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serotonin receptor subtype 6, member of the class A family of seven-transmembrane G protein-coupled receptors The 5-HT6 receptors are a subfamily of serotonin receptors that bind the neurotransmitter serotonin (5HT; 5-hydroxytryptamine) in the mammalian central nervous system (CNS). 5-HT6 receptors are selectively linked to G proteins of the G(s) family, which positively stimulate adenylate cyclase, causing cAMP formation and activation of protein kinase A. The 5-HT6 receptors mediates excitatory neurotransmission and are involved in learning and memory; thus they are promising targets for the treatment of cognitive impairment. All GPCRs have a common structural architecture comprising of seven-transmembrane (TM) alpha-helices interconnected by three extracellular and three intracellular loops. A general feature of GPCR signaling is agonist-induced conformational changes in the receptors, leading to activation of the heterotrimeric G proteins, which consist of the guanine nucleotide-binding G-alpha subunit and the dimeric G-beta-gamma subunits. The activated G proteins then bind to and activate numerous downstream effector proteins, which generate second messengers that mediate a broad range of cellular and physiological processes.
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