Azole resistance: Insights from Y132 substitutions inCandidasterol 14α-demethylase

Abstract

BackgroundAzole-resistantCandidainfections are on the rise. Resistant substitutions at Y132 in sterol 14α-demethylase, the key target of azole drugs, are frequent. However, it is unclear why only some Y132 substitutions are favoured or how they exert differential effects on different azoles.Materials and MethodsReported instances of Y132 substitutions were collected from the literature. Extensive molecular dynamics simulations of sterol 14α-demethylase bound to fluconazole or VT1161 (VT1) were performed, and the ligand-binding free energies were computed to quantify the effects of various Y132 substitutions on azole binding/interactions.ResultsThree azole-resistant substitutions, Y to C/F/H, were reported at residue position 132 in sterol 14α-demethylase. The Y132H was the most common substitution inC. albicans, while it was Y132F in other species. Ligand-binding free energies were -13.81 kcal/mol and -35.04 kcal/mol for fluconazole and VT1, respectively. There were differences in the ligand-binding free energies after substitutions compared to the wild type protein.ConclusionY132F and Y132H were the most frequent substitutions inCandidasterol 14α-demethylase. Far higher binding free energy of fluconazole in comparison with VT1 might partly explain its susceptibility to azole-resistant substitutions. The results give key insights into azole resistance, and antifungal drug discovery and optimization.

Azole resistance: Patterns of amino acid substitutions inCandidasterol 14α-demethylase

“…Further, it provides insightful patterns -for example, the number and abundance of substitutions in each Candida species. It may be noted that when there were multiple substitutions, they came from different clinical/experimental isolates and/or from different studies, and therefore provided an independent validation of such resistant substitutions/sites (Rao et al, 2024).…”

“…We searched the databases -PubMed/Medline, Scopus, Web of Science, and Google Scholarusing various combinations of the following keywords: "Candida", "azole resistance", "mutation/substitution", AND/OR "sterol 14α-demethylase", and sifted through the research papers to find the reports of experimentally confirmed azole-resistant substitutions in various clinical isolates (Rao et al, 2024). The review reports citing substitutions, if any, were traced to the original reports.…”

“…In fact, such substitutions are widely reported in the clinical isolates of Candida (Xiang et al, 2013) and other fungi (Zhang et al, 2019). For example, Y132F/H is one of the most common substitutions, and isolates might have multiple substitutions simultaneously (Flowers et al, 2015;Rao et al, 2024;Xiang et al, 2013). Substitutions, individually or in combination of two or more, strongly alter the azole MIC (Flowers et al, 2015;Warrilow et al, 2019).…”

“…For example, Y132F has a MIC of 64 to >128 µg/ml for fluconazole and 4 to >16 µg/ml for voriconazole, whereas K143R has a MIC of 64 to >128 µg/ml for fluconazole, but only 0.5 to 1 µg/ml to voriconazole (Healey et al, 2018). Similarly, different substitutions in same position might have different effects (Rao et al, 2024). For example, Y132F has a far higher MIC (>64 µg/ml) compared to Y132H (16 to 32 µg/ml) for fluconazole (Xiang et al, 2013).…”

“…Mechanistically, substitutions disrupt the interactions of ligands/azoles with the protein, and lower their binding efficacy (Rao et al, 2024). For example, many resistant (MIC: 16-256 µg/ml) clinical isolates of C. tropicalis were found to have two non-synonymous mutations A395T (Y132F) and C461T (S154F) in ERG11 gene (Paul et al, 2022).…”