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Receptor (biochemistry)
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<h2 id="structure">Structure</h2> <p>The structures of receptors are very diverse and include the following major categories, among others: </p> <ul><li>Type 1: <a href="/facts/Ligand-gated_ion_channel/gN9RkNC2">Ligand-gated ion channels</a> (ionotropic receptors) – These receptors are typically the targets of fast neurotransmitters such as <a href="/facts/Acetylcholine/v1d3wRUd">acetylcholine</a> (nicotinic) and <a href="/facts/GABA/vRTeQQUG">GABA</a>; activation of these receptors results in changes in ion movement across a membrane. They have a heteromeric structure in that each subunit consists of the extracellular ligand-binding domain and a transmembrane domain which includes four transmembrane <a href="/facts/Alpha_helix/7CESPIYJ">alpha helices</a>. The ligand-binding cavities are located at the interface between the subunits.</li> <li>Type 2: <a href="/facts/G_protein-coupled_receptor/0arUMkQc">G protein-coupled receptors</a> (metabotropic receptors) – This is the largest family of receptors and includes the receptors for several hormones and slow transmitters e.g. dopamine, metabotropic glutamate. They are composed of seven transmembrane alpha helices. The loops connecting the alpha helices form extracellular and intracellular domains. The binding-site for larger peptide ligands is usually located in the extracellular domain whereas the binding site for smaller non-peptide ligands is often located between the seven alpha helices and one extracellular loop.<a class="footnote-ref" id="fnref:11" href="#fn:11"><sup>11</sup></a> The aforementioned receptors are coupled to different intracellular effector systems via <a href="/facts/G_protein/HKkcfgGP">G proteins</a>.<a class="footnote-ref" id="fnref:12" href="#fn:12"><sup>12</sup></a> G proteins are heterotrimers made up of 3 subunits: α (alpha), β (beta), and γ (gamma). In the inactive state, the three subunits associate together and the α-subunit binds GDP.<a class="footnote-ref" id="fnref:13" href="#fn:13"><sup>13</sup></a> G protein activation causes a conformational change, which leads to the exchange of GDP for GTP. GTP-binding to the α-subunit causes dissociation of the β- and γ-subunits.<a class="footnote-ref" id="fnref:14" href="#fn:14"><sup>14</sup></a> Furthermore, the three subunits, α, β, and γ have additional four main classes based on their primary sequence. These include Gs, Gi, Gq and G12.<a class="footnote-ref" id="fnref:15" href="#fn:15"><sup>15</sup></a></li> <li>Type 3: Kinase-linked and related receptors (see "<a href="/facts/Receptor_tyrosine_kinase/1oNWIdV8">Receptor tyrosine kinase</a>" and "<a href="/facts/Enzyme-linked_receptor/mE6dEy6k">Enzyme-linked receptor</a>") – They are composed of an extracellular domain containing the ligand binding site and an intracellular domain, often with enzymatic-function, linked by a single transmembrane alpha helix. The <a href="/facts/Insulin_receptor/PCEbQj6k">insulin receptor</a> is an example.