RT Journal Article SR Electronic T1 International Union of Pharmacology. LXVI. Orphan Nuclear Receptors JF Pharmacological Reviews JO Pharmacol Rev FD American Society for Pharmacology and Experimental Therapeutics SP 798 OP 836 DO 10.1124/pr.58.4.10 VO 58 IS 4 A1 Gérard Benoit A1 Austin Cooney A1 Vincent Giguere A1 Holly Ingraham A1 Mitch Lazar A1 George Muscat A1 Thomas Perlmann A1 Jean-Paul Renaud A1 John Schwabe A1 Frances Sladek A1 Ming-Jer Tsai A1 Vincent Laudet YR 2006 UL http://pharmrev.aspetjournals.org/content/58/4/798.abstract AB 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.