View source for Melatonin receptor

{{infobox protein
| Name = [[melatonin receptor 1A]]
| caption = 
| image = 
| width = 
| HGNCid = 7463
| Symbol = MTNR1A
| AltSymbols = 
| EntrezGene = 4543
| OMIM = 600665
| RefSeq = NM_005958
| UniProt = P48039
| PDB = 
| ECnumber = 
| Chromosome = 4
| Arm = q
| Band = 35.1
| LocusSupplementaryData = 
}}
{{infobox protein
| Name = [[melatonin receptor 1B]]
| caption = 
| image = 
| width = 
| HGNCid = 7464
| Symbol = MTNR1B
| AltSymbols = 
| EntrezGene = 4544
| OMIM = 600804
| RefSeq = NM_005959
| UniProt = P49286
| PDB = 
| ECnumber = 
| Chromosome = 11
| Arm = q
| Band = 21
| LocusSupplementaryData = -q22
}}
A '''melatonin receptor''' is a [[G protein-coupled receptor]] (GPCR) which binds [[melatonin]].<ref name="pmid9406026">{{cite journal | author = Reppert SM | title = Melatonin receptors: molecular biology of a new family of G protein-coupled receptors | journal = J. Biol. Rhythms | volume = 12 | issue = 6 | pages = 528–31 | year = 1997 | pmid = 9406026 | doi = 10.1177/074873049701200606 }}</ref>

Three types of melatonin receptors have been [[cloned]]. The MT<sub>1</sub> (or [[melatonin receptor 1A|Mel<sub>1A</sub>]] or MTNR1A) and MT<sub>2</sub> (or [[melatonin receptor 1B|Mel<sub>1B</sub>]] or MTNR1B) receptor subtypes are present in [[human]]s and other [[mammal]]s,<ref name="pmid8936344">{{cite journal |vauthors=Reppert SM, Weaver DR, Godson C | title = Melatonin receptors step into the light: cloning and classification of subtypes | journal = Trends Pharmacol. Sci. | volume = 17 | issue = 3 | pages = 100–02 | year = 1996 | pmid = 8936344 | doi = 10.1016/0165-6147(96)10005-5 }}</ref> while an additional melatonin receptor subtype MT<sub>3</sub> (or [[melatonin receptor 1C|Mel<sub>1C</sub>]] or MTNR1C) has been identified in [[amphibia]] and [[bird]]s.<ref name="Sugden_2004">{{cite journal |vauthors=Sugden D, Davidson K, Hough KA, Teh MT | title = Melatonin, melatonin receptors and melanophores: a moving story | journal = Pigment Cell Res. | volume = 17 | issue = 5 | pages = 454–60 | year = 2004 | pmid = 15357831 | doi = 10.1111/j.1600-0749.2004.00185.x }}</ref>

==Expression patterns==
In mammals, melatonin receptors are found in the [[brain]] and some peripheral organs. However, there is considerable variation in the density and location of MT receptor expression between species.<ref name="pmid8161940">{{cite journal |vauthors=Morgan PJ, Barrett P, Howell HE, Helliwell R | title = Melatonin receptors: localization, molecular pharmacology and physiological significance | journal = Neurochem. Int. | volume = 24 | issue = 2 | pages = 101–46 | year = 1994 | pmid = 8161940 | doi = 10.1016/0197-0186(94)90100-7 }}</ref>

===MT<sub>1</sub>===
In humans, The MT<sub>1</sub> subtype is expressed in the [[pars tuberalis]] of the [[pituitary gland]], the retina and the [[suprachiasmatic nuclei]] of the [[hypothalamus]].

