title: The human orphan nuclear receptor tailless (TLX, NR2E1) is druggable.
abstract: 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.
authors.affiliation: Department of Genomic Medicine, Houston Methodist Research Institute (HMRI), Houston, Texas, United States of America.
authors.forename: Cindy
authors.initials: C
authors.lastname: Benod
authors.affiliation: Department of Genomic Medicine, Houston Methodist Research Institute (HMRI), Houston, Texas, United States of America.
authors.forename: Rosa
authors.initials: R
authors.lastname: Villagomez
authors.affiliation: Department of Genomic Medicine, Houston Methodist Research Institute (HMRI), Houston, Texas, United States of America.
authors.forename: Carly S
authors.initials: CS
authors.lastname: Filgueira
authors.affiliation: Department of Biophysics and Biochemistry, University of California San Francisco, San Francisco, California, United States of America.
authors.forename: Peter K
authors.initials: PK
authors.lastname: Hwang
authors.affiliation: Department of Biochemistry and Molecular Biology, MD Anderson Cancer Center, University of Texas, Houston, Texas, United States of America; Center for Biomolecular Structure and Function, MD Anderson Cancer Center, University of Texas, Houston, Texas, United States of America.
authors.forename: Paul G
authors.initials: PG
authors.lastname: Leonard
authors.affiliation: Department of Biochemistry and Molecular Biology, MD Anderson Cancer Center, University of Texas, Houston, Texas, United States of America.
authors.forename: Guillaume
authors.initials: G
authors.lastname: Poncet-Montange
authors.affiliation: Department of Genomic Medicine, Houston Methodist Research Institute (HMRI), Houston, Texas, United States of America.
authors.forename: Senapathy
authors.initials: S
authors.lastname: Rajagopalan
authors.affiliation: Department of Biophysics and Biochemistry, University of California San Francisco, San Francisco, California, United States of America.
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Fletterick
authors.affiliation: University of Houston Center for Nuclear Receptors and Cell Signaling, Houston, Texas, United States of America.
authors.forename: Jan-Åke
authors.initials: JÅ
authors.lastname: Gustafsson
authors.affiliation: Department of Genomic Medicine, Houston Methodist Research Institute (HMRI), Houston, Texas, United States of America.
authors.forename: Paul
authors.initials: P
authors.lastname: Webb
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D051837:COUP Transcription Factor II / Q000037:antagonists & inhibitors / Q000502:physiology; D004394:Dydrogesterone / Q000494:pharmacology*; D047629:Estrogen Receptor beta / Q000037:antagonists & inhibitors / Q000502:physiology; D017930:Genes, Reporter; D006367:HeLa Cells; D006801:Humans; D020128:Inhibitory Concentration 50; D008024:Ligands; D049410:Luciferases, Renilla / Q000096:biosynthesis / Q000235:genetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D057093:Orphan Nuclear Receptors; D010879:Piperazines / Q000494:pharmacology*; D011485:Protein Binding; D011720:Pyrazoles / Q000494:pharmacology*; D018160:Receptors, Cytoplasmic and Nuclear / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000502:physiology*; D047490:Retinoid X Receptor alpha / Q000037:antagonists & inhibitors / Q000502:physiology; D014158:Transcription, Genetic / Q000187:drug effects; D015533:Transcriptional Activation / Q000187:drug effects*
chemical_list: D051837:COUP Transcription Factor II; D047629:Estrogen Receptor beta; D008024:Ligands; C088601:NR2E1 protein, human; D057093:Orphan Nuclear Receptors; D010879:Piperazines; D011720:Pyrazoles; D018160:Receptors, Cytoplasmic and Nuclear; D047490:Retinoid X Receptor alpha; D004394:Dydrogesterone; D049410:Luciferases, Renilla