Neuroscience Institute, New York University Langone Medical Center, New York, NY.
J Cell Biol. 2020 Jun 1;219(6). doi: 10.1083/jcb.201906071.
Neurons are highly polarized cells organized into functionally and molecularly distinct domains. A key question is whether the multiprotein complexes that comprise these domains are preassembled, transported, and inserted as a complex or whether their components are transported independently and assemble locally. Here, we have dynamically imaged, in pairwise combinations, the vesicular transport of fluorescently tagged components of the nodes of Ranvier and other myelinated axonal domains in sensory neurons cultured alone or together with Schwann cells at the onset of myelination. In general, most proteins are transported independently in the anterograde direction. In contrast, there is substantial cotransport of proteins from distinct domains in the retrograde direction likely due to coendocytosis along the axon. Early myelination did not substantially change these patterns of transport, although it increased the overall numbers of axonal transport vesicles. Our results indicate domain components are transported in separate vesicles for local assembly, not as preformed complexes, and implicate endocytosis along axons as a mechanism of clearance.
神经元是高度极化的细胞，组织成具有不同功能和分子特征的域。一个关键问题是，构成这些域的多蛋白复合物是预先组装、运输和作为复合物插入的，还是它们的成分是独立运输并在局部组装的。在这里，我们在感觉神经元中动态地成对成像，这些神经元在髓鞘形成开始时单独培养或与施旺细胞一起培养，观察荧光标记的神经节结和其他有髓轴突域的囊泡运输。一般来说，大多数蛋白质在顺行方向上独立运输。相比之下，在逆行方向上，来自不同域的蛋白质有大量的共运输，这可能是由于沿着轴突的共内吞作用。早期髓鞘形成并没有显著改变这些运输模式，尽管它增加了轴突运输囊泡的总数。我们的结果表明，域成分是在单独的囊泡中运输进行局部组装的，而不是作为预先形成的复合物，并且暗示了沿着轴突的内吞作用是一种清除机制。
