ABSTRACT
The cultured cell-based in vitro assay using the stringency of ligand-receptor interactions is typically useful for screening certain hormone agonists from among a very large number of molecules. However, ligands are frequently altered or modified through evolution; indeed, even in the same receptor orthologs, different ligand sensitivity profiles are considered to arise among species and/or taxa. Such ligand transition has been observed in juvenile hormone (JH), one of the most important endocrine factors in arthropods. To understand the molecular basis of ligand selectivity alteration in hormone receptors, we compared the amino acid sequences and ligand selectivity of the JH receptor, Methoprene-tolerant (Met), among three insects (Drosophila melanogaster, Aedes aegypti and Tribolium castaneum) and one crustacean (Daphnia pulex). Compared with D. pulex, we found that the receptors of the three insects showed a higher sensitivity to JH III, which is the major innate JH ligand in insects. Furthermore, point mutation analysis in Met sequences revealed a candidate amino acid residue that is important for increasing JH sensitivity in insects. Amino acid mutations in Met may have affected changes in ligand selectivity intermittently over the course of the evolution of the JH-signaling pathway. These findings are useful to improve the existing (developing) cultured cell-based assay system and may shed light on the relationship between functional diversification in hormonal signaling and the molecular evolution of hormone receptors. Copyright © 2017 John Wiley & Sons, Ltd.
Subject(s)
Arthropod Proteins/metabolism , Juvenile Hormones/agonists , Luciferases/metabolism , Aedes/genetics , Aedes/metabolism , Animals , Arthropod Proteins/genetics , Cell Line , Cloning, Molecular , Daphnia/genetics , Daphnia/metabolism , Drosophila melanogaster/genetics , Drosophila melanogaster/metabolism , Ligands , Male , Nuclear Receptor Coactivators/agonists , Signal Transduction , Tribolium/genetics , Tribolium/metabolismABSTRACT
Autosomal dominant polycystic kidney disease (ADPKD) is the most common inherited human renal disorder. Progressive enlargement of the kidneys is due to aberrant proliferation of the cyst epithelial cells, together with accumulation of fluid within the cyst cavities due to transepithelial fluid secretion. Multiple studies have suggested that fluid secretion across ADPKD cyst-lining cells is driven by the transepithelial secretion of chloride, mediated by the apical cystic fibrosis transmembrane conductance regulator chloride channel (CFTR) and specific basolateral transporters. Increased levels of cAMP, probably reflecting modifications in intracellular calcium homeostasis and abnormal stimulation of the vasopressin V2 receptor, in mutant renal epithelia, play an important role in the pathogenesis of ADPKD and contribute to both transepithelial secretion of fluid and proliferation of cyst epithelia. For example, cAMP activates the CFTR leading to the stimulation of Cl- secretion into the cyst lumen. This review focuses on the pathophysiology and molecular mechanism of fluid secretion in ADPKD cysts examined during pre-clinical trials of potentially useful drugs for the treatment of this condition.
Subject(s)
Chlorides/metabolism , Cyclic AMP/metabolism , Cystic Fibrosis Transmembrane Conductance Regulator/antagonists & inhibitors , Cysts/physiopathology , Epithelial Cells/metabolism , Polycystic Kidney, Autosomal Dominant/drug therapy , Polycystic Kidney, Autosomal Dominant/physiopathology , Receptors, Vasopressin/metabolism , Biomarkers/metabolism , Cystic Fibrosis Transmembrane Conductance Regulator/genetics , Epithelial Cells/drug effects , Evidence-Based Medicine , Humans , Hypoglycemic Agents/therapeutic use , Metformin/therapeutic use , Mutation/genetics , Nuclear Receptor Coactivators/agonists , Polycystic Kidney, Autosomal Dominant/genetics , Polycystic Kidney, Autosomal Dominant/metabolism , Receptors, Vasopressin/genetics , Treatment OutcomeABSTRACT
Peroxisome proliferator-activated receptor gamma (PPARγ) regulates metabolic homeostasis and is a molecular target for anti-diabetic drugs. We report here the identification of a steroid receptor ligand, RU-486, as an unexpected PPARγ agonist, thereby uncovering a novel signaling route for this steroid drug. Similar to rosiglitazone, RU-486 modulates the expression of key PPARγ target genes and promotes adipocyte differentiation, but with a lower adipogenic activity. Structural and functional studies of receptor-ligand interactions reveal the molecular basis for a unique binding mode for RU-486 in the PPARγ ligand-binding pocket with distinctive properties and epitopes, providing the molecular mechanisms for the discrimination of RU-486 from thiazolidinediones (TZDs) drugs. Our findings together indicate that steroid compounds may represent an alternative approach for designing non-TZD PPARγ ligands in the treatment of insulin resistance.
