Intracellular domains, serotonin

The majority of the studies examining the phosphorylation of serotonin receptors have emphasized its role on receptor desensitization. A general mechanism of G protein-coupled receptor desensitization involves phosphorylation of the intracellular domains of the receptor by second-messenger kinases such as protein kinase A (PKA) or C (PKC) and specific G protein-coupled receptor kinases, that lead to the binding of arrestins to the receptor and G protein uncoupling (149,150). The mechanisms have been best elucidated for the P-adreneigic receptors, where desensitization is mediated by both PARK and PKA (151). However, mechanisms underlying desensitization of serotonin... 

Many different receptor types are coupled to G proteins, including receptors for norepinephrine and epinephrine (a- and p-adrenoceptors), 5-hydroxytrypta-mine (serotonin or 5-HT receptors), and muscarinic acetylcholine receptors. Figure 2.1 presents the structure of one of these, the uz-adrenoceptor from the human kidney. All members of this family of G protein-coupled receptors are characterized by having seven membrane-enclosed domains plus extracellular and intracellular loops. The specific binding sites for agonists occur at the extracellular surface, while the interaction with G proteins occurs with the intracellular portions of the receptor. The general term for any chain of events initiated by receptor activation is signal transduction. 

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