Levels of plasma membrane expression in progressive and benign mutations of the bile salt export pump (Bsep/Abcb11) correlate with severity of cholestatic diseases
- 1 November 2007
- journal article
- research article
- Published by American Physiological Society in American Journal of Physiology-Cell Physiology
- Vol. 293 (5), C1709-C1716
- https://doi.org/10.1152/ajpcell.00327.2007
Abstract
Human BSEP (ABCB11) mutations are the molecular basis for at least three clinical forms of liver disease, progressive familial intrahepatic cholestasis type 2 (PFIC2), benign recurrent intrahepatic cholestasis type 2 (BRIC2), and intrahepatic cholestasis of pregnancy (ICP). To better understand the pathobiology of these disease phenotypes, we hypothesized that different mutations may cause significant differences in protein defects. Therefore we compared the effect of two PFIC2 mutations (D482G, E297G) with two BRIC2 mutations (A570T and R1050C) and one ICP mutation (N591S) with regard to the subcellular localization, maturation, and function of the rat Bsep protein. Bile salt transport was retained in all but the E297G mutant. Mutant proteins were expressed at reduced levels on the plasma membrane of transfected HEK293 cells compared with wild-type (WT) Bsep in the following order: WT > N591S > R1050C ∼ A570T ∼ E297G >> D482G. Total cell protein and surface protein expression were reduced to the same extent, suggesting that trafficking of these mutants to the plasma membrane is not impaired. All Bsep mutants accumulate in perinuclear aggresome-like structures in the presence of the proteasome inhibitor MG-132, suggesting that mutations are associated with protein instability and ubiquitin-dependent degradation. Reduced temperature, sodium butyrate, and sodium 4-phenylbutyrate enhanced the expression of the mature and cell surface D482G protein in HEK293 cells. These results suggest that the clinical phenotypes of PFIC2, BRIC2, and ICP may directly correlate with the amount of mature protein that is expressed at the cell surface and that strategies to stabilize cell surface mutant protein may be therapeutic.Keywords
This publication has 32 references indexed in Scilit:
- Mutations and polymorphisms in the bile salt export pump and the multidrug resistance protein 3 associated with drug-induced liver injuryPharmacogenetics and Genomics, 2007
- Hepatocellular carcinoma in ten children under five years of age with bile salt export pump deficiencyHepatology, 2006
- Vectorial transport of unconjugated and conjugated bile salts by monolayers of LLC-PK1 cells doubly transfected with human NTCP and BSEP or with rat Ntcp and BsepAmerican Journal of Physiology-Gastrointestinal and Liver Physiology, 2006
- Benign Recurrent Intrahepatic Cholestasis Associated With Mutations of the Bile Salt Export PumpJournal of Clinical Gastroenterology, 2006
- Cytokine-dependent regulation of hepatic organic anion transporter gene transactivators in mouse liverAmerican Journal of Physiology-Gastrointestinal and Liver Physiology, 2005
- Impaired expression and function of the bile salt export pump due to three novel ABCB11 mutations in intrahepatic cholestasisJournal of Hepatology, 2005
- LPS-induced downregulation of MRP2 and BSEP in human liver is due to a posttranscriptional processAmerican Journal of Physiology-Gastrointestinal and Liver Physiology, 2004
- Intracellular Trafficking of Bile Salt Export Pump (ABCB11) in Polarized Hepatic Cells: Constitutive Cycling between the Canalicular Membrane and rab11-positive EndosomesMolecular Biology of the Cell, 2004
- Regulation of the Stability of P-Glycoprotein by UbiquitinationMolecular Pharmacology, 2004
- Degradation Process of Ligand-stimulated Platelet-derived Growth Factor β -Receptor Involves Ubiquitin-Proteasome Proteolytic PathwayOnline Journal of Public Health Informatics, 1995