Gi alpha subunit

2018-12-18T16:57:45Z

161.23.139.200: Removed duplicate ('muscarinic M2 receptor' is the same as the 'acetylcholine M2' receptor)

{{DISPLAYTITLE:Gi alpha subunit}}
{{infobox protein
| Name = [[GNAI1|G protein subunit alpha i1]]
| caption =
| image =
| width =
| HGNCid = 4384
| Symbol = [[GNAI1]]
| AltSymbols =
| EntrezGene = 2770
| OMIM = 139310
| RefSeq = NM_002069
| UniProt = P63096
| PDB = 3UMR
| ECnumber =
| Chromosome = 7
| Arm = q
| Band = 21
| LocusSupplementaryData = -q22
}}
{{infobox protein
| Name = [[GNAI2|G protein subunit alpha i2]]
| caption =
| image =
| width =
| HGNCid = 4385
| Symbol = [[GNAI2]]
| AltSymbols =
| EntrezGene = 2771
| OMIM = 139360
| RefSeq = NM_002070
| UniProt = P04899
| PDB =
| ECnumber =
| Chromosome = 3
| Arm = p
| Band = 21
| LocusSupplementaryData =
}}
{{infobox protein
| Name = [[GNAI3|G protein subunit alpha i3]]
| caption =
| image =
| width =
| HGNCid = 4387
| Symbol = [[GNAI3]]
| AltSymbols =
| EntrezGene = 2773
| OMIM = 139370
| RefSeq = NM_006496
| UniProt = P08754
| PDB = 2ODE
| ECnumber =
| Chromosome = 1
| Arm = p
| Band = 13
| LocusSupplementaryData =
}}
{{infobox protein
| Name = [[GNAO1|G protein subunit alpha o1]]
| caption =
| image =
| width =
| HGNCid = 4389
| Symbol = [[GNAO1]]
| AltSymbols =
| EntrezGene = 2775
| OMIM = 139311
| RefSeq = NM_020988
| UniProt = P09471
| PDB =
| ECnumber =
| Chromosome = 16
| Arm = q
| Band = 13
| LocusSupplementaryData =
}}
'''Gi alpha subunit''' ('''Gαi''', or '''Gi/G0''' or '''Gi protein''') is a [[heterotrimeric G protein]] subunit that inhibits the production of [[Cyclic adenosine monophosphate|cAMP]] from [[Adenosine triphosphate|ATP]].<ref name="pmid17258171">{{cite journal | author = Birnbaumer L | title = Expansion of signal transduction by G proteins. The second 15 years or so: from 3 to 16 alpha subunits plus betagamma dimers | journal = Biochim. Biophys. Acta | volume = 1768 | issue = 4 | pages = 772–93 |date=April 2007 | pmid = 17258171 | pmc = 1993906 | doi = 10.1016/j.bbamem.2006.12.002 | url = | issn = }}</ref> A mnemonic for remembering this subunit is to look at first letter (G'''αi''' = [[Adenylyl cyclase|'''A'''denylyl Cyclase]] '''i'''nhibitor).

== Receptors ==

The following [[G protein-coupled receptors]] couple to the Gi subunit:

