MAP KINASE ACTIVATION BY CYCLOSPORINE-A

Short treatment of HeLa cells with cyclosporine A led to the activatio n in the crude cell extracts of a MAP kinase-like activity. Fractionat ion by chromatography on a Mono Q column allowed the separation of two activities co-eluting with the MAP kinases ERK1 and ERK2. The activat ion of these two MAP kinases was demonstrated in Western Blotting by t he appearance, after CsA treatment, of two new slowly migrating forms on SDS electrophoretic gels. A similar activation was also obtained in renal epithelial BSC-1 cells and 3T3 fibroblasts. MAP kinase activati on might result from a perturbation of calcium homeostasis induced by CsA treatment. (C) 1997 Academic Press.