Abstract
Many types of cells exhibit increased adenylyl cyclase (AC) activity after chronic agonist treatment of Gi/o-coupled receptors. This phenomenon, defined as AC superactivation or sensitization, has mostly been studied for the opioid receptors and is implicated in opiate addiction. Here we show that this phenomenon is also observed on chronic activation of the CB1 cannabinoid receptor. Moreover, using COS-7 cells cotransfected with CB1 receptor and individual AC isozymes, we could show selective superactivation of AC types I, III, V, VI, and VIII. The level of superactivation was dependent on the concentration of agonist and time of agonist exposure and was not dependent on the AC stimulator used. No superactivation of AC types II, IV, or VII was observed in COS-7 cells cotransfected with CB1. The superactivation of AC type V was abolished by pretreatment with pertussis toxin and by cotransfection with the carboxy terminus of β-adrenergic receptor kinase, which serves as a scavenger of Gβγ dimers, implying a role for the Gi/o proteins and especially Gβγ dimers in the cannabinoid-induced superactivation of AC.
Footnotes
- Received October 14, 1999.
- Accepted December 20, 1999.
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Send reprint requests to: Prof. Zvi Vogel, Dept. of Neurobiology, Weizmann Institute of Science, Rehovot 76100, Israel. E-mail: zvi.vogel{at}weizmann.ac.il
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↵1 This work was supported by the Israel Science Foundation. Z.V. is the incumbent of the Ruth and Leonard Simon Chair for Cancer Research.
- The American Society for Pharmacology and Experimental Therapeutics
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