Exocytotic catecholamine release is not associated with cation flux through channels in the vesicle membrane but Na+ influx through the fusion pore
Exocytotic catecholamine release is not associated with cation flux through channels in the vesicle membrane but Na+ influx through the fusion pore
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DOI：
10.1038/ncb1617
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发表时间：
2007-08-01
影响因子：
21.3
通讯作者：
Lindau, Manfred
中科院分区：
文献类型：
--
作者：
Gong, Liang-Wei;Alvarez de Toledo, Guillermo;Lindau, Manfred
带电荷的神经递质分子通过狭窄的融合孔释放需要其他离子的电荷补偿。有人提出，这可能是由于离子从细胞质中流过囊泡膜上的通道，从而产生向外的净电流。这一假设在染色质细胞中进行了验证，使用细胞贴附贴片电流法，同时测量单个囊泡释放的儿茶酚胺和通过贴片膜的离子电流。没有可检测到的电流与儿茶酚胺释放相关，表明小于2%的阳离子（如果有的话）通过其膜进入囊泡。相反，我们表明，当细胞外阳离子浓度降低时，通过融合孔的儿茶酚胺通量（以安培脚信号测量）会减少。结果表明，通过融合孔释放的递质速率与通过融合孔的净Na+流入相耦合，这与应用于融合孔渗透的电扩散理论预测的结果一致，并且表明泡状阳离子通道的作用是预融合而不是后融合。
Release of charged neurotransmitter molecules through a narrow fusion pore requires charge compensation by other ions. It has been proposed that this may occur by ion flow from the cytosol through channels in the vesicle membrane, which would generate a net outward current. This hypothesis was tested in chromaffin cells using cell-attached patch amperometry that simultaneously measured catecholamine release from single vesicles and ionic current across the patch membrane. No detectable current was associated with catecholamine release indicating that < 2% of cations, if any, enter the vesicle through its membrane. Instead, we show that flux of catecholamines through the fusion pore, measured as an amperometric foot signal, decreases when the extracellular cation concentration is reduced. The results reveal that the rate of transmitter release through the fusion pore is coupled to net Na+ influx through the fusion pore, as predicted by electrodiffusion theory applied to fusion-pore permeation, and suggest a prefusion rather than postfusion role for vesicular cation channels.