TWEAK/Fn14/UPR Signaling in Skeletal Muscle Wasting

摘要 骨骼肌萎缩/恶病质是许多慢性疾病的毁灭性并发症 如癌症和老年人。肌肉萎缩是指 蛋白质合成和降解的速率，功能性去神经支配，代谢异常， 以及线粒体内容和功能的丧失。TWEAK是一种促炎细胞因子， 细胞表面受体Fn 14激活多种细胞内信号通路。我们有 发现Fn 14的表达在癌症小鼠模型的骨骼肌中增加 恶病质和老年小鼠。骨骼肌特异性Fn 14消融抑制骨骼肌萎缩 癌症恶病质的小鼠模型。TWEAK抑制骨骼肌中蛋白质合成的速率 肌肉在体内和体外。此外，TWEAK-Fn 14系统调节ER应激- 在荷瘤小鼠的骨骼肌中诱导未折叠蛋白反应（UPR）。此外，本发明还提供了一种方法， 我们的实验表明，靶向抑制PERK和/或IRE 1/XBP 1臂， UPR改善小鼠骨骼肌中的蛋白质合成。然而， TWEAK-Fn 14系统和UPR通路在骨骼肌质量和功能调节中的作用 在癌症恶病质和衰老期间仍然完全未知。在这个项目中，我们将 研究TWEAK/Fn 14/UPR信号轴在骨骼肌萎缩中的作用， Fn 14或UPR组分的靶向基因消融可减轻肌肉萎缩， 癌症恶病质和衰老过程中的临床前小鼠模型。根据我们初步的 结果，我们假设TWEAK/Fn 14系统通过以下途径引起骨骼肌萎缩： 在衰老和癌症期间UPR的PERK和IRE 1 α/XBP 1臂的激活 恶病质我们的具体目标是：（I）研究TWEAK/Fn 14系统在以下方面的作用： 衰老和癌症恶病质期间骨骼肌萎缩，以及（II）研究机制 通过TWEAK/Fn 14诱导的UPR通路激活导致骨骼肌萎缩 和癌症恶病质的影响。我们提议的研究将确定关键机制 导致骨骼肌质量下降。该项目的成功完成将 为开发肌少症和癌症恶病质的新疗法提供有力依据。

ABSTRACT Skeletal muscle wasting/cachexia is a devastating complication of a number of chronic disease states, such as cancer and in the elderly population. Muscle wasting involves an imbalance in the rates of protein synthesis and degradation, functional denervation, metabolic abnormalities, and loss of mitochondrial content and function. TWEAK is a proinflammatory cytokine that binds to cell surface receptor Fn14 to activate multiple intracellular signaling pathways. We have found that the expression of Fn14 is increased in skeletal muscle of mouse models of cancer cachexia and in aged mice. Skeletal muscle-specific ablation of Fn14 inhibits muscle wasting in a murine model of cancer cachexia. TWEAK represses the rate of protein synthesis in skeletal muscle both in vivo and in vitro. Furthermore, the TWEAK-Fn14 system regulates ER stress- induced unfolded protein response (UPR) in skeletal muscle of tumor-bearing mice. In addition, our experiments demonstrate that targeted inhibition of the PERK and/or IRE1/XBP1 arms of the UPR improves protein synthesis in skeletal muscle of mice. However, the role of the TWEAK-Fn14 system and UPR pathways in the regulation of skeletal muscle mass and function during cancer cachexia and aging remains completely unknown. In this project, we will investigate the role of TWEAK/Fn14/UPR signaling axis in skeletal muscle atrophy and whether targeted genetic ablation of Fn14 or components of the UPR attenuate muscle wasting in preclinical mouse models of cancer cachexia and during aging. Based on our preliminary results, we hypothesize that the TWEAK/Fn14 system causes skeletal muscle wasting through the activation of the PERK and the IRE1α/XBP1 arms of the UPR during aging and cancer cachexia. Our specific aims are to: (I) Investigate the role of the TWEAK/Fn14 system in skeletal muscle wasting during aging and cancer cachexia, and (II) Investigate the mechanisms by which TWEAK/Fn14-induced activation of the UPR pathways cause skeletal muscle wasting during aging and cancer cachexia. Our proposed studies will identify key mechanisms responsible for the loss of skeletal muscle mass. Successful completion of this project will provide strong basis for the development of new therapies for sarcopenia and cancer cachexia.