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.

  • Review Article
  • Published:

A guide to drug discovery

Predicting therapeutic value in the lead optimization phase of drug discovery

Nature Reviews Drug Discovery volume 2, pages 429–438 (2003)Cite this article

Key Points

  • In vitro lead optimization cellular assays are used to refine initial lead molecules obtained from screening. This allows characterization of molecular activity on receptor genotypes.

  • However, there is increasing evidence that cells impose a phenotypic selectivity to molecules in various cellular backgrounds opening the possibility of dissimulations between activity seen in lead optimization assays and the intended therapeutic value in humans.

  • Specifically, the differences in in vitro assays and the therapeutic environment can come about if the receptor interacts with more than one G-protein (pleiotropic G-protein coupling) and especially if ligands induce ligand-specific receptor conformations that differentially interact with these G-proteins; both of these conditions have been shown to occur with numerous GPCRs.

  • In addition, GPCR activities beyond G-protein coupling and the production of physiological response have been observed (some of these are therapeutically relevant — for example, receptor internalization to inhibit HIV infection), and these also have been seen to behave phenotypically in various cell systems.

  • These data support the notion that lead molecules should be tested in the therapeutic environment as quickly as possible to reduce attrition of possibly useful drug candidates.

  • These ideas also indicate some areas of possible therapeutic intervention emanating from such phenotypic conditions (that is, phantom genes where receptors assume a phenotype through combination of gene products in cells)

Abstract

Recombinant and natural cellular assays for human G-protein-coupled receptors are used to optimize initial lead molecules obtained from screening. Although the activity of these molecules can be assessed on human genotype receptors, there is increasing evidence that cells impose a phenotypic selectivity to molecules in various cellular backgrounds. This opens the possibility of dissimulations between activity seen in lead optimization assays and the intended therapeutic value in humans. This review discusses the mechanisms by which cells can impose phenotypic selectivity on molecules and approaches to reduce this practical problem for drug discovery.

This is a preview of subscription content, access via your institution

Access options

Buy this article

  • Purchase on Springer Link
  • Instant access to full article PDF
Buy now

Prices may be subject to local taxes which are calculated during checkout

Figure 1: Schematic diagram of the drug discovery process.
Figure 2: Schematic of a range of dose-response curves to two agonists of preset efficacy in assays of varying sensitivity.
Figure 3: Cycle of receptor synthesis, expression, membrane lifetime interacting with membrane and cytosolic proteins and internalization back into the cell.
Figure 4: Differences in relative potency of calcitonin agonists in different cells.
Figure 5: Receptors as information-processing units.

Similar content being viewed by others

References

  1. Marchese, A., George, S. R., Kolakowski, L. F., Lynch, K. R. & O'Dowd, B. F. Novel GPCRs and their endogenous ligands: expanding the boundaries of physiology and pharmacology. Trends Pharmacol. Sci. 20, 370–375 (1999).

    CAS  PubMed  Google Scholar 

  2. Venter, J. C. et al. The sequence of the human genome. Science 291, 1304–1351 (2001).

    Article  CAS  PubMed  Google Scholar 

  3. Drews, J. Drug discovery: a historical perspective. Science. 287, 1960–1964 (2000).

    CAS  PubMed  Google Scholar 

  4. Black, J. W. & Leff, P. Operational models of pharmacological agonist. Proc. R. Soc. Lond., B, Biol. Sci., 220, 141–162 (1983). A pivotal paper in receptor pharmacology describing a completely new way to express functional pharmacological response with no required assumptions about agonist mechanism. It has become the standard for modelling functonal receptor function in the literature.

    CAS  Google Scholar 

  5. Kenakin, T. P. Efficacy at G-protein coupled receptors. Ann. Rev. Pharmacol. Toxicol. 42, 349–379 (2002).

    CAS  Google Scholar 

  6. Kost, T. A. & Condreay, J. P. Recombinant baculoviruses as mammalian cell gene-delivery vectors. Trends Biotech. 20, 173–180 (2002).

    CAS  Google Scholar 

  7. Brady, A. E. & Limbird, L. E. G-protein-coupled receptor interacting proteins: emerging roles in localization and signal transduction. Cell. Signal. 14, 297–309 (2002). An excellent overview of the newly discovered interactants for G-protein-coupled receptors that modify and initiate drug action.

