Receptors as Drug Targets

Michael Williams1, Rita Raddatz1

1 Worldwide Discovery Research Cephalon, Inc., West Chester, Pennsylvania
Publication Name:  Current Protocols in Pharmacology
Unit Number:  Unit 1.1
DOI:  10.1002/0471141755.ph0101s32
Online Posting Date:  April, 2006
GO TO THE FULL TEXT: PDF or HTML at Wiley Online Library

Abstract

Receptors, located on both the cell surface and within the cell, are the molecular targets through which drugs produce their beneficial effects in various disease states. Receptors were initially conceptualized at the beginning of the 20th century by the parallel efforts of Ehrlich and Langley. The concepts of the receptor and receptor theory, based on the Law of Mass Action, have undergone continuous refinement as they have been characterized in terms of their molecular structure, association with ancillary proteins (e.g., G proteins, arrestins, RAMPs), and functional characteristics in normal and diseased tissues. The concepts describing ligand interactions with receptors have also been refined from the simple binary concept of competitive agonists and antagonists to partial agonists, allosteric modulators and inverse agonists. Concepts such as receptor constitutive activity, internalization and dimerization add additional complexity to the role of receptors in tissue function and in precisely characterizing their role in homeostasis and disease.

Keywords: agonist; antagonist allosteric modulator; G protein‐coupled receptor; heterotrimeric G protein; ion channels; ligand; new chemical entity (NCE); orphan receptor; structure activity relationship (SAR)

     
 
GO TO THE FULL PROTOCOL:
PDF or HTML at Wiley Online Library

Table of Contents

  • Receptor Classification and Nomenclature
  • Receptor Structure and Motifs
  • Receptor Ligands
  • Constitutively Active Receptors
  • Ligand‐Receptor Interactions
  • Orphan Receptors
  • Neurotransmitters, Neurohormones, and Neuromodulators
  • Allosteric Ligands
  • Human Recombinant Receptors
  • Receptor Mutations and Chimeras
  • Assessing Receptor Function
  • Literature Cited
  • Figures
     
 
GO TO THE FULL PROTOCOL:
PDF or HTML at Wiley Online Library

Materials

GO TO THE FULL PROTOCOL:
PDF or HTML at Wiley Online Library

Figures

  •   FigureFigure 1.1.1 Structural motifs of various receptor classes. (A) GPCR with seven membrane‐spanning regions; (B‐E) LGICs: (B) glutamate receptor, (C) P2X receptor, (D) nAChR, and (E) VGIC K+‐rectified inward (Kirs) receptor; (F) STAT receptor; (G) PTK growth factor receptor; (H) neutrophin receptor ( trk).
  •   FigureFigure 1.1.2 Ligand efficacy spectrum.
  •   FigureFigure 1.1.3 (A) Schematic of a saturation binding curve: total, nonspecific, and specific binding (see UNIT). (B) Scatchard derivation of specific binding saturation isotherm. (C) Ligand displacement curve showing IC50 relationship. (D) Ligand efficacy and EC50 derivation. The EC50 for a partial agonist (EC50 B) can be determined as the concentration at which a similar response to that of a full agonist (EC50 A) is observed. Alternatively, the EC50 for a partial agonist can be determined as the concentration at which 50% of the maximal response to the partial agonist is determined (EC50 C). Clearly, using the latter approach in the absence of any measure of ligand potency (receptor affinity) can provide misleading data. (E) Dose‐response relationship in the presence of increasing concentrations ( X‐Z ) of an antagonist. The antagonist produces a classical dose‐dependent rightward of the agonist response. (F) Schild derivation of the data in E to derive a pA2 value (see UNIT).
  •   FigureFigure 1.1.4 Pharmacological versus functional antagonism. (A) GABAA receptor activation produces a signal (GABA release) which causes neuron B to produce a response. (B) Pharmacological antagonism: blockade of the GABAA response at neuron B by a GABAA antagonist is a direct competitive effect. (C) Functional antagonism: The same GABAA response on neuron B can be blocked in vivo by a nicotinic or dopaminergic antagonist via interactions with upstream events in a pathway. In the absence of any further data on the putative nicotinic or dopaminergic antagonist, they could be classified as GABAA antagonists.

