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

项目摘要 肌肉是高度特化和组织化的细胞，提供动物生命所必需的收缩。一 精细的功能性肌细胞组织的破坏是人类肌病疾病的基础。在 特别是，肌细胞膜分化成广泛的管状膜网络，称为 需要横（T）小管来实现协调肌肉收缩功率的信号传导。T管 在某些人类骨骼肌病和心血管疾病中观察到组织解体或丢失， 有趣的是，相关的突变基因编码具有已知野生型作用的膜调节因子， 内吞作用或内体运输中的肌肉。虽然有关于机制的猜测，但仍有待于 确定了内吞功能如何影响T-小管的维持。之甚少 我们对T小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， 在完整的肌肉中响应于肌肉细胞使用、损伤或老化。在果蝇中，我们发现了受调节的T-小管， 重塑和特定的保守基因功能的身份参与不同的分解-重组 在野生型发育肌纤维重塑计划期间的阶段。重要的是，特异性T小管 在中枢性肌病中被破坏的两个人类基因的果蝇同源物的重塑作用指出， T-小管动力学的意义和在疾病模型中研究的能力。飞行系统提供了 独特的和关键的优势，活的，在体内成像的T-小管动力学在完整的肌纤维内， 刻板的发育时间表结合丰富的遗传工具。以下结果来自 基因筛选，我们建立了一个新的框架理解T-小管动力学，包括中央 发动蛋白大GT3活性在T-小管分解和随后的膜进展中的作用 重塑所需的特异性内体和自噬运输。利用我们创新的基因，细胞和 分子方法在完整的苍蝇肌肉，在这里，我们将建立在我们的新发现，以确定 机制和调节的动力蛋白介导的T-小管解体的泡，并建立 一个新的Rab 35内体通路的身份和自噬的关系都需要 从拆卸到改造。重要的是，我们将把我们对 发育计划的T-小管重塑成人飞行肌肉。我们将建立保护区， 在进行中的成人肌肉功能中T-小管膜重组的途径活性的结果， 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.