Review Article | Published:

Mechanisms of signalling and biased agonism in G protein-coupled receptors


G protein-coupled receptors (GPCRs) are the largest group of cell surface receptors in humans that signal in response to diverse inputs and regulate a plethora of cellular processes. Hence, they constitute one of the primary drug target classes. Progress in our understanding of GPCR dynamics, activation and signalling has opened new possibilities for selective drug development. A key advancement has been provided by the concept of biased agonism, which describes the ability of ligands acting at the same GPCR to elicit distinct cellular signalling profiles by preferentially stabilizing different active conformational states of the receptor. Application of this concept raises the prospect of ‘designer’ biased agonists as optimized therapeutics with improved efficacy and/or reduced side-effect profiles. However, this application will require a detailed understanding of the spectrum of drug actions and a structural understanding of the drug–receptor interactions that drive distinct pharmacologies. The recent revolution in GPCR structural biology provides unprecedented insights into ligand binding, conformational dynamics and the control of signalling outcomes. These insights, together with new approaches to multi-dimensional analysis of drug action, are allowing refined classification of drugs according to their pharmacodynamic profiles, which can be linked to receptor structure and predictions of preclinical drug efficacy.

Access optionsAccess options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Additional information

Publisher’s note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Related links

Common Gα Subunit Numbering (CGN): Drug Browser: Database: www.gpcrdb.orgNatural variation of GPCRs in the human population: Contacts Atlas: determinants of GPCR–G protein signalling:


  1. 1.

    Venkatakrishnan, A. J. et al. Structured and disordered facets of the GPCR fold. Curr. Opin. Struct. Biol. 27, 129–137 (2014).

  2. 2.

    Alexander, S. P. et al. The concise guide to pharmacology 2017/18: G protein-coupled receptors. Br. J. Pharmacol. 174, S17–S129 (2017).

  3. 3.

    Dunn, H. A. & Ferguson, S. S. G. PDZ protein regulation of G protein-coupled receptor trafficking and signaling pathways. Mol. Pharmacol. 88, 624–639 (2015).

  4. 4.

    Ellisdon, A. M. & Halls, M. L. Compartmentalization of GPCR signalling controls unique cellular responses. Biochem. Soc. Trans. 44, 562–567 (2016).

  5. 5.

    Hilger, D., Masureel, M. & Kobilka, B. K. Structure and dynamics of GPCR signaling complexes. Nat. Struct. Mol. Biol. 25, 1–34 (2017).

  6. 6.

    Komolov, K. E. & Benovic, J. L. G protein-coupled receptor kinases: past, present and future. Cell. Signal. 41, 17–24 (2018).

  7. 7.

    Peterson, Y. K. & Luttrell, L. M. The diverse roles of arrestin scaffolds in G protein–coupled teceptor signaling. Pharmacol. Rev. 69, 256–297 (2017).

  8. 8.

    Khan, S. M., Sung, J. Y. & Hébert, T. E. Gβγ subunits — different spaces, different faces. Pharmacol. Res. 111, 434–441 (2016).

  9. 9.

    Furness, S. G. B. et al. Ligand-dependent modulation of G protein conformation alters drug efficacy. Cell 167, 739–749 (2016). This study demonstrates that differential ligand–receptor conformations propagate to G proteins to control efficacy and that this propagation could contribute to biased agonism.

  10. 10.

    Gregorio, G. G. et al. Single-molecule analysis of ligand efficacy in β2AR–G-protein activation. Nature 547, 68–73 (2017).

  11. 11.

    Paek, J. et al. Multidimensional tracking of GPCR signaling via peroxidase-catalyzed proximity labeling. Cell 169, 338–349 (2017).

  12. 12.

    Sokolina, K. et al. Systematic protein–protein interaction mapping for clinically relevant human GPCRs. Mol. Syst. Biol. 13, 918 (2017).

  13. 13.

    Smith, J. S., Lefkowitz, R. J. & Rajagopal, S. Biased signalling: from simple switches to allosteric microprocessors. Nat. Rev. Drug Discov. 17, 243–260 (2018).

  14. 14.

    Ranjan, R., Dwivedi, H., Baidya, M., Kumar, M. & Shukla, A. K. Novel structural insights into GPCR–β-arrestin interaction and signaling. Trends Cell Biol. 27, 851–862 (2017).

  15. 15.

    Grundmann, M. et al. Lack of beta-arrestin signaling in the absence of active G proteins. Nat. Commun. 9, 341 (2018).

  16. 16.

    Tóth, A. D. et al. Heterologous phosphorylation-induced formation of a stability lock permits regulation of inactive receptors by β-arrestins. J. Biol. Chem. 293, 876–892 (2018).

  17. 17.

    Sriram, K. & Insel, P. A. GPCRs as targets for approved drugs: how many targets and how many drugs? Mol. Pharmacol. 93, 251–258 (2018).

  18. 18.

    Hauser, A. S., Attwood, M. M., Rask-Andersen, M., Schiöth, H. B. & Gloriam, D. E. Trends in GPCR drug discovery: new agents, targets and indications. Nat. Rev. Drug Discov. 16, 829–842 (2017).

  19. 19.

    Hauser, A. S. et al. Pharmacogenomics of GPCR drug targets. Cell 172, 41–54 (2018). This comprehensive study reveals that several GPCRs that are targeted by common drugs show extensive genetic variation in the human population, suggesting that taking GPCR variants into account when prescribing drugs would minimize ineffective treatments, adverse reactions and health-care expenses.

  20. 20.

    Flock, T. et al. Selectivity determinants of GPCR-G protein binding. Nature 545, 1–33 (2017). This study reveals the existence of selectivity barcodes on G proteins that are recognized by GPCRs and lays the foundation for understanding the molecular basis of G protein-coupling specificity.

