Summary: Neurotransmitter-gated ion-channel transmembrane region
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Ligand-gated ion channel Edit Wikipedia article
Neurotransmitter-gated ion-channel transmembrane region | |||||||||
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![]() Ligand-gated ion channel
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Identifiers | |||||||||
Symbol | Neur_chan_memb | ||||||||
Pfam | PF02932 | ||||||||
InterPro | IPR006029 | ||||||||
PROSITE | PDOC00209 | ||||||||
SCOP | 1cek | ||||||||
SUPERFAMILY | 1cek | ||||||||
TCDB | 1.A.9 | ||||||||
OPM superfamily | 14 | ||||||||
OPM protein | 2bg9 | ||||||||
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- Ion-channel-linked receptor
- Ions
- Ligand (such as acetylcholine)
Ligand-gated ion channels (LICs, LGIC), also commonly referred 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.[1][2][3]
When a presynaptic neuron is excited, it releases a neurotransmitter from vesicles into the synaptic cleft. The neurotransmitter then binds to receptors located on the postsynaptic neuron. If these receptors are ligand-gated ion channels, a resulting conformational change opens the ion channels, which leads to a flow of ions across the cell membrane. This, in turn, results in either a depolarization, for an excitatory receptor response, or a hyperpolarization, for an inhibitory response.
These proteins are typically composed of at least two different domains: a transmembrane domain which includes the ion pore, and an extracellular domain which includes the ligand binding location (an allosteric binding site). This modularity has enabled a 'divide and conquer' approach to finding the structure of the proteins (crystallising each domain separately). The function of such receptors located at synapses is to convert the chemical signal of presynaptically released neurotransmitter directly and very quickly into a postsynaptic electrical signal. Many LICs are additionally modulated by allosteric ligands, by channel blockers, ions, or the membrane potential. LICs are classified into three superfamilies which lack evolutionary relationship: cys-loop receptors, ionotropic glutamate receptors and ATP-gated channels.
Contents
Cys-loop receptors
The cys-loop receptors are named after a characteristic loop formed by a disulfide bond between two cysteine residues in the N terminal extracellular domain. They are part of a larger family of pentameric ligand-gated ion channels that usually lack this disulfide bond, hence the tentative name "Pro-loop receptors".[4][5] A binding site in the extracellular N-terminal ligand-binding domain gives them receptor specificity for (1) acetylcholine (AcCh), (2) serotonin, (3) glycine, (4) glutamate and (5) γ-aminobutyric acid (GABA) in vertebrates. The receptors are subdivided with respect to the type of ion that they conduct (anionic or cationic) and further into families defined by the endogenous ligand. They are usually pentameric with each subunit containing 4 transmembrane helices constituting the transmembrane domain, and a beta sheet sandwich type, extracellular, N terminal, ligand binding domain.[6] Some also contain an intracellular domain like shown in the image.
The prototypic ligand-gated ion channel is the nicotinic acetylcholine receptor. It consists of a pentamer of protein subunits (typically ααβγδ), with two binding sites for acetylcholine (one at the interface of each alpha subunit). When the acetylcholine binds it alters the receptor's configuration (twists the T2 helices which moves the leucine residues, which block the pore, out of the channel pathway) and causes the constriction in the pore of approximately 3 angstroms to widen to approximately 8 angstroms so that ions can pass through. This pore allows Na+ ions to flow down their electrochemical gradient into the cell. With a sufficient number of channels opening at once, the inward flow of positive charges carried by Na+ ions depolarizes the postsynaptic membrane sufficiently to initiate an action potential.
While single-cell organisms like bacteria would have little apparent need for the transmission of an action potential, a bacterial homologue to an LIC has been identified, hypothesized to act nonetheless as a chemoreceptor.[4] This prokaryotic nAChR variant is known as the GLIC receptor, after the species in which it was identified; Gloeobacter Ligand-gated Ion C channel.