</li> <li>Type 4: <a href="/facts/Nuclear_receptor/9aYqKxnM">Nuclear receptors</a> – While they are called nuclear receptors, they are actually located in the <a href="/facts/Cytoplasm/Wa0sE6xf">cytoplasm</a> and migrate to the <a href="/facts/Cell_nucleus/D7sFRa3c">nucleus</a> after binding with their ligands. They are composed of a <a href="/facts/C-terminus/ws4scHgT">C-terminal</a> ligand-binding region, a core <a href="/facts/DNA-binding_domain/x2vlHUKl">DNA-binding domain</a> (DBD) and an <a href="/facts/N-terminus/yKYpuaBJ">N-terminal</a> domain that contains the <i>AF1</i>(activation function 1) region. The core region has two zinc fingers that are responsible for recognizing the DNA sequences specific to this receptor. The N terminus interacts with other cellular transcription factors in a ligand-independent manner; and, depending on these interactions, it can modify the binding/activity of the receptor. Steroid and thyroid-hormone receptors are examples of such receptors.<a class="footnote-ref" id="fnref:16" href="#fn:16"><sup>16</sup></a></li></ul> <p>Membrane receptors may be isolated from cell membranes by complex extraction procedures using <a href="/facts/Liquid-liquid_extraction/qVfck5T1">solvents</a>, <a href="/facts/Detergents/4FLKXR6p">detergents</a>, and/or <a href="/facts/Affinity_purification/wCJjrPpt">affinity purification</a>. </p><p>The structures and actions of receptors may be studied by using biophysical methods such as <a href="/facts/X-ray_crystallography/WtI0F5DN">X-ray crystallography</a>, <a href="/facts/Nuclear_magnetic_resonance_spectroscopy_of_proteins/lCIXAFzQ">NMR</a>, <a href="/facts/Circular_dichroism/sMKgzpF2">circular dichroism</a>, and <a href="/facts/Dual_polarisation_interferometry/opICunH9">dual polarisation interferometry</a>. <a href="/facts/Computer_simulation/Re6o8vzN">Computer simulations</a> of the dynamic behavior of receptors have been used to gain understanding of their mechanisms of action. </p> <h2 id="binding-and-activation">Binding and activation</h2> <p>Ligand binding is an <a href="/facts/Chemical_equilibrium/y8ToYXHp">equilibrium</a> process. Ligands bind to receptors and dissociate from them according to the <a href="/facts/Law_of_mass_action/kw0j6Re9">law of mass action</a> in the following equation, for a ligand L and receptor, R. The brackets around chemical species denote their concentrations. </p> [ L ] + [ R ] ⇌ K d [ LR ] {\displaystyle {[{\ce {L}}]+[{\ce {R}}]{\ce {<=>[{K_{d}}]}}[{\text{LR}}]}} <p>One measure of how well a molecule fits a receptor is its binding affinity, which is inversely related to the <a href="/facts/Dissociation_constant/uvaKXf26">dissociation constant</a> <i>K</i><i>d</i>. A good fit corresponds with high affinity and low <i>K</i><i>d</i>. The final biological response (e.g. <a href="/facts/Second_messenger_system/J0eEENxQ">second messenger cascade</a>, muscle-contraction), is only achieved after a significant number of receptors are activated. </p><p>Affinity is a measure of the tendency of a ligand to bind to its receptor. Efficacy is the measure of the bound ligand to activate its receptor. </p> <h3>Agonists versus antagonists</h3> <p>Not every ligand that binds to a receptor also activates that receptor. The following classes of ligands exist: </p> <ul><li><i>(Full) <a href="/facts/Agonist/nz8U5NNp">agonists</a></i> are able to activate the receptor and result in a strong biological response. The natural <a href="/facts/Endogenous/DFkSLkRI">endogenous</a> ligand with the greatest <a href="/facts/Intrinsic_activity/wRugal9r">efficacy</a> for a given receptor is by definition a full agonist (100% efficacy).</li> <li><i><a href="/facts/Partial_agonist/VLm2vmgU">Partial agonists</a></i> do not activate receptors with maximal efficacy, even with maximal binding, causing partial responses compared to those of full agonists (efficacy between 0 and 100%).