The α2 adrenergic receptors (α2ARs) are G protein-coupled receptors (GPCRs) that respond to adrenaline and noradrenaline and couple to the Gi/o family of G proteins. α2ARs play important roles in regulating the sympathetic nervous system. Dexmedetomidine is a highly selective α2AR agonist used in post-operative patients as an anxiety-reducing, sedative medicine that decreases the requirement for opioids. As is typical for selective αAR agonists, dexmedetomidine consists of an imidazole ring and a substituted benzene moiety lacking polar groups, which is in contrast to βAR-selective agonists, which share an ethanolamine group and an aromatic system with polar, hydrogen-bonding substituents. To better understand the structural basis for the selectivity and efficacy of adrenergic agonists, we determined the structure of the α2BAR in complex with dexmedetomidine and Go at a resolution of 2.9 Å by single-particle cryo-EM. The structure reveals the mechanism of α2AR-selective activation and provides insights into Gi/o coupling specificity.
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All data generated or analyzed during this study are included in this Article and its Supplementary Information. Sequences of constructs used in this study are listed in Supplementary Fig. 2 and described in the Methods. Cryo-EM density maps for the α2BAR–GoA and α2BAR–Gi1 complexes have been deposited in the Electron Microscopy Data Bank (EMDB) under accession codes EMD-9911 and EMD-9912, respectively. The coordinates for models of the α2BAR–GoA and α2BAR–Gi1 complexes have been deposited in the PDB under accession nos. 6K41 and 6K42, respectively.
The AutoEMation2.0 package is available upon request from J. Lei at Tsinghua University.
Lefkowitz, R. J. Seven transmembrane receptors: something old, something new. Acta Physiol. (Oxf.) 190, 9–19 (2007).
Rasmussen, S. G. F. et al. Crystal structure of the β2 adrenergic receptor–Gs protein complex. Nature 477, 549–555 (2011).
Rosenbaum, D. M. et al. GPCR engineering yields high-resolution structural insights into 2-adrenergic receptor function. Science 318, 1266–1273 (2007).
Ring, A. M. et al. Adrenaline-activated structure of β2-adrenoceptor stabilized by an engineered nanobody. Nature 502, 575–579 (2013).
Giovannoni, M. P., Ghelardini, C., Vergelli, C. & Dal Piaz, V. α2-agonists as analgesic agents. Med. Res. Rev. 29, 339–368 (2009).
Hein, L. Adrenoceptors and signal transduction in neurons. Cell Tissue Res. 326, 541–551 (2006).
Altman, J. D. et al. Abnormal regulation of the sympathetic nervous system in α2A-adrenergic receptor knockout mice. Mol. Pharmacol. 56, 154–161 (1999).
Hunter, J. C. et al. Assessment of the role of α2-adrenoceptor subtypes in the antinociceptive, sedative and hypothermic action of dexmedetomidine in transgenic mice. Br. J. Pharmacol. 122, 1339–1344 (1997).
Stone, L. S., MacMillan, L. B., Kitto, K. F., Limbird, L. E. & Wilcox, G. L. The α2a adrenergic receptor subtype mediates spinal analgesia evoked by α2 agonists and is necessary for spinal adrenergic-opioid synergy. J. Neurosci. 17, 7157–7165 (1997).
Fairbanks, C. A. et al. α2C-adrenergic receptors mediate spinal analgesia and adrenergic-opioid synergy. J. Pharmacol. Exp. Ther. 300, 282–290 (2002).
Sawamura, S. et al. Antinociceptive action of nitrous oxide is mediated by stimulation of noradrenergic neurons in the brainstem and activation of α2B adrenoceptors. J. Neurosci. 20, 9242–9251 (2000).
Lakhlani, P. P. et al. Substitution of a mutant α2a-adrenergic receptor via ‘hit and run’ gene targeting reveals the role of this subtype in sedative, analgesic and anesthetic-sparing responses in vivo. Proc. Natl Acad. Sci. USA 94, 9950–9955 (1997).
Link, R. E. et al. Cardiovascular regulation in mice lacking α2-adrenergic receptor subtypes b and c. Science 273, 803–805 (1996).
Aantaa, R. & Jalonen, J. Perioperative use of α2-adrenoceptor agonists and the cardiac patient. Eur. J. Anaesthesiol. 23, 361–372 (2006).
Arcangeli, A., D’Alo, C. & Gaspari, R. Dexmedetomidine use in general anaesthesia. Curr. Drug Targets 10, 687–695 (2009).
Ruffolo, R. R. Jr, Bondinell, W. & Hieble, J. P. α- and β-adrenoceptors: from the gene to the clinic. 2. Structure–activity relationships and therapeutic applications. J. Med. Chem. 38, 3681–3716 (1995).
