Melatonin receptor 1A/1B (IPR002278)

Short name: Mel_1A/1B_rcpt

Overlapping homologous superfamilies


Family relationships


Melatonin is a naturally occurring compound found in animals, plants, and microbes [PMID: 15206778, PMID: 19033551]. In animals melatonin is secreted by the pineal gland during darkness [PMID: 1649044, PMID: 17901231]. It regulates a variety of neuroendocrine functions and is thought to play an essential role in circadian rhythms [PMID: 17298593]. Drugs that modify the action of melatonin, and hence influence circadian cycles, are of clinical interest for example, in the treatment of jet-lag [PMID: 16473858].

Many of the biological effects of melatonin are produced through the activation of melatonin receptors [PMID: 15992934], which are members of rhodopsin-like G protein-coupled receptor family. There are three melatonin receptor subtypes. Melatonin receptor type 1A and melatonin receptor type 1B are present in humans and other mammals [PMID: 8936344] while melatonin receptor type 1C has been identified in amphibia and birds [PMID: 15357831]. There is also a closely-related orphan receptor, termed melatonin-related receptor type 1X (also known as GPR50) [PMID: 9933574], is yet to achieve receptor status from the International Union of Basic and Clinical Pharmacology (IUPHAR), since a robust response mediated via the protein has not been reported in the literature. Melatonin receptor type 1C receptors are 80% identical and are distinct from 1A and 1B subtypes. Similar ligand binding and functional characteristics are observed in expressed 1A and 1C receptors. The melatonin receptors inhibit adenylyl cyclase via a pertussis-toxin-sensitive G-protein, probably of the Gi/Go class.

Melatonin receptor 1A, also known as MT1 melatonin receptor [PMID: 20605968], mediates the circadian and reproductive effects of the hormone melatonin. Melatonin receptor 1A is expressed in the hypothalamic suprachiasmatic nuclei and hypophyseal pars tuberalis [PMID: 9051762, PMID: 11836530, PMID: 8804720].

Melatonin receptor type 1B is found primarily in the retina, selected brain regions and some arterial beds [PMID: 9247266, PMID: 9737724, PMID: 7568007, PMID: 15617532, PMID: 14987948, PMID: 15620576]. Activation of human recombinant melatonin receptor 1B inhibits the adenylyl cyclase pathway and cyclic guanosine monophosphate formation [PMID: 7946354, PMID: 7568007, PMID: 10413300]. It is thought to participate in the circadian timing system [PMID: 9247266], inhibition of dopamine release in the retina [PMID: 9089668], and in vasodilation of the caudal artery [PMID: 12183692, PMID: 9593596].

GO terms

Biological Process

GO:0007186 G-protein coupled receptor signaling pathway

Molecular Function

GO:0008502 melatonin receptor activity

Cellular Component

GO:0016021 integral component of membrane

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.