Differential temperature dependency of chemical stressors in HSF1-mediated stress response in mammalian cells

Expression of stress proteins is generally induced by a variety of stressors. To gain a better understanding of the sensing and induction mechanisms of stress responses, we studied the effects of culture temperature on responses to various stressors, since the induction of hsp70 in mammalian cells by heat shock is somehow modulated by culture temperature. Hsp70 was not induced by treatment with sodium arsenite, azetidine-2-carboxylic acid, or zinc sulfate at the level of heat shock factor (HSF) 1 activation in cells incubated at low temperature, although these treatments induced hsp70 in cells incubated at 37 degrees C. The repression of sodium arsenite or zinc sulfate-induced HSF1 activation by low temperature was not simply due to the inhibition of protein synthesis. On the other hand, heat shock and iodoacetamide induced HSF 1 activation in cells incubated at either temperature. Thus, there seem to be two kinds of stressors that induce HSF1 activation independently of or dependent on culture temperature. Furthermore, the reduction of glutathione level seemed to be essential for HSF1 activation by chemical stressors.