title: Impaired NFKBIE gene function decreases cellular uptake of methotrexate by down-regulating SLC19A1 expression in a human rheumatoid arthritis cell line.
abstract: OBJECTIVE
  A non-synonymous single nucleotide polymorphism (nsSNP, rs2233434, Val194Ala) in the NFKBIE (nuclear factor of kappa light polypeptide gene enhancer in B-cells inhibitor, epsilon) gene is known to be a rheumatoid arthritis (RA) susceptibility polymorphism in the Japanese RA population and could be closely associated with nuclear factor kappaB (NF-κB) activity. Inflammation caused by RA is sometimes associated with changes in expression levels of MTX (methotrexate) pathway-related genes. It is of interest to examine whether the NFKBIE gene had any influences on the mode of MTX action.
  
  
  METHODS
  Both knockdown of NFKBIE gene expression and overexpression of wild-type NFKBIE and Val194Ala mutation were performed. A transfected human RA synovial cell line was cultured and then gene expressions in the MTX pathway were measured. In addition, we measured the uptake and efflux of MTX derivatives under the NFKBIE knockdown condition.
  
  
  RESULTS
  Knockdown of NFKBIE reduced the mRNA for SLC19A1, a main MTX membrane transporter, and the intracellular accumulations of MTX derivatives. Moreover, our experiments also confirmed that overexpression of Val194Ala mutant NFKBIE decreased the SLC19A1 mRNA when compared to that of wild-type NFKBIE.
  
  
  CONCLUSIONS
  We suggest that the impairment of NFKBIE gene function can reduce the uptake of MTX into cells, suggesting that the gene is an important factor for the RA outcome.
authors.affiliation: a Department of Physiology , Tokyo Women's Medical University School of Medicine , Tokyo , Japan .|b Institute of Rheumatology, Tokyo Women's Medical University , Tokyo , Japan .
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Imamura
authors.affiliation: a Department of Physiology , Tokyo Women's Medical University School of Medicine , Tokyo , Japan .
authors.forename: Sawako
authors.initials: S
authors.lastname: Yoshina
authors.affiliation: b Institute of Rheumatology, Tokyo Women's Medical University , Tokyo , Japan .
authors.forename: Katsunori
authors.initials: K
authors.lastname: Ikari
authors.affiliation: c Discovery Research III, Research and Development, Kissei Pharmaceutical Company , Nagano , Japan , and.
authors.forename: Keiji
authors.initials: K
authors.lastname: Miyazawa
authors.affiliation: b Institute of Rheumatology, Tokyo Women's Medical University , Tokyo , Japan .
authors.forename: Shigeki
authors.initials: S
authors.lastname: Momohara
authors.affiliation: a Department of Physiology , Tokyo Women's Medical University School of Medicine , Tokyo , Japan .|d Tokyo Women's Medical University Institute for Integrated Medical Sciences , Tokyo , Japan.
authors.forename: Shohei
authors.initials: S
authors.lastname: Mitani
mesh_terms: D001172:Arthritis, Rheumatoid / Q000188:drug therapy / Q000235:genetics* / Q000378:metabolism; D015415:Biomarkers; D002460:Cell Line; D015536:Down-Regulation; D005260:Female; D006801:Humans; D020672:I-kappa B Proteins / Q000235:genetics* / Q000378:metabolism; D008297:Male; D008727:Methotrexate / Q000494:pharmacology* / Q000627:therapeutic use; D016328:NF-kappa B / Q000378:metabolism; D020641:Polymorphism, Single Nucleotide; D011518:Proto-Oncogene Proteins / Q000235:genetics* / Q000378:metabolism; D058978:Reduced Folate Carrier Protein / Q000235:genetics* / Q000378:metabolism; D013583:Synovial Membrane / Q000166:cytology / Q000187:drug effects / Q000378:metabolism
chemical_list: D015415:Biomarkers; D020672:I-kappa B Proteins; D016328:NF-kappa B; C105627:NFKBIE protein, human; D011518:Proto-Oncogene Proteins; D058978:Reduced Folate Carrier Protein; C548699:SLC19A1 protein, human; D008727:Methotrexate
keywords: MH7A; Methotrexate; NFKBIE; Rheumatoid arthritis; SLC19A1