Transport and Intracellular Distribution of Copper in A Human Hepatoblastoma Cell Line, Hepg2

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Abstract
The uptake of radiocopper by HepG2 cells is a saturable, temperature–dependent and cellular energy–independent process with a Vmax of 7.1 ± 0.2 pmoles min-1 mg protein-1 andan estimated Km of 3.3 ± 0.5 μM. The rate of copper uptake is reduced at an equimolar concentrationof albumin and is unaffected by zinc at a 10–fold molar excess. Approximately 70% of the newly incorporated radiocopper binds to membranes and organelles, while 30% is recovered in the cytosol. The soluble fraction can be resolved intotwo copper–binding protein peaks. Incubation of HepG2 with nonisotopic copper results in displacement of radiocopper associated with the proteins contained in the lower molecular weight peak. Exposure of the cells to cycloheximide inhibits the incorporation of the isotope into this fraction.