CELLULAR ENERGETICS AS A REGULATOR OF MUSCLE MASS AND MITOCHONDRIAL CONTENT DURING MUSCLE ATROPHY

项目摘要 骨骼肌萎缩是许多慢性疾病致残和死亡的主要原因，例如癌症、糖尿病和 血栓和心力衰竭。尽管有不同的病因，萎缩的肌肉有许多共同的特征，比如 线粒体含量和抑制的能量状态。一种可能的肌肉质量和有丝分裂的调节器- 萎缩期间的DRIA是代谢酶AMP脱氨酶(AMPD)，它的亚型3增加到100- 萎缩时折叠。AMPD催化AMP的热力学不可逆降解，因此也 控制腺核苷酸(↔、ADP、↔、AMP)池的大小。结合或降解AMP是粒子- 非常重要，因为它的游离，胞浆水平是由能量感受酶AMP激活的前... 蛋白激酶(AMPK)，一种众所周知的线粒体含量的诱导剂。因此，AMPD3具有独特的定位 调节一个主要的细胞内能量信号，[AMP]/[ATP]比率。到目前为止，将 肌肉萎缩、细胞能量学和线粒体生物发生在很大程度上是未知的。的长期目标是 该项目旨在确定新的目标，以增加肌肉质量，线粒体含量，并可能改善 萎缩肌肉的能量状态和功能。此应用程序的目标是确定在 肌肉萎缩时，AMPD3会减少线粒体的生成，加速肌肉蛋白质的丢失。中环 假说认为，高水平的AMPD3，它降解腺嘌呤核苷酸池，触发丝裂原核酸库的丢失。 软骨病，增加蛋白质的降解率。这在一定程度上基于令人兴奋的初步数据，这些数据来自 培养的肌肉显示，AMPD3的过表达模拟了萎缩的能量缺乏，增加了蛋白质的含量。 而成年肌肉中AMDP3的敲除对小鼠有保护作用。 失神经萎缩，体重减轻。为了检验中心假设，我们建议取消或删除 在骨骼肌纤维/细胞中，由于各种能量侮辱而不萎缩或萎缩的AMPD3： 要么手术切断一条后肢的神经(减少能量需求)，要么剥夺食物(减少能量 以及糖皮质激素治疗(需求增加，供应减少)。这项提议的目的是 目的：1)确定AMP脱氨酶在骨骼肌线粒体丢失中的中介作用 萎缩，以及2)确定AMP脱氨酶在骨骼肌中作为蛋白质丢失的中介的作用。 罗菲。工作假说是在萎缩过程中AMPD3的丢失将增加[AMP]，线粒体生物... Genesis和线粒体含量。相反，AMPD3的过度表达，由于细胞内的损伤 能量，会加速蛋白质降解和肌肉纤维大小的损失。这一预期的结果是 该提案展示了对肌肉萎缩的精力充沛的控制，不仅将为如何 能量学/新陈代谢和肌肉质量是机械联系在一起的，但也有望揭示出新的 治疗目标，以减缓或停止肌肉质量损失的大多数，如果不是全部萎缩的情况。

Project Summary Skeletal muscle atrophy is a major cause of disability and death in many chronic diseases, e.g. cancer, diabe- tes, and heart failure. Despite diverse etiology, atrophying muscles share many common features, like loss of mitochondrial content and depressed energetic state. One probable regulator of muscle mass and mitochon- dria during atrophy is the metabolic enzyme AMP deaminase (AMPD), which isoform 3 is increased up to 100- fold during atrophy. AMPD catalyzes the thermodynamically irreversible degradation of AMP and thereby also controls the size of the adenine nucleotide (ATP ↔ ADP ↔ AMP) pool. Binding or degrading AMP is particu- larly important since its free, cytosolic levels are detected by the energy sensing enzyme AMP-activated pro- tein kinase (AMPK), a well-described inducer of mitochondrial content. Thus, AMPD3 is uniquely positioned to modulate a major intracellular energetic signal, [AMP]/[ATP] ratio. To date, the molecular mechanisms that link muscle atrophy, cellular energetics, and mitochondria biogenesis are largely unknown. The long-term goal of this project is to identify new targets to increase muscle mass, mitochondrial content and perhaps improve the energetic state and function of atrophic muscle. The objective of this application is to determine whether during muscle atrophy AMPD3 decreases mitochondrial production and accelerates muscle protein loss. The central hypothesis is that high levels of AMPD3, which degrades the adenine nucleotide pool, triggers loss of mito- chondria and increases the rate of protein degradation. This is based, in part, on exciting preliminary data from cultured muscle showing that overexpression of AMPD3 mimics the energy deficit of atrophy, increases prote- olysis rate, and decreases protein content; while knockdown of AMDP3 in adult muscle protects against mus- cle weight loss of denervation atrophy. To test the central hypothesis, we propose to knockdown or remove AMPD3 in skeletal muscle fibers/cells that are non-atrophying or atrophying due to various energetic insults: either surgical denervation of one hindlimb (decreased energy demand), food deprivation (decreased energy supply), and glucocorticoid treatment (increase in demand and decrease in supply). The Aims of this proposal are to 1) To determine the role of AMP deaminase as a mediator of mitochondrial loss during skeletal muscle atrophy, and 2) determine the role of AMP deaminase as a mediator of protein loss during skeletal muscle at- rophy. The working hypotheses are that loss of AMPD3 during atrophy will increase [AMP], mitochondrial bio- genesis, and mitochondrial content. Conversely, overexpression of AMPD3, because of impairment in cellular energetics, will trigger accelerated protein degradation and muscle fiber size loss. The expected results of this proposal, demonstrating the energetic control of muscle atrophy, will not only provide novel insights into how energetics/metabolism and muscle mass are linked mechanistically, but will also be expected to reveal novel therapeutic targets to slow or stop muscle mass loss in most, if not all, atrophy conditions.