Skip to main content

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

Biased signalling: from simple switches to allosteric microprocessors

Key Points

  • G protein-coupled receptors (GPCRs) adopt multiple conformational states that can activate or block distinct intracellular signalling pathways, such as those regulated by heterotrimeric G proteins or β-arrestins.

  • Different agonists for the same receptor can stabilize distinct GPCR conformational states. Agonists that preferentially activate certain intracellular pathways relative to others are referred to as biased agonists.

  • Structural studies support a model in which GPCRs act as allosteric microprocessors that integrate diverse extracellular and intracellular stimuli to generate distinct conformations that result in varied intracellular responses.

  • In addition to biased agonists, biased signalling may be encoded by the receptor ('receptor bias') or by the relative expression levels of transducers ('system bias').

  • Biased signalling is also observed in other receptor families, such as nuclear hormone receptors and receptor tyrosine kinases.

  • Recent preclinical and clinical work suggests that by more selectively targeting signalling pathways of interest, biased agonists have the potential to increase clinical efficacy while reducing undesirable side effects.

Abstract

G protein-coupled receptors (GPCRs) are the largest class of receptors in the human genome and some of the most common drug targets. It is now well established that GPCRs can signal through multiple transducers, including heterotrimeric G proteins, GPCR kinases and β-arrestins. While these signalling pathways can be activated or blocked by 'balanced' agonists or antagonists, they can also be selectively activated in a 'biased' response. Biased responses can be induced by biased ligands, biased receptors or system bias, any of which can result in preferential signalling through G proteins or β-arrestins. At many GPCRs, signalling events mediated by G proteins and β-arrestins have been shown to have distinct biochemical and physiological actions from one another, and an accurate evaluation of biased signalling from pharmacology through physiology is crucial for preclinical drug development. Recent structural studies have provided snapshots of GPCR–transducer complexes, which should aid in the structure-based design of novel biased therapies. Our understanding of GPCRs has evolved from that of two-state, on-and-off switches to that of multistate allosteric microprocessors, in which biased ligands transmit distinct structural information that is processed into distinct biological outputs. The development of biased ligands as therapeutics heralds an era of increased drug efficacy with reduced drug side effects.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.

from$8.99

All prices are NET prices.

Figure 1: Biased signalling can be encoded through three general mechanisms.
Figure 2: Drug discovery strategies and physiological consequences of biased signalling.
Figure 3: General approach to characterizing biased ligands.

References

  1. 1

    Lagerstrom, M. C. & Schioth, H. B. Structural diversity of G protein-coupled receptors and significance for drug discovery. Nat. Rev. Drug Discov. 7, 339–357 (2008).

    PubMed  PubMed Central  Google Scholar 

  2. 2

    Luttrell, L. M., Maudsley, S. & Bohn, L. M. Fulfilling the promise of “biased” G protein-coupled receptor agonism. Mol. Pharmacol. 88, 579–588 (2015).

    CAS  PubMed  PubMed Central  Google Scholar 

  3. 3

    Santos, R. et al. A comprehensive map of molecular drug targets. Nat. Rev. Drug Discov. 16, 19–34 (2017).

    CAS  PubMed  Google Scholar 

  4. 4

    Smith, J. S. & Rajagopal, S. The β-arrestins: multifunctional regulators of G protein-coupled receptors. J. Biol Chem. 291, 8969–8977 (2016).

    CAS  PubMed  PubMed Central  Google Scholar 

  5. 5

    Benovic, J. L., Strasser, R. H., Caron, M. G. & Lefkowitz, R. J. β-Adrenergic receptor kinase: identification of a novel protein kinase that phosphorylates the agonist-occupied form of the receptor. Proc. Natl Acad. Sci. USA 83, 2797–2801 (1986).

    CAS  PubMed  Google Scholar 

  6. 6

    Lohse, M. J., Benovic, J. L., Codina, J., Caron, M. G. & Lefkowitz, R. J. β-Arrestin: a protein that regulates β-adrenergic receptor function. Science 248, 1547–1550 (1990).

    CAS  Google Scholar 

  7. 7

    Goodman, O. B. Jr et al. β-Arrestin acts as a clathrin adaptor in endocytosis of the β2-adrenergic receptor. Nature 383, 447–450 (1996).

    CAS  Google Scholar 

  8. 8

    Oakley, R. H., Laporte, S. A., Holt, J. A., Barak, L. S. & Caron, M. G. Association of β-arrestin with G protein-coupled receptors during clathrin-mediated endocytosis dictates the profile of receptor resensitization. J. Biol Chem. 274, 32248–32257 (1999).

    CAS  PubMed  Google Scholar 

  9. 9

    Laporte, S. A., Oakley, R. H., Holt, J. A., Barak, L. S. & Caron, M. G. The interaction of β-arrestin with the AP-2 adaptor is required for the clustering of β2-adrenergic receptor into clathrin-coated pits. J. Biol Chem. 275, 23120–23126 (2000). References 7–9 are seminal papers describing the role of β-arrestin in GPCR endocytosis.

    CAS  PubMed  Google Scholar 

  10. 10

    Hanyaloglu, A. C. & von Zastrow, M. Regulation of GPCRs by endocytic membrane trafficking and its potential implications. Annu. Rev. Pharmacol. Toxicol. 48, 537–568 (2008).

    CAS  PubMed  Google Scholar 

  11. 11

    Gao, H. et al. Identification of β-arrestin2 as a G protein-coupled receptor-stimulated regulator of NF-κB pathways. Mol. Cell 14, 303–317 (2004).

    CAS  PubMed  Google Scholar 

  12. 12

    Shenoy, S. K. et al. β-Arrestin-dependent, G protein-independent ERK1/2 activation by the β2 adrenergic receptor. J. Biol Chem. 281, 1261–1273 (2006).

    CAS  PubMed  Google Scholar 

  13. 13

    Beaulieu, J. M. et al. An Akt/β-arrestin 2/PP2A signaling complex mediates dopaminergic neurotransmission and behavior. Cell 122, 261–273 (2005).

    CAS  Google Scholar 

  14. 14

    Luttrell, L. M. et al. β-Arrestin-dependent formation of β2 adrenergic receptor-Src protein kinase complexes. Science 283, 655–661 (1999). This is one of the first studies describing the signalling functions of β-arrestins.

    CAS  PubMed  Google Scholar 

  15. 15

    Ahn, S., Kim, J., Hara, M. R., Ren, X. R. & Lefkowitz, R. J. β-Arrestin-2 mediates anti-apoptotic signaling through regulation of BAD phosphorylation. J. Biol Chem. 284, 8855–8865 (2009).

    CAS  PubMed  PubMed Central  Google Scholar 

  16. 16

    Kendall, R. T. et al. Arrestin-dependent angiotensin AT1 receptor signaling regulates Akt and mTor-mediated protein synthesis. J. Biol Chem. 289, 26155–26166 (2014).

    CAS  PubMed  PubMed Central  Google Scholar 

  17. 17

    Eichel, K., Jullie, D. & von Zastrow, M. β-Arrestin drives MAP kinase signalling from clathrin-coated structures after GPCR dissociation. Nat. Cell Biol. 18, 303–310 (2016).

    CAS  PubMed  PubMed Central  Google Scholar 

  18. 18

    Coffa, S., Breitman, M., Spiller, B. W. & Gurevich, V. V. A single mutation in arrestin-2 prevents ERK1/2 activation by reducing c-Raf1 binding. Biochemistry 50, 6951–6958 (2011).