</li> <li><a href="/facts/Receptor_antagonist/PuXHVNdV"><i>Antagonists</i></a> bind to receptors but do not activate them. This results in a receptor blockade, inhibiting the binding of agonists and inverse agonists. Receptor antagonists can be competitive (or reversible), and compete with the agonist for the receptor, or they can be irreversible antagonists that form <a href="/facts/Covalent_bonds/EzMLf3Pz">covalent bonds</a> (or extremely high affinity non-covalent bonds) with the receptor and completely block it. The proton pump inhibitor <a href="/facts/Omeprazole/rJNAvWSR">omeprazole</a> is an example of an irreversible antagonist. The effects of irreversible antagonism can only be reversed by synthesis of new receptors.</li> <li><i><a href="/facts/Inverse_agonist/NDLoA789">Inverse agonists</a></i> reduce the activity of receptors by inhibiting their constitutive activity (negative efficacy).</li> <li><i><a href="/facts/Allosteric_regulation/alMRuyt9">Allosteric modulators</a></i>: They do not bind to the agonist-binding site of the receptor but instead on specific allosteric binding sites, through which they modify the effect of the agonist. For example, <a href="/facts/Benzodiazepines/IgbJr4jy">benzodiazepines</a> (BZDs) bind to the BZD site on the <a href="/facts/GABAA_receptor/6G4rAGb3">GABAA receptor</a> and potentiate the effect of endogenous GABA.</li></ul> <p>Note that the idea of receptor agonism and antagonism only refers to the interaction between receptors and ligands and not to their biological effects. </p> <h3>Constitutive activity</h3> <p>A receptor which is capable of producing a biological response in the absence of a bound ligand is said to display "constitutive activity".<a class="footnote-ref" id="fnref:17" href="#fn:17"><sup>17</sup></a> The constitutive activity of a receptor may be blocked by an <a href="/facts/Inverse_agonist/NDLoA789">inverse agonist</a>. The anti-obesity drugs <a href="/facts/Rimonabant/mySKelkE">rimonabant</a> and <a href="/facts/Taranabant/JphyMVd7">taranabant</a> are inverse agonists at the cannabinoid <a href="/facts/CB1_receptor/7b2tfePV">CB1 receptor</a> and though they produced significant weight loss, both were withdrawn owing to a high incidence of depression and anxiety, which are believed to relate to the inhibition of the constitutive activity of the cannabinoid receptor. </p><p>The <a href="/facts/GABAA_receptor/6G4rAGb3">GABAA receptor</a> has constitutive activity and conducts some basal current in the absence of an agonist. This allows <a href="/facts/Beta_carboline/zxgeBzgf">beta carboline</a> to act as an inverse agonist and reduce the current <i>below</i> basal levels. </p><p>Mutations in receptors that result in increased constitutive activity underlie some inherited diseases, such as <a href="/facts/Precocious_puberty/qUBb5nsD">precocious puberty</a> (due to mutations in luteinizing hormone receptors) and <a href="/facts/Hyperthyroidism/H9Eqmbgk">hyperthyroidism</a> (due to mutations in thyroid-stimulating hormone receptors). </p> <h2 id="theories-of-drug-receptor-interaction">Theories of drug-receptor interaction</h2> <h3>Occupation</h3> <p>Early forms of the <a href="/facts/Receptor_theory/aMjvRpbs">receptor theory</a> of pharmacology stated that a drug's effect is directly proportional to the number of receptors that are occupied.<a class="footnote-ref" id="fnref:18" href="#fn:18"><sup>18</sup></a> Furthermore, a drug effect ceases as a drug-receptor complex dissociates. </p><p><a href="/facts/Everhardus_Jacobus_Ari%C3%ABns/QUwx9Q3M">Ariëns</a> & Stephenson introduced the terms "affinity" & "efficacy" to describe the action of ligands bound to receptors.