MLL3/4-complexes in nuclear receptor-mediated metabolism

MLL3/4 复合物在核受体介导的代谢中的作用

• 批准号: 8723155
• 负责人: JAE W LEE
• 金额: $ 33.36万
• 依托单位: OREGON HEALTH & SCIENCE UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-08-20 至 2017-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8723155
• 关键词: Bile Acid Biosynthesis Pathway; Bile Acids; Biochemical; Biological Models; Cell membrane; Chromatin; Complex; Cyclic AMP; Defect; Dimensions; Dipeptidyl Peptidases; Down-Regulation; Energy Metabolism; Enzymes; Funding; Gene Expression; Gene Targeting; Genes; Genetic; Genetic Transcription; Glucose; Hepatic; Homeostasis; Iodothyronine Deiodinase; Knockout Mice; Ligands; Link; Liver; Lysine; Mediating; Metabolic; Metabolic Diseases; Metabolic syndrome; Metabolism; Methylation; Methyltransferase; Modeling; Molecular; Mus; Mutant Strains Mice; Names; Nuclear Receptors; Outcome Study; Pathway interactions; Peroxisome Proliferator-Activated Receptors; Phenotype; Physiological; Play; Recruitment Activity; Regulation; Role; Signal Pathway; Signal Transduction; Societies; Testing; Thyroid Hormones; Transactivation; Transcriptional Activation; Transgenic Mice; Up-Regulation; base; blood glucose regulation; chromatin immunoprecipitation; chromatin remodeling; drug development; genome-wide; glucagon-like peptide; improved; in vivo; insulin secretagogues; mutant; novel; pandemic disease; public health relevance; receptor; research study; response; tool; transcriptome sequencing

DESCRIPTION (provided by applicant): The homeostatic regulation of bile acid (BA) signaling requires a complex network of nuclear receptors (NRs), but their coactivators that remodel chromatin and regulate gene transcription in response to BA signaling are poorly understood. Our discovery of the NR coactivator ASC-2 led to our subsequent purification of 'ASC-2- complex' (ASCOM), the first mammalian complex that contains the H3 lysine 4 methyltransferase (H3K4MT) MLL3 or its paralogue MLL4. Later, ASCOM has also been found to contain the H3-lysine 27-demethylase (H3K27DM) UTX. Trimethylated H3K4 and trimethylated H3K27 mark transcriptionally active and inactive chromatin, respectively. Thus, ASCOM contains two types of enzymes that are linked to transcriptional activation. Excitingly, we found that the major physiological function of ASCOM is to regulate metabolism under a variety of different conditions primarily attributed by the ability of ASC-2 to recruit ASCOM to multiple metabolic NRs, including PPAR?, LXRs, and FXR, the NR for BAs. In particular, we discovered that ASCOM functions as a critical coactivator for FXR in regulating BA synthesis. Consistently, one of the most salient phenotypes of our MLL3 mutant mice was a significant increase in BA levels, suggesting that MLL3-mediated H3K4MT activity of ASCOM is essential for maintaining BA homeostasis. Intriguingly, our MLL3 mutant mice also displayed favorable metabolic profiles, which we propose is via defects in the ability of ASCOM to antagonize signaling by Tgr5, the plasma membrane receptor for BAs. Tgr5 triggers a signaling pathway that leads to upregulation of 'the cyclic-AMP-dependent thyroid hormone activating enzyme type 2 iodothyronine deiodinase' (D2) and to enhance secretion of glucagon-like peptide-1 (GLP-1), an insulin secretagogue, thereby resulting in enhanced energy expenditure and improved glucose homeostasis. Our preliminary results suggest that ASCOM inhibits Tgr5 signaling not only through decreasing BA levels but also directly through the regulation of a gene encoding a key modifier of Tgr5 signaling, 'dipeptidyl peptidase-4' (Dpp4), which inactivates GLP-1. Together, these results support the central hypothesis of this study: ASCOM functions as a master coactivator of 'the homeostatic regulation of BA signaling' by controlling the expression of genes in multiple pathways that regulate BA metabolism and signaling. This renewal has two objectives: 1) We will test the mechanisms of action for ASCOM in NR transactivation (primarily for FXR and RAR) by using the discoveries made during the previous funding period. 2) By focusing specifically on the role of ASCOM in BA homeostasis, we will establish a new paradigm for understanding the diverse metabolic roles of ASCOM. This is a well-integrated study, as the first part of the study is critical to understand the molecular basis for the functio of ASCOM in BA homeostasis and signaling (the second part of the study). We will tackle these two issues in three specific aims, utilizing a combination of biochemical, cellular and genetic approaches. This study will help us to understand the molecular basis for how NRs regulate transcription and metabolism.

描述（由申请人提供）：胆汁酸（BA）信号传导的体内调节需要复杂的核受体网络（NRS），但是它们的共激活因子重塑染色质和对BA信号的响应而调节基因转录的共激活剂对BA信号传导的理解很差。我们发现NR共激活剂ASC-2导致我们随后纯化“ ASC-2-复合物”（ASCOM），这是第一个包含H3赖氨酸4甲基转移酶（H3K4MT）MLL3或其副伙伴MLL4的哺乳动物复合物。后来，还发现ASCOM包含H3-赖氨酸27-甲基酶（H3K27DM）UTX。三甲基化的H3K4和三甲基化的H3K27分别具有转录活性和非活性染色质。因此，ASCOM包含两种与转录激活相关的酶。令人兴奋的是，我们发现ASCOM的主要生理功能是在多种不同条件下调节代谢，主要由ASC-2募集ASCOM到多个代谢NR的能力，包括PPAR？，LXR？，LXRS和FXR，fxr，NR，bas的NR。特别是，我们发现ASCOM充当FXR调节BA合成的关键共激活因子。一致地，我们的MLL3突变小鼠最显着的表型之一是BA水平的显着增加，这表明MLL3介导的ASCOM的H3K4MT活性对于维持BA稳态至关重要。有趣的是，我们的MLL3突变小鼠也表现出有利的代谢谱，我们提出的是通过ASCOM对bas的质膜受体TGR5拮抗信号传导的能力的缺陷。 TGR5触发了一种信号通路，该信号通路会导致“环状AMP依赖性甲状腺激素激活酶2型碘甲醇脱碘酶”（D2）'（D2），并增强胰高血糖素肽-1（GLP-1）（GLP-1）的分泌，胰岛素分泌能量，从而增强了胰岛素延迟，并提高了良好的效果。我们的初步结果表明，ASCOM不仅通过降低BA水平抑制TGR5信号传导，而且直接通过调节编码TGR5信号传导“二肽基肽酶-4”（DPP4）的基因（DPP4），这使GLP-1失活。这些结果共同支持了这项研究的中心假设：ASCOM充当“ BA信号的体内调节调节”的主要共激活因子，通过控制调节BA代谢和信号传导的多种途径中的基因表达。该更新有两个目标：1）我们将使用上一个资金期间的发现来测试NR反式激活中ASCOM的作用机理（主要用于FXR和RAR）。 2）通过专门关注ASCOM在BA稳态中的作用，我们将建立一个新的范式，以了解ASCOM的各种代谢角色。这是一项良好的研究，因为研究的第一部分对于了解ASCOM在BA稳态和信号传导（研究的第二部分）中的分子基础至关重要。我们将利用生化，细胞和遗传方法的结合来解决这两个问题的这两个问题。这项研究将帮助我们了解NRS如何调节转录和代谢的分子基础。