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 (Km: 24.6 μmol/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