The Retinoid X receptor-beta (RXR beta) is a nuclear hormone receptor and can function as a ligand inducible transcription factor capable of acting as a co-repressor and/or co-activator for gene expression. Nuclear receptors contain a series of conserved domains or regions. These domains/regions include a variable NH2-domain (A/B region), a conserved DNA-binding domain (DBD or region C), a linker region (region D), a ligand binding domain (LBD or region E), and in some receptors a variable COOH-terminal (region F). RXR beta belongs to the family of retinoid x receptors, one of two retinoic receptor families (retinoic acid receptors and retinoid x receptors). RXR beta is one of three members of the RXR family which consists of RXR alpha, RXR beta, and RXR gamma. The A/B and D regions of RXR beta are involved in dictating the cell dependent transcriptional response. RXR receptors are able to form both homo- and heterodimers. RXR receptors have been reported to form heterodimers with TRs (thyroid hormone receptors), RXRs retinoic acid receptors), VDR (vitamin D receptor), PPARs (peroxisome proliferator activated receptors), LXRs (liver x receptors), and FXR (farnesoid x receptor). These heterodimers can be classified as permissive and nonpermissive heterodimers. Addition of an RXR agonist, such as 9-cis-retinoic acid, can result in transcriptional activity of permissive heterodimers while activation of nonpermissive heterodimers occurs independent of the RXR agonist. RXR agonist LG100268 activates the transcriptional response RXR:PPARγ and RXR:LXR heterodimers alone and synergistically with PPARγ and LXR agonists, but does not activate RXR:RXR and RXR:TR heterodimers whose activity is dependent upon RXR and TR agonists. RXR beta is widely expressed in almost every tissue. The generation of RXR beta null mice resulted in approximately 50% of the mice to die before birth and those that survived appear normal, except for male sterility.
The endogenous ligands for RXR beta include 9-cis-retinoic acid, phytanic acid, and docosahexaenoic acid. Synthetic agonists for RXR beta have been termed rexinoids and includes LG100268.