IFIBYNE   05513
INSTITUTO DE FISIOLOGIA, BIOLOGIA MOLECULAR Y NEUROCIENCIAS
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Exploring the molecular basis of action of the inverse LXR agonist 27-nor-5-cholestenoic acid
Autor/es:
LAUTARO D. ALVAREZ; M. VIRGINIA DANSEY; DANIELA NAVALESI; DIEGO Y GRINMAN; RENÉ HOUTMAN; ADRIANA S VELEIRO; ADALI PECCI; GERARDO BURTON
Lugar:
Ajaccio
Reunión:
Conferencia; EMBO Conference-Nuclear Receptors: from molecules to humans; 2015
Institución organizadora:
EMBO
Resumen:
Liver X receptors (LXRs) are transcription factors activated by cholesterol metabolites containing an oxidized side chain. Due to their ability to regulate lipid metabolism and cholesterol transport, in the last decade they have become attractive pharmacological targets. Many potential applications targeting LXRs have been proposed for the treatment of several diseases such as atherosclerosis, type 2 diabetes and Alzheimer, among others. LXRs are closely related to DAF-12, a nuclear receptor involved in nematode life span and regulated by the binding of C-27 steroidal acids. Based on our finding that the lack of the C-25 methyl group does not abolish their DAF-12 activity, recently we evaluated the effect of removing it from the (25R)-cholestenoic acid, an endogenous LXR agonist. We found that 27-nor-5-cholestenoic acid behaves as an inverse agonist of LXR, demonstrating thus that the simple removal of the C-25 methyl moiety of cholestenoic acid provokes a drastic change in the LXR activity. Using Molecular Dynamics simulation we have observed that the C-25 methyl moiety would be necessary for the maintenance of a torsioned conformation of the steroid side chain that stabilizes an active LXR state.In this work, in order to further investigate the action of 27-nor-5-cholestenoic acid on LXR, we used the MARCoNI (Microarray Assay for Real-time Coregulator-Nuclear Receptor Interaction) array to evaluate the ability of the complex to interact with a set of 154 peptides each representing a coregulator derived motif (NR-box). We found that 27-nor-5-cholestenoic acid produces an interaction profile very different compared to agonists, with a marked preference to bind corepressors rather than coactivators. Then, using the structure of the LBD LXR/24(S),25-epoxycholesterolcomplex, in which a peptide corresponding to the second NR-box of the coactivator NCOA1 was co-crystallized, we carried out MD simulations of systems containing receptor, peptide and ligand atoms. Accordingly, we observed that the presence of 27-nor-5-cholestenoic acid provoked a destabilization of the interaction between the receptor and the coactivator peptide. Finally, the expression of LXR target genes involved in cholesterol efflux regulation and triglycerides synthesis was determined, finding that the effect of this compound seems to be dependent on the cell type. Together our results contribute to improve our understanding on the molecular basis of LXRmechanisms of action and provide a new scaffold in the quest for novelselective LXR modulators.