Structure
Cys-loop receptors have structural elements that are well conserved, with a large extracellular domain (ECD) harboring an alpha-helix and 10 beta-strands. Following the ECD, four transmembrane segments (TMSs) are connected by intracellular and extracellular loop structures.[7] Except the TMS 3-4 loop, their lengths are only 7-14 residues. The TMS 3-4 loop forms the largest part of the intracellular domain (ICD) and exhibits the most variable region between all of these homologous receptors. The ICD is defined by the TMS 3-4 loop together with the TMS 1-2 loop preceding the ion channel pore.[7] Crystallization has revealed structures for some members of the family, but to allow crystallization, the intracellular loop was usually replaced by a short linker present in prokaryotic cys-loop receptors, so their structures as not known. Nevertheless, this intracellular loop appears to function in desensitization, modulation of channel physiology by pharmacological substances, and posttranslational modifications. Motifs important for trafficking are therein, and the ICD interacts with scaffold proteins enabling inhibitory synapse formation.[7]
Cationic cys-loop receptors
Type | Class | IUPHAR-recommended protein name [8] |
Gene | Previous names |
---|---|---|---|---|
Serotonin (5-HT) |
5-HT3 | 5-HT3A 5-HT3B 5-HT3C 5-HT3D 5-HT3E |
HTR3A HTR3B HTR3C HTR3D HTR3E |
5-HT3A 5-HT3B 5-HT3C 5-HT3D 5-HT3E |
Nicotinic acetylcholine (nAChR) |
alpha | α1 α2 α3 α4 α5 α6 α7 α9 α10 |
CHRNA1 CHRNA2 CHRNA3 CHRNA4 CHRNA5 CHRNA6 CHRNA7 CHRNA9 CHRNA10 |
ACHRA, ACHRD, CHRNA, CMS2A, FCCMS, SCCMS |
beta | β1 β2 β3 β4 |
CHRNB1 CHRNB2 CHRNB3 CHRNB4 |
CMS2A, SCCMS, ACHRB, CHRNB, CMS1D EFNL3, nAChRB2 |
|
gamma | γ | CHRNG | ACHRG | |
delta | δ | CHRND | ACHRD, CMS2A, FCCMS, SCCMS | |
epsilon | ε | CHRNE | ACHRE, CMS1D, CMS1E, CMS2A, FCCMS, SCCMS | |
Zinc-activated ion channel (ZAC) |
ZAC | ZACN | ZAC1, L2m LICZ, LICZ1 |
Anionic cys-loop receptors
Type | Class | IUPHAR-recommended protein name[8] |
Gene | Previous names |
---|---|---|---|---|
GABAA | alpha | α1 α2 α3 α4 α5 α6 |
GABRA1 GABRA2 GABRA3 GABRA4 GABRA5 GABRA6 |
EJM, ECA4 |
beta | β1 β2 β3 |
GABRB1 GABRB2 GABRB3 |
ECA5 |
|
gamma | γ1 γ2 γ3 |
GABRG1 GABRG2 GABRG3 |
CAE2, ECA2, GEFSP3 | |
delta | δ | GABRD | ||
epsilon | ε | GABRE | ||
pi | π | GABRP | ||
theta | θ | GABRQ | ||
rho | ρ1 ρ2 ρ3 |
GABRR1 GABRR2 GABRR3 |
GABAC[9] | |
Glycine (GlyR) |
alpha | α1 α2 α3 α4 |
GLRA1 GLRA2 GLRA3 GLRA4 |
STHE |
beta | β | GLRB |
Ionotropic glutamate receptors
The ionotropic glutamate receptors bind the neurotransmitter glutamate. They form tetramers with each subunit consisting of an extracellular amino terminal domain (ATD, which is involved tetramer assembly), an extracellular ligand binding domain (LBD, which binds glutamate), and a transmembrane domain (TMD, which forms the ion channel). The transmembrane domain of each subunit contains three transmembrane helices as well as a half membrane helix with a reentrant loop. The structure of the protein starts with the ATD at the N terminus followed by the first half of the LBD which is interrupted by helices 1,2 and 3 of the TMD before continuing with the final half of the LBD and then finishing with helix 4 of the TMD at the C terminus. This means there are three links between the TMD and the extracellular domains. Each subunit of the tetramer has a binding site for glutamate formed by the two LBD sections forming a clamshell like shape. Only two of these sites in the tetramer need to be occupied to open the ion channel. The pore is mainly formed by the half helix 2 in a way which resembles an inverted potassium channel.
Type | Class | IUPHAR-recommended protein name [8] |
Gene | Previous names |
---|---|---|---|---|
AMPA | GluA | GluA1 GluA2 GluA3 GluA4 |
GRIA1 GRIA2 GRIA3 GRIA4 |
GLUA1, GluR1, GluRA, GluR-A, GluR-K1, HBGR1 GLUA2, GluR2, GluRB, GluR-B, GluR-K2, HBGR2 GLUA3, GluR3, GluRC, GluR-C, GluR-K3 GLUA4, GluR4, GluRD, GluR-D |
Kainate | GluK | GluK1 GluK2 GluK3 GluK4 GluK5 |
GRIK1 GRIK2 GRIK3 GRIK4 GRIK5 |
GLUK5, GluR5, GluR-5, EAA3 GLUK6, GluR6, GluR-6, EAA4 GLUK7, GluR7, GluR-7, EAA5 GLUK1, KA1, KA-1, EAA1 GLUK2, KA2, KA-2, EAA2 |
NMDA | GluN | GluN1 NRL1A NRL1B |
GRIN1 GRINL1A GRINL1B |
GLUN1, NMDA-R1, NR1, GluRξ1 |
GluN2A GluN2B GluN2C GluN2D |
GRIN2A GRIN2B GRIN2C GRIN2D |
GLUN2A, NMDA-R2A, NR2A, GluRε1 GLUN2B, NMDA-R2B, NR2B, hNR3, GluRε2 GLUN2C, NMDA-R2C, NR2C, GluRε3 GLUN2D, NMDA-R2D, NR2D, GluRε4 |
||
GluN3A GluN3B |
GRIN3A GRIN3B |
GLUN3A, NMDA-R3A, NMDAR-L, chi-1 GLU3B, NMDA-R3B |
||
‘Orphan’ | (GluD) | GluD1 GluD2 |
GRID1 GRID2 |
GluRδ1 GluRδ2 |
AMPA receptor
The α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (also known as AMPA receptor, or quisqualate receptor) is a non-NMDA-type ionotropic transmembrane receptor for glutamate that mediates fast synaptic transmission in the central nervous system (CNS). Its name is derived from its ability to be activated by the artificial glutamate analog AMPA. The receptor was first named the "quisqualate receptor" by Watkins and colleagues after a naturally occurring agonist quisqualate and was only later given the label "AMPA receptor" after the selective agonist developed by Tage Honore and colleagues at the Royal Danish School of Pharmacy in Copenhagen.[10] AMPARs are found in many parts of the brain and are the most commonly found receptor in the nervous system. The AMPA receptor GluA2 (GluR2) tetramer was the first glutamate receptor ion channel to be crystallized.
