The ABC transporter Pdr5p mediates the efflux of nonsteroidal ecdysone agonists in Saccharomyces cerevisiae

We have previously shown that the synthetic nonsteroidal ecdysone agonist t ebufenozide (RH-5992) is actively excluded by resistant cells of insects. T o identify the transporter that could be involved in the efflux of RH-5992, the role of three ATP binding cassette transporters, Pdr5p, Snq2p and Ycf1 p, has been studied using transporter-deletion mutants of yeast Saccharomyc es cerevisiae. PDR5 (pleiotropic drug resistance 5) deletion mutants (Delta pdr5 and Delta pdr5 Delta snq2) retained significantly higher levels of C- 14-radiolabeled RH-5992 within the cells when compared to wild-type strain or single deletion mutants of SNQ2 (Delta snq2) and YCF1 (Delta ycf1). Intr oduction of an expression vector containing the PDR5 gene into the PDR5 sin gle deletion mutant reversed the effect, resulting in the active exclusion of [C-14]RH-5992 from these cells as efficiently as the wild-type cells. Th ese results demonstrated that the ABC transporter Pdr5p but not Snq2p or Yc f1p was responsible for the active exclusion of [C-14]RH-5992 in yeast. Thi s exclusion was temperature-dependent and was blocked by the ATPase inhibit ors oligomycin and vanadate, indicating that the efflux was an active proce ss. The mutants with the PDR5 deletion can also selectively accumulate [C-1 4]RH-0345 and [C-14]RH-2485, but not [C-14]RH-5849, indicating that these t hree compounds share the same transporter Pdr5p for efflux.