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20-September-2008 09:29:07 - Receptor biochemistry This article or section contains too much jargon and may need simplification or further explanation. Please discuss this issue on the talk page, and/or remove or explain jargon terms used in the article. ing help is available. May 2008 For other uses, see Receptor. In biochemistry, a receptor is a protein molecule, embedded in either the plasma membrane or cytoplasm of a cell, to which a mobile signaling or signal molecule may attach. A molecule which binds to a receptor is called a ligand, and may be a peptide such as a neurotransmitter, a hormone, a pharmaceutical drug, or a toxin, and when such binding occurs, the receptor ordinarily initiates a cellular response, though some ligands merely block receptors without inducing any response. Ligand-induced changes in receptors result in physiological changes which constitute the biological activity of the ligands. Contents 1 Overview 2 Binding and activation 2.1 Constitutive activity 3 Agonists versus antagonists 4 Peripheral membrane protein receptors 5 Transmembrane receptors 5.1 Metabotropic receptors 5.1.1 G protein-coupled receptors 5.1.2 Receptor tyrosine kinases 5.1.3 Guanylyl cyclase receptors 5.2 Ionotropic receptors 5.2.1 Extracellular ligands 5.2.2 Intracellular ligands 6 Intracellular receptors 6.1 Transcription factors 6.2 Various 7 Role in Genetic Disorders 8 Receptor Regulation 9 In immune system 10 See also 11 References 12 External links Overview The shapes and actions of receptors are studied by X-ray crystallography and computer modelling, which have advanced the understanding of drug action at the binding sites of receptors. Transmembrane receptor:E=extracellular space; I=intracellular space; P=plasma membrane Transmembrane receptor:E=extracellular space; I=intracellular space; P=plasma membrane Depending on their functions and ligands, several types of receptors may be identified: Some receptor proteins are peripheral membrane proteins. Many hormone and neurotransmitter receptors are transmembrane proteins: transmembrane receptors are embedded in the phospholipid bilayer of cell membranes, that allow the activation of signal transduction pathways in response to the activation by the binding molecule, or ligand. Metabotropic receptors are coupled to G proteins and affect the cell indirectly through enzymes which control ion channels. Ionotropic receptors contain a central pore which functions as a ligand-gated ion channel. Another major class of receptors are intracellular proteins such as those for steroid and intracrine peptide hormone receptors. These receptors often can enter the cell nucleus and modulate gene expression in response to the activation by the ligand. Binding and activation Ligand binding is an equilibrium process. Ligands bind to receptors and dissociate from them according to the law of mass action. : \left\mathrmLigand\right \cdot \left\mathrmReceptor\right\;\;\overset K_d\rightleftharpoons\;\;\left\mboxLigand-receptor complex\right the brackets stand for concentrations One measure of how well a molecule fits a receptor is the binding affinity, which is inversely related to the dissociation constant Kd. A good fit corresponds with high affinity and low Kd. The activation of the second messenger cascade, and the final biological response, are achieved only when, after a certain delay, a significant number of receptors are activated. If the receptor exists in two states see this picture, then the ligand binding must account for these two receptor states. For a more detailed discussion of two-state binding, which is thought to occur as an activation mechanism in many receptors see this link. Constitutive activity A receptor which is capable of producing its biological response in the absence of a bound ligand is said to display constitutive activity. 