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Ca(2+)-dependent sensitization of adenylyl cyclase activity
G Rousseau1, P S Haddad, N Gallo-Payet
1Hôpital du Sacré-Coeur de Montréal, Université de Montréal, Montreal, Quebec, Canada.
European Journal of Pharmacology
|June 30, 2001
Summary
Increasing intracellular calcium (Ca2+) sensitizes beta-adrenoceptor and forskolin-stimulated adenylyl cyclase activity. This Ca2+-mediated sensitization is dependent on Ca2+-calmodulin-dependent protein kinase (CamKinase).
Area of Science:
- Cellular signaling
- Molecular pharmacology
Background:
- Intracellular calcium (Ca2+) concentrations modulate hormone-stimulated adenylyl cyclase activity.
- The beta-adrenoceptor pathway is a key regulator of cellular responses.
Purpose of the Study:
- To investigate the effect of increased intracellular Ca2+ on beta-adrenoceptor-stimulated adenylyl cyclase activity.
- To elucidate the role of Ca2+ and CamKinase in adenylyl cyclase regulation.
Main Methods:
- Treatment of Ltk(-) cells expressing the human beta(2)-adrenoceptor with Ca2+ ionophore A23187.
- Measurement of adenylyl cyclase activity stimulated by isoproterenol and forskolin.
- Inhibition of Ca2+-calmodulin-dependent protein kinase (CamKinase) using KN-62.
Main Results:
- Increased intracellular Ca2+ sensitized both beta-adrenoceptor- and forskolin-stimulated adenylyl cyclase activity by approximately 20%.
- This sensitization was dependent on extracellular Ca2+ and was blocked by EGTA.
- The Ca2+-mediated sensitization was completely inhibited by KN-62, a CamKinase inhibitor.
Conclusions:
- Intracellular Ca2+ can sensitize adenylyl cyclase activity through a CamKinase-dependent mechanism.
- This sensitization acts directly on the catalytic moiety of adenylyl cyclase.
- Reveals a novel regulatory pathway for adenylyl cyclase involving Ca2+ and CamKinase.