Mechanistic Studies of Ligand-Regulated Nuclear Receptor RXR Activity

描述（由申请人提供）：我们的研究目标是利用x射线晶体学结合多学科分子和生化方法揭示核受体作用的分子基础。核受体类视黄醇X受体（RXRs）是配体激活的转录调节因子，广泛参与人体生理，包括发育和代谢。rxr是公认的药物靶点。然而，RXR配体的临床使用显然受到毒性等副作用的影响，这可能与它们的低选择性和亲和力以及与RXR的其他功能的交叉反应性有关。为了了解配体介导的RXR信号在人体生理学中的分子基础，我们计划确定RXR多结构域片段与靶基因DNA应答片段结合的晶体结构。在结构确定之后，我们将进行突变研究、生化分析和基于细胞的转录分析，以确认关键结构元件的功能意义。本研究将揭示RXRs及其配体在关键调控步骤（从配体结合到靶基因识别）中功能特异性的分子基础。这些结构见解将为基于结构的药物发现提供一个合理的模板，这些药物发现具有高选择性和高效的RXR配体，并且副作用小，可用于人类疾病的治疗。此外，本项目生成的结构将作为研究其他核受体家族成员的配体依赖性调控的模型。公共卫生相关性：本提案通过提供与其靶基因结合的多结构域类视黄醇X受体的三维结构，解决了当前核受体研究中的一个关键需求。结构和功能研究将揭示如何进一步提高药物特异性和亲和力的详细信息，从而为合理发现药物，有效治疗人类代谢性疾病等疾病提供基础。

DESCRIPTION (provided by applicant): The goal of our research is to unravel the molecular basis of the nuclear receptor actions using X-ray crystallography in conjunction with multidisciplinary molecular and biochemical approaches. The nuclear receptor retinoid X receptors (RXRs) are key ligand-activated transcriptional regulators involved in a wide range of human physiology, including development and metabolism. RXRs are well-established drug targets. However, the clinical use of RXR ligands is clearly tempered by side effects like toxicity, possibly associated with their low selectivity and affinity and also the cross-reactivity with other functions of RXRs. To understand the molecular basis of ligand-mediated signaling of RXRs in human physiology, we are planning to determine the crystal structures of a RXR multi-domain fragment bound to a DNA response fragment of their target genes. Following structure determination, we will perform mutational studies, biochemical analysis, and cell-based transcriptional assays to confirm functional significance of key structure elements. This study will reveal the molecular basis of the functional specificity of RXRs and its ligands at key regulatory steps: from ligand binding and to target gene recognition. The structural insights will provide a rational template for structure-based drug discovery of highly selective and efficient RXR ligands with reduced side effects for the therapeutic use in human disease. Moreover, the structure generated in this project will serve as a model to study the ligand-dependent regulation of other nuclear receptor family members. PUBLIC HEALTH RELEVANCE: This proposal addresses a critical need in the current nuclear receptor research by providing three-dimensional structures of the multi-domain retinoid X receptor bound to its target genes. The structural and functional studies will reveal detailed insights on how drug specificity and affinity can be further improved, thus providing a foundation for rational drug discovery for effective treatment of human disease like metabolic disease.