Ligands:
- Agonists: Glutamate, AMPA, 5-Fluorowillardiine, Domoic acid, Quisqualic acid, etc.
- Antagonists: CNQX, Kynurenic acid, NBQX, Perampanel, Piracetam, etc.
- Positive allosteric modulators: Aniracetam, Cyclothiazide, CX-516, CX-614, etc.
- Negative allosteric modulators: Ethanol, Perampanel, Talampanel, GYKI-52,466, etc.
NMDA receptors
The N-methyl-D-aspartate receptor (NMDA receptor) – a type of ionotropic glutamate receptor – is a voltage-dependent ligand-gated ion channel that is gated by the simultaneous binding of glutamate and a co-agonist (i.e., either D-serine or glycine).[11] Studies show that the NMDA receptor is involved in regulating synaptic plasticity and memory.[12][13]
The name "NMDA receptor" is derived from the ligand N-methyl-D-aspartate (NMDA), which acts as a selective agonist at these receptors. When the NMDA receptor is activated by the binding of two co-agonists, the cation channel opens, allowing Na+ and Ca2+ to flow into the cell, in turn raising the cell's electric potential. Thus, the NMDA receptor is an excitatory receptor. At resting potentials, the binding of Mg2+ or Zn2+ at their extracellular binding sites on the receptor blocks ion flux through the NMDA receptor channel. "However, when neurons are depolarized, for example, by intense activation of colocalized postsynaptic AMPA receptors, the voltage-dependent block by Mg2+ is partially relieved, allowing ion influx through activated NMDA receptors. The resulting Ca2+ influx can trigger a variety of intracellular signaling cascades, which can ultimately change neuronal function through activation of various kinases and phosphatases".[14]
Ligands:
- Primary endogenous co-agonists: glutamate and either D-serine or glycine
- Other agonists : aminocyclopropanecarboxylic acid; D-cycloserine; L-aspartate; quinolinate, etc.
- Partial agonists : N-methyl-D-aspartic acid (NMDA); NRX-1074; 3,5-dibromo-L-phenylalanine,[15] etc.
- Antagonists: ketamine, PCP, dextropropoxyphene, ketobemidone, tramadol, kynurenic acid (endogenous), etc.
GABA receptors
GABA receptors are major inhibitory neurotransmitter expressed in the major interneurons in animal cortex.
GABAA receptor
GABAA receptors are ligand-gated ion channels. GABA (gamma-aminobutyric acid), the endogenous ligand for these receptors, is the major inhibitory neurotransmitter in the central nervous system. When activated, it mediates Cl– flow into the neuron, hyperpolarizing the neuron. GABAA receptors occur in all organisms that have a nervous system. Due to their wide distribution within the nervous system of mammals, they play a role in virtually all brain functions.[16]
Various ligands can bind specifically to GABAA receptors, either activating or inhibiting the Cl– channel.
Ligands:
- Agonists: GABA, muscimol, progabide, gaboxadol
- Antagonists: bicuculine, gabazine
- Partial agonist: piperidine-4-sulfonic acid
5-HT receptors
5-HT receptors, also known as the serotonin receptors, or 5-hydroxytryptamine receptors, are ligand-gated ion channels. They activate an intracellular second messenger cascade to produce an excitatory/inhibitory response. They are found in mammals, both central nervous system (CNS) and peripheral nervous system (PNS), as well as other animals.[17] Its natural ligand is Serotonin, and it modulates the release of multiple neurotransmitters, such as dopamine, epinephrine/norepinephrine, glutamate, and GABA.
Research confirm that the 5-HT receptors are involved in many neurological processes, such as anxiety, depression, sleep, cognition, memory, and so on. Thus there are several drugs targeting the 5-HT system, including some antidepressants, antipsychotics, anxiolytics, antiemetics, and antimigraine drugs, as well as the psychedelic drugs and empathogens.[18][19][20]
ATP-gated channels
ATP-gated channels open in response to binding the nucleotide ATP. They form trimers with two transmembrane helices per subunit and both the C and N termini on the intracellular side.