    CAS  PubMed  PubMed Central  Google Scholar 

  19. 19

    Ferrandon, S. et al. Sustained cyclic AMP production by parathyroid hormone receptor endocytosis. Nat. Chem. Biol. 5, 734–742 (2009).

    CAS  PubMed  PubMed Central  Google Scholar 

  20. 20

    Calebiro, D. et al. Persistent cAMP-signals triggered by internalized G-protein-coupled receptors. PLoS Biol. 7, e1000172 (2009).

    PubMed  PubMed Central  Google Scholar 

  21. 21

    Irannejad, R. et al. Conformational biosensors reveal GPCR signalling from endosomes. Nature 495, 534–538 (2013). References 19–21 are impactful studies demonstrating sustained G protein signalling from endosomes following endocytosis regulated by β-arrestins.

    CAS  PubMed  PubMed Central  Google Scholar 

  22. 22

    Roth, B. L. & Chuang, D. M. Multiple mechanisms of serotonergic signal transduction. Life Sci. 41, 1051–1064 (1987).

    CAS  PubMed  Google Scholar 

  23. 23

    Luttrell, L. M. Minireview: More than just a hammer: ligand “bias” and pharmaceutical discovery. Mol. Endocrinol. 28, 281–294 (2014).

    PubMed  PubMed Central  Google Scholar 

  24. 24

    Jarpe, M. B. et al. [D-Arg1,D-Phe5,D-Trp7,9,Leu11]Substance P acts as a biased agonist toward neuropeptide and chemokine receptors. J. Biol Chem. 273, 3097–3104 (1998).

    CAS  PubMed  Google Scholar 

  25. 25

    Urban, J. D. et al. Functional selectivity and classical concepts of quantitative pharmacology. J. Pharmacol. Exp. Ther. 320, 1–13 (2007).

    CAS  PubMed  Google Scholar 

  26. 26

    Violin, J. D. & Lefkowitz, R. J. β-Arrestin-biased ligands at seven-transmembrane receptors. Trends Pharmacol Sci. 28, 416–422 (2007).

    CAS  PubMed  Google Scholar 

  27. 27

    Spengler, D. et al. Differential signal transduction by five splice variants of the PACAP receptor. Nature 365, 170–175 (1993).

    CAS  PubMed  PubMed Central  Google Scholar 

  28. 28

    Kenakin, T. Agonist-receptor efficacy. II. Agonist trafficking of receptor signals. Trends Pharmacol Sci. 16, 232–238 (1995).

    CAS  PubMed  Google Scholar 

  29. 29

    Gurwitz, D. et al. Discrete activation of transduction pathways associated with acetylcholine m1 receptor by several muscarinic ligands. Eur. J. Pharmacol. 267, 21–31 (1994).

    CAS  PubMed  Google Scholar 

  30. 30

    Wei, H. et al. Independent β-arrestin 2 and G protein-mediated pathways for angiotensin II activation of extracellular signal-regulated kinases 1 and 2. Proc. Natl Acad. Sci. USA 100, 10782–10787 (2003).

    CAS  PubMed  Google Scholar 

  31. 31

    Whalen, E. J., Rajagopal, S. & Lefkowitz, R. J. Therapeutic potential of β-arrestin- and G protein-biased agonists. Trends Mol. Med. 17, 126–139 (2011).

    CAS  PubMed  Google Scholar 

  32. 32

    Violin, J. D., Crombie, A. L., Soergel, D. G. & Lark, M. W. Biased ligands at G-protein-coupled receptors: promise and progress. Trends Pharmacol Sci. 35, 308–316 (2014).

    CAS  PubMed  Google Scholar 

  33. 33

    Wisler, J. W., Xiao, K., Thomsen, A. R. & Lefkowitz, R. J. Recent developments in biased agonism. Curr. Opin. Cell Biol. 27, 18–24 (2014).

    CAS  PubMed  Google Scholar 

  34. 34

    Rajagopal, S., Rajagopal, K. & Lefkowitz, R. J. Teaching old receptors new tricks: biasing seven-transmembrane receptors. Nat. Rev. Drug Discov. 9, 373–386 (2010).

    CAS  PubMed  PubMed Central  Google Scholar 

  35. 35

    Samama, P., Cotecchia, S., Costa, T. & Lefkowitz, R. J. A mutation-induced activated state of the β2-adrenergic receptor. Extending the ternary complex model. J. Biol Chem. 268, 4625–4636 (1993).

    CAS  PubMed  Google Scholar 

  36. 36

    Changeux, J. P. & Edelstein, S. J. Allosteric mechanisms of signal transduction. Science 308, 1424–1428 (2005).

    CAS  PubMed  Google Scholar 

  37. 37

    Kenakin, T. P. Biased signalling and allosteric machines: new vistas and challenges for drug discovery. Br. J. Pharmacol. 165, 1659–1669 (2012).

    CAS  PubMed  PubMed Central  Google Scholar 

  38. 38

    De Lean, A., Stadel, J. M. & Lefkowitz, R. J. A ternary complex model explains the agonist-specific binding properties of the adenylate cyclase-coupled β-adrenergic receptor. J. Biol Chem. 255, 7108–7117 (1980).

    CAS  PubMed  Google Scholar 

  39. 39

    Gentry, P. R., Sexton, P. M. & Christopoulos, A. Novel allosteric modulators of G protein-coupled receptors. J. Biol Chem. 290, 19478–19488 (2015).

    CAS  PubMed  PubMed Central  Google Scholar 

  40. 40

    Onaran, H. O., Rajagopal, S. & Costa, T. What is biased efficacy? Defining the relationship between intrinsic efficacy and free energy coupling. Trends Pharmacol Sci. 35, 639–647 (2014).

    CAS  PubMed  Google Scholar 

  41. 41

    Kenakin, T. Gaddum Memorial Lecture 2014: receptors as an evolving concept: from switches to biased microprocessors. Br. J. Pharmacol. 172, 4238–4253 (2015).

    CAS  PubMed  PubMed Central  Google Scholar 

  42. 42

    Galandrin, S., Oligny-Longpre, G. & Bouvier, M. The evasive nature of drug efficacy: implications for drug discovery. Trends Pharmacol Sci. 28, 423–430 (2007).

    CAS  PubMed  Google Scholar 

  43. 43

    Wardell, S. E., Marks, J. R. & McDonnell, D. P. The turnover of estrogen receptor α by the selective estrogen receptor degrader (SERD) fulvestrant is a saturable process that is not required for antagonist efficacy. Biochem. Pharmacol. 82, 122–130 (2011).

    CAS  PubMed  PubMed Central  Google Scholar 

  44. 44

    Norris, J. D. et al. Peptide antagonists of the human estrogen receptor. Science 285, 744–746 (1999).

    CAS  PubMed  Google Scholar 

  45. 45

    Paige, L. A. et al. Estrogen receptor (ER) modulators each induce distinct conformational changes in ERα and ERβ. Proc. Natl Acad. Sci. USA 96, 3999–4004 (1999).

    CAS  PubMed  Google Scholar 

  46. 46

    Heldring, N. et al. Estrogen receptors: how do they signal and what are their targets. Physiol Rev. 87, 905–931 (2007).

    CAS  PubMed  Google Scholar 

  47. 47

    Kovalenko, M. et al. Phosphorylation site-specific inhibition of platelet-derived growth factor β-receptor autophosphorylation by the receptor blocking tyrphostin AG1296. Biochemistry 36, 6260–6269 (1997).

    CAS  PubMed  Google Scholar 

  48. 48

    Girnita, L. et al. β-Arrestin and Mdm2 mediate IGF-1 receptor-stimulated ERK activation and cell cycle progression. J. Biol Chem. 282, 11329–11338 (2007).