<a class="footnote-ref" id="fnref:19" href="#fn:19"><sup>19</sup></a><a class="footnote-ref" id="fnref:20" href="#fn:20"><sup>20</sup></a> </p> <ul><li><a href="/facts/Dissociation_constant/uvaKXf26">Affinity</a>: The ability of a drug to combine with a receptor to create a drug-receptor complex.</li> <li><a href="/facts/Intrinsic_activity/wRugal9r">Efficacy</a>: The ability of drug to initiate a response after the formation of drug-receptor complex.</li></ul> <h3>Rate</h3> <p>In contrast to the accepted <i>Occupation Theory</i>, Rate Theory proposes that the activation of receptors is directly proportional to the total number of encounters of a drug with its receptors per unit time. Pharmacological activity is directly proportional to the rates of dissociation and association, not the number of receptors occupied:<a class="footnote-ref" id="fnref:21" href="#fn:21"><sup>21</sup></a> </p> <ul><li>Agonist: A drug with a fast association and a fast dissociation.</li> <li>Partial-agonist: A drug with an intermediate association and an intermediate dissociation.</li> <li>Antagonist: A drug with a fast association & slow dissociation</li></ul> <h3>Induced-fit</h3> <p>As a drug approaches a receptor, the receptor alters the conformation of its binding site to produce drug—receptor complex. </p> <h3>Spare Receptors</h3> <p>In some receptor systems (e.g. acetylcholine at the neuromuscular junction in smooth muscle), agonists are able to elicit maximal response at very low levels of receptor occupancy (<1%). Thus, that system has spare receptors or a receptor reserve. This arrangement produces an economy of neurotransmitter production and release.<a class="footnote-ref" id="fnref:22" href="#fn:22"><sup>22</sup></a> </p> <h2 id="receptor-regulation">Receptor regulation</h2> <p>Cells can increase (<a href="/facts/Upregulate/6nRoa28r">upregulate</a>) or decrease (<a href="/facts/Downregulate/6nRoa28r">downregulate</a>) the number of receptors to a given <a href="/facts/Hormone/WFnBnINJ">hormone</a> or <a href="/facts/Neurotransmitter/LlpYFSU3">neurotransmitter</a> to alter their sensitivity to different molecules. This is a locally acting <a href="/facts/Feedback/XnuWH3zp">feedback</a> mechanism. </p> <ul><li>Change in the receptor conformation such that binding of the agonist does not activate the receptor. This is seen with ion channel receptors.</li> <li><a href="/facts/Protein_quaternary_structure/ukuyKJfj">Uncoupling</a> of the receptor <a href="/facts/G_protein-coupled_receptor/0arUMkQc">effector molecules</a> is seen with G protein-coupled receptors.</li> <li>Receptor <a href="/facts/Endocytosis/NJjChLNj">sequestration</a> (internalization),<a class="footnote-ref" id="fnref:23" href="#fn:23"><sup>23</sup></a> e.g. in the case of hormone receptors.</li></ul> <h2 id="examples-and-ligands">Examples and ligands</h2> <p>The ligands for receptors are as diverse as their receptors. GPCRs (7TMs) are a particularly vast family, with at least 810 members. There are also <a href="/facts/LGIC/gN9RkNC2">LGICs</a> for at least a dozen endogenous ligands, and many more receptors possible through different subunit compositions. Some common examples of ligands and receptors include:<a class="footnote-ref" id="fnref:24" href="#fn:24"><sup>24</sup></a> </p> <h3>Ion channels and G protein coupled receptors</h3> <p class="note">Main articles: <a href="/facts/Ligand-gated_ion_channel/gN9RkNC2">Ligand-gated ion channel</a> and <a href="/facts/G_protein-coupled_receptor/0arUMkQc">G protein-coupled receptor</a></p> <p>Some example ionotropic (LGIC) and metabotropic (specifically, GPCRs) receptors are shown in