title: Reactivity profiles of ligands of mammalian retinoic acid receptors: a preliminary COREPA analysis.
abstract: Retinoic acid and associated derivatives comprise a class of endogenous hormones that bind to and activate different families of retinoic acid receptors (RARs, RXRs), and control many aspects of vertebrate development. Identification of potential RAR and RXR ligands is of interest both from a pharmaceutical and toxicological perspective. The recently developed COREPA (COmmon REactivity PAttern) algorithm was used to establish reactivity profiles for a limited data set of retinoid receptor ligands in terms of activation of three RARs (alpha, beta, gamma) and an RXR (alpha). Conformational analysis of a training set of retinoids and related analogues in terms of thermodynamic stability of conformers and rotational barriers showed that these chemicals tend to be quite flexible. This flexibility, and the observation that relatively small energy differences between conformers can result in significant variations in electronic structure, highlighted the necessity of considering all energetically reasonable conformers in defining common reactivity profiles. The derived reactivity patterns for three different subclasses of the RAR (alpha, beta, gamma) were similar in terms of their global electrophilicity (nucleophilicity) and steric parameters. However, the profile of active chemicals with respect to interaction with the RXR-alpha differed qualitatively from that of the RARs. Variations in reactivity profiles for the RAR versus RXR families would be consistent with established differences in their affinity for endogenous retinoids, likely reflecting functional differences in the receptors.
authors.affiliation: US Environmental Protection Agency, National Health and Environmental Effects Research Laboratory, Mid-Continent Ecology Division, Duluth, MN 55804, USA. ankley.gerald@epa.gov
authors.forename: G T
authors.initials: GT
authors.lastname: Ankley
authors.forename: O G
authors.initials: OG
authors.lastname: Mekenyan
authors.forename: V B
authors.initials: VB
authors.lastname: Kamenska
authors.forename: P K
authors.initials: PK
authors.lastname: Schmieder
authors.forename: S P
authors.initials: SP
authors.lastname: Bradbury
mesh_terms: D000465:Algorithms; D000818:Animals; D005544:Forecasting; D008024:Ligands; D008322:Mammals; D008962:Models, Theoretical; D018168:Receptors, Retinoic Acid / Q000502:physiology*; D013329:Structure-Activity Relationship; D014212:Tretinoin / Q000494:pharmacology
chemical_list: D008024:Ligands; D018168:Receptors, Retinoic Acid; D014212:Tretinoin