Connexin 43 Hemichannels and Signaling In Bone

Connexin 43 半通道和骨信号传导

• 批准号: 7658224
• 负责人: Lilian Irene Plotkin
• 金额: $ 33.22万
• 依托单位: INDIANA UNIV-PURDUE UNIV AT INDIANAPOLIS
• 依托单位国家: 美国
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-07-15 至 2013-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7658224
• 关键词: Anabolism; Apoptosis; Apoptotic; Arrestins; Biological Preservation; Bone Mineral Contents; Bone remodeling; Cell Communication; Cell Nucleus; Cell membrane; Cells; Clathrin; Communication; Complex; Connexin 43; Connexins; Cyclic AMP; Defect; Dinoprostone; Disease; Embryo; Environment; Extracellular Signal Regulated Kinases; Failure; Fracture; Functional disorder; G-Protein-Coupled Receptors; Gap Junctions; Gene Expression; Gene Expression Regulation; Glucocorticoids; Hormonal; Hormones; In Vitro; Inhibition of Apoptosis; Knockout Mice; Maintenance; Mechanical Stimulation; Mechanics; Mediating; Membrane Proteins; Mitogen-Activated Protein Kinases; Mus; Nuclear; Osteoblasts; Osteoclasts; Osteocytes; Osteogenesis; Parathyroid Hormones; Pathway interactions; Phosphotransferases; Prevention; Production; Property; Protein Family; Role; Scaffolding Protein; Signal Pathway; Signal Transduction; Skeleton; Stimulus; Testing; Thick; Time; Tissues; Wild Type Mouse; Work; analog; base; bisphosphonate; bone; bone cell; bone strength; extracellular; gap junction channel; human PTH protein; improved; in vivo; novel; prevent; public health relevance; response; scaffold; tool

DESCRIPTION (provided by applicant): Connexins (Cx) are a family of proteins essential for cell-to-cell communication and for the communication of cells with their environment. Cx43 is the most abundant connexin expressed in bone cells. The importance of Cx43 expression in the skeleton has been established by the demonstration of the osteoblast dysfunction and delay ossification in embryos of Cx43 null mice. However, the role of Cx43 and, in particular Cx43 hemichannels expressed in unopposed cell membranes, is far from being completely understood. In studies leading to this application it was demonstrated that bisphosphonates, besides stopping osteoclast-mediated resorption, might preserve bone strength at least in part by promoting osteoblast and osteocyte viability and that Cx43 expression is required for this survival effect. Thus, inhibition of apoptosis by bisphosphonates requires opening of Cx43 hemichannels, activation of the extracellular signal-regulated kinases (ERKs) and extra-nuclear retention of the kinases due to their interaction with the scaffolding protein (-arrestin. Cx43 is also required for prevention of osteoblast apoptosis by parathyroid hormone (PTH) in vitro; and the anabolic response to intermittent administration of the hormone is blunted in mice deficient mice in Cx43. In addition, Cx43 might be also involved in mechanotransduction in the skeleton. Thus, mechanical stimulation increases Cx43 expression, gap junction communication and hemichannel opening in osteoblasts and osteocytes. Based on this evidence, it is hypothesized that Cx43 is a crucial component of signaling pathways activated by pharmacologic, hormonal and mechanical stimuli in osteoblasts and osteocytes, via its involvement in hemichannels or gap junctions or its scaffolding properties. This hypothesis will be tested by a combination of in vitro and in vivo approaches. Studies in Aim 1 will examine the in vivo relevance of the Cx43/(-arrestin/ERK pathway for bisphosphonate actions on bone using bisphosphonate analogs that selectively activate this pathway; and they will delineate the mechanism by which association of Cx43, ERKs and (-arrestin leads to retention of ERKs outside the nucleus and the internalization of Cx43. Studies in Aim 2 will determine the role of Cx43 in the anti-apoptotic effect of PTH in vivo by examining whether the lack of anabolic effect of intermittent PTH administration to mice deficient in Cx43 is due to the inability of PTH to prevent osteoblast apoptosis. Aim 3 will define the role of Cx43 hemichannels in mechanotransduction in vivo and in vitro. This will be accomplished by investigating whether changes in gene expression and the anabolic response to mechanical loading are altered in Cx43 deficient mice; and whether Cx43 is required for the effects of mechanical stimulation in osteoblasts and osteocytes in vitro. We expect that this work will provide opportunities to improve the treatment of diseases with increased bone fragility. PUBLIC HEALTH RELEVANCE: These studies will advance our understanding of the role of Cx43 in the response of the skeleton to pharmacotherapeutic, hormonal and mechanical stimuli. We expect that this work will provide opportunities to improve the treatment of diseases with increased bone fragility.

描述(申请人提供)：连接蛋白(Cx)是一个蛋白质家族，对细胞间的交流和细胞与环境的交流都是必不可少的。Cx43是骨细胞中表达最丰富的连接蛋白。Cx43基因缺失小鼠胚胎中成骨细胞功能障碍和延迟成骨的研究证实了Cx43在骨骼中表达的重要性。然而，Cx43的作用，特别是表达在非对位细胞膜上的Cx43半通道，还远未完全被了解。在导致这一应用的研究中，已经证明双膦酸盐除了阻止破骨细胞介导的吸收外，可能至少部分地通过促进成骨细胞和骨细胞的活性来保持骨强度，并且Cx43的表达是这种生存效应所必需的。因此，双膦酸盐抑制细胞凋亡需要开放Cx43半通道，激活细胞外信号调节蛋白(ERKs)，并由于它们与支架蛋白(-arrestin)的相互作用而将其保留在核外。Cx43也是甲状旁腺激素(PTH)在体外防止成骨细胞凋亡所必需的；在Cx43基因缺陷的小鼠中，间歇给予激素的合成代谢反应被钝化。此外，Cx43还可能参与骨骼的机械转导。因此，机械刺激增加了成骨细胞和骨细胞中Cx43的表达、缝隙连接通讯和半通道开放。根据这一证据，推测Cx43是成骨细胞和骨细胞中由药物、激素和机械刺激激活的信号通路的重要组成部分，它通过参与半月板或缝隙连接或其支架特性而激活。这一假设将通过体外和体内相结合的方法进行验证。目标1的研究将使用选择性激活双膦酸类化合物的双膦酸类化合物来研究Cx43/(-arrestin/ERK)途径与双膦酸骨作用的体内相关性；他们将描绘Cx43、ERKs和(-arrestin)的结合导致ERKs滞留在核外和Cx43内化的机制。Aim 2的研究将通过检测间歇给予Cx43缺陷小鼠的合成代谢作用是否由于PTH不能阻止成骨细胞凋亡来确定Cx43在体内PTH抗凋亡作用中的作用。目的3将确定Cx43半通道在体内和体外的机械转导中的作用。这将通过研究Cx43缺陷小鼠的基因表达变化和对机械负荷的合成代谢反应是否发生改变，以及Cx43是否在体外成骨细胞和骨细胞的机械刺激效果中所必需的来完成。我们期待这项工作将为改善骨脆性增加的疾病的治疗提供机会。公共卫生相关性：这些研究将促进我们对Cx43在骨骼对药物治疗、激素和机械刺激的反应中的作用的理解。我们期待这项工作将为改善骨脆性增加的疾病的治疗提供机会。