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: Eiji Ochiai, Daishiro Miura, Hiroshi Eguchi, Sachiko Ohara, Kazuya Takenouchi, Yoshiaki Azuma, Takashi Kamimura, Anthony W Norman, Seiichi Ishizuka
• Journal: Molecular endocrinology (Baltimore, Md.) (Mol Endocrinol) Vol. 19 Issue 5 Pg. 1147-57 (May 2005) ISSN: 0888-8809 [Print] United States
• PMID: 15650022 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, U.S. Gov't, P.H.S.)

Chemical References

• 23-25-dehydro-1,25(OH)D(3)-26,23-lactone
• Lactones
• Receptors, Calcitriol
• TEI 9647
• ZK159222
• Vitamin D
• Calcitriol
• Cysteine

Topics

• Amino Acid Sequence
• Animals
• Calcitriol (analogs & derivatives, pharmacology)
• Cysteine (metabolism)
• Humans
• Lactones (metabolism)
• Molecular Sequence Data
• Osteosarcoma (metabolism)
• Rats
• Receptors, Calcitriol (metabolism)
• Species Specificity
• Vitamin D (agonists, antagonists & inhibitors)