Identification and characterization of the molecular interactions of persistent organic pollutants with the multidrug resistance transport protein ABCB1 (974.4)

Abstract

Multidrug resistance (MDR) transporters, from the ATP binding cassette (ABC) superfamily, are thought to act as determinants of chemical accumulation in cells. Despite a long history of research on the interactions of MDR proteins with pharmaceuticals, little is known about the molecular basis of their interactions with environmental compounds such as persistent organic pollutants (POPs). This research is urgently needed to further understanding of substrate recognition by the transporters and to test the hypothesis that pollutant persistence relates to predictable patterns of interaction with the major MDR transporter ABCB1. We use purified recombinant P‐glycoprotein (ABCB1) from mouse and yellowfin tuna to measure pollutant‐transporter interaction kinetics via ATPase stimulation and fluorophore knock‐off experiments. These kinetic will be compared to what is observed with ABCB1 overexpressed in whole cells. Previously analyzed data on “real‐world” pollutant levels in the cosmopolitan and widely consumed fish species of yellowfin tuna (Thunnus albacares) was used to guide the selection of persistent pollutants. The preliminary results of this study show that the majority of the selected persistent pollutants found in tuna are inhibitors of mouse ABCB1 efflux pump. Thereby, isomeric forms of the same pollutant can differ in their IC50 values up to an order of magnitude while reaching inhibition coefficients in the range of the model inhibitor cyclosporine A. These studies aim at determining the conservation of pollutant‐transporter interactions across marine and mammalian ABCB1 transporters. In addition, we want to investigate whether common structural features of ABC transporters and pollutants govern their interactions. These results will shed light on the question of how transporters can direct pollutant movement through the environment and will lead to new avenues for design of more potent pharmaceuticals and safer industrial chemicals. Grant Funding Source: Supported by NIH and the WAITT Foundation