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Differential use of transcription activation function 2 domain of the vitamin D receptor by 1,25-dihydroxyvitamin D3 and its A ring-modified analogs.
- Source :
-
Molecular endocrinology (Baltimore, Md.) [Mol Endocrinol] 1998 Apr; Vol. 12 (4), pp. 525-35. - Publication Year :
- 1998
-
Abstract
- Analogs of 1,25-dihydroxyvitamin D3 (1,25D3) can be used to elucidate details of vitamin D receptor (VDR) activation. The A ring-modified analog, (TN-2) has 15-fold less affinity for VDR, but its transcriptional activity is diminished 1000-fold. Likewise, the ability of TN-2 to induce a protease-resistant conformation in VDR is 1/1000 that of 1,25D3. The stability of the VDR-TN-2 complexes is also significantly lower than VDR-1,25D3 complexes. Mapping the VDR-binding site of TN-2 showed that it had a significantly greater requirement for transcription activation function 2 (AF-2) residues than 1,25D3 did. These results suggest that the increased requirement for AF-2 residues that was induced by the A ring modifications is associated with diminished receptor activation. To determine whether restoring the potency of TN-2 by additional structural modifications would change the requirements for AF-2 residues, we synthesized hybrid analogs with 1beta-hydroxymethyl-3-epi groups and with dimethyl groups at positions 26 and 27 of the side chain, without or with a double bond between CD ring positions 16 and 17. We found that the side chain modification enhanced transcriptional activity 150-fold, increased the ability of the receptor to form a protease-resistant conformation 100-fold, and stabilized the VDR-analog complexes. The addition of the 16-ene group further reduced the analog's dissociation rate and increased its potency in the protease assays. These functional changes in the hybrid analogs were associated with a significant reduction in interaction with AF-2 residues. We conclude that there is an inverse relationship between analogs' potencies and their interaction with AF-2 residues of VDR.
- Subjects :
- Animals
COS Cells
Calcitriol metabolism
Calcitriol pharmacology
Cell Line
Chlorocebus aethiops
Humans
Kidney cytology
Macromolecular Substances
Protein Structure, Tertiary
Receptors, Calcitriol metabolism
Receptors, Calcitriol physiology
Structure-Activity Relationship
Calcitriol analogs & derivatives
Calcitriol genetics
Receptors, Calcitriol genetics
Transcriptional Activation physiology
Subjects
Details
- Language :
- English
- ISSN :
- 0888-8809
- Volume :
- 12
- Issue :
- 4
- Database :
- MEDLINE
- Journal :
- Molecular endocrinology (Baltimore, Md.)
- Publication Type :
- Academic Journal
- Accession number :
- 9544988
- Full Text :
- https://doi.org/10.1210/mend.12.4.0083