Type | Class | IUPHAR-recommended protein name [8] |
Gene | Previous names |
---|---|---|---|---|
P2X | N/A | P2X1 P2X2 P2X3 P2X4 P2X5 P2X6 P2X7 |
P2RX1 P2RX2 P2RX3 P2RX4 P2RX5 P2RX6 P2RX7 |
P2X1 P2X2 P2X3 P2X4 P2X5 P2X6 P2X7 |
PIP2-gated channels
Phosphatidylinositol 4,5-bisphosphate (PIP2) binds to and directly activates inwardly rectifying potassium channels (Kir).[21] PIP2 is a cell membrane lipid, and its role in gating ion channels represents a novel role for the molecule.[22][23]
Indirect modulation
In contrast to ligand-gated ion channels, there are also receptor systems in which the receptor and the ion channel are separate proteins in the cell membrane, instead of a single molecule. In this case, ion channels are indirectly modulated by activation of the receptor, instead of being gated directly.
G-protein-linked receptors
Also called G protein-coupled receptor, seven-transmembrane domain receptor, 7 TM receptor, constitute a large protein family of receptors that sense molecules outside the cell and activate inside signal transduction pathways and, ultimately, cellular responses. They pass through the cell membrane 7 times. G-protein-Linked receptors are a huge family that have hundreds of members identified. Ion-channel-linked receptors (e.g. GABAB, NMDA, etc.) are only a part of them.
Table 1. Three major families of Trimeric G Proteins[24]
FAMILY | SOME FAMILY MEMBERS | ACTION MEDIATED BY | FUNCTIONS |
---|---|---|---|
I | GS | α | Activate adenylyl cyclase activates Ca2+ channels |
Golf | α | Activates adenylyl cyclase in olfactory sensory neurons | |
II | Gi | α | Inhibits adenylyl cyclase |
βɣ | Activates K+ channels | ||
G0 | βɣ | Activates K+ channels; inactivate Ca2+ channels | |
α and βɣ | Activates phospholipase C-β | ||
Gt (transducin) | α | Activate cyclic GMP phosphodiesterase in vertebrate rod photoreceptors | |
III | Gq | α | Activates phospholipase C-β |
GABAB receptor
GABAB receptors are metabotropic transmembrane receptors for gamma-aminobutyric acid. They are linked via G-proteins to K+ channels, when active, they create hyperpolarized effect and lower the potential inside the cell.[25]
Ligands:
- Agonists: GABA, Baclofen, gamma-Hydroxybutyrate, Phenibut etc.
- Positive Allosteric Modulators: CGP-7930,[26] Fendiline, BSPP, etc.
- Antagonists:2-OH-saclofen, Saclofen, SCH-50911
Gα signaling
The cyclic-adenosine monophosphate (cAMP)-generating enzyme adenylate cyclase is the effector of both the Gαs and Gαi/o pathways. Ten different AC gene products in mammals, each with subtle differences in tissue distribution and/or function, all catalyze the conversion of cytosolic adenosine triphosphate (ATP) to cAMP, and all are directly stimulated by G-proteins of the Gαs class. Interaction with Gα subunits of the Gαi/o type, on the contrary, inhibits AC from generating cAMP. Thus, a GPCR coupled to Gαs counteracts the actions of a GPCR coupled to Gαi/o, and vice versa. The level of cytosolic cAMP may then determine the activity of various ion channels as well as members of the ser/thr-specific protein kinase A (PKA) family. As a result, cAMP is considered a second messenger and PKA a secondary effector.
The effector of the Gαq/11 pathway is phospholipase C-β (PLCβ), which catalyzes the cleavage of membrane-bound phosphatidylinositol 4,5-biphosphate (PIP2) into the second messengers inositol (1,4,5) trisphosphate (IP3) and diacylglycerol (DAG). IP3 acts on IP3 receptors found in the membrane of the endoplasmic reticulum (ER) to elicit Ca2+ release from the ER, DAG diffuses along the plasma membrane where it may activate any membrane localized forms of a second ser/thr kinase called protein kinase C (PKC). Since many isoforms of PKC are also activated by increases in intracellular Ca2+, both these pathways can also converge on each other to signal through the same secondary effector. Elevated intracellular Ca2+ also binds and allosterically activates proteins called calmodulins, which in turn go on to bind and allosterically activate enzymes such as Ca2+/calmodulin-dependent kinases (CAMKs).
The effectors of the Gα12/13 pathway are three RhoGEFs (p115-RhoGEF, PDZ-RhoGEF, and LARG), which, when bound to Gα12/13 allosterically activate the cytosolic small GTPase, Rho. Once bound to GTP, Rho can then go on to activate various proteins responsible for cytoskeleton regulation such as Rho-kinase (ROCK). Most GPCRs that couple to Gα12/13 also couple to other sub-classes, often Gαq/11.
Gβγ signaling
The above descriptions ignore the effects of Gβγ–signalling, which can also be important, in particular in the case of activated Gαi/o-coupled GPCRs. The primary effectors of Gβγ are various ion channels, such as G-protein-regulated inwardly rectifying K+ channels (GIRKs), P/Q- and N-type voltage-gated Ca2+ channels, as well as some isoforms of AC and PLC, along with some phosphoinositide-3-kinase (PI3K) isoforms.