Videos

Literature Cited

   Adan, R.A. and Kas, M.J. 2003. Inverse agonism gains weight. Trends Pharmacol. Sci. 24:315‐321.
   Akbar, G.K.M., Dasarai, V.R., Webb, T.E., Ayyanathan, K., Pillarisetti, K., Sandhu, A.K., Athwal, R.S., Daniel, J.L., Ashby, B., Barnard, E.A., and Kunapuli, S.P. 1996. Molecular cloning of a novel P2 receptor from human erythroleukemia cells. J. Biol. Chem. 271:18363‐18367.
   Ardati, A., Hennigsen, R.A., Higelin, J., Reinscheid, R.K., Civelli, O., and Monsma, F.J. Jr. 1997. Interaction of [3H]orphanin FQ and 125I‐tyr14‐orphanin FQ with the orphanin FQ receptor: Kinetics and modulation by cations and guanine nucleotides. Mol. Pharmacol. 51:816‐824.
   Ariens, E.J. 1954. Affinity and intrinsic activity in the theory of competitive inhibition. Arch. Int. Pharmacodyn. Ther. 99:32‐49.
   Arvanitakis, L., Geras‐Raaka, E., Varma, A., Gershengorn, M.C., and Cesarman, E. 1997. Human herpes virus KSHV encodes a constitutively active G‐protein‐coupled receptor linked to cell proliferation. Nature 385:347‐350.
   Black, J.W. 1989. Drugs from emasculated hormones: The principle of syntopic antagonism. Science 245:486‐492.
   Bloom, F.E. 1988. Neurotransmitters: Past, present and future directions. FASEB J. 2:32‐41.
   Catterall, W.A. 2000. From ionic currents to molecular mechanisms: The structure and function of voltage‐gated sodium channels. Neuron 26:13‐25.
   Clifford, E.E., Martin, K.A., Dalal, P., Thomas, R., and Dubyak, G.R. 1997. Stage‐specific expression of P2Y receptors, ecto‐apyrase and ecto‐S′‐nucleotidase in myeloid leukocytes. Am. J. Physiol. 273:C973‐C987.
   Coughlin, S.R. 1994. Expanding horizons for receptors coupled to G proteins: Diversity and disease. Curr. Opin. Cell Biol. 6:191‐197.
   Devane, W.A., Hanus, L., Breur, A., Pertwee, R.G., Stevenson, L.A., Griffin, G., Gibson, D., Mandelbaum, A., Etinger, A., and Mechoulam, R. 1992. Isolation and structure of a brain constituent that binds to the cannabinoid receptor. Science 258:1882‐1884.
   Donaldson, L.F., Hanley, M.R., and Villablanca, A.C. 1997. Inducible receptors. Trends Pharmacol. Sci. 18:171‐181.
   Elsele, J.‐L., Betrand, S., Galzi, J.‐L., Devilliers‐Thiery, A., Changeux, J.‐P., and Bertrand, D. 1993. Chimaeric nicotinic: Serotonergic receptor combines distinct ligand binding and channel specificities. Nature 366:479‐483.
   Garcia‐Colunga, J., Awada, J.N., and Miledi, R. 1997. Blockage of muscle and neuronal nicotinic acetylcholine receptors by fluoxetine (Prozac). Proc. Natl. Acad. Sci. U.S.A. 94:2041‐2044.
   Gelman, D.M., Noain, D., Avale, M.E., Otero, V., Low, M.J., and Rubinstein, M. 2003. Transgenic mice engineered to target Cre/loxP‐mediated DNA recombination into catecholaminergic neurons. Genesis 36:196‐202.
   Grissmer, S. 1997. Potassium channels still hot. Trends Pharmacol. Sci. 18:347‐350.
   Hall, R.A., Premont, R.T., and Lefkowitz, R.J. 1999. Heptahelical receptor signaling: Beyond the G protein paradigm. J. Cell Biol. 145:927‐932.
   Hopkins, A.L. and Groom, C.R. 2002. The druggable genome. Nat. Rev. Drug Discov. 1:727‐730.
