The G
s alpha subunit (G
αs, G
sα) is a subunit of the
heterotrimeric G protein G
s that stimulates the
cAMP-dependent pathway by activating
adenylyl cyclase
Adenylate cyclase (EC 4.6.1.1, also commonly known as adenyl cyclase and adenylyl cyclase, abbreviated AC) is an enzyme with systematic name ATP diphosphate-lyase (cyclizing; 3′,5′-cyclic-AMP-forming). It catalyzes the following reaction:
:A ...
. G
sα is a
GTPase that functions as a cellular signaling protein.
G
sα is the founding member of one of the four families of heterotrimeric G proteins, defined by the
alpha subunits they contain: the G
αs family,
Gαi/Gαo family,
Gαq family, and
Gα12/Gα13 family.
The Gs-family has only two members: the other member is G
olf, named for its predominant expression in the olfactory system. In humans, G
sα is encoded by the
GNAS complex locus
GNAS complex locus is a gene locus in humans. Its main product is the heterotrimeric G-protein alpha subunit Gs-α, a key component of G protein-coupled receptor-regulated adenylyl cyclase signal transduction pathways. GNAS stands for Guanine Nuc ...
, while G
olfα is encoded by the
GNAL gene.
Function
The general function of G
s 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.
The transducer in this system is a
heterotrimeric G protein, composed of three subunits: a Gα protein such as G
sα, and a complex of two tightly linked proteins called Gβ and Gγ in a
Gβγ complex.
When not stimulated by a receptor, Gα is bound to
GDP and to Gβγ to form the inactive G protein trimer.
When the receptor binds an activating ligand outside the cell (such as a
hormone
A hormone (from the Greek participle , "setting in motion") is a class of signaling molecules in multicellular organisms that are sent to distant organs by complex biological processes to regulate physiology and behavior. Hormones are required ...
or
neurotransmitter
A neurotransmitter is a signaling molecule secreted by a neuron to affect another cell across a synapse. The cell receiving the signal, any main body part or target cell, may be another neuron, but could also be a gland or muscle cell.
Neu ...
), the activated receptor acts as a
guanine nucleotide exchange factor to promote GDP release from and
GTP binding to Gα, which drives dissociation of GTP-bound Gα from Gβγ.
In particular, GTP-bound, activated G
sα binds to
adenylyl cyclase
Adenylate cyclase (EC 4.6.1.1, also commonly known as adenyl cyclase and adenylyl cyclase, abbreviated AC) is an enzyme with systematic name ATP diphosphate-lyase (cyclizing; 3′,5′-cyclic-AMP-forming). It catalyzes the following reaction:
:A ...
to produce the
second messenger
Second messengers are intracellular signaling molecules released by the cell in response to exposure to extracellular signaling molecules—the first messengers. (Intercellular signals, a non-local form or cell signaling, encompassing both first m ...
cAMP
Camp may refer to:
Outdoor accommodation and recreation
* Campsite or campground, a recreational outdoor sleeping and eating site
* a temporary settlement for nomads
* Camp, a term used in New England, Northern Ontario and New Brunswick to descri ...
, which in turn activates the
cAMP-dependent protein kinase (also called Protein Kinase A or PKA).
Cellular effects of G
sα acting through PKA are described
here
Here is an adverb that means "in, on, or at this place". It may also refer to:
Software
* Here Technologies, a mapping company
* Here WeGo (formerly Here Maps), a mobile app and map website by Here
Television
* Here TV (formerly "here!"), a ...
.
Although each GTP-bound G
sα can activate only one adenylyl cyclase enzyme, amplification of the signal occurs because one receptor can activate multiple copies of G
s while that receptor remains bound to its activating
agonist
An agonist is a chemical that activates a receptor to produce a biological response. Receptors are cellular proteins whose activation causes the cell to modify what it is currently doing. In contrast, an antagonist blocks the action of the ag ...
, and each G
sα-bound adenylyl cyclase enzyme can generate substantial cAMP to activate many copies of PKA.
Receptors
The G protein-coupled receptors that couple to the G
s family proteins include:
*
5-HT receptor
5-HT receptors, 5-hydroxytryptamine receptors, or serotonin receptors, are a group of G protein-coupled receptor and ligand-gated ion channels found in the central and peripheral nervous systems. They mediate both excitatory and inhibitory n ...
s types
5-HT4 and
5-HT7
*
ACTH receptor a.k.a. MC2R
*
Adenosine receptor
The adenosine receptors (or P1 receptors) are a class of purinergic G protein-coupled receptors with adenosine as the endogenous ligand. There are four known types of adenosine receptors in humans: A1, A2A, A2B and A3; each is encoded by a di ...
types
A2a and
A2b
*
Arginine vasopressin receptor 2
*
β-adrenergic receptors types
β1,
β2 and
β3
*
Calcitonin receptor
*
Calcitonin gene-related peptide receptor
Calcitonin receptor-like (CALCRL), also known as the calcitonin receptor-like receptor (CRLR), is a human protein; it is a receptor for calcitonin gene-related peptide.
