Arsenic Trioxide Uptake by Hexose Permeases in Saccharomyces cerevisiae

Abstract

Arsenic trioxide is a toxic metalloid and carcinogen that is also used as an anticancer drug, and for this reason it is important to identify the routes of arsenite uptake by cells. In this study the ability of hexose transporters to facilitate arsenic trioxide uptake in Saccharomyces cerevisiae was examined. In the absence of glucose, strains with disruption of the arsenite efflux gene ACR3 accumulated high levels of 73As(OH)3. The addition of glucose inhibited uptake by ∼80%. Disruption of FPS1, the aquaglyceroporin gene, reduced glucose-independent uptake by only about 25%, and the residual uptake was nearly completely inhibited by hexoses, including glucose, galactose, mannose, and fructose but not pentoses or disaccharides. A strain lacking FPS1, ACR3, and all genes for hexose permeases except for HXT3, HXT6, HXT7, and GAL2 exhibited hexose-inhibitable 73As(OH) 3 uptake, whereas a strain lacking all 18 hexose transport-related genes (HXT1 to HXT17 and GAL2), FPS1 and ACR3, exhibited <10% of wild type 73As(OH)3 transport. When HXT1, HXT3, HXT4, HXT5, HXT7, or HXT9 was individually expressed in that strain, hexose-inhibitable 73As(OH)3 uptake was restored. In addition, the transport of [14C]glucose was inhibited by As(OH)3. These results clearly demonstrate that hexose permeases catalyze the majority of the transport of the trivalent metalloid arsenic trioxide.