title: Molecular mechanism of the vitamin D antagonistic actions of (23S)-25-dehydro-1alpha-hydroxyvitamin D3-26,23-lactone depends on the primary structure of the carboxyl-terminal region of the vitamin d receptor.
abstract: We reported that (23S)-25-dehydro-1alpha-hydroxyvitamin D(3)-26,23-lactone (TEI-9647) antagonizes vitamin D receptor (VDR)-mediated genomic actions of 1alpha,25-dihydroxyvitamin D(3) [1alpha,25(OH)(2)D(3)] in human cells but is agonistic in rodent cells. Human and rat VDR ligand-binding domains are similar, but differences in the C-terminal region are important for ligand binding and transactivation and might determine the agonistic/antagonistic effects of TEI-9647. We tested TEI-9647 on 1alpha,25(OH)(2)D(3) transactivation using SaOS-2 cells (human osteosarcoma) or ROS 24/1 cells (rat osteosarcoma) cotransfected with human or rodent VDR and a reporter. In both cell lines, TEI-9647 was antagonistic with wild-type human (h)VDR, but agonistic with overexpressed wild-type rat (r)VDR. VDR chimeras substituting the hVDR C-terminal region (activation function 2 domain) with corresponding rVDR residues diminished antagonism and increased agonism of TEI-9647. However, substitution of 25 C-terminal rVDR residues with corresponding hVDR residues diminished agonism and increased antagonism of TEI-9647. hVDR mutants (C403S, C410N) demonstrated that Cys403 and/or 410 was necessary for TEI-9647 antagonism of 1alpha,25(OH)(2)D(3) transactivation. These results suggest that species specificity of VDR, especially in the C-terminal region, determines the agonistic/antagonistic effects of TEI-9647 that determine, in part, VDR interactions with coactivators and emphasize the critical interaction between TEI-9647 and the two C-terminal hVDR Cys residues to mediate the antagonistic effect of TEI-9647.
authors.affiliation: Department of Biochemistry, University of California-Riverside, Riverside, CA 92521, USA.
authors.forename: Eiji
authors.initials: E
authors.lastname: Ochiai
authors.forename: Daishiro
authors.initials: D
authors.lastname: Miura
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Eguchi
authors.forename: Sachiko
authors.initials: S
authors.lastname: Ohara
authors.forename: Kazuya
authors.initials: K
authors.lastname: Takenouchi
authors.forename: Yoshiaki
authors.initials: Y
authors.lastname: Azuma
authors.forename: Takashi
authors.initials: T
authors.lastname: Kamimura
authors.forename: Anthony W
authors.initials: AW
authors.lastname: Norman
authors.forename: Seiichi
authors.initials: S
authors.lastname: Ishizuka
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002117:Calcitriol / Q000031:analogs & derivatives* / Q000494:pharmacology*; D003545:Cysteine / Q000378:metabolism; D006801:Humans; D007783:Lactones / Q000378:metabolism*; D008969:Molecular Sequence Data; D012516:Osteosarcoma / Q000378:metabolism; D051381:Rats; D018167:Receptors, Calcitriol / Q000378:metabolism*; D013045:Species Specificity; D014807:Vitamin D / Q000819:agonists / Q000037:antagonists & inhibitors*
chemical_list: C465239:23-25-dehydro-1,25(OH)D(3)-26,23-lactone; D007783:Lactones; D018167:Receptors, Calcitriol; C400545:TEI 9647; C410228:ZK159222; D014807:Vitamin D; D002117:Calcitriol; D003545:Cysteine