Editing Calcium channel

{{Short description|Ion channel complex through which calcium ions pass}}
A '''calcium channel''' is an [[ion channel]] which shows selective permeability to [[calcium]] ions. It is sometimes synonymous with [[voltage-gated calcium channel]],<ref>{{DorlandsDict|two/000019812|calcium channel}}</ref> which are a type of calcium channel regulated by changes in [[membrane potential]]. Some calcium channels are regulated by the binding of a [[ligand]].<ref name="boron">Striggow F, Ehrlich BE (August 1996). "Ligand-gated calcium channels inside and out". ''Current Opinion in Cell Biology''. '''8''' (4): 490–495. [[Doi (identifier)|doi]]:[[doi:10.1016/S0955-0674(96)80025-1|10.1016/S0955-0674(96)80025-1]]. [[PMID (identifier)|PMID]] [https://pubmed.ncbi.nlm.nih.gov/8791458/ 8791458].</ref><ref>{{Cite journal |last=Zamponi |first=Gerald W. |date=2017-12-20 |title=A Crash Course in Calcium Channels |journal=ACS Chemical Neuroscience |language=en |volume=8 |issue=12 |pages=2583–2585 |doi=10.1021/acschemneuro.7b00415 |pmid=29131938 |issn=1948-7193|doi-access=free }}</ref> Other calcium channels can also be regulated by both voltage and ligands to provide precise control over ion flow. Some cation channels allow calcium as well as other cations to pass through the membrane.

Calcium channels can participate in the creation of [[Action potential|action potentials]] across cell membranes. Calcium channels can also be used to release calcium ions as [[Second messenger system|second messengers]] within the cell, affecting downstream signaling pathways.   ''' '''

==Comparison tables==
The following tables explain gating, gene, location and function of different types of calcium channels, both voltage and ligand-gated.

===Voltage-gated===
{{Main|voltage-gated calcium channel}}

* ''voltage-operated calcium channels'' 

{| class="wikitable"  | style="text-align:center"
| '''Type''' || '''Voltage''' || '''α<sub>1</sub> subunit (gene name)''' || '''Associated subunits''' || '''Most often found in''' 
 |- 
 | [[L-type calcium channel]] ("Long-Lasting" AKA "DHP Receptor")|| HVA (high voltage activated)|| [[Cav1.1|Ca<sub>v</sub>1.1]] ({{Gene|CACNA1S}})<br /> [[Cav1.2|Ca<sub>v</sub>1.2]] ({{Gene|CACNA1C}}) [[Cav1.3|Ca<sub>v</sub>1.3]] ({{Gene|CACNA1D}})<br /> [[Cav1.4|Ca<sub>v</sub>1.4]] ({{Gene|CACNA1F}}) || α<sub>2</sub>δ, β, γ || Skeletal muscle, smooth muscle, bone (osteoblasts), ventricular myocytes** (responsible for prolonged action potential in cardiac cell; also termed DHP receptors), dendrites and dendritic spines of cortical neurons
 |- 
 | [[N-type calcium channel]] ("Neural"/"Non-L") || HVA (high-voltage-activated) || [[N-type calcium channel|Ca<sub>v</sub>2.2]] ({{Gene|CACNA1B}}) || α<sub>2</sub>δ/β<sub>1</sub>, β<sub>3</sub>, β<sub>4</sub>, possibly γ || Throughout the [[brain]] and peripheral nervous system.
 |- 
 | [[P-type calcium channel]] ("Purkinje") /[[Q-type calcium channel]] || HVA (high voltage activated) || [[Cav2.1|Ca<sub>v</sub>2.1]] ({{Gene|CACNA1A}}) || α<sub>2</sub>δ, β, possibly γ || [[Purkinje neurons]] in the cerebellum / [[Cerebellum|Cerebellar]] [[granule cell]]s
 |- 
 | [[R-type calcium channel]] ("Residual") || intermediate-voltage-activated || [[R-type calcium channel|Ca<sub>v</sub>2.3]] ({{Gene|CACNA1E}}) || α<sub>2</sub>δ, β, possibly γ || [[Cerebellum|Cerebellar]] [[granule cell]]s, other neurons
 |- 
 | [[T-type calcium channel]] ("Transient") || low-voltage-activated || [[CACNA1G|Ca<sub>v</sub>3.1]] ({{Gene|CACNA1G}})<br /> [[CACNA1H|Ca<sub>v</sub>3.2]] ({{Gene|CACNA1H}})<br /> [[CACNA1I|Ca<sub>v</sub>3.3]] ({{Gene|CACNA1I}}) || || neurons, cells that have [[pacemaker]] activity, bone ([[osteocytes]]), thalamus ([[thalamus]])  
|}

