Interaction of PTH with the PTH-1 Receptor

这些研究将探讨甲状旁腺素和甲状旁腺素配基结合的分子机制。 激活PTH/PTHrP受体(PTHR1)：PTHR1在钙和磷中起重要作用 动态平衡，以及骨骼生长和重塑。我们有新的数据表明PTHR1可以采用 不同的构象，不同的PTH和PTHrP配体以不同的方式结合到这些构象上 选择性，从而引起不同的生物反应。Thsu、PTH(1-34)和某些其他配体，但 不是PTHrP(1-36)，与一种新的构象高亲和力结合，称为RO，它对 因此，GTPGammaS不太可能与G蛋白偶联。优先与RO结合的配体产生 延长了细胞和动物体内的信号反应。因此，我们假设RO是一个稳定的中间体 可以转换为活动状态的RG。这表明RO选择性配体将产生延长的信号。 相反，RG选择性配体将产生短暂的、脉动的信号反应。这些假设 具有重要的意义，不仅对于理解PTHR1 分别介导PTH和PTHrP的生物学作用，内分泌和旁分泌，也可用于 开发基于PTHR1的新疗法，用于治疗骨质疏松症和甲状旁腺功能减退症等疾病 哪个信号持续时间看起来很关键。我们的目标是阐明潜在的生化和细胞 机制，并确认PTHR1的构象选择性是 在生物学上相关，并确实控制甲状旁腺素和甲状旁腺素配体在体内的作用。要做到这一点，我们将 使用结合了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活体小鼠模型 系统。为了证实我们的假设，我们将开发和测试新的PTHR1配体 增强构象选择性，从而改变生物和信号作用。特别是，我们将 开发新的长效RO选择性配体，并评估它们在以下方面是否优于PTH(1-34 甲状旁腺功能减退症模型的钙正常化。我们还将开发短效、RG选择性 配体，并评估它们是否对骨骼具有强大的合成代谢作用，同时最大限度地减少吸收/增钙 效果。这类药物可能代表用于治疗骨质疏松症的PTHR1配体的“下一代”。

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.