    CAS  PubMed  Google Scholar 

  49. 49

    Arey, B. J. et al. Induction of promiscuous G protein coupling of the follicle-stimulating hormone (FSH) receptor: a novel mechanism for transducing pleiotropic actions of FSH isoforms. Mol. Endocrinol. 11, 517–526 (1997).

    CAS  PubMed  Google Scholar 

  50. 50

    Arey, B. J. et al. Differing pharmacological activities of thiazolidinone analogs at the FSH receptor. Biochem. Biophys. Res. Commun. 368, 723–728 (2008).

    CAS  PubMed  Google Scholar 

  51. 51

    Yanofsky, S. D. et al. Allosteric activation of the follicle-stimulating hormone (FSH) receptor by selective, nonpeptide agonists. J. Biol Chem. 281, 13226–13233 (2006).

    CAS  PubMed  Google Scholar 

  52. 52

    Kjelsberg, M. A., Cotecchia, S., Ostrowski, J., Caron, M. G. & Lefkowitz, R. J. Constitutive activation of the α1B-adrenergic receptor by all amino acid substitutions at a single site. Evidence for a region which constrains receptor activation. J. Biol Chem. 267, 1430–1433 (1992).

    CAS  PubMed  Google Scholar 

  53. 53

    Chen, X., Bai, B., Tian, Y., Du, H. & Chen, J. Identification of serine 348 on the apelin receptor as a novel regulatory phosphorylation site in apelin-13-induced G protein-independent biased signaling. J. Biol Chem. 289, 31173–31187 (2014).

    CAS  PubMed  PubMed Central  Google Scholar 

  54. 54

    Wanka, L. et al. C-Terminal motif of human neuropeptide Y4 receptor determines internalization and arrestin recruitment. Cell. Signal. 29, 233–239 (2017).

    CAS  PubMed  Google Scholar 

  55. 55

    Rajagopal, S. et al. β-Arrestin-but not G protein-mediated signaling by the “decoy” receptor CXCR7. Proc. Natl Acad. Sci. USA 107, 628–632 (2010).

    Google Scholar 

  56. 56

    Levoye, A., Balabanian, K., Baleux, F., Bachelerie, F. & Lagane, B. CXCR7 heterodimerizes with CXCR4 and regulates CXCL12-mediated G protein signaling. Blood 113, 6085–6093 (2009).

    CAS  PubMed  Google Scholar 

  57. 57

    Decaillot, F. M. et al. CXCR7/CXCR4 heterodimer constitutively recruits β-arrestin to enhance cell migration. J. Biol Chem. 286, 32188–32197 (2011).

    CAS  PubMed  PubMed Central  Google Scholar 

  58. 58

    Wang, Y. et al. CXCR4 and CXCR7 have distinct functions in regulating interneuron migration. Neuron 69, 61–76 (2011).

    CAS  PubMed  PubMed Central  Google Scholar 

  59. 59

    Smith, J. S. et al. C-X-C motif chemokine receptor 3 splice variants differentially activate beta-arrestins to regulate downstream signaling pathways. Mol. Pharmacol. 92, 136–150 (2017).

    CAS  PubMed  PubMed Central  Google Scholar 

  60. 60

    Berchiche, Y. A. & Sakmar, T. P. CXC chemokine receptor 3 alternative splice variants selectively activate different signaling pathways. Mol. Pharmacol. 90, 483–495 (2016).

    CAS  PubMed  Google Scholar 

  61. 61

    Armbruster, B. N., Li, X., Pausch, M. H., Herlitze, S. & Roth, B. L. Evolving the lock to fit the key to create a family of G protein-coupled receptors potently activated by an inert ligand. Proc. Natl Acad. Sci. USA 104, 5163–5168 (2007).

    PubMed  PubMed Central  Google Scholar 

  62. 62

    Nakajima, K. & Wess, J. Design and functional characterization of a novel, arrestin-biased designer G protein-coupled receptor. Mol. Pharmacol. 82, 575–582 (2012).

    CAS  PubMed  PubMed Central  Google Scholar 

  63. 63

    Hu, J. et al. A G protein-biased designer G protein-coupled receptor useful for studying the physiological relevance of Gq/11-dependent signaling pathways. J. Biol Chem. 291, 7809–7820 (2016).

    CAS  PubMed  PubMed Central  Google Scholar 

  64. 64

    Siuda, E. R. et al. Optodynamic simulation of beta-adrenergic receptor signalling. Nat. Commun. 6, 8480 (2015).

    CAS  PubMed  PubMed Central  Google Scholar 

  65. 65

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

    CAS  PubMed  Google Scholar 

  66. 66

    Reiter, E. & Lefkowitz, R. J. GRKs and β-arrestins: roles in receptor silencing, trafficking and signaling. Trends Endocrinol. Metab. 17, 159–165 (2006).

    CAS  PubMed  Google Scholar 

  67. 67

    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).

    CAS  PubMed  Google Scholar 

  68. 68

    Riggs, B. L. & Hartmann, L. C. Selective estrogen-receptor modulators — mechanisms of action and application to clinical practice. N. Engl. J. Med. 348, 618–629 (2003).

    CAS  PubMed  Google Scholar 

  69. 69

    Urs, N. M. et al. Distinct cortical and striatal actions of a β-arrestin-biased dopamine D2 receptor ligand reveal unique antipsychotic-like properties. Proc. Natl Acad. Sci. USA 113, E8178–E8186 (2016). This paper presents a physiological example of how system bias can influence β-arrestin signalling.

    CAS  PubMed  Google Scholar 

  70. 70

    Schattauer, S. S., Kuhar, J. R., Song, A. & Chavkin, C. Nalfurafine is a G-protein biased agonist having significantly greater bias at the human than rodent form of the kappa opioid receptor. Cell. Signal. 32, 59–65 (2017).

    CAS  PubMed  PubMed Central  Google Scholar 

  71. 71

    Shenoy, S. K. & Lefkowitz, R. J. β-Arrestin-mediated receptor trafficking and signal transduction. Trends Pharmacol Sci. 32, 521–533 (2011).

    CAS  PubMed  PubMed Central  Google Scholar 

  72. 72

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

    CAS  PubMed  Google Scholar 

  73. 73

    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).

    CAS  PubMed  PubMed Central  Google Scholar 

  74. 74

    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).

    CAS  PubMed  PubMed Central  Google Scholar 

  75. 75

    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). References 72–75 are some of the key papers demonstrating 'barcode' patterns, indicating how site-specific phosphorylation regulates GPCR signalling.

    CAS  PubMed  Google Scholar 

  76. 76

    Poulin, B. et al. The M3-muscarinic receptor regulates learning and memory in a receptor phosphorylation/arrestin-dependent manner. Proc. Natl Acad. Sci. USA 107, 9440–9445 (2010).

    CAS  PubMed  Google Scholar 

  77. 77

    Luo, J., Busillo, J. M., Stumm, R. & Benovic, J. L. G. Protein-coupled receptor kinase 3 and protein kinase C phosphorylate the distal C-terminal tail of the chemokine receptor CXCR4 and mediate recruitment of β-arrestin. Mol. Pharmacol. 91, 554–566 (2017).

    CAS  PubMed  PubMed Central  Google Scholar 

  78. 78

    Shukla, A. K. et al. Distinct conformational changes in β-arrestin report biased agonism at seven-transmembrane receptors. Proc. Natl Acad. Sci. USA 105, 9988–9993 (2008).

