title: 20-Epi analogues of 1,25-dihydroxyvitamin D3 are highly potent inducers of DRIP coactivator complex binding to the vitamin D3 receptor.
abstract: 1,25-Dihydroxyvitamin D3 (1,25(OH)2D3) plays a major role in the stimulation of bone growth, mineralization, and intestinal calcium and phosphate absorption; it also acts as a general inhibitor of cellular proliferation. Several new, clinically relevant compounds dissociate antiproliferative and calcemic activities of 1,25(OH)2D3, but the molecular basis for this has not been clearly elucidated. Here, we tested whether the potency of one class of compounds, 20-epi analogues, to induce myeloid cell differentiation, is because of direct molecular effects on vitamin D receptor (VDR). We report that two 20-epi analogues, MC1627 and MC1288, induced differentiation and transcription of p21(Waf1,Cip1), a key VDR target gene involved in growth inhibition, at a concentration 100-fold lower than that of 1,25(OH)2D3. We compared this sensitivity to analogue effects on VDR interacting proteins: RXR, GRIP-1, and DRIP205, a subunit of the DRIP coactivator complex. Compared with the interaction of VDR with RXR or GRIP-1, the differentiation dose-response most closely correlated to the ligand-dependent recruitment of the DRIP coactivator complex to VDR and to the ability of the receptor to activate transcription in a cell-free system. These results provide compelling links between the efficiency of the 20-epi analogue in inducing VDR/DRIP interactions, transactivation in vitro, and its enhanced ability to induce cellular differentiation.
authors.affiliation: Cell Biology Program, Memorial Sloan-Kettering Cancer Center, New York, New York 10021, USA.
authors.forename: W
authors.initials: W
authors.lastname: Yang
authors.forename: L P
authors.initials: LP
authors.lastname: Freedman
mesh_terms: D002117:Calcitriol / Q000031:analogs & derivatives* / Q000378:metabolism* / Q000494:pharmacology; D002454:Cell Differentiation / Q000187:drug effects; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000235:genetics; D006801:Humans; D008264:Macrophages / Q000166:cytology; D056892:Mediator Complex; D009000:Monocytes / Q000166:cytology; D009687:Nuclear Proteins / Q000378:metabolism*; D051958:Nuclear Receptor Coactivator 2; D011485:Protein Binding; D018167:Receptors, Calcitriol / Q000235:genetics / Q000378:metabolism*; D018168:Receptors, Retinoic Acid / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D020218:Response Elements; D047488:Retinoid X Receptors; D015534:Trans-Activators; D014157:Transcription Factors / Q000378:metabolism; D015533:Transcriptional Activation; D020298:U937 Cells
chemical_list: C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; C113182:DRIP, VDR interacting protein complex; C119704:MC 1627; C491863:MED4 protein, human; D056892:Mediator Complex; C498001:NCOA2 protein, human; D009687:Nuclear Proteins; D051958:Nuclear Receptor Coactivator 2; D018167:Receptors, Calcitriol; D018168:Receptors, Retinoic Acid; D011993:Recombinant Fusion Proteins; D047488:Retinoid X Receptors; D015534:Trans-Activators; D014157:Transcription Factors; D002117:Calcitriol