Function
The protein encoded by the CALCRL gene is a G protein-coupled re ...
*
Cannabinoid receptor 2
The cannabinoid receptor type 2, abbreviated as CB2, is a G protein-coupled receptor from the cannabinoid receptor family that in humans is encoded by the ''CNR2'' gene. It is closely related to the cannabinoid receptor type 1 (CB1), which is ...
*
Corticotropin-releasing hormone receptor
Corticotropin-releasing hormone receptors (CRHRs), also known as corticotropin-releasing factor receptors (CRFRs) are a G protein-coupled receptor family that binds corticotropin-releasing hormone (CRH). There are two receptors in the family, ...
*
Dopamine receptors D
1-like family (
D1 and
D5), mainly through G
olf in the
striatum
The striatum, or corpus striatum (also called the striate nucleus), is a nucleus (a cluster of neurons) in the subcortical basal ganglia of the forebrain. The striatum is a critical component of the motor and reward systems; receives gluta ...
*
FSH-receptor
The follicle-stimulating hormone receptor or FSH receptor (FSHR) is a transmembrane receptor that interacts with the follicle-stimulating hormone (FSH) and represents a G protein-coupled receptor (GPCR). Its activation is necessary for the horm ...
*
Gastric inhibitory polypeptide receptor
*
Glucagon receptor
*
Growth-hormone-releasing hormone receptor
*
Histamine H2 receptor
*
Luteinizing hormone/choriogonadotropin receptor
*
Melanocortin receptor:
MC1R,
MC2R (a.k.a. ACTH receptor),
MC3R,
MC4R,
MC5R
*
Olfactory receptors, through G
olf in the
olfactory neurons
*
Parathyroid hormone receptor 1
Parathyroid hormone/parathyroid hormone-related peptide receptor, also known as parathyroid hormone 1 receptor (PTH1R), is a protein that in humans is encoded by the ''PTH1R'' gene. PTH1R functions as a receptor for parathyroid hormone ( PTH) and ...
*
Prostaglandin receptor Prostaglandin receptors or prostanoid receptors represent a sub-class of cell surface membrane receptors that are regarded as the primary receptors for one or more of the classical, naturally occurring prostanoids viz., prostaglandin D2, (i.e. PGD2 ...
types
D2 and
I2
*
Secretin receptor
*
Thyrotropin receptor
The thyrotropin receptor (or TSH receptor) is a receptor (and associated protein) that responds to thyroid-stimulating hormone (also known as "thyrotropin") and stimulates the production of thyroxine (T4) and triiodothyronine (T3). The TSH recep ...
*
Trace amine-associated receptor 1
See also
*
Second messenger system
*
G protein-coupled receptor
G protein-coupled receptors (GPCRs), also known as seven-(pass)-transmembrane domain receptors, 7TM receptors, heptahelical receptors, serpentine receptors, and G protein-linked receptors (GPLR), form a large group of evolutionarily-related p ...
*
Heterotrimeric G protein
*
Adenylyl cyclase
Adenylate cyclase (EC 4.6.1.1, also commonly known as adenyl cyclase and adenylyl cyclase, abbreviated AC) is an enzyme with systematic name ATP diphosphate-lyase (cyclizing; 3′,5′-cyclic-AMP-forming). It catalyzes the following reaction:
:A ...
*
Protein kinase A
In cell biology, protein kinase A (PKA) is a family of enzymes whose activity is dependent on cellular levels of cyclic AMP (cAMP). PKA is also known as cAMP-dependent protein kinase (). PKA has several functions in the cell, including regulatio ...
*
Gi alpha subunit
Gi protein alpha subunit is a family of heterotrimeric G protein alpha subunits. This family is also commonly called the Gi/o (Gi /Go ) family or Gi/o/z/t family to include closely related family members. G alpha subunits may be referre ...
*
Gq alpha subunit
*
G12/G13 alpha subunits
G12/G13 alpha subunits are alpha subunits of heterotrimeric G proteins that link cell surface G protein-coupled receptors primarily to guanine nucleotide exchange factors for the Rho small GTPases to regulate the actin cytoskeleton. Together ...
References
External links
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Peripheral membrane proteins
Medical mnemonics