Novel ARNT-mediated Regulatory Paradigm of AHR Signaling

新型 ARNT 介导的 AHR 信号调节范式

• 批准号: 9477928
• 负责人: Casey W Wright
• 金额: $ 34.88万
• 依托单位: UNIVERSITY OF TEXAS MED BR GALVESTON
• 依托单位国家: 美国
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-06-01 至 2021-05-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9477928
• 关键词: ARNT gene; Affect; Affinity; Alternative Splicing; Amino Acids; Antigen-Presenting Cells; Aromatic Hydrocarbons; Aryl Hydrocarbon Receptor; Autoimmune Diseases; Autoimmune Process; Binding; CD4 Positive T Lymphocytes; CRISPR/Cas technology; Cancer Cell Growth; Cells; Cellular biology; Complex; Cytoplasmic Receptors; DNA; Data; Development; Diet; Dioxins; EMSA; Enhancers; Environmental Pollution; Event; Exhibits; Future; Gatekeeping; Gene Targeting; Genetic Transcription; Goals; Hematopoiesis; Immune; Immune Tolerance; Immune signaling; Immunotherapy; Individual; Knock-out; Laboratories; Lentivirus Vector; Ligand Binding; Ligands; Light; Lymphocyte; Lymphoma; Malignant Neoplasms; Malignant lymphoid neoplasm; Mediating; Molecular; Mus; Mutate; NF-kappa B; Nuclear; Nuclear Translocation; Organ; Outcome; Phosphorylation; Phosphorylation Site; Physiological; Process; Protein Isoforms; RNA Polymerase II; RNA Splicing; Receptor Signaling; Recruitment Activity; Regulation; Research; Role; Signal Pathway; Signal Transduction; Sum; System; T cell differentiation; T-Lymphocyte; Techniques; Testing; Tetrachlorodibenzodioxin; Tissues; Toxic Environmental Substances; Transactivation; Transgenic Mice; Tryptophan; Work; Xenobiotics; aryl hydrocarbon receptor ligand; base; cell growth; cell type; chromatin immunoprecipitation; cofactor; experimental study; immunoregulation; in vivo; innovation; mouse model; mutant; novel; prevent; public health relevance; receptor binding; receptor function; receptor-mediated signaling; reconstitution; response; therapy development; transcription factor

 DESCRIPTION (provided by applicant): AHR is a cytoplasmic receptor that has affinity for numerous xenobiotic ligands, which include halogenated aromatic hydrocarbons such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), one of the most potent AHR activators, and AHR signaling mediates the detrimental effects of environmental contaminants on body tissues and organs. Ligand binding induces nuclear translocation of AHR and interaction with the AHR binding partner, aryl hydrocarbon receptor nuclear translocator (ARNT), allowing recognition of specific DNA enhancer sequences. More recently endogenous and natural AHR ligands, such as tryptophan metabolites and dietary compounds, have been identified. These ligands induce AHR-mediated immunomodulatory effects such as controlling normal T cell differentiation and immune tolerance. However, little is known about the role of ARNT in AHR immune signaling. Initial studies by our laboratory, and others, into the regulatory role of ARNT in AHR-mediated immunomodulation have suggested that ARNT is an integral cofactor in different immune signaling pathways, including AHR and NF-κB signaling. ARNT is often described in AHR signaling as a constitutively expressed, non-regulated, nuclear binding partner for AHR. However, our data challenge this assumption and show that the actual regulatory paradigm is more intricate. For instance, ARNT is expressed as two isoforms, isoform 1 and 3, which differ in only 15 amino acids present in isoform 1. Despite their sequence similarity, we have found that the ARNT isoforms appear to have opposing functions in AHR signaling. Intriguingly, the extra 15 amino acids in isoform 1 include a unique phosphorylation site, where we have observed TCDD-induced phosphorylation. Furthermore, we find that the phosphorylation of ARNT isoform 1 is crucial for the recruitment of RNA polymerase II and transactivation of AHR/ARNT target genes. We predict that ARNT activity is a function of both unique phosphorylation of isoform 1 and the given isoform ratio within a particular cell type, which in turn is likely important for regulating the magnitude/outcome of the AHR response. To investigate our hypothesis we propose to 1) Define a comprehensive molecular framework for AHR regulation by the ARNT isoforms, 2) Examine the role of AHR activity, as governed by the ARNT isoforms, in lymphoma cell growth, and 3) Characterize the regulation of AHR signaling by ARNT isoforms in vivo. Ultimately, these studies will lay the groundwork for ARNT-based therapies such as splice modulation as a means of manipulating the ARNT isoforms to control AHR signaling in autoimmune diseases and cancer.

 描述（由申请人提供）：AHR 是一种细胞质受体，对多种外源配体具有亲和力，其中包括卤代芳香烃，如 2,3,7,8-四氯二苯并-对二恶英 (TCDD)，它是最有效的 AHR 激活剂之一，AHR 信号传导介导环境污染物对身体组织和器官的有害影响。配体结合诱导 AHR 的核转位以及与 AHR 结合伴侣、芳基烃受体核转位子 (ARNT) 的相互作用，从而识别特定的 DNA 增强子序列。最近，已鉴定出内源性和天然 AHR 配体，例如色氨酸代谢物和膳食化合物。这些配体诱导 AHR 介导的免疫调节作用，例如控制正常 T 细胞分化和免疫耐受。然而，人们对 ARNT 在 AHR 免疫信号传导中的作用知之甚少。我们实验室和其他人对 ARNT 在 AHR 介导的免疫调节中的调节作用的初步研究表明，ARNT 是不同免疫信号通路（包括 AHR 和 NF-κB 信号通路）中不可或缺的辅助因子。 ARNT 在 AHR 信号传导中通常被描述为 AHR 的组成型表达、非调控的核结合伴侣。然而，我们的数据挑战了这一假设，并表明实际的监管范式更加复杂。例如，ARNT 表达为两种异构体，即异构体 1 和 3，它们仅在异构体 1 中存在 15 个氨基酸上存在差异。尽管它们的序列相似，但我们发现 ARNT 异构体在 AHR 信号传导中似乎具有相反的功能。有趣的是，异构体 1 中额外的 15 个氨基酸包括一个独特的磷酸化位点，我们在该位点观察到 TCDD 诱导的磷酸化。此外，我们发现 ARNT 亚型 1 的磷酸化对于 RNA 聚合酶 II 的募集和 AHR/ARNT 靶基因的反式激活至关重要。我们预测 ARNT 活性是亚型 1 的独特磷酸化和特定细胞类型内给定亚型比率的函数，这反过来可能对于调节 AHR 反应的幅度/结果很重要。为了研究我们的假设，我们建议 1) 定义 ARNT 同工型对 AHR 调节的综合分子框架，2) 检查由 ARNT 同工型控制的 AHR 活性在淋巴瘤细胞生长中的作用，以及 3) 表征体内 ARNT 同工型对 AHR 信号传导的调节。最终，这些研究将为基于 ARNT 的疗法奠定基础，例如剪接调节作为操纵 ARNT 同工型以控制自身免疫性疾病和癌症中的 AHR 信号传导的手段。