Role of Mitochondrial Quality Control in Bone Homeostasis and Disease

项目总结/摘要 成骨细胞和破骨细胞中线粒体质量控制的改变与骨量丢失有关 与衰老和雌激素缺乏有关-这是人类骨质疏松症的两个最重要的原因， 然而，其内在机制仍不清楚。Sirtuin-3（Sirt 3）是线粒体的主要蛋白质， 脱乙酰酶，并在线粒体质量控制，包括线粒体生物发生， 线粒体动力学和线粒体自噬--所有这些都在与年龄相关的代谢疾病中受到影响。早些时候 旨在阐明Sirt 3在骨中的作用的工作产生了与一些研究相矛盾的结果， Sirt 3对骨骼内稳态至关重要，而其他人发现Sirt 3在骨骼中没有生理作用。我们有 显示小鼠中Sirt 3的缺失或Sirt 3的药理学抑制防止了由Sirt 3引起的骨量损失， 衰老和雌激素缺乏，这与骨吸收减少有关。破骨细胞缺乏 Sirt 3表现出线粒体自噬受损和线粒体自噬蛋白PTEN诱导的激酶1乙酰化增加 （PINK1）.此外，线粒体自噬抑制剂mdivi-1模拟Sirt 3缺失或Sirt 3抑制对细胞凋亡的影响。 破骨细胞生成和骨吸收。我们还获得了蛋白质组学证据，表明 Sirt 3缺失对骨量的保护作用是通过其翻译后调节ATP酶介导的 抑制因子1（ATPIF 1），一种线粒体自噬必需蛋白。值得注意的是，ATPIF 1沉默破骨细胞祖细胞 表现出受损的多核体形成和再吸收活性以及减少的线粒体自噬。我们假设 Sirt 3介导的ATPIF 1去乙酰化通过PINK 1依赖性或 独立的线粒体自噬，这一过程有助于发生过度的骨吸收 衰老和雌激素缺乏在目标1中，我们将确定Sirt 3/PINK 1介导的对细胞凋亡的贡献。 线粒体自噬对PINK 1功能丧失的老年或卵巢切除小鼠骨质疏松症的发展的影响。我们 还将使用线粒体报告小鼠在体内定量线粒体自噬和线粒体结构。在Aim中 我们将确定ATPIF 1在Sirt 3对破骨细胞功能的作用中的作用。成功完成 这项工作应该建立新的分子和细胞机制，有助于破骨细胞的功能， 骨质疏松这些研究还应该阐明Sirt 3在年龄增长中以前未被认识到的有害作用。 相关的代谢性疾病。

PROJECT SUMMARY/ABSTRACT Altered mitochondria quality control in osteoblasts and osteoclasts has been implicated in the loss of bone mass associated with aging and estrogen deficiency – the two most important causes of osteoporosis in humans, however the underlying mechanisms remain unclear. Sirtuin-3 (Sirt3) is the primary mitochondrial protein deacetylase and plays a critical role in mitochondrial quality control, including mitochondrial biogenesis, mitochondrial dynamics, and mitophagy—all of which are affected in age-related metabolic diseases. Earlier work aiming to elucidate the role of Sirt3 in bone has produced conflicting results with some studies suggesting that Sirt3 is critical for skeletal homeostasis while others found no physiological role of Sirt3 in bone. We have shown that deletion of Sirt3 or pharmacologic inhibition of Sirt3 in mice prevents the loss of bone mass caused by aging and estrogen deficiency and this is associated with decreased bone resorption. Osteoclasts lacking Sirt3 exhibit impaired mitophagy and increased acetylation of the mitophagy protein PTEN-induced kinase 1 (PINK1). Moreover, the mitophagy inhibitor mdivi-1 mimics the effects of Sirt3 deletion or Sirt3 inhibition on osteoclast generation and bone resorption. We have also obtained proteomic evidence to suggest that the protective effects of Sirt3 deletion on bone mass are mediated by its posttranslational regulation of ATPase inhibitory factor 1 (ATPIF1), an essential protein for mitophagy. Notably, ATPIF1 silencing osteoclast progenitors exhibit impaired polykaryon formation and resorptive activity as well as decreased mitophagy. We hypothesize that Sirt3-mediated deacetylation of ATPIF1 promotes osteoclast function via PINK1-dependent or independent mitophagy and that this process contributes to the excessive bone resorption that occurs with aging and estrogen deficiency. In Aim 1 we will determine the contribution of Sirt3/PINK1-mediated mitophagy to the development of osteoporosis in aged or ovariectomized mice with PINK1 loss-of-function. We will also quantify mitophagy and mitochondrial architecture in vivo using a mitochondria reporter mouse. In Aim 2 we will determine the role of ATPIF1 in the actions of Sirt3 on osteoclast function. Successful completion of this work should establish novel molecular and cellular mechanisms that contribute to osteoclast function and osteoporosis. These studies also should elucidate a previously unappreciated deleterious role of Sirt3 in age- related metabolic diseases.