    CAS  PubMed  Google Scholar 

  8. Horne, W. C., Shyu, J. -F., Chakraborty, M. & Baron, R. Signal transduction by calcitonin: multiple ligands, receptors, and signaling pathways. Trends Endocrinol. Metab. 5, 395–401 (1994).

    CAS  PubMed  Google Scholar 

  9. Laugwitz, K. -L. et al. The human thyrotropin receptor: A heptahelical receptor capable of stimulating members of all four G protein families. Proc. Natl Acad. Sci. USA 93, 116–1120 (1996).

    CAS  PubMed  PubMed Central  Google Scholar 

  10. Kenakin, T. P. Differences between natural and recombinant G-protein coupled receptor systems with varying receptor/G-protein stoichiometry. Trends Pharmacol. Sci. 18, 456–464 (1997).

    CAS  PubMed  Google Scholar 

  11. Cordeaux, Y. et al. Influence of receptor number on functional responses elicited by agonists acting at the human adenosine A1 receptor: Evidence for signaling pathway-dependent changes in agonist potency and relative intrinsic activity. Mol. Pharmacol. 58, 1075–1084 (2000).

    CAS  PubMed  Google Scholar 

  12. Cussac, D., Newman-Trancredi, A., Duqueyroix, D., Pasteau, V. & Millan, M. J. Differential activation of Gq/11 and Gi3 proteins at 5-hydroxytryptamine2C receptors revealed by antibody capture assays: Influence of receptor reserve and relationship to agonist-directed trafficking. Mol. Pharmacol. 62, 578–589 (2002).

    CAS  PubMed  Google Scholar 

  13. Nasman, J., Kukkonen, J. P., Ammoun, S. & Akerman, K. E. O. Role of G-protein availability in differential signaling by α2-adrenoceptors. Biochem. Pharmacol. 62, 913–922 (2002).

    Google Scholar 

  14. Costa, T., Ogino, Y, Munson, P. J., Onaran, H. O. & Rodbard, D Drug efficacy at guanine nucleotide-binding regulatory protein-linked receptors: Thermodynamic interpretation of negative antagonism and of receptor activity in the absence of ligand. Mol. Pharmacol. 41, 549–560 (1992).

    CAS  PubMed  Google Scholar 

  15. 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 

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

    CAS  PubMed  Google Scholar 

  17. Kenakin, T. P. Inverse, protean, and ligand-selective agonism: Matters of receptor conformation. FASEB J. 15, 598–611 (2001).

    CAS  PubMed  Google Scholar 

  18. Kenakin, T. P. Efficacy at G-protein-coupled receptors. Nature Rev. Drug Discov. 1, 103–109 (2002).

    CAS  Google Scholar 

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

    CAS  PubMed  Google Scholar 

  20. Meller, E., Puza, T., Diamond, J., Lieu, H. -D. & Bohmaker, K. Comparative effects of receptor inactivation, 17β-estradiol and pertussis toxin on dopaminergic inhibition of prolactin-secretion in vitro. J. Pharmacol. Exp. Ther. 263, 462–469 (1992).

    CAS  PubMed  Google Scholar 

  21. Robb, S. et al. Agonist-specific coupling of a cloned Drosophila octopamine/tyramine receptor to multiple second messenger systems. EMBO J. 13, 1325–1332 (1994).

    CAS  PubMed  PubMed Central  Google Scholar 

  22. Sagan, S., Karoyan, P., Chassaing, G. & Lavielle, S. Further delineation of the two binding sites (R*n) associated with tachykinin neurokinin-1 receptors using [3-prolinomethionine]SP analogues. J. Biol. Chem. 274, 23770–23776 (1999).

    CAS  PubMed  Google Scholar 

  23. Wenzel-Seifert, K. & Seifert, R. Molecular analysis of β2-adrenoceptor coupling to Gs-, Gi-, and Gq- proteins. Mol. Pharmacol. 58, 954–966 (2000).

    CAS  PubMed  Google Scholar 

  24. Krumins, A. M. & Barber, R. The stability of the agonist β2-adrenergic receptor–Gs complex: evidence for agonist-specific states. Mol. Pharmacol. 52, 144–154 (1997).

