OKADAIC ACID POTENTIATES HEAT-INDUCED ACTIVATION OF ERK2

Subjecting exponentially growing HeLa cells to heat shock at 45 degree s C for 30 min leads to retarded migration of erk1 and erk2, as reveal ed on immunoblots indicating their activation. Renaturation gels confi rmed activation of erk2 but not erk1. Treatment of cells with okadaic acid (OA) alone marginally upregulated erk1 and erk2, whereas simultan eous exposure to heat shock and OA led to a considerably augmented res ponse for erk2 which was approximately 3-foId higher than the sum of h eat- and OA-induced activation. Chronic treatment of cells with 12-O-t etradecanoyl-phorbol 13-acetate marginally diminished the extent of er k2 stimulation, but had no influence on the OA-induced potentiation of heat-induced erk2 activity.