Tetraspanin CD82 in muscle satellite cells quiescence and differentiation

摘要/摘要 Tetraspanins是已知的调节蛋白质聚集的一个重要蛋白质家族。 细胞膜上的复合体。已知的是，Tetraspanins可以在细胞内结合和招募其他蛋白质 表面，如整合素和细胞黏附分子，从而启动重要的细胞决策，包括 迁移、黏附和信号激活。我们的初步数据表明，Tetraspanin CD82 是由肌肉卫星细胞表达的，在那里它与~250Kd的蛋白质复合体中的其他蛋白质结合。其中之一 该蛋白成员为α7-整合素(α7-itg)。培养的α7-ITG小鼠成肌细胞减少 CD82的表达，提示这两种蛋白之间存在功能联系。此外，肌肉组织 营养不良的mdx和α7-ITG缺陷型小鼠的裂解产物显示CD82-α7-ITG几乎不存在 蛋白质复合体与野生型骨骼肌相比。最后，来自CD82基因敲除的肌肉卫星细胞 老鼠在细胞增殖方面表现出缺陷。在本申请中，我们建议标识附加的 CD82-α7-ITG复合体的成员，研究卫星细胞中CD82的翻译后修饰 并测定正常卫星细胞(Aim1)中该复合体的化学计量比。在目标2中，我们将确定 导致CD82基因敲除卫星细胞增殖受损的CD82下游信号通路 细胞。我们将调查这些分子是α7-ITG的下游信号效应器，还是无关 至α7-itg功能。最后，在目标3中，我们将研究在卫星细胞中过表达CD82是否可以 增强其体内修复能力，改善营养不良肌肉的整体功能。这些 研究将促进我们对这种特定的Tetraspanin在卫星细胞活动中的作用的理解，并将 为未来旨在增强CD82蛋白表达的治疗提供基础 营养不良肌肉的复合体。

SUMMARY/ABSTRACT The tetraspanins constitute an important family of proteins known to regulate the aggregation of protein complexes at the cell membrane. Tetraspanins are known to bind and recruit other proteins at the cell surface, such as integrins and cell adhesion molecules, thus initiating important cell decisions including migration, adhesion and signaling activation. Our preliminary data demonstrate that the tetraspanin CD82 is expressed by muscle satellite cells where it binds to other proteins in a ~250Kd protein complex. One of the protein members is α7-integrin (α7-ITG). Cultured myoblasts from α7-ITGnull mice show decreased expression of CD82, suggesting a functional link between these two proteins. Additionally, muscle tissue lysates from dystrophic mdx and α7-ITGnull mice show a decrease to near absence of the CD82-α7-ITG protein complex compared to wild-type skeletal muscle. Lastly, muscle satellite cells from CD82 knockout mice show a defect in cell proliferation. In the present application we propose to identify the additional members of the CD82-α7-ITG complex, study the post-translational modifications of CD82 in satellite cells and determine the stoichiometry of the complex in normal satellite cells (Aim1). In Aim 2, we will identify the downstream signaling pathways of CD82 that lead to impaired cell proliferation of CD82 knockout satellite cells. We will investigate if these molecules are downstream signaling effectors of α7-ITG, or are unrelated to α7-ITG function. Finally, in Aim 3 we will study whether overexpression of CD82 in satellite cells can enhance their in vivo reparative capacity and improve the overall function of dystrophic muscle. These studies will advance our understanding on the role of this specific tetraspanin in satellite cell activity and will provide the groundwork for future therapies aimed at enhancing the expression of the CD82 protein complex in dystrophic muscle.