Clinical relevance
Ligand-gated ion channels are likely to be the major site at which anaesthetic agents and ethanol have their effects, although unequivocal evidence of this is yet to be established.[27][28] In particular, the GABA and NMDA receptors are affected by anaesthetic agents at concentrations similar to those used in clinical anaesthesia.[29]
By understanding the mechanism and exploring the chemical/biological/physical component that could function on those receptors, more and more clinical applications are proven by preliminary experiments or FDA.
- Addiction treatment:
A series recent study shows that GABA receptors are involved with addiction-related behaviors, such as cocaine,[30] heroin, alcohol,[31] etc. Understanding the mechanism of receptors helped scientist develop pharmaceutical tools to treat addictions by modifying the receptors' activity.[32][33]
Memantine is approved by the U.S. F.D.A and the European Medicines Agency for the treatment of moderate-to-severe Alzheimer's disease,[34] and has now received a limited recommendation by the UK's National Institute for Health and Care Excellence for patients who fail other treatment options.[35]
- Antidepressant treatment
Agomelatine, is a type of drug that acts on a dual melatonergic-serotonergic pathway, which have shown its efficacy in the treatment of anxious depression during clinical trails,[36][37] study also suggests the efficacy in the treatment of atypical and melancholic depression.[38]
See also
- Receptor (biochemistry)
- Action potential
- Voltage-dependent calcium channel
- Calcium-activated potassium channel
- Cyclic nucleotide-gated ion channel
- Acid-sensing ion channel
- Ryanodine receptor
- Inositol trisphosphate receptor
References
- ^ "Gene Family: Ligand gated ion channels". HUGO Gene Nomenclature Committee.
- ^ "ligand-gated channel" at Dorland's Medical Dictionary
- ^ Purves, Dale, George J. Augustine, David Fitzpatrick, William C. Hall, Anthony-Samuel LaMantia, James O. McNamara, and Leonard E. White (2008). Neuroscience. 4th ed. Sinauer Associates. pp. 156–7. ISBN 978-0-87893-697-7.
- ^ a b Tasneem A, Iyer L, Jakobsson E, Aravind L (2004). "Identification of the prokaryotic ligand-gated ion channels and their implications for the mechanisms and origins of animal Cys-loop ion channels". Genome Biology. 6 (1): R4. doi:10.1186/gb-2004-6-1-r4. PMC 549065
. PMID 15642096.
- ^ Jaiteh M, Taly A, Hénin J (2016). "Evolution of Pentameric Ligand-Gated Ion Channels: Pro-Loop Receptors". PLoS One. 11 (3): e0151934. doi:10.1371/journal.pone.0151934. PMC 4795631
. PMID 26986966.
- ^ Cascio M (2004). "Structure and function of the glycine receptor and related nicotinicoid receptors". J. Biol. Chem. 279 (19): 19383–6. doi:10.1074/jbc.R300035200. PMID 15023997.
- ^ a b c Langlhofer, Georg; Villmann, Carmen (2016-01-01). "The Intracellular Loop of the Glycine Receptor: It's not all about the Size". Frontiers in Molecular Neuroscience. 9: 41. doi:10.3389/fnmol.2016.00041. ISSN 1662-5099. PMC 4891346
. PMID 27330534.
- ^ a b c d Collingridge GL, Olsen RW, Peters J, Spedding M (January 2009). "A nomenclature for ligand-gated ion channels". Neuropharmacology. 56 (1): 2–5. doi:10.1016/j.neuropharm.2008.06.063. PMC 2847504
. PMID 18655795.
- ^ Olsen RW, Sieghart W (September 2008). "International Union of Pharmacology. LXX. Subtypes of γ-Aminobutyric AcidA Receptors: Classification on the Basis of Subunit Composition, Pharmacology, and Function. Update". Pharmacol. Rev. 60 (3): 243–60. doi:10.1124/pr.108.00505. PMC 2847512
. PMID 18790874.
- ^ Honore T, Lauridsen J, Krogsgaard-Larsen P (1982). "The binding of [3H]AMPA, a structural analogue of glutamic acid, to rat brain membranes". Journal of Neurochemistry. 38 (1): 173–178. doi:10.1111/j.1471-4159.1982.tb10868.x. PMID 6125564.
- ^ Malenka RC, Nestler EJ, Hyman SE (2009). "Chapter 5: Excitatory and Inhibitory Amino Acids". In Sydor A, Brown RY. Molecular Neuropharmacology: A Foundation for Clinical Neuroscience (2nd ed.). New York, USA: McGraw-Hill Medical. pp. 124–125. ISBN 9780071481274.
At membrane potentials more negative than approximately −50 mV, the Mg2+ in the extracellular fluid of the brain virtually abolishes ion flux through NMDA receptor channels, even in the presence of glutamate. ... The NMDA receptor is unique among all neurotransmitter receptors in that its activation requires the simultaneous binding of two different agonists. In addition to the binding of glutamate at the conventional agonist-binding site, the binding of glycine appears to be required for receptor activation. Because neither of these agonists alone can open this ion channel, glutamate and glycine are referred to as coagonists of the NMDA receptor. The physiologic significance of the glycine binding site is unclear because the normal extracellular concentration of glycine is believed to be saturating. However, recent evidence suggests that D-serine may be the endogenous agonist for this site.