    CAS  PubMed  Google Scholar 

  25. Seifert, R., Gether, U., Wenzel-Siefert, K. & Kobilka, B. Effects of guanine, inosine, and xanthine nucleotides on β2-adrenergic receptor/Gs interactions: evidence for multiple receptor conformations. Mol. Pharmacol. 56, 348–358 (1999).

    CAS  PubMed  Google Scholar 

  26. Chidiac, P., Hebert, T. E., Valiquette, M., Dennis, M. & Bouvier, M. Inverse agonist activity of β-adrenergic antagonists. Mol. Pharmacol. 45, 490–9 (1994).

    CAS  PubMed  Google Scholar 

  27. Chidiac, P., Nouet, S. & Bouvier, M. Agonist-induced modulation of inverse agonist efficacy at the β2-adrenergic receptor. Mol. Pharmacol. 50, 662–666 (1996).

    CAS  PubMed  Google Scholar 

  28. Gether, U. et al. Structural instability of a constitutively active G-protein coupled receptor. J. Biol. Chem. 272, 2587–2590 (1997). Describes a unique approach to the study of ligand interaction with receptors. Specifically, actual changes in protein conformation, in response to drug binding, are observed. This is a powerful new technique in receptor pharmacology.

    CAS  PubMed  Google Scholar 

  29. Akam, E. C., Challiss, R. A. J. & Nahorski, S. R. Gq/11 and Gi/1o activation profiles in CHO cells expressing human muscarinic acetylcholine receptors: Dependence on agonist as well as receptor-subtype. Br. J. Pharmacol. 132, 950–958 (2001).

    CAS  PubMed  PubMed Central  Google Scholar 

  30. Watson, C. A. et al. The use of stimulus-biased assay systems to detect agonist-specific receptor active-states: implications for the trafficking of receptor stimulus by agonists. Mol. Pharmacol. 58, 1230–1238 (2000).

    CAS  PubMed  Google Scholar 

  31. Kukkonen, J. P., Jansson, C. C. & Akerman, K. E. O. Agonist trafficking of Gi/o-mediated α2A-adrenoceptor responses in HEL 92. 1. 7 cells. Br. J. Pharmacol. 132, 1477–1484 (2001).

    CAS  PubMed  PubMed Central  Google Scholar 

  32. Jansson, C. C. et al. Protean agonism at α2A-adrenoceptors. Mol. Pharmacol. 53, 963–968 (1998).

    CAS  PubMed  Google Scholar 

  33. MacKinnon, A. C., Waters, C., Jodrell, D., Haslett, C. & Sethi, T. Bombesin and substance P analogues differentially regulate G-protein coupling to the bombesin receptor. J. Biol. Chem. 276, 28083–28091 (2001).

    CAS  PubMed  Google Scholar 

  34. Takasu, H., Gardella, T. J., Luck, M. D., Potts, J. T. & Bringhurst, F. R. Amino-terminal modifications of human parathyroid hormone (PTH) selectively alter phospholipase C signaling via type 1 PTH receptor: Implications for design of signal-specific PTH ligands. Biochem. 38, 13453–13460 (1999).

    CAS  Google Scholar 

  35. Lopez-Gimenez, J. F. et al. Multiple conformations of native and recombinant human 5-hydroxytryptamine2A receptors are labeled by agonists and discriminated by antagonists. Mol. Pharmacol. 60, 690–699 (2001).

    CAS  PubMed  Google Scholar 

  36. Berg, K. A. et al. Effect pathway-dependent relative efficacy at serotonin type 2A and 2C receptors: evidence for agonist-directed trafficking of receptor stimulus. Mol. Pharmacol. 54, 94–104 (1998). The first description of unambiguous trafficking of stimulus by agonists through receptors. Specifically, the maximal response to agonists are shown to differ with different agonists thereby clearly indicating differences in receptor-specific efficacy associated with molecular structure.

    CAS  PubMed  Google Scholar 

  37. Bonhaus, D. W., Chang, L. K., Kwan, J. & Martin, G. R. Dual activation and inhibition of adenylyl cyclase by cannabinoid receptor agonists: evidence for agonist-specific trafficking of intracellular process. J. Pharmacol. Exp. Ther. 287, 884–888 (1998).