    CAS  PubMed  Google Scholar 

  79. 79

    Charest, P. G., Terrillon, S. & Bouvier, M. Monitoring agonist-promoted conformational changes of β-arrestin in living cells by intramolecular BRET. EMBO Rep. 6, 334–340 (2005).

    CAS  PubMed  PubMed Central  Google Scholar 

  80. 80

    Namkung, Y. et al. Monitoring G protein-coupled receptor and β-arrestin trafficking in live cells using enhanced bystander BRET. Nat. Commun. 7, 12178 (2016).

    PubMed  PubMed Central  Google Scholar 

  81. 81

    Lee, M. H. et al. The conformational signature of β-arrestin2 predicts its trafficking and signalling functions. Nature 531, 665–668 (2016).

    CAS  PubMed  PubMed Central  Google Scholar 

  82. 82

    Nuber, S. et al. β-Arrestin biosensors reveal a rapid, receptor-dependent activation/deactivation cycle. Nature 531, 661–664 (2016). References 81 and 82 are studies that link β-arrestin conformation with function.

    CAS  PubMed  PubMed Central  Google Scholar 

  83. 83

    Hernandez, P. A. et al. Mutations in the chemokine receptor gene CXCR4 are associated with WHIM syndrome, a combined immunodeficiency disease. Nat. Genet. 34, 70–74 (2003).

    CAS  PubMed  Google Scholar 

  84. 84

    Balabanian, K. et al. WHIM syndromes with different genetic anomalies are accounted for by impaired CXCR4 desensitization to CXCL12. Blood 105, 2449–2457 (2005).

    CAS  PubMed  Google Scholar 

  85. 85

    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).

    CAS  PubMed  Google Scholar 

  86. 86

    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 paper presents important mechanistic work on how receptor mutants can bias signalling responses.

    CAS  PubMed  PubMed Central  Google Scholar 

  87. 87

    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).

    CAS  PubMed  PubMed Central  Google Scholar 

  88. 88

    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).

    CAS  PubMed  PubMed Central  Google Scholar 

  89. 89

    Cherezov, V. et al. High-resolution crystal structure of an engineered human β2-adrenergic G protein-coupled receptor. Science 318, 1258–1265 (2007).

    CAS  PubMed  PubMed Central  Google Scholar 

  90. 90

    Venkatakrishnan, A. J. et al. Diverse activation pathways in class A GPCRs converge near the G-protein-coupling region. Nature 536, 484–487 (2016).

    CAS  PubMed  PubMed Central  Google Scholar 

  91. 91

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

    CAS  PubMed  Google Scholar 

  92. 92

    Zhang, H. et al. Structure of the Angiotensin receptor revealed by serial femtosecond crystallography. Cell 161, 833–844 (2015).

    CAS  PubMed  PubMed Central  Google Scholar 

  93. 93

    Zhang, H. et al. Structural basis for ligand recognition and functional selectivity at angiotensin receptor. J. Biol Chem. 290, 29127–29139 (2015).

    CAS  PubMed  PubMed Central  Google Scholar 

  94. 94

    Choe, H. W. et al. Crystal structure of metarhodopsin II. Nature 471, 651–655 (2011).

    CAS  Google Scholar 

  95. 95

    Standfuss, J. et al. The structural basis of agonist-induced activation in constitutively active rhodopsin. Nature 471, 656–660 (2011).

    CAS  PubMed  PubMed Central  Google Scholar 

  96. 96

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

    CAS  PubMed  PubMed Central  Google Scholar 

  97. 97

    Jaakola, V. P. et al. The 2.6 angstrom crystal structure of a human A2A adenosine receptor bound to an antagonist. Science 322, 1211–1217 (2008).

    CAS  PubMed  PubMed Central  Google Scholar 

  98. 98

    Xu, F. et al. Structure of an agonist-bound human A2A adenosine receptor. Science 332, 322–327 (2011).

    CAS  PubMed  PubMed Central  Google Scholar 

  99. 99

    Kruse, A. C. et al. Activation and allosteric modulation of a muscarinic acetylcholine receptor. Nature 504, 101–106 (2013).

    CAS  PubMed  PubMed Central  Google Scholar 

  100. 100

    Manglik, A. et al. Crystal structure of the micro-opioid receptor bound to a morphinan antagonist. Nature 485, 321–326 (2012).

    CAS  PubMed  PubMed Central  Google Scholar 

  101. 101

    Huang, W. et al. Structural insights into micro-opioid receptor activation. Nature 524, 315–321 (2015).

    CAS  PubMed  PubMed Central  Google Scholar 

  102. 102

    Zheng, Y. et al. Structure of CC chemokine receptor 2 with orthosteric and allosteric antagonists. Nature 540, 458–461 (2016).

    CAS  PubMed  PubMed Central  Google Scholar 

  103. 103

    Oswald, C. et al. Intracellular allosteric antagonism of the CCR9 receptor. Nature 540, 462–465 (2016).

    CAS  Google Scholar 

  104. 104

    Hollenstein, K. et al. Structure of class B GPCR corticotropin-releasing factor receptor 1. Nature 499, 438–443 (2013).

    CAS  Google Scholar 

  105. 105

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

    CAS  Google Scholar 

  106. 106

    Rasmussen, S. G. et al. Crystal structure of the β2 adrenergic receptor-Gs protein complex. Nature 477, 549–555 (2011).

    CAS  PubMed  PubMed Central  Google Scholar 

  107. 107

    Liang, Y. L. et al. Phase-plate cryo-EM structure of a class B GPCR-G-protein complex. Nature 546, 118–123 (2017).

    CAS  PubMed  PubMed Central  Google Scholar 

  108. 108

    Zhang, Y. et al. Cryo-EM structure of the activated GLP-1 receptor in complex with a G protein. Nature 546, 248–253 (2017). References 107 and 108 are structural studies utilizing cryo-EM to solve GPCR structures in complex with G proteins. Cryo-EM technology will likely play an important role in providing critical structural insights into biased signalling.

    CAS  PubMed  PubMed Central  Google Scholar 

  109. 109

    Zhang, H. et al. Structural basis for selectivity and diversity in angiotensin II receptors. Nature 544, 327–332 (2017).

    CAS  PubMed  PubMed Central  Google Scholar 

  110. 110

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

    CAS  PubMed  PubMed Central  Google Scholar 

  111. 111

    Carpenter, B., Nehme, R., Warne, T., Leslie, A. G. & Tate, C. G. Structure of the adenosine A2A receptor bound to an engineered G protein. Nature 536, 104–107 (2016).

    CAS  PubMed  PubMed Central  Google Scholar 

  112. 112

    Staus, D. P. et al. Allosteric nanobodies reveal the dynamic range and diverse mechanisms of G-protein-coupled receptor activation. Nature 535, 448–452 (2016).

    CAS  PubMed  PubMed Central  Google Scholar 

  113. 113

    Kim, Y. J. et al. Crystal structure of pre-activated arrestin p44. Nature 497, 142–146 (2013).

    CAS  Google Scholar 

  114. 114

    Kang, Y. et al. Crystal structure of rhodopsin bound to arrestin by femtosecond X-ray laser. Nature 523, 561–567 (2015).

    CAS  PubMed  PubMed Central  Google Scholar 

  115. 115

    Szczepek, M. et al. Crystal structure of a common GPCR-binding interface for G protein and arrestin. Nat. Commun. 5, 4801 (2014).

    CAS  PubMed  PubMed Central  Google Scholar 

  116. 116

    Renaud, J. P. et al. Biophysics in drug discovery: impact, challenges and opportunities. Nat. Rev. Drug Discov. 15, 679–698 (2016).

