G protein betagamma-subunits activated by serotonin mediate presynaptic inhibition by regulating vesicle fusion properties.
G protein betagamma-subunits activated by serotonin mediate presynaptic inhibition by regulating vesicle fusion properties.
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血清素激活的 G 蛋白 β-亚基通过调节囊泡融合特性介导突触前抑制。
DOI：
10.1073/pnas.0600509103
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发表时间：
2006
影响因子：
11.1
通讯作者：
Alford,Simon
中科院分区：
文献类型：
--
作者：
Photowala,Huzefa;Blackmer,Trillium;Schwartz,Eric;Hamm,HeidiE;Alford,Simon
神经递质被认为以量子的形式释放，突触小泡通过与质膜融合将神经递质包传递到突触裂隙。然而，突触小泡可能发生不完全融合。我们提供了G蛋白偶联受体通过导致这种不完全融合而抑制释放的证据。5-羟色胺(5-HT)受体信号通过直接作用于囊泡融合机制，有效地抑制七翼动物网状脊髓轴突及其突触后靶点之间的兴奋性突触后电流(EPSCs)。我们发现，5-羟色胺受体介导的突触前抑制，在这个突触，涉及EPSC量子大小的减小。通过比较5-羟色胺应用前后成对EPSC的单位量子幅度直接测量量子大小，通过确定5-羟色胺对平均诱发EPSC幅度与方差之间关系的影响间接测量量子大小。FM染料标记实验的结果表明，5-羟色胺阻止囊泡的充分融合。5-羟色胺减少小泡的FM1-43染色，其效果与其对EPSC的作用相似。然而，FM1-43标记的囊泡的脱色被较低浓度的5-羟色胺所消除，从而留下大量的EPSC。在5-羟色胺刺激过程中，细胞外间隙使用水溶性膜猝灭剂可减少FM1-43的荧光。因此，在5-羟色胺抑制突触传递的过程中，囊泡与细胞外间隙接触。我们的结论是，5-羟色胺通过游离G-βγ阻止突触小泡塌陷进入突触前膜。
Neurotransmitters are thought to be released as quanta, where synaptic vesicles deliver packets of neurotransmitter to the synaptic cleft by fusion with the plasma membrane. However, synaptic vesicles may undergo incomplete fusion. We provide evidence that G protein-coupled receptors inhibit release by causing such incomplete fusion. 5-hydroxytryptamine (5-HT) receptor signaling potently inhibits excitatory postsynaptic currents (EPSCs) between lamprey reticulospinal axons and their postsynaptic targets by a direct action on the vesicle fusion machinery. We show that 5-HT receptor-mediated presynaptic inhibition, at this synapse, involves a reduction in EPSC quantal size. Quantal size was measured directly by comparing unitary quantal amplitudes of paired EPSCs before and during 5-HT application and indirectly by determining the effect of 5-HT on the relationship between mean-evoked EPSC amplitude and variance. Results from FM dye-labeling experiments indicate that 5-HT prevents full fusion of vesicles. 5-HT reduces FM1-43 staining of vesicles with a similar efficacy to its effect on the EPSC. However, destaining of FM1-43-labeled vesicles is abolished by lower concentrations of 5-HT that leave a substantial EPSC. The use of a water-soluble membrane impermeant quenching agent in the extracellular space reduced FM1-43 fluorescence during stimulation in 5-HT. Thus vesicles contact the extracellular space during inhibition of synaptic transmission by 5-HT. We conclude that 5-HT, via free Gβγ, prevents the collapse of synaptic vesicles into the presynaptic membrane.