BACKGROUND/AIMS: Progressive familial intrahepatic cholestasis type 2 (PFIC-2) patients have a defect in the hepatocanalicular bile salt secretion. The disease is caused by mutations in the bile salt export pump (BSEP). Ten different missense mutations have been described. In this study, we analysed the effect of the D482G PFIC-2 mutation on BSEP function. METHODS: Adenosine triphosphatase (ATPase) and taurocholate transport assays were performed with full-length mouse Bsep (mBsep) with and without the D482G mutation. The effect on expression and subcellular sorting was studied in HepG2 cells, stably expressing enhanced green fluorescent protein (EGFP)-tagged mBsep proteins. RESULTS: The D482G mutation did not significantly affect the taurocholate transport activity of mBsep, even though the bile salt-inducible ATPase activity of the mutant protein was slightly reduced. Protein expression and canalicular sorting were strongly affected by the D482G mutation. Mutant EGFP-mBsep protein was only partly glycosylated and detected in both the canalicular membrane and the cytoplasm. At 30 degrees C, the mutant mRNA and protein levels were strongly increased, and the protein was predominantly glycosylated and efficiently targeted to the canalicular membrane. CONCLUSIONS: These data suggest that PFIC-2 patients with the D482G mutation express a functional, but highly unstable, temperature-sensitive bile salt export pump.
BACKGROUND/AIMS: Progressive familial intrahepatic cholestasis type 2 (PFIC-2) patients have a defect in the hepatocanalicular bile salt secretion. The disease is caused by mutations in the bile salt export pump (BSEP). Ten different missense mutations have been described. In this study, we analysed the effect of the D482GPFIC-2 mutation on BSEP function. METHODS: Adenosine triphosphatase (ATPase) and taurocholate transport assays were performed with full-length mouseBsep (mBsep) with and without the D482G mutation. The effect on expression and subcellular sorting was studied in HepG2 cells, stably expressing enhanced green fluorescent protein (EGFP)-tagged mBsep proteins. RESULTS: The D482G mutation did not significantly affect the taurocholate transport activity of mBsep, even though the bile salt-inducible ATPase activity of the mutant protein was slightly reduced. Protein expression and canalicular sorting were strongly affected by the D482G mutation. Mutant EGFP-mBsep protein was only partly glycosylated and detected in both the canalicular membrane and the cytoplasm. At 30 degrees C, the mutant mRNA and protein levels were strongly increased, and the protein was predominantly glycosylated and efficiently targeted to the canalicular membrane. CONCLUSIONS: These data suggest that PFIC-2patients with the D482G mutation express a functional, but highly unstable, temperature-sensitive bile salt export pump.
Authors: Ludmila Pawlikowska; Sandra Strautnieks; Irena Jankowska; Piotr Czubkowski; Karan Emerick; Anthony Antoniou; Catherine Wanty; Bjorn Fischler; Emmanuel Jacquemin; Sami Wali; Samra Blanchard; Inge-Merete Nielsen; Billy Bourke; Shirley McQuaid; Florence Lacaille; Jane A Byrne; Albertien M van Eerde; Kaija-Leena Kolho; Leo Klomp; Roderick Houwen; Peter Bacchetti; Steven Lobritto; Vera Hupertz; Patricia McClean; Giorgina Mieli-Vergani; Benjamin Shneider; Antal Nemeth; Etienne Sokal; Nelson B Freimer; A S Knisely; Philip Rosenthal; Peter F Whitington; Joanna Pawlowska; Richard J Thompson; Laura N Bull Journal: J Hepatol Date: 2010-04-13 Impact factor: 25.083
Authors: Richard H Ho; Brenda F Leake; Dawn M Kilkenny; Henriette E Meyer Zu Schwabedissen; Hartmut Glaeser; Deanna L Kroetz; Richard B Kim Journal: Pharmacogenet Genomics Date: 2010-01 Impact factor: 2.089