Gi alpha subunit

Updated on Dec 09, 2023

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Symbol GNAI1 HUGO 4384 RefSeq NM_002069		Entrez 2770 OMIM 139310 UniProt P63096

G_i alpha subunit (G_αi, or G_i/G₀ or G_i protein) is a heterotrimeric G protein subunit that inhibits the production of cAMP from ATP. A mnemonic for remembering this subunit is to look at first letter (G_αi = Adenylyl Cyclase inhibitor).

Receptors

The following G protein-coupled receptors couple to the G_i subunit:

Acetylcholine M₂ & M₄ receptors

Adenosine A₁ & A₃ receptors

Adrenergic α_2A, α_2B, & α_2C receptors

Apelin receptors

Calcium-sensing receptor

Cannabinoid receptors (CB1 and CB2)

Chemokine CXCR4 receptor

Dopamine D₂, D₃, D₄

GABA_B receptor

Glutamate mGluR₂, mGluR₃, mGluR₄, mGluR₆, mGluR₇, & mGluR₈ receptors

Histamine H₃ & H₄ receptors

Melatonin MT₁, MT₂, & MT₃ receptors

Niacin receptors NIACR1 & NIACR2

Opioid δ, κ, μ, & nociceptin receptors

Prostaglandin EP₁, EP₃, FP, & TP receptors

Serotonin 5-HT₁ & 5-HT₅ receptors

Short chain fatty acid receptors: FFAR2 & FFAR3

Somatostatin sst1, sst2, sst3, sst4 & sst5 receptors

Trace amine-associated receptor 8

Function

G_i mainly inhibits the cAMP dependent pathway by inhibiting adenylate cyclase activity, decreasing the production of cAMP from ATP, which, in turn, results in decreased activity of cAMP-dependent protein kinase. Therefore, the ultimate effect of G_i is the opposite of cAMP-dependent protein kinase.

It is also attributed a minor role in activation of the phospholipase C pathway. Growth hormone is required for normal postnatal growth, bone growth, regulatory effects on protein, carbohydrate, and lipid metabolism. although this is mainly a function of the G_q alpha subunit.

Types

There are several types of G_i: Gia1, Gia2, Gia3 and Gia4

Gia1

Gia1 or G_i1 is encoded by the gene GNAI1.

Gia2

Gia2 or G_i2 is encoded by the gene GNAI2.

Gia3

Gia3 or G_i3 is encoded by the gene GNAI3.

References

Gi alpha subunit Wikipedia

(Text) CC BY-SA

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