Structural Genomics of Orphan Nuclear Receptors

描述（由申请人提供）：核受体（NR）包括48个转录因子家族，这些转录因子是开启或关闭基因的调节蛋白。与其他转录因子相反，NR的活性由小分子（配体）生理调节，包括性激素、糖皮质激素、维生素、脂质等，这使得这些蛋白质适于药理学干预以治疗许多疾病，包括炎症、癌症和糖尿病。因此，NR代表了治疗药物发现靶标的最成功类别之一。孤儿NR是在首次鉴定时不知道其生理配体的受体。这组NR仍然具有巨大的医学意义，因为它们的生理作用以及小分子和药物的可能调节仍在出现。本研究的目的是确定剩余的孤儿NR配体结合域（LBD）的高分辨率晶体结构，将这些受体的结构与生物学功能相关联，并探索靶向这些受体的药物发现的结构信息。所有的核受体都至少含有 两个保守结构域之一：位于中心的DNA结合结构域（DBD）和C-末端LBD。LBD是介导配体结合、受体二聚化、配体调控核受体转录功能的关键功能域。因此，LBD一直是密集的结构研究和药物发现的焦点。大多数人核激素受体LBD的晶体结构已被确定，这些结构为核受体的配体调节和配体发现提供了关键机制。本申请第一次更新的工作确定了两种抑制性孤儿NR SHP和TLX的新调控机制，并表明其他抑制性孤儿NR可能具有类似的机制。在本申请的具体目的中，我们将通过功能分析新发现的调节界面并通过确定不同状态下SHP的晶体结构来鉴定SHP受小分子调节以及SHP抑制其他NR的结构机制来测试该假设。在结构确定之后，我们将通过与这些受体的关键专家Steve Kliewer、大卫Mangelsdorf、Chun-Li Zhang和Pat Griffin博士的密切合作来验证关键结构元件的功能意义。重要性：本申请中产生的结构信息将显著增强我们对这些孤儿核受体如何进化为各自的配体依赖性或非依赖性信号传导途径的分子机制的理解，并且可以作为靶向这些受体的药物发现的合理模板。

DESCRIPTION (provided by applicant): Nuclear receptors (NRs) comprise a family of 48 transcription factors, which are regulatory proteins that turn genes on or off. In contrast to othe transcription factors, the activity of NRs is physiologically regulated by small molecules (ligands), including sex hormones, glucocorticoids, vitamins, lipids, and others, which makes these proteins amenable to pharmacological intervention for the treatment of many diseases, including inflammation, cancer, and diabetes. NRs therefore represent one of the most successful classes of therapeutic drug discovery targets. Orphan NRs are receptors for which no physiological ligands were known when they were first identified. This set of NRs remains of enormous medical interest as their physiological roles and possible regulation by small molecules and drugs are still emerging. The objective of this study is to determine high resolution crystal structures of the remaining orphan NR ligand-binding domains (LBDs), to correlate the structures with biological functions of these receptors, and to explore the structura information for drug discovery that targets these receptors. All nuclear receptors contain at least one of two conserved domains: the centrally-located DNA-binding domain (DBD) and the C-terminal LBD. The LBD is the key functional domain that mediates the ligand binding, receptor dimerization, ligand-regulated transcriptional function of nuclear receptors. As such the LBD has been the focus of intense structural studies and pharmaceutical discovery. Crystal structures of most of the human nuclear hormone receptor LBDs have been determined and these structures have provided key mechanisms of ligand regulation and ligand discovery for nuclear receptors. Work from the first renewal of this application identified novel regulatory mechanisms for two repressive orphan NR, SHP and TLX, and suggested that similar mechanisms may be shared by other repressive orphan NRs. In the specific aims of this application, we will test this hypothesis by functionally analyzing the newly discovered regulatory interfaces and by determining the crystal structure of SHP in different states to identify the structural mechanisms by which SHP is regulated by small molecules and by which SHP represses other NRs. Following the structural determination, we will validate the functional significance of key structural elements through close collaborations with Drs Steve Kliewer, David Mangelsdorf, Chun-Li Zhang, and Pat Griffin, who are key experts on these receptors. Significance: The structural information generated in this application will significantly enhance our understanding of the molecular mechanisms of how these orphan nuclear receptors have evolved for their respective ligand-dependent or -independent signaling pathways, and can serve as rational templates for drug discovery that targets these receptors.