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Inhibition of 1,25‐Dihydroxyvitamin D 3 ‐Dependent Transcription by Synthetic LXXLL Peptide Antagonists that Target the Activation Domains of the Vitamin D and Retinoid X Receptors
Author(s) -
Pathrose Peterson,
Barmina Olga,
Chang ChingYi,
McDonnell Donald P.,
Shevde Nirupama K.,
Pike J. Wesley
Publication year - 2002
Publication title -
journal of bone and mineral research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.882
H-Index - 241
eISSN - 1523-4681
pISSN - 0884-0431
DOI - 10.1359/jbmr.2002.17.12.2196
Subject(s) - retinoid x receptor , calcitriol receptor , transactivation , retinoic acid , nuclear receptor , transcription factor , retinoid , receptor , retinoid x receptor beta , retinoid x receptor alpha , biology , microbiology and biotechnology , chemistry , biochemistry , gene
Abstract The vitamin D receptor (VDR) is known to mediate the biological actions of 1,25‐dihydroxyvitamin D 3 [1,25(OH) 2 D 3 ] through its ability to regulate cellular programs of gene expression. Although RXR appears to participate as a heterodimeric partner with the VDR, absolute evidence for its role remains equivocal in vivo. To test this role and to investigate the requirement for comodulator interaction, we identified VDR‐ and retinoid X receptor (RXR)‐interacting LXXLL peptides and examined whether these molecules could block vitamin D and 9‐ cis retinoic acid (9‐ cis RA) response. We used a mammalian cell two‐hybrid system to screen a series of nuclear receptor (NR)‐reactive LXXLL peptides previously identified through phage display screening for hormone‐dependent reactivity with either VDR or RXR. Three categories of peptides were identified: those reactive with both VDR and RXR, those selective for RXR, and those unreactive to either receptor. Peptide fusion proteins were then examined in MC3T3‐E1 cells for their ability to block induction of the osteocalcin (OC) promoter by 1,25(OH) 2 D 3 or stimulation of a retinoic acid response element‐thymidine kinase (RARE‐TK) reporter by 9‐ cis‐ RA. Peptides that interacted with both VDR and RXR blocked 1,25(OH) 2 D 3 ‐dependent transcription by up to 75%. Control LXXLL sequences derived from Src‐1 and Grip also suppressed 1,25(OH) 2 D 3 ‐induced transactivation; peptides that interacted with RXR blocked 9‐ cis‐ RA‐induced transcription. Interestingly, two RXR‐interacting peptides were also found to block 1,25(OH) 2 D 3 response effectively. These studies support the idea that comodulator recruitment is essential for VDR‐ and RXR‐mediated gene expression and that RXR is required for 1,25(OH) 2 D 3 ‐induced OC gene transcription. This approach may represent a novel means of assessing the contribution of RXR in various endogenous biological responses to 1,25(OH) 2 D 3 .