosynthetic pathways of raft lipid constituents, in this study we demonstrate that fluctuations in either sphingolipid or ergosterol levels result in increased drug sensitivity and morphological defects in Candida albicans cells. We show that any change in either ergosterol composition by conditionally disrupting ERG1 or in sphingolipid composition by homozygously disrupting its biosynthetic gene IPT1 leads to improper surface localization of a major ABC (ATP-binding cassette) drug efflux protein, Cdr1p. Results suggest that sterol/sphingolipid-rich membrane microdomains play an important role in positioning and functional maintenance of the integral efflux protein. The impaired ability of erg1/ipt1 mutant cells to efflux drugs mediated through Cdr1p appears to be the main cause of increased drug sensitivity of Candida cells.

Comparative Lipidomics of Azole Sensitive and Resistant Clinical Isolates of Candida albicans Reveals Unexpected Diversity in Molecular Lipid Imprints

“…For example, CaCdr1p shows selectivity towards membrane recruitment and prefers membrane raft micro-domains for its localization within plasma membrane [9]. It has already been demonstrated that there are close interactions between raft constituents such as ergosterol and sphingolipids (SLs), and disruption of these results in altered drug susceptibilities [10], [11]. Thus, any change in ergosterol composition by disruption of ERG genes, or change in SL composition by disruption of its biosynthetic genes leads to improper surface localization of CaCdr1p [9].…”

Candida albicans virulence and drug-resistance requires the O-acyltransferase Gup1p

“…An association between altered lipid-ordered domains and antifungal resistance has been described before [23,24,34,35]. Therefore, we examined the growth behaviour of several clones of Ca gup1Δ null mutant (3-5) in the presence of some common antifungals and compare them with wt.…”

“…It has been shown that subtle modifications on the membrane lipid composition (phospholipids and ergosterol), on its order (fluidity) and asymmetry could be important determinants of yeast cells susceptibility to antifungal drugs [23,24,34]. As already referred, Sc gup1Δ mutant presents a distorted lipidic plasma membrane constitution [54], and a changed stability/assembly of the sphingolipids-sterol ordered domains [19].…”

“…This may be the basis of the observed increased resistance of Ca gup1Δ null mutant strain to the EBIs, fluconazole, ketoconazole and clotrimazole, belonging to the class of azoles, and the morpholine, fenpropimorph. The azoles are antifungals commonly used to treat yeast infections [23,24,27,28,34]. Although in C. albicans the lipid biosynthesis pathways are not well documented, in S. cerevisiae these drugs operate on the biosynthesis of ergosterol at the C-14 demethylation stage [27,28], causing a combination of ergosterol depletion and the accumulation of lanosterol, along with other 14-methylated sterols [27,28].…”

“…Among various classes of lipids in C. albicans , membrane ergosterol is an important constituent, which is also the target of common antifungals like polyenes and azoles [23-25]. Therefore, the action of antifungals is affected by changes in the membrane lipid composition, as well as its order (fluidity) and asymmetry in general, and by ergosterol content/distribution in particular [19,23,24,26-28]. Our group has shown [19], that the Sc gup1Δ mutant displays a moderate sensitivity to sphingolipids biosynthesis inhibitors (SBIs), but a higher resistance to ergosterol biosynthesis inhibitors (EBIs), including azoles.…”