Mechanisms of PTH Signal Transduction in Bone Cells

说明（改编自申请人摘要）：甲状旁腺激素（PTH） 在调节钙代谢中起着重要作用， 一种骨骼合成激素这种激素似乎是通过一个单一的 成骨细胞上的受体，以引发其所有的骨骼效应，包括其 合成代谢作用。我们已经表明，低浓度的PTH（10 12和10”） M）刺激培养的成骨细胞的DNA合成和增殖， 这是由于蛋白激酶C（PKC）的选择性激活， 导致细胞外信号调节激酶（ERK）的激活。的 最可能的原因是因为这些浓度的PTH与它们的 受体以这样的方式选择性地激活某些Ga蛋白（如 Gaq或Ga 2/13）导致PKC的激活。这种激活和作用 在成骨细胞中没有很好的记录。因此，总体目标 目前竞争性更新的目的是描述低浓度的PTH 通过PKC的信号和ERK激活的最终目标是什么， 导致成骨细胞增殖。这将作为一个双管齐下的 方法：1.确定低浓度的PTH如何通过PKC信号传导， 成骨细胞通过：a）确定低活化的PKC同工酶的类型， 所述激素的浓度，B）评估所述信号转导途径 c）确定激活PKC同工酶的G蛋白， 特别是磷脂酶。2.描绘ERK的最终靶点 活化，其通过以下方式导致成骨细胞增殖：a）检查 已知的ERK靶基因是否受到成骨细胞治疗的影响 B）鉴定由低浓度PTH调节的其它基因， c）检查所述基因的mRNA的变化是否 反映在蛋白质水平的变化中，d）切除调节的基因， 通过使用蛋白质的显性负性形式或诱导性反义 RNA，并确定这是否会阻止成骨细胞的增殖， 低剂量的PTH。这项工作的结果将提供深入了解 成骨细胞调节的关键途径之一。在此过程中，数据 可能为开发可用于治疗癌症的小分子提供基础。 用于治疗骨质疏松症的PTH注射部位。

DESCRIPTION (Adapted from the Applicant's Abstract): Parathyroid hormone (PTH) plays a central role in regulation of calcium metabolism but also has a role as an anabolic hormone for bone. The hormone appears to act through a single receptor on the osteoblast to elicit all of its skeletal effects, including its anabolic effects. We have shown that low concentrations of PTH (1012 and I 0" M) stimulate DNA synthesis and proliferation of osteoblastic cells in culture, and that this is due to selective activation of protein kinase C (PKC) resulting in activation of extra-cellular signal regulated kinases (ERKs). The most likely reason is because these concentrations of PTH interact with their receptor in such a way as to selectively activate certain Ga proteins (such as Gaq or Ga 2/13) leading to activation of PKC. The activation and role of this pathway has not been well documented in the osteoblast. Thus, the overall goal of the present competing renewal is to delineate how low concentrations of PTH signal through PKC and what the eventual targets of ERK activation are which lead to proliferation of osteoblastic cells. This will be done as a two-pronged approach: 1. determining how low concentrations of PTH signal though PKC in osteoblastic cells by: a) ascertaining the type of PKC isozyme activated by low concentrations of the hormone, b) assessing the signal transduction pathway activating the PKC isozyme(s), c) determining the G protein activating the particular phospholipase(s). 2. delineating the eventual targets of ERK activation which lead to proliferation of osteoblastic cells by: a) examining whether known ERK target genes are affected by treatment of osteoblastic cells with low concentrations of PTH, b) identifying other genes regulated by low concentrations of PTH, c) examining whether the changes in mRNA for the gene(s) are reflected in changes in protein levels, d) ablating the regulated gene(s) by either using dominant negative forms of the protein or inducible anti-sense RNA, and ascertaining if this prevents enhanced proliferation of osteoblastic cells by low doses of PTH. The results of this work will provide insight into one of the key pathways of regulation of the osteoblast. In so doing, the data may provide a foundation for development of small molecules that can be used in place of injected PTH for treatment of osteoporosis.