Regulation of PTH secretion by TRPC1

原发性甲状旁腺功能亢进是最常见的内分泌疾病之一。初级 甲状旁腺功能亢进由甲状旁腺腺瘤引起，而继发性甲状旁腺功能亢进由 肾脏疾病背景下的甲状旁腺增生。这两种情况都与减少 抑制甲状旁腺激素（PTH）所需的Ca 2+敏感受体（CaSR）的表达 高钙血症时的分泌。了解调节PTH的分子机制 CaSR下游的分泌对于发现治疗甲状旁腺功能亢进的新疗法至关重要 及其相关的发病率。在这里，我们第一次表明，Tprc 1基因敲除小鼠发生原发性 甲状旁腺功能亢进、高钙血症和低尿钙排泄类似人类疾病家族性 低尿钙高钙血症（FHH）。FHH是原发性甲状旁腺功能亢进的一种形式， 编码CaSR的CASR、GNA 11和AP 2S 1中的突变，CaSR是鸟嘌呤核苷酸结合的α11亚基， 蛋白，以及AP 2网格蛋白相关衔接子复合物的σ1亚基介导细胞表面的再循环 受体和通道。因此，我们测试了TRCP 1功能是否与CaSR直接相关。 发信号。体外生物化学、功能和细胞生物学实验表明，TRPC 1被激活， CaSR涉及Gα11的作用。我们还表明TRPC 1与AP 2 σ1物理相互作用。这些数据 导致我们假设TRPC 1是甲状旁腺中PTH分泌正常抑制所必需的 通过Gα11作用于CaSR下游的腺体。TRPC 1与AP 2 σ1的相互作用增加了 通过加速失活TRPC 1的再循环，TRPC 1可用于CaSR诱导的信号传导。目标1： 将采用细胞生物学方法来确定TRPC 1介导CaSR诱导的Ca 2+的机制 信号传导以及Gα11和AP 2 σ1在甲状旁腺细胞中的信号传导途径中的作用。 在具体目标2中，我们将通过以下方法确定TRPC 1在体内是否在CaSR和Gα11下游发挥功能： 询问在其甲状旁腺中缺乏Trpc 1和Casr或Gnα11/Gnαq基因的复合小鼠是否 显示出比单基因缺失引起的表型更严重的FHH样表型。了解 调节PTH分泌的途径可能对设计新的和更有效的， 治疗原发性和继发性甲状旁腺功能亢进患者的具体方法。

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.