The Interaction of Thyroid Hormone and Wnt Signaling Pathways in the Growth Plate

描述（由申请人提供）：随着我们对信号转导知识的增加，很明显，进一步的科学进步将需要了解单个信号通路如何整合到更广泛的信号网络中，从而调节基本的细胞过程，如增殖和分化。五十多年前，甲状腺激素首次被确定为生长板骨骼成熟的有效调节剂。从那时起，许多体外和体内研究证实，甲状腺激素调节生长板中细胞增殖到终末分化的关键转变，特别是生长板软骨细胞向肥大细胞的成熟。然而，这些研究既没有确定甲状腺激素调节骨骼成熟的分子机制，也没有证明甲状腺激素的系统作用如何与生长板的局部调节环境相结合。典型的Wnt信号通路最近被确定为软骨细胞成熟的另一个重要调节因子。我们实验室最近的研究表明，典型的Wnt信号被生长板软骨细胞的甲状腺激素治疗激活，并且羧基肽酶Z (CPZ)，一种从蛋白质中去除羧基末端精氨酸残基的Wnt调节剂，在甲状腺激素治疗24小时内上调10倍。先前的研究者也观察到甲状腺激素对生长板中生长激素和IGF-1受体表达的积极作用，以及IGF-1信号传导对细胞浆中β -连环蛋白积累和生长板软骨细胞肥大的积极作用。以下具体目标将验证甲状腺激素通过调节生长板软骨细胞中的Wnt信号通路调节骨骼成熟的新假设，并将确定甲状腺激素的作用在多大程度上是由CPZ和/或生长激素/IGF-1轴介导的：1)测定甲状腺激素治疗生长板软骨细胞对体外和体内典型Wnt信号通路关键元件表达和活性的影响；2)明确甲状腺激素对典型Wnt信号的影响程度是由CPZ介导的；3)明确GH/IGF-1介导甲状腺激素对典型Wnt信号传导的影响程度。

DESCRIPTION (provided by applicant): As our knowledge of signal transduction has increased, it has become apparent that further scientific advances will require understanding of how individual signaling pathways become integrated into a broader signaling network that regulates fundamental cellular processes such as proliferation and differentiation. Thyroid hormone was first identified as a potent regulator of skeletal maturation at the growth plate more than fifty years ago. Since that time, many in vitro and in vivo studies have confirmed that thyroid hormone regulates the critical transition between cell proliferation and terminal differentiation in the growth plate, specifically the maturation of growth plate chondrocytes into hypertrophic cells. However these studies have neither identified the molecular mechanisms involved in the regulation of skeletal maturation by thyroid hormone, nor demonstrated how the systemic actions of thyroid hormone interface with the local regulatory milieu of the growth plate. The canonical Wnt signaling pathway has recently been identified as another important regulator of chondrocyte maturation. Recent studies in our laboratory indicate that canonical Wnt signaling is activated by thyroid hormone treatment of growth plate chondrocytes, and that carboxypeptidase Z (CPZ), a Wnt modulator that removes carboxy-terminal arginine residues from proteins, is upregulated ten-fold within 24 hours of thyroid hormone treatment. Previous investigators have also observed a positive effect of thyroid hormone on expression of the growth hormone and IGF-1 receptors in the growth plate, as well as positive effects of IGF-1 signaling on both cytoplasmic accumulation of beta-catenin and hypertrophy of growth plate chondrocytes. The following specific aims will test the novel hypothesis that thyroid hormone regulates skeletal maturation through modulation of Wnt signaling pathways in growth plate chondrocytes, and will define the degree to which this thyroid hormone effect is mediated by CPZ and/or the growth hormone / IGF- 1 (GH/IGF-1) axis: 1) To determine the effect of thyroid hormone treatment of growth plate chondrocytes on the expression and activity of key elements of the canonical Wnt signaling pathway in vitro and in vivo; 2) To define the degree to which the thyroid hormone effect on canonical Wnt signaling is mediated by CPZ; 3) To define the degree to which the thyroid hormone effect on canonical Wnt signaling is mediated by GH/IGF-1.