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

项目概要 肌肉是高度专业化和有组织的细胞，提供动物生命所必需的收缩功能。一个 复杂的、功能性的肌肉细胞组织的破坏是人类肌病疾病的基础。在 特别是，肌肉细胞膜分化为广泛的管状膜网络，称为 需要横向 (T) 管来发出协调肌肉收缩力量的信号。 T型小管 在某些人类骨骼肌病和心血管疾病中观察到组织紊乱或丧失，并且 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剂 肌肉内吞作用或内体运输。虽然有关于机制的猜测，但仍有待确定 确定了内吞功能如何有助于 T 管维持。相对较少的是 了解 T 管形成的分子遗传学基础以及动力学或重塑机制 完整肌肉中对肌肉细胞使用、损伤或衰老的反应。在果蝇中，我们发现了受调节的 T 管 参与不同拆卸-重组的特定保守基因功能的重塑和识别 野生型发育肌纤维重塑计划的各个阶段。重要的是，特定的 T 管 两个人类基因在中心核肌病中被破坏的果蝇同源物的重塑作用表明 T 管动力学的重要性和在疾病模型中研究的能力。飞行系统提供 对完整肌纤维中的 T 管动力学进行活体活体成像的独特且关键的优势 刻板的发育时间框架与丰富的遗传工具相结合。以下结果来自 遗传筛选，我们建立了 T 管动力学的新框架理解，其中包括一个中心 动力大 GTP 酶活性在 T 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转运。利用我们创新的遗传、细胞和 完整的果蝇肌肉中的分子方法，在这里我们将基于我们的新发现来确定 通过囊泡形成动力介导的 T 管解体的机制和调节，并建立 拟议的新型 Rab35 内体途径的身份及其与自噬的关系都是 从拆卸到改造的过程。重要的是，我们将把我们对 T 管重塑成成人飞行肌的发育计划。我们将建立保护和 T 管膜重组通路活动对持续成人肌肉功能的影响， 与了解人类肌肉疾病相关。

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.