Browse by Function (Ion Channel)
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  • Ion channel
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  Introduction            
 

    Ion channels are pore-forming proteins that help establish and control the small voltage gradient across the plasma membrane of all living cells (see cell potential) by allowing the flow of ions down their electrochemical gradient.[1] They are present in the membranes that surround all biological cells.

 
  Basic features            
      Ion channels regulate the flow of ions across the membrane in all cells. It is an integral membrane protein; or, more typically, an assembly of several proteins. Such "multi-subunit" assemblies usually involve a circular arrangement of identical or homologous proteins closely packed around a water-filled pore through the plane of the membrane or lipid bilayer.[2][3] The pore-forming subunit(s) are called the α subunit, while the auxiliary subunits are denoted β, γ, and so on. While some channels permit the passage of ions based solely on charge, the archetypal channel pore is just one or two atoms wide at its narrowest point. It conducts a specific species of ion, such as sodium or potassium, and conveys them through the membrane single file--nearly as quickly as the ions move through free fluid. In some ion channels, passage through the pore is governed by a "gate," which may be opened or closed by chemical or electrical signals, temperature, or mechanical force, depending on the variety of channel.  
  Biological role            
      Because "voltage-activated" channels underlie the nerve impulse and because "transmitter-activated" channels mediate conduction across the synapses, channels are especially prominent components of the nervous system. Indeed, most of the offensive and defensive toxins that organisms have evolved for shutting down the nervous systems of predators and prey (e.g., the venoms produced by spiders, scorpions, snakes, fish, bees, sea snails and others) work by modulating ion channel conductance and/or kinetics. In addition, ion channels are key components in a wide variety of biological processes that involve rapid changes in cells, such as cardiac, skeletal, and smooth muscle contraction, epithelial transport of nutrients and ions, T-cell activation and pancreatic beta-cell insulin release. In the search for new drugs, ion channels are a frequent target.[4][5][6]  
  External links            
  Ligand-Gated Ion Channels From Wikipedia, the free encyclopedia  
  Reference            
  1. Hille, Bertil (2001). Ion channels of excitable membranes (third ed.). Sunderland, Mass: Sinauer Associates. ISBN 0-87893-321-2.
2. Dale Purves, George J. Augustine, David Fitzpatrick, Lawrence. C. Katz, Anthony-Samuel LaMantia, James O. McNamara, S. Mark Williams, editors, ed (2001). "Chapter 4: Channels and Transporters". Neuroscience (2nd ed.). Sinauer Associates Inc.. ISBN 0-87893-741-2.
3. Hille B, Catterall, WA (1999). "Chapter 6: Electrical Excitability and Ion Channels". in George J Siegel, Bernard W Agranoff, R. W Albers, Stephen K Fisher and Michael D Uhler. Basic neurochemistry: molecular, cellular, and medical aspects. Philadelphia: Lippincott-Raven. ISBN 0-397-51820-X.
4. Camerino DC, Tricarico D, Desaphy JF (April 2007). "Ion channel pharmacology". Neurotherapeutics 4 (2): 184–98. doi:10.1016/j.nurt.2007.01.013. PMID 17395128.
5. Verkman AS, Galietta LJ (February 2009). "Chloride channels as drug targets". Nat Rev Drug Discov 8 (2): 153–71. doi:10.1038/nrd2780. PMID 19153558.
6. Camerino DC, Desaphy JF, Tricarico D, Pierno S, Liantonio A (2008). "Therapeutic approaches to ion channel diseases". Adv. Genet. 64: 81–145. doi:10.1016/S0065-2660(08)00804-3. PMID 19161833.
 
  Introduction            
      Voltage-gated ion channels are a class of transmembrane ion channels that are activated by changes in electrical potential difference near the channel; these types of ion channels are especially critical in neurons, but are common in many types of cells.They have a crucial role in excitable neuronal and muscle tissues, allowing a rapid and co-ordinated depolarisation in response to triggering voltage change. Found along the axon and at the synapse, voltage-gated ion channels directionally propagate electrical signals.  
  Classification            
 
