Different roles of ribbon-associated and ribbon-free active zones in retinal bipolar cells
Different roles of ribbon-associated and ribbon-free active zones in retinal bipolar cells
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DOI：
10.1038/nn1963
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发表时间：
2007-10-01
影响因子：
25
通讯作者：
Tachibana, Masao
中科院分区：
文献类型：
--
作者：
Midorikawa, Mitsuharu;Tsukamoto, Yoshihiko;Tachibana, Masao
在感觉神经元的活动区可以看到带有突触囊泡晕的突触带，这些突触带紧张性地释放递质。因此，丝带被认为是持续胞吐的先决条件。通过应用全内反射荧光显微镜金鱼视网膜双极细胞终端，我们可视化Ca2+的入口网站，丝带，和囊泡融合事件。在这里，我们表明，主要的Ca2+进入网站位于带状，激活的Ca2+电流诱导立即和延迟囊泡融合事件在带状相关和带状免费的“热点”，分别。蛋白激酶C（PKC）的激活特异性地增强了无带位点的囊泡融合.电子显微镜显示，PKC激活选择性地增加了在无带位点停靠的囊泡的数量，这些囊泡面向具有突触后密度的神经元突起。视网膜双极细胞在其末端具有带状相关和无带状活动区，并且可能通过带状相关和无带状突触向突触后神经元发送功能不同的信号。
Synaptic ribbons with a halo of synaptic vesicles are seen at the active zones of sensory neurons that release transmitter tonically. Thus, ribbons are assumed to be a prerequisite for sustained exocytosis. By applying total internal reflection fluorescence microscopy to goldfish retinal bipolar cell terminals, we visualized Ca2+ entry sites, ribbons, and vesicle fusion events. Here we show that the main Ca2+ entry sites were located at ribbons, and that activation of the Ca2+ current induced immediate and delayed vesicle fusion events at ribbon- associated and ribbon-free 'hot spots', respectively. The activation of protein kinase C (PKC) specifically potentiated vesicle fusion at ribbon- free sites. Electron microscopy showed that PKC activation selectively increased the number of docked vesicles at ribbon- free sites, which faced neuronal processes with the postsynaptic density. Retinal bipolar cells have both ribbon- associated and ribbon- free active zones in their terminals and might send functionally distinct signals through ribbon-associated and ribbon-free synapses to postsynaptic neurons.