Orexin receptor: Difference between revisions

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Both [[orexin]] receptors exhibit a similar pharmacology - the 2 orexin peptides, [[orexin-A]] and [[orexin B|orexin-B]], bind to both [[Receptor (biochemistry)|receptors]] and, in each case, [[agonist]] [[Binding (molecular)|binding]] results in an increase in [[intracellular]] [[calcium]] levels. However, orexin-B shows a 10-fold selectivity for [[Hypocretin (orexin) receptor 2|orexin receptor type 2]], whilst orexin-A is [[equipotent]] at both receptors.<ref name="pmid10498827">{{cite journal |vauthors=Smart D, Jerman JC, Brough SJ, Rushton SL, Murdock PR, Jewitt F, Elshourbagy NA, Ellis CE, Middlemiss DN, Brown F | title = Characterization of recombinant human orexin receptor pharmacology in a Chinese hamster ovary cell-line using FLIPR | journal = Br. J. Pharmacol. | volume = 128 | issue = 1 | pages = 1–3 |date=September 1999 | pmid = 10498827 | pmc = 1571615 | doi = 10.1038/sj.bjp.0702780 | url = }}</ref>
Both [[orexin]] receptors exhibit a similar pharmacology - the 2 orexin peptides, [[orexin-A]] and [[orexin B|orexin-B]], bind to both [[Receptor (biochemistry)|receptors]] and, in each case, [[agonist]] [[Binding (molecular)|binding]] results in an increase in [[intracellular]] [[calcium]] levels. However, orexin-B shows a 10-fold selectivity for [[Hypocretin (orexin) receptor 2|orexin receptor type 2]], whilst orexin-A is [[equipotent]] at both receptors.<ref name="pmid10498827">{{cite journal |vauthors=Smart D, Jerman JC, Brough SJ, Rushton SL, Murdock PR, Jewitt F, Elshourbagy NA, Ellis CE, Middlemiss DN, Brown F | title = Characterization of recombinant human orexin receptor pharmacology in a Chinese hamster ovary cell-line using FLIPR | journal = Br. J. Pharmacol. | volume = 128 | issue = 1 | pages = 1–3 |date=September 1999 | pmid = 10498827 | pmc = 1571615 | doi = 10.1038/sj.bjp.0702780 | url = }}</ref>


Several [[orexin receptor antagonist]]s are in development for potential use in sleep disorders. Only the crystal structure of OX2 is known.<ref name="nature">{{cite journal |vauthors=Yin J, Mobarec JC, Kolb P, Rosenbaum DM | title = Crystal Structure of the Human Ox2 Orexin Receptor Bound to the Insomnia Drug Suvorexant | journal = Nature | volume =  519| issue =  | pages = 247–250|date=December 2014 | pmid =  25533960| pmc = | doi = 10.1038/nature14035 | url = }}</ref>
Several [[orexin receptor antagonist]]s are in development for potential use in sleep disorders.<ref name="nature">{{cite journal |vauthors=Yin J, Mobarec JC, Kolb P, Rosenbaum DM | title = Crystal Structure of the Human Ox2 Orexin Receptor Bound to the Insomnia Drug Suvorexant | journal = Nature | volume =  519| issue =  | pages = 247–250|date=December 2014 | pmid =  25533960| pmc = | doi = 10.1038/nature14035 | url = }}</ref>


