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Gq protein alpha subunit is a family of heterotrimeric G protein alpha subunits. This family is also commonly called the Gq/11 (Gq/G11) family or Gq/11/14/15 family to include closely related family members. G alpha subunits may be referred to as Gq alpha, Gαq, or Gqα. Gq proteins couple to G protein-coupled receptors to activate beta-type phospholipase C (PLC-β) enzymes. PLC-β in turn hydrolyzes phosphatidylinositol 4,5-bisphosphate (PIP2) to diacyl glycerol (DAG) and inositol trisphosphate (IP3). IP3 acts as a second messenger to release stored calcium into the cytoplasm, while DAG acts as a second messenger that activates protein kinase C (PKC).

guanine nucleotide binding protein (G protein), q polypeptide
Identifiers
SymbolGNAQ
Entrez2776
HUGO4390
OMIM600998
RefSeqNM_002072
UniProtP50148
Other data
LocusChr. 9 q21
guanine nucleotide binding protein (G protein), alpha 11 (Gq class)
Identifiers
SymbolGNA11
Entrez2767
HUGO4379
OMIM139313
RefSeqNM_002067
UniProtP29992
Other data
LocusChr. 19 p13.3
guanine nucleotide binding protein (G protein), alpha 14
Identifiers
SymbolGNA14
Entrez9630
HUGO4382
OMIM604397
RefSeqNM_004297
UniProtO95837
Other data
LocusChr. 9 q21
guanine nucleotide binding protein (G protein), alpha 15 (Gq class)
Identifiers
SymbolGNA15
Entrez2769
HUGO4383
OMIM139314
RefSeqNM_002068
UniProtP30679
Other data
LocusChr. 19 p13.3

Contents

Family membersEdit

In humans, there are four distinct proteins in the Gq alpha subunit family:

  • Gqα is encoded by the gene GNAQ.
  • G11α is encoded by the gene GNA11.
  • G14α is encoded by the gene GNA14.
  • G15α is encoded by the gene GNA15.

FunctionEdit

The general function of Gq is to activate intracellular signaling pathways in response to activation of cell surface G protein-coupled receptors (GPCRs). GPCRs function as part of a three-component system of receptor-transducer-effector.[1][2] The transducer in this system is a heterotrimeric G protein, composed of three subunits: a Gα protein such as Gqα, and a complex of two tightly linked proteins called Gβ and Gγ in a Gβγ complex.[1][2] When not stimulated by a receptor, Gα is bound to guanosine diphosphate (GDP) and to Gβγ to form the inactive G protein trimer.[1][2] When the receptor binds an activating ligand outside the cell (such as a hormone or neurotransmitter), the activated receptor acts as a guanine nucleotide exchange factor to promote GDP release from and guanosine triphosphate (GTP) binding to Gα, which drives dissociation of GTP-bound Gα from Gβγ.[1][2] GTP-bound Gα and Gβγ are then freed to activate their respective downstream signaling enzymes.

Gq/11/14/15 proteins all activate beta-type phospholipase C (PLC-β) to signal through calcium and PKC signaling pathways.[3] PLC-β then cleaves a specific plasma membrane phospholipid, phosphatidylinositol 4,5-bisphosphate (PIP2) into diacyl glycerol (DAG) and inositol 1,4,5-trisphosphate (IP3). DAG remains bound to the membrane, and IP3 is released as a soluble molecule into the cytoplasm. IP3 diffuses to bind to IP3 receptors, a specialized calcium channel in the endoplasmic reticulum (ER). These channels are specific to calcium and only allow the passage of calcium from the ER into the cytoplasm. Since cells actively sequester calcium in the ER to keep cytoplasmic levels low, this release causes the cytosolic concentration of calcium to increase, causing a cascade of intracellular changes and activity through calcium binding proteins and calcium-sensitive processes.[3]

Further reading: Calcium function in vertebrates

DAG works together with released calcium to activate specific isoforms of PKC, which are activated to phosphorylate other molecules, leading to further altered cellular activity.[3]

Further reading: function of protein kinase C

ReceptorsEdit

The following G protein-coupled receptors couple to Gq subunits:

At least some Gq-coupled receptors (e.g., the muscarinic acetylcholine M3 receptor) can be found preassembled (pre-coupled) with Gq. The common polybasic domain in the C-tail of Gq-coupled receptors appears necessary for this receptor¬G protein preassembly.[4]

See alsoEdit

ReferencesEdit

  1. ^ a b c d Gilman AG (1987). "G proteins: transducers of receptor-generated signals". Annual Review of Biochemistry. 56: 615–649. doi:10.1146/annurev.bi.56.070187.003151.
  2. ^ a b c d Rodbell M (1995). "Nobel Lecture: Signal transduction: Evolution of an idea". Bioscience Reports. 15 (3): 117–133. doi:10.1007/bf01207453.
  3. ^ a b c Alberts B, Lewis J, Raff M, Roberts K, Walter P (2002). Molecular biology of the cell (4th ed.). New York: Garland Science. ISBN 0-8153-3218-1.
  4. ^ a b Qin K, Dong C, Wu G, Lambert NA (August 2011). "Inactive-state preassembly of Gq-coupled receptors and Gq heterotrimers". Nature Chemical Biology. 7 (11): 740–747. doi:10.1038/nchembio.642. PMC 3177959. PMID 21873996.

External linksEdit