Ca(2+)-dependent sensitization of adenylyl cyclase activity.
It has been shown that intracellular Ca(2+) concentrations have multiple modulatory influences on hormone-stimulated adenylyl cyclase activity. Here, we report that increasing intracellular Ca(2+) concentration by treating cells with the Ca(2+) ionophore A23187 leads to a sensitization of the beta-adrenoceptor-stimulated adenylyl cyclase activity in Ltk(-) cells expressing the human beta(2)-adrenoceptor. The ionophore treatment led to a 20+/-5% increase of the maximal isoproterenol-stimulated cyclase activity that could be prevented by chelation of the extracellular Ca(2+) using EGTA. A similar Ca(2+)-mediated sensitization (20+/-6%) was observed when the adenylyl cyclase was directly stimulated by the diterpene forskolin indicating that the catalytic activity of the enzyme itself is modulated by the change in Ca(2+) concentration. Sensitization of both the isoproterenol- and forskolin-stimulated adenylyl cyclase activities were completely blocked by treatment with KN-62[1-[N,O-bis-(5-isoquinolinesulfonyl)-N-methyl-L-tyrosyl]-4-phenylpiperazine], an inhibitor of the Ca(2+)-calmodulin-dependent protein kinase (CamKinase). Taken together, our data reveal the existence of a CamKinase-dependent sensitization process acting at the level of the adenylyl cyclase catalytic moiety.
Rousseau
G
G
Hôpital du Sacré-Coeur de Montréal, Université de Montréal, Montreal, Quebec, Canada.
Haddad
P S
PS
Gallo-Payet
N
N
Bouvier
M
M
D000262:Adenylyl Cyclases / Q000187:drug effects / Q000378:metabolism*; D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000818:Animals; D001667:Binding, Competitive / Q000187:drug effects; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002460:Cell Line; D005576:Colforsin / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation / Q000187:drug effects; D015870:Gene Expression; D006801:Humans; D007476:Ionophores / Q000494:pharmacology; D007527:Isoenzymes / Q000187:drug effects / Q000378:metabolism; D007545:Isoproterenol / Q000494:pharmacology; D018343:Receptors, Adrenergic, beta-2 / Q000235:genetics / Q000378:metabolism
D000318:Adrenergic beta-Agonists; D007476:Ionophores; D007527:Isoenzymes; D018343:Receptors, Adrenergic, beta-2; D005576:Colforsin; D000001:Calcimycin; D000262:Adenylyl Cyclases; D007545:Isoproterenol; D002118:Calcium