Ligand-gated ion channel
From Wikipedia, the free encyclopedia
Neurotransmitter-gated ion-channel transmembrane region | ||
---|---|---|
Identifiers | ||
Symbol | Neur_chan_memb | |
Pfam | PF02932 | |
InterPro | IPR006029 | |
PROSITE | PDOC00209 | |
SCOP | 1cek | |
TCDB | 1.A.9 | |
OPM family | 14 | |
OPM protein | 2bg9 | |
Available PDB structures:
1oedE:242-483 2bg9E:242-389 1dxzA:260-291 3mra :301-325 1a11 :276-298 1cekA:276-298 1eq8E:276-298 1motA:277-304 1vryA:281-337 |
Neurotransmitter-gated ion-channel ligand binding domain | ||
---|---|---|
Identifiers | ||
Symbol | Neur_chan_LBD | |
Pfam | PF02931 | |
InterPro | IPR006202 | |
SCOP | 1lxg | |
Available PDB structures:
1ux2F:34-142 1uw6D:34-142 1i9bE:34-142 1uv6J:34-142 1yi5A:34-142 2bysD:23-226 2byrI:23-226 2byqA:23-226 2br7D:23-226 2bypC:23-225 2bynA:23-226 2bg9B:28-241 1lk1G:28-241 1olkE:28-241 1ol8B:26-230 1ol3A:26-230 1ol4B:26-230 1kl8B:201-219 1kc4B:201-219 1ol9A:26-230 1y5tB:230-235 1l4wB:206-226 1ljzB:206-226 1idgB:205-222 1tos :91-99 1lxgB:205-222 1lxhB:205-222 1idhB:205-222 1tor :91-100 1oleA:39-245 1olfA:29-235 1oljC:29-235 |
The Ligand-gated ion channels, also referred to as LGICs, or ionotropic receptors, are a group of intrinsic transmembrane ion channels that are opened or closed in response to binding of a chemical messenger, as opposed to voltage-gated ion channels or stretch-activated ion channels.[1]
Contents |
[edit] Regulation
The ion channel is regulated by a ligand and is usually very selective to one or more ions like Na+, K+, Ca2+, or Cl-. Such receptors located at synapses convert the chemical signal of presynaptically released neurotransmitter directly and very quickly into a postsynaptic electrical signal.
Many LGICs are additionally modulated by allosteric ligands, by channel blockers, ions, or the membrane potential.
[edit] Structure
Each subunit of the pentameric channels consist of the extracellular ligand-binding domain and a transmembrane domain. Each transmembrane domain in the pentamer includes four transmembrane helixes.[2]
[edit] Example: nicotinic acetylcholine receptor
The prototypic ligand-gated ion channel is the nicotinic acetylcholine receptor. It consists of a pentamer of protein subunits, with two binding sites for acetylcholine, which, when bound, alter the receptor's configuration and cause an internal pore to open. This pore, permeable to Na+, allows Na+ ions to flow down their electrochemical gradient into the cell. With a sufficient number of channels opening at once, the intracellular Na+ concentration rises to the point at which the positive charge within the cell is enough to depolarize the membrane, and an action potential is initiated.
[edit] Classification and examples
Many important ion channels are ligand-gated, and they show a great degree of homology at the genetic level. The Ligand-gated ion channels are classified into three superfamilies:
[edit] The Cys-loop receptors
- anionic
- cationic
- 5-HT3 serotonin receptor
- nicotinic acetylcholine receptor (nAChR)
- nAChR-α1 (CHRNA1), nAChR-α2 (CHRNA2), nAChR-α3 (CHRNA3), nAChR-α4 (CHRNA4), nAChR-α5 (CHRNA5), nAChR-α6 (CHRNA6), nAChR-α7 (CHRNA7), nAChR-α8 (CHRNA8), nAChR-α9 (CHRNA9), nAChR-α10 (CHRNA10)
- nAChR-β1 (CHRNB1), nAChR-β2 (CHRNB2), nAChR-β3 (CHRNB3), nAChR-β4 (CHRNB4)
- nAChR-δ (CHRND), nAChR-ε (CHRNE), nAChR-γ (CHRNG)
[edit] The ionotropic glutamate receptors
[edit] The ATP-gated channels
[edit] 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.[3][4] In particular, the GABA and NMDA receptors are affected by anaesthetic agents at concentrations similar to those used in clinical anaesthesia.[5]
[edit] See also
[edit] References
- ^ Connolly CN, Wafford KA (2004). "The Cys-loop superfamily of ligand-gated ion channels: the impact of receptor structure on function". Biochem. Soc. Trans. 32 (Pt3): 529–34. doi: . PMID 15157178.
- ^ Cascio M (2004). "Structure and function of the glycine receptor and related nicotinicoid receptors". J. Biol. Chem. 279 (19): 19383–6. doi: . PMID 15023997.
- ^ Krasowski MD, Harrison NL (1999). "General anaesthetic actions on ligand-gated ion channels". Cell. Mol. Life Sci. 55 (10): 1278–303. doi: . PMID 10487207.
- ^ Dilger JP (2002). "The effects of general anaesthetics on ligand-gated ion channels". Br J Anaesth 89 (1): 41–51. doi: . 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.
[edit] External links
- Ligand-Gated Ion Channel database at European Bioinformatics Institute. Verified availability April 11, 2007.
|
|