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Amino acid substitutions in the aryl hydrocarbon receptor ligand binding domain reveal YH439 as an atypical AhR activator

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dc.contributor.authorWhelan, F.
dc.contributor.authorHao, N.
dc.contributor.authorFurness, S.
dc.contributor.authorWhitelaw, M.
dc.contributor.authorChapman-Smith, A.
dc.date.issued2010
dc.description.abstractThe aryl hydrocarbon receptor (AhR) is traditionally defined as a transcription factor activated by exogenous polyaromatic and halogenated aromatic hydrocarbon (PAH/HAH) ligands. Active AhR induces genes involved in xenobiotic metabolism, including cytochrome P4501A1, which function to metabolize activating ligands. However, recent studies implicate AhR in biological events that are apparently unrelated to the xenobiotic response, implying that endogenous activation mechanisms exist. Three AhR genes in zebrafish (Danio rerio) encode proteins that demonstrate differential activation in response to PAH/HAHs, with the nonresponsive drAhR1a having some sequence divergence from the PAH/HAH-responsive AhRs in the ligand binding domain (LBD). We used these differences to guide the mutagenesis of mouse AhR (mAhR), aiming to generate variants that functionally discriminate between activation mechanisms. We found substitution of histidine 285 in the LBD with tyrosine gave a receptor that could be activated by isopropyl-2-(1,3-dithietane-2-ylidene)-2-[N-(4-methylthiazol-2-yl)carbamoyl]acetate (YH439), a potential AhR ligand chemically distinct from classic PAH/HAH-type ligands, but prevented activation by both exogenous PAH/HAH ligands and the endogenous activation mimics of suspension culture and application of shear-stressed serum. The differential response of H285Y mAhR to YH439 suggests that this activator has a novel mode of interaction that tolerates tyrosine at position 285 in the LBD and is distinct from the binding mode of the well characterized PAH/HAH ligands. In support of this, the PAH-type antagonist 3′,4′-dimethoxyflavone blocked mAhR activation by 2,3,7,8-tetrachlorodibenzo-p-dioxin but not YH439. Furthermore, the strict correlation between response to exogenous PAH/HAH ligands and mimics of endogenous activation suggests that a PAH-type ligand may underpin endogenous mechanisms of activation.
dc.description.statementofresponsibilityFiona Whelan, Nan Hao, Sebastian G. B. Furness, Murray L. Whitelaw and Anne Chapman-Smith
dc.identifier.citationMolecular Pharmacology, 2010; 77(6):1037-1046
dc.identifier.doi10.1124/mol.109.062927
dc.identifier.issn0026-895X
dc.identifier.issn1521-0111
dc.identifier.orcidWhelan, F. [0000-0002-0791-6850]
dc.identifier.orcidHao, N. [0000-0001-5836-3507]
dc.identifier.urihttp://hdl.handle.net/2440/59803
dc.language.isoen
dc.publisherAmer Soc Pharmacology Experimental Therapeutics
dc.rightsCopyright © 2010 by the American Society for Pharmacology and Experimental Therapeutics
dc.source.urihttps://doi.org/10.1124/mol.109.062927
dc.subjectCell Line
dc.subjectAnimals
dc.subjectZebrafish
dc.subjectHumans
dc.subjectReceptors, Aryl Hydrocarbon
dc.subjectDNA Primers
dc.subjectElectrophoretic Mobility Shift Assay
dc.subjectAmino Acid Substitution
dc.subjectPolymerase Chain Reaction
dc.subjectMutagenesis
dc.subjectBinding Sites
dc.subjectAmino Acid Sequence
dc.subjectBase Sequence
dc.subjectSequence Homology, Amino Acid
dc.subjectMolecular Sequence Data
dc.titleAmino acid substitutions in the aryl hydrocarbon receptor ligand binding domain reveal YH439 as an atypical AhR activator
dc.typeJournal article
pubs.publication-statusPublished

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