International Union of Pharmacology. LXVI. Orphan nuclear receptors

Pharmacol Rev. 2006 Dec;58(4):798-836. doi: 10.1124/pr.58.4.10.


Half of the members of the nuclear receptors superfamily are so-called "orphan" receptors because the identity of their ligand, if any, is unknown. Because of their important biological roles, the study of orphan receptors has attracted much attention recently and has resulted in rapid advances that have helped in the discovery of novel signaling pathways. In this review we present the main features of orphan receptors, discuss the structure of their ligand-binding domains and their biological functions. The paradoxical existence of a pharmacology of orphan receptors, a rapidly growing and innovative field, is highlighted.

Publication types

  • Review

MeSH terms

  • Animals
  • Binding Sites
  • Humans
  • Ligands
  • Mutation
  • Phylogeny
  • Protein Isoforms / genetics
  • Protein Isoforms / physiology
  • Receptors, Cytoplasmic and Nuclear / classification
  • Receptors, Cytoplasmic and Nuclear / genetics
  • Receptors, Cytoplasmic and Nuclear / physiology*
  • Signal Transduction*
  • Terminology as Topic


  • Ligands
  • Protein Isoforms
  • Receptors, Cytoplasmic and Nuclear