===MT<sub>2</sub>===
The MT<sub>2</sub> subtype is expressed in the [[retina]]. MT<sub>2</sub> receptor mRNA has not been detected by in situ hybridization in the rat suprachiasmatic nucleus or pars tuberalis.<ref name="Reppert_1995">{{cite journal |vauthors=Reppert SM, Godson C, Mahle CD, Weaver DR, Slaugenhaupt SA, Gusella JF | title = Molecular characterization of a second melatonin receptor expressed in human retina and brain: the Mel1b melatonin receptor | journal = Proc. Natl. Acad. Sci. U.S.A. | volume = 92 | issue = 19 | pages = 8734–38 |date=September 1995  | pmid = 7568007 | pmc = 41041 | doi =  10.1073/pnas.92.19.8734| bibcode = 1995PNAS...92.8734R }}</ref>

===MT<sub>3</sub>===
The MT<sub>3</sub> subtype of many non-mammalian vertebrates is expressed in various brain areas.<ref name= Sugden_2004/>

==MT Receptor function==

===MT<sub>1</sub>===
In humans, The MT<sub>1</sub> subtype's expression in the pars tuberalis of the pituitary gland and suprachiasmatic nuclei of the hypothalamus is indicative of melatonin's circadian and reproductive functional involvement.

===MT<sub>2</sub>===
In humans, the MT<sub>2</sub> subtype's expression in the retina is suggestive of melatonin's effect on the mammalian retina occurring through this receptor. Research suggests that melatonin acts to inhibit the Ca2+-dependent release of dopamine.<ref name="Reppert_1995"/> Melatonin's action in the retina is believed to affect several light-dependent functions, including phagocytosis and photopigment disc shedding.<ref name="pmid6828862">{{cite journal |vauthors=Besharse JC, Dunis DA | title = Methoxyindoles and photoreceptor metabolism: activation of rod shedding | journal = Science | volume = 219 | issue = 4590 | pages = 1341–43 |date=March 1983  | pmid = 6828862 | doi =  10.1126/science.6828862| bibcode = 1983Sci...219.1341B }}</ref> In addition to retina this receptor is expressed on the osteoblasts and is increased upon their differentiation. MT2 regulates proliferation and differentiation of osteoblasts and regulates their function in depositing bone. <ref>{{cite journal |vauthors=Sharan K, Lewis K, Furukawa T, Yadav VK |title=Regulation of bone mass through pineal-derived melatonin-MT2 pathway |journal=[[J Pineal Res (journal)|J Pineal Res]] |pmid=28512916 |doi= 10.1002/jbm.a.30786}}</ref>
MT2 signaling seems  also involved in the pathogenesis of type 2 diabetes. 
MT3 binding sites are widely distributed in the brain, liver, heart, kidneys, and lungs.Recent findings from animal studies suggest possible roles in the regulation of intraocular pressure and in inflammatory responses in the microvasculature.(Abdulhadi.m)

==Selective Ligands==

===Agonists===
* [[6-Hydroxymelatonin]]
* [[Agomelatine]]
* [[GR-196,429]]
* [[Melatonin]]
* [[N-Acetylserotonin]]
* [[Piromelatine]] 
* [[Ramelteon]]
* [[Tasimelteon]]
* [[TIK-301|TIK-301 (LY-156,735)]]<ref name="pmid12405554">{{cite journal |vauthors=Nickelsen T, Samel A, Vejvoda M, Wenzel J, Smith B, Gerzer R | title = Chronobiotic effects of the melatonin agonist LY 156735 following a simulated 9h time shift: results of a placebo-controlled trial | journal = Chronobiol. Int. | volume = 19 | issue = 5 | pages = 915–36 |date=September 2002  | pmid = 12405554 | doi = 10.1081/cbi-120014108}}</ref>

===Antagonists===
* [[Afobazole]]
* [[Luzindole]]
* [[Prazosin]]

== See also ==
*[[Discovery and development of melatonin receptor agonists]]

==References==
{{Reflist|2}}

==External links==
* {{cite web | url = http://www.iuphar-db.org/GPCR/ChapterMenuForward?chapterID=1291 | title = Melatonin Receptors | work = IUPHAR Database of Receptors and Ion Channels | publisher = International Union of Basic and Clinical Pharmacology }}
* {{MeshName|Melatonin+Receptors}}

{{G protein-coupled receptors}}
{{Melatonergics}}


{{gene-11-stub}}