  21. 21.

    Latorraca, N. R., Venkatakrishnan, A. J. & Dror, R. O. GPCR dynamics: structures in motion. Chem. Rev. 117, 139–155 (2017).

  22. 22.

    Klein Herenbrink, C. et al. The role of kinetic context in apparent biased agonism at GPCRs. Nat. Commun. 7, 1–14 (2016). This is the first detailed study on the role of kinetics in GPCR biased agonism that highlights the importance of considering kinetic context in the design and interpretation of biased agonism.

  23. 23.

    Irannejad, R. et al. Functional selectivity of GPCR-directed drug action through location bias. Nat. Chem. Biol. 13, 799–806 (2017).

  24. 24.

    Halls, M. L. et al. Plasma membrane localization of the μ-opioid receptor controls spatiotemporal signaling. Sci. Signal. 9, ra16 (2016).

  25. 25.

    Kenakin, T. Theoretical aspects of GPCR–ligand complex pharmacology. Chem. Rev. 117, 4–20 (2017).

  26. 26.

    Burg, J. S. et al. Structural basis for chemokine recognition and activation of a viral G protein-coupled receptor. Science 347, 1113–1117 (2015).

  27. 27.

    Zhang, B., Albaker, A., Plouffe, B., Lefebvre, C. & Tiberi, M. Constitutive activities and inverse agonism in dopamine receptors. Adv. Pharmacol. 70, 175–214 (2014).

  28. 28.

    Stamm, S., Gruber, S. B., Rabchevsky, A. G. & Emeson, R. B. The activity of the serotonin receptor 2C is regulated by alternative splicing. Hum. Genet. 136, 1079–1091 (2017).

  29. 29.

    Lebon, G., Warne, T. & Tate, C. G. Agonist-bound structures of G protein-coupled receptors. Curr. Opin. Struct. Biol. 22, 482–490 (2012).

  30. 30.

    Jacobsen, S. E. et al. The GPRC6A receptor displays constitutive internalization and sorting to the slow recycling pathway. J. Biol. Chem. 292, 6910–6926 (2017).

  31. 31.

    Cooney, K. A., Molden, B. M., Kowalczyk, N. S., Russell, S. & Baldini, G. Lipid stress inhibits endocytosis of melanocortin-4 receptor from modified clathrin-enriched sites and impairs receptor desensitization. J. Biol. Chem. 292, 17731–17745 (2017).

  32. 32.

    Barbash, S., Lorenzen, E., Persson, T., Huber, T. & Sakmar, T. P. GPCRs globally coevolved with receptor activity-modifying proteins, RAMPs. Proc. Natl Acad. Sci. USA 114, 12015–12020 (2017).

  33. 33.

    Hay, D. L. & Pioszak, A. A. Receptor activity-modifying proteins (RAMPs): new insights and roles. Annu. Rev. Pharmacol. Toxicol. 56, 469–487 (2016).

  34. 34.

    Rouault, A. A. J., Srinivasan, D. K., Yin, T. C., Lee, A. A. & Sebag, J. A. Melanocortin receptor accessory proteins (MRAPs): functions in the melanocortin system and beyond. Biochim. Biophys. Acta 1863, 2462–2467 (2017).

  35. 35.

    Mølleskov-Jensen, A. S., Oliveira, M. T., Farrell, H. E. & Davis-Poynter, N. Virus-encoded 7 transmembrane receptors. Prog. Mol. Biol. Transl Sci. 129, 353–393 (2015).

  36. 36.

    Cheloha, R. W., Gellman, S. H., Vilardaga, J.-P. & Gardella, T. J. PTH receptor-1 signalling — mechanistic insights and therapeutic prospects. Nat. Rev. Endocrinol. 11, 712–724 (2015).

  37. 37.

    Hannan, F. M., Olesen, M. K. & Thakker, R. V. Calcimimetic and calcilytic therapies for inherited disorders of the calcium-sensing receptor signalling pathway. Br. J. Pharmacol. (2017).

  38. 38.

    Zantomio, D. et al. Convergent evidence for mGluR5 in synaptic and neuroinflammatory pathways implicated in ASD. Neurosci. Biobehav. Rev. 52, 172–177 (2015).

  39. 39.

    Brown, L. S. & Ernst, O. P. Recent advances in biophysical studies of rhodopsins – oligomerization, folding, and structure. Biochim. Biophys. Acta 1865, 1512–1521 (2017).

  40. 40.

    Zürn, A. et al. Fluorescence resonance energy transfer analysis of alpha 2a-adrenergic receptor activation reveals distinct agonist-specific conformational changes. Mol. Pharmacol. 75, 534–541 (2009).

  41. 41.

    Maier-Peuschel, M. et al. A fluorescence resonance energy transfer-based M2 muscarinic receptor sensor reveals rapid kinetics of allosteric modulation. J. Biol. Chem. 285, 8793–8800 (2010).

  42. 42.

    Devost, D. et al. Conformational profiling of the AT1 angiotensin II receptor reflects biased agonism, G protein coupling, and cellular context. J. Biol. Chem. 292, 5443–5456 (2017).

  43. 43.

    Liang, Y.-L. et al. Phase-plate cryo-EM structure of a biased agonist- bound human GLP-1 receptor-Gs complex. Nature 555, 121–125 (2018). This study provides the highest resolution cyro-electron microscopy (cryo-EM) structure of a GPCR to date and the first structure of a GPCR bound by a biased peptide ligand.

  44. 44.

    Lee, M.-H. et al. The conformational signature of β-arrestin2 predicts its trafficking and signalling functions. Nature 531, 665–668 (2016). This study identifies distinct β-arrestin 2 conformational signatures that reflect the diverse functional roles of β-arrestins.