1 The constitutive activity of receptors may be blocked by inverse agonist binding. Mutations in receptors that result in increased constitutive activity underlie some inherited diseases, such as precocious puberty due to mutations in luteinizing hormone receptors and hyperthyroidism due to mutations in thyroid-stimulating hormone receptors. Psychostimulants act as inverse agonists on dopamine receptors. For the use of statistical mechanics in a quantitative study of the ligand-receptor binding affinity, see the comprehensive article2 on the configuration integral. Agonists versus antagonists Not every ligand that binds to a receptor also activates the receptor. The following classes of ligands exist: Full agonists are able to activate the receptor and result in a maximal biological response. Most natural ligands are full agonists. Partial agonists do not activate receptors thoroughly, causing responses which are partial compared to those of full agonists. Antagonists bind to receptors but do not activate them. This results in receptor blockage, inhibiting the binding of other agonists. Inverse agonists reduce the activity of receptors by inhibiting their constitutive activity. Peripheral membrane protein receptors See also: Peripheral membrane protein Transmembrane receptors Main article: Transmembrane receptor Metabotropic receptors Main article: Metabotropic receptor G protein-coupled receptors Main article: G protein-coupled receptor These receptors are also known as seven transmembrane receptors or 7TM receptors, because they pass through the membrane seven times. Muscarinic acetylcholine receptor Acetylcholine and Muscarine Adenosine receptors Adenosine Adrenoceptors also known as Adrenergic receptors, for adrenaline, and other structurally related hormones and drugs GABA receptors, Type-B γ-Aminobutyric acid or GABA Angiotensin receptors Angiotensin Cannabinoid receptors Cannabinoids Cholecystokinin receptors Cholecystokinin Dopamine receptors Dopamine Glucagon receptors Glucagon Metabotropic glutamate receptors Glutamate Histamine receptors Histamine Olfactory receptors for the sense of smell Opioid receptors Opioids Rhodopsin a photoreceptor Secretin receptors Secretin Serotonin receptors, except Type-3 Serotonin, also known as 5-Hydroxytryptamine or 5-HT Somatostatin receptors Somatostatin Calcium-sensing receptor Calcium Chemokine receptors Chemokines many more ... Please help improve this section by expanding it. Further information might be found on the talk page or at requests for expansion. June 2008 Receptor tyrosine kinases Main article: Receptor tyrosine kinase These receptors detect ligands and propagate signals via the tyrosine kinase of their intracellular domains. This family of receptors includes; Erythropoietin receptor Erythropoietin Insulin receptor Insulin Eph receptors Insulin-like growth factor 1 receptor various other growth factor and cytokine receptors .... Guanylyl cyclase receptors GC-A GC-B: receptors for Atrial-natriuretic peptide ANP and other natriuretic peptides GC-C: Guanylin receptor Ionotropic receptors Ionotropic receptors are heteromeric or homomeric oligomers 3. They are receptors that respond to extracellular ligands and receptors that respond to intracellular ligands. Extracellular ligands Receptor Ligand Ion current Nicotinic acetylcholine receptor Acetylcholine, Nicotine Na+, K+, Ca2+ 3 Glycine receptor GlyR Glycine, Strychnine Cl- HCO-3 3 GABA receptors: GABA-A, GABA-C GABA Cl- HCO-3 3 Glutamate receptors: NMDA receptor, AMPA receptor, and Kainate receptor Glutamate Na+, K+, Ca2+ 3 5-HT3 receptor Serotonin Na+, K+ 3 P2X receptors ATP Ca2+, Na+, Mg2+ 3 Intracellular ligands Receptor Ligand Ion current cyclic nucleotide-gated ion channels cGMP vision, cAMP and cGTP olfaction Na+, K+ 3 IP3 receptor IP3 Ca2+ 3 Intracellular ATP receptors ATP closes channel3 K+ 3 Ryanodine receptor Ca2+ Ca2+ 3 The entire repertoire of human plasma membrane receptors is listed at the Human Plasma Membrane Receptome http://receptome.stanford.edu. Intracellular receptors Main article: Intracellular receptor Transcription factors nuclear receptor: Steroid hormone receptor Various Ionotropic receptors IP3 receptor above sigma1 neurosteroids G protein-coupled receptors 4 Role in Genetic Disorders Many genetic disorders involve herary defects in receptor genes. Often, it is hard to determine whether the receptor is nonfunctional or the hormone is produced at decreased level; this gives rise to the pseudo-hypo- group of endocrine disorders, where there appears to be a decreased hormonal level while in fact it is the receptor that is not responding sufficiently to the hormone. Receptor