the table below. The chief neurotransmitters are glutamate and GABA; other neurotransmitters are <a href="/facts/Neuromodulation/mwjkrkHt">neuromodulatory</a>. This list is by no means exhaustive. </p> <table><tbody><tr><th rowspan="2">Endogenous Ligand</th><th colspan="3"><a href="/facts/LGIC/gN9RkNC2">Ion channel receptor (LGIC)</a></th><th colspan="3"><a href="/facts/7TM/0arUMkQc">G protein coupled receptor (GPCR)</a></th></tr><tr><th>Receptors</th><th><a href="/facts/Electric_current/Dc1xdnUX">Ion current</a><a class="footnote-ref" id="fnref:25" href="#fn:25"><sup>25</sup></a></th><th>Exogenous Ligand</th><th>Receptors</th><th><a href="/facts/G_protein/HKkcfgGP">G protein</a></th><th>Exogenous Ligand</th></tr><tr><td><a href="/facts/Glutamate/7oXbNcvu">Glutamate</a></td><td><a href="/facts/IGluR/RqSxqHqF">iGluRs</a>: <a href="/facts/NMDA_receptor/BqMhXEbU">NMDA</a>, <a href="/facts/AMPA_receptor/FJHDlvkg">AMPA</a>, and <a href="/facts/Kainate_receptors/RjdFLMIK">Kainate receptors</a></td><td>Na+, K+, Ca2+ <a class="footnote-ref" id="fnref:26" href="#fn:26"><sup>26</sup></a></td><td><a href="/facts/Ketamine/BtNSoqvh">Ketamine</a></td><td><a href="/facts/Glutamate_receptor/MGwpHHUA">Glutamate receptors</a>: <a href="/facts/MGluR/01pA40Kg">mGluRs</a></td><td>Gq or Gi/o</td><td>-</td></tr><tr><td><a href="/facts/GABA/vRTeQQUG">GABA</a></td><td><a href="/facts/GABAA/6G4rAGb3">GABAA</a>(including <a href="/facts/GABAA-rho/sutE5vXr">GABAA-rho</a>)</td><td>Cl− > HCO−3 <a class="footnote-ref" id="fnref:27" href="#fn:27"><sup>27</sup></a></td><td><a href="/facts/Benzodiazepines/IgbJr4jy">Benzodiazepines</a></td><td><a href="/facts/GABAB/dRomDjtq">GABAB receptor</a></td><td>Gi/o</td><td><a href="/facts/Baclofen/CI3r45RA">Baclofen</a></td></tr><tr><td><a href="/facts/Acetylcholine/v1d3wRUd">Acetylcholine</a></td><td><a href="/facts/Nicotinic_acetylcholine_receptor/k2s2pPHr">nAChR</a></td><td>Na+, K+, Ca2+<a class="footnote-ref" id="fnref:28" href="#fn:28"><sup>28</sup></a></td><td><a href="/facts/Nicotine/VQ6HcIrY">Nicotine</a></td><td><a href="/facts/Muscarinic_acetylcholine_receptor/caIdoqrW">mAChR</a></td><td><a href="/facts/Gq_subunit/Y8TVuq2U">Gq</a> or Gi</td><td><a href="/facts/Muscarine/9Sow1p3P">Muscarine</a></td></tr><tr><td><a href="/facts/Glycine/3nXI1hqW">Glycine</a></td><td><a href="/facts/Glycine_receptor/jwVgXdrJ">Glycine receptor</a> (GlyR)</td><td>Cl− > HCO−3 <a class="footnote-ref" id="fnref:29" href="#fn:29"><sup>29</sup></a></td><td><a href="/facts/Strychnine/oaAfW1xP">Strychnine</a></td><td>-</td><td>-</td><td>-</td></tr><tr><td><a href="/facts/Serotonin/EzY58q4a">Serotonin</a></td><td><a href="/facts/Serotonin_receptor/D6656QzQ">5-HT3 receptor</a></td><td>Na+, K+ <a class="footnote-ref" id="fnref:30" href="#fn:30"><sup>30</sup></a></td><td><a href="/facts/Cereulide/5FMQ1PnH">Cereulide</a></td><td><a href="/facts/Serotonin_receptor/D6656QzQ">5-HT1-2 or 4-7</a></td><td>Gs, Gi/o or Gq</td><td>-</td></tr><tr><td><a href="/facts/Adenosine_triphosphate/nB9bwgcU">ATP</a></td><td><a href="/facts/P2X_receptors/oCYaQG5I">P2X receptors</a></td><td>Ca2+, Na+, Mg2+ <a class="footnote-ref" id="fnref:31" href="#fn:31"><sup>31</sup></a></td><td>BzATP</td><td><a href="/facts/P2Y_receptors/PTXGk3WK">P2Y receptors</a></td><td>Gs, Gi/o or Gq</td><td>-</td></tr><tr><td><a href="/facts/Dopamine/5gNy8Xkd">Dopamine</a></td><td>No ion channels</td><td>-</td><td>-</td><td><a href="/facts/Dopamine_receptor/fgsjJwkL">Dopamine receptor</a></td><td>Gs or Gi/o</td><td>-</td></tr></tbody></table> <h3>Enzyme linked receptors</h3> <p