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Helix-stabilized cyclic peptides as selective inhibitors of steroid receptor-coactivator interactions.

ABSTRACT: The interaction between nuclear receptors and coactivators provides an arena for testing whether protein-protein interactions may be inhibited by small molecule drug candidates. We provide evidence that a short cyclic peptide, containing a copy of the LXXLL nuclear receptor box pentapeptide, binds tightly and selectively to estrogen receptor alpha. Furthermore, as shown by x-ray analysis, the disulfide-bridged nonapeptide, nonhelical in aqueous solutions, is able to adopt a quasihelical conformer while binding to the groove created by ligand attachment to estrogen receptor alpha. An i, i+3 linked analog, H-Lys-cyclo(d-Cys-Ile-Leu-Cys)-Arg-Leu-Leu-Gln-NH2 (peptidomimetic estrogen receptor modulator 1), binds with a Ki of 25 nM, significantly better than an i, i+4 bridged cyclic amide, as predicted by molecular modeling design criteria. The induction of helical character, effective binding, and receptor selectivity exhibited by this peptide analog provide strong support for this strategy. The stabilization of minimalist surface motifs may prove useful for the control of other macromolecular assemblies, especially when an amphiphilic helix is crucial for the strong binding interaction between two proteins.

SUBMITTER: Leduc AM

PROVIDER: S-EPMC208747 | biostudies-literature | 2003 Sep

REPOSITORIES: biostudies-literature

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Helix-stabilized cyclic peptides as selective inhibitors of steroid receptor-coactivator interactions.

Leduc Anne-Marie AM Trent John O JO Wittliff James L JL Bramlett Kelli S KS Briggs Stephen L SL Chirgadze Nikolay Y NY Wang Yong Y Burris Thomas P TP Spatola Arno F AF

Proceedings of the National Academy of Sciences of the United States of America 20030917 20

The interaction between nuclear receptors and coactivators provides an arena for testing whether protein-protein interactions may be inhibited by small molecule drug candidates. We provide evidence that a short cyclic peptide, containing a copy of the LXXLL nuclear receptor box pentapeptide, binds tightly and selectively to estrogen receptor alpha. Furthermore, as shown by x-ray analysis, the disulfide-bridged nonapeptide, nonhelical in aqueous solutions, is able to adopt a quasihelical conforme ...[more]

PMID: 13679575

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Project description:Estradiol and progesterone bind to their respective receptors in the hypothalamus and hippocampus to influence a variety of behavioral and physiological functions, including reproduction and cognition. Work from our lab and others has shown that the nuclear receptor coactivators, steroid receptor coactivator-1 (SRC-1) and SRC-2, are essential for efficient estrogen receptor (ER) and progestin receptor (PR) transcriptional activity in brain and for hormone-dependent behaviors. While the expression of SRC-1 in brain has been studied extensively, little is known about the expression of SRC-2 in brain. In the present studies, we found that SRC-2 was highly expressed throughout the hippocampus, amygdala and hypothalamus, including the medial preoptic area (MPOA), ventral medial nucleus (VMN), arcuate nucleus (ARC), bed nucleus of the stria terminalis, supraoptic nucleus and suprachiasmatic nucleus. In order for coactivators to function with steroid receptors, they must be expressed in the same cells. Indeed, SRC-2 and ER(alpha) were coexpressed in many cells in the MPOA, VMN and ARC, all brain regions known to be involved in female reproductive behavior and physiology. While in vitro studies indicate that SRC-2 physically associates with ER and PR, very little is known about receptor-coactivator interactions in brain. Therefore, we used pull-down assays to test the hypotheses that SRC-2 from hypothalamic and hippocampal tissue physically associate with ER and PR subtypes in a ligand-dependent manner. SRC-2 from both brain regions interacted with ER(alpha) bound to agonist, but not in the absence of ligand or in the presence of the selective ER modulator, tamoxifen. Analysis by mass spectrometry confirmed these ligand-dependent interactions between ER(alpha) and SRC-2 from brain. In dramatic contrast, SRC-2 from brain showed little to no interaction with ERbeta. Interestingly, SRC-2 from both brain regions interacted with PR-B, but not PR-A, in a ligand-dependent manner. Taken together, these findings reveal that SRC-2 is expressed in brain regions known to mediate a variety of steroid-dependent functions. Furthermore, SRC-2 is expressed in many ER(alpha) containing cells in the hypothalamus. Finally, SRC-2 from brain interacts with ER and PR in a subtype-specific manner, which may contribute to the functional differences of these steroid receptor subtypes in brain.

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Helix-stabilized cyclic peptides as selective inhibitors of steroid receptor-coactivator interactions.

Publications

Helix-stabilized cyclic peptides as selective inhibitors of steroid receptor-coactivator interactions.

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