- ^ Li, F; Tsien, JZ (2009). "Memory and the NMDA receptors". N. Engl. J. Med. 361 (3): 302–3. doi:10.1056/NEJMcibr0902052. PMC 3703758
. PMID 19605837.
- ^ Cao, X; Cui, Z; Feng, R; et al. (March 2007). "Maintenance of superior learning and memory function in NR2B transgenic mice during ageing". European Journal of Neuroscience. 25: 1815–22. doi:10.1111/j.1460-9568.2007.05431.x. PMID 17432968.
- ^ Dingledine, R; Borges, K; Bowie, D; Traynelis, SF (1999). "The glutamate receptor ion channels". Pharmacol. Rev. 51 (1): 7–61. PMID 10049997.
- ^ Yarotskyy, V; Glushakov, AV; Sumners, C; Gravenstein, N; Dennis, DM; Seubert, CN; Martynyuk, AE (2005). "Differential modulation of glutamatergic transmission by 3,5-dibromo-L-phenylalanine". Mol. Pharmacol. 67 (5): 1648–54. doi:10.1124/mol.104.005983. PMID 15687225.
- ^ Wu, Connie; Sun, Dandan (April 2015). "GABA receptors in brain development, function, and injury". Metabolic brain disease. 30 (2): 367–379. doi:10.1007/s11011-014-9560-1. ISSN 0885-7490. PMC 4231020
. PMID 24820774.
- ^ Qi YX, Xia RY, Wu YS, Stanley D, Huang J, Ye GY (2014). "Larvae of the small white butterfly, Pieris rapae, express a novel serotonin receptor". J. Neurochem. 131: 767–77. doi:10.1111/jnc.12940. PMID 25187179.
- ^ Roth, BL; Driscol, J (12 January 2011). "PDSP Ki Database". Psychoactive Drug Screening Program (PDSP). University of North Carolina at Chapel Hill and the United States National Institute of Mental Health. Retrieved 17 December 2013.
- ^ Gonzalez, R; Chávez-Pascacio, K; Meneses, A (2013). "Role of 5-HT5A receptors in the consolidation of memory". Behavioural Brain Research. 252: 246–251. doi:10.1016/j.bbr.2013.05.051. PMID 23735322.
- ^ Sawin, ER; Ranganathan, R; Horvitz, HR; Ranganathan; Horvitz (2000). "C. elegans locomotory rate is modulated by the environment through a dopaminergic pathway and by experience through a serotonergic pathway". Neuron. 26 (3): 619–31. doi:10.1016/s0896-6273(00)81199-x. PMID 10896158.
- ^ Hansen SB, Tao X, MacKinnon R (September 2011). "Structural basis of PIP2 activation of the classical inward rectifier K+ channel Kir2.2". Nature. 477 (7365): 495–8. Bibcode:2011Natur.477..495H. doi:10.1038/nature10370. PMC 3324908
. PMID 21874019.
- ^ Hansen, SB (May 2015). "Lipid agonism: The PIP2 paradigm of ligand-gated ion channels". Biochimica et Biophysica Acta. 1851 (5): 620–8. doi:10.1016/j.bbalip.2015.01.011. PMID 25633344.
- ^ Gao, Y; Cao, E; Julius, D; Cheng, Y (16 June 2016). "TRPV1 structures in nanodiscs reveal mechanisms of ligand and lipid action". Nature. 534 (7607): 347–51. doi:10.1038/nature17964. PMID 27281200.
- ^ Lodish, Harvey. Molecular cell biology. Macmillan, 2008.
- ^ Chen, K; Li, HZ; Ye, N; Zhang, J; Wang, JJ (2005). "Role of GABAB receptors in GABA and baclofen-induced inhibition of adult rat cerebellar interpositus nucleus neurons in vitro". Brain Res Bull. 67 (4): 310–8. doi:10.1016/j.brainresbull.2005.07.004. PMID 16182939.
- ^ Urwyler, S; Mosbacher, J; Lingenhoehl, K; Heid, J; Hofstetter, K; Froestl, W; Bettler, B; Kaupmann, K (2001). "Positive allosteric modulation of native and recombinant gamma-aminobutyric acid(B) receptors by 2,6-Di-tert-butyl-4-(3-hydroxy-2,2-dimethyl-propyl)-phenol (CGP7930) and its aldehyde analog CGP13501". Mol. Pharmacol. 60 (5): 963–71. PMID 11641424.
- ^ Krasowski MD, Harrison NL (1999). "General anaesthetic actions on ligand-gated ion channels". Cell. Mol. Life Sci. 55 (10): 1278–303. doi:10.1007/s000180050371. PMC 2854026
. PMID 10487207.
- ^ Dilger JP (2002). "The effects of general anaesthetics on ligand-gated ion channels". Br J Anaesth. 89 (1): 41–51. doi:10.1093/bja/aef161. PMID 12173240.
