Stress-induced insolubilization of certain proteins in ascites tumor cells.

The stress-induced redistribution of cellular proteins between Triton (X-100)-soluble and Triton-insoluble fractions was studied in EL-4 thymoma and Ehrlich carcinoma cells. It was shown by electrophoresis and immunoblotting that a common sign of the cells which in vitro underwent such different harmful influences as ATP depletion, heat shock, oxidative stress, and SH reagent treatment was significant insolubilization of actin and 70-kDa heat-shock protein (hsp70). At the same time, each type of injury caused the specific insolubilization of some major cellular proteins. The transient ATP deprivation alone (without protein denaturation) induced a rapid insolubilization of myosin that was the earliest manifestation of ATP deficiency in the cells. Thermal stress without sharp decrease in ATP level induced a transition of 90-kDa heat-shock protein (hsp90) and 47-kDa polypeptide in Triton-insoluble fraction. The insolubilization of myosin and 47- and 35-kDa proteins was typical for the cells subjected to oxidative stress or SH reagent treatment, both of which caused damage of cellular proteins as well as ATP loss. The redistribution of the above proteins was intrinsic in the stressed cells of either ascites cell line, allowing one to consider it as characteristic and stress-specific cellular response to various injuries.