Glutamate [NMDA] receptor subunit epsilon-2, also known as N-methyl D-aspartate receptor subtype 2B (NMDAR2B or NR2B), is a protein that in humans is encoded by the GRIN2B gene. [5]
Glutamate [NMDA] receptor subunit epsilon-2, also known as N-methyl D-aspartate receptor subtype 2B (NMDAR2B or NR2B), is a protein that in humans is encoded by the GRIN2B gene. [5]
N-methyl-D-aspartate (NMDA) receptors are a class of ionotropic glutamate receptors. The NMDA receptor channel has been shown to be involved in long-term potentiation, an activity-dependent increase in the efficiency of synaptic transmission thought to underlie certain kinds of memory and learning. NMDA receptor channels are heterotetramers composed of two molecules of the key receptor subunit NMDAR1 (GRIN1) and two drawn from one or more of the four NMDAR2 subunits: NMDAR2A (GRIN2A), NMDAR2B (GRIN2B), NMDAR2C (GRIN2C), and NMDAR2D (GRIN2D). The NR2 subunit acts as the agonist binding site for glutamate, one of the predominant excitatory neurotransmitter receptors in the mammalian brain. [6]
NR2B has been associated with age- and visual-experience-dependent plasticity in the neocortex of rats, where an increased NR2B/NR2A ratio correlates directly with the stronger excitatory LTP in young animals. This is thought to contribute to experience-dependent refinement of developing cortical circuits. [7]
Engineered to overexpress GRIN2B in their brains, mice and rats exhibit improved mental function. The "Doogie" mouse performed twice as well on one learning test. [8] [9]
GRIN2B has been shown to interact with:
The N-methyl-D-aspartatereceptor (also known as the NMDA receptor or NMDAR), is a glutamate receptor and predominantly Ca2+ ion channel found in neurons. The NMDA receptor is one of three types of ionotropic glutamate receptors, the other two being AMPA and kainate receptors. Depending on its subunit composition, its ligands are glutamate and glycine (or D-serine). However, the binding of the ligands is typically not sufficient to open the channel as it may be blocked by Mg2+ ions which are only removed when the neuron is sufficiently depolarized. Thus, the channel acts as a "coincidence detector" and only once both of these conditions are met, the channel opens and it allows positively charged ions (cations) to flow through the cell membrane. The NMDA receptor is thought to be very important for controlling synaptic plasticity and mediating learning and memory functions.
Dizocilpine (INN), also known as MK-801, is a pore blocker of the NMDA receptor, a glutamate receptor, discovered by a team at Merck in 1982. Glutamate is the brain's primary excitatory neurotransmitter. The channel is normally blocked with a magnesium ion and requires depolarization of the neuron to remove the magnesium and allow the glutamate to open the channel, causing an influx of calcium, which then leads to subsequent depolarization. Dizocilpine binds inside the ion channel of the receptor at several of PCP's binding sites thus preventing the flow of ions, including calcium (Ca2+), through the channel. Dizocilpine blocks NMDA receptors in a use- and voltage-dependent manner, since the channel must open for the drug to bind inside it. The drug acts as a potent anti-convulsant and probably has dissociative anesthetic properties, but it is not used clinically for this purpose because of the discovery of brain lesions, called Olney's lesions (see below), in laboratory rats. Dizocilpine is also associated with a number of negative side effects, including cognitive disruption and psychotic-spectrum reactions. It inhibits the induction of long term potentiation and has been found to impair the acquisition of difficult, but not easy, learning tasks in rats and primates. Because of these effects of dizocilpine, the NMDA receptor pore blocker ketamine is used instead as a dissociative anesthetic in human medical procedures. While ketamine may also trigger temporary psychosis in certain individuals, its short half-life and lower potency make it a much safer clinical option. However, dizocilpine is the most frequently used uncompetitive NMDA receptor antagonist in animal models to mimic psychosis for experimental purposes.
CNQX or cyanquixaline (6-cyano-7-nitroquinoxaline-2,3-dione) is a competitive AMPA/kainate receptor antagonist. Its chemical formula is C9H4N4O4. CNQX is often used in the retina to block the responses of OFF-bipolar cells for electrophysiology recordings.
Ligand-gated ion channels (LICs, LGIC), also commonly referred to as ionotropic receptors, are a group of transmembrane ion-channel proteins which open to allow ions such as Na+, K+, Ca2+, and/or Cl− to pass through the membrane in response to the binding of a chemical messenger (i.e. a ligand), such as a neurotransmitter.
