Activation of extracellular signal-regulated kinases 1 and 2 by insulin-like growth factor I in human osteosarcoma MG-63 cells

The activation of extracellular signal-regulated kinases 1 and 2 by insulin -like growth factor I in human osteosarcoma MG-63 cells was examined by Mon o Q ion exchange chromatography of cell extracts and measurement of myelin basic protein kinase activity, and by immunoblotting of cell extracts with a phospho-specific extracellular signal-regulated kinase antibody. Extracel lular signal-regulated kinase 1 appeared to be activated in resting cells a nd addition of insulin-like growth factor I resulted in the activation prim arily of extracellular signal-regulated kinase 2. Extracellular signal-regu lated kinase 2 was found in the nucleus after addition of insulin-like grow th factor I.