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Structure of the Ancestral Glucocorticoid Receptor 2 ligand binding domain in complex with dexamethasone and PGC1a coregulator fragment
Structural highlights
FunctionPRGC1_HUMAN Transcriptional coactivator for steroid receptors and nuclear receptors. Greatly increases the transcriptional activity of PPARG and thyroid hormone receptor on the uncoupling protein promoter. Can regulate key mitochondrial genes that contribute to the program of adaptive thermogenesis. Plays an essential role in metabolic reprogramming in response to dietary availability through coordination of the expression of a wide array of genes involved in glucose and fatty acid metabolism.[1] [2] [3] Publication Abstract from PubMedBoth synthetic and endogenous glucocorticoids are important pharmaceutic drugs known to bind to the ligand-binding domain (LBD) of glucocorticoid receptor (GR), a member of the nuclear receptor (NR) superfamily. Ligand binding induces conformational changes within GR, resulting in subsequent DNA binding and differential coregulator recruitment, ultimately activating or repressing target gene expression. One of the most crucial coregulators is peroxisome proliferator-activated gamma coactivator 1-alpha (PGC1alpha), which acts to regulate energy metabolism by directly interacting with GR to modulate gene expression. However, the mechanisms through which PGC1alpha senses GR conformation to drive transcription are not completely known. Here, an ancestral variant of the GR (AncGR2) LBD was used as a tool to produce stable protein for biochemical and structural studies. PGC1alpha is found to interact more tightly and form a more stable complex with AncGR2 LBD than nuclear receptor coactivator 2. We report the first high-resolution X-ray crystal structures of AncGR2 LBD in complex with PGC1alpha and dexamethasone (DEX) or hydrocortisone (HCY). Structural analyses reveal how distinct steroid drugs bind to GR with different affinities by unique hydrogen bonds and hydrophobic interactions. Important charge clamps are formed between the activation function 2 and PGC1alpha to mediate their specific interactions. These interactions lead to a high level of protection from hydrogen-deuterium exchange at the coregulator interaction site and strong intramolecular allosteric communication to ligand binding site. This is the first structure detailing the GR-PGC1alpha interaction providing a foundation for future design of specific therapeutic agents targeting these critical metabolic regulators. SIGNIFICANCE STATEMENT: High-resolution structures of AncGR2 LBD bound to DEX and HCY in complex with PGC1alpha reveal the molecular mechanism of PGC1alpha binding to AncGR2 LBD as well as the distinct affinities between DEX and HCY binding. Identifying the structural mechanisms that drive drug affinity is of pharmacologic interest to the glucocorticoid receptor field as an avenue to guide future drug design targeting GR-PGC1alpha signaling, which plays a crucial role in controlling hepatic glucose output. First High-Resolution Crystal Structures of the Glucocorticoid Receptor Ligand-Binding Domain-Peroxisome Proliferator-Activated gamma Coactivator 1-alpha Complex with Endogenous and Synthetic Glucocorticoids.,Liu X, Wang Y, Ortlund EA Mol Pharmacol. 2019 Oct;96(4):408-417. doi: 10.1124/mol.119.116806. Epub 2019 Aug, 7. PMID:31391291[4] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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