Connexin 43 Hemichannels and Signaling In Bone

Connexin 43 半通道和骨信号传导

• 批准号: 7461108
• 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/7461108
• 关键词: Anabolism; Apoptosis; Apoptotic; Arrestin; Arrestins; Biological Preservation; Bone Mineral Contents; Bone remodeling; Cell Communication; Cell Nucleus; Cell membrane; Cells; Clathrin; Communication; Complex; Condition; 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; Numbers; Osteoblasts; Osteoclasts; Osteocytes; Osteogenesis; Parathyroid Hormones; Pathway interactions; Phosphotransferases; Prevention; Production; Property; Protein Family; Public Health; 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; 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（由申请人提供）：连接蛋白（Cx）是细胞间通讯以及细胞与其环境通讯所必需的蛋白质家族。 Cx43 是骨细胞中表达最丰富的连接蛋白。通过 Cx43 缺失小鼠胚胎中成骨细胞功能障碍和延迟骨化的证明，Cx43 表达在骨骼中的重要性已得到证实。然而，Cx43，特别是在非相对细胞膜中表达的 Cx43 半通道的作用，还远未完全了解。在导致该应用的研究中，证明双磷酸盐除了阻止破骨细胞介导的吸收外，还可以至少部分通过促进成骨细胞和骨细胞的活力来保持骨强度，并且这种生存效应需要 Cx43 表达。因此，双磷酸盐抑制细胞凋亡需要打开 Cx43 半通道、激活细胞外信号调节激酶 (ERK) 以及由于激酶与支架蛋白 (-arrestin) 相互作用而保留在核外。Cx43 也是预防细胞凋亡所必需的体外甲状旁腺激素（PTH）对成骨细胞凋亡的影响；并且在 Cx43 缺陷小鼠中，间歇性施用该激素的合成代谢反应减弱。此外，Cx43 还可能参与骨骼中的机械转导，因此，机械刺激会增加成骨细胞和骨细胞中的 Cx43 表达、间隙连接通讯和半通道开放，据此推测 Cx43 是信号通路的重要组成部分。通过参与半通道或间隙连接或其支架特性，由成骨细胞和骨细胞中的药理、激素和机械刺激激活。通过体外和体内方法的组合进行测试。目标 1 中的研究将使用选择性激活该途径的双磷酸盐类似物来检查 Cx43/(-arrestin/ERK 途径与双磷酸盐对骨作用的体内相关性；并且他们将描述 Cx43、ERK 和 (-抑制蛋白导致 ERK 保留在细胞核外，并且 Cx43 内化。目标 2 中的研究将确定 Cx43 在抗凋亡中的作用。通过检查对缺乏 Cx43 的小鼠间歇性施用 PTH 缺乏合成代谢作用是否是由于 PTH 无法防止成骨细胞凋亡来确定 PTH 的体内作用，目标 3 将确定 Cx43 半通道在体内和体外机械转导中的作用。这将通过研究 Cx43 缺陷小鼠的基因表达和合成代谢反应是否发生改变以及 Cx43 是否需要来实现；我们期望这项工作将为改善骨脆性增加疾病的治疗提供机会。公共健康相关性：这些研究将增进我们对 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。我们期望这项工作将为改善骨脆性增加疾病的治疗提供机会。