MG53-mediated membrane repair in muscle physiology and disease

 描述（由申请人提供）：细胞膜修复是正常生理学的一个重要方面，该过程的破坏可导致许多人类疾病（包括肌营养不良症）的病理生理学。我们以前确定MG 53作为细胞膜修复机制的重要组成部分。在上一个资助期间，我们发现MG 53中的关键半胱氨酸残基和亮氨酸拉链基序参与细胞膜修复的成核过程;非肌肉肌球蛋白IIa型（NM-IIa）作为分子马达将含有MG 53的囊泡运输到损伤部位; PTRF使MG 53修复机制锚定和靶向损伤膜。除了MG 53的细胞内作用之外，细胞膜损伤暴露了可以通过循环MG 53检测到的信号，允许重组人（rh）MG 53蛋白在细胞外空间中提供时修复膜损伤。为了开发MG 53作为治疗肌肉疾病的潜在治疗剂，我们已经建立了用于规模化生产rhMG 53的化学、生产和控制（CMC）工艺，以支持我们的临床前和未来临床研究。显然，如果不了解循环中MG 53控制的细胞过程和细胞外MG 53在组织保护中的机制作用，我们的翻译方法就无法进行。具体而言，a）循环MG 53如何识别组织损伤部位以促进针对肌肉损伤的保护并改善其在应激条件下的存活？B）控制MG 53在血液循环中的分泌、转运和清除的细胞过程是什么？c）循环MG 53的持续升高能否提供有益效果以改善肌营养不良的慢性过程？我们最近建立了一种转基因小鼠模型，其在循环中具有受控的MG 53分泌，该模型可用于检查MG 53在生理和病理条件下对肌肉损伤的保护功能。此次更新申请将重点测试“循环中的MG 53通过膜界定的信号通路保护肌肉损伤，控制MG 53的分泌，运输和血流清除可能为治疗退行性肌肉疾病提供替代方法”的假设。我们建议测试肌肉是分泌MG 53用于组织保护的旁分泌器官的概念，并且MG 53的肾脏介导的排泄是调节循环中MG 53水平的关键因素。我们的转基因小鼠模型允许对MG 53分泌进行定制控制，提供了检查循环MG 53在改善mdx小鼠中肌营养不良症病理学方面的功效以及评估持续MG 53在影响其他器官功能方面的安全性特征的方法。

 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.