title: Stable expression and functional characterization of a Na+-taurocholate cotransporting green fluorescent protein in human hepatoblastoma HepG2 cells.
abstract: Sodium-dependent uptake of bile acids from blood is aliver-specific function which is mediated by theNa(+)-taurocholate cotransporting polypeptide(Ntcp). We report the stable expression of aNa(+)-taurocholate cotransporting green fluorescentfusion protein in the human hepatoblastoma cell lineHepG2, normally lacking Ntcp expression. Ntcp-EGFPassociated green fluorescence colocalized with Ntcpimmunofluorescence in the plasma membrane. Intransfected HepG2 cells, the fusion protein mediatedthe sodium-dependent uptake of the bile acidtaurocholate (K(m): 24.6 mumol/l) and of the anionicsteroids estrone-3-sulfate and dehydroepiandrosteronesulfate. We conclude that the Ntcp-EGFP fusion proteinfollows the sorting route of Ntcp, is functionallyidentical to Ntcp and could be used to monitor proteintrafficking in living HepG2 cells.
authors.affiliation: Divisions of Clinical Pharmacology/Toxicology, Department of Medicine, University Hospital, CH-8091, Zürich, Switzerland, kullak@kpt.unizh.ch.
authors.forename: G A
authors.initials: GA
authors.lastname: Kullak-Ublick
authors.forename: M G
authors.initials: MG
authors.lastname: Ismair
authors.forename: R
authors.initials: R
authors.lastname: Kubitz
authors.forename: M
authors.initials: M
authors.lastname: Schmitt
authors.forename: D
authors.initials: D
authors.lastname: Häussinger
authors.forename: B
authors.initials: B
authors.lastname: Stieger
authors.forename: B
authors.initials: B
authors.lastname: Hagenbuch
authors.forename: P J
authors.initials: PJ
authors.lastname: Meier
authors.forename: U
authors.initials: U
authors.lastname: Beuers
authors.forename: G
authors.initials: G
authors.lastname: Paumgartner