  45. 45.

    Nuber, S. et al. β-Arrestin biosensors reveal a rapid, receptor-dependent activation/deactivation cycle. Nature 531, 661–664 (2016).

  46. 46.

    Busillo, J. M. et al. Site-specific phosphorylation of CXCR4 is dynamically regulated by multiple kinases and results in differential modulation of CXCR4 signaling. J. Biol. Chem. 285, 7805–7817 (2010).

  47. 47.

    Kim, J. et al. Functional antagonism of different G protein-coupled receptor kinases for beta-arrestin-mediated angiotensin II receptor signaling. Proc. Natl Acad. Sci. USA 102, 1442–1447 (2005).

  48. 48.

    Zidar, D. A., Violin, J. D., Whalen, E. J. & Lefkowitz, R. J. Selective engagement of G protein coupled receptor kinases (GRKs) encodes distinct functions of biased ligands. Proc. Natl Acad. Sci. USA 106, 9649–9654 (2009).

  49. 49.

    Cahill, T. J. et al. Distinct conformations of GPCR–β-arrestin complexes mediate desensitization, signaling, and endocytosis. Proc. Natl Acad. Sci. USA 114, 2562–2567 (2017).

  50. 50.

    Butcher, A. J. et al. Differential G-protein-coupled receptor phosphorylation provides evidence for a signaling bar code. J. Biol. Chem. 286, 11506–11518 (2011).

  51. 51.

    Nobles, K. N. et al. Distinct phosphorylation sites on the β2-adrenergic receptor establish a barcode that encodes differential functions of β-arrestin. Sci. Signal. 4, ra51 (2011).

  52. 52.

    Shiraishi, Y. et al. Phosphorylation-induced conformation of β2-adrenoceptor related to arrestin recruitment revealed by NMR. Nat. Commun. 9, 194 (2018).

  53. 53.

    Katritch, V., Cherezov, V. & Stevens, R. C. Diversity and modularity of G protein-coupled receptor structures. Trends Pharmacol. Sci. 33, 17–27 (2012).

  54. 54.

    Venkatakrishnan, A. J. et al. Molecular signatures of G-protein-coupled receptors. Nature 494, 185–194 (2013). This work shows that, despite the very large diversity in the structure of class A GPCRs, there are common sets of non-covalent contacts between structurally equivalent residues that constitute the molecular signature of this GPCR class.

  55. 55.

    DeVree, B. T. et al. Allosteric coupling from G protein to the agonist-binding pocket in GPCRs. Nature 535, 182–186 (2016).

  56. 56.

    Venkatakrishnan, A. J. et al. Diverse activation pathways in class A GPCRs converge near the G-protein-coupling region. Nature 40, 383–388 (2016). This is a systematic analysis of GPCR structures that reveals conserved interaction networks and characteristic features of GPCR binding and conformational changes upon activation.

  57. 57.

    Dror, R. O. et al. Activation mechanism of the β2-adrenergic receptor. Proc. Natl Acad. Sci. USA 108, 18684–18689 (2011). This study provides long-timescale, atomic-level simulations that reveal the dynamics associated with activation of a GPCR as it transitions between multiple conformational states.

  58. 58.

    Nygaard, R. et al. The dynamic process of β2-adrenergic receptor activation. Cell 152, 532–542 (2013).

  59. 59.

    Manglik, A. et al. Structural insights into the dynamic process of β2-adrenergic receptor signaling. Cell 161, 1101–1111 (2015).

  60. 60.

    Malik, R. U., Dysthe, M., Ritt, M., Sunahara, R. K. & Sivaramakrishnan, S. ER/K linked GPCR-G protein fusions systematically modulate second messenger response in cells. Sci. Rep. 7, 7749 (2017).

  61. 61.

    Gupte, T. M., Malik, R. U., Sommese, R. F., Ritt, M. & Sivaramakrishnan, S. Priming GPCR signaling through the synergistic effect of two G proteins. Proc. Natl Acad. Sci. USA 114, 3756–3761 (2017).

  62. 62.

    Flock, T. et al. Universal allosteric mechanism for Gα activation by GPCRs. Nature 524, 173–179 (2015).

  63. 63.

    Dror, R. O. et al. Structural basis for nucleotide exchange in heteromeric G proteins. Science 348, 1361–1365 (2015). This study used atomic-level simulations to elucidate the nucleotide release mechanism, which is critical for G protein activation.

  64. 64.

    Wacker, D., Wang, C., Katritch, V. & Han, G. Structural features for functional selectivity at serotonin receptors. Science 469, 175–180 (2013).

  65. 65.

    Peng, Y. et al. 5-HT 2C receptor structures reveal the structural basis of GPCR polypharmacology. Cell 172, 719–730 (2018).

  66. 66.

    Schönegge, A. M. et al. Evolutionary action and structural basis of the allosteric switch controlling β2AR functional selectivity. Nat. Commun. 8, 2169 (2017).

  67. 67.

    Liu, J. J., Horst, R., Katritch, V., Stevens, R. C. & Wüthrich, K. Biased signaling pathways in β2-adrenergic receptor characterized by 19F-NMR. Science 335, 1106–1110 (2012). This study uses NMR techniques to observe conformational differences induced in a GPCR by biased ligands.

  68. 68.

    Ballesteros, J. A. & Weinstein, H. Integrated methods for the construction of three-dimensional models and computational probing of structure-function relations in G protein-coupled receptors. Methods Neurosciences 25, 366–428 (1995).

  69. 69.

    Che, T. et al. Structure of the nanobody-stabilized active state of the kappa opioid receptor. Cell 172, 55–61 (2018).

  70. 70.