Channel Type Membrane transport protein: ion channels
Ca2+: Calcium channel Alpha subunit of Ca channel LCav NCav P/QCav RCav TCav
Beta subunit of Ca channel Cacnb1 Cacnb2 Cacnb3 Cacnb4
Delta subunit of Ca channel Cacna2d1 Cacna2d2 Cacna2d3 Cacna2d4
Gamma subunit of Ca channel Cacng1 Cacng2 Cacng3 Cacng4 Cacng5 Cacng6 Cacng7 Cacng8 Cacng9
Na+: Sodium channel Alpha subunit of Nav channel TTX-S Nav TTX-R Nav
Belta subunit of Nav channel NavB1 NavB2 Scn3B Scn4B
K+: Potassium channel Voltage-gate K channel ISK Kv channel KQT Kv channel Shab Kv channel Shaker Kv channel
Shal Kv channel Shaw Kv channel
Subfamily F Kv channel Subfamily G Kv channel Subfamily H Kv channel Subfamily K potassium channel Subfamily S Kv channel Subfamily V Kv channel
Inward rectifier K channel Kir1.1 Kir2.1 Kir2.2 Kir2.3 Kir2.4 Kir3.1 Kir3.2 Kir3.3 Kir3.4 Kir4.1 Kir4.2 Kir5.1 Kir6.1 Kir6.2 Kir7.1
Ca-activated K channel Large conductance K channel Small conductance K channel
Cyclic Nucleotide-Regulated channel CNG family CNGA1 CNGA2 CNGA3 CNGA4 CNGB1 CNGB3
HCN family HCN1 HCN2 HCN3 HCN4
TRP channel TRPC subfamily TRPM subfamily TRPML subfamily TRPP subfamily TRPV subfamily TRPA1 channel
 
  External links            
  Voltage-gated ion channels From Wikipedia, the free encyclopedia
The IUPHAR Compendium of Voltage-gated Ion Channels 2005
MeSH Voltage-Dependent Anion Channels

 
  References            
  1. Alabi AA, Bahamonde MI, Jung HJ, Kim JI, Swartz KJ. "Portability of Paddle Motif Function and Pharmacology in Voltage Sensors." "Nature", November 15, 2007.
2. Long SB, Tao X, Campbell EB, MacKinnon R. "Atomic Structure of a Kv Channel in a Lipid Membrane-Like Environment." "Nature", November 15, 2007.
 
  Introduction            
 

    Ligand-gated ion channels (LGICs), also referred to as ionotropic receptors or channel-linked receptors, are a group of transmembrane ion channels that are opened or closed in response to the binding of a chemical messenger (i.e., a ligand),[1] such as a neurotransmitter.[2]The binding site of endogenous ligands on LGICs protein complexes are normally located on a different portion of the protein (an allosteric binding site) compared to where the ion conduction pore is located. The direct link between ligand binding and opening or closing of the ion channel, which is characteristic of ligand-gated ion channels, is contrasted with the indirect function of metabotropic receptors, which use second messengers. Ligand-gated ion channels are also different from voltage-gated ion channels (which open and close depending on membrane potential), and stretch-activated ion channels (which open and close depending on mechanical deformation of the cell membrane).[2][3]

 
  Classification            
 
Channel Type Membrane transport protein: ion channels
Ionotropic glutamate receptors AMPA Family (GluA) GluA1(GRIA1) GluA2(GRIA2) GluA3(GRIA3) GluA4(GRIA4)
Kainate Family (GluK) GluK1(GRIK1) GluK2(GRIK2) GluK3(GRIK3) GluK4(GRIK4)
GluK5(GRIK5)
NMDA Family (GluN) GluN1(GRIN1) GluN2A(GRIN2A) GluN2B(GRIN2B)
Cys-loop recptors GABA Bate Family (GABA) Gamma Family (GABA) Alpha Family (GABA)
Rho Family (GABA)
Delta (GABA) Epsilon (GABA) Theta (GABA) PI (GABA)
Glycine (GlyR)

Alpha Family (GlyR) Beta (GlyR)

Nicotinic acetylcholine (nAChR) Alpha Family (nAChR) Beta Family (nAChR)
Delta (nAChR) Gamma (nAChR) Epsilon (nAChR)
Serotonin (5-HT) Serotonin (5-HT)
Zinc-activated ion channel (ZAC)  
ATP-gated channels P2X Family  
 
  External links            
  Ligand-Gated Ion Channels From Wikipedia, the free encyclopedia
Revised Recommendations for Nomenclature of Ligand-Gated Ion Channels IUPHAR Database of Receptors and Ion Channels. International Union of Basic and Clinical Pharmacology.
Ligand-Gated Ion Channel database at European Bioinformatics Institute. Verified availability April 11, 2007.
 
  References            
  1.ligand-gated channel at Dorland's Medical Dictionary
2. a b 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.
3.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:10.1042/BST0320529. PMID 15157178.
3. 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.
4. 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. PMID 18655795.
5. Olsen RW, Sieghart W (September 2008). "International Union of Pharmacology. LXX. Subtypes of gamma-aminobutyric acid(A) receptors: classification on the basis of subunit composition, pharmacology, and function. Update". Pharmacol. Rev. 60 (3): 243–60. doi:10.1124/pr.108.00505. PMID 18790874.
6. 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. PMID 10487207.
7. 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.
8. 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.
 
 
         
   
       
   
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