K143R Amino Acid Substitution in 14-α-Demethylase (Erg11p) Changes Plasma Membrane and Cell Wall Structure of Candida albicans

Abstract

The opportunistic pathogen Candida albicans is responsible for life-threating infections in immunocompromised individuals. Azoles and polyenes are two of the most commonly used antifungals and target the ergosterol biosynthesis pathway or ergosterol itself. A limited number of clinically employed antifungals correspond to the development of resistance mechanisms. One resistance mechanism observed in clinical isolates of azole-resistant C. albicans is the introduction of point mutations in the ERG11 gene, which encodes a key enzyme (lanosterol 14-α-demethylase) on the ergosterol biosynthesis pathway. Here, we demonstrate that a point mutation K143R in ERG11 (C. albicans ERG11K143R/K143R) contributes not only to azole resistance, but causes increased gene expression. Overexpression of ERG11 results in increased ergosterol content and a significant reduction in plasma membrane fluidity. Simultaneously, the same point mutation caused cell wall remodeling. This could be facilitated by the unmasking of chitin and β-glucan on the fungal cell surface, which can lead to recognition of the highly immunogenic β-glucan, triggering a stronger immunological reaction. For the first time, we report that a frequently occurring azole-resistance strategy makes C. albicans less susceptible to azole treatment while, at the same time, affects its cell wall architecture, potentially leading to exposure of the pathogen to a more effective host immune response.

Alterations in the Level of Ergosterol in Candida albicans’ Plasma Membrane Correspond with Changes in Virulence and Result in Triggering Diversed Inflammatory Response

“…The aim of this study was to investigate whether changes in the CW composition of C. albicans KS058 ( erg11∆ / ∆ ) and 10C1B1I1 ( ERG11 K143R / K143R ) mutants [ 28 ] correlate with altered cell surface hydrophobicity (CSH) and formation of biofilm. The results of CSH and biofilm assay are presented in Figure 1 .…”

“…We previously reported that both point mutation ( K143R ) in the ERG11 gene (in C. albicans 10C1B1I1 strain) or deletion of this gene (in C. albicans KS058 strain) corresponds with changes in the plasma membrane (PM) and CW composition of C. albicans mutants [ 28 ]. CW remodeling can impact both virulence of C. albicans and the immune response.…”

The Transcription Factor CsAtf1 Negatively Regulates the Cytochrome P450 Gene CsCyp51G1 to Increase Fludioxonil Sensitivity in Colletotrichum siamense

“…Studies have shown that the expression levels of HOG pathway members and CYP51s can affect the cellular ergosterol content. For example, in Cryptococcus neoformans , the Δ hog1 (MAPK) and Δ ssk1 (MAPKKK) mutants were found to generate significantly higher levels of cellular ergosterol than the WT [ 62 ], Δ Erg11B of A. fumigatus exhibited significantly reduced ergosterol content [ 63 ], and overexpression of Erg11 in Candida albicans elevated the ergosterol content [ 64 ]. Our studies showed that the HOG pathway and the transcription factors CsAtf1 and CsCyp51G1 are involved in fludioxonil sensitivity regulation in C. siamense , which prompted us to suggest a relevance between fludioxonil sensitivity and ergosterol biosynthesis.…”

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

“…PMs were obtained as previously described [ 32 ]. Briefly, C. albicans CAF2-1 and KS028 cells were harvested (3 min, 6000 rpm) after 8, 14, or 24 h of culture (equal A 600 = 40 for all used strains) and lysis solution was added to the cells (1 M sorbitol, 0.1 M EDTA, 1% BME, 3 mg/mL zymolyase).…”