title: Molecular Determinants of CGS21680 Binding to the Human Adenosine A2A Receptor.
abstract: The adenosine A2A receptor (A(2A)R) plays a key role in transmembrane signaling mediated by the endogenous agonist adenosine. Here, we describe the crystal structure of human A2AR thermostabilized in an active-like conformation bound to the selective agonist 2-[p-(2-carboxyethyl)phenylethyl-amino]-5'-N-ethylcarboxamido adenosine (CGS21680) at a resolution of 2.6 Å. Comparison of A(2A)R structures bound to either CGS21680, 5'-N-ethylcarboxamido adenosine (NECA), UK432097 [6-(2,2-diphenylethylamino)-9-[(2R,3R,4S,5S)-5-(ethylcarbamoyl)-3,4-dihydroxy-tetrahydrofuran-2-yl]-N-[2-[[1-(2-pyridyl)-4-piperidyl]carbamoylamino]ethyl]purine-2-carboxamide], or adenosine shows that the adenosine moiety of the ligands binds to the receptor in an identical fashion. However, an extension in CGS21680 compared with adenosine, the (2-carboxyethyl)phenylethylamino group, binds in an extended vestibule formed from transmembrane regions 2 and 7 (TM2 and TM7) and extracellular loops 2 and 3 (EL2 and EL3). The (2-carboxyethyl)phenylethylamino group makes van der Waals contacts with side chains of amino acid residues Glu169(EL2), His264(EL3), Leu267(7.32), and Ile274(7.39), and the amine group forms a hydrogen bond with the side chain of Ser67(2.65). Of these residues, only Ile274(7.39) is absolutely conserved across the human adenosine receptor subfamily. The major difference between the structures of A(2A)R bound to either adenosine or CGS21680 is that the binding pocket narrows at the extracellular surface when CGS21680 is bound, due to an inward tilt of TM2 in that region. This conformation is stabilized by hydrogen bonds formed by the side chain of Ser67(2.65) to CGS21680, either directly or via an ordered water molecule. Mutation of amino acid residues Ser67(2.65), Glu169(EL2), and His264(EL3), and analysis of receptor activation either in the presence or absence of ligands implicates this region in modulating the level of basal activity of A(2A)R.
authors.affiliation: Institut de Génomique Fonctionelle, Centre National de la Recherche Scientifique, Unité Mixte de Recherche 5203, Institut National de la Sante et de la Recherche Medicale U1191, Université de Montpellier, Montpellier, France (G.L.); and Medical Research Council Laboratory of Molecular Biology, Cambridge Biomedical Campus, Cambridge, United Kingdom (P.C.E., A.G.W.L., C.G.T.) guillaume.lebon@igf.cnrs.fr cgt@mrc-lmb.cam.ac.uk.
authors.forename: Guillaume
authors.initials: G
authors.lastname: Lebon
authors.affiliation: Institut de Génomique Fonctionelle, Centre National de la Recherche Scientifique, Unité Mixte de Recherche 5203, Institut National de la Sante et de la Recherche Medicale U1191, Université de Montpellier, Montpellier, France (G.L.); and Medical Research Council Laboratory of Molecular Biology, Cambridge Biomedical Campus, Cambridge, United Kingdom (P.C.E., A.G.W.L., C.G.T.).
authors.forename: Patricia C
authors.initials: PC
authors.lastname: Edwards
authors.affiliation: Institut de Génomique Fonctionelle, Centre National de la Recherche Scientifique, Unité Mixte de Recherche 5203, Institut National de la Sante et de la Recherche Medicale U1191, Université de Montpellier, Montpellier, France (G.L.); and Medical Research Council Laboratory of Molecular Biology, Cambridge Biomedical Campus, Cambridge, United Kingdom (P.C.E., A.G.W.L., C.G.T.).
authors.forename: Andrew G W
authors.initials: AG
authors.lastname: Leslie
authors.affiliation: Institut de Génomique Fonctionelle, Centre National de la Recherche Scientifique, Unité Mixte de Recherche 5203, Institut National de la Sante et de la Recherche Medicale U1191, Université de Montpellier, Montpellier, France (G.L.); and Medical Research Council Laboratory of Molecular Biology, Cambridge Biomedical Campus, Cambridge, United Kingdom (P.C.E., A.G.W.L., C.G.T.) guillaume.lebon@igf.cnrs.fr cgt@mrc-lmb.cam.ac.uk.
authors.forename: Christopher G
authors.initials: CG
authors.lastname: Tate
mesh_terms: D000241:Adenosine / Q000031:analogs & derivatives* / Q000737:chemistry / Q000494:pharmacology; D058908:Adenosine A2 Receptor Agonists / Q000737:chemistry* / Q000494:pharmacology; D000818:Animals; D016466:CHO Cells; D003412:Cricetulus; D018360:Crystallography, X-Ray; D000242:Cyclic AMP / Q000096:biosynthesis; D006801:Humans; D008958:Models, Molecular; D010627:Phenethylamines / Q000737:chemistry* / Q000494:pharmacology; D011487:Protein Conformation; D043705:Receptor, Adenosine A2A / Q000737:chemistry* / Q000378:metabolism
chemical_list: D058908:Adenosine A2 Receptor Agonists; D010627:Phenethylamines; D043705:Receptor, Adenosine A2A; C061282:2-(4-(2-carboxyethyl)phenethylamino)-5'-N-ethylcarboxamidoadenosine; D000242:Cyclic AMP; D000241:Adenosine