class="note">Main article: <a href="/facts/Enzyme-linked_receptor/mE6dEy6k">Enzyme-linked receptor</a></p> <p>Enzyme linked receptors include <a href="/facts/Receptor_tyrosine_kinase/1oNWIdV8">Receptor tyrosine kinases</a> (RTKs), serine/threonine-specific protein kinase, as in bone morphogenetic protein and guanylate cyclase, as in atrial natriuretic factor receptor. Of the RTKs, 20 classes have been identified, with 58 different RTKs as members. Some examples are shown below: </p> <table><tbody><tr><th>RTK Class/Receptor Family</th><th>Member</th><th>Endogenous Ligand</th><th>Exogenous Ligand</th></tr><tr><td>I</td><td><a href="/facts/Epidermal_growth_factor_receptor/NLmnXKYY">EGFR</a></td><td><a href="/facts/Epidermal_growth_factor/CpyH5tYs">EGF</a></td><td><a href="/facts/Gefitinib/qnjmhugq">Gefitinib</a></td></tr><tr><td>II</td><td><a href="/facts/Insulin_receptor/PCEbQj6k">Insulin Receptor</a></td><td><a href="/facts/Insulin/oXG0myt1">Insulin</a></td><td><a href="/facts/Chaetochromin/2XECxloI">Chaetochromin</a></td></tr><tr><td>IV</td><td><a href="/facts/VEGF_receptor/FKA44l8U">VEGFR</a></td><td><a href="/facts/Vascular_endothelial_growth_factor/kNDc0Xj0">VEGF</a></td><td><a href="/facts/Lenvatinib/EgC9TEJq">Lenvatinib</a></td></tr></tbody></table> <h3>Intracellular Receptors</h3> <p class="note">Main article: <a href="/facts/Intracellular_receptor/Up8SbQIX">Intracellular receptor</a></p> <p>Receptors may be classed based on their mechanism or on their position in the cell. 4 examples of intracellular LGIC are shown below: </p> <table><tbody><tr><th>Receptor</th><th>Ligand</th><th>Ion current</th></tr><tr><td><a href="/facts/Cyclic_nucleotide-gated_ion_channel/Is1HhaIo">cyclic nucleotide-gated ion channels</a></td><td><a href="/facts/Cyclic_guanosine_monophosphate/zsge65d9">cGMP</a> (<a href="/facts/Visual_system/QVcuA27K">vision</a>), <a href="/facts/Cyclic_adenosine_monophosphate/flK2vwUe">cAMP</a> and <a href="/facts/Cyclic_guanosine_triphosphate/NAwoHjTW">cGTP</a> (<a href="/facts/Olfaction/t6ytFklU">olfaction</a>)</td><td>Na+, K+ <a class="footnote-ref" id="fnref:32" href="#fn:32"><sup>32</sup></a></td></tr><tr><td><a href="/facts/Inositol_triphosphate_receptor/qFX5WQSG">IP3 receptor</a></td><td><a href="/facts/Inositol_triphosphate/TDLGCWuG">IP3</a></td><td>Ca2+ <a class="footnote-ref" id="fnref:33" href="#fn:33"><sup>33</sup></a></td></tr><tr><td>Intracellular <a href="/facts/Adenosine_triphosphate/nB9bwgcU">ATP</a> receptors</td><td><a href="/facts/Adenosine_triphosphate/nB9bwgcU">ATP</a> (closes channel)<a class="footnote-ref" id="fnref:34" href="#fn:34"><sup>34</sup></a></td><td>K+ <a class="footnote-ref" id="fnref:35" href="#fn:35"><sup>35</sup></a></td></tr><tr><td><a href="/facts/Ryanodine_receptor/DrntsRrs">Ryanodine receptor</a></td><td>Ca2+</td><td>Ca2+ <a class="footnote-ref" id="fnref:36" href="#fn:36"><sup>36</sup></a></td></tr></tbody></table> <h2 id="role-in-health-and-disease">Role in health and disease</h2> <h3>In genetic disorders</h3> <p>Many <a href="/facts/Genetic_disorder/hFqt2NLn">genetic disorders</a> involve hereditary defects in receptor genes. Often, it is hard to determine whether the receptor is nonfunctional or the <a href="/facts/Hormone/WFnBnINJ">hormone</a> is produced at decreased level; this gives rise to the "pseudo-hypo-" group of <a href="/facts/Endocrinology/4SqQu1NN">endocrine disorders</a>, where there appears to be a decreased hormonal level while in fact it is the receptor that is not responding sufficiently to the hormone. </p> <h3>In the immune system</h3> <p class="note">Main