A Proteomic Screen for Muscle E3 LigaseSubstrates in Cachexia.

描述（由申请人提供）：与癌症相关的肌肉萎缩的治疗对癌症患者的临床护理和管理提出了巨大挑战。在药理学上，癌症的这一方面已被证明是神秘的，因为恶病质背后的蛋白质降解程序的分子细节尚未阐明。最近的研究表明，包括癌症在内的许多疾病中的肌肉萎缩主要是由于泛素蛋白酶体系统激活引起的蛋白水解增加。 我们确定了一个干部的E3连接酶的转录调控MyoD1，肌发生的主调节器，在成肌细胞和成肌细胞肌管过渡使用基因组转录因子结合（ChIP芯片）分析。我们假设这些E3连接酶在肌肉稳态中正常发挥作用，并且癌症中的肌肉萎缩可能部分是由于肌肉特异性E3连接酶的不适当的持续激活。因此，这些E3连接酶（及其调节剂）可以代表治疗癌症和其他疾病中肌肉萎缩的可行药物靶标。在这里，我们将在两个具体目标中探讨这一假设。首先，我们将使用地塞米松治疗作为肌肉萎缩的组织培养模型，在完全分化的C2C12肌管中对Rnf11（先前在我们的MyoD1基因组筛选中鉴定的E3连接酶组成员）的底物进行蛋白质组学筛选。其次，我们将尝试验证这些假定的底物的泛素化RNF 11 E3连接酶在体外和我们的肌肉萎缩的组织培养模型。该提案旨在开发创新的和以前未探索的方法来对抗与癌症相关的肌肉萎缩，因此为其临床管理提供了新的可能性。

DESCRIPTION (provided by applicant): Treatment of muscle wasting associated with cancer poses a great challenge in the clinical care and management of cancer patients. Pharmacologically, this aspect of cancer has proven enigmatic, as the molecular details of the protein degradation programs underlying cachexia have not been elucidated. Recent studies have shown that muscle wasting in a number of diseases, including cancer, is principally due to an increase in proteolysis caused by activation of the ubiquitin proteasome system. We identified a cadre of E3 ligases that are transcriptionally regulated by MyoD1, a master regulator of myogenesis, in myoblasts and during the myoblast to myotube transition using genomic transcription factor binding (ChIP-on-chip) analyses. We hypothesize that these E3 ligases normally function in muscle homeostasis and that muscle wasting in cancer may be due in part to inappropriate, sustained activation of muscle-specific E3 ligases. Thus, these E3 ligases (and their regulators) could represent viable drug targets in the treatment of muscle wasting in cancer and other diseases. Here, we will explore this hypothesis in two specific aims. First, we will conduct a proteomic screen for substrates of Rnf11, a member of the group of E3 ligases previously identified in our MyoD1 genomic screen, in fully differentiated C2C12 myotubes using dexamethasone treatment as a tissue culture model of muscle atrophy. Second, we will attempt to validate ubiquitylation of these putative substrates by the Rnf11 E3 ligase in vitro and in our tissue culture model of muscle atrophy. This Proposal is designed to develop innovative and previously unexplored approaches to combat muscle wasting associated with cancer and therefore presents novel possibilities for its clinical management.