PPARgamma as an architectural regulator of gene expression in endocrine signaling

PPARgamma 作为内分泌信号中基因表达的结构调节剂

• 批准号: 9751850
• 负责人: Laszlo Nagy
• 金额: $ 40.94万
• 依托单位: JOHNS HOPKINS UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2018
• 资助国家: 美国
• 起止时间: 2018-08-01 至 2022-05-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9751850
• 关键词: 3-Dimensional; Adipocytes; Alveolar Macrophages; Animals; Architecture; Atherosclerosis; Binding Sites; Bioinformatics; Biology; Blinded; Cell Differentiation process; Cell model; Cells; Cellular biology; Cholesterol; Chromatin; Chromatin Structure; Chronic; Collaborations; Complex; DNA Binding; Data; Dendritic Cells; Disease; Elements; Endocrine; Enhancers; Expression Profiling; Fatty Acids; Fibrinogen; Gene Expression; Genes; Genetic Transcription; Genome; Genomics; Human body; Immune system; Inflammation; Inflammatory; Inflammatory Response; Influenza; Interleukin-4; Laboratories; Learning; Ligand Binding; Ligands; Link; Lipids; Lung; Mediating; Memory; Metabolic Diseases; Metabolism; Methods; Modeling; Molecular Biology; Myeloid Cells; Nuclear Hormone Receptors; PPAR gamma; Pathway interactions; Physiological; Play; Process; Prostaglandins; Proteins; RXR; Regulator Genes; Research; Role; STAT6 gene; Signal Transduction; Testing; Tissues; Transactivation; Transcriptional Regulation; Virus Diseases; Work; cell type; cohesin; dimer; epigenome; epigenomics; gain of function; genome-wide; genome-wide analysis; in vivo; inflammatory milieu; influenzavirus; insulin sensitivity; interest; knockout animal; loss of function; macrophage; mutant; overexpression; programs; promoter; receptor; receptor binding; receptor function; research study; response; tissue regeneration; tissue repair; transcription factor; uptake

PROJECT SUMMARY The canonical view of Nuclear Hormone Receptors (NHRs) is that these are ligand-activated transcription factors acting as DNA-bound, lipid-controlled genomic switches. A group of NHRs are acting as heterodimers with the obligate heterodimeric partner Retinoid X Receptor (RXR). One of the key partners of RXR is the Peroxisome Proliferator-Activated Receptor gamma (PPAR). PPAR is viewed as a modified fatty acid and prostanoid regulated transcription factor essential for fat cell differentiation and contributing to lipid metabolite induced transcriptional regulation in many cell types including macrophages. Using traditional ligand centric approaches, we and others were able to identify PPAR target genes and ligand regulated processes including cholesterol uptake and efflux, inhibition of inflammatory responses, regulating insulin sensitivity and promoting tissue repair in macrophages cells. These findings make this receptor a key endocrine regulator of metabolism and inflammation in this cell type. A major weakness of prior research was that it focused solely on ligand- dependent activities of the receptors and did not consider ligand-independent ones. Therefore, there is a substantial gap in our understanding of receptor biology and action. Recent genome-wide determinations of binding sites identified at least two orders of magnitude more genomic binding sites in fat cells and macrophages as regulated genes would necessitate. This prompted us to explore PPAR:RXR cistromes in alternatively polarized macrophages. We have gathered preliminary evidence to suggest that (1) The macrophage PPARγ:RXR cistrome is greatly extended upon IL-4 polarization directed by STAT6; (2) Chromatin-bound PPARγ is predominantly ligand-insensitive in alternatively polarized macrophages; (3) PPARγ:RXR heterodimers are architectural elements of the genome, and (4) the heterodimer confers transcriptional memory via retained gene-enhancer looping. This allows us to formulate new hypotheses as follows: A large fraction of PPAR:RXR heterodimers is ligand-insensitive; (a) Contributing to the epigenome of IL-4 polarized macrophages and provides links between enhancers and promoters via looping utilizing the cohesin complex and/or CTCF; (b) Establishes transcriptional cellular memory and (C) Contributes to macrophage tissue-specification and transcriptional adaptation. We are proposing to test these at three levels. At the chromatin and genome folding level we will determine the epigenomic roles for PPAR. At the cellular level we will determine the role PPAR plays in opening of chromatin and transcriptional memory. Finally at the in vivo level, contribution of PPAR to lung macrophage function and response to viral infection will be explored. The results will likely open up new avenues of research into the epigenomic programming of macrophages with translational potential in chronic inflammatory and metabolic disease and tissue regeneration.

项目摘要 核激素受体（NHRs）的经典观点是，它们是配体激活的转录 作为DNA结合，脂质控制的基因组开关的因子。一组NHR作为异二聚体 视黄酸X受体（Retinoid X Receptor，RXR）RXR的主要合作伙伴之一是 过氧化物酶体增殖物激活受体γ（PPAR-A）。PPAR γ被认为是一种修饰的脂肪酸， 前列腺素类调节转录因子对脂肪细胞分化和脂质代谢至关重要 在包括巨噬细胞在内的许多细胞类型中诱导转录调节。使用传统的配体中心 方法，我们和其他人能够识别PPAR γ靶基因和配体调控的过程，包括 胆固醇摄取和流出，抑制炎症反应，调节胰岛素敏感性和促进 巨噬细胞的组织修复。这些发现使这种受体成为代谢的关键内分泌调节因子 和炎症。先前研究的一个主要弱点是它只关注配体- 受体的依赖性活动，不考虑配体非依赖性活动。因此有 我们对受体生物学和作用的理解存在巨大差距。最近的全基因组测定 在脂肪细胞中，结合位点识别出至少两个数量级以上的基因组结合位点， 巨噬细胞作为受调控的基因将是必要的。这促使我们探索PPAR γ：RXR顺反系统， 交替极化的巨噬细胞。我们已经收集了初步证据，表明（1） 巨噬细胞PPARγ：RXR顺式组在由STAT 6指导的IL-4极化后大大扩展;（2） 染色质结合的PPARγ在交替极化的巨噬细胞中主要是配体不敏感的;（3） PPARγ：RXR异二聚体是基因组的结构元件，并且（4）异二聚体赋予 转录记忆通过保留基因增强子环。这使我们能够提出新的假设， 以下：大部分的PPAR γ：RXR异二聚体是配体不敏感的;（a）有助于表观基因组， IL-4极化巨噬细胞，并通过利用巨噬细胞中的蛋白质形成环，在增强子和启动子之间提供连接。 粘附素复合物和/或CTCF;（B）增强转录细胞记忆和（C）有助于 巨噬细胞组织特异性和转录适应。我们建议在三个层次上进行测试。 在染色质和基因组折叠水平，我们将确定表观基因组的作用，为过氧化物酶体增殖物激活受体。在细胞 水平，我们将确定的作用，过氧化物酶体增殖物激活物激活物在开放的染色质和转录记忆。最后在 在体内水平，将探索PPAR γ对肺巨噬细胞功能和对病毒感染反应的贡献。 这些结果可能会为巨噬细胞的表观基因组编程开辟新的研究途径， 在慢性炎症和代谢性疾病以及组织再生中的翻译潜力。