Structural Genomics of Orphan Nuclear Receptors

描述(申请人提供)：核受体(NRs)由48个转录因子家族组成，这些转录因子是调节基因开启或关闭的蛋白质。与其他转录因子不同，NRs的活性受到小分子(配体)的生理调节，包括性激素、糖皮质激素、维生素、脂质和其他，这使得这些蛋白质适合于药物干预，用于许多疾病的治疗，包括炎症、癌症和糖尿病。因此，NRS代表了最成功的治疗药物发现靶点之一。孤儿NRs是一种受体，其生理配体在首次被发现时并不为人所知。这套NRs仍然具有巨大的医学价值，因为它们的生理作用以及小分子和药物可能的调节仍在不断出现。本研究的目的是确定剩余的孤儿NR配体结合域(LBD)的高分辨晶体结构，将这些受体的结构与生物学功能联系起来，并探索针对这些受体的药物开发的结构信息。所有的核受体至少含有 两个保守结构域之一：位于中心的DNA结合域(DBD)和C末端的LBD。LBD是介导核受体配体结合、受体二聚化、配体调控转录功能的关键功能区。因此，LBD一直是紧张的结构研究和药物发现的焦点。大多数人类核激素受体LBD的晶体结构已经确定，这些结构为核受体的配基调节和配基发现提供了关键机制。从这项申请的第一次更新中发现了两个压抑性孤儿NR，SHP和TLX的新的调节机制，并表明类似的机制可能被其他压抑性孤儿NR共享。在这一应用的特定目标中，我们将通过对新发现的调控界面进行功能分析并通过测定SHP在不同状态下的晶体结构来验证这一假说，以确定SHP受小分子调控以及SHP抑制其他NRs的结构机制。在结构确定之后，我们将通过与这些受体的关键专家Steve Kliewer、David Mangelsdorf、Chun-Li Zhang和Pat Griffin的密切合作来验证这些关键结构元件的功能意义。意义：在这一应用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为各自的配体依赖或独立的信号通路进化的分子机制的理解，并可以作为针对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.