T-tubule membrane remodeling in Drosophila myofiber function and models of myopathy

项目摘要 肌肉是高度专业化和组织化的细胞，为动物生命提供必不可少的收缩。一个 精细的、有功能的肌肉细胞组织的破坏是人类肌病疾病的基础。在……里面 具体地说，肌肉细胞膜分化成广泛的管状膜网络，称为 横(T)管是协调肌肉收缩力量的信号传递所必需的。T形小管 在某些人类骨骼肌病和心血管疾病中观察到组织紊乱或丢失，以及 有趣的是，相关突变基因编码的膜调节器与已知的野生型作用外 内吞或内体运输的肌肉。虽然有关于机制的猜测，但它仍然是 确定内分泌功能对T-小管维持的影响。相对较少的是 已知T管如何形成的分子遗传学基础，也不知道动力学或重塑机制 在完整的肌肉中对肌肉细胞的使用、损伤或老化做出反应。在果蝇中，我们发现了受调控的T管 在不同的拆卸-重组中涉及的特定保守基因功能的重塑和识别 野生型发育性肌纤维重塑计划的各个阶段。重要的是，特定的T小管 在中心性肌病中，两个人类基因的Fly同源基因的重塑作用指向 T小管动力学在疾病模型研究中的意义。飞翔系统提供了 活体、活体成像完整肌纤维中T管动力学的独特和关键优势 陈旧的发育时间框架与丰富的遗传工具相结合。以下结果来自 基因筛查，我们建立了一个新的理解T小管动力学的框架，其中包括一个中央 Dynamin Large GTPase活性在T小管解体和随后的膜进展中的作用 重塑所需的特定内体和自噬运输。利用我们创新的遗传、细胞和 分子方法在完整的苍蝇肌肉中，在这里我们将建立在我们的新发现的基础上来确定 动力蛋白介导的T小管囊泡分解的机制和调控，并建立 一条新的Rab35内体途径的鉴定及其与自噬的关系 从拆解到改建的过程。重要的是，我们将把我们对 成人飞行肌肉T管重塑的发育程序。我们将建立保护和 成人持续肌肉功能中T小管膜重组通路活动的后果 与了解人类肌肉疾病有关。

Project Summary Muscles are highly specialized and organized cells that provide contraction essential for animal life. A disruption of the elaborate, functional muscle cell organization underlies human myopathy diseases. In particular, differentiation of the muscle cell membrane into an extensive tubular membrane network called Transverse (T)-tubules is needed to enable signaling that coordinates power of muscle contraction. T-tubule disorganization or loss is observed in certain human skeletal myopathies and cardiovascular diseases, and interestingly, associated mutant genes encode for membrane regulators with known wildtype roles outside of muscle in endocytosis or endosomal trafficking. While there are speculations on mechanisms, it remains to be determined how implicated endocytic functions may contribute to T-tubule maintenance. Relatively little is known about the molecular-genetic basis for how T-tubules form nor the dynamics or remodeling mechanisms in intact muscle in response to muscle cell use, damage or aging. In flies, we uncovered regulated T-tubule remodeling and the identity of specific conserved gene functions involved at distinct disassembly-reassembly stages during a wildtype developmental myofiber remodeling program. Importantly, specific T-tubule remodeling roles for fly homologs of two human genes disrupted in centronuclear myopathy point to the significance of T-tubule dynamics and the ability to study in models of disease. The fly system affords the unique and key advantages of live, in vivo imaging of T-tubule dynamics in intact myofibers within a stereotypical developmental timeframe in combination with a wealth of genetic tools. Following results from genetic screens, we established a new framework understanding of T-tubule dynamics that includes a central role for dynamin large GTPase activity in T-tubule disassembly and subsequent membrane progression into specific endosomal and autophagy trafficking needed for remodeling. Using our innovative genetic, cellular and molecular approaches in intact fly muscles, here we will build on our novel findings to determine the mechanisms and regulation of dynamin-mediated T-tubule disassembly by vesiculation, and establish the identity of a proposed novel Rab35 endosomal pathway and the relationship to autophagy both needed for progression from disassembly to remodeling. Importantly, we will translate our understanding of a developmental program for T-tubule remodeling to adult flight muscle. We will establish conservation and consequences of a pathway activity for T-tubule membrane reorganization in ongoing adult muscle function, with relevance to understanding human muscle disease.