LOCALIZATION OF THE WILSONS-DISEASE PROTEIN PRODUCT TO MITOCHONDRIA

Wilson's disease (WND) is an inherited disorder of copper homeostasis characterized by abnormal accumulation of copper in several tissues, p articularly in the liver, brain, and kidney. The disease-associated ge ne encodes a copper-transporting P-type ATPase, the WND protein, the s ubcellular location of which could be regulated by copper. We demonstr ate that the WND protein is present in cells in two forms, the 160-kDa and the 140-kDa products. The 160-kDa product was earlier shown to be targeted to trans-Golgi network The 140-kDa product identified herein is located in mitochondria as evidenced by the immunofluorescent stai ning of HepG2 cells with specific mitochondria markers and polyclonal antibody directed against the C terminus of the WND molecule. The mito chondrial location for the 140-kDa WND product was confirmed by membra ne fractionation and by analysis of purified human mitochondria. The a ntibody raised against a repetitive sequence in the N-terminal portion of the WND molecule detects an additional 16-kDa protein, suggesting that the 140-kDa product was formed after proteolytic cleavage of the full-length WND protein at the N terminus. Thus, the WND protein is a P-type ATPase with an unusual subcellular localization. The mitochondr ia targeting of the WND protein suggests its important role for copper -dependent processes taking place in this organelle.