G Protein Receptor--Structural Characterization

描述(申请人提供)：我们的目标是探索甲状旁腺激素(PTH)的G蛋白偶联受体(PTH1和PTH2)的结构特征。甲状旁腺素是为数不多的几种被证实在人类体内具有合成代谢作用的骨活性物质之一，因此已被广泛研究为治疗骨质疏松症的可能靶点。我们的目标是在结构的基础上表征受体与已知与其偶联的G蛋白(Gs和Gq)的关联。此外，我们还将从结构上研究PTH1与受体内化的重要一步-抑制蛋白2的关系。第二个目标是利用本课题组先前确定的PTH和PTH1的结构特征，合理设计基于低分子量PTH的类似物。众所周知，甲状旁腺激素的N端负责受体的激活。然而，仅PTH(1-14)这个结构域具有极低的结合亲和力。通过随机筛选，已经开发出具有低um势的类似物(例如，(Ala3，10，12，Arg11)Pth(1-14))。我们对这种先导化合物的结构表征提供了许多方法来结合额外的构象约束(环化)以及非天然氨基酸和肽仿制。本研究将有助于合理设计和优化以甲状旁腺素为基础的钙稳态调节剂。最终目的是利用PTH1受体的药效团的建立，以及TIP39(tuberoin漏斗状多肽-39)的结构特征来建立PTH2受体的结构-活性关系。这些信息将有助于设计稳定的PTH2特异性拮抗剂，这将有助于建立受体的生理作用，被认为参与脑垂体和胰腺激素的释放，并可能感受疼痛。鉴于PTH激活两种受体，而TIP39(7-39)是PTH1的特异性受体，后两个目的之间存在很大的协同作用；旨在开发有价值的PTH2生理特性的工具的结果将加速合理设计PTH1受体特异性的、治疗骨质疏松的先导候选药物。

DESCRIPTION (provided by applicant): We aim to probe the structural features of the G-protein coupled receptors (PTH1 and PTH2) for parathyroid hormone (PTH). PTH is one of the few bone-active agents proven to be anabolic in humans and therefore has been intensively examined as a possible target for the treatment of osteoporosis. We aim to characterize, on a structural basis, the association of the receptor to the G-proteins (Gs and Gq) known to couple to it. Additionally, the association of PTH1 to beta-arrestin2, an important step in the internalization of the receptor will also be structurally examined. A second aim is to utilize the structural features of PTH and PTH1 previously determined in our group to rationally design low molecular weight PTH-based analogs. It is well established that the N-terminus of PTH is responsible for receptor activation. However, this domain alone, PTH(1-14), has extremely low binding affinity. Through random screening, analogs with low uM potencies (e.g., (Ala3, 10,12, Arg11)PTH(1-14)) have been developed. Our structural characterization of this lead compound has provided a number of methods to incorporate additional conformational constraint (cyclization) as well as non-natural amino acids and peptidomimetics. The research described here will facilitate the rational design and optimization of PTH-based agents for the regulation of calcium homeostasis. A final aim is to utilize the establishment of the pharmacophore for the PTH1 receptor, as well as structural characterization of TIP39 (tuberoinfundibular peptide-39) to develop a structure-activity relationship for the PTH2 receptor. Such information would facilitate the design of stable, PTH2 specific antagonist, which would assist in the establishing the physiological role of the receptor, thought to be involved in release of pituitary and pancreatic hormones and possibly perception of pain. Given that PTH activates both receptors, and TIP39(7-39) is specific for PTH1, there is a great synergy between the latter two aims; the results aimed to develop a valuable tool for the physiological characterization of PTH2 will accelerate the rational design of PTH1 receptor-specific, lead drug candidates for the treatment of osteoporosis.