Presynaptic G-protein-coupled receptors dynamically modify vesicle fusion, synaptic cleft glutamate concentrations, and motor behavior.
Presynaptic G-protein-coupled receptors dynamically modify vesicle fusion, synaptic cleft glutamate concentrations, and motor behavior.
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DOI：
10.1523/jneurosci.1404-09.2009
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发表时间：
2009-08-19
期刊：
影响因子：
--
通讯作者：
Alford S
中科院分区：
文献类型：
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作者：
Gerachshenko T;Schwartz E;Bleckert A;Photowala H;Seymour A;Alford S
了解神经调节剂如何调节行为需要研究它们对功能神经系统的影响，以及它们潜在的细胞机制。利用广泛表征的七鳃鳗运动回路，以及启动这些行为的完整脊髓中网状脊髓突触前末梢的独特通道，我们研究了突触前 G 蛋白偶联受体对从系统水平到囊泡融合的分子控制的运动的影响。 5-HT 通过 Gβγ 与 SNARE 复合体相互作用来抑制神经递质释放，从而促进 Kiss-and-run 囊泡融合。在七鳃鳗脊髓中，我们证明，虽然突触前 5-HT 受体抑制网状脊髓指挥神经元诱发的神经递质释放，但它们的激活不会消除运动，而是调节运动节律。突触前 Gβγ 的释放会导致 AMPA 受体介导的突触反应受到显着抑制，但 NMDA 受体介导的神经传递成分基本保持完整。由于 Gβγ 与 SNARE 复合物的结合被 Ca2+-突触结合蛋白结合所取代，因此 5-HT 介导的抑制表现出 Ca2+ 敏感性。我们发现，随着 Ca2+ 在生理活动期间在突触前积聚，5-HT/Gβγ 介导的突触前抑制得到缓解，导致谷氨酸突触浓度呈频率依赖性增加。这种频率依赖性现象反映了囊泡融合模式的转变以及 AMPA 受体介导的 EPSC 从抑制中恢复，而无需 NMDA 受体 EPSC 的修饰。我们得出的结论是，突触前 5-HT GPCR 的激活状态依赖性地改变囊泡融合特性，从而改变兴奋性突触处 NMDA 与 AMPA 受体介导的反应的权重。因此，我们发现了一种新的机制，其中囊泡融合模式的修改可能会深刻地改变运动行为。
Understanding how neuromodulators regulate behavior requires investigating their effects on functional neural systems, but also their underlying cellular mechanisms. Utilizing extensively characterized lamprey motor circuits, and the unique access to reticulospinal presynaptic terminals in the intact spinal cord that initiate these behaviours, we have investigated effects of presynaptic G protein-coupled receptors on locomotion from the systems level, to the molecular control of vesicle fusion. 5-HT inhibits neurotransmitter release via a Gβγ interaction with the SNARE complex that promotes kiss-and-run vesicle fusion. In the lamprey spinal cord we demonstrate that while presynaptic 5-HT receptors inhibit evoked neurotransmitter release from reticulospinal command neurons, their activation does not abolish locomotion, but rather modulates locomotor rhythms. Liberation of presynaptic Gβγ causes substantial inhibition of AMPA receptor-mediated synaptic responses, but leaves NMDA receptor-mediated components of neurotransmission largely intact. Because Gβγ binding to the SNARE complex is displaced by Ca2+-synaptotagmin binding, 5-HT-mediated inhibition displays Ca2+ sensitivity. We show that as Ca2+ accumulates presynaptically during physiological bouts of activity, 5-HT/Gβγ-mediated presynaptic inhibition is relieved leading to a frequency-dependent increase in synaptic concentrations of glutamate. This frequency dependent phenomenon mirrors a shift in the vesicle fusion mode and a recovery of AMPA receptor-mediated EPSCs from inhibition without a modification of NMDA receptor EPSCs. We conclude that activation of presynaptic 5-HT GPCRs state-dependently alters vesicle fusion properties to shift the weight of NMDA vs AMPA receptor-mediated responses at excitatory synapses. We have therefore identified a novel mechanism in which modification of vesicle fusion modes may profoundly alter locomotor behaviour.