Regulation of the rat liver sodium-dependent bile acid cotransporter gene by prolactin. Mediation of transcriptional activation by Stat5.
The intracellular mechanism(s) underlying the upregulation of the hepatic Na+/taurocholate cotransporting polypeptide (ntcp) by prolactin (PRL) are unknown. In this report, we demonstrate a time-dependent increase in nuclear translocation of phosphorylated liver Stat5 (a member of the ignal ransducers and ctivators of ranscription family) that correlated with suckling-induced increases in serum PRL levels. In electrophoretic mobility gel shift assays, nuclear Stat5 exhibited specific DNA-binding ability towards IFN-gamma-activated sequence (GAS)-like elements (GLEs; 5'TTC/A-PyNPu-G/TAA-3') located in the -937 to -904 bp region of the ntcp promoter. Transient cotransfections in HepG2 cells revealed that PRL inducibility (2.5-3-fold) required coexpression of the long form of the PRL receptor (PRLRL) and Stat5. Deletion analysis mapped the PRLinducible region to -1237 to -758 bp of the ntcp promoter. Linking this 0.5-kb region to a heterologous thymidine kinase (tk) promoter, or linking multimerized ntcp GLEs either upstream of the ntcp minimal promoter (-158 to +47 bp) or the heterologous promoter conferred dose-dependent PRL responsiveness. The short form of the PRL receptor failed to transactivate ntcp GLEs. These results indicate that PRL acts via the PRLRL to facilitate Stat5 binding to ntcp-GLEs and to transcriptionally regulate ntcp.
Ganguly
T C
TC
Graduate Center for Toxicology, University of Kentucky, Lexington, Kentucky 40536, USA.
O'Brien
M L
ML
Karpen
S J
SJ
Hyde
J F
JF
Suchy
F J
FJ
Vore
M
M
D000818:Animals; D000833:Animals, Suckling; D001665:Binding Sites; D002352:Carrier Proteins / Q000235:genetics*; D002467:Cell Nucleus / Q000378:metabolism; D004247:DNA / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects*; D007371:Interferon-gamma / Q000494:pharmacology; D007700:Kinetics; D008099:Liver / Q000378:metabolism*; D008894:Milk Proteins; D029363:Organic Anion Transporters, Sodium-Dependent; D010766:Phosphorylation; D019000:Phosphotyrosine / Q000378:metabolism; D011388:Prolactin / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D011981:Receptors, Prolactin / Q000235:genetics; D050799:STAT5 Transcription Factor; D012964:Sodium / Q000494:pharmacology*; D027981:Symporters; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism; D014162:Transfection
D002352:Carrier Proteins; D004268:DNA-Binding Proteins; D008894:Milk Proteins; D029363:Organic Anion Transporters, Sodium-Dependent; D011981:Receptors, Prolactin; D050799:STAT5 Transcription Factor; D027981:Symporters; D015534:Trans-Activators; C071908:sodium-bile acid cotransporter; D019000:Phosphotyrosine; D007371:Interferon-gamma; D011388:Prolactin; D004247:DNA; D012964:Sodium