- ^ Harris RA, Mihic SJ, Dildy-Mayfield JE, Machu TK (1995). "Actions of anesthetics on ligand-gated ion channels: role of receptor subunit composition" (abstract). FASEB J. 9 (14): 1454–62. PMID 7589987.
- ^ Goeders, N. E.; McNulty, M. A.; Mirkis, S.; McAllister, K. H. (1989). "Chlordiazepoxide alters intravenous cocaine self-administration in rats". Pharmacology Biochemistry and Behavior. 33: 859–866. doi:10.1016/0091-3057(89)90483-8.
- ^ Colombo, Giancarlo; et al. (2004). "Role of GABAB receptor in alcohol dependence: reducing effect of baclofen on alcohol intake and alcohol motivational properties in rats and amelioration of alcohol withdrawal syndrome and alcohol craving in human alcoholics". Neurotoxicity research. 6 (5): 403–414. doi:10.1007/BF03033315.
- ^ Brebner, Karen, Anna Rose Childress, and David CS Roberts. "A potential role for GABAB agonists in the treatment of psychostimulant addiction." Alcohol and Alcoholism 37.5 (2002): 478-484. alcalc.oxfordjournals.org/content/37/5/478.short
- ^ Young, Kimberly A.; et al. (2014). "Baclofen, a GABA B Agonist, reduces risk-taking and reveals the relationship between brain responses to drug cues and risk-taking in cocaine-addicted patients". Drug & Alcohol Dependence. 140: e247. doi:10.1016/j.drugalcdep.2014.02.684.
- ^ Mount C, Downton C (July 2006). "Alzheimer disease: progress or profit?". Nat. Med. 12 (7): 780–4. doi:10.1038/nm0706-780. PMID 16829947.
- ^ NICE technology appraisal January 18, 2011 Azheimer's disease - donepezil, galantamine, rivastigmine and memantine (review): final appraisal determination
- ^ Heun, R; Coral, RM; Ahokas, A; Nicolini, H; Teixeira, JM; Dehelean, P (2013). "1643 – Efficacy of agomelatine in more anxious elderly depressed patients. A randomized, double-blind study vs placebo". European Psychiatry. 28 (Suppl 1): 1. doi:10.1016/S0924-9338(13)76634-3.
- ^ Brunton, L; Chabner, B; Knollman, B (2010). Goodman and Gilman's The Pharmacological Basis of Therapeutics (12th ed.). New York: McGraw-Hill Professional. ISBN 978-0-07-162442-8.
- ^ Avedisova, A; Marachev, M (2013). "2639 – The effectiveness of agomelatine (valdoxan) in the treatment of atypical depression". European Psychiatry. 28 (Suppl 1): 1. doi:10.1016/S0924-9338(13)77272-9.
External links
- Ligand-Gated Ion Channel database at European Bioinformatics Institute. Verified availability April 11, 2007.
- "Revised Recommendations for Nomenclature of Ligand-Gated Ion Channels". IUPHAR Database of Receptors and Ion Channels. International Union of Basic and Clinical Pharmacology.
- http://www.esf.edu/efb/course/EFB325/lectures/29HormoneSignals.htm
- http://www.genenames.org/
As of this edit, this article uses content from "1.A.9 The Neurotransmitter Receptor, Cys loop, Ligand-gated Ion Channel (LIC) Family", which is licensed in a way that permits reuse under the Creative Commons Attribution-ShareAlike 3.0 Unported License, but not under the GFDL. All relevant terms must be followed.
This page is based on a Wikipedia article. The text is available under the Creative Commons Attribution/Share-Alike License.
This tab holds the annotation information that is stored in the Pfam database. As we move to using Wikipedia as our main source of annotation, the contents of this tab will be gradually replaced by the Wikipedia tab.
Neurotransmitter-gated ion-channel transmembrane region Provide feedback
This family includes the four transmembrane helices that form the ion channel.
Literature references
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Nury H, Bocquet N, Le Poupon C, Raynal B, Haouz A, Corringer PJ, Delarue M;, J Mol Biol. 2009; [Epub ahead of print]: Crystal Structure of the Extracellular Domain of a Bacterial Ligand-Gated Ion Channel. PUBMED:19917292 EPMC:19917292
Internal database links
SCOOP: | CytochromB561_N DUF1510 |
External database links
PRINTS: | PR00252 PR00253 PR00254 |
PROSITE: | PDOC00209 |
SCOP: | 1cek |
Transporter classification: | 1.A.9 |
This tab holds annotation information from the InterPro database.
InterPro entry IPR006029
Neurotransmitter ligand-gated ion channels are transmembrane receptor-ion channel complexes that open transiently upon binding of specific ligands, allowing rapid transmission of signals at chemical synapses [PUBMED:1721053, PUBMED:1846404]. Five of these ion channel receptor families have been shown to form a sequence-related superfamily:
- Nicotinic acetylcholine receptor (AchR), an excitatory cation channel in vertebrates and invertebrates; in vertebrate motor endplates it is composed of alpha, beta, gamma and delta/epsilon subunits; in neurons it is composed of alpha and non-alpha (or beta) subunits [PUBMED:18446614].
