A common Dubin-Johnson syndrome mutation impairs protein maturation and transport activity of MRP2 (ABCC2).
Absence of a functional multidrug resistance protein 2 (MRP2; symbol ABCC2) from the hepatocyte canalicular membrane is the molecular basis of Dubin- Johnson syndrome, an inherited disorder associated with conjugated hyperbilirubinemia in humans. In this work, we analyzed a relatively frequent Dubin-Johnson syndrome mutation that leads to an exchange of two hydrophobic amino acids, isoleucine 1173 to phenylalanine (MRP2I1173F), in a predicted extracellular loop of MRP2. HEK-293 cells stably transfected with MRP2I1173F cDNA synthesized a mutant protein that was mainly core-glycosylated, predominantly retained in the endoplasmic reticulum, and degraded by proteasomes. MRP2I1173F did not mediate ATP-dependent transport of leukotriene C(4) (LTC(4)) into vesicles from plasma membrane and endoplasmic reticulum preparations while normal MRP2 was functionally active. Human HepG2 cells were used to study localization of MRP2I1173F in a polarized cell system. Quantitative analysis showed that GFP-tagged MRP2I1173F was localized to the apical membrane in only 5% of transfected, polarized HepG2 cells compared with 80% for normal MRP2-GFP. Impaired protein maturation followed by proteasomal degradation of inactive MRP2I1173F explain the deficient hepatobiliary elimination observed in this group of Dubin-Johnson syndrome patients.
Keitel
Verena
V
Division of Tumor Biochemistry, Deutsches Krebsforschungszentrum, D-69120 Heidelberg, Germany.
Nies
Anne T
AT
Brom
Manuela
M
Hummel-Eisenbeiss
Johanna
J
Spring
Herbert
H
Keppler
Dietrich
D
D000255:Adenosine Triphosphate / Q000378:metabolism; D001692:Biological Transport / Q000235:genetics; D015153:Blotting, Western; D006528:Carcinoma, Hepatocellular; D002462:Cell Membrane / Q000737:chemistry / Q000378:metabolism; D003546:Cysteine Endopeptidases / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000737:chemistry / Q000378:metabolism; D004958:Estradiol / Q000031:analogs & derivatives* / Q000493:pharmacokinetics; D005455:Fluorescent Antibody Technique; D005965:Glucuronates / Q000493:pharmacokinetics; D006801:Humans; D006932:Hyperbilirubinemia / Q000235:genetics / Q000378:metabolism; D007566:Jaundice, Chronic Idiopathic / Q000235:genetics* / Q000378:metabolism*; D007668:Kidney / Q000166:cytology; D017997:Leukotriene C4 / Q000493:pharmacokinetics; D026901:Membrane Transport Proteins; D018613:Microscopy, Confocal; D000089762:Multidrug Resistance-Associated Protein 2; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000032:analysis / Q000235:genetics* / Q000378:metabolism*; D009097:Multienzyme Complexes / Q000037:antagonists & inhibitors / Q000378:metabolism; D046988:Proteasome Endopeptidase Complex; D014316:Tritium; D014407:Tumor Cells, Cultured
D000255:Adenosine Triphosphate; D003546:Cysteine Endopeptidases; D004958:Estradiol; D005965:Glucuronates; D017997:Leukotriene C4; D026901:Membrane Transport Proteins; D000089762:Multidrug Resistance-Associated Protein 2; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D009097:Multienzyme Complexes; D046988:Proteasome Endopeptidase Complex; D014316:Tritium; C409215:17-glucuronosylestradiol; C000715087:ABCC2 protein, human; C421109:multidrug resistance-associated protein 1