    CAS  PubMed  PubMed Central  Google Scholar 

  117. 117

    Westfield, G. H. et al. Structural flexibility of the Gαs α-helical domain in the β2-adrenoceptor Gs complex. Proc. Natl Acad. Sci. USA 108, 16086–16091 (2011).

    CAS  PubMed  Google Scholar 

  118. 118

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

    CAS  PubMed  PubMed Central  Google Scholar 

  119. 119

    Kumari, P. et al. Functional competence of a partially engaged GPCR-β-arrestin complex. Nat. Commun. 7, 13416 (2016).

    CAS  PubMed  PubMed Central  Google Scholar 

  120. 120

    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).

    CAS  PubMed  Google Scholar 

  121. 121

    Thomsen, A. R. et al. GPCR-G protein-β-arrestin super-complex mediates sustained G protein signaling. Cell 166, 907–919 (2016). This is a negative stain EM study that provides a potential structural basis for how β-arrestin and G proteins can orchestrate prolonged intracellular GPCR signalling.

    CAS  PubMed  PubMed Central  Google Scholar 

  122. 122

    Kahsai, A. W. et al. Multiple ligand-specific conformations of the β2-adrenergic receptor. Nat. Chem. Biol. 7, 692–700 (2011).

    CAS  PubMed  PubMed Central  Google Scholar 

  123. 123

    Isogai, S. et al. Backbone NMR reveals allosteric signal transduction networks in the β1-adrenergic receptor. Nature 530, 237–241 (2016).

    CAS  PubMed  Google Scholar 

  124. 124

    Perez-Aguilar, J. M., Shan, J., LeVine, M. V., Khelashvili, G. & Weinstein, H. A functional selectivity mechanism at the serotonin-2A GPCR involves ligand-dependent conformations of intracellular loop 2. J. Am. Chem. Soc. 136, 16044–16054 (2014).

    CAS  PubMed  PubMed Central  Google Scholar 

  125. 125

    Kim, I. M. et al. β-Blockers alprenolol and carvedilol stimulate β-arrestin-mediated EGFR transactivation. Proc. Natl Acad. Sci. USA 105, 14555–14560 (2008).

    CAS  PubMed  Google Scholar 

  126. 126

    Kim, I. M. et al. β-Arrestin1-biased β1-adrenergic receptor signaling regulates microRNA processing. Circ. Res. 114, 833–844 (2014).

    CAS  PubMed  Google Scholar 

  127. 127

    Wisler, J. W. et al. A unique mechanism of β-blocker action: carvedilol stimulates β-arrestin signaling. Proc. Natl Acad. Sci. USA 104, 16657–16662 (2007).

    CAS  Google Scholar 

  128. 128

    Liu, J. J., Horst, R., Katritch, V., Stevens, R. C. & Wuthrich, K. Biased signaling pathways in β2-adrenergic receptor characterized by 19F-NMR. Science 335, 1106–1110 (2012).

    CAS  PubMed  PubMed Central  Google Scholar 

  129. 129

    Kahsai, A. W. et al. Conformationally selective RNA aptamers allosterically modulate the β2-adrenoceptor. Nat. Chem. Biol. 12, 709–716 (2016).

    CAS  PubMed  PubMed Central  Google Scholar 

  130. 130

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

    CAS  PubMed  PubMed Central  Google Scholar 

  131. 131

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

    CAS  PubMed  PubMed Central  Google Scholar 

  132. 132

    Mary, S. et al. Ligands and signaling proteins govern the conformational landscape explored by a G protein-coupled receptor. Proc. Natl Acad. Sci. USA 109, 8304–8309 (2012).

    CAS  PubMed  Google Scholar 

  133. 133

    Wacker, D. et al. Structural features for functional selectivity at serotonin receptors. Science 340, 615–619 (2013).

    CAS  PubMed  PubMed Central  Google Scholar 

  134. 134

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

    PubMed  PubMed Central  Google Scholar 

  135. 135

    Ariens, E. J. Affinity and intrinsic activity in the theory of competitive inhibition. I. Problems and theory. Arch. Intern. Pharmacodynamie Therapie 99, 32–49 (1954).

    CAS  Google Scholar 

  136. 136

    Stephenson, R. P. A modification of receptor theory. Br. J. Pharmacol. Chemother. 11, 379–393 (1956).

    CAS  PubMed  PubMed Central  Google Scholar 

  137. 137

    Furchgott, R. F. in in Advances in Drug Research Vol. 3 (eds Harper, N. J. & Simmonds, A. B.) 21–55 (Academic Press, 1966).

    Google Scholar 

  138. 138

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

    CAS  PubMed  Google Scholar 

  139. 139

    Rajagopal, S. et al. Quantifying ligand bias at seven-transmembrane receptors. Mol. Pharmacol. 80, 367–377 (2011).

    CAS  PubMed  PubMed Central  Google Scholar 

  140. 140

    Kenakin, T., Watson, C., Muniz-Medina, V., Christopoulos, A. & Novick, S. A simple method for quantifying functional selectivity and agonist bias. ACS Chem. Neurosci. 3, 193–203 (2012).

    CAS  PubMed  Google Scholar 

  141. 141

    Griffin, M. T., Figueroa, K. W., Liller, S. & Ehlert, F. J. Estimation of agonist activity at G protein-coupled receptors: analysis of M2 muscarinic receptor signaling through Gi/o, Gs, and G15 . J. Pharmacol. Exp. Ther. 321, 1193–1207 (2007).

    CAS  PubMed  Google Scholar 

  142. 142

    Snyder, J. C., Rochelle, L. K., Lyerly, H. K., Caron, M. G. & Barak, L. S. Constitutive internalization of the leucine-rich G protein-coupled receptor-5 (LGR5) to the trans-Golgi network. J. Biol Chem. 288, 10286–10297 (2013).

    CAS  PubMed  PubMed Central  Google Scholar 

  143. 143

    Onaran, H. O. et al. Systematic errors in detecting biased agonism: analysis of current methods and development of a new model-free approach. Sci. Rep. 7, 44247 (2017). This is a detailed comparison of different methods to quantify biased signalling.

    CAS  PubMed  PubMed Central  Google Scholar 

  144. 144

    Gregory, K. J., Hall, N. E., Tobin, A. B., Sexton, P. M. & Christopoulos, A. Identification of orthosteric and allosteric site mutations in M2 muscarinic acetylcholine receptors that contribute to ligand-selective signaling bias. J. Biol Chem. 285, 7459–7474 (2010).

    CAS  PubMed  PubMed Central  Google Scholar 

  145. 145

    Strachan, R. T. et al. Divergent transducer-specific molecular efficacies generate biased agonism at a G protein-coupled receptor (GPCR). J. Biol. Chem. 289, 14211–14224 (2014).

    CAS  PubMed  PubMed Central  Google Scholar 

  146. 146

    Moffat, J. G., Vincent, F., Lee, J. A., Eder, J. & Prunotto, M. Opportunities and challenges in phenotypic drug discovery: an industry perspective. Nat. Rev. Drug Discov. 16, 531–543 (2017).

    CAS  PubMed  Google Scholar 

  147. 147

    Jones, L. H. & Bunnage, M. E. Applications of chemogenomic library screening in drug discovery. Nat. Rev. Drug Discov. 16, 285–296 (2017).

    CAS  PubMed  Google Scholar 

  148. 148

    Horvath, P. et al. Screening out irrelevant cell-based models of disease. Nat. Rev. Drug Discov. 15, 751–769 (2016).

