Role of Fbxw7-Mediated Proteasomal Degradation in Myofibers in Determining Muscle Stem Cell Pool Size

总结 该提案的主要目标是描绘信令网络， 肌纤维对MuSC功能的影响。MuSC，也称为卫星细胞，是骨骼肌生长的主要来源 和再生。在健康的成人组织中，MuSC以静止状态存在，并且在应激或损伤时， 激活增殖并产生大量祖细胞，以有效修复受损的肌肉。而 该过程在健康条件下、在几种疾病条件下以及在老化期间是有效的， MuSC的功能受损。因此，有一个主要的需要，了解分子网络调节 它们的功能，以确定新的工具或目标，以提高其组织修复潜力， 在再生医学的方法。近年来的重大努力确定了联合国的关键作用， 微环境在调节MuSC功能，通过揭示几个组织的综合协调- 常驻细胞，如炎性细胞、成纤维脂肪祖细胞和内皮细胞在调节MuSC中的作用 组织修复功能然而，肌纤维在组织微环境中和在MuSC中的作用 niche的定义仍然很模糊。我们的初步研究结果提供了证据，E3泛素连接酶Fbxw 7， 肌纤维以细胞非自主的方式调节MuSC池的大小，这表明肌纤维在MuSC池中起着重要作用。 在指导干细胞功能方面的主要作用。我们进一步确定PGC 1 α作为Fbxw 7的直接靶点， PGC 1 α靶向Irisin的上调，Irisin是一种促进MuSC分化的肌因子。的识别 介导肌纤维对MuSC池大小的指导作用的信号通路可以确定策略， 扩大MuSC，从而使其在再生医学方法中的使用。本申请的目的 是利用遗传模型、无偏见的蛋白质组学和泛素组分析、基因表达 分析和细胞生物学技术，以描绘信号网络介导的指导作用， 对MuSC功能的影响。待检验的中心假设是肌纤维中的Fbxw 7调节 通过改变MuSC小生境以细胞非自主方式进行MuSC编号。这一综合办法将 提高我们对肌纤维/MuSC相互作用的理解，定义介导这一过程的信号网络 并评估Fbxw 7/PGC 1 α/Irisin作为调节MuSC池大小的关键轴。

SUMMARY The over-arching goal of this proposal is to delineate the signaling networks mediating the instructive role of the myofiber on MuSC function. MuSC, also known as satellite cells, are the main source of skeletal muscle growth and regeneration. In healthy adult tissues MuSC exist in a quiescent state, and upon stress or injury they are activated to proliferate and generate large numbers of progenitors to efficiently repair damaged muscles. While this process is efficient in healthy conditions, in several diseased conditions and during aging the numbers and function of MuSC are impaired. Thus, there is a major need to understand the molecular networks regulating their function, in order to identify novel tools or targets to enhance their tissue repair potential that can be utilized in regenerative medicine approaches. Significant efforts in the recent years have defined a critical role of the microenvironment in regulating MuSC function, by uncovering the integrated coordination of several tissue- resident cells, such as inflammatory cells, fibroadipogenic progenitors and endothelial cells in regulating MuSC tissue repair function. However, the role of the myofiber within the tissue microenvironment and in the MuSC niche is still poorly defined. Our preliminary findings provide evidence that the E3 ubiquitin ligase Fbxw7 in myofibers regulates MuSC pool size in a cell non-autonomous manner, suggesting that the myofiber plays a major role in instructing stem cell function. We further identify PGC1alpha as a direct Fbxw7 target and the upregulation of the PGC1alpha target irisin, a myokine that promotes MuSC differentiation. The identification of signaling pathways that mediate the instructive role of the myofiber on MuSC pool size could identify strategies to expand MuSC, thus allowing their use in regenerative medicine approaches. The objective of this application is to take advantage of genetic models, unbiased proteomics and ubiquitinome profiling, gene expression profiling and cellular biology techniques in order to delineate the signaling networks mediating the instructive role of the myofiber on MuSC function. The central hypothesis to be tested is that the Fbxw7 in myofibers regulates MuSC numbers in a cell non-autonomous manner by altering the MuSC niche. This integrated approach will improve our understanding of myofiber/MuSC interactions, define the signaling networks mediating this process and evaluate Fbxw7/PGC1α/Irisin as a critical axis to regulate MuSC pool size.