PTH Inverse Agonists as Therapy for Jansen’s Disease

项目总结/摘要 Jansen干骺端软骨发育不良（JMC）是一种罕见的发育性疾病，由激活，获得， PTH 1 R、甲状旁腺激素（PTH）受体和PTH相关肽的功能缺失突变 （PTHrP）。PTH 1 R突变导致骨骼发育异常，导致严重的骨骼瘫痪 畸形和极度矮小此外，JMC患者发展为慢性，通常是严重的 高钙血症和高钙尿症，这些疾病会在以后的生活中导致慢性肾病（CKD）， 需要对老年人进行肾脏替代治疗。目前没有治愈或有效的治疗方法， JMC，尽管有明确的分子靶点。我们以前开发了几种PTH-PTHrP类似物， 当在表达不同组成型活性PTH 1 R的细胞中测试时显示反向激动作用，包括 H223 R-PTH 1 R突变体。我们广泛的初步研究表明，一种反向激动剂，即 L11，dW 12，W23，Y36-PTHrP（7-36）（dTrp 12-PTHrP（7-36））逆转H223 R-PTH 1 R诱导的体内效应 通过I型胶原启动子表达的突变体（Col 1-H223 R小鼠），从而降低骨转换， 皮质骨丢失和改善骨长度。我们现在计划提供进一步的文件， 类似物或其衍生物，可以防止生长板异常，其发生在表达 通过II型胶原启动子增殖软骨细胞中的H223 R-PTH 1 R突变体（Col 2-H223 R小鼠）; 纯合子Col 2-H223 R小鼠很小，就像JMC患者一样，并且产前和/或产后 用反向激动剂治疗将改善骨生长。我们还建议开发转基因小鼠 在近端小管和远端小管中表达突变PTH 1 R的小鼠，以及如果需要的话，“敲入”JMC小鼠，即 模拟所有疾病方面的鼠模型。除了矫正儿童生长板异常外 受JMC的影响，可以想象，反向激动剂将防止高钙血症和高钙尿症， 儿童和成人患者激活PTH 1 R突变，因此肾钙质沉着症和CKD。见解 减少突变PTH 1 R信号传导的机制可能导致有效的靶向方法， 通过额外的肽类似物或小分子在患有PTH-或PTHrP-的患者中治疗野生型PTH 1 R， 依赖性高钙血症，或继发性高甲状旁腺激素由于CKD。此外，我们的研究将 为生长板、骨骼和肾脏生理学提供了新的见解，他们将鼓励对 其他致病G蛋白偶联受体突变体的反向激动剂。

PROJECT SUMMARY/ABSTRACT Jansen's Metaphyseal Chondrodysplasia (JMC) is a rare developmental disease caused by activating, gain- of-function mutations in the PTH1R, the receptor for parathyroid hormone (PTH) and PTH-related peptide (PTHrP). The PTH1R mutations lead to abnormal skeletal development resulting in severe, crippling bone deformities, and extremely short stature. In addition, JMC patients develop chronic, often severe hypercalcemia and hypercalciuria that contribute to development of chronic kidney disease (CKD) later in life, necessitating kidney replacement therapy in older adults. There is currently no cure or effective treatment for JMC, despite a clearly defined molecular target. We previously developed several PTH-PTHrP analogs that show inverse agonism when tested in cells expressing different constitutively active PTH1Rs, including the H223R-PTH1R mutant. Our extensive preliminary studies have shown that one inverse agonist, namely L11,dW12,W23,Y36-PTHrP(7-36) (dTrp12-PTHrP(7-36)), reverses in vivo effects induced by the H223R-PTH1R mutant expressed via the type I collagen promoter (Col1-H223R mice), thus reducing bone turnover and cortical bone loss, and improving bone length. We now plan to provide further documentation that this PTH analog, or a derivative thereof, can prevent the growth plate abnormalities, which occur in mice expressing the H223R-PTH1R mutant in proliferating chondrocytes via the type II collagen promoter (Col2-H223R mice); homozygous Col2-H223R mice are small, just like JMC patients, and it is plausible that pre- and/or post-natal treatment with an inverse agonist will improve bone growth. We also propose developing transgenic mice expressing the mutant PTH1R in proximal and distal tubules, and if necessary a “knock-in” JMC mouse, i.e. a murine model mimicking all disease aspects. Besides correction of growth plate abnormalities in children affected by JMC, it is conceivable that inverse agonists will prevent hypercalcemia and hypercalciuria in pediatric and adult patients with activating PTH1R mutations, and thus nephrocalcinosis and CKD. Insights into the mechanisms that reduce signaling at the mutant PTH1R may lead to effective approaches targeting the wild-type PTH1R through additional peptide analogs or small molecules in patients with PTH- or PTHrP- dependent hypercalcemia, or with secondary hyperparathyroidism due to CKD. In addition, our studies will provide novel insights into growth plate, bone, and kidney physiology, and they will encourage searches for inverse agonists at other disease-causing G protein-coupled receptor mutants.