TRB3: A Novel Mediator for Denervation-induced Muscle Atrophy

 描述（由申请人提供）：肌肉萎缩是人类中一种突出且使人衰弱的医学病症，但启动该过程的信号分子尚未阐明。我们的目标是鉴定调节蛋白质合成和/或蛋白质降解途径的新分子，从而调节肌肉质量。我们在这项研究中假设TRB 3介导去神经诱导的骨骼肌萎缩，并且TRB 3的抑制改善了肌肉质量的损失。这一假设是基于初步数据制定的，这些数据表明TRB 3表达是由肌肉去神经支配诱导的，并且TRB 3的过表达抑制Akt活性。此外，在小鼠中敲除TRB 3导致Akt活性增加和F0 XO功能降低。我们将通过追求两个具体目标来检验这一假设。在目标1中，我们将确定TRB 3表达和功能对骨骼肌去神经支配的反应。在此基础上，我们将利用电穿孔技术在骨骼肌中过表达TRB 3，建立肌肉特异性TRB 3转基因小鼠模型，并对失神经诱导的骨骼肌萎缩进行研究。根据我们的初步数据，我们预计TRB 3在肌肉中的过表达会加重肌肉萎缩。在目标2中，我们将确定TRB 3抑制是否可以预防去神经诱导的骨骼肌萎缩。为此，我们将研究TRB 3基因敲除小鼠，以确定小鼠是否对去神经诱导的肌肉质量损失具有抵抗力。我们还将确定敲除小鼠中的蛋白质合成和Akt活性。我们期望TRB 3的敲除将通过消除响应于肌肉去神经的蛋白质合成和Akt活性的降低来防止小鼠发生去神经诱导的肌肉萎缩。这项研究将建立TRB 3对肌肉萎缩的新功能，并确定治疗肌肉萎缩的新方法。此外，该研究还将提供证据来研究TRB 3在与肌肉萎缩相关的其他肌肉疾病中的作用，包括肌肉废用、恶病质和肌肉减少症。该研究将在以下方面具有创新性：1）提出对肌肉萎缩发展的细胞和分子病因学的新见解; 2）研究模拟功能获得（TRB 3转基因小鼠）和功能丧失（TRB 3敲除小鼠）的独特动物; 3）研究TRB 3对肌肉质量调节的新功能。拟议的研究也将是重要的，在提供新的见解肌肉萎缩的发病机制，并在持有的承诺，为发展的药理学药物，可以防止肌肉萎缩在广泛的疾病状态。此外，我们将从该项目中获得的知识可以应用于与肌肉萎缩直接或间接相关的其他肌肉疾病。

 DESCRIPTION (provided by applicant): Muscle atrophy is a prominent and debilitating medical condition in humans, but the signaling molecules that initiate this process have not been elucidated yet. Our goal is to identify novel molecule(s) that regulate pathways involved in protein synthesis and/or protein degradation, leading to regulation of muscle mass. We hypothesize in this study that TRB3 mediates denervation-induced skeletal muscle atrophy and that inhibition of TRB3 ameliorates the loss of muscle mass. This hypothesis has been formulated on the basis of preliminary data showing that TRB3 expression is induced by muscle denervation and that overexpression of TRB3 inhibits Akt activity. Furthermore, knockout of TRB3 in mice results in increased Akt activity and decreased FOXO function. We will test the hypothesis by pursing two specific aims. In Aim 1, we will determine TRB3 expression and function in response to skeletal muscle denervation. Under this aim, we will overexpress TRB3 in skeletal muscle using electroporation technique and muscle-specific TRB3 transgenic mice, and assess the denervation-induced muscle atrophy. Guided by our preliminary data, we anticipate that overexpression of TRB3 in muscle will worsen muscle atrophy. In Aim 2, we will determine if TRB3 inhibition prevents denervation-induced skeletal muscle atrophy. To this end, we will study TRB3 knockout mice to determine if the mice are resistant to denervation-induced muscle mass loss. We will also determine protein synthesis and Akt activity in the knockout mice. We expect that knockout of TRB3 will prevent mice from developing denervation-induced muscle atrophy through ablation of decreases in protein synthesis and Akt activity in response to muscle denervation. The proposed research will establish the novel function of TRB3 on muscle atrophy and identify a new approach for treating muscle atrophy. In addition, the study will provide evidence to investigate the role of TRB3 in other muscle diseases related to muscle atrophy, including muscle disuse, cachexia, and sarcopenia. The study will be innovative in 1) proposing new insight into the cellular and molecular etiology of muscle atrophy development; 2) studying unique animals that model both Gain-of- function (TRB3 transgenic mice) and Loss-of-function (TRB3 knockout mice); and 3) investigating a novel function of TRB3 on muscle mass regulation. The proposed study will be also significant in providing new insights into the pathogenesis of muscle atrophy and in holding promise for the development of pharmacological agents that could prevent muscle atrophy during a wide range of diseased states. Furthermore, the knowledge that we will gain from this project can be applied to other muscle diseases that are directly or indirectly related to muscle atrophy.