Editing G protein-coupled receptor (section)

===Phosphorylation by cAMP-dependent protein kinases===

Cyclic AMP-dependent protein kinases ([[protein kinase A]]) are activated by the signal chain coming from the G protein (that was activated by the receptor) via [[adenylate cyclase]] and [[cyclic AMP]] (cAMP). In a ''feedback mechanism'', these activated kinases phosphorylate the receptor. The longer the receptor remains active the more kinases are activated and the more receptors are phosphorylated. In [[beta-2 adrenergic receptor|β<sub>2</sub>-adrenoceptor]]s, this phosphorylation results in the switching of the coupling from the G<sub>s</sub> class of G-protein to the [[Gi alpha subunit|G<sub>i</sub>]] class.<ref name="pmid11053129">{{cite journal | vauthors = Chen-Izu Y, Xiao RP, Izu LT, Cheng H, Kuschel M, Spurgeon H, Lakatta EG | title = G(i)-dependent localization of beta(2)-adrenergic receptor signaling to L-type Ca(2+) channels | journal = Biophysical Journal | volume = 79 | issue = 5 | pages = 2547–56 | date = November 2000 | pmid = 11053129 | pmc = 1301137 | doi = 10.1016/S0006-3495(00)76495-2 | bibcode = 2000BpJ....79.2547C }}</ref> cAMP-dependent PKA mediated phosphorylation can cause heterologous desensitisation in receptors other than those activated.<ref name="pmid14744258">{{cite journal | vauthors = Tan CM, Brady AE, Nickols HH, Wang Q, Limbird LE | title = Membrane trafficking of G protein-coupled receptors | journal = Annual Review of Pharmacology and Toxicology | volume = 44 | issue = 1 | pages = 559–609 | year = 2004 | pmid = 14744258 | doi = 10.1146/annurev.pharmtox.44.101802.121558 }}</ref>