Gastroenterology 1999 Dec;117(6):1380-5

Localization of the Wilson's disease protein in human liver

Schaefer M, Roelofsen H, Wolters H, Hofmann WJ, Muller M, Kuipers F, Stremmel W,
Vonk RJ

Abstract
BACKGROUND & AIMS: 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