article: <a href="/facts/Immune_receptor/myRgAvX0">Immune receptor</a></p> <p>The main receptors in the <a href="/facts/Immune_system/HRCTf1pb">immune system</a> are <a href="/facts/Pattern_recognition_receptors/ItopNrK0">pattern recognition receptors</a> (PRRs), <a href="/facts/Toll-like_receptor/hj4qIWP8">toll-like receptors</a> (TLRs), <a href="/facts/Killer_activated_receptor/HPazhzLl">killer activated</a> and <a href="/facts/Killer_inhibitor_receptor/pTEygp94">killer inhibitor receptors</a> (KARs and KIRs), <a href="/facts/Complement_receptor/EsI570Ic">complement receptors</a>, <a href="/facts/Fc_receptors/hpv5q6Hu">Fc receptors</a>, <a href="/facts/B_cell_receptor/J6qRYYkN">B cell receptors</a> and <a href="/facts/T_cell_receptor/zDqyWyG4">T cell receptors</a>.<a class="footnote-ref" id="fnref:37" href="#fn:37"><sup>37</sup></a> </p> <h2 id="see-also">See also</h2> <ul><li><a href="/facts/Ki_Database/lcpb61cI">Ki Database</a></li> <li><a href="/facts/Ion_channel_linked_receptors/gN9RkNC2">Ion channel linked receptors</a></li> <li><a href="/facts/Neuropsychopharmacology/Lzx7jTc3">Neuropsychopharmacology</a></li> <li><a href="/facts/Schild_regression/uehLHchx">Schild regression</a> for ligand receptor inhibition</li> <li><a href="/facts/Signal_transduction/1bs0Me6w">Signal transduction</a></li> <li><a href="/facts/Stem_cell_marker/NJlfvSaC">Stem cell marker</a></li> <li><a href="/facts/List_of_MeSH_codes_(D12.776)/jqAkNjFU">List of MeSH codes (D12.776)</a></li> <li><a href="/facts/Receptor_theory/aMjvRpbs">Receptor theory</a></li></ul> <h2 id="notes">Notes</h2> <h2 id="external-links">External links</h2> <ul><li><a href="http://www.iuphar-db.org">IUPHAR GPCR Database and Ion Channels Compendium</a> <a href="https://web.archive.org/web/20190323064157/http://iuphar-db.org/">Archived</a> 2019-03-23 at the <a href="/facts/Wayback_Machine/nmQ3a6JC">Wayback Machine</a></li> <li><a href="http://www.receptome.org/">Human plasma membrane receptome</a> <a href="https://web.archive.org/web/20190915010207/http://www.receptome.org/">Archived</a> 2019-09-15 at the <a href="/facts/Wayback_Machine/nmQ3a6JC">Wayback Machine</a></li> <li><a href="https://meshb.nlm.nih.gov/record/ui?name=Cell+surface+receptors">Cell+surface+receptors</a> at the U.S. National Library of Medicine <a href="/facts/Medical_Subject_Headings/C57g2JuF">Medical Subject Headings</a> (MeSH)</li></ul> <h2 id="references">References</h2> <ol> <li id="fn:1"><p>Guyton, Arthur C.; Hall, John E. 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Rang & Dale's Pharmacology (7th ed.). Elsevier Churchill Livingstone. ISBN 978-0-7020-3471-8. <a href="978-0-7020-3471-8" target="_blank">978-0-7020-3471-8</a> <a href="#fnref:22" class="footnote-back-ref">↩</a></p></li> <li id="fn:23"><p>Boulay G, Chrétien L, Richard DE, Guillemette G (November 1994). "Short-term desensitization of the angiotensin II receptor of bovinde adrenal glomerulosa cells corresponds to a shift from a high to low affinity state". Endocrinology. 135 (5): 2130–6. doi:10.1210/en.135.5.2130. PMID 7956936. