serotonin receptor subtype 2 from insects, member of the class A family of seven-transmembrane G protein-coupled receptors
The 5-HT2 receptors are a subfamily of serotonin receptors that bind the neurotransmitter serotonin (5HT; 5-hydroxytryptamine) in the central nervous system (CNS). The 5-HT2 subfamily is composed of three subtypes that mediate excitatory neurotransmission: 5-HT2A, 5-HT2B, and 5-HT2C. They are selectively linked to G proteins of the G(q/11) family and activate phospholipase C, which leads to activation of protein kinase C and calcium release. In the CNS, serotonin is involved in the regulation of appetite, mood, sleep, cognition, learning and memory, as well as implicated in diseases such as migraine, schizophrenia, and depression. Indeed, 5-HT2 receptors are attractive targets for a variety of psychoactive drugs, ranging from atypical antipsychotic drugs, antidepressants, and anxiolytics, which have an antagonistic action on 5-HT2 receptors, to hallucinogens, which act as agonists at postsynaptic 5-HT2 receptors. 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.