Botulinum toxin A (BoNT/A) is a potent neurotoxin that acts primarily by silencing synaptic transmission by blocking neurotransmitter release. BoNT/A comprises a light chain (LC/A) intracellular protease and a heavy chain (HC/A) composed of a receptor binding domain (HCC/A) and a translocation domain (HCN/A) that mediates cell entry. Following entry into the neuron, the disulphide bond linking the two peptide chains is reduced to release the LC/A. To gain better insight into the trafficking and fate of BoNT/A before dissociation we have used a catalytically inactive, non-toxic full-length BoNT/A(0) mutant. Our data confirm that BoNT/A(0) enters cortical neurons both in an activity-dependent manner and via a pathway dependent on fibroblast growth factor receptor 3 (Fgfr3) signalling. We demonstrate that both dynamin-dependent endocytosis and lipid rafts are involved in BoNT/A internalisation and that full-length BoNT/A(0) traffics to early endosomes. Furthermore, while a proportion of BoNT/A remains stable in neurons for 3 days, BoNT/A degradation is primarily mediated by the proteasome. Finally, we demonstrate that a fraction of the endocytosed full-length BoNT/A(0) is capable of exiting the cell to intoxicate other neurons. Together, our data shed new light on the entry routes, trafficking and degradation of BoNT/A, and confirm that trafficking properties previously described for the isolated HCC/A receptor binding domain of are also applicable to the intact, full-length toxin.

中文翻译：

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培养大鼠神经元中完整全长 a 型肉毒杆菌神经毒素的内吞作用、运输和胞吐作用。


A 型肉毒杆菌毒素 (BoNT/A) 是一种强效神经毒素，主要通过阻断神经递质释放来抑制突触传递。 BoNT/A 包含轻链 (LC/A) 胞内蛋白酶和重链 (HC/A)，重链由受体结合​​结构域 (HCC/A) 和介导细胞进入的易位结构域 (HCN/A) 组成。进入神经元后，连接两条肽链的二硫键被还原以释放 LC/A。为了更好地了解解离前 BoNT/A 的运输和命运，我们使用了催化失活、无毒的全长 BoNT/A(0) 突变体。我们的数据证实，BoNT/A(0) 以活动依赖性方式和依赖成纤维细胞生长因子受体 3 (Fgfr3) 信号传导的途径进入皮质神经元。我们证明动力依赖性内吞作用和脂筏都参与 BoNT/A 内化，并且全长 BoNT/A(0) 运输到早期内体。此外，虽然一部分 BoNT/A 在神经元中保持稳定 3 天，但 BoNT/A 降解主要由蛋白酶体介导。最后，我们证明内吞的全长 BoNT/A(0) 的一部分能够离开细胞以毒害其他神经元。总之，我们的数据为 BoNT/A 的进入途径、运输和降解提供了新的线索，并证实先前描述的分离的 HCC/A 受体结合域的运输特性也适用于完整的全长毒素。