DIFFERENT INDUCTION OF 70,000-DA HEAT-SHOCK PROTEIN AND METALLOTHIONEIN IN HELA-CELLS BY COPPER

To clarify the physiological roles of heat shock proteins induced by copper, we studied the synthesis of these proteins and metallothionein, as well as the level and nature of copper incorporated into HeLa cells. Incubation in medium containing 200-mu-M cupric sulfate and above induced the synthesis of 70,000-Da heat shock protein (hsp70) in these cells. However, the synthesis of hsp70 did not increase in the presence of less than 200-mu-M cupric sulfate. On the other hand, the synthesis of metallothionein increased due to 100-mu-M cupric sulfate. The uptake of copper into the cells depended on the cupric sulfate concentration in the medium. To analyze the nature of the intracellular copper, cell extracts were separated by gel filtration chromatography into three fractions: the high molecular weight, metallothionein, and low molecular weight fractions. No copper was found in the low molecular weight fraction of control cells, but appeared distinctly at 200-mu-M cupric sulfate and above. Copper in the high molecular weight fraction also began to increase at 200-mu-M cupric sulfate and above, whereas in the metallothionein fraction it began to increase even at 50 to 100-mu-M cupric sulfate. Furthermore, inhibition of cell growth was also observed at 200-mu-M cupric sulfate and above but not at 100-mu-M and below. Since the induction of hsp70 synthesis and inhibition of cell growth occurred concomitantly with the increase of copper in the high and low molecular weight fractions, hsp70 seemed not to participate in the detoxification of copper as does metallothionein, although it may function in repairing damage caused by the metal.