title: Different molecular mechanisms of vitamin D(3) receptor antagonists.
abstract: Two structurally different antagonists of the nuclear hormone 1alpha,25-dihydroxyvitamin D(3) [1alpha,25(OH)(2)D(3)], the 25-carboxylic ester ZK159222 and the 26,23-lactone TEI-9647, have recently been described. In this study, the molecular mechanisms and the efficacy of both antagonists were compared. ZK159222 showed similar potency and sensitivity to 1alpha,25(OH)(2)D(3) in ligand-dependent gel shift assays using the vitamin D receptor (VDR), the retinoid X receptor, and specific DNA binding sites, whereas TEI-9647 displayed reduced potency and >10-fold lower sensitivity in this assay system. Limited protease digestion and gel shift clipping assays showed that the two antagonists stabilized individual patterns of VDR conformations. Both antagonists prevented the interaction of the VDR with coactivator proteins, as demonstrated by GST-pull-down and supershift assays; like the natural hormone, however, they were able to induce a dissociation of corepressor proteins. Interestingly, ZK159222 demonstrated functional antagonism in reporter gene assays both in HeLa and MCF-7 cells, whereas TEI-9647 functioned as a less sensitive antagonist only in MCF-7 cells. In conclusion, the two 1alpha,25(OH)(2)D(3) analogs act in part via different molecular mechanisms, which allows us to speculate that ZK159222 is a more complete antagonist and TEI-9647 a more selective antagonist.
authors.affiliation: Institut für Physiologische Chemie I and Biomedizinisches Forschungszentrum, Heinrich-Heine-Universität, Düsseldorf, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Toell
authors.forename: M M
authors.initials: MM
authors.lastname: Gonzalez
authors.forename: D
authors.initials: D
authors.lastname: Ruf
authors.forename: A
authors.initials: A
authors.lastname: Steinmeyer
authors.forename: S
authors.initials: S
authors.lastname: Ishizuka
authors.forename: C
authors.initials: C
authors.lastname: Carlberg
mesh_terms: D002117:Calcitriol / Q000031:analogs & derivatives* / Q000494:pharmacology*; D004587:Electrophoresis, Agar Gel; D005786:Gene Expression Regulation / Q000187:drug effects; D006367:HeLa Cells; D006801:Humans; D011487:Protein Conformation / Q000187:drug effects; D018167:Receptors, Calcitriol / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000378:metabolism; D018168:Receptors, Retinoic Acid / Q000378:metabolism; D047488:Retinoid X Receptors; D014157:Transcription Factors / Q000378:metabolism; D014407:Tumor Cells, Cultured; D014807:Vitamin D / Q000031:analogs & derivatives; D014809:Vitamin D-Binding Protein / Q000378:metabolism
chemical_list: C116441:2-methyl-1,25-dihydroxyvitamin D3; D018167:Receptors, Calcitriol; D018168:Receptors, Retinoic Acid; D047488:Retinoid X Receptors; C400545:TEI 9647; D014157:Transcription Factors; D014809:Vitamin D-Binding Protein; C410228:ZK159222; D014807:Vitamin D; D002117:Calcitriol