title: Regulation of plasma membrane localization of the Na+-taurocholate cotransporting polypeptide (Ntcp) by hyperosmolarity and tauroursodeoxycholate.
abstract: In perfused rat liver, hepatocyte shrinkage induces a Fyn-dependent retrieval of the bile salt export pump (Bsep) and multidrug resistance-associated protein 2 (Mrp2) from the canalicular membrane (Cantore, M., Reinehr, R., Sommerfeld, A., Becker, M., and Häussinger, D. (2011) J. Biol. Chem. 286, 45014-45029) leading to cholestasis. However little is known about the effects of hyperosmolarity on short term regulation of the Na(+)-taurocholate cotransporting polypeptide (Ntcp), the major bile salt uptake system at the sinusoidal membrane of hepatocytes. The aim of this study was to analyze hyperosmotic Ntcp regulation and the underlying signaling events. Hyperosmolarity induced a significant retrieval of Ntcp from the basolateral membrane, which was accompanied by an activating phosphorylation of the Src kinases Fyn and Yes but not of c-Src. Hyperosmotic internalization of Ntcp was sensitive to SU6656 and PP-2, suggesting that Fyn mediates Ntcp retrieval from the basolateral membrane. Hyperosmotic internalization of Ntcp was also found in livers from wild-type mice but not in p47(phox) knock-out mice. Tauroursodeoxycholate (TUDC) and cAMP reversed hyperosmolarity-induced Fyn activation and triggered re-insertion of the hyperosmotically retrieved Ntcp into the membrane. This was associated with dephosphorylation of the Ntcp on serine residues. Insertion of Ntcp by TUDC was sensitive to the integrin inhibitory hexapeptide GRGDSP and inhibition of protein kinase A. TUDC also reversed the hyperosmolarity-induced retrieval of bile salt export pump from the canalicular membrane. These findings suggest a coordinated and oxidative stress- and Fyn-dependent retrieval of sinusoidal and canalicular bile salt transport systems from the corresponding membranes. Ntcp insertion was also identified as a novel target of β1-integrin-dependent TUDC action, which is frequently used in the treatment of cholestatic liver disease.
authors: From the Clinic for Gastroenterology, Hepatology and Infectious Diseases, Heinrich-Heine-University Düsseldorf, 40225 Düsseldorf, Germany.
authors: Annika
authors: A
authors: Sommerfeld
authors: From the Clinic for Gastroenterology, Hepatology and Infectious Diseases, Heinrich-Heine-University Düsseldorf, 40225 Düsseldorf, Germany.
authors: Patrick G K
authors: PG
authors: Mayer
authors: From the Clinic for Gastroenterology, Hepatology and Infectious Diseases, Heinrich-Heine-University Düsseldorf, 40225 Düsseldorf, Germany.
authors: Miriam
authors: M
authors: Cantore
authors: From the Clinic for Gastroenterology, Hepatology and Infectious Diseases, Heinrich-Heine-University Düsseldorf, 40225 Düsseldorf, Germany haeussin@uni-duesseldorf.de.
authors: Dieter
authors: D
authors: Häussinger
mesh_terms: D000818:Animals; D001647:Bile Acids and Salts / Q000737:chemistry; D002118:Calcium / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism*; D002478:Cells, Cultured; D002779:Cholestasis / Q000378:metabolism; D003720:Densitometry; D015971:Gene Expression Regulation, Enzymologic; D056945:Hep G2 Cells; D022781:Hepatocytes / Q000166:cytology; D006801:Humans; D019012:Integrin beta1 / Q000378:metabolism; D008099:Liver / Q000378:metabolism*; D008297:Male; D051379:Mice; D029363:Organic Anion Transporters, Sodium-Dependent / Q000378:metabolism*; D009994:Osmolar Concentration; D018384:Oxidative Stress; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism; D051076:Proto-Oncogene Proteins c-fyn / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D017382:Reactive Oxygen Species / Q000737:chemistry; D012694:Serine / Q000737:chemistry; D015398:Signal Transduction; D012964:Sodium / Q000737:chemistry; D027981:Symporters / Q000378:metabolism*; D013656:Taurocholic Acid / Q000737:chemistry
chemical_list: D001647:Bile Acids and Salts; D019012:Integrin beta1; D029363:Organic Anion Transporters, Sodium-Dependent; D017382:Reactive Oxygen Species; D027981:Symporters; C071908:sodium-bile acid cotransporter; D012694:Serine; D013656:Taurocholic Acid; D012964:Sodium; C494961:Fyn protein, rat; D051076:Proto-Oncogene Proteins c-fyn; D011493:Protein Kinase C; D002118:Calcium
keywords: Fyn; Ntcp; Src; bile acid; cyclic AMP (cAMP); integrin; protein kinase C (PKC); tauroursodeoxycholate; transporter retrieval