Calcium and muscarinic agonist stimulation of type I adenylylcyclase in whole cells.
The type I adenylylcyclase which was originally purified and cloned from bovine brain is stimulated by Ca2+ and calmodulin in vitro. Although it has been proposed that this enzyme may couple elevations in intracellular Ca2+ to increases in cAMP in whole cells, this has not been demonstrated in vivo. In this study, the type I adenylylcyclase was expressed in human 293 cells, and the influence of extracellular Ca2+ and Ca2+ ionophore on intracellular cAMP levels was examined. The cAMP levels of control cells were unaffected by Ca2+ and A23187. In contrast, intracellular cAMP in 293 cells expressing type I adenylylcyclase was markedly elevated by addition of A23187 and extracellular Ca2+. In the presence of forskolin, the muscarinic agonist carbachol also increased cAMP in 293 cells expressing the type I adenylylcyclase. These data indicate that the type I adenylylcyclase can be stimulated by Ca2+ in vivo, and that muscarinic agonists may indirectly stimulate the enzyme by increasing intracellular free Ca2+.
Choi
E J
EJ
Department of Pharmacology, University of Washington, Seattle 98195.
Wong
S T
ST
Hinds
T R
TR
Storm
D R
DR
D000262:Adenylyl Cyclases / Q000378:metabolism*; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002217:Carbachol / Q000494:pharmacology*; D002460:Cell Line; D000242:Cyclic AMP / Q000378:metabolism; D004789:Enzyme Activation; D006801:Humans; D011976:Receptors, Muscarinic / Q000378:metabolism
D011976:Receptors, Muscarinic; D000001:Calcimycin; D002217:Carbachol; D000242:Cyclic AMP; D000262:Adenylyl Cyclases; D002118:Calcium