Correlation of activation of Ca2+/calmodulin-dependent protein kinase II with catecholamine secretion and tyrosine hydroxylase activation in cultured bovine adrenal medullary cells

Abstract

We have investigated the activation of Ca2+/calmodulin-dependent protein kinase II (CaM kinase II) in cultured bovine adrenal medullary cells. The activation was assayed as an increase in the Ca(2+)-independent (autonomous) activity of CaM kinase II, using the synthetic substrate Syntide-2. Incubation of cells with acetylcholine increased the Ca(2+)-independent activity in a time (20 sec to 5.0 min)- and concentration (10-300 microM)-dependent manner. These curves were closely correlated with those of catecholamine secretion and tyrosine hydroxylase activation. Removal of extracellular Ca2+ completely abolished the stimulatory effects of acetylcholine on the Ca(2+)-independent activity, as well as on catecholamine secretion and activation of tyrosine hydroxylase. Nicotine but not muscarine increased the Ca(2+)-independent activity as potently as did acetylcholine, and hexamethonium but not atropine completely blocked the acetylcholine-induced increase. In 32P-labeled cells, acetylcholine stimulated the phosphorylation of a 50-kDa protein that was immunoprecipitated with an anti-brain CaM kinase II antibody. These results suggest that acetylcholine stimulates CaM kinase II activity through nicotinic acetylcholine receptor-mediated influx of Ca2+ and that the activation of CaM kinase II is closely related to catecholamine secretion and tyrosine hydroxylase activation in cultured adrenal medullary cells.