BIOCHEMICAL-CHARACTERIZATION OF THE WILSON DISEASE PROTEIN AND FUNCTIONAL EXPRESSION IN THE YEAST SACCHAROMYCES-CEREVISIAE

Wilson disease is a disorder of copper metabolism characterized by hep atic cirrhosis and neuronal degeneration due to inherited mutations in a gene encoding a putative copper-transporting P-type ATPase. Polyclo nal antisera generated against the amino terminus of the Wilson protei n detected a specific 165-kDa protein in HepG2 and CaCo cell lysates, Further analysis revealed that this protein is synthesized as a single -chain polypeptide and localized to the trans-Golgi network under stea dy state conditions. An increase in the copper concentration resulted in the rapid movement of this protein to a cytoplasmic vesicular compa rtment. This copper-specific cellular redistribution of the Wilson pro tein is a reversible process that occurs independent of a new protein synthesis. Expression of the wild-type but not mutant Wilson protein i n the ccc2 Delta strain of Saccharomyces cerevisiae restored copper in corporation into the multicopper oxidase Fet3p, providing direct evide nce of copper transport by the Wilson protein. Taken together these da ta reveal a remarkable evolutionary conservation in the cellular mecha nisms of copper metabolism and provide a unique model for the regulati on of copper transport into the secretory pathway of eucaryotic cells.