Copper does not alter the intracellular distribution of ATP7B, a copper-transporting ATPase.
Wilson's disease is a genetic disorder characterized by the accumulation of copper in the body due to a defect of biliary copper excretion. However, the mechanism of biliary copper excretion has not been fully clarified. We examined the effect of copper on the intracellular localization of the Wilson disease gene product (ATP7B) and green fluorescent protein (GFP)-tagged ATP7B in a human hepatoma cell line (Huh7). The intracellular organelles were visualized by fluorescence microscopy. GFP-ATP7B colocalized with late endosome markers, but not with endoplasmic reticulum, Golgi, or lysosome markers in both the steady and copper-loaded states. ATP7B mainly localized at the perinuclear regions in both states. These results suggest that the main localization of ATP7B is in the late endosomes in both the steady and copper-loaded states. ATP7B seems to translocate copper from the cytosol to the late endosomal lumen, thus participating in biliary copper excretion via lysosomes.
Harada
M
M
Second Department of Medicine, Kurume University School of Medicine, Kurume, Japan. harada@med.kurume-u.ac.jp
Sakisaka
S
S
Kawaguchi
T
T
Kimura
R
R
Taniguchi
E
E
Koga
H
H
Hanada
S
S
Baba
S
S
Furuta
K
K
Kumashiro
R
R
Sugiyama
T
T
Sata
M
M
D000251:Adenosine Triphosphatases / Q000235:genetics / Q000378:metabolism*; D015703:Antigens, CD / Q000032:analysis; D001692:Biological Transport / Q000187:drug effects; D015415:Biomarkers; D006528:Carcinoma, Hepatocellular / Q000201:enzymology / Q000473:pathology; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D002402:Cathepsin D / Q000032:analysis; D027682:Cation Transport Proteins; D003300:Copper / Q000378:metabolism / Q000494:pharmacology*; D000073840:Copper-Transporting ATPases; D011992:Endosomes / Q000187:drug effects / Q000378:metabolism; D005455:Fluorescent Antibody Technique; D006527:Hepatolenticular Degeneration / Q000201:enzymology / Q000235:genetics; D006801:Humans; D051907:Lysosomal Membrane Proteins; D008247:Lysosomes / Q000187:drug effects / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000032:analysis; D018613:Microscopy, Confocal; D011419:Propidium; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D014162:Transfection; D014407:Tumor Cells, Cultured
D015703:Antigens, CD; D015415:Biomarkers; D002352:Carrier Proteins; D027682:Cation Transport Proteins; D051907:Lysosomal Membrane Proteins; D008562:Membrane Glycoproteins; D011993:Recombinant Fusion Proteins; D011419:Propidium; D003300:Copper; D002402:Cathepsin D; D000251:Adenosine Triphosphatases; C000612464:ATP7B protein, human; D000073840:Copper-Transporting ATPases