Regulation Cells can increase upregulate or decrease downregulate the number of receptors to a given hormone or neurotransmitter to alter its sensitivity to this molecule. This is a locally acting feedback mechanism. Receptor desensitization Ligand-bound desensitation of receptors was first characterized by Katz and Thesleff in the nicotine acetylcholine receptor56 Prolonged or repeated exposure to a stimulus often results in decreased responsiveness of that receptor for a stimulus. Receptor desensitization results in altered affinity for the ligand.5 Receptor desensitization can modeled by a two-state model that also predicts that antagonists combined with agonists can prevent receptor desensitization 7 See this link 1 for detailed molecular description Desensitation may be accomplished by Receptor phosphorylation.8 Uncoupling of receptor effector molecules. Receptor sequestration internalization.8 In immune system Main article: Immune receptor The main receptors in the immune system are pattern recognition receptors PRRs, Toll-like receptors TLRs, killer activated and killer inhibitor receptors KARs and KIRs, complement receptors, Fc receptors, B cell receptors and T cell receptors. 9 v d e Transmembrane receptors: immune receptors Cytokine receptor Type I: Interleukins 2, 3, 4, 5, 6, 7, 9, 11, 12, 13, 15, 21, 23, 27, CSF receptors EPO, GM-CSF, G-CSF, GH, prolactin, Oncostatin M,Leukemia inhibitory factor - common subunits Common gamma chain, common beta chain, CSF2RB Type II: Interleukins 10, 20, 22, 28 - interferon -α/β, -γ immunoglobulin superfamily: CSF1, C-kit, IL-1, IL-18 Tumor necrosis factor: CD27, CD30, CD40, CD120, Lymphotoxin β Chemokines: IL-8 α, β, CCR1,CXCR4 Other: IL-17, TGF-beta 1, 2 Pattern recognition/Toll-like TLR 1 - TLR 2 - TLR 3 - TLR 4 - TLR 5 - TLR 6 - TLR 7 - TLR 8 - TLR 9 - TLR 10 Fc receptor ε FcεRI, FcεRII - γ FcγRI, FcγRII, FcγRIII - α/μ FcαRI, Fcα/μR - Neonatal Lymphocyte homing receptor CD44 - L-selectin - VLA-4 - LFA-1 other Antigen receptor B-cell, T cell - Complement - Formyl peptide - Immunophilins - Integrin - Killer-cell immunoglobulin-like - Scavenger See also Signal transduction Neuropsychopharmacology Schild regression for ligand receptor inhibition Ki Database :MeSH D12.776#MeSH D12.776.543.750 --- receptors.2C cell surface References ^ Milligan G December 2003. Constitutive activity and inverse agonists of G protein-coupled receptors: a current perspective. Mol. Pharmacol. 64 6: 1271-6. doi:10.1124/mol.64.6.1271. PMID 14645655. ^ Vu-Quoc, L., Configuration integral statistical mechanics, 2008. ^ a b c d e f g h i j k l Medical Physiology, Boron Boulpaep, ISBN 1-4160-2328-3, Elsevier Saunders 2005. Updated ion. Page 90. ^ Gobeil F, et al. 2006 G-protein-coupled receptors signalling at the cell nucleus: an emerging paradigm. Can J Physiol Pharmacol. 2006 Mar-Apr;843-4:287-97. PMID 16902576 ^ a b Y. Sun, R. Olson, M. Horning, N. Armstrong, M. Mayer and E. Gouaux. 2002 Mechanism of glutamate receptor desensitization Nature 417, 245-253 ^ S. Pitchford, J.W. Day, A. Gordon and D. Mochly-Rosen. 1992 Acetylcholine receptor desensitization is Regulate by activation-induced extracellular adenosine accumulation. The Journal of Neuroscience, 1.311: 4540-4544. ^ Lanzara, Optimal Agonist/Antagonist Combinations Maintain Receptor Response by Preventing Rapid Beta-1 adrenergic Receptor Desensitization Intl. J. Pharmacol., 12: 122-131, 2005.http://www.bio-balance.com/ijp.pdf ^ a b G. Boulay, L. Chrbtien, D.E. Richard, AND G. Guillemettes. 1994 Short-Term Desensitization of the Angiotensin II Receptor of Bovine Adrenal Glomerulosa Cells Corresponds to a Shift from a High to a Low Affinity State. Endocrinology Vol. 135. No. 5 2130-2136 ^ Lippincott's Illustrated Reviews: Immunology. Paperback: 384 pages. Publisher: Lippincott Williams Wilkins; July 1, 2007. Language: English. ISBN-10: 0781795435. ISBN-13: 978-0781795432. Page 20 External links IUPHAR GPCR Database and Ion Channels Compendium MeSH Cell+surface+receptors v d e Cell signaling Key concepts Ligand - Signal transduction - Apoptosis - Second messenger system Ca2+ signaling, Lipid signaling Processes Paracrine - Autocrine - Juxtacrine - Neurotransmitters - Endocrine Neuroendocrine Types of proteins Receptor Transmembrane, Intracellular - Transcription factor General, Preinitiation complex, TFIID, TFIIH - Adaptor protein receptor ligands hormones, neurotransmitters, cytokines, growth factors v d e Transmembrane receptor: G protein-coupled receptors Class A: Rhodopsin like Adrenergic α1 A, B, D, α2 A, B, C, β1, β2, β3 Eicosanoid CysLT 1, 2, LTB4 1, 2, FPRL1, OXE, Prostaglandin DP, EP 1, 2, 3, 4, PGF, Prostacyclin, Thromboxane Neuropeptide B/W 1, 2, FF 1, 2, S, Y 1, 2, 4, 5 Orphan GPR 1, 3, 4, 6, 12, 15, 17, 18, 19, 20, 21, 22, 23, 25, 26, 27, 31, 32, 33, 34, 35, 37, 39, 42, 44, 45, 50, 52, 55, 61, 62, 63, 65, 68, 75, 77, 78, 79, 82, 83, 84, 85, 87, 88, 92, 101, 103, 119, 120, 132, 135, 139, 141, 142, 146, 148, 149, 150, 151, 152, 153, 160, 161, 162, 171, 172, 173, 174, 176, 177, 182 Purinergics Adenosine A1, A2a, A2b, A3, P2Y, 1, 2, 4, 5, 6, 8, 9, 10, 11, 12, 13, 14 Serotonin all but 5-HT3 5-HT1 A, B, D, E, F, 5-HT2 A, B, C, 5-HT 4, 5A, 6, 7 Other Acetylcholine M1, M2, M3, M4, M5 - Adrenomedullin - Anaphylatoxin C3a, C5a - Angiotensin 1, 2 - Apelin - Bile acid - Bombesin BRS3, GRPR, NMBR - Bradykinin B1, B2 - Cannabinoid CB1, CB2 - Chemokine - Cholecystokinin A, B - Dopamine D1, D2, D3, D4, D5 - EBI2 - Endothelin A, B - Estrogen - Formyl peptide 1, L1, L2 - Free fatty acid 1, 2, 3, 4 - FSH - Galanin 1, 2, 3 - Gonadotropin-releasing hormone 1, 2 - Ghrelin - Histamine H1, H2, H3, H4 - Kisspeptin - Luteinizing hormone/choriogonadotropin - Lysophospholipid 1, 2, 3, 4, 5, 6, 7, 8 - MAS 1, 1L, D, E, F, G, X1, X2, X3, X4 - Melanocortin 1, 2, 3, 4, 5 - MCHR 1, 2 - Melatonin 1A, 1B- Motilin - neuromedin B, U 1, 2 - Neurotensin 1, 2 - Opioid Delta, Kappa, Mu, Nociceptin, but not Sigma - Olfactory - Opsin 3, 4, 5, 1LW, 1MW, 1SW, RGR, RRH - Orexin 1, 2 - Oxytocin - Oxoglutarate - PAF - Prokineticin 1, 2 - Prolactin-releasing peptide - Protease-activated 1, 2, 3, 4 - Relaxin 1, 2, 3, 4 - Somatostatin 1, 2, 3, 4, 5 - SREB - Succinate - TAAR 1, 2, 3, 5, 6, 8, 9 - Tachykinin 1, 2, 3 - Thyrotropin - Thyrotropin-releasing hormone - Urotensin-II - Vasopressin 1A, 1B, 2 Class B: Secretin like Brain-specific angiogenesis inhibitor 1, 2, 3 - Cadherin 1, 2, 3 - Calcitonin - CD97 - Corticotropin-releasing hormone 1, 2 - EMR 1, 2, 3 - Glucagon GR, GIPR, GLP1R, GLP2R - Growth hormone releasing hormone - PACAPR1- GPR 56, 64, 97, 98, 110, 111, 112, 113, 114, 115, 116, 123, 124, 125, 126, 128, 133, 143, 144, 157 - Latrophilin 1, 2, 3, ELTD1 - Parathyroid hormone 1, 2 - Secretin - Vasoactive intestinal peptide 1, 2 Class C: Metabotropic glutamate / pheromone Calcium-sensing receptor - GABA B 1, 2 - Glutamate receptor Metabotropic glutamate 1, 2, 3, 4, 5, 6, 7, 8 - GPRC6A - GPR 156, 158, 179 - RAIG 1, 2, 3, 4 - Taste receptors TAS1R 1, 2, 3 TAS2R 1, 3, 4, 5, 8, 9, 10, 12, 13, 14, 16, 38, 39, 40, 41, 43, 44, 45, 46, 47, 48, 49, 50 Frizzled / Smoothened Frizzled 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 - Smoothened v d e Transmembrane receptor, tyrosine kinase: receptor tyrosine kinases EC 2.7.10.1 I EGF HER2/neu, Her 3, Her 4 II Insulin - IGF-1 III Platelet-derived growth factor IV Fibroblast growth factor FGFR1, FGFR2, FGFR3 V VEGF receptors - Flk-1 - Flt-1 VII TRK: TrkA - TrkB - TrkC other VIII: Eph B2 - XI: Angiopoietin Receptors: Tie-1 Tie-2 - XIV: RET - XVI: Related to receptor tyrosine kinase - XVII: MuSK Retrieved from http://en..org/wiki/Receptor_biochemistry Categories: Cell signaling | Signal transduction | Cell biology | Membrane biology | ReceptorsHidden categories: Cleanup from May 2008 | articles needing style ing from May 2008 | All articles needing style ing | Articles to be expanded since June 2008 | All articles to be expanded Views Article Discussion this page History Personal tools Log in / create account Navigation Main page Contents Featured content Current events Random article Search Go Search Interaction Community portal Recent changes Contact Donate to Help Toolbox What links here Related changes Upload file Special pages Printable version Permanent link Cite this page Languages العربية ÄŒesky Dansk Deutsch Español Français Italiano עברית Nederlands 日本語 Polski Português Română РуÑ?Ñ?кий SlovenÄ?ina SlovenÅ¡Ä?ina Suomi Svenska ไทย УкраїнÑ?ька ä¸æ–‡ This page was last modified on 11 August 2008, at 02:58
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