THE PROTEIN-KINASE-C ISOFORMS LEADING TO MAP-KINASE ACTIVATION IN CHOCELLS

Stimulation of CHO cells with phorbol ester caused transient activatio n of mitogen-activated protein kinase (MAP-kinases with 42 and 44 kDa) . A similar treatment of CHO cells which overexpress a massive amount of the alpha- or delta-isoform of protein kinase C (PKC) resulted in t he prolonged activation of MAP-kinase and eventually in the appearance of mostly dikaryotic, sometimes tetrakaryotic cells. The results sugg est that the delta-isoform, as well as the alpha-isoform, has a potent ial to cause MAP kinase activation. Unusual activation of the PKC/MAP- kinase pathway, however, may lead to abnormal cytokinesis. (C) 1995 Ac ademic Press, Inc.