    Wacker, D. et al. Crystal structure of an LSD-bound human serotonin receptor. Cell 168, 377–389 (2017).

  71. 71.

    Wacker, D., Stevens, R. C. & Roth, B. L. How ligands illuminate GPCR molecular pharmacology. Cell 170, 414–427 (2017).

  72. 72.

    McCorvy, J. D. et al. Structure-inspired design of β-arrestin-biased ligands for aminergic GPCRs. Nat. Chem. Biol. 14, 126–134 (2017).

  73. 73.

    Shukla, A. K. et al. Visualisation of arrestin recruitment by a G-protein-coupled receptor. Nature 512, 218–222 (2014).

  74. 74.

    Yang, F. et al. Phospho-selective mechanisms of arrestin conformations and functions revealed by unnatural amino acid incorporation and (19)F-NMR. Nat. Commun. 6, 8202 (2015).

  75. 75.

    Staus, D. P. et al. Sortase ligation enables homogeneous GPCR phosphorylation to reveal diversity in β-arrestin coupling. Proc. Natl Acad. Sci. USA 115, 3834–3839 (2018).

  76. 76.

    Zhou, X. E. et al. Identification of phosphorylation codes for arrestin recruitment by G protein-coupled receptors. Cell 170, 457–459 (2017).

  77. 77.

    Thomsen, A. R. B. et al. GPCR-G protein-beta-arrestin super-complex mediates sustained G protein signaling. Cell 166, 907–919 (2016).

  78. 78.

    Liang, Y. L. et al. Phase-plate cryo-EM structure of a class B GPCR-G-protein complex. Nature 546, 118–123 (2017). This study presents the first cryo-EM structure of a GPCR and the first structure of a class B GPCR in an active state bound by a peptide agonist and a heterotrimeric G protein.

  79. 79.

    Zhang, Y. et al. Cryo-EM structure of the activated GLP-1 receptor in complex with a G protein. Nature 546, 248–253 (2017).

  80. 80.

    Wootten, D., Miller, L. J., Koole, C., Christopoulos, A. & Sexton, P. M. Allostery and biased agonism at class B G protein-coupled receptors. Chem. Rev. 117, 111–138 (2017).

  81. 81.

    Siu, F. Y. et al. Structure of the human glucagon class B G-protein-coupled receptor. Nature 499, 444–449 (2013).

  82. 82.

    Hollenstein, K. et al. Structure of class B GPCR corticotropin-releasing factor receptor 1. Nature 499, 438–443 (2013). Together with reference 80, this study describes the first TMD structures of a class B GPCR and reveals a unique binding mode for an allosteric antagonist, which occurs deep in the transmembrane bundle.

  83. 83.

    Jazayeri, A. et al. Extra-helical binding site of a glucagon receptor antagonist. Nature 533, 274–277 (2016).

  84. 84.

    Song, G. et al. Human GLP-1 receptor transmembrane domain structure in complex with allosteric modulators. Nature 546, 312–315 (2017).

  85. 85.

    Koth, C. M. et al. Molecular basis for negative regulation of the glucagon receptor. Proc. Natl Acad. Sci. USA 109, 14393–14398 (2012).

  86. 86.

    Mukund, S. et al. Inhibitory mechanism of an allosteric antibody targeting the glucagon receptor. J. Biol. Chem. 288, 36168–36178 (2013).

  87. 87.

    Zhang, H. et al. Structure of the full-length glucagon class B G-protein-coupled receptor. Nature 546, 259–264 (2017).

  88. 88.

    Zhang, H. et al. Structure of the glucagon receptor in complex with a glucagon analogue. Nature 553, 106–110 (2018).

  89. 89.

    Jazayeri, A. et al. Crystal structure of the GLP-1 receptor bound to a peptide agonist. Nature 546, 254–258 (2017).

  90. 90.

    Wootten, D., Simms, J., Miller, L. J., Christopoulos, A. & Sexton, P. M. Polar transmembrane interactions drive formation of ligand-specific and signal pathway-biased family B G protein-coupled receptor conformations. Proc. Natl Acad. Sci. USA 110, 5211–5216 (2013).

  91. 91.

    Wootten, D. et al. The extracellular surface of the GLP-1 receptor is a molecular trigger for biased agonism. Cell 165, 1632–1643 (2016). This study provides some of the first molecular and mechanistic insights into the initiation and activation of biased agonism for a GPCR.

  92. 92.

    Dal Maso, E. et al. Extracellular loops 2 and 3 of the calcitonin receptor selectively modify agonist binding and efficacy. Biochem. Pharmacol. 150, 214–244 (2018).

  93. 93.

    Wootten, D. et al. A hydrogen-bonded polar network in the core of the glucagon-like peptide-1 receptor is a fulcrum for biased agonism: lessons from class B crystal structures. Mol. Pharmacol. 89, 335–347 (2016).

  94. 94.

    Wootten, D. et al. Key interactions by conserved polar amino acids located at the transmembrane helical boundaries in Class B GPCRs modulate activation, effector specificity and biased signalling in the glucagon-like peptide-1 receptor. Biochem. Pharmacol. 118, 68–87 (2016).

  95. 95.

    de Graaf, C. et al. Extending the structural view of class B GPCRs. Trends Biochem. Sci. 42, 946–960 (2017).

  96. 96.

    Harikumar, K. G. et al. Glucagon-like peptide-1 receptor dimerization differentially regulates agonist signaling but does not affect small molecule allostery. Proc. Natl Acad. Sci. USA 109, 18607–18612 (2012).

  97. 97.

    Harikumar, K. G., Lau, S., Sexton, P. M., Wootten, D. & Miller, L. J. Coexpressed class B G protein–coupled secretin and GLP-1 receptors self- and cross-associate: impact on pancreatic islets. Endocrinology 158, 1685–1700 (2017).