== Synthetic ligands ==
== Synthetic ligands ==


Several drugs<ref name=Heifetz_2012>{{cite journal |vauthors=Heifetz A, Morris GB, Biggin PC, Barker O, Fryatt T, Bentley J, Hallett D, Manikowski DP, Pal S, Reifegerste R, Slack M, Law R |title=Study of Human Orexin-1 and -2 G-Protein-Coupled Receptors with Novel and Published Antagonists by Modeling, Molecular Dynamics Simulations, and Site-Directed Mutagenesis | journal = Biochemistry | year=2012 | volume = 51 | issue = 15 | pages = 3178–3197 | doi = 10.1021/bi300136h | pmid=22448975}}</ref> acting on the orexin system are under development, either orexin agonists for the treatment of conditions such as [[narcolepsy]], or orexin antagonists for [[insomnia]]. No [[neuropeptide]] agonists are yet available, although synthetic Orexin-A polypeptide has been made available as a nasal spray and tested on monkeys. One non-peptide antagonist is currently available in the U.S., [[Merck & Co.|Merck's]] [[suvorexant]] (Belsomra),;<ref name=Baxter_2011>{{cite journal |vauthors=Baxter CA, Cleator ED, Karel MJ, Edwards JS, Reamer RA, Sheen FJ, Stewart GW, Strotman NA, Wallace DJ | title = The First Large-Scale Synthesis of MK-4305: A Dual Orexin Receptor Antagonist for the Treatment of Sleep Disorder | journal = Organic Process Research & Development | year = 2011 | volume = 15 | issue = 2 | pages = 367–375 | doi = 10.1021/op1002853}}</ref> two additional agents are in development: [[SB-649,868|SB-649,868 by]] [[GlaxoSmithKline]], for sleep disorders, and ACT-462206, currently in human clinical trials.<ref>{{Cite journal|url = |title = Entry-into-humans study with ACT-462206, a novel dual orexin receptor antagonist, comparing its pharmacodynamics with almorexant|date = Sep 2014|journal = J Clin Pharmacol.|accessdate = |doi = 10.1002/jcph.297|pmid = 24691844 |volume=54 |pages=979–86 |vauthors=Hoch M, van Gorsel H, van Gerven J, Dingemanse J}}</ref> Another drug in development, [[almorexant]] (ACT-078573) by [[Actelion]], was abandoned due to adverse effects.
Several drugs<ref name=Heifetz_2012>{{cite journal |vauthors=Heifetz A, Morris GB, Biggin PC, Barker O, Fryatt T, Bentley J, Hallett D, Manikowski DP, Pal S, Reifegerste R, Slack M, Law R |title=Study of Human Orexin-1 and -2 G-Protein-Coupled Receptors with Novel and Published Antagonists by Modeling, Molecular Dynamics Simulations, and Site-Directed Mutagenesis | journal = Biochemistry | year=2012 | volume = 51 | issue = 15 | pages = 3178–3197 | doi = 10.1021/bi300136h | pmid=22448975}}</ref> acting on the orexin system are under development, either orexin agonists for the treatment of conditions such as [[narcolepsy]], or orexin antagonists for [[insomnia]]. No [[neuropeptide]] agonists are yet available, although synthetic Orexin-A polypeptide has been made available as a nasal spray and tested on monkeys. One non-peptide antagonist is currently available in the U.S., [[Merck & Co.|Merck's]] [[suvorexant]] (Belsomra),;<ref name=Baxter_2011>{{cite journal |vauthors=Baxter CA, Cleator ED, Karel MJ, Edwards JS, Reamer RA, Sheen FJ, Stewart GW, Strotman NA, Wallace DJ | title = The First Large-Scale Synthesis of MK-4305: A Dual Orexin Receptor Antagonist for the Treatment of Sleep Disorder | journal = Organic Process Research & Development | year = 2011 | volume = 15 | issue = 2 | pages = 367–375 | doi = 10.1021/op1002853}}</ref> two additional agents are in development: [[SB-649,868|SB-649,868 by]] [[GlaxoSmithKline]], for sleep disorders, and ACT-462206, currently in human clinical trials.<ref>{{Cite journal|url = |title = Entry-into-humans study with ACT-462206, a novel dual orexin receptor antagonist, comparing its pharmacodynamics with almorexant|date = Sep 2014|journal = J Clin Pharmacol|accessdate = |doi = 10.1002/jcph.297|pmid = 24691844 |volume=54 |pages=979–86 |vauthors=Hoch M, van Gorsel H, van Gerven J, Dingemanse J}}</ref> Another drug in development, [[almorexant]] (ACT-078573) by [[Actelion]], was abandoned due to adverse effects.


Most ligands acting on the orexin system so far are polypeptides modified from the endogenous agonists Orexin-A and Orexin-B, however there are some subtype-selective non-peptide antagonists available for research purposes.
Most ligands acting on the orexin system so far are polypeptides modified from the endogenous agonists Orexin-A and Orexin-B, however there are some subtype-selective non-peptide antagonists available for research purposes.
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* [[RTIOX-276]] – selective OX<sub>1</sub> antagonist
* [[RTIOX-276]] – selective OX<sub>1</sub> antagonist


==References==
== References ==
<references/>
 
{{reflist | 30em}}


==External links==
==External links==
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[[Category:Protein families]]
[[Category:Protein families]]
[[Category:G protein coupled receptors]]
[[Category:G protein-coupled receptors]]
[[Category:Orexin antagonists]]
[[Category:Orexin antagonists]]




{{transmembranereceptor-stub}}
{{transmembranereceptor-stub}}

Latest revision as of 23:05, 28 October 2018

hypocretin (orexin) receptor 1
Identifiers
SymbolHCRTR1
Entrez3061
HUGO4848
OMIM602392
RefSeqNM_001525
UniProtO43613
Other data
LocusChr. 1 p33
hypocretin (orexin) receptor 2
Identifiers
SymbolHCRTR2
Entrez3062
HUGO4849
OMIM602393
RefSeqNM_001526
UniProtO43614
Other data
LocusChr. 6 p11-q11
Orexin receptor type 2
Identifiers
SymbolOrexin_rec2
PfamPF03827
InterProIPR004060

