RRC ID 61151
Author Nakai Y, Inoue K, Abe N, Hatakeyama M, Ohta KY, Otagiri M, Hayashi Y, Yuasa H.
Title Functional characterization of human proton-coupled folate transporter/heme carrier protein 1 heterologously expressed in mammalian cells as a folate transporter.
Journal J Pharmacol Exp Ther
Abstract The functional characteristics of human proton coupled folate transporter (hPCFT)/heme carrier protein (HCP) 1 were investigated. hPCFT/HCP1 expressed transiently in human embryonic kidney 293 cells mediated the transport of folate at an acidic extracellular pH of 5.5 in a manner independent of Na(+) and insensitive to membrane potential, but its transport activity was absent at near-neutral pH. Folate transport mediated by hPCFT/hHCP1 at pH 5.5 was saturable with a K(m) of 1.67 microM and extensively inhibited by reduced folates, such as folinate, 5-methyltetrahydrofolate, and methotrexate (MTX). Sulfobro-mophthalein and 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid were also found to be potent inhibitors of hPCFT/hHCP1, but hemin was found to exhibit only minimal inhibitory effect. When expressed stably as a protein fused with green fluorescent protein (GFP-hPCFT/HCP1) in MDCKII cells, GFP-hPCFT/HCP1 was mainly localized at the apical membrane, and the cellular accumulation of MTX was higher from the apical side than from the basal side. These functional features of hPCFT/HCP1 are consistent with those of the well characterized carrier-mediated folate transport system in the small intestine, suggesting that hPCFT/HCP1 is responsible for the intestinal absorption of folate and also MTX. We also found that sulfasalazine is a potent inhibitor of hPCFT/HCP1, which would interfere with the intestinal absorption of MTX when coadministered in therapy for rheumatoid arthritis as well as folate.
Volume 322(2)
Pages 469-76
Published 2007-8-1
DOI 10.1124/jpet.107.122606
PII jpet.107.122606
PMID 17475902
MeSH Animals Anti-Inflammatory Agents, Non-Steroidal / pharmacology Antirheumatic Agents / pharmacology Biological Transport, Active / drug effects Cell Line Cell Membrane / chemistry Cell Membrane / metabolism Diclofenac / pharmacology Dose-Response Relationship, Drug Folic Acid / analogs & derivatives Folic Acid / metabolism* Green Fluorescent Proteins / genetics Green Fluorescent Proteins / metabolism Humans Hydrogen-Ion Concentration Indomethacin / pharmacology Kinetics Membrane Transport Proteins / genetics Membrane Transport Proteins / metabolism Membrane Transport Proteins / physiology* Methotrexate / metabolism* Microscopy, Confocal Nigericin / pharmacology Proton-Coupled Folate Transporter Sulfasalazine / pharmacology Transfection
IF 3.615
DNA material pCI-neo-hPCFT (RDB18230)