Metabotropic receptor
Ametabotropic receptor,also referred to by the broader termG-protein-coupled receptor,[1]is a type of membrane receptor that initiates a number ofmetabolic stepsto modulate cell activity. Thenervous systemutilizes two types ofreceptors:metabotropicandionotropicreceptors. While ionotropic receptors form anion channel pore,metabotropic receptors are indirectly linked with ion channels through signal transduction mechanisms, such asG proteins.
Both receptor types are activated by specificchemical ligands.When an ionotropic receptor is activated, it opens a channel that allows ions such asNa+,K+,orCl−to flow. In contrast, when a metabotropic receptor is activated, a series of intracellular events are triggered that can also result in ion channels opening or other intracellular events, but involve a range ofsecond messengerchemicals.[2]
Mechanism
[edit]Chemical messengersbind to metabotropic receptors to initiate a diversity of effects caused by biochemicalsignaling cascades.G protein-coupled receptors are all metabotropic receptors. When a ligand binds to a G protein-coupled receptor, aguanine nucleotide-binding protein,orG protein,activates a second messenger cascade which can altergene transcription,regulate other proteins in the cell, releaseintracellular Ca2+,or directly affect ion channels on the membrane.[3][4]These receptors can remain open from seconds to minutes and are associated with long-lasting effects, such as modifying synaptic strength and modulating short- and long-term synaptic plasticity.[5]
Metabotropic receptors have a diversity of ligands, including but not limited to: small molecule transmitters,monoamines,peptides,hormones,and even gases.[5][6][7]In comparison to fast-actingneurotransmitters,these ligands are not taken up again or degraded quickly. They can also enter thecirculatory systemto globalize a signal.[3]Most metabotropic ligands have unique receptors. Some examples include:metabotropic glutamate receptors,muscarinic acetylcholine receptors,GABABreceptors.[2][8]
Structure
[edit]The G protein-coupled receptors have seven hydrophobic transmembrane domains. Most of them are monomeric proteins, although GABABreceptors require heterodimerization to function properly. The protein'sN terminusis located on the extracellular side of the membrane and its C terminus is on the intracellular side.[2]
The 7 transmembrane spanning domains, with an external amino terminus, are often claimed as being Alpha helix shaped, and the polypeptide chain is said to be composed of around 450–550 amino acids.
References
[edit]- ^Purves, Dale, ed. (2018).Neuroscience, 6th ed.Sunderland, Mass: Sinauer Associates. p. 103.
- ^abcWilliams, S. J.; Purves, Dale (2001).Neuroscience.Sunderland, Mass: Sinauer Associates.ISBN0-87893-742-0.
- ^ab"Principles of Neural Design",The MIT Press, 2015,doi:10.7551/mitpress/9395.003.0019,ISBN978-0-262-32731-2,retrievedOctober 18,2020
{{citation}}:Missing or empty|title=(help) - ^Ferguson, Duncan C. (January 1, 2018), Wallig, Matthew A.; Haschek, Wanda M.; Rousseaux, Colin G.; Bolon, Brad (eds.),"Chapter 4 - Principles of Pharmacodynamics and Toxicodynamics",Fundamentals of Toxicologic Pathology (Third Edition),Academic Press, pp. 47–58,doi:10.1016/b978-0-12-809841-7.00004-6,ISBN978-0-12-809841-7,retrievedOctober 30,2020
- ^abNadim, Farzan; Bucher, Dirk (December 2014)."Neuromodulation of Neurons and Synapses".Current Opinion in Neurobiology.29:48–56.doi:10.1016/j.conb.2014.05.003.ISSN0959-4388.PMC4252488.PMID24907657.
- ^Burrows, Malcolm (1996). "Neurotransmitters, neuromodulators and neurohormones".The Neurobiology of an Insect Brain.Oxford Scholarship.doi:10.1093/acprof:oso/9780198523444.003.0005.ISBN9780198523444.
- ^Marder, Eve (October 4, 2012)."Neuromodulation of Neuronal Circuits: Back to the Future".Neuron.76(1): 1–11.doi:10.1016/j.neuron.2012.09.010.ISSN0896-6273.PMC3482119.PMID23040802.
- ^Hoehn K, Marieb EN (2007)."Fundamentals of the nervous system and nervous tissue".Human Anatomy & Physiology.San Francisco: Pearson Benjamin Cummings.ISBN978-0-8053-5910-7.
Further reading
[edit]- Zimmerberg, B. 2002. Dopamine receptors: A representative family of metabotropic receptors. Multimedia Neuroscience Education Project[1]