Agonist-bound adenosine A2A receptor structures reveal common features of GPCR activation


Adenosine receptors and β-adrenoceptors are G-protein-coupled receptors (GPCRs) that activate intracellular G proteins on binding the agonists adenosine1 or noradrenaline2, respectively. GPCRs have similar structures consisting of seven transmembrane helices that contain well-conserved sequence motifs, indicating that they are probably activated by a common mechanism3,4. Recent structures of β-adrenoceptors highlight residues in transmembrane region 5 that initially bind specifically to agonists rather than to antagonists, indicating that these residues have an important role in agonist-induced activation of receptors5,6,7. Here we present two crystal structures of the thermostabilized human adenosine A2A receptor (A2AR-GL31) bound to its endogenous agonist adenosine and the synthetic agonist NECA. The structures represent an intermediate conformation between the inactive and active states, because they share all the features of GPCRs that are thought to be in a fully activated state, except that the cytoplasmic end of transmembrane helix 6 partially occludes the G-protein-binding site. The adenine substituent of the agonists binds in a similar fashion to the chemically related region of the inverse agonist ZM241385 (ref. 8). Both agonists contain a ribose group, not found in ZM241385, which extends deep into the ligand-binding pocket where it makes polar interactions with conserved residues in H7 (Ser 2777.42 and His 2787.43; superscripts refer to Ballesteros–Weinstein numbering9) and non-polar interactions with residues in H3. In contrast, the inverse agonist ZM241385 does not interact with any of these residues and comparison with the agonist-bound structures indicates that ZM241385 sterically prevents the conformational change in H5 and therefore it acts as an inverse agonist. Comparison of the agonist-bound structures of A2AR with the agonist-bound structures of β-adrenoceptors indicates that the contraction of the ligand-binding pocket caused by the inward motion of helices 3, 5 and 7 may be a common feature in the activation of all GPCRs.

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Figure 1: Structure of the adenosine A 2A receptor bound to NECA compared to other GPCR structures.
Figure 2: Comparison of receptor–ligand interactions for A 2A R bound to the inverse agonist ZM241385 and the agonists NECA and adenosine.
Figure 3: Positions of adenosine and ZM241385 in the A 2A R ligand-binding pocket.
Figure 4: Comparison of the positions of agonists in the binding pockets of the A 2A R and β 1 -AR.

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Protein Data Bank

Data deposits

Co-ordinates and structure factors have been submitted to the PDB database under accession codes 2YDO and 2YDV for A2AR-GL31 bound to adenosine or NECA, respectively.


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This work was supported by core funding from the Medical Research Council, and grants from Heptares Therapeutics Ltd and from the Biotechnology and Biological Sciences Research Council (BB/G003653/1). We would like to thank F. Magnani for technical help at the start of the project and F. Gorrec for developing the crystallization screen. We also thank the beamline staff at the European Synchrotron Radiation Facility, particularly at (beamline ID23-2; D. Flot and A. Popov), the Swiss Light Source (beamline X06SA) and at the Diamond Light Source (beamline I24; G. Evans, D. Axford and R. Owen). F. Marshall, M. Weir, M. Congreve and R. Henderson are thanked for their comments on the manuscript.

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G.L. devised and performed receptor expression, purification, crystallization, cryo-cooling of the crystals, data collection, data processing and structure refinement. T.W. and P.C.E. helped with expression, crystal cryo-cooling and data collection. K.B. performed the radioligand binding assays and pharmacological analyses on receptor mutants in whole cells and C.J.L. was involved in data analysis and experimental design. A.G.W.L. was involved in data processing and structure refinement. Manuscript preparation was performed by G.L., A.G.W.L. and C.G.T. Overall project management was by C.G.T.

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Correspondence to Christopher G. Tate.

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Lebon, G., Warne, T., Edwards, P. et al. Agonist-bound adenosine A2A receptor structures reveal common features of GPCR activation. Nature 474, 521–525 (2011).

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