    CAS  PubMed  Google Scholar 

  38. Glass, M. & Northup, J. K. Agonist selective regulation of G proteins by cannabinoid CB1 and CB2 receptors. Mol. Pharmacol. 56, 1362–1369 (1999).

    CAS  PubMed  Google Scholar 

  39. Fathy, D. B., Leeb, T., Mathis, S. A. & Leeb-Lundberg, L. M. F. Spontaneous human B2 bradykinin receptor activity determines the action of partial agonists as agonists or inverse agonists. J. Biol. Chem. 274, 29603–6 (1999).

    CAS  PubMed  Google Scholar 

  40. Zhou, Y. -Y. et al. Spontaneous β2-adrenergic signaling fails to modulate l-type Ca2+ current in mouse ventricular myocytes. Mol. Pharmacol. 56, 485–493 (1999).

    CAS  PubMed  Google Scholar 

  41. Wiens, B. L., Nelspon, C. S. & Neve, K. A. Contribution of serine residues to constitutive and agonist-induced signaling via the D2s dopamine receptor: evidence for multiple, agonist-specific active conformations. Mol. Pharmacol. 54, 435–441 (1998).

    CAS  PubMed  Google Scholar 

  42. Liu, J. -G., Ruckle, M. B. & Prather, P. L. Constitutively active μ-opioid receptors inhibit adenylyl cyclase activity in intact cells and activate G-proteins differently than the agonist [D-Ala2,N-MePhe4, Gly-ol5]enkephalin. J. Biol. Chem. 276, 37779–37786 (2001).

    CAS  PubMed  Google Scholar 

  43. Christmanson, L., Westermark, P., & Bertsholtz, C. Islet amyloid polypeptide stimulates cyclic AMP accumulation via the porcine calcitonin receptor. Biochem. Biophys. Res. Commun. 205, 1226–1235 (1994).

    CAS  PubMed  Google Scholar 

  44. Stephenson, R. P. A modification of receptor theory. Br. J. Pharmacol. 11, 379–391 (1956). A classic paper describing efficacy as a separate property of some ligands. This paper forms the basis of modern receptor theory.

    CAS  Google Scholar 

  45. Costa, T. & Herz, A. Antagonists with negative intrinsic activity at δ-opioid receptors coupled to GTP-binding proteins. Proc. Natl Acad. Sci. USA 86, 7321–7325 (1989).

    CAS  PubMed  PubMed Central  Google Scholar 

  46. Pommier, B. et al. The cholecystokinB receptor is coupled to two effector pathways through pertussis toxin-sensitive and -insensitive G proteins. J. Neurochem. 73, 281–288 (1999).

    CAS  PubMed  Google Scholar 

  47. Dunlop, J., Zhang, Y., Smith, D. L. & Schechter, L. E. Characterization of 5-HT1A receptor functional coupling in cells expressing the human 5-HT1A receptor as assessed with the cytosensor microphysiometer J. Pharmacol. Toxicol. Meth. 40, 47–55 (1999).

    Google Scholar 

  48. Konkar, A. A., Zhu, Z. & Granneman, J. G. Aryloxypropanolamine and catecholamine ligand interactions with the α1-adrenergic receptor: evidence for interaction with distinct conformations of 1-adrenergic receptor. J. Pharmacol. Expt. Ther. 294, 923–932 (2000).

    CAS  Google Scholar 

  49. Thomas, W. G., Quian, H., Chang, C. -S. & Karnik, S. Agonist-induced phosphorylation of the angiotensin II (AT1A) receptor requires generation of a conformation that is distinct from the inositol phosphate-signaling state. J. Biol. Chem. 275, 2893–2900 (2000).

    CAS  PubMed  Google Scholar 

  50. Chakrabarti, S., Law, P. Y. & Loh, H. H. Distinct differences between morphine- and [δ-Ala2,N-MePhe4,Gly-ol5]enkephalin-μ-opioid complexes demonstrated by cyclic independent protein kinase phosphorylation. J. Neurochem. 71, 231–233 (1998).

    CAS  PubMed  Google Scholar 

  51. Blake, A. D., Bot, G., Freeman, J. C. & Reisine, T. Differential opioid agonist regulation of the mouse μ-opioid receptor. J. Biol. Chem. 272, 782–790 (1997).