  98. 98.

    Schelshorn, D. et al. Lateral allosterism in the glucagon receptor family: glucagon-like peptide 1 induces G-protein-coupled receptor heteromer formation. Mol. Pharmacol. 81, 309–318 (2012).

  99. 99.

    Pediani, J. D., Ward, R. J., Marsango, S. & Milligan, G. Spatial intensity distribution analysis: studies of G protein-coupled receptor oligomerisation. Trends Pharmacol. Sci. 39, 175–186 (2018).

  100. 100.

    Møller, T. C., Moreno-Delgado, D., Pin, J.-P. & Kniazeff, J. Class C G protein-coupled receptors: reviving old couples with new partners. Biophys. Rep. 3, 57–63 (2017).

  101. 101.

    Geng, Y. et al. Structural mechanism of ligand activation in human calcium-sensing receptor. eLife 5, e13662 (2016).

  102. 102.

    Geng, Y., Bush, M., Mosyak, L., Wang, F. & Fan, Q. R. Structural mechanism of ligand activation in human GABAB receptor. Nature 504, 254–259 (2013).

  103. 103.

    Frangaj, A. & Fan, Q. R. Structural biology of GABA B receptor. Neuropharmacology 136, 68–79 (2017).

  104. 104.

    Xue, L. et al. Major ligand-induced rearrangement of the heptahelical domain interface in a GPCR dimer. Nat. Chem. Biol. 11, 134–140 (2015).

  105. 105.

    Leach, K. & Gregory, K. J. Molecular insights into allosteric modulation of Class C G protein-coupled receptors. Pharmacol. Res. 116, 105–118 (2017).

  106. 106.

    Cook, A. E. et al. Biased allosteric modulation at the CaS receptor engendered by structurally diverse calcimimetics. Br. J. Pharmacol. 172, 185–200 (2015).

  107. 107.

    Foster, D. J. & Conn, P. J. Allosteric modulation of GPCRs: new insights and potential utility for treatment of schizophrenia and other CNS disorders. Neuron 94, 431–446 (2017).

  108. 108.

    Dijkman, P. M. & Watts, A. Lipid modulation of early G protein-coupled receptor signalling events. Biochim. Biophys. Acta 1848, 2889–2897, (2015).

  109. 109.

    Desai, A. J., Dong, M., Langlais, B. T., Dueck, A. C. & Miller, L. J. Cholecystokinin responsiveness varies across the population dependent on metabolic phenotype. Am. J. Clin. Nutr. 106, 447–456 (2017).

  110. 110.

    Desai, A. J., Dong, M. & Miller, L. J. Beneficial effects of β-sitosterol on type 1 cholecystokinin receptor dysfunction induced by elevated membrane cholesterol. Clin. Nutr. 35, 1374–1379 (2016).

  111. 111.

    Zocher, M., Zhang, C., Rasmussen, S. G. F., Kobilka, B. K. & Muller, D. J. Cholesterol increases kinetic, energetic, and mechanical stability of the human β2-adrenergic receptor. Proc. Natl Acad. Sci. USA 109, E3463–E3472 (2012).

  112. 112.

    Inagaki, S. et al. Modulation of the interaction between neurotensin receptor NTS1 and Gq protein by lipid. J. Mol. Biol. 417, 95–111 (2012).

  113. 113.

    Dawaliby, R. et al. Allosteric regulation of G protein–coupled receptor activity by phospholipids. Nat. Chem. Biol. 3, 35–39 (2015).

  114. 114.

    Guinzberg, R. et al. Newly synthesized cAMP is integrated at a membrane protein complex signalosome to ensure receptor response specificity. FEBS J. 284, 258–276 (2017).

  115. 115.

    Stillwell, W. An Introduction to Biological Membranes: Composition, Structure and Function (Elsevier Science, 2016).

  116. 116.

    Harayama, T. & Riezman, H. Understanding the diversity of membrane lipid composition. Nat. Rev. Mol. Cell Biol. 19, 281–296 (2018).

  117. 117.

    Parton, R. G. & del Pozo, M. A. Caveolae as plasma membrane sensors, protectors and organizers. Nat. Rev. Mol. Cell Biol. 14, 98–112 (2013).

  118. 118.

    Rosholm, K. R. et al. Membrane curvature regulates ligand-specific membrane sorting of GPCRs in living cells. Nat. Chem. Biol. 13, 724–729 (2017). This study highlights the importance of membrane curvature in regulation of GPCR function.

  119. 119.

    Shukla, A. K. G Protein-Coupled Receptors: Signaling, Trafficking and Regulation Vol. 132 (Academic Press, 2016).

  120. 120.

    Wu, G. Trafficking of GPCRs Vol. 132 (Academic Press, 2015).

  121. 121.

    Bahouth, S. W. & Nooh, M. M. Barcoding of GPCR trafficking and signaling through the various trafficking roadmaps by compartmentalized signaling networks. Cell. Signal. 36, 42–55 (2017).

  122. 122.

    Wang, G., Wei, Z. & Wu, G. Role of Rab GTPases in the export trafficking of G protein-coupled receptors. Small GTPases 26, 130–135 (2017).

  123. 123.

    Irannejad, R., Tsvetanova, N. G., Lobingier, B. T. & von Zastrow, M. Effects of endocytosis on receptor-mediated signaling. Curr. Opin. Cell Biol. 35, 137–143 (2015).

  124. 124.

    Farran, B. An update on the physiological and therapeutic relevance of GPCR oligomers. Pharmacol. Res. 117, 303–327 (2017).

  125. 125.

