Understanding the origins and mechanisms of aryl hydrocarbon receptor promiscuity

了解芳烃受体混杂的起源和机制

• 批准号: 10679532
• 负责人: Mark E Hahn
• 金额: $ 51.1万
• 依托单位: WOODS HOLE OCEANOGRAPHIC INSTITUTION
• 依托单位国家: 美国
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-03-09 至 2027-12-31
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/10679532
• 关键词: Address; Agonist; Allosteric Regulation; Amino Acid Sequence; Amino Acids; Animals; Aromatic Hydrocarbons; Aromatic Polycyclic Hydrocarbons; Aryl Hydrocarbon Receptor; Basic Science; Binding; Biological Process; Cell Differentiation process; Chemicals; Chordata; Circadian Rhythms; Dependence; Development; Dietary Phytochemical; Dioxins; Disease; Docking; Embryonic Development; Engineering; Environmental Exposure; Environmental Pollutants; Enzymes; Etiology; Eukaryota; Evolution; Exposure to; Family; Foundations; Genetic; Goals; Helix-Turn-Helix Motifs; Hematopoiesis; Hypoxia Inducible Factor; Immunity; Inflammatory; Invertebrates; Laboratories; Ligand Binding; Ligands; Malignant Neoplasms; Mediating; Modernization; Molecular; Mutate; Mutation; NPAS4 gene; Natural Products; Nuclear Receptors; Organ; Phylogenetic Analysis; Physiological; Physiological Processes; Physiology; Play; Polychlorinated Biphenyls; Process; Property; Proteins; Regulation; Research; Role; Sampling; Sensitivity and Specificity; Signal Transduction; Specificity; Statistical Methods; Structure; Testing; Tetrachlorodibenzodioxin; Time; Toxic effect; Transcriptional Activation; Trees; Tryptophan; Vertebrates; Work; Xenobiotics; anthropogenesis; aryl hydrocarbon receptor ligand; candidate identification; exposed human population; gut microbiome; halogenation; host microbiome; immune function; innovation; insight; member; microbial; microbiome; molecular modeling; receptor; receptor function; reconstruction; response; sensor; single-minded protein; transcription factor

Project Summary/Abstract The aryl hydrocarbon receptor (AHR) is a bHLH-PAS protein that in vertebrate animals is a ligand-activated transcription factor that plays essential roles in the regulation of xenobiotic-metabolizing enzymes and in the mechanisms of toxicity of numerous environmental contaminants, including chlorinated dioxins such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), some polychlorinated biphenyls (PCBs), polynuclear aromatic hydrocarbons (PAHs), and some emerging contaminants. The AHR is also involved in a variety of physiological processes including development, hematopoiesis, immunity, host-microbiome interactions, and barrier organ function. In contrast to most ligand-activated transcription factors that have narrow ligand- specificity, the vertebrate AHR is highly promiscuous, recognizing a diverse array of chemicals. In addition to the well-known xenobiotics, AHR ligands include dietary phytochemicals, microbiome-derived microbial metabolites, and endogenous metabolites such as tryptophan catabolites, all of which collectively contribute to the internal chemical exposome. A comprehensive mechanistic understanding of AHR’s role in the response to environmental exposures has been hindered by the complexity of its physiological functions and the bewildering diversity of its ligands. Here, we propose a set of innovative molecular studies to elucidate the sequence-structure-function determinants of AHR ligand-dependence and the origin of its ligand diversity. Evidence suggests that the AHR evolved from a ligand-independent (constitutively active) ancestor. The proposed basic research will experimentally determine the evolutionary trajectory and underlying genetic and structural mechanisms that drove the evolution of AHR ligand-dependence and promiscuity. In Aim 1, we will establish the ligand-specificity of AHRs from present-day species through a systematic experimental assessment of phylogenetically diverse metazoan AHRs, including new invertebrate and early vertebrate AHRs. In Aim 2, we will use ancestral sequence reconstruction (ASR) to “resurrect” ancestral AHR proteins and then determine their ligand-binding sensitivity and specificity, revealing the identities of ancestral and derived ligands. In Aim 3, we will use phylogenetic and protein structural analysis to identify candidate historical amino acid changes that caused the acquisition of ligand-binding and evolution of promiscuity. We will test these hypotheses by engineering ancestral and extant proteins containing these substitutions and experimentally assessing their function. Understanding the ancestral properties of the primordial ligand- activated AHR and the mechanisms that drove the evolution of promiscuity will provide essential new insights into the natural physiological ligands and biological functions of extant AHR, reveal the genetic and structural mechanisms underlying AHR ligand recognition, and elucidate how and why AHR function is disrupted by anthropogenic environmental contaminants.

项目总结/摘要 芳香烃受体（AHR）是一种bHLH-PAS蛋白，在脊椎动物中是一种配体激活的受体。 一种在外源性物质代谢酶的调节和代谢过程中起重要作用的转录因子。 许多环境污染物的毒性机制，包括氯化二恶英， 2，3，7，8-四氯二苯并对二恶英（TCDD）、某些多氯联苯（PCB）、多核芳香族化合物 碳氢化合物（PAHs）和一些新出现的污染物。AHR还参与了各种 生理过程，包括发育、造血、免疫、宿主-微生物组相互作用，以及 屏障器官功能与大多数配体激活的转录因子相比， 脊椎动物AHR是高度混杂的，识别各种各样的化学物质。除了 众所周知的异生物质、AHR配体包括膳食植物化学物质、微生物组衍生的微生物 代谢物和内源性代谢物如色氨酸催化剂，所有这些共同有助于 内部化学问题。对AHR在应对以下疾病中的作用的全面机制性理解 环境暴露受到其生理功能复杂性的阻碍， 配体的多样性令人眼花缭乱。在这里，我们提出了一套创新的分子研究，以阐明 AHR配体依赖性的序列-结构-功能决定因素及其配体多样性的起源。 有证据表明，AHR是从一个配体独立的（组成型活性）祖先进化而来的。的 拟议的基础研究将通过实验确定进化轨迹和潜在的遗传和 驱动AHR配体依赖性和滥交进化的结构机制。在目标1中，我们 建立配体特异性的AHRs从今天的物种，通过系统的实验 评估遗传多样性后生动物AHR，包括新的无脊椎动物和早期脊椎动物 AHR在目标2中，我们将使用祖先序列重建（ASR）来“复活”祖先AHR蛋白 然后确定它们的配体结合敏感性和特异性，揭示祖先和 衍生配体。在目标3中，我们将使用系统发育和蛋白质结构分析来鉴定候选蛋白质。 导致配体结合获得和滥交进化的历史氨基酸变化。我们 将通过工程改造含有这些取代的祖先和现存蛋白质来测试这些假设， 实验性地评估它们的功能。了解原始配体的祖先特性- 激活的AHR和驱动滥交进化的机制将提供重要的新见解 研究了现存AHR的天然生理配体和生物学功能，揭示了AHR的遗传和结构特征， AHR配体识别的潜在机制，并阐明如何以及为什么AHR功能被破坏 人为环境污染物。