TY - JOUR T1 - ABCG2 (Breast Cancer Resistance Protein/Mitoxantrone Resistance-Associated Protein) ATPase Assay: A Useful Tool to Detect Drug-Transporter Interactions JF - Drug Metabolism and Disposition JO - Drug Metab Dispos SP - 1533 LP - 1542 DO - 10.1124/dmd.106.014605 VL - 35 IS - 9 AU - Hristos Glavinas AU - Emese Kis AU - Ákos Pál AU - Rita Kovács AU - Márton Jani AU - Erika Vági AU - Éva Molnár AU - Száva Bánsághi AU - Zoltán Kele AU - Tamás Janáky AU - György Báthori AU - Oliver von Richter AU - Gerrit-Jan Koomen AU - Péter Krajcsi Y1 - 2007/09/01 UR - http://dmd.aspetjournals.org/content/35/9/1533.abstract N2 - The ATPase assay using membrane preparations from recombinant baculovirus-infected Spodoptera frugiperda ovarian (Sf9) cells is widely used to detect the interaction of compounds with different ATP-binding cassette transporters. However, Sf9 membrane preparations containing the wild-type ABCG2 transporter show an elevated baseline vanadate-sensitive ATPase activity, which cannot be further stimulated by substrates of ABCG2. Therefore, this assay system cannot be used for the detection of ABCG2 substrates. To overcome this difficulty we 1) purified membranes from a selected human cell line expressing wild-type ABCG2, and 2) inhibited the baseline ATPase activity with different inhibitors. In our modified assay, ABCG2 substrates were able to stimulate the baseline ATPase activity of ABCG2 expressed in membranes of human cells. Furthermore, using the specific ABCG2 inhibitors Ko143 or Ko134 allowed us to suppress the baseline vanadate-sensitive ATPase activity. Substrates of ABCG2 could stimulate this suppressed baseline ATPase, resulting in a better signal-to-background ratio and a robust assay to detect substrates of the ABCG2 transporter. The ATPase assay and the direct vesicular transport measurements for estrone-3-sulfate were in good accordance. The American Society for Pharmacology and Experimental Therapeutics ER -