Regulation of PTH secretion by TRPC1

原发性甲状旁腺功能亢进症是最常见的内分泌疾病之一。主要 甲状旁腺机能亢进症是由甲状旁腺腺瘤引起的，而继发性甲状旁腺机能亢进症是由 以甲状旁腺增生为背景的肾脏疾病。这两种情况都与 抑制甲状旁腺激素(PTH)所需的钙敏感受体(CaSR)的表达 高钙血症环境下的分泌物。了解调节甲状旁腺素的分子机制 CaSR下游的分泌对发现治疗甲状旁腺功能亢进症的新疗法至关重要 以及与之相关的发病率。在这里，我们第一次展示了Tprc1基因缺失的小鼠发展为原发 甲状旁腺功能亢进症、高钙血症和低尿钙排泄率与人类疾病家族性相似 低钙尿性高钙血症(FHH)。甲状旁腺功能亢进是一种原发性甲状旁腺机能亢进症，由失活引起。 编码鸟嘌呤核苷酸结合的α11亚基CaSR、GNA11和AP2S1的突变 蛋白质，以及介导细胞表面循环的AP2clathrin相关接头复合体的σ1亚单位 分别是受体和通道。因此，我们测试了TRCP1功能是否直接链接到CASR 发信号。体外生化、功能和细胞生物学实验表明，TRPC1被激活 涉及Gα11的作用。我们还发现σ1与AP2在物理上相互作用。这些数据 我们由此推测，TRPC1是正常抑制甲状旁腺分泌甲状旁腺素所必需的。 通过Gα11作用于CaSR下游的腺体。TRPC1与AP2σ1的相互作用增加 通过加速失活的TRPC1的循环，TRPC1可用于CaSR诱导的信号转导。在目标1中，我们 将使用细胞生物学方法来确定TRPC1介导CaSR诱导的钙离子的机制 甲状旁腺来源细胞的信号转导及Gα11和AP2σ1在此信号通路中的作用 在特定的目标2中，我们将通过以下方式确定TRPC1在体内是否在CaSR和Gα11下游发挥作用 询问复合小鼠甲状旁腺是否缺少Trpc1和Casr或Gnα11/GnαQ基因 表现出比单基因缺失引起的表型更严重的FHH样表型。了解 调节甲状旁腺素分泌的途径可能对设计新的、更有效的和 治疗原发性和继发性甲状旁腺功能亢进症患者的具体方法。

Primary hyperparathyroidism is the one of the most common endocrine disorders. Primary hyperparathyroidism results from parathyroid adenomas while secondary hyperparathyroidism results from parathyroid gland hyperplasia in the setting of renal disease. Both conditions are associated with decreased expression of the Ca2+ sensing receptor (CaSR) which is required to suppress parathyroid hormone (PTH) secretion in the setting of hypercalcemia. Understanding the molecular mechanisms that regulate PTH secretion downstream of CaSR is critical for the discovery of new therapeutics to treat hyperparathyroidism and its associated morbidity. Here we show for the first time that Tprc1-null mice develop primary hyperparathyroidism, hypercalcemia, and low urinary calcium excretion mimicking the human disease Familial Hypocalciuric Hypercalcemia (FHH). FHH is a form of primary hypeparathyroidism and caused by inactivating mutations in CASR, GNA11 and AP2S1 encoding CaSR, the α11 subunit of the guanine nucleotide-binding protein, and the σ1 subunit of the AP2 clathrin-associated adaptor complex mediating recycling of cell surface receptors and channels, respectively. Thus, we tested whether TRCP1 function is directly linked to CaSR signaling. Biochemical, functional, and cell biological experiments in vitro show that TRPC1 is activated by CaSR involving the action of Gα11. We also show that TRPC1 physically interacts with AP2σ1. These data lead us to the hypothesis that TRPC1 is required for normal suppression of PTH secretion in the parathyroid gland by acting downstream of CaSR via Gα11. The interaction of TRPC1 with AP2σ1 increases the availability of TRPC1 for CaSR-induced signaling by accelerating recycling of inactivated TRPC1. In Aim 1, we will employ cell biological approaches to define the mechanism by which TRPC1 mediates CaSR-induced Ca2+ signaling and the role of Gα11 and AP2σ1 in this signaling pathway in cells derived from the parathyroid gland. In specific Aim 2, we will determine whether TRPC1 functions downstream of CaSR and Gα11 in vivo, by asking whether compound mice lacking Trpc1 and Casr or Gnα11/Gnαq genes in their parathyroid glands show more severe FHH-like phenotypes than phenotypes elicited by single gene deletions. Understanding the pathways that regulate PTH secretion could have a high impact on designing new and more effective and specific approaches to treat patients with primary as well as secondary hyperparathyroidism.