PTH Reduces the Mechanical Threshold in Osteoblasts

PTH 降低成骨细胞的机械阈值

• 批准号: 6928691
• 负责人: RANDALL L DUNCAN
• 金额: $ 15.73万
• 依托单位: INDIANA UNIV-PURDUE UNIV AT INDIANAPOLIS
• 依托单位国家: 美国
• 财政年份: 2000
• 资助国家: 美国
• 起止时间: 2000-08-15 至 2005-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6928691
• 关键词: 3T3 cells; biological signal transduction; bone development; calcium channel; calcium indicator; calcium ion; enzyme linked immunosorbent assay; gene expression; hormone regulation /control mechanism; immunofluorescence technique; mechanical pressure; northern blottings; osteoblasts; parathyroid hormones; protein kinase A; statistics /biometry; voltage /patch clamp; western blottings

DESCRIPTION (provided by applicant): Parathyroid hormone (PTH) enhances the osteogenic response of bone to mechanical loads, in vivo. We postulate that PTH interacts with the signaling mechanisms of mechanotransduction to lower the mechanical threshold and prime the osteogenic cells of bone to respond to lesser magnitudes of mechanical stimulation to promote bone formation. We have shown that PTH can alter both mechanosensitive (MSCC) and L-type voltage sensitive calcium channel (LVSCC) kinetics to increase the Ca2+ signal in osteoblasts, resulting in increased osteogenic activity. Further, we have shown that reorganization of the actin cytoskeleton leads to increased activity of MSCC and that PTH-induced activation of protein kinase A (PKA) enhances activity of both the L-VSCC and the MSCC. We have also shown that inhibition of the L-VSCC significantly reduces the bone formation rate in both rats and mice subjected to mechanical loading and completely blocks the PTH enhanced bone formation response to in vivo loading. Our overall hypothesis is that PTH reduces the mechanical threshold in osteoblasts by altering MSCC and L-VSCC kinetics to increase the entry of Ca2+ in response to a mechanical signal. In this proposal, we will continue to examine the mechanisms of PTH control of the mechanotransduction signaling pathways and how this regulation alters cell function. The aims of this proposal are: 1) examine the role of the cytoskeleton in the regulation of MSCC and L-VSCC kinetics and intracellular Ca2+ release in osteoblasts in response to shear and ascertain how PTH modulates this regulation, 2) determine the effects of phosphorylation on the regulation of the MSCC and L-VSCC kinetics fluid shear and PTH stimulation in osteoblasts and 3) ascertain how PTH enhanced Ca2+'entry through the MSCC and L-VSCC alters release of autocrine/paracrine factors and increase gene expression in osteoblasts. Completion of these aims should provide insight into the regulation of bone by the mechanical environment and how modulation of the signaling pathways can affect bone formation.

描述（由申请人提供）：甲状旁腺激素（PTH）在体内增强骨骼对机械负荷的成骨反应。我们假设 PTH 与机械转导的信号机制相互作用，以降低机械阈值，并使骨的成骨细胞对较小强度的机械刺激做出反应，从而促进骨形成。我们已经证明，PTH 可以改变机械敏感 (MSCC) 和 L 型电压敏感钙通道 (LVSCC) 动力学，以增加成骨细胞中的 Ca2+ 信号，从而增加成骨活性。此外，我们还发现肌动蛋白细胞骨架的重组导致MSCC活性增加，并且PTH诱导的蛋白激酶A（PKA）激活增强了L-VSCC和MSCC的活性。我们还表明，抑制 L-VSCC 可显着降低承受机械负荷的大鼠和小鼠的骨形成率，并完全阻断 PTH 对体内负荷增强的骨形成反应。我们的总体假设是，PTH 通过改变 MSCC 和 L-VSCC 动力学来增加 Ca2+ 响应机械信号的进入，从而降低成骨细胞的机械阈值。在本提案中，我们将继续研究 PTH 控制力转导信号通路的机制以及这种调节如何改变细胞功能。该提案的目的是：1) 检查细胞骨架在调节 MSCC 和 L-VSCC 动力学以及成骨细胞响应剪切的细胞内 Ca2+ 释放中的作用，并确定 PTH 如何调节这种调节，2) 确定磷酸化的影响关于成骨细胞中 MSCC 和 L-VSCC 动力学流体剪切和 PTH 刺激的调节，以及 3）确定 PTH 如何增强 Ca2+' 通过 MSCC 的进入和L-VSCC 改变自分泌/旁分泌因子的释放并增加成骨细胞中的基因表达。完成这些目标应该可以深入了解机械环境对骨的调节以及信号通路的调节如何影响骨形成。