School of Biomedical Sciences, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China.
School of Biological Sciences, Faculty of Science, The University of Hong Kong, Hong Kong, China.
Sci Adv. 2023 Jun 16;9(24):eadg0183. doi: 10.1126/sciadv.adg0183.
Junctional folds are unique membrane specializations developed progressively during the postnatal maturation of vertebrate neuromuscular junctions (NMJs), but how they are formed remains elusive. Previous studies suggested that topologically complex acetylcholine receptor (AChR) clusters in muscle cultures undergo a series of transformations, resembling the postnatal maturation of NMJs in vivo. We first demonstrated the presence of membrane infoldings at AChR clusters in cultured muscles. Live-cell super-resolution imaging further revealed that AChRs are gradually redistributed to the crest regions and spatially segregated from acetylcholinesterase along the elongating membrane infoldings over time. Mechanistically, lipid raft disruption or caveolin-3 knockdown not only inhibits membrane infolding formation at aneural AChR clusters and delays agrin-induced AChR clustering in vitro but also affects junctional fold development at NMJs in vivo. Collectively, this study demonstrated the progressive development of membrane infoldings via nerve-independent, caveolin-3-dependent mechanisms and identified their roles in AChR trafficking and redistribution during the structural maturation of NMJs.
连接褶皱是脊椎动物神经肌肉接头（NMJ）在出生后成熟过程中逐渐形成的独特膜特化结构，但它们是如何形成的仍然难以捉摸。先前的研究表明，在肌肉培养物中拓扑结构复杂的乙酰胆碱受体（AChR）簇经历了一系列的转化，类似于体内 NMJ 的出生后成熟。我们首先证明了在培养的肌肉中的 AChR 簇存在膜内折。活细胞超分辨率成像进一步显示，随着时间的推移，AChR 逐渐重新分布到嵴区域，并沿延长的膜内折与乙酰胆碱酯酶在空间上分离。从机制上讲，脂质筏破坏或窖蛋白-3 敲低不仅抑制无神经 AChR 簇的膜内折形成，并延迟体外诱导的 AChR 聚集，而且还影响体内 NMJ 连接褶皱的发育。总之，这项研究表明，通过与神经无关、窖蛋白-3 依赖的机制，膜内折的逐渐发育，并确定了它们在 NMJ 结构成熟过程中 AChR 运输和再分布中的作用。
