Editing G protein (section)

====Specific mechanisms====

=====G<sub>αs</sub>=====
'''[[Gαs|G<sub>αs</sub>]]''' activates the [[cAMP-dependent pathway]] by stimulating the production of [[cyclic AMP]] (cAMP) from [[adenosine triphosphate|ATP]]. This is accomplished by direct stimulation of the membrane-associated enzyme [[adenylate cyclase]]. cAMP can then act as a second messenger that goes on to interact with and activate [[protein kinase A]] (PKA). PKA can phosphorylate a myriad downstream targets.

The [[cAMP-dependent pathway]] is used as a signal transduction pathway for many hormones including:

* [[Antidiuretic hormone|ADH]] – Promotes water retention by the [[kidneys]] (created by the [[magnocellular neurosecretory cell]]s of the [[posterior pituitary]])
* [[GHRH]] – Stimulates the synthesis and release of GH ([[somatotropic cell]]s of the [[anterior pituitary]])
* [[GHIH]] – Inhibits the synthesis and release of GH (somatotropic cells of anterior pituitary)
* [[Corticotropin-releasing hormone|CRH]] – Stimulates the synthesis and release of ACTH (anterior pituitary)
* [[ACTH]] – Stimulates the synthesis and release of [[cortisol]] ([[zona fasciculata]] of the [[adrenal cortex]] in the adrenal glands)
* [[Thyroid-stimulating hormone|TSH]] – Stimulates the synthesis and release of a majority of [[Thyroxine|T4]] (thyroid gland)
* [[Luteinizing hormone|LH]] – Stimulates follicular maturation and ovulation in women; or testosterone production and spermatogenesis in men
* [[Follicle stimulating hormone|FSH]] – Stimulates follicular development in women; or [[spermatogenesis]] in men
* [[Parathyroid hormone|PTH]] – Increases [[blood calcium]] levels.  This is accomplished via the [[parathyroid hormone 1 receptor]] (PTH1) in the kidneys and bones, or via the [[parathyroid hormone 2 receptor]] (PTH2) in the central nervous system and brain, as well as the bones and kidneys.
* [[Calcitonin]] – Decreases blood calcium levels (via the [[calcitonin receptor]] in the intestines, bones, kidneys, and brain)
* [[Glucagon]] – Stimulates [[glycogen]] breakdown in the liver
* [[human chorionic gonadotropin|hCG]] – Promotes cellular differentiation, and is potentially involved in [[apoptosis]].<ref>{{cite journal | vauthors = Cole LA | title = Biological functions of hCG and hCG-related molecules | journal = Reproductive Biology and Endocrinology | volume = 8 | issue = 1 | pages = 102 | date = August 2010 | pmid = 20735820 | pmc = 2936313 | doi = 10.1186/1477-7827-8-102 | doi-access = free }}</ref>
* [[Epinephrine]] – released by the ''[[adrenal medulla]]'' during the fasting state, when body is under metabolic duress.  It stimulates [[glycogenolysis]], in addition to the actions of [[glucagon]].

=====G<sub>αi</sub>=====
'''[[Gαi|G<sub>αi</sub>]]''' inhibits the production of cAMP from ATP.
e.g. somatostatin, prostaglandins

=====G<sub>αq/11</sub>=====
'''[[Gαq|G<sub>αq/11</sub>]]''' stimulates the membrane-bound [[phospholipase C]] beta, which then cleaves [[phosphatidylinositol 4,5-bisphosphate]] (PIP<sub>2</sub>) into two second messengers, [[inositol trisphosphate]] (IP<sub>3</sub>) and [[diacylglycerol]] (DAG). IP<sub>3</sub> induces calcium release from the [[endoplasmic reticulum]]. DAG activates [[protein kinase C]].
The Inositol Phospholipid Dependent Pathway is used as a signal transduction pathway for many hormones including:
* Epinephrine
* ADH ([[Vasopressin]]/AVP) – Induces the synthesis and release of [[glucocorticoid]]s ([[Zona fasciculata]] of [[adrenal cortex]]); Induces vasoconstriction (V1 Cells of [[Posterior pituitary]])
* [[Thyrotropin-releasing hormone|TRH]] – Induces the synthesis and release of TSH ([[Anterior pituitary gland]])
* TSH – Induces the synthesis and release of a small amount of T4 ([[Thyroid Gland]])
* [[Angiotensin#Angiotensin II|Angiotensin II]] – Induces Aldosterone synthesis and release ([[zona glomerulosa]] of adrenal cortex in kidney)
* [[Gonadotropin-releasing hormone|GnRH]] – Induces the synthesis and release of FSH and LH (Anterior Pituitary)

=====G<sub>α12/13</sub>=====
*'''[[G12/G13 alpha subunits|G<sub>α12/13</sub>]]''' are involved in Rho family GTPase signaling (see [[Rho family of GTPases]]).  This is through the RhoGEF superfamily involving the [[RhoGEF domain]] of the proteins' structures). These are involved in control of cell cytoskeleton remodeling, and thus in regulating cell migration.

=====G<sub>β</sub>, G<sub>γ</sub>=====
*The '''[[Beta-gamma complex|G<sub>βγ</sub>]]''' complexes sometimes also have active functions. Examples include coupling to and activating [[G protein-coupled inwardly-rectifying potassium channel]]s.