- Glycine receptor, an inhibitory chloride ion channel composed of alpha and beta subunits [PUBMED:15383648].
- Gamma-aminobutyric acid (GABA) receptor, an inhibitory chloride ion channel; at least four types of subunits (alpha, beta, gamma and delta) are known [PUBMED:18760291].
- Serotonin 5HT3 receptor, of which there are seven major types (5HT3-5HT7) [PUBMED:10026168].
- Glutamate receptor, an excitatory cation channel of which at least three types have been described (kainate, N-methyl-D-aspartate (NMDA) and quisqualate) [PUBMED:15165736].
These receptors possess a pentameric structure (made up of varying subunits), surrounding a central pore. All known sequences of subunits from neurotransmitter-gated ion-channels are structurally related. They are composed of a large extracellular glycosylated N-terminal ligand-binding domain, followed by three hydrophobic transmembrane regions which form the ionic channel, followed by an intracellular region of variable length. A fourth hydrophobic region is found at the C-terminal of the sequence [PUBMED:1721053, PUBMED:1846404].
This domain represents four transmembrane helices of a variety of neurotransmitter-gated ion-channels.
Gene Ontology
The mapping between Pfam and Gene Ontology is provided by InterPro. If you use this data please cite InterPro.
Cellular component | membrane (GO:0016020) |
Biological process | ion transport (GO:0006811) |
Domain organisation
Below is a listing of the unique domain organisations or architectures in which this domain is found. More...
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Alignments
We store a range of different sequence alignments for families. As well as the seed alignment from which the family is built, we provide the full alignment, generated by searching the sequence database (reference proteomes) using the family HMM. We also generate alignments using four representative proteomes (RP) sets, the UniProtKB sequence database, the NCBI sequence database, and our metagenomics sequence database. More...
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We make a range of alignments for each Pfam-A family. You can see a description of each above. You can view these alignments in various ways but please note that some types of alignment are never generated while others may not be available for all families, most commonly because the alignments are too large to handle.
Seed (50) |
Full (11034) |
Representative proteomes | UniProt (16274) |
NCBI (27750) |
Meta (38) |
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RP15 (3154) |
RP35 (4999) |
RP55 (8022) |
RP75 (9565) |
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PP/heatmap | 1 |
1Cannot generate PP/Heatmap alignments for seeds; no PP data available
Key:
available,
not generated,
— not available.
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We make all of our alignments available in Stockholm format. You can download them here as raw, plain text files or as gzip-compressed files.
Seed (50) |
Full (11034) |
Representative proteomes | UniProt (16274) |
NCBI (27750) |
Meta (38) |
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RP15 (3154) |
RP35 (4999) |
RP55 (8022) |
RP75 (9565) |
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Raw Stockholm | |||||||||
Gzipped |
You can also download a FASTA format file containing the full-length sequences for all sequences in the full alignment.
HMM logo
HMM logos is one way of visualising profile HMMs. Logos provide a quick overview of the properties of an HMM in a graphical form. You can see a more detailed description of HMM logos and find out how you can interpret them here. More...
Trees
This page displays the phylogenetic tree for this family's seed alignment. We use FastTree to calculate neighbour join trees with a local bootstrap based on 100 resamples (shown next to the tree nodes). FastTree calculates approximately-maximum-likelihood phylogenetic trees from our seed alignment.
Note: You can also download the data file for the tree.
Curation and family details
This section shows the detailed information about the Pfam family. You can see the definitions of many of the terms in this section in the glossary and a fuller explanation of the scoring system that we use in the scores section of the help pages.
Curation
Seed source: | Prosite |
Previous IDs: | none |
Type: | Family |
Author: | Bateman A, Sonnhammer ELL |
Number in seed: | 50 |
Number in full: | 11034 |
Average length of the domain: | 168.20 aa |
Average identity of full alignment: | 22 % |
Average coverage of the sequence by the domain: | 39.20 % |
HMM information
HMM build commands: |
build method: hmmbuild -o /dev/null HMM SEED
search method: hmmsearch -Z 26740544 -E 1000 --cpu 4 HMM pfamseq
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Model details: |
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Model length: | 238 | ||||||||||||
Family (HMM) version: | 15 | ||||||||||||
Download: | download the raw HMM for this family |
Species distribution
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Selections
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This visualisation provides a simple graphical representation of the distribution of this family across species. You can find the original interactive tree in the adjacent tab. More...
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Interactions
There are 7 interactions for this family. More...
MoeA_C Neur_chan_LBD MoeA_N Adap_comp_sub Neur_chan_LBD Neur_chan_memb MoCF_biosynthStructures
For those sequences which have a structure in the Protein DataBank, we use the mapping between UniProt, PDB and Pfam coordinate systems from the PDBe group, to allow us to map Pfam domains onto UniProt sequences and three-dimensional protein structures. The table below shows the structures on which the Neur_chan_memb domain has been found. There are 202 instances of this domain found in the PDB. Note that there may be multiple copies of the domain in a single PDB structure, since many structures contain multiple copies of the same protein sequence.
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