Regulation of apoptosis in osteoblasts by Runx2 and NFkB

Runx2 和 NFkB 对成骨细胞凋亡的调节

• 批准号: 8466932
• 负责人: Roman Eliseev
• 金额: $ 6.69万
• 依托单位: UNIVERSITY OF ROCHESTER
• 依托单位国家: 美国
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-07-01 至 2014-05-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8466932
• 关键词: Address; Aging; Apoptosis; Apoptotic; Binding; Biological Assay; Bone Tissue; Bone neoplasms; Cell Line; Cell Proliferation; Cells; DNA Binding; Data; EMSA; Elements; Equilibrium; Future; Genes; Genetic Transcription; Goals; Growth; Homeostasis; Life Cycle Stages; Literature; Malignant Bone Neoplasm; Mesenchymal Stem Cells; Mitotic; Molecular; Mus; Mutagenesis; NF-kappa B; Neoplasms; Osteoblasts; Osteocytes; Play; Proliferating; Regulation; Reporter; Repression; Response Elements; Role; Signal Transduction; base; bone; bone cell; cytokine; expression vector; inhibitor/antagonist; insight; loss of function; novel; osteoblast differentiation; osteosarcoma; p65; promoter

DESCRIPTION (provided by applicant): Delicate balance between cellular proliferation, differentiation and apoptosis is required for normal bone tissue composition and function. Disruption of such balance leads to bone neoplasia or degeneration. Our long-term goal is to elucidate the mechanisms of disregulation of apoptosis in bone neoplasms and find novel treatments targeted at modulation of apoptosis in neoplasia. The goal of this proposal is to expand our previous findings on counter-regulation of apoptosis in osteoblasts (OB) by Runx2 and NF-kB that will serve as preliminary data for our future RO1 project. During growth and remodeling of bone tissue, bone cells differentiate from mesenchymal stem cells to early proliferating OBs to mature post-mitotic OBs of which 30 percent become either osteocytes or lining cells while 70 percent are eliminated by apoptosis. OB apoptosis is, therefore an ultimate part of OB life cycle which is regulated by the microenvironment and bone-specific cytokines. Despite the importance of apoptosis in bone homeostasis, its regulation in OBs remains elusive. We have collected new data indicating that: 1) A key OB differentiation factor, Runx2, also plays a central role in regulation of OB apoptosis by inducing pro-apoptotic Bax via direct binding and activation of the bax gene promoter; 2) Apoptosis is increased in more differentiated OBs in concert with the increase in Runx2 and Bax; 3) Induction of Bax by Runx2 is negatively regulated by the NF-kB signaling. Bax promoter contains NF-kB binding elements; and 4) NF-kB activity is increased in proliferating OBs and in osteosarcoma cells and plays a role in suppression of apoptosis. In addition, others have found that in Bax KO mice, bone volumes are significantly increased in aging mice implicating Bax in regulation of OB function. In this proposal we will determine the specific role of the Runx2/Bax axis in regulation of apoptosis in OBs and get an insight on the role of NF-kB as a modulator of the Runx2/Bax apoptotic axis. Based on our preliminary results and the literature we hypothesize that apoptosis in osteoblasts is counter-regulated by Runx2 and NF-kB which correspondingly induce or repress transcription of pro-apoptotic Bax. To prove our hypothesis we will address the two Specific Aims: 1) To confirm the inhibitory role of NF-kB in regulation of Bax transcription; and 2) To elucidate the effect of interaction of the Runx2/Bax axis with NF-kB on apoptosis sensitivity in osteoblasts and in osteosarcoma cells. This proposal seeks to understand regulatory mechanisms involved in OB apoptosis and how the Runx2/Bax axis and NF-kB interact at the molecular level. This will provide us a rationale for a RO1 project focused on the mechanism of suppression of apoptosis in bone cancer. 1

描述（由申请人提供）：正常骨组织组成和功能需要细胞增殖、分化和凋亡之间的微妙平衡。这种平衡的破坏导致骨肿瘤或骨退化。我们的长期目标是阐明骨肿瘤细胞凋亡失调的机制，并找到新的治疗靶向肿瘤细胞凋亡的调制。该提案的目标是扩展我们先前关于Runx 2和NF-kB反调节成骨细胞（OB）凋亡的研究结果，这将作为我们未来RO 1项目的初步数据。 在骨组织的生长和重塑过程中，骨细胞从间充质干细胞分化为早期增殖的OB，再分化为成熟的有丝分裂后OB，其中30%成为骨细胞或衬里细胞，而70%通过凋亡被消除。因此，成骨细胞凋亡是成骨细胞生命周期的最终部分，其受微环境和骨特异性细胞因子的调节。尽管细胞凋亡在骨稳态中的重要性，但其在OB中的调节仍然是难以捉摸的。我们已经收集了新的数据，表明：1）一个关键的OB分化因子，Runx 2，也发挥了核心作用，通过诱导促凋亡Bax通过直接结合和激活的bax基因启动子的OB细胞凋亡的调节; 2）细胞凋亡的增加，在更分化的OB与Runx 2和Bax的增加; 3）由Runx 2诱导Bax的NF-κ B信号负调控。Bax启动子含有NF-κ B结合元件; 4）NF-κ B活性在增殖的OB和骨肉瘤细胞中增加，并在抑制凋亡中起作用。此外，其他人已经发现，在Bax KO小鼠中，老龄小鼠的骨体积显著增加，暗示Bax调节OB功能。在这个提议中，我们将确定Runx 2/Bax轴在OB细胞凋亡调控中的具体作用，并深入了解NF-κ B作为Runx 2/Bax凋亡轴调节剂的作用。 根据我们的初步结果和文献，我们假设成骨细胞的凋亡是由Runx 2和NF-κ B的反调节，相应地诱导或抑制促凋亡Bax的转录。为了证明我们的假设，我们将解决两个具体的目的：1）证实NF-κ B在Bax转录调控中的抑制作用; 2）阐明Runx 2/Bax轴与NF-κ B的相互作用对成骨细胞和骨肉瘤细胞凋亡敏感性的影响。 该提案旨在了解OB凋亡的调控机制以及Runx 2/Bax轴和NF-kB如何在分子水平上相互作用。这将为我们提供一个RO 1项目的基本原理，重点是在骨癌细胞凋亡的抑制机制。1