    CAS  PubMed  Google Scholar 

  52. van Hooft, J. A., Vijverberg, H. P. M. Selection of distinct conformational states of the 5–HT3 receptor by full and partial agonists. Br. J. Pharmacol. 117, 839–846 (1996).

    CAS  PubMed  PubMed Central  Google Scholar 

  53. Roettger, B. F. et al. Antagonist-stimulated internalization of the G protein-coupled cholecystokinin receptor. Mol. Pharmacol. 51, 357–362 (1997). This paper is the first to show clear dissociation between receptor activation (G-protein mediated response) and receptor internalization. This is an important indicator of separate efficacies of ligands for different receptor behaviors.

    CAS  PubMed  Google Scholar 

  54. Keith, D. E. et al. Morphine activates opioid receptors without causing their rapid internalization. J. Biol. Chem. 271, 19021–19024 (1996).

    CAS  PubMed  Google Scholar 

  55. Hunyady, L., Baukal, A. J., Balla, T. & Catt, K. J. Independence of type I angiotensin II receptor endocytosis from G protein coupling and signal transduction. J. Biol. Chem. 269, 24798–24804 (1994).

    CAS  PubMed  Google Scholar 

  56. Vila-Coro, A. J., Mellado, M., Matrin de Ana, A., Martinez-A., C. & Rodriguez-Frade, J. M. Characterization of RANTES- and Aminooxypentane-RANTES-triggered desensitization signals reveals differences in recruitment of the G-protein-coupled receptor complex. J. Immunol. 163, 3037–3044 (1999).

    CAS  PubMed  Google Scholar 

  57. Dickenson, J. M. & Hill, S. J. Synergistic interactions between human transfected adenosine A1 receptors and endogenous cholecystokin receptors in CHO cells. Eur. J. Pharmacol. 302, 141–151 (1996).

    CAS  PubMed  Google Scholar 

  58. Gerwins, P. & Fredholm, B. B. ATP and its metabolite adenosine act synergistically to mobilise intracellular calcium via the formation of inositol 1,4,5-triphosphate in a smooth muscle line. J. Biol. Chem. 267, 16081–16090 (1992).

    CAS  PubMed  Google Scholar 

  59. Gerwins, P. & Fredholm, B. B. Stimulation of adenosine A1 receptors and bradykinin receptors which act via different G-proteins synergistically raises inositol 1,4,5-triphosphate and intracellular calcium in DDT1MF-2 smooth muscle cells. Proc. Natl Acad. Sci. USA 89, 7330–7339 (1992).

    CAS  PubMed  PubMed Central  Google Scholar 

  60. Dickenson, J. M. Synergistic actions between adenosine A1 and α1B-adrenoceptors in DDT1MF–2 cells. Biochem. Soc. Trans. 22, 427S (1994).

    CAS  PubMed  Google Scholar 

  61. AbdAlla, S., Lother, H. & Quitterrer, U. AT1-receptor heterodimers show enhanced G-protein activation and altered receptor sequestration. Nature 407, 94–99 (2000).

    CAS  PubMed  Google Scholar 

  62. Devi, L. A. Heterodimerization of G-protein-coupled receptors: pharmacology, signaling and trafficking. Trends Pharmacol. Sci. 22, 532–537 (2001).

    CAS  PubMed  Google Scholar 

  63. Jordan, B. A., Cvejic, S. & Devi, L. A. Opioids and their complicated receptor complexes. Neuropsychopharmacology 23, S5–S18 (2000).

    CAS  PubMed  Google Scholar 

  64. Zhu, Y. et al. Retention of supraspinal delta-like analgesia and loss of morphine tolerance in delta opioid receptor knockout mice. Neuron 24, 243–252 (1999).

    CAS  PubMed  Google Scholar 

  65. Rocheville, M. et al. Receptors for dopamine and somatostatin: formation of hetero-oligomers with enhanced functional activity. Science 288, 154–157 (2000).

    CAS  PubMed  Google Scholar 

  66. Cladman, W. & Chidiac, P. Characterization and comparison of RGS2 and RGS4 as GTP-ase-activating proteins for m2 muscarinic receptor-stimulated Gi . Mol. Pharmacol. 62, 654–659 (2002).

