title: The mechanism of carrier-mediated transport of folates in BeWo cells: the involvement of heme carrier protein 1 in placental folate transport.
abstract: The aim of this study was to elucidate the mechanism of folate transport in the placenta. A study of folate was carried out to determine which carriers transport folates in the human choriocarcinoma cell line BeWo, a model cell line for the placenta. We investigated the effects of buffer pH and various compounds on folate uptake. In the first part of the study, the expression levels of the mRNA of the folate receptor alpha (FRalpha), the reduced folate carrier (RFC), and heme carrier protein 1 (HCP1) were determined in BeWo cells by RT-PCR analysis. Folate uptake into BeWo cells was greater under an acidic buffer condition than under a neutral one. Structure analogs of folates inhibited folate uptake under all buffer pH conditions, but anion drugs (e.g., pravastatin) inhibited folate uptake only under an acidic buffer condition. Although thiamine pyrophosphate (TPP), a substrate of RFC, had no effect on folate uptake, hemin (a weak inhibitor of folate uptake via HCP1) decreased folate uptake to about 80% of the control level under an acidic buffer condition. Furthermore, kinetic analysis showed that hemin inhibited the low-affinity phase of folate uptake under an acidic buffer condition. We conclude that pH-dependent folate uptake in BeWo cells is mediated by at least two carriers. RFC is not involved in folate uptake, but FRalpha (high affinity phase) and HCP1 (low affinity phase) transport folate in BeWo cells.
authors.affiliation: Laboratory of Clinical Pharmaceutics and Therapeutics, Division of Pharmascience, Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo 060-0812, Japan.
authors.forename: Satoru
authors.initials: S
authors.lastname: Yasuda
authors.forename: Satoko
authors.initials: S
authors.lastname: Hasui
authors.forename: Masaki
authors.initials: M
authors.lastname: Kobayashi
authors.forename: Shirou
authors.initials: S
authors.lastname: Itagaki
authors.forename: Takeshi
authors.initials: T
authors.lastname: Hirano
authors.forename: Ken
authors.initials: K
authors.lastname: Iseki
mesh_terms: D001483:Base Sequence; D001692:Biological Transport; D002352:Carrier Proteins / Q000235:genetics; D045744:Cell Line, Tumor; D017931:DNA Primers; D005260:Female; D058973:Folate Receptors, GPI-Anchored; D005492:Folic Acid / Q000378:metabolism*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D026901:Membrane Transport Proteins / Q000502:physiology*; D010920:Placenta / Q000378:metabolism*; D017035:Pravastatin / Q000494:pharmacology; D058979:Proton-Coupled Folate Transporter; D012333:RNA, Messenger / Q000235:genetics; D011956:Receptors, Cell Surface / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013835:Thiamine Pyrophosphate / Q000494:pharmacology
chemical_list: D002352:Carrier Proteins; D017931:DNA Primers; D058973:Folate Receptors, GPI-Anchored; D026901:Membrane Transport Proteins; D058979:Proton-Coupled Folate Transporter; D012333:RNA, Messenger; D011956:Receptors, Cell Surface; C505058:SLC46A1 protein, human; D005492:Folic Acid; D017035:Pravastatin; D013835:Thiamine Pyrophosphate