WordNet

direct the flow of; "channel information towards a broad audience" (同)canalize, canalise
a television station and its programs; "a satellite TV channel"; "surfing through the channels"; "they offer more than one hundred channels" (同)television channel, TV channel
a passage for water (or other fluids) to flow through; "the fields were crossed with irrigation channels"; "gutters carried off the rainwater into a series of channels under the street"
(often plural) a means of communication or access; "it must go through official channels"; "lines of communication were set up between the two firms" (同)communication channel, line
a path over which electrical signals can pass; "a channel is typically what you rent from a telephone company" (同)transmission channel
a deep and relatively narrow body of water (as in a river or a harbor or a strait linking two larger bodies) that allows the best passage for vessels; "the ship went aground in the channel"
relying on or requiring a person or thing for support, supply, or what is needed; "dependent children"; "dependent on moisture"
addicted to a drug (同)dependant, drug-addicted, hooked, strung-out
contingent on something else (同)dependant, qualified
(of a clause) unable to stand alone syntactically as a complete sentence; "a subordinate (or dependent) clause functions as a noun or adjective or adverb within a sentence" (同)subordinate
the rate at which energy is drawn from a source that produces a flow of electricity in a circuit; expressed in volts (同)electromotive_force, emf
a particle that is electrically charged (positive or negative); an atom or molecule or group that has lost or gained one or more electrons
official routes of communication; "you have to go through channels"

PrepTutorEJDIC

〈C〉『水路』(川・湾・運河の船の通行ができる深い部分) / 〈U〉河床・川底 / 〈C〉『海峡』 / 〈C〉みぞ(groove),(道路の)水渠(すいきょ) / 《複数形で》(運搬・伝達の)正式の経路(手続き);(一般に)経路 / 〈C〉(テレビ・ラジオの)チャンネル / …‘に'水路を開く / …‘に'みぞを堀る / …'を'伝える,流す
『頼っている』,依存している,従属している / 扶養される人(家族)
電圧,電圧量,ボルト数
イオン

Wikipedia preview

出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2015/05/15 09:01:27」(JST)

wiki en

Voltage-gated ion channels are a class of transmembrane ion channels that are activated by changes in electrical membrane potential 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 depolarization in response to triggering voltage change. Found along the axon and at the synapse, voltage-gated ion channels directionally propagate electrical signals.

Structure

They generally are composed of several subunits arranged in such a way that there is a central pore through which ions can travel down their electrochemical gradients. The channels tend to be ion-specific, although similarly sized and charged ions may sometimes travel through them.

Examples include:

the sodium and potassium voltage-gated channels of nerve and muscle.
the voltage-gated calcium channels that play a role in neurotransmitter release in pre-synaptic nerve endings.

Mechanism

From crystallographic structural studies of a potassium channel, assuming that this structure remains intact in the corresponding plasma membrane, it is possible to surmise that when a potential difference is introduced over the membrane, the associated electric field induces a conformational change in the potassium channel. The conformational change distorts the shape of the channel proteins sufficiently such that the cavity, or channel, opens to admit ion influx or efflux to occur across the membrane, down its electrochemical gradient. This subsequently generates an electrical current sufficient to depolarise the cell membrane.

Voltage-gated sodium channels and calcium channels are made up of a single polypeptide with four homologous domains. Each domain contains 6 membrane spanning alpha helices. One of these helices, S4, is the voltage sensing helix.^[1] It has many positive charges such that a high positive charge outside the cell repels the helix, keeping the channel in its closed state. Depolarization of the cell interior causes the helix to move, inducing a conformational change such that ions may flow through the channel (the open state). Potassium channels function in a similar way, with the exception that they are composed of four separate polypeptide chains, each comprising one domain.

The voltage-sensitive protein domain of these channels (the "voltage sensor") generally contains a region composed of S3b and S4 helices, known as the "paddle" due to its shape, which appears to be a conserved sequence, interchangeable across a wide variety of cells and species. A similar voltage sensor paddle has also been found in a family of voltage sensitive phosphatases in various species.^[2] Genetic engineering of the paddle region from a species of volcano-dwelling archaebacteria into rat brain potassium channels results in a fully functional ion channel, as long as the whole intact paddle is replaced.^[3] This "modularity" allows use of simple and inexpensive model systems to study the function of this region, its role in disease, and pharmaceutical control of its behavior rather than being limited to poorly characterized, expensive, and/or difficult to study preparations.^[4]

Although voltage-gated ion channels are typically activated by membrane depolarization, some channels, such as inward-rectifier potassium ion channels, are activated instead by hyperpolarization.

