Metabolism of the vitamin D analog EB1089 by cultured human cells: redirection of hydroxylation site to distal carbons of the side-chain

Shankar, V.; Dilworth, F. Jeffrey; Makin, H. L. J.; Schroeder, Neil J.; Trafford, D.J.H.; Kissmeyer, Anne-Marie; Calverley, Martin J.; Binderup, Ernst; Jones, Glenville

doi:10.1016/s0006-2952(96)00815-5

Cited by 45 publications

(24 citation statements)

References 21 publications

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“…Limited digest proteolysis shows that the 20-epi analog-receptor complexes are more resistant to digestion and suggests that they are more stable. Additionally, an important role might be played by the rate of assimilation and how the synthetic agonists are metabolized vs. the natural ligand in different cell types (25,31). Altogether, these data suggest that the life time of the active conformation is then the main factor responsible for the formation of a more potent complex with coactivators like DRIP and the subsequent higher transcription activity.…”

Section: Discussionmentioning

confidence: 98%

Crystal structures of the vitamin D receptor complexed to superagonist 20-epi ligands

Tocchini-Valentini

Rochel

Wurtz

et al. 2001

Proc. Natl. Acad. Sci. U.S.A.

221

198

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The crystal structures of the ligand-binding domain (LBD) of the vitamin D receptor complexed to 1␣,25(OH)2D3 and the 20-epi analogs, MC1288 and KH1060, show that the protein conformation is identical, conferring a general character to the observation first made for retinoic acid receptor (RAR) that, for a given LBD, the agonist conformation is unique, the ligands adapting to the binding pocket. In all complexes, the A-to D-ring moieties of the ligands adopt the same conformation and form identical contacts with the protein. Differences are observed only for the 17␤-aliphatic chains that adapt their conformation to anchor the 25-hydroxyl group to His-305 and His-397. The inverted geometry of the C20 methyl group induces different paths of the aliphatic chains. The ligands exhibit a low-energy conformation for MC1288 and a more strained conformation for the two others. KH1060 compensates this energy cost by additional contacts. Based on the present data, the explanation of the superagonist effect is to be found in higher stability and longer half-life of the active complex, thereby excluding different conformations of the ligand binding domain. A different class of proteins has been characterized that stimulate the transcriptional activity of liganded NRs in an activation function 2 (AF2)-dependent way. These coactivators are thought to bridge the NRs to the transcriptional apparatus. In particular, VDR is regulated by coactivators belonging to the steroid receptor activator (SRC)͞p160 family of proteins, which contain several LXXLL motifs (6). This motif has been shown to form an amphipatic ␣-helical structure that can interact with the AF2 region of NRs (7). Another class of coactivators [vitamin D receptor-interacting protein (DRIP), thyroid hormone receptor-associated protein (TRAP), activator-recruited cofactor (ARC); refs. 8-11] has been isolated as multiprotein complexes and strongly potentiated transcription mediated by VDR͞RXR in a ligand-dependent manner on DNA templates assembled into chromatin (8). One of their components, DRIP205, interacts directly with the ligand-binding domain (LBD) in the presence of ligand and anchors the rest of the subunits to the receptor.Among the several synthetic analogs of vitamin D, the 20-epi compounds, which exhibit an inverted stereochemistry at position 20 in the flexible aliphatic chain, have attracted much attention. They are potent growth inhibitors and inducers of cell differentiation, while showing an affinity similar to vitamin D for VDR (11). KH1060 ( Fig. 1), a member of this 20-epi family, exhibits similar properties, with decreased calcemic side effects. These compounds induce VDR-dependent transcription at concentrations at least 100-fold lower than the natural ligand and present antiproliferative activity several orders of magnitude higher than the natural ligand (11-13). The differences in biological activity of 1␣,25(OH) 2 D 3 and the 20-epi molecules in general, and KH1060 in particular, are known to be VDR-LBD dependent, but are not yet understood. Th...

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Section: Discussionmentioning

confidence: 98%

Crystal structures of the vitamin D receptor complexed to superagonist 20-epi ligands

Tocchini-Valentini

Rochel

Wurtz

et al. 2001

Proc. Natl. Acad. Sci. U.S.A.

221

198

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show abstract

“…4B and C). In addition, because the side-chain double-bond structure of EB1089 is hydroxylated in distal C26 and C26a sites, the metabolism of EB1089 might not involve CYP24A1 [47]. EB1089 has been shown to be more potent in the cancer cell growth inhibition than 1,25-VD both in vivo and in vitro [48][49][50][51].…”

Section: Discussionmentioning

confidence: 99%

Down-regulation of NF-κB signals is involved in loss of 1α,25-dihydroxyvitamin D3 responsiveness

Bao¹,

Ting²,

Hsu³

et al. 2010

The Journal of Steroid Biochemistry and Molecular Biology

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“…Additionally, an important role might be played by the rate of assimilation, i.e. how synthetic agonists are metabolized as compared to the natural ligand in different cells types [43,44].…”

Section: -Epi Analogsmentioning

confidence: 99%

Structural Basis for Ligand Activity in VDR

Rochel

Moras

2011

Vitamin D

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Metabolism of the vitamin D analog EB1089 by cultured human cells: redirection of hydroxylation site to distal carbons of the side-chain

Cited by 45 publications

References 21 publications

Crystal structures of the vitamin D receptor complexed to superagonist 20-epi ligands

Crystal structures of the vitamin D receptor complexed to superagonist 20-epi ligands

Down-regulation of NF-κB signals is involved in loss of 1α,25-dihydroxyvitamin D3 responsiveness

Structural Basis for Ligand Activity in VDR

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