Deerinck T J, Levinson S R, Bennett G V, Ellisman M H
National Center for Microscopy and Imaging Research at San Diego and the Department of Neurosciences, University of California San Diego, La Jolla, California 92093-0608, USA.
J Neurosci. 1997 Jul 1;17(13):5080-8. doi: 10.1523/JNEUROSCI.17-13-05080.1997.
The distribution of voltage-sensitive sodium channels on axons in the dorsal and ventral spinal roots of the dystrophic mouse 129/ReJ-Lama2dy was determined via immunocytochemistry. In these nerves there are regions in which Schwann cells fail to proliferate and myelinate axons in a normal manner, leaving bundles of closely packed large-diameter amyelinated axons. We have identified discrete and focal concentrations of sodium channel immunoreactivity on these axons by both confocal immunofluorescence and immunoelectron microscopy, using a peptide-derived polyclonal antibody. In addition, simultaneous labeling with an antibody recognizing neuronal-specific ankyrinG revealed a distinct colocalization with the sodium channels on both normal and amyelinated axons. The presence of patches of sodium channels along with their anchoring protein on amyelinated axons in the absence of intervening Schwann cells demonstrates that axons can form and maintain independently these initial aggregations. This confirms that direct contact between Schwann cell and axon is not required for the formation of sodium channel patches of nodal dimensions and density. Furthermore, this strongly suggests that local transfer of sodium channels from Schwann cells to axons is not required for this process.
通过免疫细胞化学方法确定了营养不良小鼠129/ReJ-Lama2dy背侧和腹侧脊髓神经根轴突上电压敏感钠通道的分布。在这些神经中，存在一些区域，雪旺细胞无法正常增殖并髓鞘化轴突，从而留下紧密排列的大直径无髓鞘轴突束。我们使用肽衍生的多克隆抗体，通过共聚焦免疫荧光和免疫电子显微镜，在这些轴突上鉴定出钠通道免疫反应性的离散和局灶性聚集。此外，用识别神经元特异性锚蛋白G的抗体进行同步标记，显示在正常和无髓鞘轴突上，它与钠通道有明显的共定位。在没有中间雪旺细胞的情况下，无髓鞘轴突上存在钠通道斑块及其锚定蛋白，这表明轴突可以独立形成并维持这些初始聚集。这证实了形成节点尺寸和密度的钠通道斑块不需要雪旺细胞与轴突之间的直接接触。此外，这强烈表明该过程不需要钠通道从雪旺细胞向轴突的局部转移。