    Franco, R., Martínez-Pinilla, E., Lanciego, J. L. & Navarro, G. Basic pharmacological and structural evidence for class A G-protein-coupled receptor heteromerization. Front. Pharmacol. 7, 76 (2016).

  126. 126.

    Gomes, I. et al. G protein–coupled receptor heteromers. Annu. Rev. Pharmacol. Toxicol. 56, 403–425 (2016).

  127. 127.

    DeBruine, Z. J., Xu, H. E. & Melcher, K. Assembly and architecture of the Wnt/β-catenin signalosome at the membrane. Br. J. Pharmacol. 174, 4564–4574 (2017).

  128. 128.

    McLatchie, L. M. et al. RAMPs regulate the transport and ligand specificity of the calcitonin-receptor-like receptor. Nature 393, 333–339 (1998).

  129. 129.

    Nikolaev, V. O. et al. Beta2-adrenergic receptor redistribution in heart failure changes cAMP compartmentation. Science 327, 1653–1657 (2010).

  130. 130.

    Lyon, A. R. et al. Plasticity of surface structures and beta2-adrenergic receptor localization in failing ventricular cardiomyocytes during recovery from heart failure. Circ. Heart Fail. 5, 357–365 (2012).

  131. 131.

    Jensen, D. D. et al. Endothelin-converting enzyme 1 and β-arrestins exert spatiotemporal control of substance P-induced inflammatory signals. J. Biol. Chem. 289, 20283–20294 (2014).

  132. 132.

    Ayling, L. J. et al. Adenylyl cyclase AC8 directly controls its micro-environment by recruiting the actin cytoskeleton in a cholesterol-rich milieu. J. Cell Sci. 125, 869–886 (2012).

  133. 133.

    Halls, M. L. & Cooper, D. M. F. Sub-picomolar relaxin signalling by a pre-assembled RXFP1, AKAP79, AC2, β-arrestin 2, PDE4D3 complex. EMBO J. 29, 2772–2787 (2010). This study identifies pre-assembled, ligand-independent GPCR signalosomes that allow a GPCR to respond to extremely low concentrations of circulating ligands.

  134. 134.

    Siljee, J. E. et al. Subcellular localization of MC4R with ADCY3 at neuronal primary cilia underlies a common pathway for genetic predisposition to obesity. Nat. Genet. 50, 180–185 (2018).

  135. 135.

    Navarro, G. et al. Evidence for functional pre-coupled complexes of receptor heteromers and adenylyl cyclase. Nat. Commun. 9, 1242 (2018).

  136. 136.

    Wehbi, V. L. et al. Noncanonical GPCR signaling arising from a PTH receptor–arrestin–Gβγ complex. Proc. Natl Acad. Sci. USA 110, 1530–1535 (2013). This study is one of the first to report a GPCR that promotes persistent G protein signalling from intracellular endosomal compartments, which is mediated by β-arrestins.

  137. 137.

    Suofu, Y. et al. Dual role of mitochondria in producing melatonin and driving GPCR signaling to block cytochrome c release. Proc. Natl Acad. Sci. USA 114, E7997–E8006 (2017).

  138. 138.

    Tadevosyan, A. et al. Intracellular angiotensin-II interacts with nuclear angiotensin receptors in cardiac fibroblasts and regulates RNA synthesis, cell proliferation, and collagen secretion. J. Am. Heart Assoc. 6, e004965 (2017).

  139. 139.

    Vaniotis, G. et al. Regulation of cardiac nitric oxide signaling by nuclear β-adrenergic and endothelin receptors. J. Mol. Cell. Cardiol. 62, 58–68 (2013).

  140. 140.

    Tsvetanova, N. G., Irannejad, R. & von Zastrow, M. G. Protein-coupled receptor (GPCR) signaling via heterotrimeric G proteins from endosomes. J. Biol. Chem. 290, 6689–6696 (2015).

  141. 141.

    Tsvetanova, N. G. & von Zastrow, M. Spatial encoding of cyclic AMP signaling specificity by GPCR endocytosis. Nat. Chem. Biol. 10, 1061–1065 (2014).

  142. 142.

    Vilardaga, J.-P., Jean-Alphonse, F. G. & Gardella, T. J. Endosomal generation of cAMP in GPCR signaling. Nat. Chem. Biol. 10, 700–706 (2014).

  143. 143.

    Jensen, D. D. et al. Neurokinin 1 receptor signaling in endosomes mediates sustained nociception and is a viable therapeutic target for prolonged pain relief. Sci. Transl Med. 9, eaal3447 (2017). This study reveals a critical role for endosomal signalling of a GPCR in pain perception and demonstrates the potential therapeutic use of endosomally targeted GPCR antagonists.

  144. 144.

    Yarwood, R. E. et al. Endosomal signaling of the receptor for calcitonin gene-related peptide mediates pain transmission. Proc. Natl Acad. Sci. USA 114, 12309–12314 (2017).

  145. 145.

    Jean-Alphonse, F. G. et al. β2-adrenergic receptor control of endosomal PTH receptor signaling via Gβγ. Nat. Chem. Biol. 13, 259–261 (2017).

  146. 146.

    Wright, P. T. et al. Caveolin-3 regulates compartmentation of cardiomyocyte beta2-adrenergic receptor-mediated cAMP signaling. J. Mol. Cell. Cardiol. 67, 38–48 (2014).

  147. 147.

    Beautrait, A. et al. A new inhibitor of the β-arrestin/AP2 endocytic complex reveals interplay between GPCR internalization and signalling. Nat. Commun. 8, 15054 (2017).

  148. 148.

    Sykes, D. A. et al. Extrapyramidal side effects of antipsychotics are linked to their association kinetics at dopamine D2 receptors. Nat. Commun. 8, 763 (2017).

  149. 149.

