PROTEIN AGGREGATION AS PRIMARY AND CHARACTERISTIC CELL REACTION TO VARIOUS STRESSES

Ehrlich carcinoma and EL-4 thymoma ascites cells were subjected in vit ro to heat shock, ATP depletion, oxidative stress, Ca2+ overloading an d iodoacetamide treatment. After the transient stresses, Triton (X-100 )-insoluble (TIS) fractions were isolated from the cells and analysed by electrophoresis and immunoblotting. All stresses used caused rapid aggregation of cell proteins. This was manifested in a signficant rise in protein content in the TIS fractions. The protein increase was mos tly due to an increase in the insolubility of actin, 57 kDa protein of intermediate filaments, 70 kDa heat shock protein (HSP 70), and some specific proteins whose insolubilization was a characteristic sign for each type of cell injury. Different survival rates in the cell lines after either stress correlated well with differences in their TIS prot ein accretion. Possible mechanisms for stress-induced protein aggregat ion and its relationship with cell viability are suggested.