Localization of the Wilson's disease protein in human liver.
OBJECTIVE
Wilson's disease is an autosomal-recessive disorder of copper metabolism that results from the absence or dysfunction of a copper-transporting P-type adenosine triphosphatase that leads to impaired biliary copper excretion and disturbed holoceruloplasmin synthesis. To gain further insight into the role of the Wilson's disease protein in hepatic copper handling, its localization in human liver was investigated.


METHODS
By use of a specific antibody, localization of the Wilson's disease protein was studied in liver membrane fractions and liver sections by immunoblotting, immunohistochemistry, and double-label confocal scanning laser microscopy.


RESULTS
The 165-kilodalton protein, found by immunoblotting, was most abundant mainly in isolated plasma membrane fractions enriched in canalicular domains. Immunohistochemistry revealed intracellular punctuate staining of hepatocytes in certain regions of the liver, whereas a canalicular membrane staining pattern was observed in other regions. Double-labeling studies showed that in the latter regions the transporter is present mainly in vesicular structures just underneath the canalicular membrane that are positive for markers of the trans-Golgi network. A weak staining of the canalicular membrane, identified by staining for P-glycoprotein, was observed.


CONCLUSIONS
These results show that in human liver the Wilson's disease protein is predominantly present in trans-Golgi vesicles in the pericanalicular area, whereas relatively small amounts of the protein appear to localize to the canalicular membrane, consistent with a dual function of the protein in holoceruloplasmin synthesis and biliary copper excretion.
Schaefer
M
M
Groningen Institute for Drug Studies, Center for Liver, Digestive and Metabolic Diseases, University of Groningen, Groningen, The Netherlands.
Roelofsen
H
H
Wolters
H
H
Hofmann
W J
WJ
Müller
M
M
Kuipers
F
F
Stremmel
W
W
Vonk
R J
RJ
D000251:Adenosine Triphosphatases / Q000032:analysis* / Q000378:metabolism; D001659:Biliary Tract / Q000378:metabolism; D002352:Carrier Proteins / Q000032:analysis*; D027682:Cation Transport Proteins; D002462:Cell Membrane / Q000378:metabolism; D003300:Copper / Q000378:metabolism; D000073840:Copper-Transporting ATPases; D006527:Hepatolenticular Degeneration / Q000378:metabolism* / Q000473:pathology; D006801:Humans; D007150:Immunohistochemistry; D066298:In Vitro Techniques; D008099:Liver / Q000201:enzymology / Q000378:metabolism* / Q000473:pathology
D002352:Carrier Proteins; D027682:Cation Transport Proteins; D003300:Copper; D000251:Adenosine Triphosphatases; D000073840:Copper-Transporting ATPases