    Wacker, D. et al. Crystal structure of an LSD-bound human serotonin receptor. Cell 168, 377–389 (2017).

  150. 150.

    Lane, J. R., May, L. T., Parton, R. G., Sexton, P. M. & Christopoulos, A. A kinetic view of GPCR allostery and biased agonism. Nat. Chem. Biol. 13, 929–937 (2017).

  151. 151.

    Benredjem, B., Dallaire, P. & Pineyro, G. Analyzing biased responses of GPCR ligands. Curr. Opin. Pharmacol. 32, 71–76 (2017).

  152. 152.

    Bradley, S. J., Tobin, A. B. & Prihandoko, R. The use of chemogenetic approaches to study the physiological roles of muscarinic acetylcholine receptors in the central nervous system. Neuropharmacology 136, 421–426 (2018).

  153. 153.

    Roth, B. L. DREADDs for neuroscientists. Neuron 89, 683–694 (2016).

  154. 154.

    Bruchas, M. R. & Roth, B. L. New technologies for elucidating opioid receptor function. Trends Pharmacol. Sci. 37, 279–289 (2016).

  155. 155.

    Spangler, S. M. & Bruchas, M. R. Optogenetic approaches for dissecting neuromodulation and GPCR signaling in neural circuits. Curr. Opin. Pharmacol. 32, 56–70 (2017).

  156. 156.

    Boerrigter, G., Soergel, D. G., Violin, J. D., Lark, M. W. & Burnett, J. C. TRV120027, a novel beta-arrestin biased ligand at the angiotensin II type I receptor, unloads the heart and maintains renal function when added to furosemide in experimental heart failure. Circ. Heart Fail. 5, 627–634 (2012).

  157. 157.

    Tarigopula, M. et al. Cardiac myosin light chain phosphorylation and inotropic effects of a biased ligand, TRV120023, in a dilated cardiomyopathy model. Cardiovasc. Res. 107, 226–234 (2015).

  158. 158.

    Brust, T. F. et al. Biased agonists of the kappa opioid receptor suppress pain and itch without causing sedation or dysphoria. Sci. Signal. 9, ra117 (2016).

  159. 159.

    DeWire, S. M. et al. A G protein-biased ligand at the mu-opioid receptor is potently analgesic with reduced gastrointestinal and respiratory dysfunction compared with morphine. J. Pharmacol. Exp. Ther. 344, 708–717 (2013).

  160. 160.

    Manglik, A. et al. Structure-based discovery of opioid analgesics with reduced side effects. Nature 537, 185–190 (2016).

  161. 161.

    Schmid, C. L. et al. Bias factor and therapeutic window correlate to predict safer opioid analgesics. Cell 171, 1165–1175 (2017). This is an important study that examines the correlation between measures of biased agonism and in vivo therapeutic index (the ratio of beneficial to detrimental effects).

  162. 162.

    Desai, A. J. & Miller, L. J. Changes in the plasma membrane in metabolic disease: impact of the membrane environment on G protein-coupled receptor structure and function. Br. J. Pharmacol. (2018).

  163. 163.

    Vijayakumar, N. et al. White matter integrity in individuals at ultra-high risk for psychosis: a systematic review and discussion of the role of polyunsaturated fatty acids. BMC Psychiatry 16, 287 (2016).

  164. 164.

    Cheong, H. I. et al. Hypoxia sensing through β-adrenergic receptors. JCI Insight 1, e90240 (2016).

  165. 165.

    Shellhammer, J. P. et al. Amino acid metabolites that regulate G protein signaling during osmotic stress. PLoS Genet. 13, e1006829 (2017).

  166. 166.

    Ardura, J. A., Alonso, V., Esbrit, P. & Friedman, P. A. Oxidation inhibits PTH receptor signaling and trafficking. Biochem. Biophys. Res. Commun. 482, 1019–1024 (2017).

  167. 167.

    Ghanouni, P. et al. The effect of pH on beta(2) adrenoceptor function. Evidence for protonation-dependent activation. J. Biol. Chem. 275, 3121–3127 (2000).

  168. 168.

    Vickery, O. N., Machtens, J. P. & Zachariae, U. Membrane potentials regulating GPCRs: insights from experiments and molecular dynamics simulations. Curr. Opin. Pharmacol. 30, 44–50 (2016).

  169. 169.

    Isom, D. G. & Dohlman, H. G. Buried ionizable networks are an ancient hallmark of G protein-coupled receptor activation. Proc. Natl Acad. Sci. USA 112, 5702–5707 (2015).

  170. 170.

    Katritch, V. et al. Allosteric sodium in class A GPCR signaling. Trends Pharmacol. Sci. 39, 233–244 (2014).

  171. 171.

    Massink, A. et al. Sodium ion binding pocket mutations and adenosine A2A receptor function. Mol. Pharmacol. 82, 305–313 (2015).

  172. 172.

    Thompson, M. D. et al. Pharmacogenetics of the G protein-coupled receptors. Methods Mol. Biol. 1175, 189–242 (2014).

  173. 173.

    Perez, J. M. et al. β1-adrenergic receptor polymorphisms confer differential function and predisposition to heart failure. Nat. Med. 9, 1300–1305 (2003).

  174. 174.

    Liggett, S. B. et al. A polymorphism within a conserved beta(1)-adrenergic receptor motif alters cardiac function and beta-blocker response in human heart failure. Proc. Natl Acad. Sci. USA 103, 11288–11293 (2006).

  175. 175.

    Freitas, C. et al. Lymphoid differentiation of hematopoietic stem cells requires efficient Cxcr4 desensitization. J. Exp. Med. 214, 2023–2040 (2017).

  176. 176.