    CAS  PubMed  Google Scholar 

  67. Zaworski, P. G. et al. Efficient functional coupling of the human D3 dopamine receptor to Go subtype of G proteins in SH-SY5Y cells. Br. J. Pharmacol. 128, 1181–1188 (1999).

    CAS  PubMed  PubMed Central  Google Scholar 

  68. Albert, P. R. & Robillard, L. G-protein specificity: Traffic direction required. Cell. Signal. 14, 407–418 (2002).

    CAS  PubMed  Google Scholar 

  69. Dickenson, J. M. & Hill, S. J. Involvement of G-protein βγ subunits in coupling the adenosine A1 receptor to phospholipase C in transfected CHO cells. Eur. J. Pharmacol. 355, 85–93 (1998).

    CAS  PubMed  Google Scholar 

  70. Selbie, L. A. & Hill, S. J. G protein-coupled-receptor cross-talk: the fine tuning of multiple receptor-signalling pathways. Trends Pharmacol. Sci. 19, 87–93 (1998).

    CAS  PubMed  Google Scholar 

  71. Marinissen, M. J. & Gutkind, J. S. G-protein-coupled receptors and signaling networks: emerging paradigms. Trends Pharmacol. Sci. 22, 368–376 (2001).

    CAS  PubMed  Google Scholar 

  72. Ostrom, R. S. New determinants of receptor–effector coupling: trafficking and compartmentation in membrane microdomains. Mol. Pharmacol. 61, 473–476 (2002).

    CAS  PubMed  Google Scholar 

  73. Ostrom, R. S., Post, S. R. & Insel, P. A. Stoichiometry and compartmentation in G protein-coupled receptor signaling: implications for therapeutic interventions involving Gs . J. Pharmacol. Exp. Ther. 294, 407–412 (2000).

    CAS  PubMed  Google Scholar 

  74. Rybin, V. O., Xu, X., Lisanti, M. P. & Steinberg, S. F. Differential targeting of β-adrenergic receptor subtypes and adenylyl cyclase to cardiomyocyte caveolae: A mechanism to functionally regulate the cAMP signaling pathway. J. Biol. Chem. 275, 41447–41453 (2000).

    CAS  PubMed  Google Scholar 

  75. Davare, M. A. et al. A β2-adrenergic receptor signaling complex assembled with the Ca2+ channel Cav1. 2. Science 293, 98–101 (2001).

    CAS  PubMed  Google Scholar 

  76. Fraser, I. D. C. et al. Assembly of an A kinase-anchoring protein β2-adrenergic receptor complex facilitates receptor phosphorylation and signaling. Curr. Biol. 10, 409–412 (2000).

    CAS  PubMed  Google Scholar 

  77. Armour, S., Foord, S., Kenakin, T. P. & Chen, W. -J. Pharmacological characterization of receptor activity modifying proteins (RAMPs) and the human calcitonin receptor. J. Pharmacol. Toxicol. Methods 42, 217–224 (1999).

    CAS  PubMed  Google Scholar 

  78. Fraser, N. J. et al. The amino terminus of receptor activity modifying proteins is a critical determinant of glycosylation state and ligand binding of calcitonin-like receptor. Mol. Pharmacol. 55, 1054–1059 (1999).

    CAS  PubMed  Google Scholar 

  79. Foord, S. M. & Marshall, F. H. RAMPS: Accessory proteins for seven transmembrane domain receptors. Trends Pharmacol. Sci. 20, 184–187 (1999).

    CAS  PubMed  Google Scholar 

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

    CAS  PubMed  Google Scholar 

  81. Christopoulos, G. et al. Multiple amylin receptors arise from receptor activity modifying protein interaction with the calcitonin receptor gene product. Mol. Pharmacol. 56, 235–242 (1999).

    CAS  PubMed  Google Scholar 

  82. Christopoulos, A. et al. Novel receptor partners and function of receptor activity-modifying proteins. J. Biol. Chem. 278, 3293–3297 (2003).

