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

Schwarz, P. F.; Perhal, A. F.; Preglej, T.; Breit, L.; Schmetterer, K. G.; Grienke, U.; Janneschütz, J.; Chen, Y.; Rochel, N.; Kirchmair, J.; Schützenmeister, N.; Rollinger, J. M.; Bonelli, M.; Dirsch, V. M.

doi:10.1101/2025.04.01.646598

bioRxiv · 10.1101/2025.04.01.646598

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

Schwarz, P. F.·Perhal, A. F.·Preglej, T.·Breit, L.·Schmetterer, K. G.·Grienke, U.·Janneschütz, J.·Chen, Y.·Rochel, N.·Kirchmair, J.·Schützenmeister, N.·Rollinger, J. M.·Bonelli, M.·Dirsch, V. M.

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Abstract

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.

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Schwarz, P. F., Perhal, A. F., Preglej, T., Breit, L., Schmetterer, K. G., Grienke, U., Janneschütz, J., Chen, Y., Rochel, N., Kirchmair, J., Schützenmeister, N., Rollinger, J. M., Bonelli, M., Dirsch, V. M.. 2025-04-04. Primulagenin A is a potent inverse agonist of the nuclear receptor RAR-related orphan receptor gamma (RORγ). https://doi.org/10.1101/2025.04.01.646598

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