   Ihle, J.N. 1996. STATs: Signal transducers and activators of transcription. Cell 84:331‐334.
   Kenakin, T. 1993. Pharmacologic Analysis of Drug‐Receptor Interaction, 2nd ed. Raven Press, New York.
   Kenakin, T. 1996. The classification of seven transmembrane receptors in recombinant expression systems. Pharmacol. Rev. 48:413‐465.
   Kenakin, T. and Onaran, O. 2002. The ligand paradox between affinity and efficacy: Can you be there and not make a difference? Trends Pharmacol. Sci. 23:275‐280.
   Kenakin, T. 2003. Predicting therapeutic value in the lead optimization phase of drug discovery. Nat. Rev. Drug Discov. 2:429‐438.
   Kobilka, B.K., Kobilka, T.J., Daniel, K.W., Regan, J.W., Caron, M.G., and Lefkowitz, R.J. 1988. Chimeric α2‐, β2‐adrenergic receptors: Delineation of domains involved in effector coupling and ligand specificity. Science 240:1310‐1316.
   Kollias‐Baker, C.A., Ruble, J., Jacobson, M., Harrison, J.K., Ozeck, M., Shyrock, J.C., and Belardinelli, L. 1997. Agonist‐independent effect of an allosteric enhancer of the A1 adenosine receptor in CHO cells stably expressing the recombinant human A1 receptor. J. Pharmacol. Exp. Ther. 281:761‐768.
   Koshland, D.E. Jr., Nemethy, S., and Filmer, D. 1966. Comparison of experimental binding data and theoretical models in proteins containing subunits. Biochemistry 5:365‐381.
   Kostenis, E., Milligan, G., Christopoulos, A., Sanchez‐Ferrer, C.F., Heringer‐Walther, S., Sexton, P.M., Gembardt, F., Kellett, E., Martini, L., Vanderheyden, P., Schultheiss, H.P., and Walther, T. 2005. G‐protein‐coupled receptor Mas is a physiological antagonist of the angiotensin II type 1 receptor. Circulation 111:1806‐1813.
   Laduron, P.M. 1992. Towards genomic pharmacology: From membranal to nuclear receptors. Adv. Drug Res. 22:107‐148.
   Leaman, D.W., Leung, S., Li, X., and Stark, G.R. 1996. Regulation of STAT‐dependent pathways by growth factors and cytokines. FASEB J. 10:1578‐1588.
   Liebmann, C. 2004. G protein‐coupled receptors and their signaling pathways: Classical therapeutical targets susceptible to novel therapeutic concepts. Curr. Pharm. Des. 10:1937‐1958.
   Matherne, G.P., Linden, J., Byford, A.M., Gauthier, N.S., and Headrick, J.P. 1997. Transgenic A1 adenosine receptor overexpression increases myocardial resistance to ischemia. Proc. Natl. Acad. Sci. U.S.A. 94:6541‐6546.
   May, L.T., Avlani, V.A., Sexton, P.M., and Christopoulos, A. 2004. Allosteric modulation of G protein‐coupled receptors. Curr. Pharm. Des. 10:2003‐2013.
   Monod, J., Wyman, J., and Changeux, J.‐P. 1965. On the nature of allosteric transitions. J. Mol. Biol. 12:88‐118.
   Navia, M.A. and Chaturvedi, C. 1996. Design principles for orally bioavailable drugs. Drug Disc. Today 1:179‐189.
   Neumann, S., Doubell, T.P., Leslie, T., and Woolf, C.J. 1996. Inflammatory pain hypersensitivity mediated by phenotypic switch in myelinated primary sensory neurons. Nature 384:360‐364.
