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: 8177970
• 负责人: Roman Eliseev
• 金额: $ 7.73万
• 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/8177970
• 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。这种平衡的破坏会导致骨肿瘤或退化。我们的长期目标是阐明骨肿瘤细胞凋亡失调的机制，并找到针对肿瘤细胞凋亡调节的新疗法。该提案的目标是扩展我们之前关于 Runx2 和 NF-kB 反调节成骨细胞 (OB) 细胞凋亡的发现，这将作为我们未来 RO1 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，再到成熟的有丝分裂后 OB，其中 30% 成为骨细胞或衬里细胞，而 70% 则通过细胞凋亡消除。因此，OB 细胞凋亡是 OB 生命周期的最终部分，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很重要，但其在 OB 中的调节仍然难以捉摸。我们收集到的新数据表明：1）关键的 OB 分化因子 Runx2 通过直接结合和激活 bax 基因启动子诱导促凋亡 Bax，在调节 OB 细胞凋亡中也发挥着核心作用； 2) 分化程度较高的 OB 中细胞凋亡随着 Runx2 和 Bax 的增加而增加； 3) Runx2 对 Bax 的诱导受到 NF-kB 信号传导的负调控。 Bax启动子含有NF-kB结合元件； 4) 增殖的 OB 和骨肉瘤细胞中 NF-kB 活性增加，并在抑制细胞凋亡中发挥作用。此外，其他人还发现，在 Bax KO 小鼠中，衰老小鼠的骨量显着增加，这表明 Bax 参与了 OB 功能的调节。在本提案中，我们将确定 Runx2/Bax 轴在 OB 细胞凋亡调节中的具体作用，并深入了解 NF-kB 作为 Runx2/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受到 Runx2 和 NF-kB 的反向调节，它们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目标：1）确认 NF-kB 在 Bax 转录调节中的抑制作用； 2) 阐明 Runx2/Bax 轴与 NF-kB 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 细胞凋亡中涉及的调控机制以及 Runx2/Bax 轴和 NF-kB 如何在分子水平上相互作用。这将为我们关注骨癌细胞凋亡抑制机制的 RO1 项目提供依据。 1