MAP KINASE ACTIVATION DURING HEAT-SHOCK IN QUIESCENT AND EXPONENTIALLY GROWING MAMMALIAN-CELLS

In numerous cases of signal transduction, the mitogen-activated protei n kinases (MAP kinases) or extracellular regulated kinases (ERKs) are found to be activated by phosphorylations which result in electrophore tic mobility changes. Activities of MAP kinases in cytosolic extracts can also be monitored by the capacity of such extracts to phosphorylat e myelin basic protein. These two assays were used to demonstrate that MAP kinases were rapidly activated during heat shock of both quiescen t and exponentially growing mammalian (hamster, rat, mouse and human) cells. Thus, the MAP kinase cascade is likely to also ensure heat-shoc k signal transduction and contribute to the regulation of the complex array of metabolic changes designated as the heat-shock response.