Effector coupling of stably transfected human A3 adenosine receptors in CHO cells |
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| Authors: | Englert Martin Quitterer Ursula Klotz Karl Norbert |
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| Affiliation: | Institut für Pharmakologie und Toxikologie, Universit?t Würzburg, Versbacher Str. 9, Würzburg, Germany. |
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| 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. |
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| Keywords: | AB-MECA, N6-4-aminobenzyladenosine-5′-N-methyluronamide CCPA, 2-chloro-N6-cyclopentyladenosine CGS 21680, 2-[p-(2-carboxyethyl)phenylethylamino]-adenosine-5′-N-ethyluronamide Cl-IB-MECA, 2-chloro-N6-3-iodobenzyladenosine-5′-N-methyluronamide CPA, N6-cyclopentyladenosine IAB-MECA, N6-4-amino-3-iodobenzyladenosine-5’-N-methyluronamide NECA, 5′-N-ethylcarboxamidoadenosine PENECA, 2-phenylethynyl-adenosine-5′-N-ethyluronamide PHPNECA, 2-(3-hydroxy-3-phenyl)propyn-1-yl-adenosine-5′-N-ethyluronamide PIA, N6-(2-phenylisopropyl)adenosine XAC, xanthine amine congener, 8-[4-[[[[(2-aminoethyl)amino]carbonyl]methyl]oxy]phenyl]-1,3-dipro-pylxanthine. |
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