The human orphan nuclear receptor tailless (TLX, NR2E1) is druggable

• Published in: PloS one 2014-06, Vol.9 (6), p.e99440
• Main Authors: Benod, Cindy, Villagomez, Rosa, Filgueira, Carly S, Hwang, Peter K, Leonard, Paul G, Poncet-Montange, Guillaume, Rajagopalan, Senapathy, Fletterick, Robert J, Gustafsson, Jan-Åke, Webb, Paul
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Binders; Binding; Binding Sites; Biochemistry; Biology and Life Sciences; Biophysics; Brain; Brain cancer; Brain research; Brain stem; Brain tumors; COUP Transcription Factor II - antagonists & inhibitors; COUP Transcription Factor II - physiology; Crystal structure; Drugs; Dydrogesterone - pharmacology; Estrogen Receptor beta - antagonists & inhibitors; Estrogen Receptor beta - physiology; Fluorescent indicators; Gene expression; Genes, Reporter; HeLa Cells; Helices; Homology; Humans; Inhibitory Concentration 50; Kinases; Lead compounds; Ligands; Luciferases, Renilla - biosynthesis; Luciferases, Renilla - genetics; Medicine; Medicine and Health Sciences; Models, Molecular; Molecular biology; Molecular Sequence Data; Neural stem cells; Neurogenesis; Nuclear receptors; Piperazines - pharmacology; Protein Binding; Proteins; Proteomics; Pyrazoles - pharmacology; Receptors; Receptors, Cytoplasmic and Nuclear - antagonists & inhibitors; Receptors, Cytoplasmic and Nuclear - chemistry; Receptors, Cytoplasmic and Nuclear - physiology; Retinoid X Receptor alpha - antagonists & inhibitors; Retinoid X Receptor alpha - physiology; Scaffolds; Sedimentation & deposition; Stem cells; Transcription; Transcription factors; Transcription, Genetic - drug effects; Transcriptional Activation - drug effects; Tumors; Yang, Cindy
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0099440

Nuclear receptors (NRs) are an important group of ligand-dependent transcriptional factors. Presently, no natural or synthetic ligand has been identified for a large group of orphan NRs. Small molecules to target these orphan NRs will provide unique resources for uncovering regulatory systems that impact human health and to modulate these pathways with drugs. The orphan NR tailless (TLX, NR2E1), a transcriptional repressor, is a major player in neurogenesis and Neural Stem Cell (NSC) derived brain tumors. No chemical probes that modulate TLX activity are available, and it is not clear whether TLX is druggable. To assess TLX ligand binding capacity, we created homology models of the TLX ligand binding domain (LBD). Results suggest that TLX belongs to an emerging class of NRs that lack LBD helices α1 and α2 and that it has potential to form a large open ligand binding pocket (LBP). Using a medium throughput screening strategy, we investigated direct binding of 20,000 compounds to purified human TLX protein and verified interactions with a secondary (orthogonal) assay. We then assessed effects of verified binders on TLX activity using luciferase assays. As a result, we report identification of three compounds (ccrp1, ccrp2 and ccrp3) that bind to recombinant TLX protein with affinities in the high nanomolar to low micromolar range and enhance TLX transcriptional repressive activity. We conclude that TLX is druggable and propose that our lead compounds could serve as scaffolds to derive more potent ligands. While our ligands potentiate TLX repressive activity, the question of whether it is possible to develop ligands to de-repress TLX activity remains open.