title: Divergent sequence tunes ligand sensitivity in phospholipid-regulated hormone receptors.
abstract: The members of the NR5A subfamily of nuclear receptors (NRs) are important regulators of pluripotency, lipid and glucose homeostasis, and steroidogenesis. Liver receptor homologue 1 (LRH-1; NR5A2) and steroidogenic factor 1 (SF-1; NR5A1) have therapeutic potential for the treatment of metabolic and neoplastic disease; however, a poor understanding of their ligand regulation has hampered the pursuit of these proteins as pharmaceutical targets. In this study, we dissect how sequence variation among LRH-1 orthologs affects phospholipid (PL) binding and regulation. Both human LRH-1 (hLRH-1) and mouse LRH-1 (mLRH-1) respond to newly discovered medium chain PL agonists to modulate lipid and glucose homeostasis. These PLs activate hLRH-1 by altering receptor dynamics in a newly identified alternate activation function region. Mouse and Drosophila orthologs contain divergent sequences in this region potentially altering PL-driven activation. Structural evidence suggests that these sequence differences in mLRH-1 and Drosophila FTZ-f1 (dmFTZ-f1) confer at least partial ligand independence, making them poor models for hLRH-1 studies; however, the mechanisms of ligand independence remain untested. We show using structural and biochemical methods that the recent evolutionary divergence of the mLRH-1 stabilizes the active conformation in the absence of ligand, yet does not abrogate PL-dependent activation. We also show by mass spectrometry and biochemical assays that FTZ-f1 is incapable of PL binding. This work provides a structural mechanism for the differential tuning of PL sensitivity in NR5A orthologs and supports the use of mice as viable therapeutic models for LRH-1-dependent diseases.
authors.affiliation: Department of Biochemistry, Emory University School of Medicine, Atlanta, Georgia 30322, USA.
authors.forename: Paul M
authors.initials: PM
authors.lastname: Musille
authors.forename: Manish
authors.initials: M
authors.lastname: Pathak
authors.forename: Janelle L
authors.initials: JL
authors.lastname: Lauer
authors.forename: Patrick R
authors.initials: PR
authors.lastname: Griffin
authors.forename: Eric A
authors.initials: EA
authors.lastname: Ortlund
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites / Q000235:genetics; D018360:Crystallography, X-Ray; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism; D004331:Drosophila melanogaster; D014644:Genetic Variation; D006801:Humans; D008024:Ligands; D013058:Mass Spectrometry; D051379:Mice; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010715:Phosphatidylglycerols / Q000378:metabolism; D010743:Phospholipids / Q000378:metabolism*; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D018160:Receptors, Cytoplasmic and Nuclear / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013045:Species Specificity; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
chemical_list: D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D008024:Ligands; C082631:NR5A2 protein, human; C431936:Nr5a2 protein, mouse; D010715:Phosphatidylglycerols; D010743:Phospholipids; D018160:Receptors, Cytoplasmic and Nuclear; D011994:Recombinant Proteins; D014157:Transcription Factors; C499712:nuclear hormone receptor FTZ-F1, Drosophila
keywords: Diabetes; Glucose Metabolism; Hormone Receptors; Mouse; Phosphatidylcholine; Phospholipid