   Oksenberg, D., Marsters, S.A., O'Dowd, B.F., Jin, H., Havlik, S., Peroutka, S.J., and Ashkenazi, A. 1992. A single amino‐acid difference confers major pharmacological variation between human and rodent 5HT1B receptors. Nature 360:161‐163.
   Pleskoff, O., Treboute, C., Brelot, A., Heveker, N., Seman, M., and Alizon, M. 1997. Identification of a chemokine receptor encoded by human cytomegalovirus as a cofactor for HIV‐1 entry. Science 276:1874‐1878.
   Poyner, D.R., Sexton, P.M., Marshall, I., Smith, D.M., Quirion, R., Born, W., Muff, R., Fischer, J.A., and Foord, S.M. 2002. International Union of Pharmacology. XXXII. The mammalian calcitonin gene‐related peptides, adrenomedullin, amylin, and calcitonin receptors. Pharmacol. Rev. 54:233‐246.
   Stamler, J.S., Jia, L., Eu, J.P., McMahon, T.J., Demchenko, I.T., Bonaventura, J., Gernert, K., and Piantadosi, C.A. 1997. Blood‐flow regulation by S‐nitrosohemoglobin in the physiological oxygen gradient. Science 276:2034‐2037.
   Strosberg, A.D. 1996. G protein coupled R7G receptors. Cancer Surv. 27:65‐83.
   Ward, R.J. and Milligan, G. 2004. Analysis of function of receptor‐G‐protein and receptor‐RGS fusion proteins. Methods Mol. Biol. 259:225‐247.
   Williams, M. and Gordon, E.M. 1996. Drug discovery: An overview. In A Textbook of Drug Design and Development, 2nd ed. (P. Krogsgaard‐Larsen, T. Liljefors, and U.Madsen, eds.) pp. 1‐34. Harwood Academic Publishers, Chur, Switzerland.
   Williams, M., Mehlin, C., Raddatz, R., and Triggle, D.J. 2005. Receptor targets in drug discovery and development. In Burger's Medicinal Chemistry and Drug Discovery, 7th Edition. Vol. 2, Drug Discovery and Development (D. Abraham, ed.), pp. 319‐355. John Wiley & Sons, Hoboken, N.J.
   Yokomizo, T., Izumi, T., Chang, K., Takuwa, Y., and Shimizu, T. 1997. A G‐protein‐coupled receptor for leukotriene B4 that mediates chemotaxis. Nature 387:620‐624.
   Zadina, J.E., Hackler, L., Ge, L.J., and Kastin, A.J. 1997. A potent and selective endogenous agonist for the mu‐opiate receptor. Nature 386:499‐502.
   Zambrowicz, B.P. and Sands, A.T. 2003. Knockouts model the 100 best‐selling drugs—Will they model the next 100? Nat. Rev. Drug. Discov. 2:38‐51.
Key References
   Kenakin, T. 2004. A pharmacology primer: Theory, application and methods. Elsevier, Inc., London, UK.
  An absolutely indispensable and comprehensive review of the current state of receptor theory. Required reading for anyone interested in receptor theory and pharmacology.
   Moss, S.J. and Henley, J. 2002. Receptor and Ion‐Channel Trafficking: Cell Biology of Ligand‐Gated and Voltage Sensitive Ion Channels. Oxford, London.
  Compendium on ion channels.
   Nature Reviews Drug Discovery GPCR Questionnaire Participants. 2004. The state of GPCR research in 2004. Nat. Rev. Drug Discov. 3:577‐626.
  Twenty GPCR experts answer questions relevant to drug discovery now and projecting into the future.
Internet Resources
   http://www.sigmaaldrich.com/Area_of_Interest/Life_Science/Cell_Signaling/Sigma_RBI_Handbook2.html
  The Sigma‐RBI Handbook of Receptor Classification and Signal Transduction.
GO TO THE FULL PROTOCOL:
PDF or HTML at Wiley Online Library