title: Transmembrane Domain Single-Nucleotide Polymorphisms Impair Expression and Transport Activity of ABC Transporter ABCG2.
abstract: OBJECTIVE
  To study the function and expression of nine naturally occurring single-nucleotide polymorphisms (G406R, F431L, S441N, P480L, F489L, M515R, L525R, A528T and T542A) that are predicted to reside in the transmembrane regions of the ABC transporter ABCG2.
  
  
  METHODS
  The transport activity of the variants was tested in inside-out membrane vesicles from Sf9 insect and human derived HEK293 cells overexpressing ABCG2. Lucifer Yellow and estrone sulfate were used as probe substrates of activity. The expression levels and cellular localization of the variants was compared to the wild-type ABCG2 by western blotting and immunofluorescence microscopy.
  
  
  RESULTS
  All studied variants of ABCG2 displayed markedly decreased transport in both Sf9-ABCG2 and HEK293-ABCG2 vesicles. Impaired transport could be explained for some variants by altered expression levels and cellular localization. Moreover, the destructive effect on transport activity of variants G406R, P480L, M515R and T542A is, to our knowledge, reported for the first time.
  
  
  CONCLUSIONS
  These results indicate that the transmembrane region of ABCG2 is sensitive to amino acid substitution and that patients harboring these ABCG2 variant forms could suffer from unexpected pharmacokinetic events of ABCG2 substrate drugs or have an increased risk for diseases such as gout where ABCG2 is implicated.
authors.affiliation: Centre for Drug Research, Division of Pharmaceutical Biosciences, Faculty of Pharmacy, University of Helsinki, Viikinkaari 5E, 00014, Helsinki, Finland.
authors.forename: Noora
authors.initials: N
authors.lastname: Sjöstedt
authors.affiliation: Department of Pharmacology and Toxicology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, The Netherlands.
authors.forename: Jeroen J M W
authors.initials: JJMW
authors.lastname: van den Heuvel
authors.affiliation: Department of Pharmacology and Toxicology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, The Netherlands.
authors.forename: Jan B
authors.initials: JB
authors.lastname: Koenderink
authors.affiliation: Centre for Drug Research, Division of Pharmaceutical Biosciences, Faculty of Pharmacy, University of Helsinki, Viikinkaari 5E, 00014, Helsinki, Finland. heidi.kidron@helsinki.fi.
authors.forename: Heidi
authors.initials: H
authors.lastname: Kidron
mesh_terms: D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2 / Q000235:genetics* / Q000378:metabolism*; D000818:Animals; D001692:Biological Transport; D014644:Genetic Variation; D057809:HEK293 Cells; D006801:Humans; D009154:Mutation; D009363:Neoplasm Proteins / Q000235:genetics* / Q000378:metabolism*; D020641:Polymorphism, Single Nucleotide; D061987:Sf9 Cells; D014162:Transfection
chemical_list: C116614:ABCG2 protein, human; D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D009363:Neoplasm Proteins
keywords: BCRP; SNP; genetic variant; interindividual variability; pharmacogenetics