title: Differences in substrate specificity among glutathione conjugates (GS-X) pump family members: comparison between multidrug resistance-associated protein and a novel transporter expressed on a cisplatin-resistant cell line (KCP-4).
abstract: The substrate specificity of primary active transporters expressed on two kinds of human epidermoid KB-3-1 derived cell lines, C-A500 and KCP-4, was examined; the former expresses multidrug resistance-associated protein (MRP1), whereas the latter is resistant to cis-diamminedichloroplatinum (II) (cisplatin). Northern blot analysis indicated that neither P-glycoprotein, MRP1, MRP2 (canalicular multispecific organic anion transporter; cMOAT) nor MRP3 was overexpressed on KCP-4. Membrane vesicles isolated from C-A500 and KCP-4, but not from KB-3-1, exhibited the ATP-dependent uptake of glutathione conjugates (GS-X) such as leukotriene C4 and 2,4-dinitrophenyl-S-glutathione (DNP-SG), indicating the presence of GS-X pumps on these cells. The uptake of these GS-X by membrane vesicles from C-A500 was approximately twice that in the case of KCP-4. Kinetic analysis indicated that the Km and Vmax values for DNP-SG uptake were 2.56 and 1.43 microM, and 570 and 160 pmol/min/mg protein for C-A500 and KCP-4, respectively. In marked contrast, significant ATP-dependent uptake of glutathione-platinum complex was observed only in membrane vesicles from KCP-4, but not those from KB-3-1 and C-A500. The transport properties of estradiol-17beta-D-glucuronide (E(2)17betaG) were also different between the two cell lines. This was reflected in the findings that the ATP-dependent uptake of this conjugated metabolite in membrane vesicles from C-A500 (Km=2.33 microM, Vmax=34 pmol/min/mg protein) was much more extensive than that in the case of KCP-4 (Km=5.5 microM, Vmax=35 pmol/min/mg protein), and that comparable uptake was observed between KCP-4 and KB-3-1. Overall, a clear difference in substrate specificity among GS-X pump family members expressed on resistant tumor cells was demonstrated.
authors.affiliation: Graduate School of Pharmaceutical Sciences, The University of Tokyo.
authors.forename: K
authors.initials: K
authors.lastname: Ueda
authors.forename: H
authors.initials: H
authors.lastname: Suzuki
authors.forename: S
authors.initials: S
authors.lastname: Akiyama
authors.forename: Y
authors.initials: Y
authors.lastname: Sugiyama
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000235:genetics*; D000970:Antineoplastic Agents / Q000627:therapeutic use*; D002352:Carrier Proteins / Q000235:genetics*; D002945:Cisplatin / Q000627:therapeutic use; D018432:Drug Resistance, Multiple / Q000235:genetics*; D019008:Drug Resistance, Neoplasm / Q000235:genetics*; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D026901:Membrane Transport Proteins; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D005810:Multigene Family; D013379:Substrate Specificity; D014407:Tumor Cells, Cultured
chemical_list: D018528:ATP-Binding Cassette Transporters; D000970:Antineoplastic Agents; D002352:Carrier Proteins; D002945:Cisplatin; D026901:Membrane Transport Proteins; D027425:ATP-Binding Cassette, Sub-Family C Proteins; C086860:glutathione transporter