Biology subjects

Rochel, N.

Publications and source records attributed to Rochel, N..

5 recordsLinked to original sources

bioRxiv2025

Primulagenin A is a potent inverse agonist of the nuclear receptor RAR-related orphan receptor gamma (RORγ)

Throughout history, herbal medicines and natural products have played a crucial role as therapeutics for humans, yet their molecular mechanisms of action often remain elusive. Here, we ask whether primulagenin A (PGA) from the traditionally used herbal substance Primula root, acts via the nuclear receptor ROR{gamma}, a key regulator of pro-inflammatory Th17 cells, which are linked to autoimmune diseases like psoriasis. Luciferase assays revealed a high potency (IC50 ~100 nM) and efficacy (Imax ~ 90%) of PGA as an inverse agonist of ROR{gamma}. To ensure sufficient supply, we established methods to isolate and synthesize PGA. Its binding to the human ROR{gamma} ligand binding domain was confirmed by nano differential scanning fluorimetry, and a structure-activity relationship was proposed by docking and site-directed mutagenesis. PGA downregulated ROR{gamma} target gene expression and inhibited murine and human Th17 differentiation in a concentration-dependent manner. It also reduced the proportion of IL-17A-producing Th17 cells. In this work, we identify PGA as a new, potent, and efficacious inverse agonist of ROR{gamma}, with potential for modulating immune responses in inflammatory and autoimmune diseases.

pharmacology and toxicology↗

bioRxiv2025

New structural insights into the control of the retinoic acid receptors RAR/RXR by DNA, ligands and transcriptional coregulators

Retinoic acid receptors (RARs) are ligand-dependent transcription factors essential for various biological processes, including embryogenesis, differentiation, and apoptosis. RARs function as heterodimers with retinoid X receptors (RXRs) and regulate gene expression via retinoic acid response elements (RAREs). Their transcriptional activity is modulated by coregulators, with corepressors maintaining repression in the absence of ligand and coactivators enabling transcription upon ligand binding. Structural studies reveal that DNA binding induces conformational changes affecting coregulator interactions. However, the precise structural organization of RAR/RXR-coregulator complexes and the allosteric influence of DNA on receptor function remain incompletely understood. Our study presents an integrative analysis of the RAR/RXR heterodimer bound to four distinct and relevant RAREs (DR0, DR1, DR5, and IR0) in complex with either a corepressor (NCoR) or a coactivator (TIF-2) nuclear receptor interaction domain. By combining small-angle X-ray scattering, hydrogen/deuterium exchange mass spectrometry and molecular dynamics simulations, we revealed that the heterodimer adopts distinct conformations depending on the DNA sequence, influencing interdomain distances and receptor interactions. Additionally, we uncovered the dynamic interplay between ligand, DNA, and coregulator binding. This study provides new insights into the structural features of coregulator proteins and highlights the allosteric influence of RAREs on receptor function.

biochemistry↗

bioRxiv2020

Molecular determinants of MED1 interaction with the DNA bound VDR-RXR heterodimer

The MED1 subunit of the Mediator complex is an essential coactivator of nuclear receptor-mediated transcriptional activation. While structural requirements for ligand-dependent binding of classical coactivator motifs of MED1 to numerous nuclear receptor ligand-binding domains have been fully elucidated, the recognition of the full-length or truncated coactivator by full nuclear receptor complexes remain unknown. Here we present structural details of the interaction between a large part of MED1 comprising its structured N-terminal and the flexible receptor-interacting domains and the mutual heterodimer of the vitamin D receptor (VDR) and the retinoid X receptor (RXR) bound to their cognate DNA response element. Using a combination of structural and biophysical methods we show that the ligand-dependent interaction between VDR and the second coactivator motif of MED1 is crucial for complex formation and we identify additional, previously unseen, interaction details. In particular, we identified RXR regions involved in the interaction with structured N-terminal domain of MED1, as well as VDR regions outside the classical coactivator binding cleft affected by coactivator recruitment. These findings highlight important roles of each receptor within the heterodimer in selective recognition of MED1 and contribute to our understanding of the nuclear receptor-coregulator complexes.

molecular biology↗

bioRxiv2019

PPARG is a tumor suppressor in basal bladder tumors offering new potential therapeutic opportunities.

PPAR{gamma} activation is a critical event in luminal muscle-invasive bladder cancer (MIBC) tumorigenesis, favoring both tumor cell growth and microenvironment modulation toward tumor immune escape. Conversely, the down-regulation of PPAR{gamma} activity in basal MIBC suggests tumor suppressive effects in this subgroup. Here, we report genetic, epigenetic and functional evidence to support the tumor suppressor role for PPAR{gamma} in basal bladder tumors. We identified hemizygous deletions, DNA hyper-methylation and loss-of-function mutations of PPAR{gamma} in basal MIBC, associated with PPAR{gamma} under-expression and its decreased activity. Re-expression of PPAR{gamma} in basal tumor cells resulted in the activation of PPAR{gamma} -dependent transcription program that modulated fatty acid metabolism and cell differentiation and decreased cell growth, which could partly rely on EGFR down-regulation. Structure-function studies of two PPAR{gamma} mutant revealed a destabilization of a region important for coactivator recruitment and should help develop potent molecules to activate PPAR{gamma} as a therapeutic strategy for basal MIBC. The identification of this subtype-dependent dual role of PPAR{gamma} in MIBC strengthens the critical role of PPAR{gamma} in bladder tumorigenesis and reinforces the interest in stratified medicine based on tumor molecular subtyping. One sentence summaryGenetic, epigenetic and functional evidence of a tumor suppressor role for PPAR{gamma} in basal bladder tumors offer new therapeutic opportunities for this subgroup.

cancer biology↗

bioRxiv2018

The tumor suppressor FBW7 and the vitamin D receptor are mutual cofactors.

The E3 ligase FBW7 targets drivers of cell cycle progression such as c-MYC for proteasomal degradation. It is frequently mutated in cancer, and is a tumor suppressor. Extensive epidemiological data links vitamin D deficiency to increased incidence of several cancers, although the underlying cancer-preventive mechanisms are poorly understood. Here, we show that hormonal 1,25-dihydroxyvitamin D3 (1,25D) rapidly stimulates the interaction of the VDR with FBW7, and that of FBW7 with c-MYC. In contrast, it blocks the association of FBW7 with c-MYC antagonist MXD1. 1,25D also enhances the association of FBW7, proteasome subunits, and ubiquitin with DNA-bound c-MYC, consistent with induced degradation of c-MYC on DNA. In addition to c-MYC, 1,25D accelerates the turnover of other FBW7 target proteins. Intriguingly, FBW7 is essential for optimal VDR gene expression. It is also recruited to VDR targets genes, and its depletion attenuates 1,25D-stimulated VDR DNA binding, transactivation, and cell cycle arrest. Thus, the VDR and FBW7 are mutual cofactors, which provides a molecular basis for the cancer-preventive actions of vitamin D through accelerated turnover of FBW7 target proteins.

molecular biology↗