Rapsyn调控神经肌肉接头发育的分子机理及其在肌萎缩和肌纤维类型转换中的作用研究

Neuromuscular junction (NMJ)is a specialized chemical synapse that forms between motor axon terminals and skeletal muscle fibers.The development and maintenance of synaptic plasticity at the NMJ plays crucial roles in posture maintenance,muscle contraction,nutrition and metabolisms.Rapsyn is a pivotal scaffold protein for these processes.RING-H2 domain located at C-terminal of rapsyn interacts with β-dystroglycan, and mutations in this domain alter AChR cluster size and stability. Our previous work found that high-level autoubiquitination of rapsyn was detected, and it also interacts with E3 ligase CHIP.The interaction between rapsyn and CHIP was compromised with RING-H2 domain deletion.The function and signaling mechanisms of RING-H2 domain in vivo is still elusive so far.For this reason,in this proposal, we sought to use genetic strategy,"functional rescue"assay, to study the function and signaling mechanisms of RING-H2 domain underlying the development and maintenance of synaptic plasticity at the NMJ.With use of multiple muscle atrophy models,to explore effects of NMJ plasticity alteration on muscle atrophy and muscle fiber-type switching caused by RING-H2 domain deletion.Thus,this proposal will provide experimental evidences for deep understanding the molecular mechanism underlying regulation of NMJ development and its effects on the pathogenesis of muscle atrophy.

神经肌肉接头（NMJ）是运动神经末梢和骨骼肌纤维之间特化而成的化学突触，NMJ发育和突触可塑性维持对于姿势控制、肌肉收缩及营养代谢都至关重要。Rapsyn是参与NMJ发育和功能维持的一个关键"脚手架"蛋白，其C端的RING-H2结构域能够同β-dystroglycan相互作用，该结构域突变会影响到AChR聚集簇的形态和稳定性。我们的前期工作发现rapsyn存在高度泛素化修饰，并能同E3泛素连接酶CHIP结合；RING-H2结构域缺失可导致两者间相互作用降低，但目前该结构域的在体功能及信号转导机制仍不甚明了。为此，本研究拟采取遗传学功能"挽救"策略，研究RING-H2结构域在NMJ发育和突触可塑性中的功能及信号机制；结合多种肌萎缩模型，探讨RING-H2结构域缺陷导致的NMJ可塑性改变对肌萎缩和肌纤维类型转换的影响。从而，为深入理解NMJ发育的分子机理及其在肌萎缩进程中的作用提供实验依据。

神经肌肉接头（NMJ）是运动神经末梢和骨骼肌纤维之间特化而成的化学突触，NMJ发育和突触可塑性维持对于姿势控制、肌肉收缩及营养代谢都至关重要。Rapsyn是参与NMJ发育和功能维持的一个关键“脚手架”蛋白，其C端的RING-H2结构域能够同β-dystroglycan相互作用，该结构域突变会影响到AChR聚集簇的形态和稳定性。我们的前期工作发现rapsyn存在高度泛素化修饰，并能同E3泛素连接酶CHIP结合；RING-H2结构域缺失可导致两者间相互作用降低，但目前该结构域的在体功能及信号转导机制仍不甚明了。为此，本研究拟采取遗传学功能“挽救”策略，研究RING-H2结构域在NMJ发育和突触可塑性中的功能及信号机制；结合多种肌萎缩模型，探讨RING-H2结构域缺陷导致的NMJ可塑性改变对肌萎缩和肌纤维类型转换的影响。我们的研究结果表明：rapsyn蛋白的RING-H2结构域具有E3泛素连接酶活性，其主要通过Nedd8介导的Neddylation修饰催化AChRδ亚基并诱导AChR聚集簇形成，该研究为深入理解NMJ发育的分子机理及其在肌萎缩进程中的作用提供了重要实验依据。