In biochemistry and pharmacology , receptors are chemical structures, composed of protein , that receive and transduce signals that may be integrated into biological systems. These signals are typically chemical messengers which bind to a receptor and produce physiological responses such as change in the electrical activity of a cell . For example, GABA , an inhibitory neurotransmitter , inhibits electrical activity of neurons by binding to GABA A receptors . There are three main ways the action of the receptor can be classified: relay of signal, amplification, or integration. Relaying sends the signal onward, amplification increases the effect of a single ligand , and integration allows the signal to be incorporated into another biochemical pathway.
22-417: 4DOH 53833 213208 ENSG00000174564 ENSMUSG00000044244 Q6UXL0 E9Q9A6 NM_144717 NM_001033543 NM_001037246 NP_653318 NP_001028715 Interleukin 20 receptor , beta subunit (IL20R2 or IL20RB) is a subunit of the interleukin-20 receptor and interleukin-22 receptor . It is believed to be involved in both pro-inflammatory and anti-inflammatory responses. IL20RB
44-402: A bound ligand is said to display "constitutive activity". The constitutive activity of a receptor may be blocked by an inverse agonist . The anti-obesity drugs rimonabant and taranabant are inverse agonists at the cannabinoid CB1 receptor and though they produced significant weight loss, both were withdrawn owing to a high incidence of depression and anxiety, which are believed to relate to
66-557: A particular structure. This has been analogously compared to how locks will only accept specifically shaped keys . When a ligand binds to a corresponding receptor, it activates or inhibits the receptor's associated biochemical pathway, which may also be highly specialised. Receptor proteins can be also classified by the property of the ligands. Such classifications include chemoreceptors , mechanoreceptors , gravitropic receptors , photoreceptors , magnetoreceptors and gasoreceptors. The structures of receptors are very diverse and include
88-410: A receptor is its binding affinity, which is inversely related to the dissociation constant K d . A good fit corresponds with high affinity and low K d . The final biological response (e.g. second messenger cascade , muscle-contraction), is only achieved after a significant number of receptors are activated. Affinity is a measure of the tendency of a ligand to bind to its receptor. Efficacy
110-470: A transcription factor, which can gene expression. IL20RB mRNA is present in some immune cells, including monocytes , natural killer cells , B-cells , T-cells , and some hematopoietic stem cells . It is known what role IL20RB plays in these cells. IL20RB is linked with atherosclerosis and gastrointestinal diseases , although its specific roles are unknown. IL20RB mRNA is expressed in retinal ganglion cells and optic nerves in rats. Mutations in
132-464: Is a locally acting feedback mechanism. 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 LGICs for at least a dozen endogenous ligands, and many more receptors possible through different subunit compositions. Some common examples of ligands and receptors include: Some example ionotropic (LGIC) and metabotropic (specifically, GPCRs) receptors are shown in
154-411: Is found in many organ resident effector cells such as keratinocytes at the skin epidermis , osteoclasts , found in bones, and epithelial cells of the intestine and trachea . IL20RB is also found in some immune cells. The subunit has been linked with multiple diseases, including gastrointestinal diseases and glaucoma. IL20RB is a β-chain with a short intracellular domain . IL20RB, along with
176-425: Is not responding sufficiently to the hormone. 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 . Intracellular receptor Intracellular receptors are globular protein receptors located inside
198-411: Is referred to as its endogenous ligand. E.g. the endogenous ligand for the nicotinic acetylcholine receptor is acetylcholine , but it can also be activated by nicotine and blocked by curare . Receptors of a particular type are linked to specific cellular biochemical pathways that correspond to the signal. While numerous receptors are found in most cells, each receptor will only bind with ligands of
220-411: Is the measure of the bound ligand to activate its receptor. Not every ligand that binds to a receptor also activates that receptor. The following classes of ligands exist: Note that the idea of receptor agonism and antagonism only refers to the interaction between receptors and ligands and not to their biological effects. A receptor which is capable of producing a biological response in the absence of
242-424: The cell rather than on its cell membrane . The word intracellular means "within or inside a cell." Molecules that cross a cell membrane to bind with a receptor are generally nonpolar and may be relatively small. These molecules are also known as ligands . Hormones that use intracellular receptors include thyroid , aldosterone , and steroid hormones . Examples are the class of nuclear receptors located in
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#1733085469448264-422: The receptor theory of pharmacology stated that a drug's effect is directly proportional to the number of receptors that are occupied. Furthermore, a drug effect ceases as a drug-receptor complex dissociates. Ariëns & Stephenson introduced the terms "affinity" & "efficacy" to describe the action of ligands bound to receptors. In contrast to the accepted Occupation Theory , Rate Theory proposes that
286-667: The IL-20 receptor, alpha subunit, form the heterodimeric type I interleukin-20 receptor, which binds the cytokines IL-19 , IL-20 and IL-24 . IL20RB also associates with IL-22 receptor, to form the heterodimeric type II interleukin-20 receptor, which also binds IL-20 and IL-24. After a cytokine binds both the IL20RB and the alpha subunit of the IL20 receptor, a signal is sent through the JAK-STAT signaling pathway. This signaling pathway leads STAT to act as
308-704: The IL20RB gene are associated with glaucoma . The specific links between IL20RB and glaucoma are unknown, but IL20RB does not have a causative effect on the disease, instead contributing to an increased risk of the disease along with other factors, such as intraocular pressure . This article on a gene on human chromosome 3 is a stub . You can help Misplaced Pages by expanding it . Receptor (biochemistry) Receptor proteins can be classified by their location. Cell surface receptors , also known as transmembrane receptors, include ligand-gated ion channels , G protein-coupled receptors , and enzyme-linked hormone receptors . Intracellular receptors are those found inside
330-443: 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: As a drug approaches a receptor, the receptor alters the conformation of its binding site to produce drug—receptor complex. In some receptor systems (e.g. acetylcholine at
352-405: The cell, and include cytoplasmic receptors and nuclear receptors . A molecule that binds to a receptor is called a ligand and can be a protein, peptide (short protein), or another small molecule , such as a neurotransmitter , hormone , pharmaceutical drug, toxin, calcium ion or parts of the outside of a virus or microbe. An endogenously produced substance that binds to a particular receptor
374-411: The cell. 4 examples of intracellular LGIC are shown below: Many genetic disorders involve hereditary 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
396-403: The dynamic behavior of receptors have been used to gain understanding of their mechanisms of action. Ligand binding is an equilibrium process. Ligands bind to receptors and dissociate from them according to the law of mass action in the following equation, for a ligand L and receptor, R. The brackets around chemical species denote their concentrations. One measure of how well a molecule fits
418-414: The following major categories, among others: Membrane receptors may be isolated from cell membranes by complex extraction procedures using solvents , detergents , and/or affinity purification . The structures and actions of receptors may be studied by using biophysical methods such as X-ray crystallography , NMR , circular dichroism , and dual polarisation interferometry . Computer simulations of
440-577: The inhibition of the constitutive activity of the cannabinoid receptor. The GABA A receptor has constitutive activity and conducts some basal current in the absence of an agonist. This allows beta carboline to act as an inverse agonist and reduce the current below basal levels. 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). Early forms of
462-472: 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. Cells can increase ( upregulate ) or decrease ( downregulate ) the number of receptors to a given hormone or neurotransmitter to alter their sensitivity to different molecules. This
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#1733085469448484-597: The table below. The chief neurotransmitters are glutamate and GABA; other neurotransmitters are neuromodulatory . This list is by no means exhaustive. Enzyme linked receptors include Receptor tyrosine kinases (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: Receptors may be classed based on their mechanism or on their position in
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