The metabotropic glutamate receptors, or mGluRs, are a type of glutamate receptor that are active through an indirect metabotropic process. They are members of the group C family of G-protein-coupled receptors, or GPCRs. Like all glutamate receptors, mGluRs bind with glutamate, an amino acid that functions as an excitatory neurotransmitter.
Glutamate receptors are synaptic and non synaptic receptors located primarily on the membranes of neuronal and glial cells. Glutamate is abundant in the human body, but particularly in the nervous system and especially prominent in the human brain where it is the body's most prominent neurotransmitter, the brain's main excitatory neurotransmitter, and also the precursor for GABA, the brain's main inhibitory neurotransmitter. Glutamate receptors are responsible for the glutamate-mediated postsynaptic excitation of neural cells, and are important for neural communication, memory formation, learning, and regulation.
Ifenprodil is an inhibitor of the NMDA receptor, specifically of GluN1 and GluN2B subunits. Additionally, ifenprodil inhibits GIRK channels, and interacts with alpha1 adrenergic, serotonin, and sigma receptors.
PSD-95 also known as SAP-90 is a protein that in humans is encoded by the DLG4 gene.
Disks large homolog 3 (DLG3) also known as neuroendocrine-DLG or synapse-associated protein 102 (SAP-102) is a protein that in humans is encoded by the DLG3 gene. DLG3 is a member of the membrane-associated guanylate kinase (MAGUK) superfamily of proteins.
Glutamate [NMDA] receptor subunit epsilon-1 is a protein that in humans is encoded by the GRIN2A gene. With 1464 amino acids, the canonical GluN2A subunit isoform is large. GluN2A-short isoforms specific to primates can be produced by alternative splicing and contain 1281 amino acids.
Glutamate [NMDA] receptor subunit zeta-1 is a protein that in humans is encoded by the GRIN1 gene.
Glutamate [NMDA] receptor subunit 3A is a protein that in humans is encoded by the GRIN3A gene.
Glutamate [NMDA] receptor subunit epsilon-4 is a protein that in humans is encoded by the GRIN2D gene.
Glutamate [NMDA] receptor subunit epsilon-3 is a protein that in humans is encoded by the GRIN2C gene.
Glutamate [NMDA] receptor subunit 3B is a protein that in humans is encoded by the GRIN3B gene.
Disks large-associated protein 2 is a protein that in humans is encoded by the DLGAP2 gene.
Selfotel (CGS-19755) is a drug which acts as a competitive NMDA antagonist, directly competing with glutamate for binding to the receptor. Initial studies showed it to have anticonvulsant, anxiolytic, analgesic and neuroprotective effects, and it was originally researched for the treatment of stroke, but subsequent animal and human studies showed phencyclidine-like effects, as well as limited efficacy and evidence for possible neurotoxicity under some conditions, and so clinical development was ultimately discontinued.
Traxoprodil is a drug developed by Pfizer which acts as an NMDA antagonist, selective for the NR2B subunit. It has neuroprotective, analgesic, and anti-Parkinsonian effects in animal studies. Traxoprodil has been researched in humans as a potential treatment to lessen the damage to the brain after stroke, but results from clinical trials showed only modest benefit. The drug was found to cause EKG abnormalities and its clinical development was stopped. More recent animal studies have suggested traxoprodil may exhibit rapid-acting antidepressant effects similar to those of ketamine, although there is some evidence for similar psychoactive side effects and abuse potential at higher doses, which might limit clinical acceptance of traxoprodil for this application.
Conantokins are a small family of helical peptides that are derived from the venom of predatory marine snails of the genus Conus. Conantokins act as potent and specific antagonists of the N-methyl-D-aspartate receptor (NMDAR). They are the only naturally-derived peptides to do so. The subtypes of conantokins exhibit a surprising variability of selectivity across the NMDAR subunits, and are therefore uniquely useful in developing subunit-specific pharmacological probes.
GRIN disorders are a group of neurodevelopmental disorders that result from mutations in genes coding for subunits of an N-methyl-D-aspartate (NMDA) receptor, which leads to dysfunction of glutamate signaling. GRIN disorders are universally characterized by a varying degree of developmental delay and intellectual disability, as well as epileptic seizures. Other clinical features vary depending on the affected gene and may include muscular hypotonia, spasticity, and movement disorders. GRIN disorders are confirmed with genetic testing and managed symptomatically since there is currently no cure for the disorder.
This article incorporates text from the United States National Library of Medicine, which is in the public domain.