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Adenosine triphosphate-dependent copper transport in human liver
M Dijkstra1, G J van den Berg, H Wolters
1Department of Pediatrics, Groningen Institute for Drug Studies, University Hospital Groningen, The Netherlands.
Journal of Hepatology
|July 1, 1996
Summary
This study reveals an ATP-dependent copper transport system in human liver cells, primarily located on the canalicular membrane. This finding is crucial for understanding copper metabolism and Wilson disease.
Area of Science:
- Hepatology
- Cell Biology
- Biochemistry
Background:
- Wilson disease gene cloning identified a P-type ATPase mediating hepatic copper transport.
- The precise location of this copper-transporting protein within hepatocytes was previously unknown.
- Potential locations included intracellular membranes (endoplasmic reticulum, lysosomes) or the bile canalicular membrane.
Purpose of the Study:
- To characterize and localize ATP-dependent copper transport in human liver.
- To investigate the role of specific membrane domains in hepatic copper uptake.
Main Methods:
- Investigated copper transport in isolated human liver plasma membrane vesicles.
- Utilized vesicles enriched in basolateral (blLPM), mixed (XLPM), and canalicular (cLPM) domains.
- Measured radiolabeled copper (64Cu) uptake in the presence of ATP and an ATP-regenerating system.
Main Results:
- ATP-dependent copper uptake was significantly stimulated in cLPM vesicles compared to blLPM and XLPM.
- Uptake rates correlated with canalicular membrane markers (leucine aminopeptidase activity).
- Kinetic analysis revealed specific Km and Vmax values for ATP-dependent copper transport.
Conclusions:
- Biochemical evidence supports an ATP-dependent copper transport system in human liver.
- This system, termed cCOP, is predominantly localized to the canalicular domain of the hepatocytic plasma membrane.