Difference in trafficking of brain-derived neurotrophic factor between axons and dendrites of cortical neurons, revealed by live-cell imaging
Difference in trafficking of brain-derived neurotrophic factor between axons and dendrites of cortical neurons, revealed by live-cell imaging
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DOI：
10.1186/1471-2202-6-42
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发表时间：
2005-06-21
期刊：
影响因子：
2.4
通讯作者：
Tsumoto, T
中科院分区：
文献类型：
--
作者：
Adachi, N;Kohara, K;Tsumoto, T
背景：脑源性神经营养因子（Brain-derived neurotrophic factor， BDNF）被分类为神经元的一条受调控的分泌通路，被认为是通过突触前神经元的树突逆行作用或突触后神经元的轴突顺行作用。根据不同的情况，BDNF在树突和轴突中的运输模式和方向预计会有所不同。为了解决这个问题，我们通过延时成像分析了绿色荧光蛋白（GFP）标记的BDNF在活皮层神经元轴突和树突中的运动。在部分实验中，将青色荧光蛋白（CFP）标记的BDNF与黄色荧光蛋白（YFP）标记的神经生长因子（NGF）的表达进行比较，观察荧光蛋白标记的BDNF是否以这种神经营养素特异性的方式表达。结果：我们发现，在大约三分之二的注射质粒cdna的神经元中，标记有GFP或CFP的BDNF在树突和轴突中以点状方式表达，而在大约70%的注射质粒的神经元中，标记有GFP或YFP的NGF甚至在树突中弥漫表达。BDNF-GFP在轴突以囊状小点表达的神经元中，59%和23%的小点在顺行和逆行方向上快速运动。另一方面，树突中64%的BDNF-GFP点根本不动，或者在很短的距离内来回摆动。其余的树突点在两个方向上的移动相对平稳，但它们的平均移动速度为0.47 +/- 0.23 μ m/s，比轴突点的移动速度（0.73 +/- 0.26 μ m/s）慢。结论：荧光蛋白标记的BDNF在轴突和树突之间的运输模式和速度不同，提示轴突的顺行运输可能是BDNF向释放位点的主要流。
Background: Brain-derived neurotrophic factor ( BDNF), which is sorted into a regulated secretory pathway of neurons, is supposed to act retrogradely through dendrites on presynaptic neurons or anterogradely through axons on postsynaptic neurons. Depending on which is the case, the pattern and direction of trafficking of BDNF in dendrites and axons are expected to be different. To address this issue, we analyzed movements of green fluorescent protein (GFP)-tagged BDNF in axons and dendrites of living cortical neurons by time-lapse imaging. In part of the experiments, the expression of BDNF tagged with cyan fluorescent protein (CFP) was compared with that of nerve growth factor (NGF) tagged with yellow fluorescent protein (YFP), to see whether fluorescent protein-tagged BDNF is expressed in a manner specific to this neurotrophin.Results: We found that BDNF tagged with GFP or CFP was expressed in a punctated manner in dendrites and axons in about two-thirds of neurons into which plasmid cDNAs had been injected, while NGF tagged with GFP or YFP was diffusely expressed even in dendrites in about 70% of the plasmid-injected neurons. In neurons in which BDNF-GFP was expressed as vesicular puncta in axons, 59 and 23% of the puncta were moving rapidly in the anterograde and retrograde directions, respectively. On the other hand, 64% of BDNF-GFP puncta in dendrites did not move at all or fluttered back and forth within a short distance. The rest of the puncta in dendrites were moving relatively smoothly in either direction, but their mean velocity of transport, 0.47 +/- 0.23 ( SD) mu m/ s, was slower than that of the moving puncta in axons (0.73 +/- 0.26 mu m/s).Conclusion: The present results show that the pattern and velocity of the trafficking of fluorescence protein-tagged BDNF are different between axons and dendrites, and suggest that the anterograde transport in axons may be the dominant stream of BDNF to release sites.