    CAS  PubMed  Google Scholar 

  149. 149

    Swinney, D. C. & Anthony, J. How were new medicines discovered? Nat. Rev. Drug Discov. 10, 507–519 (2011).

    CAS  Google Scholar 

  150. 150

    Whistler, J. L., Chuang, H. H., Chu, P., Jan, L. Y. & von Zastrow, M. Functional dissociation of mu opioid receptor signaling and endocytosis: implications for the biology of opiate tolerance and addiction. Neuron 23, 737–746 (1999).

    CAS  PubMed  Google Scholar 

  151. 151

    Zhang, J. et al. Role for G protein-coupled receptor kinase in agonist-specific regulation of μ-opioid receptor responsiveness. Proc. Natl Acad. Sci. USA 95, 7157–7162 (1998).

    CAS  PubMed  Google Scholar 

  152. 152

    Melief, E. J., Miyatake, M., Bruchas, M. R. & Chavkin, C. Ligand-directed c-Jun N-terminal kinase activation disrupts opioid receptor signaling. Proc. Natl Acad. Sci. USA 107, 11608–11613 (2010).

    CAS  PubMed  Google Scholar 

  153. 153

    Bohn, L. M., Gainetdinov, R. R., Lin, F. T., Lefkowitz, R. J. & Caron, M. G. μ-Opioid receptor desensitization by β-arrestin-2 determines morphine tolerance but not dependence. Nature 408, 720–723 (2000).

    CAS  PubMed  Google Scholar 

  154. 154

    Bohn, L. M. et al. Enhanced morphine analgesia in mice lacking β-arrestin 2. Science 286, 2495–2498 (1999).

    CAS  PubMed  Google Scholar 

  155. 155

    Groer, C. E. et al. An opioid agonist that does not induce μ-opioid receptor-arrestin interactions or receptor internalization. Mol. Pharmacol. 71, 549–557 (2007).

    CAS  PubMed  Google Scholar 

  156. 156

    Soergel, D. G. et al. Biased agonism of the μ-opioid receptor by TRV130 increases analgesia and reduces on-target adverse effects versus morphine: a randomized, double-blind, placebo-controlled, crossover study in healthy volunteers. Pain 155, 1829–1835 (2014).

    CAS  PubMed  Google Scholar 

  157. 157

    Viscusi, E. R. et al. A randomized, phase 2 study investigating TRV130, a biased ligand of the μ-opioid receptor, for the intravenous treatment of acute pain. Pain 157, 264–272 (2016).

    CAS  PubMed  Google Scholar 

  158. 158

    Manglik, A. et al. Structure-based discovery of opioid analgesics with reduced side effects. Nature 537, 185–190 (2016). This is a manuscript describing the design of a biased agonist, from a structure-based approach to physiological effects.

    CAS  PubMed  PubMed Central  Google Scholar 

  159. 159

    Land, B. B. et al. The dysphoric component of stress is encoded by activation of the dynorphin κ-opioid system. J. Neurosci. 28, 407–414 (2008).

    CAS  PubMed  PubMed Central  Google Scholar 

  160. 160

    White, K. L. & Roth, B. L. Psychotomimetic effects of kappa opioid receptor agonists. Biol Psychiatry 72, 797–798 (2012).

    CAS  PubMed  Google Scholar 

  161. 161

    Bruchas, M. R. et al. Selective p38α MAPK deletion in serotonergic neurons produces stress resilience in models of depression and addiction. Neuron 71, 498–511 (2011).

    CAS  PubMed  PubMed Central  Google Scholar 

  162. 162

    Land, B. B. et al. Activation of the kappa opioid receptor in the dorsal raphe nucleus mediates the aversive effects of stress and reinstates drug seeking. Proc. Natl Acad. Sci. USA 106, 19168–19173 (2009).

    CAS  PubMed  Google Scholar 

  163. 163

    Ehrich, J. M. et al. Kappa opioid receptor-induced aversion requires p38 MAPK activation in VTA dopamine neurons. J. Neurosci. 35, 12917–12931 (2015).

    CAS  PubMed  PubMed Central  Google Scholar 

  164. 164

    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).

    PubMed  PubMed Central  Google Scholar 

  165. 165

    White, K. L. et al. The G protein-biased κ-opioid receptor agonist RB-64 is analgesic with a unique spectrum of activities in vivo. J. Pharmacol. Exp. Ther. 352, 98–109 (2015).

    PubMed  PubMed Central  Google Scholar 

  166. 166

    Maillet, E. L. et al. Noribogaine is a G-protein biased κ-opioid receptor agonist. Neuropharmacology 99, 675–688 (2015).

    CAS  PubMed  Google Scholar 

  167. 167

    White, K. L. et al. Identification of novel functionally selective κ-opioid receptor scaffolds. Mol. Pharmacol. 85, 83–90 (2014).

    PubMed  PubMed Central  Google Scholar 

  168. 168

    Rives, M. L., Rossillo, M., Liu-Chen, L. Y. & Javitch, J. A. 6′-Guanidinonaltrindole (6′-GNTI) is a G protein-biased κ-opioid receptor agonist that inhibits arrestin recruitment. J. Biol Chem. 287, 27050–27054 (2012).

    CAS  PubMed  PubMed Central  Google Scholar 

  169. 169

    Lovell, K. M. et al. Structure-activity relationship studies of functionally selective kappa opioid receptor agonists that modulate ERK 1/2 phosphorylation while preserving G protein over βarrestin2 signaling bias. ACS Chem. Neurosci. 6, 1411–1419 (2015).

    CAS  PubMed  PubMed Central  Google Scholar 

  170. 170

    Zhou, L. et al. Development of functionally selective, small molecule agonists at kappa opioid receptors. J. Biol Chem. 288, 36703–36716 (2013).

    CAS  PubMed  PubMed Central  Google Scholar 

  171. 171

    Melief, E. J. et al. Duration of action of a broad range of selective κ-opioid receptor antagonists is positively correlated with c-Jun N-terminal kinase-1 activation. Mol. Pharmacol. 80, 920–929 (2011).

    CAS  PubMed  PubMed Central  Google Scholar 

  172. 172

    Munro, T. A. et al. Long-acting kappa opioid antagonists nor-BNI, GNTI and JDTic: pharmacokinetics in mice and lipophilicity. BMC Pharmacol. 12, 5 (2012).

    CAS  PubMed  PubMed Central  Google Scholar 

  173. 173

    Carroll, F. I. & Carlezon, W. A. Jr. Development of kappa opioid receptor antagonists. J. Med. Chem. 56, 2178–2195 (2013).

    CAS  PubMed  PubMed Central  Google Scholar 

  174. 174

    Chavkin, C. & Koob, G. F. Dynorphin, dysphoria, and dependence: the stress of addiction. Neuropsychopharmacology 41, 373–374 (2016).

    CAS  PubMed  Google Scholar 

  175. 175

    Van't Veer, A. & Carlezon, W. A. Jr. Role of κ-opioid receptors in stress and anxiety-related behavior. Psychopharmacology 229, 435–452 (2013).

    CAS  PubMed  PubMed Central  Google Scholar 

  176. 176

    Howes, O. D. & Kapur, S. The dopamine hypothesis of schizophrenia: version III — the final common pathway. Schizophr. Bull. 35, 549–562 (2009).

    PubMed  PubMed Central  Google Scholar 

  177. 177

    Free, R. B. et al. Discovery and characterization of a G protein-biased agonist that inhibits β-arrestin recruitment to the D2 dopamine receptor. Mol. Pharmacol. 86, 96–105 (2014).

