Melatonin receptors C
Unless otherwise stated all data on this page refer to the human proteins. Gene information is provided for human (Hs), mouse (Mm) and rat (Rn).
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Melatonin receptors (nomenclature as agreed by the NC-IUPHAR Subcommittee on Melatonin Receptors [6]) are activated by the endogenous ligands melatonin and clinically used drugs like ramelteon, agomelatine and tasimelteon.
Receptors
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MT1 receptor
C
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MT2 receptor
C
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Concise Guide to PHARMACOLOGY citation:
Alexander SP, Christopoulos A, Davenport AP, Kelly E, Mathie A, Peters JA, Veale EL et al. (2021) THE CONCISE GUIDE TO PHARMACOLOGY 2021/22: G protein-coupled receptors. Br J Pharmacol. 176 Suppl 1:S27-S156.
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Melatonin, 2-iodo-melatonin, agomelatine, GR 196429, LY 156735 and ramelteon [14] are nonselective agonists for MT1 and MT2 receptors. (-)-AMMTC displays an ~400-fold greater agonist potency than (+)-AMMTC at rat MT1 receptors (see AMMTC for structure) [26]. Luzindole is an MT1/MT2 non-selective competitive melatonin receptor antagonist with about 15-25 fold selectivity for the MT2 receptor [8]. MT1/MT2 heterodimers present different pharmacological profiles from MT1 and MT2 receptors [2].
The MT3 binding site of hamster brain and peripheral tissues such as kidney and testis, also termed the ML2 receptor, binds selectively 2-iodo-[125I]5MCA-NAT [17]. Pharmacological investigations of MT3 binding sites have primarily been conducted in hamster tissues. At this site, The endogenous ligand N-acetylserotonin [10,16-17,20] and 5MCA-NAT [20] appear to function as agonists, while prazosin [16] functions as an antagonist. The MT3 binding site of hamster kidney was also identified as the hamster homologue of human quinone reductase 2 (NQO2, P16083 [18-19]). The MT3 binding site activated by 5MCA-NAT in eye ciliary body is positively coupled to adenylyl cyclase and regulates chloride secretion [12]. Xenopus melanophores and chick brain express a distinct receptor (x420, P49219; c346, P49288, initially termed Mel1C) coupled to the Gi/o family of G proteins, for which GPR50 has recently been suggested to be a mammalian counterpart [9] although melatonin does not bind to GPR50 receptors. Several variants of the MTNR1B gene have been associated with increased type 2 diabetes risk [13].