References

^ Voltage sensor in the voltage gated sodium and potassium channels | PharmaXChange.info
^ Murata, Y.; Iwasaki, H.; Sasaki, M.; Inaba, K.; Okamura, Y. (2005). "Phosphoinositide phosphatase activity coupled to an intrinsic voltage sensor". Nature 435 (7046): 1239–1243. doi:10.1038/nature03650. PMID 15902207.
^ Alabi AA, Bahamonde MI, Jung HJ, Kim JI, Swartz KJ (November 2007). "Portability of paddle motif function and pharmacology in voltage sensors". Nature 450 (7168): 370–5. doi:10.1038/nature06266. PMC 2709416. PMID 18004375.
^ Long SB, Tao X, Campbell EB, MacKinnon R (November 2007). "Atomic structure of a voltage-dependent K+ channel in a lipid membrane-like environment". Nature 450 (7168): 376–82. doi:10.1038/nature06265. PMID 18004376.

External links

IUPHAR-DB Voltage-gated ion channel subunits
The IUPHAR Compendium of Voltage-gated Ion Channels 2005
Voltage-Dependent Anion Channels at the US National Library of Medicine Medical Subject Headings (MeSH)

UpToDate Contents

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4. 心筋活動電位および抗不整脈剤の作用 myocardial action potential and action of antiarrhythmic drugs
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English Journal

Expression and function of the Scn5a-encoded voltage-gated sodium channel NaV 1.5 in the rat jejunum.

Beyder A1, Gibbons SJ1, Mazzone A1, Strege PR1, Saravanaperumal SA1, Sha L1, Higgins S2, Eisenman ST1, Bernard CE1, Geurts A3, Kline CF4, Mohler PJ4, Farrugia G1.
Neurogastroenterology and motility : the official journal of the European Gastrointestinal Motility Society.Neurogastroenterol Motil.2016 Jan;28(1):64-73. doi: 10.1111/nmo.12697. Epub 2015 Oct 13.
BACKGROUND: The SCN5A-encoded voltage-gated sodium channel NaV 1.5 is expressed in human jejunum and colon. Mutations in NaV 1.5 are associated with gastrointestinal motility disorders. The rat gastrointestinal tract expresses voltage-gated sodium channels, but their molecular identity and role in r
PMID 26459913

Molecular Basis of Regulating High Voltage-Activated Calcium Channels by S-Nitrosylation.

Zhou MH1, Bavencoffe A1, Pan HL2.
The Journal of biological chemistry.J Biol Chem.2015 Dec 18;290(51):30616-23. doi: 10.1074/jbc.M115.685206. Epub 2015 Oct 27.
Nitric oxide (NO) is involved in a variety of physiological processes, such as vasoregulation and neurotransmission, and has a complex role in the regulation of pain transduction and synaptic transmission. We have shown previously that NO inhibits high voltage-activated Ca(2+) channels in primary se
PMID 26507659

N-helix and Cysteines Inter-regulate Human Mitochondrial VDAC-2 Function and Biochemistry.

Maurya SR1, Mahalakshmi R2.
The Journal of biological chemistry.J Biol Chem.2015 Dec 18;290(51):30240-52. doi: 10.1074/jbc.M115.693978. Epub 2015 Oct 20.
Human voltage-dependent anion channel-2 (hVDAC-2) functions primarily as the crucial anti-apoptotic protein in the outer mitochondrial membrane, and additionally as a gated bidirectional metabolite transporter. The N-terminal helix (NTH), involved in voltage sensing, bears an additional 11-residue e
PMID 26487717

Japanese Journal

心臓イオンチャネルに作用する薬物の効果に関するシステム論的理解

古谷久和春,倉智嘉久
Drug Delivery System 29(5), 397-407, 2014
システムズバイオロジーのアプローチを薬理学に適用したものがシステムズ薬理学だといえる。薬物の有効性や毒性を生命の複雑なシステムのなかで理解しようとするものである。薬物の分子作用を定式化し、生体への影響をシミュレートする研究が行われ、これにより薬物を生体に投与したときの効果を予測することが可能となりつつある。このような研究により得られた薬物作用のシステム論的理解は創薬や医療を変えるものであると期待さ …
NAID 130004874239

Calcium Ions Released from Mineral Trioxide Aggregate are Taken Up by C2C12 Cells via the L-Type Voltage-Dependent Calcium Channel

Matsumoto Sakurako,Hayashi Makoto,Tanabe Natsuko [他]
Journal of hard tissue biology 22(1), 13-18, 2013-01
NAID 40019635296

Calcium Ions Released from Mineral Trioxide Aggregate are Taken Up by C2C12 Cells via the L-Type Voltage-Dependent Calcium Channel

Matsumoto Sakurako,Hayashi Makoto,Tanabe Natsuko,Suzuki Yusuke,Kobayashi Yoshimi,Kobayashi Hiroshi,Suzuki Naoto,Maeno Masao,Ogiso Bunnai
Journal of Hard Tissue Biology 22(1), 13-18, 2013
… To clarify the specific effects of MTA-derived calcium ions, we used calcium chloride as an exogenous calcium ion source and ethylene glycol tetraacetic acid (EGTA) as a calcium chelator. … Moreover, MTA did not affect FI in C2C12 cells pre-incubated with verapamil, an L-type voltage-dependent calcium channel (VDCCL) blocker. …
NAID 130004848401

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