G_q protein or G_q/11 is a heterotrimeric G protein

Heterotrimeric G protein

"G protein" usually refers to the membrane-associated heterotrimeric G proteins, sometimes referred to as the "large" G proteins. These proteins are activated by G protein-coupled receptors and are made up of alpha , beta and gamma subunits, the latter two referred to as the beta-gamma...

 subunit that activates phospholipase C

Phospholipase C

Phosphoinositide phospholipase C is a family of eukaryotic intracellular enzymes that play an important role in signal transduction processes. In general, this enzyme is denoted as Phospholipase C, although three other families of phospholipase C enzymes have been identified in bacteria and in...

 (PLC). PLC in turn hydrolyzes Phosphatidylinositol 4,5-bisphosphate

Phosphatidylinositol 4,5-bisphosphate

Phosphatidylinositol 4,5-bisphosphate or PtdInsP2, also known simply as PIP2, is a minor phospholipid component of cell membranes...

 (PIP₂) to diacyl glycerol (DAG) and inositol triphosphate

Inositol triphosphate

Inositol trisphosphate or inositol 1,4,5-trisphosphate , together with diacylglycerol , is a secondary messenger molecule used in signal transduction and lipid signaling in biological cells. While DAG stays inside the membrane, IP3 is soluble and diffuses through the cell...

 (IP₃) signal transduction

Signal transduction

Signal transduction occurs when an extracellular signaling molecule activates a cell surface receptor. In turn, this receptor alters intracellular molecules creating a response...

 pathway

Metabolic pathway

In biochemistry, metabolic pathways are series of chemical reactions occurring within a cell. In each pathway, a principal chemical is modified by a series of chemical reactions. Enzymes catalyze these reactions, and often require dietary minerals, vitamins, and other cofactors in order to function...

. DAG acts as a second messenger that activates Protein Kinase C

Protein kinase C

Protein kinase C also known as PKC is a family of enzymes that are involved in controlling the function of other proteins through the phosphorylation of hydroxyl groups of serine and threonine amino acid residues on these proteins. PKC enzymes in turn are activated by signals such as increases in...

 (PKC) and IP₃ helps in phosphorylation of some proteins.

Function

G_q proteins are class of G proteins which work to activate phospholipase C (PLC), participating in a variety of cellular signaling pathways, including taste, manic depression, tumor promotion, etc.

The G_q protein works by activating PLC. PLC then cleaves a phospholipid

Phospholipid

Phospholipids are a class of lipids that are a major component of all cell membranes as they can form lipid bilayers. Most phospholipids contain a diglyceride, a phosphate group, and a simple organic molecule such as choline; one exception to this rule is sphingomyelin, which is derived from...

. In the process, phosphatidylinositol 4,5-bisphosphate

Phosphatidylinositol 4,5-bisphosphate

Phosphatidylinositol 4,5-bisphosphate or PtdInsP2, also known simply as PIP2, is a minor phospholipid component of cell membranes...

 (PIP2) is cleaved into diacyl glycerol (DAG) and inositol 1,4,5-triphosphate (IP₃). DAG remains bound to the membrane, and IP₃ is released as a soluble structure into the cytosol

Cytosol

The cytosol or intracellular fluid is the liquid found inside cells, that is separated into compartments by membranes. For example, the mitochondrial matrix separates the mitochondrion into compartments....

. IP₃ then diffuses through the cytosol to bind to IP₃ receptors

Inositol triphosphate receptor

Inositol trisphosphate receptor is a membrane glycoprotein complex acting as Ca2+ channel activated by inositol trisphosphate . InsP3R is very diverse among organisms, and is necessary for the control of cellular and physiological processes including cell division, cell proliferation, apoptosis,...

, particular calcium channel

Calcium channel

A Calcium channel is an ion channel which displays selective permeability to calcium ions. It is sometimes synonymous as voltage-dependent calcium channel, although there are also ligand-gated calcium channels.-Comparison tables:...

s in the endoplasmic reticulum

Endoplasmic reticulum

The endoplasmic reticulum is an organelle of cells in eukaryotic organisms that forms an interconnected network of tubules, vesicles, and cisternae...

 (ER). These channels are specific to calcium

Calcium

Calcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft gray alkaline earth metal, and is the fifth-most-abundant element by mass in the Earth's crust...

 and only allow the passage of calcium to move through. This causes the cytosolic concentration of calcium to increase, causing a cascade of intracellular changes and activity.

