title: The discovery of 9-cis retinoic acid: a hormone that binds the retinoid-X receptor.
abstract: Two classes of nuclear receptors, the retinoic acid receptors (RARs) and the retinoid-X receptors (RXRs), mediate the physiologic activity of retinoids. The RXRs can form biologically active heterodimers with the RARs and with other nuclear receptors, including the vitamin-D, thyroid hormone, and peroxisome proliferator-activated receptors. Thus, the RXRs may play a pivotal role in modulating the action of other hormones or ligands. The RXRs were originally classified as orphan receptors whose cognate ligand was unknown until recently, when 9-cis retinoic acid (9-cis RA) was discovered to bind directly and activate this family of receptors. Since 9-cis RA also binds and activates the RARs, it is interesting to speculate that this natural ligand may regulate a broad range of physiologic processes by mediating transcriptional activity through both RAR- and RXR-linked pathways.
authors.affiliation: Department of Toxicology and Pathology, Hoffmann-La Roche, Nutley, NJ 07110, USA.
authors.forename: B F
authors.initials: BF
authors.lastname: Tate
authors.forename: A A
authors.initials: AA
authors.lastname: Levin
authors.forename: J F
authors.initials: JF
authors.lastname: Grippo