Protein kinase translocation following beta-adrenergic receptor activation in C6 glioma cells

Incubation of C6 glioma cells with isoproterenol elicits an increase in cyclic AMP content, followed by an activation of cyclic AMP-dependent protein kinase (ATP:protein phosphotransferase, EC 2.7.1.37). The cytoplasm of these glioma cells contains type II protein kinase and a small amount of cyclic AMP-independent protein kinase. Following the persistent activation of cyclic AMP-dependent protein kinase, catalytic subunits of this enzyme redistribute into particulate fractions. A maximal increase in nuclear protein kinase activity occurrs 45 to 60 min following isoproterenol. The addition of cyclic AMP or of Ca2+ with or without the specific ionophore A-23187 fails to increase the protein kinase activity of nuclei from control or isoproterenol-treated cells. Preincubation of the cells with vinblastine blocks the increase of nuclear protein kinase activity due to isoproterenol. If the incubation with vinblastine occurs simultaneously with isoproterenol, vinblastine fails to reduce the increase in nuclear protein kinase activity elicited by isoproterenol.