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:23" class="footnote-back-ref">↩</a></p></li> <li id="fn:24"><p>Boulpaep EL, Boron WF (2005). Medical Physiology: A Cellular and Molecular Approach. St. Louis, Mo: Elsevier Saunders. p. 90. ISBN 1-4160-2328-3. <a href="1-4160-2328-3" target="_blank">1-4160-2328-3</a> <a href="#fnref:24" class="footnote-back-ref">↩</a></p></li> <li id="fn:25"><p>Different LGICs conduct currents of different ions. This is accomplished with selectivity filters, such as the selectivity filter of the K+ ion channel <a href="/wiki/Ions" target="_blank">/wiki/Ions</a> <a href="#fnref:25" class="footnote-back-ref">↩</a></p></li> <li id="fn:26"><p>Boulpaep EL, Boron WF (2005). Medical Physiology: A Cellular and Molecular Approach. St. Louis, Mo: Elsevier Saunders. p. 90. ISBN 1-4160-2328-3. <a href="1-4160-2328-3" target="_blank">1-4160-2328-3</a> <a href="#fnref:26" class="footnote-back-ref">↩</a></p></li> <li id="fn:27"><p>Boulpaep EL, Boron WF (2005). Medical Physiology: A Cellular and Molecular Approach. St. Louis, Mo: Elsevier Saunders. p. 90. ISBN 1-4160-2328-3. <a href="1-4160-2328-3" target="_blank">1-4160-2328-3</a> <a href="#fnref:27" class="footnote-back-ref">↩</a></p></li> <li id="fn:28"><p>Boulpaep EL, Boron WF (2005). Medical Physiology: A Cellular and Molecular Approach. St. Louis, Mo: Elsevier Saunders. p. 90. ISBN 1-4160-2328-3. <a href="1-4160-2328-3" target="_blank">1-4160-2328-3</a> <a href="#fnref:28" class="footnote-back-ref">↩</a></p></li> <li id="fn:29"><p>Boulpaep EL, Boron WF (2005). Medical Physiology: A Cellular and Molecular Approach. St. Louis, Mo: Elsevier Saunders. p. 90. ISBN 1-4160-2328-3. <a href="1-4160-2328-3" target="_blank">1-4160-2328-3</a> <a href="#fnref:29" class="footnote-back-ref">↩</a></p></li> <li id="fn:30"><p>Boulpaep EL, Boron WF (2005). Medical Physiology: A Cellular and Molecular Approach. St. Louis, Mo: Elsevier Saunders. p. 90. ISBN 1-4160-2328-3. <a href="1-4160-2328-3" target="_blank">1-4160-2328-3</a> <a href="#fnref:30" class="footnote-back-ref">↩</a></p></li> <li id="fn:31"><p>Boulpaep EL, Boron WF (2005). Medical Physiology: A Cellular and Molecular Approach. St. Louis, Mo: Elsevier Saunders. p. 90. ISBN 1-4160-2328-3. <a href="1-4160-2328-3" target="_blank">1-4160-2328-3</a> <a href="#fnref:31" class="footnote-back-ref">↩</a></p></li> <li id="fn:32"><p>Boulpaep EL, Boron WF (2005). Medical Physiology: A Cellular and Molecular Approach. St. Louis, Mo: Elsevier Saunders. p. 90. ISBN 1-4160-2328-3. <a href="1-4160-2328-3" target="_blank">1-4160-2328-3</a> <a href="#fnref:32" class="footnote-back-ref">↩</a></p></li> <li id="fn:33"><p>Boulpaep EL, Boron WF (2005). Medical Physiology: A Cellular and Molecular Approach. St. Louis, Mo: Elsevier Saunders. p. 90. ISBN 1-4160-2328-3. <a href="1-4160-2328-3" target="_blank">1-4160-2328-3</a> <a href="#fnref:33" class="footnote-back-ref">↩</a></p></li> <li id="fn:34"><p>Boulpaep EL, Boron WF (2005). Medical Physiology: A Cellular and Molecular Approach. St. Louis, Mo: Elsevier Saunders. p. 90. ISBN 1-4160-2328-3. <a href="1-4160-2328-3" target="_blank">1-4160-2328-3</a> <a href="#fnref:34" class="footnote-back-ref">↩</a></p></li> <li id="fn:35"><p>Boulpaep EL, Boron WF (2005). Medical Physiology: A Cellular and Molecular Approach. St. Louis, Mo: Elsevier Saunders. p. 90. ISBN 1-4160-2328-3. <a href="1-4160-2328-3" target="_blank">1-4160-2328-3</a> <a href="#fnref:35" class="footnote-back-ref">↩</a></p></li> <li id="fn:36"><p>Boulpaep EL, Boron WF (2005). Medical Physiology: A Cellular and Molecular Approach. St. Louis, Mo: Elsevier Saunders. p. 90. ISBN 1-4160-2328-3. <a href="1-4160-2328-3" target="_blank">1-4160-2328-3</a> <a href="#fnref:36" class="footnote-back-ref">↩</a></p></li> <li id="fn:37"><p>Waltenbaugh C, Doan T, Melvold R, Viselli S (2008). Immunology. Philadelphia: Wolters Kluwer Health/Lippincott Williams & Wilkins. p. 20. ISBN 978-0-7817-9543-2. <a href="978-0-7817-9543-2" target="_blank">978-0-7817-9543-2</a> <a href="#fnref:37" class="footnote-back-ref">↩</a></p></li> </ol>