Locust retinoid X receptors: 9-Cis-retinoic acid in embryos from a primitive insect.

The retinoid X receptor (RXR) is activated by its often elusive cognate ligand, 9-cis-retinoic acid (9-cis-RA). In flies and moths, molting is mediated by a heterodimer ecdysone receptor consisting of the ecdysone monomer (EcR) and an RXR homolog, ultraspiracle (USP); the latter is believed to have diverged from its RXR origin. In the more primitive insect, Locusta migratoria (Lm), RXR is more similar to human RXRs than to USPs.

HPLC-MS/MS analysis of the products generated from all-trans-retinoic acid using recombinant human CYP26A.

Two mammalian hCYP26A expression systems have been used to analyze the metabolic products of CYP26A. Through the use of extensive HPLC, UV spectroscopy, and liquid chromatography/tandem mass spectrometry (LC-MS/MS) methodology, we have conclusively demonstrated that the complex mixture of products comprises 4-OH-all-trans-retinoic acid, 4-oxo-all-trans-retinoic acid, and 18-OH-all-trans-retinoic acid, and more polar products, partially identified as dihydroxy and mono-oxo, mono-hydroxy derivatives. These more polar products are presumed to result from multiple hydroxylations on the beta-ionone ring.