title: Functional defect of variants in the adenosine triphosphate-binding sites of ABCB4 and their rescue by the cystic fibrosis transmembrane conductance regulator potentiator, ivacaftor (VX-770).
abstract: ABCB4 (MDR3) is an adenosine triphosphate (ATP)-binding cassette (ABC) transporter expressed at the canalicular membrane of hepatocytes, where it mediates phosphatidylcholine (PC) secretion. Variations in the ABCB4 gene are responsible for several biliary diseases, including progressive familial intrahepatic cholestasis type 3 (PFIC3), a rare disease that can be lethal in the absence of liver transplantation. In this study, we investigated the effect and potential rescue of ABCB4 missense variations that reside in the highly conserved motifs of ABC transporters, involved in ATP binding. Five disease-causing variations in these motifs have been identified in ABCB4 (G535D, G536R, S1076C, S1176L, and G1178S), three of which are homologous to the gating mutations of cystic fibrosis transmembrane conductance regulator (CFTR or ABCC7; i.e., G551D, S1251N, and G1349D), that were previously shown to be function defective and corrected by ivacaftor (VX-770; Kalydeco), a clinically approved CFTR potentiator. Three-dimensional structural modeling predicted that all five ABCB4 variants would disrupt critical interactions in the binding of ATP and thereby impair ATP-induced nucleotide-binding domain dimerization and ABCB4 function. This prediction was confirmed by expression in cell models, which showed that the ABCB4 mutants were normally processed and targeted to the plasma membrane, whereas their PC secretion activity was dramatically decreased. As also hypothesized on the basis of molecular modeling, PC secretion activity of the mutants was rescued by the CFTR potentiator, ivacaftor (VX-770).
  
  
  
  Disease-causing variations in the ATP-binding sites of ABCB4 cause defects in PC secretion, which can be rescued by ivacaftor. These results provide the first experimental evidence that ivacaftor is a potential therapy for selected patients who harbor mutations in the ATP-binding sites of ABCB4. (Hepatology 2017;65:560-570).
authors.affiliation: Sorbonne Universités, UPMC Univ Paris 06, INSERM, UMR_S 938, Saint-Antoine Research Center, F-75012, Paris, France.
authors.forename: Jean-Louis
authors.initials: JL
authors.lastname: Delaunay
authors.affiliation: Sorbonne Universités, UPMC Univ Paris 06, INSERM, UMR_S 938, Saint-Antoine Research Center, F-75012, Paris, France.
authors.forename: Alix
authors.initials: A
authors.lastname: Bruneau
authors.affiliation: IMPMC, Sorbonne Universités, UPMC Univ Paris 06, UMR CNRS 7590, Museum National d'Histoire Naturelle, IRD UMR 206, IUC, Case 115, 4 Place Jussieu, 75005, Paris Cedex 05, France.
authors.forename: Brice
authors.initials: B
authors.lastname: Hoffmann
authors.affiliation: Sorbonne Universités, UPMC Univ Paris 06, INSERM, UMR_S 938, Saint-Antoine Research Center, F-75012, Paris, France.
authors.forename: Anne-Marie
authors.initials: AM
authors.lastname: Durand-Schneider
authors.affiliation: Sorbonne Universités, UPMC Univ Paris 06, INSERM, UMR_S 938, Saint-Antoine Research Center, F-75012, Paris, France.|Assistance Publique-Hôpitaux de Paris, Saint-Antoine Hospital, Reference Center for Rare Disease, Inflammatory Biliary Diseases & Hepatology Department, F-75012, Paris, France.
authors.forename: Véronique
authors.initials: V
authors.lastname: Barbu
authors.affiliation: Assistance Publique-Hôpitaux de Paris, Faculty of Medicine Paris Sud, CHU Bicêtre, Pediatric Hepatology & Pediatric Hepatic Transplant Department, Reference Center for Rare Pediatric Liver Diseases, F-94275, Le Kremlin Bicêtre, France.|Université Paris Sud, INSERM, UMR_S 1174, Hepatinov, Orsay, France.
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Jacquemin
authors.affiliation: Sorbonne Universités, UPMC Univ Paris 06, INSERM, UMR_S 938, Saint-Antoine Research Center, F-75012, Paris, France.
authors.forename: Michèle
authors.initials: M
authors.lastname: Maurice
authors.affiliation: Sorbonne Universités, UPMC Univ Paris 06, INSERM, UMR_S 938, Saint-Antoine Research Center, F-75012, Paris, France.|Assistance Publique-Hôpitaux de Paris, Saint-Antoine Hospital, Reference Center for Rare Disease, Inflammatory Biliary Diseases & Hepatology Department, F-75012, Paris, France.
authors.forename: Chantal
authors.initials: C
authors.lastname: Housset
authors.affiliation: IMPMC, Sorbonne Universités, UPMC Univ Paris 06, UMR CNRS 7590, Museum National d'Histoire Naturelle, IRD UMR 206, IUC, Case 115, 4 Place Jussieu, 75005, Paris Cedex 05, France.
authors.forename: Isabelle
authors.initials: I
authors.lastname: Callebaut
authors.affiliation: Sorbonne Universités, UPMC Univ Paris 06, INSERM, UMR_S 938, Saint-Antoine Research Center, F-75012, Paris, France.
authors.forename: Tounsia
authors.initials: T
authors.lastname: Aït-Slimane
mesh_terms: D018435:ATP Binding Cassette Transporter, Subfamily B / Q000235:genetics*; D000255:Adenosine Triphosphate / Q000235:genetics; D000293:Adolescent; D000627:Aminophenols / Q000494:pharmacology*; D001665:Binding Sites; D002478:Cells, Cultured; D002648:Child; D003550:Cystic Fibrosis / Q000235:genetics* / Q000473:pathology; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000235:genetics*; D005260:Female; D056945:Hep G2 Cells; D006801:Humans; D008297:Male; D016296:Mutagenesis / Q000187:drug effects*; D020125:Mutation, Missense / Q000235:genetics; D010713:Phosphatidylcholines / Q000378:metabolism; D015363:Quinolones / Q000494:pharmacology*; D012494:Sampling Studies; D014162:Transfection; D055815:Young Adult
chemical_list: D018435:ATP Binding Cassette Transporter, Subfamily B; D000627:Aminophenols; D010713:Phosphatidylcholines; D015363:Quinolones; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; C545203:ivacaftor; D000255:Adenosine Triphosphate; C095122:multidrug resistance protein 3