Role of Mitochondrial Quality Control in Bone Homeostasis and Disease

项目摘要/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的丢失有关 与衰老和雌激素缺乏有关--这是人类骨质疏松的两个最重要的原因， 然而，潜在的机制仍不清楚。Sirtuin-3(SIRT3)是线粒体的主要蛋白质 脱乙酰酶在线粒体质量控制中起关键作用，包括线粒体的生物发生， 线粒体动力学和有丝分裂--所有这些都会在年龄相关的代谢性疾病中受到影响。早些时候 旨在阐明SIRT3在骨骼中的作用的工作产生了相互矛盾的结果，一些研究表明 SIRT3对骨骼的动态平衡至关重要，而其他人则没有发现SIRT3在骨骼中的生理作用。我们有 在小鼠中，SIRT3的缺失或SIRT3的药物抑制可防止导致的骨量丢失 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显示吞丝分裂功能受损和吞丝分裂蛋白PTEN诱导的激酶1乙酰化增加 (PINK1)。此外，丝裂原吞噬抑制剂mdivi-1模拟SIRT3缺失或SIRT3抑制对细胞生长的影响 破骨细胞生成与骨吸收。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对ATPase的翻译后调节来实现的 抑制因子1(ATPIF1)是吞噬有丝分裂所必需的蛋白质。值得注意的是，ATPIF1使破骨细胞前体细胞沉默 表现出多核形成和吸收活性受损，吞噬线粒体数减少。我们假设 SIRT3介导的ATPIF1脱乙酰基通过PINK1依赖或促进破骨细胞功能 独立的有丝分裂，这一过程导致了过度的骨吸收 衰老和雌激素缺乏症。在目标1中，我们将确定SIRT3/PINK1介导的贡献 有丝分裂与老年或去卵巢PINK1功能丧失小鼠骨质疏松的发展。我们 还将使用线粒体报告小鼠来量化体内的有丝分裂和线粒体结构。在AIM 2我们将确定ATPIF1在SIRT3对破骨细胞功能作用中的作用。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和 骨质疏松。这些研究还应该阐明SIRT3在年龄中以前没有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.