Encyclopedia of Molecular Pharmacology

2008 Edition
| Editors: Stefan Offermanns, Walter Rosenthal

Orphan Receptors

  • Hans‐Peter Nothacker
Reference work entry
DOI: https://doi.org/10.1007/978-3-540-38918-7_224

Synonyms

Orphan G protein‐coupled receptors; Orphan GPCRs; Orphan serpentine receptors; Orphan nuclear receptor

Definition

Orphan receptors are proteins that bind and are activated by hitherto unknown signaling molecules (called ligands, neurotransmitters, or hormones). However, they share structural components with identified receptors whose signaling molecules are already known. The physiological functions of orphan receptors are unidentified. The identification of the natural ligand of an orphan receptor holds the key to our understanding of its physiological role and potential as a drug target.

Basic Mechanism

Members of two structurally very distinct receptor families are termed orphan receptors. One is the family of the  nuclear receptors which are cytosolic proteins that upon ligand binding change their conformation, translocate to nuclear binding sites, and act as transcription factors to regulate the expression of other genes. The second group of receptor proteins is the  G...

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References

  1. 1.
    Nothacker HP, Reinscheid, RK, Civelli O (2001) From receptor to ligand. In: Stanford C, Horton R (eds) Receptors: Structure and function. CRC press, Oxford pp. 41–63Google Scholar
  2. 2.
    Wise A, Jupe SC, Rees S (2004). The identification of ligands at orphan G‐protein coupled receptors. Annu Rev Pharmacol Toxicol 44: 43–66PubMedCrossRefGoogle Scholar
  3. 3.
    Bjarnadottir TK, Gloriam DE, Hellstrand SH et al (2006) Comprehensive repertoire and phylogenetic analysis of the G protein‐coupled receptors in human and mouse. Genomics 88:263–273PubMedCrossRefGoogle Scholar
  4. 4.
    Civelli O, Saito Y, Wang Z et al (2006) Orphan GPCRs and their ligands. Pharmacol Ther 110:525–532PubMedCrossRefGoogle Scholar

Copyright information

© Springer-Verlag Berlin Heidelberg New York 2008

Authors and Affiliations

  • Hans‐Peter Nothacker
    • 1
  1. 1.Department of PharmacologyUniversity of California, IrvineCAUSA