    PubMed  PubMed Central  Google Scholar 

  178. 178

    Shonberg, J. et al. A structure-activity analysis of biased agonism at the dopamine D2 receptor. J. Med. Chem. 56, 9199–9221 (2013).

    CAS  PubMed  Google Scholar 

  179. 179

    Chen, X. et al. Structure-functional selectivity relationship studies of β-arrestin-biased dopamine D2 receptor agonists. J. Med. Chem. 55, 7141–7153 (2012).

    CAS  PubMed  PubMed Central  Google Scholar 

  180. 180

    Allen, J. A. et al. Discovery of β-arrestin-biased dopamine D2 ligands for probing signal transduction pathways essential for antipsychotic efficacy. Proc. Natl Acad. Sci. USA 108, 18488–18493 (2011).

    CAS  PubMed  Google Scholar 

  181. 181

    Park, S. M. et al. Effects of β-arrestin-biased dopamine D2 receptor ligands on schizophrenia-like behavior in hypoglutamatergic mice. Neuropsychopharmacology 41, 704–715 (2016).

    CAS  PubMed  Google Scholar 

  182. 182

    Urs, N. M., Peterson, S. M. & Caron, M. G. New concepts in dopamine D2 receptor biased signaling and implications for schizophrenia therapy. Biol Psychiatry 81, 78–85 (2016).

    PubMed  PubMed Central  Google Scholar 

  183. 183

    Sexton, P. M., Findlay, D. M. & Martin, T. J. Calcitonin. Curr. Med. Chem. 6, 1067–1093 (1999).

    CAS  PubMed  Google Scholar 

  184. 184

    Andreassen, K. V. et al. Prolonged calcitonin receptor signaling by salmon, but not human calcitonin, reveals ligand bias. PLoS ONE 9, e92042 (2014).

    PubMed  PubMed Central  Google Scholar 

  185. 185

    Furness, S. G. et al. Ligand-dependent modulation of G protein conformation alters drug efficacy. Cell 167, 739–749.e11 (2016).

    CAS  PubMed  Google Scholar 

  186. 186

    Bachelerie, F. et al. International Union of Basic and Clinical Pharmacology. LXXXIX. Update on the extended family of chemokine receptors and introducing a new nomenclature for atypical chemokine receptors. Pharmacol Rev. 66, 1–79 (2014).

    PubMed  PubMed Central  Google Scholar 

  187. 187

    Steen, A., Larsen, O., Thiele, S. & Rosenkilde, M. M. Biased and G protein-independent signaling of chemokine receptors. Front. Immunol. 5, 277 (2014).

    PubMed  PubMed Central  Google Scholar 

  188. 188

    Muller, M., Carter, S., Hofer, M. J. & Campbell, I. L. Review: The chemokine receptor CXCR3 and its ligands CXCL9, CXCL10 and CXCL11 in neuroimmunity — a tale of conflict and conundrum. Neuropathol. Appl. Neurobiol. 36, 368–387 (2010).

    CAS  PubMed  Google Scholar 

  189. 189

    Groom, J. R. & Luster, A. D. CXCR3 ligands: redundant, collaborative and antagonistic functions. Immunol. Cell Biol. 89, 207–215 (2011).

    CAS  Google Scholar 

  190. 190

    Rashighi, M. et al. CXCL10 is critical for the progression and maintenance of depigmentation in a mouse model of vitiligo. Sci. Transl Med. 6, 223ra23 (2014).

    PubMed  PubMed Central  Google Scholar 

  191. 191

    Rajagopal, S. et al. Biased agonism as a mechanism for differential signaling by chemokine receptors. J. Biol Chem. 288, 35039–35048 (2013).

    CAS  PubMed  PubMed Central  Google Scholar 

  192. 192

    Zohar, Y. et al. CXCL11-dependent induction of FOXP3-negative regulatory T cells suppresses autoimmune encephalomyelitis. J. Clin. Invest. 124, 2009–2022 (2014).

    CAS  PubMed  PubMed Central  Google Scholar 

  193. 193

    Kohout, T. A. et al. Differential desensitization, receptor phosphorylation, β-arrestin recruitment, and ERK1/2 activation by the two endogenous ligands for the CC chemokine receptor 7. J. Biol Chem. 279, 23214–23222 (2004).

    CAS  PubMed  Google Scholar 

  194. 194

    Drury, L. J. et al. Monomeric and dimeric CXCL12 inhibit metastasis through distinct CXCR4 interactions and signaling pathways. Proc. Natl Acad. Sci. USA 108, 17655–17660 (2011).

    CAS  PubMed  Google Scholar 

  195. 195

    Corbisier, J., Gales, C., Huszagh, A., Parmentier, M. & Springael, J. Y. Biased signaling at chemokine receptors. J. Biol Chem. 290, 9542–9554 (2015).

    CAS  PubMed  PubMed Central  Google Scholar 

  196. 196

    Corbisier, J., Huszagh, A., Gales, C., Parmentier, M. & Springael, J. Y. Partial agonist and biased signaling properties of the synthetic enantiomers J113863/UCB35625 at chemokine receptors CCR2 and CCR5. J. Biol Chem. 292, 575–584 (2016).

    PubMed  PubMed Central  Google Scholar 

  197. 197

    Felker, G. M. et al. Heart failure therapeutics on the basis of a biased ligand of the angiotensin-2 type 1 receptor. Rationale and design of the BLAST-AHF study (Biased Ligand of the Angiotensin Receptor Study in Acute Heart Failure). JACC Heart Fail. 3, 193–201 (2015).

    PubMed  Google Scholar 

  198. 198

    Abraham, D. M. et al. β-Arrestin mediates the Frank-Starling mechanism of cardiac contractility. Proc. Natl Acad. Sci. USA 113, 14426–14431 (2016).

    CAS  PubMed  Google Scholar 

  199. 199

    Liu, C. H. et al. Arrestin-biased AT1R agonism induces acute catecholamine secretion through TRPC3 coupling. Nat. Commun. 8, 14335 (2017).

    CAS  PubMed  PubMed Central  Google Scholar 

  200. 200

    Donato, M. & Gelpi, R. J. Adenosine and cardioprotection during reperfusion — an overview. Mol. Cell. Biochem. 251, 153–159 (2003).

    CAS  PubMed  Google Scholar 

  201. 201

    Welihinda, A. A., Kaur, M., Greene, K., Zhai, Y. & Amento, E. P. The adenosine metabolite inosine is a functional agonist of the adenosine A2A receptor with a unique signaling bias. Cell. Signal. 28, 552–560 (2016).

    CAS  PubMed  PubMed Central  Google Scholar 

  202. 202

    Vecchio, E. A. et al. The hybrid molecule, VCP746, is a potent adenosine A2B receptor agonist that stimulates anti-fibrotic signalling. Biochem. Pharmacol. 117, 46–56 (2016).

    CAS  PubMed  Google Scholar 

  203. 203

    Aurelio, L. et al. Allosteric modulators of the adenosine A1 receptor: synthesis and pharmacological evaluation of 4-substituted 2-amino-3-benzoylthiophenes. J. Med. Chem. 52, 4543–4547 (2009).

    CAS  PubMed  Google Scholar 

  204. 204

    Valant, C. et al. Separation of on-target efficacy from adverse effects through rational design of a bitopic adenosine receptor agonist. Proc. Natl Acad. Sci. USA 111, 4614–4619 (2014).

