7axl
Crystal structure of the hPXR-LBD in complex with estradiol and heptachlor endo-epoxide
Structural highlights
FunctionNR1I2_HUMAN Nuclear receptor that binds and is activated by variety of endogenous and xenobiotic compounds. Transcription factor that activates the transcription of multiple genes involved in the metabolism and secretion of potentially harmful xenobiotics, drugs and endogenous compounds. Activated by the antibiotic rifampicin and various plant metabolites, such as hyperforin, guggulipid, colupulone, and isoflavones. Response to specific ligands is species-specific. Activated by naturally occurring steroids, such as pregnenolone and progesterone. Binds to a response element in the promoters of the CYP3A4 and ABCB1/MDR1 genes.[1] [2] [3] [4] [5] [6] Publication Abstract from PubMedHumans are chronically exposed to mixtures of xenobiotics referred to as endocrine-disrupting chemicals (EDCs). A vast body of literature links exposure to these chemicals with increased incidences of reproductive, metabolic, or neurological disorders. Moreover, recent data demonstrate that, when used in combination, chemicals have outcomes that cannot be predicted from their individual behavior. In its heterodimeric form with the retinoid X receptor (RXR), the pregnane X receptor (PXR) plays an essential role in controlling the mammalian xenobiotic response and mediates both beneficial and detrimental effects. Our previous work shed light on a mechanism by which a binary mixture of xenobiotics activates PXR in a synergistic fashion. Structural analysis revealed that mutual stabilization of the compounds within the ligand-binding pocket of PXR accounts for the enhancement of their binding affinity. In order to identify and characterize additional active mixtures, we combined a set of cell-based, biophysical, structural, and in vivo approaches. Our study reveals features that confirm the binding promiscuity of this receptor and its ability to accommodate bipartite ligands. We reveal previously unidentified binding mechanisms involving dynamic structural transitions and covalent coupling and report four binary mixtures eliciting graded synergistic activities. Last, we demonstrate that the robust activity obtained with two synergizing PXR ligands can be enhanced further in the presence of RXR environmental ligands. Our study reveals insights as to how low-dose EDC mixtures may alter physiology through interaction with RXR-PXR and potentially several other nuclear receptor heterodimers. Mechanistic insights into the synergistic activation of the RXR-PXR heterodimer by endocrine disruptor mixtures.,Delfosse V, Huet T, Harrus D, Granell M, Bourguet M, Gardia-Parege C, Chiavarina B, Grimaldi M, Le Mevel S, Blanc P, Huang D, Gruszczyk J, Demeneix B, Cianferani S, Fini JB, Balaguer P, Bourguet W Proc Natl Acad Sci U S A. 2021 Jan 5;118(1). pii: 2020551118. doi:, 10.1073/pnas.2020551118. PMID:33361153[7] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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