Concanavalin A prevents phorbol-mediated redistribution of protein kinase C and β-adrenergic receptors in rat glioma C6 cells

Abstract

Exposure of rat glioma C6 cells to the phorbol ester 12-O-tetradecanoylphorbol 13-acetate (TPA) caused an activation of protein kinase C where-in the enzyme rapidly became membrane-bound ( T 1 2 of 15 min). This translocation of protein kinase C from cytosol to membrane was followed by a sequestration of cell surface β-adrenergic receptors and a loss of isoproterenol-stimulated adenylate cyclase activity. We had reported previously that prior exposure of rat glioma cells to concanavalin A prevents the TPA-mediated sequestration of receptors and desensitization of adenylate cyclase (Kassis et al., 1985). We now show that the concanavalin A treatment also prevents the translocation and activation of protein kinase C. These results are further evidence that in the TPA-treated cells, sequestration of β-adrenergic receptors is mediated by membrane-bound protein kinase C.