Neurofilaments are transported rapidly but intermittently in axons: Implications for slow axonal transport
Neurofilaments are transported rapidly but intermittently in axons: Implications for slow axonal transport
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DOI：
10.1523/jneurosci.20-18-06849.2000
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发表时间：
2000-09-15
影响因子：
5.3
通讯作者：
Black, MM
中科院分区：
文献类型：
--
作者：
Roy, S;Coffee, P;Black, MM
缓慢轴突运输将细胞骨架蛋白从细胞体传递到轴突尖端。这种运输为轴突提供了产生和保持其细长形状所需的结构元素，也在轴突内产生了轴突生长和导航所必需的力。轴突细胞骨架运输的机制尚不清楚。一种假说认为，细胞骨架蛋白以聚合物的形式在轴突内运输。我们通过观察活轴突中的单个细胞骨架聚合物并确定它们是否经历矢量运动来验证这一假设。我们将重点放在培养的交感神经元轴突中的神经丝上，因为这些轴突中的单个神经丝可以通过光学显微镜看到。用含有绿色荧光蛋白（GFP）与重神经丝蛋白亚基（NFH）融合蛋白编码结构的重组腺病毒感染培养的交感神经元。嵌合GFP-NFH与内源性神经丝共组装。延时成像显示，单个gfp - nfh标记的神经丝在轴突中沿顺行和逆行方向进行强烈的矢量运输，但具有强烈的顺行偏倚。两个方向的NF输运表现出较宽的速率谱，平均约为0.6-0.7 mm/秒。然而，运动是间歇性的，单个神经丝在轴突内运输时暂停。一些NFs在观察它们的大部分时间里要么移动要么暂停，而另一些则处于中间状态。平均而言，神经丝最多有20%的时间在运动，其余时间则处于静止状态。这些结果证实了慢轴突运输机制传递神经丝。
Slow axonal transport conveys cytoskeletal proteins from cell body to axon tip. This transport provides the axon with the architectural elements that are required to generate and maintain its elongate shape and also generates forces within the axon that are necessary for axon growth and navigation. The mechanisms of cytoskeletal transport in axons are unknown. One hypothesis states that cytoskeletal proteins are transported within the axon as polymers. We tested this hypothesis by visualizing individual cytoskeletal polymers in living axons and determining whether they undergo vectorial movement. We focused on neurofilaments in axons of cultured sympathetic neurons because individual neurofilaments in these axons can be visualized by optical microscopy. Cultured sympathetic neurons were infected with recombinant adenovirus containing a construct encoding a fusion protein combining green fluorescent protein (GFP) with the heavy neurofilament protein subunit (NFH). The chimeric GFP-NFH coassembled with endogenous neurofilaments. Time lapse imaging revealed that individual GFP-NFH-labeled neurofilaments undergo vigorous vectorial transport in the axon in both anterograde and retrograde directions but with a strong anterograde bias. NF transport in both directions exhibited a broad spectrum of rates with averages of approximate to 0.6-0.7 mm/sec. However, movement was intermittent, with individual neurofilaments pausing during their transit within the axon. Some NFs either moved or paused for the most of the time they were observed, whereas others were intermediate in behavior. On average, neurofilaments spend at most 20% of the time moving and rest of the time paused. These results establish that the slow axonal transport machinery conveys neurofilaments.