The orexin receptor (also referred to as the hypocretin receptor) is a G-protein-coupled receptor that binds the neuropeptide orexin. There are two variants, OX1 and OX2, each encoded by a different gene (HCRTR1, HCRTR2).[1]

Both orexin receptors exhibit a similar pharmacology - the 2 orexin peptides, orexin-A and orexin-B, bind to both receptors and, in each case, agonist binding results in an increase in intracellular calcium levels. However, orexin-B shows a 10-fold selectivity for orexin receptor type 2, whilst orexin-A is equipotent at both receptors.[2]

Several orexin receptor antagonists are in development for potential use in sleep disorders.[3]

Synthetic ligands

Several drugs[4] acting on the orexin system are under development, either orexin agonists for the treatment of conditions such as narcolepsy, or orexin antagonists for insomnia. No neuropeptide agonists are yet available, although synthetic Orexin-A polypeptide has been made available as a nasal spray and tested on monkeys. One non-peptide antagonist is currently available in the U.S., Merck's suvorexant (Belsomra),;[5] two additional agents are in development: SB-649,868 by GlaxoSmithKline, for sleep disorders, and ACT-462206, currently in human clinical trials.[6] Another drug in development, almorexant (ACT-078573) by Actelion, was abandoned due to adverse effects.

Most ligands acting on the orexin system so far are polypeptides modified from the endogenous agonists Orexin-A and Orexin-B, however there are some subtype-selective non-peptide antagonists available for research purposes.

  • SB-334,867 – selective OX1 antagonist
  • SB-408,124 – selective OX1 antagonist
  • TCS-OX2-29 – selective OX2 antagonist
  • EMPA (N-Ethyl-2-[(6-methoxy-pyridin-3-yl)-(toluene-2-sulfonyl)-amino]-N-pyridin-3-ylmethyl-acetamide) – selective OX2 antagonist
  • RTIOX-276 – selective OX1 antagonist

References

  1. Spinazzi R, Andreis PG, Rossi GP, Nussdorfer GG (2006). "Orexins in the regulation of the hypothalamic-pituitary-adrenal axis". Pharmacol. Rev. 58 (1): 46–57. doi:10.1124/pr.58.1.4. PMID 16507882.
  2. Smart D, Jerman JC, Brough SJ, Rushton SL, Murdock PR, Jewitt F, Elshourbagy NA, Ellis CE, Middlemiss DN, Brown F (September 1999). "Characterization of recombinant human orexin receptor pharmacology in a Chinese hamster ovary cell-line using FLIPR". Br. J. Pharmacol. 128 (1): 1–3. doi:10.1038/sj.bjp.0702780. PMC 1571615. PMID 10498827.
  3. Yin J, Mobarec JC, Kolb P, Rosenbaum DM (December 2014). "Crystal Structure of the Human Ox2 Orexin Receptor Bound to the Insomnia Drug Suvorexant". Nature. 519: 247–250. doi:10.1038/nature14035. PMID 25533960.
  4. Heifetz A, Morris GB, Biggin PC, Barker O, Fryatt T, Bentley J, Hallett D, Manikowski DP, Pal S, Reifegerste R, Slack M, Law R (2012). "Study of Human Orexin-1 and -2 G-Protein-Coupled Receptors with Novel and Published Antagonists by Modeling, Molecular Dynamics Simulations, and Site-Directed Mutagenesis". Biochemistry. 51 (15): 3178–3197. doi:10.1021/bi300136h. PMID 22448975.
  5. Baxter CA, Cleator ED, Karel MJ, Edwards JS, Reamer RA, Sheen FJ, Stewart GW, Strotman NA, Wallace DJ (2011). "The First Large-Scale Synthesis of MK-4305: A Dual Orexin Receptor Antagonist for the Treatment of Sleep Disorder". Organic Process Research & Development. 15 (2): 367–375. doi:10.1021/op1002853.
  6. Hoch M, van Gorsel H, van Gerven J, Dingemanse J (Sep 2014). "Entry-into-humans study with ACT-462206, a novel dual orexin receptor antagonist, comparing its pharmacodynamics with almorexant". J Clin Pharmacol. 54: 979–86. doi:10.1002/jcph.297. PMID 24691844.

External links

This article incorporates text from the public domain Pfam and InterPro: IPR004060