title: A novel cDNA restores reduced folate carrier activity and methotrexate sensitivity to transport deficient cells.
abstract: Mammalian cells accumulate reduced folates and methotrexate, a folate antagonist, through the reduced-folate carrier (RFC) (Goldman, I.D., Lichtenstein, N.S., and Oliverio, V.T. (1968) J. Biol. Chem. 243, 5007-5017). This study describes the isolation and expression of a cDNA clone that restores RFC activity to human breast cancer cells defective in this transporter. The cDNA cancer cells defective in this transporter. The cDNA codes for a peptide (mRFC1) of 58 kDa, whose hydropathy plot, resembling those of mammalian sugar transporters, predicts that it may be a member of a superfamily of transporter genes. Transfection of methotrexate-resistant (MTXR) ZR-75-1 cells with an expression vector, pRFC1, that codes for this peptide restores their ability to accumulate methotrexate. Furthermore, transport of methotrexate into pRFC1-transfected cells is blocked by a 10-fold molar excess of the reduced folate, 5-formyltetrahydrofolic acid, but is unaffected by folic acid. The increase in methotrexate uptake that is observed in pRFC1-transfected MTXR ZR-75-1 cells reverses their resistance to this antitumor agent.
authors.affiliation: Medical Breast Cancer Section, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892.
authors.forename: K H
authors.initials: KH
authors.lastname: Dixon
authors.forename: B C
authors.initials: BC
authors.lastname: Lanpher
authors.forename: J
authors.initials: J
authors.lastname: Chiu
authors.forename: K
authors.initials: K
authors.lastname: Kelley
authors.forename: K H
authors.initials: KH
authors.lastname: Cowan
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001692:Biological Transport; D002352:Carrier Proteins / Q000235:genetics* / Q000378:metabolism; D018076:DNA, Complementary; D005492:Folic Acid / Q000378:metabolism*; D006801:Humans; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D008727:Methotrexate / Q000494:pharmacology*; D051379:Mice; D008969:Molecular Sequence Data; D058978:Reduced Folate Carrier Protein; D014162:Transfection; D014407:Tumor Cells, Cultured
chemical_list: D002352:Carrier Proteins; D018076:DNA, Complementary; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D058978:Reduced Folate Carrier Protein; C548699:SLC19A1 protein, human; C120043:SLC19A2 protein, human; C548700:Slc19a1 protein, mouse; C492292:Slc19a2 protein, mouse; D005492:Folic Acid; D008727:Methotrexate