    Barak, L. S., Oakley, R. H., Laporte, S. A. & Caron, M. G. Constitutive arrestin-mediated desensitization of a human vasopressin receptor mutant associated with nephrogenic diabetes insipidus. Proc. Natl Acad. Sci. USA 98, 93–98 (2001).

  177. 177.

    Michel, M. C. & Charlton, S. J. Biased agonism in drug discovery — is it too soon to choose a path? Mol. Pharmacol. 93, 259–265 (2018).

  178. 178.

    Black, J. & Leff, P. Operational models of pharmacological agonism. Proc. R. Soc. 220, 141–162 (1983).

  179. 179.

    Hager, M. V., Clydesdale, L., Gellman, S. H., Sexton, P. M. & Wootten, D. Characterization of signal bias at the GLP-1 receptor induced by backbone modification of GLP-1. Biochem. Pharmacol. 136, 99–108 (2017).

  180. 180.

    Thompson, G. L. et al. Systematic analysis of factors influencing observations of biased agonism at the mu-opioid receptor. Biochem. Pharmacol. 113, 70–87 (2016).

  181. 181.

    Karamitri, A. et al. Melatonin MT2 receptor variants associated with type 2 diabetes affect specific subsets of the receptor signaling modalities. Sci. Signal. (in the press) (2018).

  182. 182.

    Qin, C. X. et al. Small-molecule-biased formyl peptide receptor agonist compound 17b protects against myocardial ischaemia-reperfusion injury in mice. Nat. Commun. 8, 14232 (2017).

  183. 183.

    van der Westhuizen, E. T., Breton, B., Christopoulos, A. & Bouvier, M. Quantification of ligand bias for clinically relevant β2-adrenergic receptor ligands: implications for drug taxonomy. Mol. Pharmacol. 85, 492–509 (2014).

  184. 184.

    Valant, C., Robert Lane, J., Sexton, P. M. & Christopoulos, A. The best of both worlds? Bitopic orthosteric/allosteric ligands of G protein–coupled receptors. Annu. Rev. Pharmacol. Toxicol. 52, 153–178 (2012).

  185. 185.

    Thal, D., Glukhova, A., Sexton, P. M. & Christopoulos, A. Structural insights into G-protein-coupled receptor allostery. Nature 559, 45–53 (2018).

  186. 186.

    Christopoulos, A. et al. International Union of Basic and Clinical Pharmacology. XC. Multisite pharmacology: Recommendations for the nomenclature of receptor allosterism and allosteric ligands. Pharmacol. Rev. 66, 918–947 (2014).

Download references


P.M.S., A.C. and D.W. are Principal, Senior Principal and Career Development Fellows of the National Health and Medical Research Council of Australia, respectively. M.M.B. and M.M.-S. acknowledge the UK Medical Research Council (MC_U105185859) for support. M.M.-S. is supported by a Federation of European Biochemical Societies Long-Term Fellowship, and M.M.B. is a Lister Institute Fellow and is also supported by the European Research Council (ERC-COG-2015-682414).

Reviewer information

Nature Reviews Molecular Cell Biology thanks T. Hebert, V. Katritch, S. Rajagopal and the other anonymous reviewer(s) for their contribution to the peer review of this work.

Author information

D.W., A.C., M.M.-S., M.M.B. and P.M.S. researched data for the article. D.W., A.C., M.M.B. and P.M.S. substantially contributed to discussion of content. D.W., M.M.B., M.M.-S. and P.M.S. wrote the article. D.W., A.C., M.M.-S., M.M.B. and P.M.S. reviewed and edited the manuscript before submission.

Competing interests

The authors declare no competing interests.

Correspondence to Denise Wootten or Patrick M. Sexton.



A light-sensitive G protein-coupled receptor involved in visual phototransduction.


A family of intracellular transducers that can act as G protein-coupled receptor modulators by blocking G protein-mediated signalling, promoting receptor internalization and activating G protein-independent signalling pathways.


A molecule that binds to and stabilizes the receptor in an active conformation, thereby resulting in an intracellular response.

Bioluminescence resonance energy transfer

(BRET). A biophysical technique combining a photon-emitting bioluminescent luciferase and an acceptor fluorescent protein, which is used to monitor changes in intramolecular and intermolecular proximity.

Fluorescence resonance energy transfer

(FRET). A biophysical technique combining a donor chromophore and an acceptor chromophore, which is used to monitor changes in intramolecular and intermolecular proximity.

GPCR kinases

(GRKs). G protein-coupled receptor (GPCR)-regulating protein kinases that phosphorylate intracellular receptor sites and modulate the ability of GPCRs to interact with G proteins and other intracellular transducers.

Transducer mimetic

A non-functional protein such as a camelid nanobody that binds within the transducer-binding cleft of an activated receptor to induce structural reorganization of the receptor similar to that induced by functional transducers (for example, G proteins).

Inhibitory antibody

An antibody directed against a G protein-coupled receptor that inhibits receptor activation.

Protein signalosome

A spatially restricted group of transducers and/or regulatory proteins that jointly produce a specific signalling output.


A chemical description of a molecule that allows identification of the similarities and differences in chemical structure compared with other molecules.

Chemogenetically modified receptors

Genetically engineered receptors that can be chemically modified to be able to alter receptor signalling properties. These include receptors selected for their capacity to interact with previously unrecognized ligands.


A biophysical technique that uses modified, light-activated G protein-coupled receptors or channels to control cells in living tissue.

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Further reading

Fig. 1: Schematic illustration of GPCR signalling.
Fig. 2: Mechanisms of ligand-induced biased agonism.
Fig. 3: Conserved residue contact networks between class A GPCRs and G proteins.
Fig. 4: Conformational changes in class B and class C GPCRs required for G protein coupling.
Fig. 5: Compartmentalization of signalling by GPCRs.