===Ligand-gated===
*''receptor-operated calcium channels'' 

{| class="wikitable"  | style="text-align:center"
| '''Type''' || '''Gated by''' || '''Gene''' || '''Location''' || '''Function''' 
 |- 
 | [[Inositol triphosphate receptor|IP<sub>3</sub> receptor]] || [[inositol triphosphate|IP<sub>3</sub>]] || ITPR1, ITPR2, ITPR3 || [[endoplasmic reticulum|ER]]/[[sarcoplasmic reticulum|SR]] || Releases calcium from ER/SR in response to IP<sub>3</sub> by e.g. [[GPCR]]s<ref name=Rang53>{{cite book | vauthors = Rang HP |title=Pharmacology |publisher=Churchill Livingstone |location=Edinburgh |year=2003  |isbn=978-0-443-07145-4 |page = 54 }}</ref>
 |- 
 | [[Ryanodine receptor]] || [[dihydropyridine receptor]]s in [[T-tubule]]s and increased intracellular calcium (Calcium Induced Calcium Release - CICR) || RYR1, RYR2, RYR3 || [[endoplasmic reticulum|ER]]/[[sarcoplasmic reticulum|SR]] || [[Calcium-induced calcium release]] in [[myocyte]]s<ref name=Rang53/> 
 |- 
 | [[Two-pore channel]] ||Nicotinic acid adenine dinucleotide phosphate ([[Nicotinic acid adenine dinucleotide phosphate|NAADP]])||TPCN1, TPCN2||endosomal/lysosomal membranes||NAADP-activated calcium transport across endosomal/lysosomal membranes<ref>{{Cite web|url=https://www.uniprot.org/uniprot/Q9ULQ1|title=TPCN1 - Two pore calcium channel protein 1 - Homo sapiens (Human) - TPCN1 gene & protein|website=www.uniprot.org|language=en|access-date=2017-12-11}}</ref>
 
|- 
 | ''store-operated channels''<ref>{{Cite journal |last1=Prakriya |first1=Murali |last2=Lewis |first2=Richard S. |date=Oct 2015 |title=Store-Operated Calcium Channels |journal=Physiological Reviews |language=en |volume=95 |issue=4 |pages=1383–1436 |doi=10.1152/physrev.00020.2014 |issn=0031-9333 |pmc=4600950 |pmid=26400989}}</ref>|| indirectly by [[endoplasmic reticulum|ER]]/[[sarcoplasmic reticulum|SR]] depletion of calcium<ref name="Rang53" />|| ORAI1, ORAI2, ORAI3 || [[plasma membrane]] || Provides calcium signaling to the cytoplasm<ref>{{cite journal | vauthors = Putney JW, Steinckwich-Besançon N, Numaga-Tomita T, Davis FM, Desai PN, D'Agostin DM, Wu S, Bird GS | display-authors = 6 | title = The functions of store-operated calcium channels | journal = Biochimica et Biophysica Acta (BBA) - Molecular Cell Research| volume = 1864 | issue = 6 | pages = 900–906 | date = June 2017 | pmid = 27913208 | pmc = 5420336 | doi = 10.1016/j.bbamcr.2016.11.028 }}</ref>
 |- 
|}

