Site-directed mutagenesis of the human adenosine A2A receptor. Critical involvement of Glu13 in agonist recognition

Eur J Pharmacol. 1996 Aug 29;310(2-3):269-72. doi: 10.1016/0014-2999(96)00495-5.


A glutamic acid residue in the first transmembrane domain of the human adenosine A2A receptor was mutated to glutamine. Radioligand binding studies on COS-7 cell membranes expressing either the wild-type or the mutant receptor revealed that the affinity of the prototypic agonist CGS21680 (2-[4-[(2-carboxyethyl)phenyl]ethylamino]-5'-N-ethylcarboxamidoadenosine ) for the mutant receptor was 15-fold lower than for the wild-type receptor. This was confirmed in functional studies with intact cells. The EC50 values of CGS21680 for the stimulation of cAMP production differed in a similar way. Antagonists of various chemical structure were equally effective on both mutant and wild-type receptors, thus the mutation selectively diminishes agonist affinity. We propose an indirect perturbation of the binding site, perhaps through a proton transfer mechanism as suggested by molecular modelling.

MeSH terms

  • Cyclic AMP / biosynthesis
  • Glutamic Acid / metabolism*
  • Humans
  • Mutagenesis, Site-Directed
  • Purinergic P1 Receptor Agonists
  • Radioligand Assay
  • Receptors, Purinergic P1 / genetics*
  • Receptors, Purinergic P1 / metabolism


  • Purinergic P1 Receptor Agonists
  • Receptors, Purinergic P1
  • Glutamic Acid
  • Cyclic AMP