Jaakola, V. P. et al. Intracellularly truncated human α2B-adrenoceptors: stable and functional GPCRs for structural studies. J. Recept. Signal Transduct. Res. 25, 99–124 (2005).
Maeda, S. et al. Development of an antibody fragment that stabilizes GPCR/G-protein complexes. Nat. Commun. 9, 3712 (2018).
Maeda, S., Qu, Q., Robertson, M. J., Skiniotis, G. & Kobilka, B. K. Structures of the M1 and M2 muscarinic acetylcholine receptor/G-protein complexes. Science 364, 552–557 (2019).
Scheres, S. H. RELION: implementation of a bayesian approach to cryo-EM structure determination. J. Struct. Biol. 180, 519–530 (2012).
Adams, P. D. et al. PHENIX: a comprehensive Python-based system for macromolecular structure solution. Acta Crystallogr. D 66, 213–221 (2010).
Strader, C. D., Candelore, M. R., Hill, W. S., Sigal, I. S. & Dixon, R. A. Identification of two serine residues involved in agonist activation of the β-adrenergic receptor. J. Biol. Chem. 264, 13572–13578 (1989).
Pauwels, P. J. & Colpaert, F. C. Disparate ligand-mediated Ca2+ responses by wild-type, mutant Ser200Ala and Ser204Ala α2A-adrenoceptor: Gα15 fusion proteins: evidence for multiple ligand-activation binding sites. Br. J. Pharmacol. 130, 1505–1512 (2000).
Chen, S. et al. Phe310 in transmembrane VI of the α1B-adrenergic receptor is a key switch residue involved in activation and catecholamine ring aromatic bonding. J. Biol. Chem. 274, 16320–16330 (1999).
Schwinn, D. A., Correa-Sales, C., Page, S. O. & Maze, M. Functional effects of activation of alpha-1 adrenoceptors by dexmedetomidine: in vivo and in vitro studies. J. Pharmacol. Exp. Ther. 259, 1147–1152 (1991).
Isberg, V. et al. Generic GPCR residue numbers—aligning topology maps while minding the gaps. Trends Pharmacol. Sci. 36, 22–31 (2015).
Eason, M. G., Kurose, H., Holt, B. D., Raymond, J. R. & Liggett, S. B. Simultaneous coupling of α2-adrenergic receptors to two G-proteins with opposing effects. Subtype-selective coupling of α2C10, α2C4 and α2C2 adrenergic receptors to Gi and Gs. J. Biol. Chem. 267, 15795–15801 (1992).
Xiao, R. P. et al. Coupling of β2-adrenoceptor to Gi proteins and its physiological relevance in murine cardiac myocytes. Circ. Res. 84, 43–52 (1999).
Carpenter, B., Nehme, R., Warne, T., Leslie, A. G. & Tate, C. G. Erratum. Structure of the adenosine A2A receptor bound to an engineered G protein. Nature 538, 542 (2016).
Thal, D. M., Glukhova, A., Sexton, P. M. & Christopoulos, A. Structural insights into G-protein-coupled receptor allostery. Nature 559, 45–53 (2018).
Garcia-Nafria, J. & Tate, C. G. Cryo-EM structures of GPCRs coupled to Gs, Gi and Go. Mol. Cell. Endocrinol. 488, 1–13 (2019).
Connor, M. & Christie, M. D. Opioid receptor signalling mechanisms. Clin. Exp. Pharmacol. Physiol. 26, 493–499 (1999).
Garcia-Nafria, J., Lee, Y., Bai, X., Carpenter, B. & Tate, C. G. Cryo-EM structure of the adenosine A2A receptor coupled to an engineered heterotrimeric G protein. Elife 7, e35946 (2018).
Zhang, Y. et al. Cryo-EM structure of the activated GLP-1 receptor in complex with a G protein. Nature 546, 248–253 (2017).
Liang, Y.-L. et al. Phase-plate cryo-EM structure of a class B GPCR–G-protein complex. Nature 546, 118–123 (2017).
Gregorio, G. G. et al. Single-molecule analysis of ligand efficacy in β2AR–G-protein activation. Nature 547, 68–73 (2017).
Liu, X. et al. Structural insights into the process of GPCR–G protein complex formation. Cell 177, 1243–1251 (2019).
Du, Y. et al. Assembly of a GPCR–G protein complex. Cell 177, 1232–1242 (2019).
Kato, H. E. et al. Conformational transitions of a neurotensin receptor 1–Gi1 complex. Nature 572, 80–85 (2019).
Li, X. et al. Electron counting and beam-induced motion correction enable near-atomic-resolution single-particle cryo-EM. Nat. Methods 10, 584–590 (2013).
Zheng, S. Q. et al. MotionCor2: anisotropic correction of beam-induced motion for improved cryo-electron microscopy. Nat. Methods 14, 331–332 (2017).
