title: Effector coupling of stably transfected human A3 adenosine receptors in CHO cells.
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.
authors.affiliation: Institut für Pharmakologie und Toxikologie, Universität Würzburg, Versbacher Str. 9, Würzburg, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Englert
authors.forename: Ursula
authors.initials: U
authors.lastname: Quitterer
authors.forename: Karl Norbert
authors.initials: KN
authors.lastname: Klotz
mesh_terms: D000818:Animals; D016466:CHO Cells; D020013:Calcium Signaling / Q000502:physiology*; D006224:Cricetinae; D019204:GTP-Binding Proteins / Q000378:metabolism*; D006801:Humans; D043684:Receptor, Adenosine A3; D018047:Receptors, Purinergic P1 / Q000235:genetics / Q000378:metabolism*; D014162:Transfection
chemical_list: D043684:Receptor, Adenosine A3; D018047:Receptors, Purinergic P1; D019204:GTP-Binding Proteins