== Non-selective channels permeable to calcium ==
There are several cation channel families that allow positively charged ions including calcium to pass through. These include [[P2X receptor|P2X receptors]], [[Transient receptor potential channel|Transient Receptor Potential (TRP) channels]], [[Cyclic nucleotide–gated ion channel|Cyclic nucleotide-gated (CNG) channels]], [[Acid-sensing ion channel|Acid-sensing ion channels]], and [[SOC channels]].<ref>{{Cite book |last1=Zheng |first1=Jie |url=https://www.taylorfrancis.com/books/9781003096276 |title=Textbook of Ion Channels Volume II: Properties, Function, and Pharmacology of the Superfamilies |last2=Trudeau |first2=Matthew C. |date=2023-06-06 |publisher=CRC Press |isbn=978-1-003-09627-6 |edition=1 |location=Boca Raton |language=en |doi=10.1201/9781003096276|s2cid=259784278 }}</ref> These channels can be regulated by membrane voltage potentials, ligands, and/or other cellular conditions. [[Cation channels of sperm|Cat-Sper]] channels, found in mammalian sperm, are one example of this as they are voltage gated and ligand regulated.<ref>{{Cite journal |last1=Wu |first1=Jianping |last2=Yan |first2=Zhen |last3=Li |first3=Zhangqiang |last4=Yan |first4=Chuangye |last5=Lu |first5=Shan |last6=Dong |first6=Mengqiu |last7=Yan |first7=Nieng |date=2015-12-18 |title=Structure of the voltage-gated calcium channel Ca v 1.1 complex |url=https://www.science.org/doi/10.1126/science.aad2395 |journal=Science |language=en |volume=350 |issue=6267 |pages=aad2395 |doi=10.1126/science.aad2395 |pmid=26680202 |s2cid=22271779 |issn=0036-8075|url-access=subscription }}</ref>

==Pharmacology==
[[File:L-type_calcium_channel.jpg|320x320px|Depiction of binding sites of various antagonistic drugs in the L-type calcium channel.|thumb]]
L-type [[calcium channel blocker]]s are used to treat [[hypertension]]. In most areas of the body, [[depolarization]] is mediated by sodium influx into a cell; changing the calcium permeability has little effect on action potentials. However, in many smooth muscle tissues, depolarization is mediated primarily by calcium influx into the cell. L-type calcium channel blockers selectively inhibit these action potentials in smooth muscle which leads to dilation of blood vessels; this in turn corrects hypertension.<ref>{{cite journal | vauthors = Katz AM | title = Pharmacology and mechanisms of action of calcium-channel blockers | journal = Journal of Clinical Hypertension | volume = 2 | issue = 3 Suppl | pages = 28S–37S | date = September 1986 | pmid = 3540226 }}</ref>

T-type [[calcium channel blocker]]s are used to treat [[epilepsy]]. Increased calcium conductance in the neurons leads to increased depolarization and excitability. This leads to a greater predisposition to epileptic episodes. Calcium channel blockers reduce the neuronal calcium conductance and reduce the likelihood of experiencing epileptic attacks.<ref>{{cite journal | vauthors = Zamponi GW, Lory P, Perez-Reyes E | title = Role of voltage-gated calcium channels in epilepsy | journal = Pflügers Archiv | volume = 460 | issue = 2 | pages = 395–403 | date = July 2010 | pmid = 20091047 | pmc = 3312315 | doi = 10.1007/s00424-009-0772-x }}</ref>

== See also ==

* {{annotated link|Calcium in biology}}.

== References ==
{{reflist}}

== External links ==
* {{cite web | url = http://www.theweisslab.com | title = The Weiss Lab | access-date = | date = | work = The Weiss Lab is investigating the molecular and cellular mechanisms underlying human diseases caused by dysfunction of ion channels| pages = | archive-url = | archive-date = | quote = }}
* {{cite web | url = http://www.iuphar-db.org/IC/ReceptorFamiliesForward | title = Voltage-Gated Ion Channels | work = IUPHAR Database of Receptors and Ion Channels | publisher = International Union of Basic and Clinical Pharmacology | access-date = 2008-12-17 | archive-date = 2021-04-17 | archive-url = https://web.archive.org/web/20210417093732/https://www.iuphar-db.org/IC/ReceptorFamiliesForward | url-status = dead }}
* {{cite web | url = http://www.trpchannel.org | title = TRIP Database | work = a manually curated database of protein-protein interactions for mammalian TRP channels | access-date = 2021-06-18 | archive-date = 2016-08-10 | archive-url = https://web.archive.org/web/20160810025812/http://www.trpchannel.org/ | url-status = dead }}
* {{MeshName|Calcium+Channels}}

{{Ion channels|g1}}

[[Category:Ion channels]]
[[Category:Electrophysiology]]
[[Category:Integral membrane proteins]]
[[Category:Calcium channels]]