    CAS  PubMed  Google Scholar 

  205. 205

    Chuo, C. H. et al. VCP746, a novel A1 adenosine receptor biased agonist, reduces hypertrophy in a rat neonatal cardiac myocyte model. Clin. Exp. Pharmacol. Physiol. 43, 976–982 (2016).

    CAS  PubMed  Google Scholar 

  206. 206

    Baltos, J. A. et al. Structure-activity analysis of biased agonism at the human adenosine A3 receptor. Mol. Pharmacol. 90, 12–22 (2016).

    CAS  PubMed  PubMed Central  Google Scholar 

  207. 207

    Barak, L. S. et al. ML314: a biased neurotensin receptor ligand for methamphetamine abuse. ACS Chem. Biol. 11, 1880–1890 (2016).

    CAS  PubMed  PubMed Central  Google Scholar 

  208. 208

    Peddibhotla, S. et al. Discovery of ML314, a brain penetrant non-peptidic β-arrestin biased agonist of the neurotensin NTR1 receptor. ACS Med. Chem. Lett. 4, 846–851 (2013).

    CAS  PubMed  PubMed Central  Google Scholar 

  209. 209

    Quoyer, J. et al. Pepducin targeting the C-X-C chemokine receptor type 4 acts as a biased agonist favoring activation of the inhibitory G protein. Proc. Natl Acad. Sci. USA 110, E5088–E5097 (2013).

    CAS  PubMed  Google Scholar 

  210. 210

    Wacker, D. et al. Crystal structure of an LSD-bound human serotonin receptor. Cell 168, 377–389.e12 (2017).

    CAS  PubMed  PubMed Central  Google Scholar 

  211. 211

    Mallipeddi, S., Janero, D. R., Zvonok, N. & Makriyannis, A. Functional selectivity at G-protein coupled receptors: advancing cannabinoid receptors as drug targets. Biochem. Pharmacol. 128, 1–11 (2016).

    PubMed  PubMed Central  Google Scholar 

  212. 212

    Ahn, K. H., Mahmoud, M. M., Shim, J. Y. & Kendall, D. A. Distinct roles of β-arrestin 1 and β-arrestin 2 in ORG27569-induced biased signaling and internalization of the cannabinoid receptor 1 (CB1). J. Biol Chem. 288, 9790–9800 (2013).

    CAS  PubMed  PubMed Central  Google Scholar 

  213. 213

    Fay, J. F. & Farrens, D. L. Structural dynamics and energetics underlying allosteric inactivation of the cannabinoid receptor CB1. Proc. Natl Acad. Sci. USA 112, 8469–8474 (2015).

    CAS  PubMed  Google Scholar 

  214. 214

    Mancini, A. D. et al. β-Arrestin recruitment and biased agonism at free fatty acid receptor 1. J. Biol Chem. 290, 21131–21140 (2015).

    CAS  PubMed  PubMed Central  Google Scholar 

  215. 215

    Christopoulos, A. Advances in G protein-coupled receptor allostery: from function to structure. Mol. Pharmacol. 86, 463–478 (2014).

    PubMed  Google Scholar 

  216. 216

    Kenakin, T. & Christopoulos, A. Signalling bias in new drug discovery: detection, quantification and therapeutic impact. Nat. Rev. Drug Discov. 12, 205–216 (2013).

    CAS  PubMed  PubMed Central  Google Scholar 

  217. 217

    Rajagopal, S. Quantifying biased agonism: understanding the links between affinity and efficacy. Nat. Rev. Drug Discov. 12, 483 (2013).

    CAS  PubMed  Google Scholar 

  218. 218

    Kenakin, T. & Christopoulos, A. Measurements of ligand bias and functional affinity. Nat. Rev. Drug Discov. 12, 483 (2013).

    CAS  PubMed  Google Scholar 

  219. 219

    Breton, B. et al. Multiplexing of multicolor bioluminescence resonance energy transfer. Biophys. J. 99, 4037–4046 (2010).

    CAS  PubMed  PubMed Central  Google Scholar 

  220. 220

    Kroeze, W. K. et al. PRESTO-Tango as an open-source resource for interrogation of the druggable human GPCRome. Nat. Struct. Mol. Biol. 22, 362–369 (2015).

    CAS  PubMed  PubMed Central  Google Scholar 

  221. 221

    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).

    CAS  PubMed  PubMed Central  Google Scholar 

  222. 222

    Barak, L. S., Ferguson, S. S., Zhang, J. & Caron, M. G. A β-arrestin/green fluorescent protein biosensor for detecting G protein-coupled receptor activation. J. Biol Chem. 272, 27497–27500 (1997).

    CAS  PubMed  Google Scholar 

  223. 223

    Inoue, A. et al. TGFα shedding assay: an accurate and versatile method for detecting GPCR activation. Nat. Methods 9, 1021–1029 (2012).

    CAS  PubMed  Google Scholar 

Download references

Acknowledgements

The authors thank J. Silverman for helpful discussion on error propagation and for design and implementation of the online biased calculator resource. We thank T. Pack, M. Caron and C. Chavkin for comments on sections of the manuscript. This work is supported by NIH Grants T32GM7171 (J.S.S.), HL16037 (R.J.L.), HL114643 (S.R.) and GM122798 (S.R.); the Duke Medical Scientist Training Program (J.S.S.); a Burroughs Wellcome Career Award for Medical Scientists (S.R.). R.J.L. is an HHMI Investigator.

Author information

Affiliations

Authors

Corresponding authors

Correspondence to Robert J. Lefkowitz or Sudarshan Rajagopal.

Ethics declarations

Competing interests

R.J.L. is a co-founder and shareholder of Trevena.

Related links

FURTHER INFORMATION

Biased Ligand Calculator

PowerPoint slides

Glossary

G protein-coupled receptor kinases

(GRKs). A family of serine/threonine kinases that phosphorylate the intracellular residues of a G protein-coupled receptor following agonist binding, which is often required for β-arrestin recruitment and signalling.

β-Arrestins

Multifunctional adaptor proteins that regulate G protein-coupled receptor (GPCR) signalling through desensitization and internalization and by promoting signalling through a wide variety of pathways. They also regulate non-GPCR targets, such as receptor tyrosine kinases.

Efficacy

The ability of a ligand to generate a quantifiable response after binding to a receptor.

Affinity

A measurement of how well a ligand binds to a receptor, commonly expressed in terms of a dissociation constant (Kd). Affinity depends on cellular context, and therefore affinity for a G protein-coupled receptor is influenced by transducers, such as G proteins and β-arrestins.

Ligand bias

Biased signalling encoded in the ligand that generates a distinct ligand–receptor conformation relative to a reference ligand.

Allosteric modulators

Ligands that bind to an allosteric site of the receptor and affect receptor responses to orthosteric ligands. Some allosteric modulators are capable of generating biased responses.

Biased agonists

Ligands that selectively enhance or attenuate some, but not all, of the signalling pathways available to a receptor compared with a reference ligand (usually an endogenous agonist).

Receptor bias

Biased signalling encoded by differences in receptor structure or conformation compared with the 'wild-type' receptor.

System bias

Biased signalling directed by the relative expression of receptor transducers, such as increased expression of G proteins, G protein-coupled receptor kinases and/or β-arrestins.

Orthosteric site

The site on a receptor to which the endogenous ligand binds.

Allosteric site

A binding site on a receptor that is different from the orthosteric site.

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Smith, J., Lefkowitz, R. & Rajagopal, S. Biased signalling: from simple switches to allosteric microprocessors. Nat Rev Drug Discov 17, 243–260 (2018). https://doi.org/10.1038/nrd.2017.229

Download citation

Further reading

Search

Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing