ADENOSINE TRIPHOSPHATE-DEPENDENT COPPER TRANSPORT IN ISOLATED RAT-LIVER PLASMA-MEMBRANES

G INTVELD, GJ VANDENBERG, M MULLER, F KUIPERS, RJ VONK

Research output: Contribution to journalComment/Letter to the editorAcademicpeer-review

48 Citations (Scopus)

Abstract

The process of hepatobiliary copper (Cu) secretion is still poorly understood: Cu secretion as a complex with glutathione and transport via a lysosomal pathway have been proposed. The recent cloning and sequencing of the gene for Wilson disease indicates that Cu transport in liver cells may be mediated by a Cu transporting P-type ATPase. Biochemical evidence for ATP-dependent Cu transport in mammalian systems, however, has not been reported so far. We have investigated Cu transport in rat liver plasma membrane vesicles enriched in canalicular or basolateral membranes in the presence and absence of ATP (4 mM) and an ATP-regenerating system. The presence of ATP clearly stimulated uptake of radiolabeled Cu ((CU)-C-64, 10 mu M) into canalicular plasma membrane vesicles and, to a lesser extent, also into basolateral plasma membrane vesicles. ATP-dependent Cu transport was dose-dependently inhibited by the P-type ATPase inhibitor vanadate, and showed saturation kinetics with an estimated K-m of 8.6 mu M and a V-max of 6.9 nmol/min/mg protein. ATP-stimulated Cu uptake was similar in canalicular membrane vesicles of normal Wistar rats and those of mutant GY rats, expressing a congenital defect in the activity of the ATP-dependent canalicular glutathione-conjugate transporter (cMOAT). These studies demonstrate the presence of an ATP-dependent Cu transporting system in isolated plasma membrane fractions of rat liver distinct from cMOAT.

Original languageEnglish
Pages (from-to)412-416
Number of pages5
JournalThe Journal of Clinical Investigation
Volume95
Issue number1
Publication statusPublished - Jan-1995

Keywords

  • COPPER
  • BILE SECRETION
  • P-TYPE ATPASE
  • VESICLE TRANSPORT
  • WILSON DISEASE
  • WILSON DISEASE GENE
  • MENKES DISEASE
  • CANDIDATE GENE
  • BILIARY-SECRETION
  • GLUTATHIONE
  • EXCRETION
  • ATPASE
  • TAUROCHOLATE
  • HEPATOCYTES
  • KINETICS

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