Further reading:Calcium function in vertebrates

In addition, calcium and DAG together works to activate PKC, which goes on to phosphorylate other molecules, leading to altered cellular activity.

Further reading:function of protein kinase C

Examples of GPCR partners

From modulatory neurotransmitter

Neurotransmitter

Neurotransmitters are endogenous chemicals that transmit signals from a neuron to a target cell across a synapse. Neurotransmitters are packaged into synaptic vesicles clustered beneath the membrane on the presynaptic side of a synapse, and are released into the synaptic cleft, where they bind to...

 receptors (amine

Amine

Amines are organic compounds and functional groups that contain a basic nitrogen atom with a lone pair. Amines are derivatives of ammonia, wherein one or more hydrogen atoms have been replaced by a substituent such as an alkyl or aryl group. Important amines include amino acids, biogenic amines,...

 receptors belonging to rhodopsin

Rhodopsin

Rhodopsin, also known as visual purple, is a biological pigment of the retina that is responsible for both the formation of the photoreceptor cells and the first events in the perception of light. Rhodopsins belong to the G-protein coupled receptor family and are extremely sensitive to light,...

 family), G_q is usually coupled to e.g. the G-protein coupled receptors:

• 5-HT₂ serotonergic receptors
  5-HT receptor
  The serotonin receptors, also known as 5-hydroxytryptamine receptors or 5-HT receptors, are a group of G protein-coupled receptors and ligand-gated ion channels found in the central and peripheral nervous systems. They mediate both excitatory and inhibitory neurotransmission...
  
  
• Alpha-1 adrenergic receptor
  Alpha-1 adrenergic receptor
  The alpha-1 adrenergic receptor is a G protein-coupled receptor associated with the Gq heterotrimeric G-protein. It consists of three highly homologous subtypes, including α1A-, α1B-, and α1D-adrenergic...
  
  
• Vasopressin type 1 receptor
• Angiotensin II receptor type 1
  Angiotensin II receptor type 1
  Angiotensin II receptor, type 1 or AT1 receptor is an angiotensin receptor. It has vasopressor effects and regulates aldosterone secretion. It is an important effector controlling blood pressure and volume in the cardiovascular system...
  
  
• Calcitonin receptor
  Calcitonin receptor
  The calcitonin receptor is a G protein-coupled receptor that binds the peptide hormone calcitonin and is involved in maintenance of calcium homeostasis, particularly with respect to bone formation and metabolism ....
  
  
• Histamine H1 receptor
• Metabotropic glutamate receptor
  Metabotropic glutamate receptor
  The metabotropic glutamate receptors, or mGluRs, are a type of glutamate receptor that are active through an indirect metabotropic process. They are members of the group C family of G-protein-coupled receptors, or GPCRs...
  
  , Group I
• M₁
  Muscarinic acetylcholine receptor M1
  The muscarinic acetylcholine receptor M1, also known as the cholinergic receptor, muscarinic 1, is a muscarinic receptor.This receptor is found mediating slow EPSP at the ganglion in the postganglionic nerve, is common in exocrine glands and in the CNS.It is predominantly found bound to G proteins...
  
  , M₃
  Muscarinic acetylcholine receptor M3
  The muscarinic acetylcholine receptor M3, also known as the cholinergic receptor, muscarinic 3, is a muscarinic acetylcholine receptor. It is encoded by the human gene CHRM3....
  
  , and M₅
  Muscarinic acetylcholine receptor M5
  The human muscarinic acetylcholine receptor M5 which is encoded by the gene is a member of the G protein-coupled receptor superfamily of integral membrane proteins. Binding of the endogenous ligand acetylcholine to the M5 receptor triggers a number of cellular responses such as adenylate cyclase...
  
   muscarinic receptors

Mnemonics

An easy mnemonic used in medical school to remember which receptor utilizes the Gq subunit would be: "Kiss and Kick until you're sick of sex." (i.e. QISS and QIQ until you're SIQ of SQS.") QISS = adrenergic (alpha1, alpha2, beta1, beta2), QIQ (M1, M2, M3), SIQ (Dopamine1, dopamine2, Histamine1), SQS (Histamine 2, Vasopressin1, Vasopressin 2).

• G_q = Q
• G_i = I
• G_s = S