MG53-mediated membrane repair in muscle physiology and disease

 描述(申请人提供)：细胞膜修复是正常生理的一个重要方面，这一过程的中断可导致包括肌肉营养不良在内的许多人类疾病的病理生理学。我们先前确定MG53是细胞膜修复机制的重要组成部分。在上一次资助期间，我们发现MG53中关键的半胱氨酸残基和亮氨酸拉链基序参与了细胞膜修复的成核过程；非肌肉肌球蛋白IIa(NM-IIa)充当分子马达，将含有MG53的囊泡运送到损伤部位；PTRF使MG53修复机制能够锚定和靶向损伤的膜。除了MG53的细胞内作用外，细胞膜的损伤还暴露了一个可以被循环的MG53检测到的信号，当提供给细胞外空间时，重组人(Rh)MG53蛋白可以修复膜损伤。为了开发MG53作为治疗肌肉疾病的潜在治疗剂，我们建立了扩大生产rhMG53的化学、制造和控制(CMC)工艺，以支持我们的临床前和未来的临床研究。显然，如果不了解MG53在循环中控制的细胞过程和细胞外MG53在组织保护中的机械作用，我们的翻译方法就不能继续进行。具体来说，a)循环中的MG53如何识别组织损伤部位，以促进对肌肉损伤的保护，并提高其在应激条件下的存活率？B)控制MG53在血液循环中的分泌、运输和清除的细胞过程是什么？C)循环中MG53的持续升高能否为改善肌营养不良的慢性过程提供有益的效果？我们最近建立了循环中控制分泌MG53的转基因小鼠模型，可以用来检测MG53在生理和病理条件下对肌肉损伤的保护作用。这一新的应用将集中于检验这一假说，即循环中的MG53通过膜分隔的信号通路保护肌肉损伤，控制MG53的分泌、运输和从血流中的清除可能为退行性肌肉疾病的治疗提供替代途径。我们建议验证肌肉是分泌MG53以保护组织的旁分泌器官的概念，肾脏介导的MG53的排泄是调节循环中MG53水平的关键因素。我们的转基因小鼠模型允许量身定做地控制MG53的分泌，提供了检查循环MG53在改善MDX小鼠肌营养不良病理方面的有效性的方法，以及评估持续MG53影响其他器官功能的安全性。

 DESCRIPTION (provided by applicant): Cell membrane repair is an important aspect of normal physiology, and disruption of this process can result in pathophysiology in a number of human diseases including muscular dystrophy. We previously identified MG53 as an essential component of the cell membrane repair machinery. During the last funding period, we showed that critical cysteine residues and leucine-zipper motifs in MG53 participate in the nucleation process of cell membrane repair; non-muscle myosin type IIa (NM-IIa) acts as a molecular motor to transport MG53- containing vesicles toward the injury site; and PTRF enables anchoring and targeting of the MG53-repair machinery at the injured membrane. In addition to the intracellular action of MG53, injury to the cell membrane exposes a signal that can be detected by circulating MG53, allowing recombinant human (rh)MG53 protein to repair membrane damage when provided in the extracellular space. To develop MG53 as a potential therapeutic agent for treatment of muscle diseases, we have established the chemistry, manufacture and control (CMC) process for scale-up production of rhMG53 to support our pre-clinical and future clinical studies. Clearly, our translational approach cannot proceed without understanding the cellular processes that underlie the control of MG53 in circulation and the mechanistic action of extracellular MG53 in tissue protection. Specifically, a) how does circulating MG53 recognize the tissue injury site to facilitate protection against muscle injury an improve its survival under stress conditions? b) what are the cellular processes that control secretion, transport and clearance of MG53 in blood circulation? c) can sustained elevation of circulating MG53 provide beneficial effects to ameliorate the chronic process of muscular dystrophy? We have recently established a transgenic mouse model with controlled secretion of MG53 in circulation that can be used to examine the function for MG53 in protection against muscle injury in physiological and pathological conditions. This renewal application will focus on testing the hypothesis that "MG53 in circulation protects muscle injury through membrane-delimited signaling pathways, and controlling MG53 secretion, transport and clearance from the blood stream may provide alternative ways for treatment of degenerative muscular diseases". We propose to test the concept that muscle is a paracrine organ that secretes MG53 for tissue protection and renal-mediated excretion of MG53 is a key factor that regulates MG53 levels in circulation. Our transgenic mouse model allows for tailored control of MG53 secretion, providing ways to examine the efficacy for circulating MG53 in ameliorating the pathology of muscular dystrophy in the mdx mice, as well as for evaluating the safety profile for sustained MG53 in affecting other organ functions.