title: Substitution of Trp1242 of TM17 alters substrate specificity of human multidrug resistance protein 3.
abstract: Multidrug resistance protein 3 (MRP3) is an ATP-dependent transporter of 17beta-estradiol 17beta(d-glucuronide) (E(2)17betaG), leukotriene C(4) (LTC(4)), methotrexate, and the bile salts taurocholate and glycocholate. In the present study, the role of a highly conserved Trp residue at position 1242 on MRP3 transport function was examined by expressing wild-type MRP3 and Ala-, Cys-, Phe-, Tyr-, and Pro-substituted mutants in human embryonic kidney 293T cells. Four MRP3-Trp(1242) mutants showed significantly increased E(2)17betaG uptake, whereas transport by the Pro mutant was undetectable. Similarly, the Pro mutant did not transport LTC(4). By comparison, LTC(4) transport by the Ala, Cys, Phe, and Tyr mutants was reduced by approximately 35%. The Ala, Cys, Phe, and Tyr mutants all showed greatly reduced methotrexate and leucovorin transport, except the Tyr mutant, which transported leucovorin at levels comparable with wild-type MRP3. In contrast, the MRP3-Trp(1242) substitutions did not significantly affect taurocholate transport or taurocholate and glycocholate inhibition of E(2)17betaG uptake. Thus Trp(1242) substitutions markedly alter the substrate specificity of MRP3 but leave bile salt binding and transport intact.
authors.affiliation: Department of Pharmacology and Toxicology and Cancer Research Laboratories, Queen's University, Kingston, Ontario, Canada K7L 3N6.
authors.forename: Curtis J
authors.initials: CJ
authors.lastname: Oleschuk
authors.forename: Roger G
authors.initials: RG
authors.lastname: Deeley
authors.forename: Susan P C
authors.initials: SP
authors.lastname: Cole
mesh_terms: D018435:ATP Binding Cassette Transporter, Subfamily B / Q000235:genetics*; D018528:ATP-Binding Cassette Transporters / Q000235:genetics*; D019943:Amino Acid Substitution; D002352:Carrier Proteins / Q000378:metabolism; D002460:Cell Line; D004958:Estradiol / Q000378:metabolism; D005822:Genetic Vectors; D006801:Humans; D006913:Hydroxysteroid Dehydrogenases; D007668:Kidney / Q000378:metabolism; D002955:Leucovorin / Q000378:metabolism; D017997:Leukotriene C4 / Q000378:metabolism; D008562:Membrane Glycoproteins; D008566:Membranes / Q000378:metabolism; D008727:Methotrexate / Q000378:metabolism; D016297:Mutagenesis, Site-Directed; D010446:Peptide Fragments / Q000235:genetics / Q000378:metabolism; D013379:Substrate Specificity; D013656:Taurocholic Acid / Q000378:metabolism; D014162:Transfection; D014364:Tryptophan / Q000235:genetics* / Q000378:metabolism; D045002:3-alpha-Hydroxysteroid Dehydrogenase (B-Specific)
chemical_list: D018435:ATP Binding Cassette Transporter, Subfamily B; D018528:ATP-Binding Cassette Transporters; D002352:Carrier Proteins; D004958:Estradiol; D006913:Hydroxysteroid Dehydrogenases; D002955:Leucovorin; D017997:Leukotriene C4; D008562:Membrane Glycoproteins; D008727:Methotrexate; D010446:Peptide Fragments; D013656:Taurocholic Acid; D014364:Tryptophan; C037643:bile acid binding proteins; C095122:multidrug resistance protein 3; C435496:AKR1C2 protein, human; D045002:3-alpha-Hydroxysteroid Dehydrogenase (B-Specific)