Mindell, J. A. & Grigorieff, N. Accurate determination of local defocus and specimen tilt in electron microscopy. J. Struct. Biol. 142, 334–347 (2003).
Pettersen, E. F. et al. UCSF Chimera—a visualization system for exploratory research and analysis. J. Comput. Chem. 25, 1605–1612 (2004).
Emsley, P. & Cowtan, K. Coot: model-building tools for molecular graphics. Acta Crystallogr. D Biol. Crystallogr. 60, 2126–2132 (2004).
Sali, A. & Blundell, T. L. Comparative protein modelling by satisfaction of spatial restraints. J. Mol. Biol. 234, 779–815 (1993).
Ghanouni, P. et al. The effect of pH on β2 adrenoceptor function. Evidence for protonation-dependent activation. J. Biol. Chem. 275, 3121–3127 (2000).
Wolf, M. G., Hoefling, M., Aponte-Santamaria, C., Grubmuller, H. & Groenhof, G. g_membed: efficient insertion of a membrane protein into an equilibrated lipid bilayer with minimal perturbation. J. Comput. Chem. 31, 2169–2174 (2010).
Case, D. A. et al. AMBER18 (Univ. California, 2018).
Wang, J., Wolf, R. M., Caldwell, J. W., Kollman, P. A. & Case, D. A. Development and testing of a general amber force field. J. Comput. Chem. 25, 1157–1174 (2004).
Dickson, C. J. et al. Lipid14: the AMBER lipid force field. J. Chem. Theory Comput. 10, 865–879 (2014).
Maier, J. A. et al. ff14SB: improving the accuracy of protein side chain and backbone parameters from ff99SB. J. Chem. Theory Comput. 11, 3696–3713 (2015).
Bayly, C. I., Cieplak, P., Cornell, W. D. & Kollman, P. A. A well-behaved electrostatic potential based method using charge restraints for deriving atomic charges—the RESP model. J. Phys. Chem. 97, 10269–10280 (1993).
Fanelli, F. Dimerization of the lutropin receptor: insights from computational modeling. Mol. Cell. Endocrinol. 260–262, 59–64 (2007).
Van Der Spoel, D. et al. GROMACS: fast, flexible and free. J. Comput. Chem. 26, 1701–1718 (2005).
Abraham, M. J. et al. GROMACS: high performance molecular simulations through multi-level parallelism from laptops to supercomputers. Softwarex 1–2, 19–25 (2015).
Hess, B., Bekker, H., Berendsen, H. J. C. & Fraaije, J. G. E. M. LINCS: A linear constraint solver for molecular simulations. J. Comput. Chem. 18, 1463–1472 (1997).
Darden, T., York, D. & Pedersen, L. Particle mesh Ewald: an N⋅log(N) method for Ewald sums in large systems. J. Chem. Phys. 98, 10089–10092 (1993).
Roe, D. R. & Cheatham, T. E. III PTRAJ and CPPTRAJ: software for processing and analysis of molecular dynamics trajectory data. J. Chem. Theory Comput. 9, 3084–3095 (2013).
Hunter, J. D. Matplotlib: a 2D graphics environment. Comput. Sci. Eng. 9, 90–95 (2007).
Hanwell, M. D. et al. Avogadro: an advanced semantic chemical editor, visualization and analysis platform. J. Cheminform. 4, 17 (2012).
Trott, O. & Olson, A. J. AutoDock Vina: improving the speed and accuracy of docking with a new scoring function, efficient optimization and multithreading. J. Comput. Chem. 31, 455–461 (2010).
This work was supported by the Beijing Advanced Innovation Center for Structural Biology, Tsinghua-Peking Joint Center for Life Sciences, School of Medicine, Tsinghua University, by grant no. 2016YFA0501100 to H.-W.W. from the Ministry of Science and Technology of China and by DFG grant GRK 1910 to P.G. and J.K. Computing resources were provided by the RRZE. We thank Y. Du, W. Huang and D. Hilger for help in protein purification and S. Han for structure analysis. We are thankful to J. Lei, X. Li, X. Li and T. Yang for providing the cryo-EM and high-performance computational facility support, and J. Wang, X. Fan, Q. Zhou, S. Sun, F. Yang and X. Pi for their technical assistance with cryo-EM data processing. We thank the Erlangen Regional Computing Center (RRZE) for computer resources and support. B.K.K. is a Chan Zuckerberg Biohub investigator and a Einstein BIH visiting fellow.
B.K.K. is co-founder of and consultant for ConfometRx.
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Yuan, D., Liu, Z., Kaindl, J. et al. Activation of the α2B adrenoceptor by the sedative sympatholytic dexmedetomidine. Nat Chem Biol 16, 507–512 (2020). https://doi.org/10.1038/s41589-020-0492-2
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