Interaction of PTH with the PTH-1 Receptor

这些研究将探讨PTH和PTHrP配体结合的分子机制， 激活PTH/PTHrP受体（PTHR 1）：PTHR 1在钙和磷酸盐中起重要作用 体内平衡，以及骨生长和重塑。我们有新的数据表明PTHR 1可以采用 不同的PTH和PTHrP配体以不同的构象结合这些构象， 选择性，从而诱导不同的生物反应。Thsu、PTH（1-34）和某些其他配体，但 而不是PTHrP（1-36），以高亲和力结合一种新的构象，称为RO，它对 GTP γ S，因此不可能与G蛋白偶联。优先与RO结合的配体产生 延长细胞和动物的信号反应。因此，我们假设RO是一个稳定的中介 可以转换为活动状态RG。这表明RO选择性配体将产生延长的信号传导。 相反，RG-选择性配体将产生短暂的、脉动的信号传导反应。这些假设 不仅对理解PTHR 1的基本机制有重要意义， 分别介导内分泌和旁分泌的PTH和PTHrP的生物学作用，但也用于 开发新的基于PTHR 1的治疗方法，用于骨质疏松症和甲状旁腺功能减退症等疾病， 该信号持续时间显得很关键。我们的目标是阐明潜在的生化和细胞 参与的机制，并确认假说，构象选择性在PTHR 1是 生物学上相关，并且实际上控制PTH和PTHrP配体在体内的作用。为此，我们将 使用结合分子和药理学方法的综合实验设计方法， 基于FRET的生物物理方法、高分辨率亚细胞成像方法和体内小鼠模型 系统.为了证实我们的假设，我们将开发和测试新的PTHR 1配体， 增强构象选择性，从而改变生物学和信号传导作用。特别是要 开发新的长效RO选择性配体，并评估它们在以下方面是否上级PTH（1-34） 使甲状旁腺功能减退模型中的钙正常化。我们还将开发短效的， 配体，并评估它们是否对骨具有有效的合成代谢作用， 方面的影响.这些药物可能代表用于治疗骨质疏松症的“下一代”PTHR 1配体。

These studies will investigate the molecular mechanisms by which PTH and PTHrP ligands bind to and activate the PTH/PTHrP receptor (PTHR1): The PTHR1 plays vital roles in calcium and phosphate homeostasis, and in bone growth and remodeling. We have new data to suggest that the PTHR1 can adopt different conformations, and that different PTH and PTHrP ligands bind to these conformations with different selectivities, and thus induce different biological responses. Thsu, PTH(1-34) and certain other ligands, but not PTHrP(1-36), bind with high affinity to a novel conformation, called RO, which is insensitive to GTPgammaS, and thus, are not likely coupled to G proteins. Ligands that bind preferentially to RO produce prolonged signaling responses in cells and in animals. We thus hypothesize that RO is a stable intermediary that can convert to active-state, RG. This pedicts that RO-selective ligands will produce prolonged signaling. In contrast, RG-selective ligands will produce short-lived, pulsatile, signaling responses. These hypotheses have important implications, not only for understanding the fundamental mechanisms by which the PTHR1 mediates the biological actions of PTH and PTHrP, endocrine and paracrine, respectively, but also for developing new PTHR1-based therapies for diseases such as osteoporosis and hypoparathyroidism, for which signal duration time appears critical. Our goal is to elucidate the underlying biochemical and cellular mechanisms involved, and to confirm the hypothesis that conformational selectivity at the PTHR1 is biologically relevant, and indeed governs the actions of PTH and PTHrP ligands in vivo. To do this, we will use an integrated experimental design approach that incorporates molecular and pharmacological methods, FRET-based biophysical methods, high-resolution sub-cellular imaging methods, and in vivo mouse model systems. As confirmation of our hypotheses, we will develop and test new PTHR1 ligands that have enhanced conformational selectivity, and thus altered biological and signaling actions. In particular, we will develop new long-acting RO-selective ligands, and assess whether they are superior to PTH(1-34) in normalizing calcium in models of hypoparathyroidism. We also will develop short-acting, RG-selective ligands, and assess whether they have potent anabolic effects on bone with minimal resorptive/calcemic effects. Such agents could represent the "next generation" of PTHR1 ligands for treating osteoporosis.