Editing G protein-coupled receptor (section)

====Gα signaling====

# The effector of both the G<sub>αs</sub> and G<sub>αi/o</sub> pathways is the [[cyclic amp|cyclic-adenosine monophosphate]] (cAMP)-generating enzyme [[adenylyl cyclase|adenylate cyclase]], or AC. While there are ten different AC gene products in mammals, each with subtle differences in [[tissue (biology)|tissue]] distribution or function, all [[catalyze]] the conversion of [[cytosolic]] [[adenosine triphosphate]] (ATP) to cAMP, and all are directly stimulated by G-proteins of the G<sub>αs</sub> class. In contrast, however, interaction with Gα subunits of the G<sub>αi/o</sub> type inhibits AC from generating cAMP. Thus, a GPCR coupled to G<sub>αs</sub> counteracts the actions of a GPCR coupled to G<sub>αi/o</sub>, and vice versa. The level of cytosolic cAMP may then determine the activity of various [[cyclic nucleotide-gated ion channel|ion channels]] as well as members of the [[Serine/threonine-specific protein kinase|ser/thr-specific]] [[protein kinase A|protein kinase&nbsp;A]] (PKA) family. Thus cAMP is considered a [[second messenger system|second messenger]] and PKA a secondary [[effector (biology)|effector]].
# The effector of the G<sub>αq/11</sub> pathway is [[phospholipase C|phospholipase C-β]] (PLCβ), which catalyzes the cleavage of membrane-bound [[phosphatidylinositol 4,5-bisphosphate]] (PIP2) into the second messengers [[inositol trisphosphate|inositol (1,4,5) trisphosphate]] (IP3) and [[diglyceride|diacylglycerol]] (DAG). IP3 acts on [[inositol trisphosphate receptor|IP3 receptors]] found in the membrane of the [[endoplasmic reticulum]] (ER) to elicit [[Ca2+|Ca<sup>2+</sup>]] release from the ER, while DAG diffuses along the [[plasma membrane]] where it may activate any membrane localized forms of a second ser/thr kinase called [[protein kinase C]] (PKC). Since many isoforms of PKC are also activated by increases in intracellular Ca<sup>2+</sup>, both these pathways can also converge on each other to signal through the same secondary effector. Elevated intracellular Ca<sup>2+</sup> also binds and [[allosterically]] activates proteins called [[calmodulin]]s, which in turn tosolic [[small GTPase]], [[Rho family of GTPases|Rho]]. Once bound to GTP, Rho can then go on to activate various proteins responsible for [[cytoskeleton]] regulation such as [[Rho-associated protein kinase|Rho-kinase]] (ROCK). Most GPCRs that couple to G<sub>α12/13</sub> also couple to other sub-classes, often G<sub>αq/11</sub>.