G protein-coupled receptor adaptation mechanisms.

G protein-coupled receptors (GPCRs) transduce extracellular signals that modulate the activity of a wide variety of biological processes, such as neurotransmission, chemoattraction, cardiac function, olfaction, and vision. However, GPCR signalling desensitizes rapidly as the consequence of receptor phosphorylation. G protein-coupled receptor kinase-mediated receptor phosphorylation promotes the binding of beta-arrestin proteins, which not only uncouple GPCRs from their cognate heterotrimeric G protein, but also target them for endocytosis. The sequestration (endocytosis) of desensitized GPCRs to endosomes is required for their dephosphorylation and subsequent resensitization to their pre-ligand exposed state. This review concentrates on the mechanisms underlying GPCR desensitization and resensitization.