Role of Mitochondrial Quality Control in Bone Homeostasis and Disease

项目概要/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损失有关 与衰老和雌激素缺乏有关——人类骨质疏松症的两个最重要原因， 然而，其根本机制仍不清楚。 Sirtuin-3 (Sirt3) 是主要的线粒体蛋白 脱乙酰酶在线粒体质量控制中发挥着关键作用，包括线粒体生物发生， 线粒体动力学和线粒体自噬——所有这些都受到与年龄相关的代谢疾病的影响。早些时候 旨在阐明 Sirt3 在骨骼中的作用的工作产生了与一些研究表明的相互矛盾的结果 Sirt3 对于骨骼稳态至关重要，而其他人则发现 Sirt3 在骨骼中没有生理作用。我们有 研究表明，敲除 Sirt3 或对小鼠 Sirt3 进行药物抑制可防止小鼠骨质流失 由于衰老和雌激素缺乏，这与骨吸收减少有关。破骨细胞缺乏 Sirt3 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 （粉红色1）。此外，线粒体自噬抑制剂 mdivi-1 模拟了 Sirt3 缺失或 Sirt3 抑制对细胞的影响。 破骨细胞的生成和骨吸收。我们还获得了蛋白质组学证据表明 Sirt3 缺失对骨量的保护作用是通过其 ATP 酶的翻译后调节介导的 抑制因子 1 (ATPIF1)，线粒体自噬的必需蛋白。值得注意的是，ATPIF1 沉默破骨细胞祖细胞 表现出多核体形成和再吸收活性受损以及线粒体自噬减少。我们假设 Sirt3 介导的 ATPIF1 去乙酰化通过 PINK1 依赖性或促进破骨细胞功能 独立的线粒体自噬，并且该过程导致发生过度的骨吸收 与衰老和雌激素缺乏有关。在目标 1 中，我们将确定 Sirt3/PINK1 介导的贡献 线粒体自噬对 PINK1 功能丧失的老年或卵巢切除小鼠骨质疏松症发展的影响。我们 还将使用线粒体报告小鼠量化体内线粒体自噬和线粒体结构。瞄准 2 我们将确定 ATPIF1 在 Sirt3 对破骨细胞功能的作用中的作用。顺利完成 这项工作应该建立有助于破骨细胞功能的新分子和细胞机制 骨质疏松症。这些研究还应该阐明 Sirt3 在年龄增长中先前未被认识到的有害作用。 相关代谢性疾病。

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.