TY - JOUR T1 - Calmodulin may play a pivotal role in neurotransmitter-mediated inhibition and stimulation of rat cerebellar adenylate cyclase. JF - Molecular Pharmacology JO - Mol Pharmacol SP - 127 LP - 132 VL - 32 IS - 1 AU - M K Ahlijanian AU - D M Cooper Y1 - 1987/07/01 UR - http://molpharm.aspetjournals.org/content/32/1/127.abstract N2 - Adenylate cyclase activity was stimulated 2.5-fold by exogenous Ca2+/calmodulin (CaM) (1 microM) in rat cerebellar plasma membranes which had been depleted of endogenous Ca2+/CaM. In EGTA-washed membranes, phenylisopropyladenosine (an adenosine receptor agonist) was unable to inhibit adenylate cyclase activity unless exogenous Ca2+/CaM was included in the assay. Conversely, isoproterenol (a beta-adrenergic receptor agonist) was able to stimulate adenylate cyclase activity only in the absence of Ca2+/CaM. The regulation of adenylate cyclase activity by guanyl-5'-yl-imidodiphosphate [Gpp(NH)p, a nonhydrolyzable guanine nucleotide analog, used to monitor interactions between guanine nucleotide-binding proteins and the catalytic unit of adenylate cyclase] was similar to that of phenylisopropyladenosine and isoproterenol; i.e., Gpp(NH)p produced inhibition exclusively in the presence of Ca2+/CaM, whereas only stimulation was observed in the absence of Ca2+/CaM. These results suggest that changes in intracellular Ca2+ concentrations may determine whether adenylate cyclase can be stimulated or inhibited by neurotransmitters. ER -