    CAS  PubMed  Google Scholar 

  83. Varrault, A., Journot, L., Audiger, Y. & Bockaert, J. Transfection of human 5-hydroxytryptamine1A receptors in NIH-3T3 fibroblasts: effects of increasing receptor density on the coupling of 5-hydroxytryptamine1A receptors to adenylyl cyclase. Mol. Pharmacol. 41, 999–1007 (1992).

    CAS  PubMed  Google Scholar 

  84. Cortes, S. F., Lemos, V. S., Corriu, C. & Stoclet, J. C. Changes in angiotensin II receptor density and calcium handling during proliferation in SHR aortic myocytes. Am. J. Physiol. 271, H2330–2338 (1996).

    CAS  PubMed  Google Scholar 

  85. Hoel, N. L., Hansen-Schwartz, J. & Edvinsson, L. Selective up-regulation of 5-HT(1B/1D) receptors during organ culture of cerebral arteries. Neuroreport 12, 1605–1608 (2001).

    CAS  PubMed  Google Scholar 

  86. Lelievre, V., Caigneaux, E., Muller, J. M. & Falcon, J. Extracellular adenosine deprivation induces epithelial differentiation of HT29 cells: Evidence for a concomitant adenosine A(1)/A(2) receptor balance regulation. Eur. J. Pharmacol. 10, 21–29 (2000).

    Google Scholar 

  87. Makino, I. et al. Phenotypic changes of adrenomedullin receptor components, RAMP2, and CRLR mRNA expression in cultured rat vascular smooth muscle cell. Biochem. Biophys. Res. Commun. 288, 515–520 (2001).

    CAS  PubMed  Google Scholar 

  88. Bowers, C. W. & Dahm, L. M. Extracellular matrix regulates smooth muscle responses to substance P Proc. Natl Acad. Sci. USA 89, 8130–8134 (1992).

    CAS  PubMed  PubMed Central  Google Scholar 

  89. Kawase, T., Orikasa, M. & Suzuki, A. Starvation of clonal osteoblast-like cell line MOB 3-4-F2, down-regulates prostaglandin E2 receptors but increases cAMP response to prostaglandin E2. Cell Signal 3, 153–158 (1991).

    CAS  PubMed  Google Scholar 

  90. Corriu, C., Andre, P., Schott, C., Michel, M. & Stoclet, J. C. ANG II receptor expression and function during phenotypic modulation of rat aortic smooth muscle cells. Am. J. Physiol. 266, H631–636 (1994).

    CAS  PubMed  Google Scholar 

  91. Chakraborthy, M., Chatterjee, D., Kellokumpu, S., Rasmussen, H. & Baron, R. N. Cell cycle-dependent coupling of the calcitonin receptor to different G-proteins. Science, 251, 1078–1082 (1991).

    Google Scholar 

  92. Chen, W. J. et al. Expression cloning and receptor pharmacology of human calcitonin receptors from MCF-7 cells and their relationship to amylin receptors. Mol. Pharmacol. 52, 1164–1175 (1997).

    CAS  PubMed  Google Scholar 

  93. Muff, R., Buhlmann, N., Fischer, J. A. & Born, W. An amylin receptor is revealed following co-transfection of a calcitonin receptor with receptor activity modifying proteins-1 or -3. Endocrinology 140, 2924–2927 (1999).

    CAS  PubMed  Google Scholar 

  94. Tilakaratne, N., Christopoulos, G., Zumpe, E. T., Foord, S. M. & Sexton, P. M. Amylin receptor phenotypes derived from human calcitonin receptor/RAMP coexpression exhibit pharmacological differences dependent on receptor isoform and host cell environment. J. Pharmacol. Exp. Ther. 294, 61–72 (2000)

    CAS  PubMed  Google Scholar 

  95. Molenaar, P., Sarseso, D. & Kaumann, A. J. Proposal for the interaction of non-conventional partial agonists and catecholamines with the 'putative β4-adrenoceptor' in mammalian heart. Clin. Exp. Pharmacol. Physiol. 24, 647–656 (1997).

    CAS  PubMed  Google Scholar 

  96. Granneman, J. G. The putative β4-adrenergic receptor is a novel state of the β1-adrenergic receptor. Am. J. Physiol. Endocrinol. Metab. 280, E199–E202 (2001).

