title: Functional validation of the genetic polymorphisms of human ATP-binding cassette (ABC) transporter ABCG2: identification of alleles that are defective in porphyrin transport.
abstract: The ATP-binding cassette (ABC) transporter ABCG2 has been implicated to play a significant role in the response of patients to medication and/or the risk of diseases. To clarify the possible physiological or pathological relevance of ABCG2 polymorphisms, we have functionally validated single nucleotide polymorphisms (SNP) of ABCG2. In the present study, based on the currently available data on SNPs and acquired mutations, we have created a total of 18 variant forms of ABCG2 (V12M, G51C, Q126stop, Q141K, T153M, Q166E, I206L, F208S, S248P, E334stop, F431L, S441N, R482G, R482T, F489L, F571I, N590Y, and D620N) by site-directed mutagenesis and expressed them in insect cells. Because porphyrins are considered to be endogenous substrates for ABCG2, we have investigated the porphyrin transport activity of those variant forms in vitro. We herein provide evidence that the variants Q126stop, F208S, S248P, E334stop, and S441N are defective in porphyrin transport, whereas F489L exhibited impaired transport, approximately 10% of the activity observed for the wild type. Furthermore, Flp-In-293 cells expressing those variants were photosensitive. Thus, among those genetic polymorphisms of ABCG2, at least the hitherto validated alleles of Q126stop, S441N, and F489L are suggested to be of clinical importance related to the potential risk of porphyria.
authors.affiliation: Department of Biomolecular Engineering, Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, 4259-B-60 Nagatsuta, Midori-ku, Yokohama 226-8501, Japan.
authors.forename: Ai
authors.initials: A
authors.lastname: Tamura
authors.forename: Masato
authors.initials: M
authors.lastname: Watanabe
authors.forename: Hikaru
authors.initials: H
authors.lastname: Saito
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Nakagawa
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Kamachi
authors.forename: Ichiro
authors.initials: I
authors.lastname: Okura
authors.forename: Toshihisa
authors.initials: T
authors.lastname: Ishikawa
mesh_terms: D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters / Q000235:genetics / Q000502:physiology*; D000255:Adenosine Triphosphate / Q000494:pharmacology; D000483:Alleles; D000818:Animals; D001692:Biological Transport / Q000187:drug effects / Q000502:physiology; D002166:Camptothecin / Q000031:analogs & derivatives / Q000494:pharmacology; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects / Q000235:genetics / Q000528:radiation effects; D002734:Chlorophyll / Q000031:analogs & derivatives / Q000494:pharmacology; D003630:Daunorubicin / Q000494:pharmacology; D004317:Doxorubicin / Q000494:pharmacology; D004351:Drug Resistance / Q000235:genetics; D006415:Hematoporphyrins / Q000378:metabolism; D006801:Humans; D000077146:Irinotecan; D007700:Kinetics; D008727:Methotrexate / Q000378:metabolism; D008942:Mitoxantrone / Q000494:pharmacology; D050505:Mutant Proteins / Q000235:genetics / Q000502:physiology; D009154:Mutation / Q000235:genetics; D009363:Neoplasm Proteins / Q000235:genetics / Q000502:physiology*; D020641:Polymorphism, Single Nucleotide / Q000235:genetics*; D011166:Porphyrins / Q000378:metabolism*; D018411:Spodoptera; D014162:Transfection
chemical_list: C116614:ABCG2 protein, human; D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters; D006415:Hematoporphyrins; D050505:Mutant Proteins; D009363:Neoplasm Proteins; D011166:Porphyrins; D002734:Chlorophyll; D000077146:Irinotecan; D004317:Doxorubicin; D000255:Adenosine Triphosphate; D008942:Mitoxantrone; C032623:pheophorbide a; D002166:Camptothecin; D008727:Methotrexate; D003630:Daunorubicin