Arachidonic acid is a potential inhibitor of Abc1 transporter of Candida krusei

With innate resistance to fluconazole (FLC) and rapid acquired resistance to other antifungal drugs, Candida krusei represents a potential multidrug-resistant pathogen. The mechanism of intrinsic FLC resistance in this yeast has been chiefly attributed to decreased susceptibility of FLC target, lanosterol 14α-demethylase (Erg11p), however, the role of efflux pump transporters remains controversial, and requires further investigation. Furthermore, although the overexpression of these transporters, including ATP-binding cassette 1 protein (Abc1p), results in multidrug-resistance phenotype, their inhibitors are limited. More so, there is currently no class of antifungal that specifically targets these transporters. Polyunsaturated fatty acids (PUFAs), including arachidonic acid (AA), which are known disruptors of the cellular membranes might function well as effective efflux pump inhibitors; however, this needs to be investigated. Hence, this study attempted to examine the influence of AA (with or without FLC) on the expression and activity of a representative ABC transporter, Abc1p, in C. krusei. This was carried out by exposing C. krusei biofilms to varying concentrations of AA alone or in combination FLC, and determining Abc1p expression and function using western blot analysis and Rhodamine 6G efflux assay, respectively. Our results demonstrate that Abc1p is overexpressed following exposure to FLC alone, but not in any treatments with AA. Furthermore, Abc1p exhibited increased functionality in the presence of FLC; however, this was severely diminished upon exposure to 1 mM AA, either alone or in combination with FLC. These findings demonstrate AA as a potential inhibitor of Abc1p expression, and subsequent activity. However, further research is necessary to fully delineate how AA influences this transporter.