    CAS  PubMed  Google Scholar 

  97. Konkar, A. A., Zhai, Y. & Granneman, J. β1-adrenergic receptors mediate β3-adrenergic-independent effects of CGP 12177 in brown adipose tissue. Mol. Pharmacol. 57, 252–258 (2000).

    CAS  PubMed  Google Scholar 

  98. Traynor, J. Subtypes of μ-opioid receptor: fact or fiction. Trends Pharmacol. Sci. 10, 52–53 (1989).

    CAS  PubMed  Google Scholar 

  99. Traynor, J. & Elliot, J. δ-opioid receptor subtypes and cross talk with μ-receptors. Trends Pharmacol. Sci. 14, 84–85 (1993).

    CAS  PubMed  Google Scholar 

  100. Jordan, B. A. & Devi, L. A. G-protein–coupled receptor heterodimerization modulates receptor function. Nature 399, 697–700 (1999).

    CAS  PubMed  PubMed Central  Google Scholar 

Download references

Author information

Authors and Affiliations

  1. Systems Research, GlaxoSmithKline Research and Development, 5 Moore Drive, Research Triangle Park, North Carolina, 27709, USA

    Terry Kenakin

Authors
  1. Terry Kenakin
    View author publications

    You can also search for this author in PubMed Google Scholar

Related links

Related links

DATABASES

LocusLink

Adenosine A1

angiotensin II receptors

bradykinin

calcitonin receptor

dopamine D2 receptor

follicle-stimulating hormone receptor

PACAP

RAMP3

somatostatin receptors

thyrotropin receptor

tyramine

Glossary

RECOMBINANT SYSTEMS

Cells transfected with DNA containing new genetic material in an order different from the original. Genetic engineering can be used to do this deliberately to produce new proteins in cells.

EFFICACY

The property of a molecule that causes the receptor to change its behavior toward the host cell.

AFFINITY

Ligands reside at a point of minimal energy within a binding locus of a protein according to a ratio of the rate that the ligand leaves the surface of the protein (koff) and the rate it approaches the protein surface (kon). This ratio is the equilibrium dissociation constant of the ligand–protein complex (denoted Keq = koff/kon) and defines the molar concentration of the ligand in the compartment containing the protein at which 50% of the protein has ligand bound to it at any one instant. The 'affinity' or attraction of the ligand for the protein is the reciprocal of Keq.

PARTIAL AGONIST

Whereas a full agonist produces the system maximal response, a partial agonist produces a maximal response that is below that of the system maximum (and that of a full agonist). As well as producing a sub-maximal response, partial agonists produce antagonism of more efficacious full agonists.

FULL AGONIST

This is the name given to an agonist that produces the full system maximal response (Emax). It is a system-dependent phenomenon and should not necessarily be associated with a particular agonist, as an agonist can be a full agonist in some systems and a partial agonist in others.

CONSTITUTIVE RECEPTOR ACTIVITY

Receptors spontaneously produce conformations that activate G-proteins in the absence of agonists. This activity, referred to as constitutive activity, can be observed in systems in which the receptor expression levels are high and the resulting levels of spontaneously activating receptor species produce visible physiological response. An inverse agonist reverses this constitutive activity and so reduces, in a dose-dependent manner, the spontaneously elevated basal response of a constitutively active receptor system.

INVERSE AGONISTS

These ligands reverse constitutive receptor activity. At present it is thought that this occurs because inverse agonists have a selectively higher affinity for the inactive versus the active conformation of the receptor. It is important to note that although inverse agonist activity requires constitutive activity to be observed, the property of the molecule that is responsible for this activity does not disappear when there is no constitutive activity. In these cases, inverse agonists function as simple competitive antagonists.

HETERODIMER

In this case, a physical biochemical complex of two receptors formed in the membrane and interacting with ligands as one species. The pharmacological properties of heterodimers can differ from the properties of either reactant.

Rights and permissions

Reprints and permissions

About this article

Cite this article

Kenakin, T. Predicting therapeutic value in the lead optimization phase of drug discovery. Nat Rev Drug Discov 2, 429–438 (2003). https://doi.org/10.1038/nrd1110

Download citation

  • Issue Date:

  • DOI: https://doi.org/10.1038/nrd1110

This article is cited by

Search

Advanced 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