* [[Acetylcholine]] [[Muscarinic acetylcholine receptor M2|M2]] & [[Muscarinic acetylcholine receptor M4|M4]] receptors
* [[Adenosine]] [[Adenosine receptor A1|A1]] & [[Adenosine receptor A3|A3]] receptors
* [[Adrenergic]] [[ADRA2A|α2A]], [[ADRA2B|α2B]], & [[ADRA2C|α2C]] receptors
* [[Apelin]] receptors
* [[Calcium-sensing receptor]]
* [[Cannabinoid receptor]]s ([[Cannabinoid receptor type 1|CB1]] and [[Cannabinoid receptor type 2|CB2]])
* [[Chemokine]] [[CXCR4]] receptor
* [[Dopamine]] [[Dopamine D2 receptor|D2]], [[Dopamine D3 receptor|D3]], [[Dopamine D4 receptor|D4]]
* [[GABA-B receptor|GABAB]] receptor
* [[Glutamate]] [[MGlu2|mGlu2]], [[MGlu3|mGlu3]], [[mGluR4|mGlu4]], [[mGluR6|mGlu6]], [[mGluR7|mGlu7]], & [[mGluR8|mGlu8]] receptors
* [[Histamine]] [[Histamine H3 receptor|H3]] & [[Histamine H4 receptor|H4]] receptors
* [[Melatonin]] [[MTNR1A|MT1]], [[MTNR1B|MT2]], & [[MTNR1C|MT3]] receptors
* [[Hydroxycarboxylic acid receptors]]: [[HCA1]], [[HCA2]], & [[HCA3]]
* [[Opioid]] [[Delta Opioid receptor|δ]], [[Kappa Opioid receptor|κ]], [[Mu Opioid receptor|μ]], & [[Nociceptin receptor|nociceptin]] receptors
* [[Prostaglandin]] [[PTGER1|EP1]], [[PTGER3|EP3]], [[FP receptor|FP]], & [[Thromboxane receptor|TP]] receptors
* [[Serotonin]] [[5-HT1|5-HT1]] & [[5-HT5A|5-HT5]] receptors
* [[Short chain fatty acid]] receptors: [[FFAR2]] & [[FFAR3]]
* [[Somatostatin]] [[Somatostatin receptor 1|sst1]], [[Somatostatin receptor 2|sst2]], [[Somatostatin receptor 3|sst3]], [[Somatostatin receptor 4|sst4]] & [[Somatostatin receptor 5|sst5]] receptors
* [[Trace amine-associated receptor 8]]

== Function ==

{{See also|function of cAMP-dependent protein kinase}}

Gi mainly inhibits the [[cAMP dependent pathway]] by inhibiting adenylate cyclase activity, decreasing the production of [[Cyclic adenosine monophosphate|cAMP]] from [[Adenosine triphosphate|ATP]], which, in turn, results in decreased activity of [[cAMP-dependent protein kinase]]. Therefore, the ultimate effect of Gi is the opposite of [[function of cAMP-dependent protein kinase|cAMP-dependent protein kinase]].

It is also attributed a minor role in activation of the [[phospholipase C pathway]].<ref>{{cite journal |vauthors=Obál F, Krueger J | title = The somatotropic axis and sleep. | journal = Rev Neurol (Paris) | volume = 157 | issue = 11 Pt 2 | pages = S12–5 | year = 2001 | pmid = 11924022}}</ref> Growth hormone is required for normal postnatal growth, bone growth, regulatory effects on protein, carbohydrate, and lipid metabolism.<ref name=GeneGlobe>[https://www1.qiagen.com/GeneGlobe/PathwayView.aspx?pathwayID=199 GeneGlobe -> GHRH Signaling]{{dead link|date=October 2017 |bot=InternetArchiveBot |fix-attempted=yes }} Retrieved on May 31, 2009</ref> Although this is mainly a function of the [[Gq alpha subunit|Gq alpha subunit]].

== Types ==
There are several types of Gi: Gia1, Gia2, Gia3 and Gia4

=== Gia1 === 
Gia1 or Gi1 is encoded by the gene [[GNAI1]].

=== Gia2 === 
Gia2 or Gi2 is encoded by the gene [[GNAI2]].

=== Gia3 === 
Gia3 or Gi3 is encoded by the gene [[GNAI3]].

== See also ==
* [[Second messenger system]]

== References ==
{{Reflist}}

== External links ==
* {{MeshName|Gi+alpha+Subunit}}

{{Intracellular signaling peptides and proteins}}
{{Acid anhydride hydrolases}}
{{Enzymes}}
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[[Category:G proteins|*]]
[[Category:Peripheral membrane proteins]]

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Gi alpha subunit