Effector coupling of stably transfected human A3 adenosine receptors
in CHO cells
Biochem Pharmacol, 64 (1):
61-5 (July 2002)Englert, Martin Quitterer, Ursula Klotz, Karl Norbert England Biochemical
pharmacology Biochem Pharmacol. 2002 Jul 1;64(1):61-5..Abstract
CHO cells stably transfected with adenosine receptors are widely utilized
models for binding and functional studies. The effector coupling
of human A3 adenosine receptors expressed in such a cellular model
was characterized. Inhibition of adenylyl cyclase via a pertussis
toxin-sensitive G protein was confirmed and exhibited a pharmacological
profile in accordance with agonist binding data. The agonist potency
was dependent on the assay system utilized to measure cyclase inhibition.
Agonists were more potent in a cell-based assay than in experiments
where cyclase inhibition was measured in a membrane preparation suggesting
that receptor-effector coupling might be more efficient in intact
cells. In addition to the modulation of cyclase activity, stimulation
of A3 receptors elicited a Ca2+ response in CHO cells with agonist
potencies corresponding to the values for the whole cell cAMP assay.
The Ca2+ signal was completely eliminated by pertussis toxin treatment
suggesting that it is mediated via betagamma release from a heterotrimeric
G protein of the Gi/o family. These results show that cAMP and Ca2+
signaling characteristics of the A3 adenosine receptor are comparable
to the ones found for the A1 subtype.