Project description:Cofactors interacting with PPARγ can regulate adipogenesis and adipocyte metabolism by modulating the transcriptional activity and selectivity of PPARγ signaling. ZFP407 was previously demonstrated to regulate PPARγ target genes such as GLUT4, and its overexpression improved glucose homeostasis in mice. Here, using a series of molecular assays, including protein-interaction studies, mutagenesis, and ChIP-seq, ZFP407 was found to interact with the PPARγ/RXRα protein complex in the nucleus of adipocytes. Consistent with this observation, ZFP407 ChIP-seq peaks significantly overlapped with PPARγ ChIP-seq peaks, with more than half of ZFP407 peaks overlapping with PPARγ peaks. Transcription factor binding motifs enriched in these overlapping sites included CTCF, RARα/RXRγ, TP73, and ELK1, which regulate cellular development and function within adipocytes. Site-directed mutagenesis of frequent PPARγ phosphorylation or SUMOylation sites did not prevent its regulation by ZFP407, while mutagenesis of ZFP407 domains potentially necessary for RXR and PPARγ binding abrogated any impact of ZFP407 on PPARγ activity. These data suggest that ZFP407 controls the activity of PPARγ, but does so independently of post-translational modifications, likely by direct binding, establishing ZFP407 as a newly identified PPARγ cofactor. In addition, ZFP407 ChIP-seq analyses identified regions that did not overlap with PPARγ peaks. These non-overlapping peaks were significantly enriched for the transcription factor binding motifs of TBX19, PAX8, HSF4, and ZKSCAN3, which may contribute to the PPARγ-independent functions of ZFP407 in adipocytes and other cell types.
Project description:Retinoid X receptor alpha (RXRα) is a ligand-activated nuclear receptor involved in the regulation of retinoid metabolism. RXRα activation by agonist bexarotene can significantly induce hepatomegaly and promote liver regeneration after 70% partial hepatectomy (PHx) in wild type mice, while these effects were abolished in liver-specific RXRα-knockout mice. However, the underlying mechanisms remain unclear. Our findings reveal that RXRα activation promotes liver proliferation through transactivation of Cyclin D1. These data raise some key questions for understanding the manipulation of liver size and liver regeneration by RXRα agonists.
Project description:Sepsis is a life-threatening condition where a dysregulated host response to infection causes organ dysfunction and the collapse of metabolic and immune functions. Here, we identify hepatocyte Retinoid X Receptor α (RXRα) as a central integrator of host resilience during polymicrobial sepsis. We show that hepatic Rxra expression is transcriptionally dependent on the upstream regulator Hepatocyte Nuclear Factor 4 α (HNF4α), and that sepsis rapidly suppresses RXRα abundance at both the mRNA and protein levels. Transcriptomic profiling further reveals that the septic liver develops partial resistance to pharmacological RXR activation by its agonist Bexarotene (Bex). Despite this, prophylactic treatment with Bex preserves metabolic stability, enhances bacterial clearance, and improves survival. Using hepatocyte-specific inducible RXRα-deficient mice (RXRαiAlbKO), we demonstrate that this protective effect is strictly dependent on hepatocyte RXRα. Mechanistically, the loss of RXRα in hepatocytes leads to a profound reduction in the liver-resident macrophage, Kupffer cells (KC), resulting in uncontrolled bacterial dissemination and increased mortality. This defect is phenocopied by selective KC depletion. These findings establish that hepatocyte RXRα is essential for maintaining the hepatic macrophage niche, thereby linking hepatocellular transcriptional competence to systemic antibacterial defense.
Project description:In this dataset, we present ChIP-seq profiling of RXRα in proliferating C2C12 myoblasts, which serves as an extension of Series GSE94558. The overall data provides genome-wide occupancy of RXRα in normal myoblast proliferation.
Project description:The peroxisome proliferator-activated receptor γ (PPARγ) is the master regulator of adipocyte differentiation, and mutations that interfere with PPARγ function cause lipodystrophy. Structural studies indicate that PPARγ domains engage in several intra- and inter-moleuclar interactions; however, how these interactions modulate the ability of PPARγ to activate target genes in a cellular context is currently poorly understood. Here we analysed the transcriptional potential of R212Q and E379K two previously uncharacterised lipodystrophy-associated PPARγ mutants that are located in distinct PPARγ domains but are both predicted to affect intermolecular interactions. Using a combination of biochemical and genome-wide approaches we show that these mutations impair binding to an overlapping subset of enhancers that are less accessible and specifically require PPARγ for chromatin remodeling. Based on these findings we propose a model in which recruitment of PPARγ to chromatin is determined by several intermolecular interfaces. Furthermore, our data exemplify that relatively subtle molecular defects in transcription factors are sufficient to significantly affect enhancer binding and thereby transcriptional output.
Project description:Purpose: To explore whether the differences in chromatin occupancy of RXRα correlate with distinct gene expression in PTCs of MI and SI Methods: Proximal tubules were isolated for RXRα ChIP-seq Results: Using an optimized data analysis workflow, we mapped reads to the mouse genome (mm10). Conclusions: We mapped the chromatin occupancy of RXRα.
Project description:Hepatic stellate cells (HSCs) represent a dominant fibrogenic cell population in the liver, whose activation is a key event in the development and progression of hepatic fibrosis. We report here that retinoid X receptor-alpha (RXRα), a unique member of the nuclear receptor superfamily, is a critical modulator of HSC activation and liver fibrosis through its regulation of calcium/calmodulin-dependent protein kinase kinase β (CaMKKβ)-mediated activation of AMP-activated protein kinase-alpha (AMPKα). K-80003, which binds RXRα by a unique mechanism, effectively inhibits the activation, proliferation and migration of HSCs and inhibits liver fibrosis in the CCl4 and AMLN animal models by AMPKα activation, which promotes mitophagy in HSCs. Mechanistically, K-80003 activation of AMPKα requires its induction of RXRα formation of condensates with CaMKKβ and AMPKα via a two-phase mechanism. The formation of RXRα condensates is mediated by the N-terminal intrinsically disorder region of RXRα and is dependent on its phosphorylation by CaMKKβ. Our results therefore unravel an important RXRα-CaMKKβ-AMPKα axis in the modulation of HSC activation through phase separation and identify K-80003 as a potent inhibitor of HSC activation and liver fibrosis by targeting the axis.