Assembly of SNARE core complexes prior to neurotransmitter release sets the readily releasable pool of synaptic vesicles.
Assembly of SNARE core complexes prior to neurotransmitter release sets the readily releasable pool of synaptic vesicles.
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DOI：
10.1074/jbc.c000237200
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发表时间：
2000-09
期刊：
影响因子：
--
通讯作者：
G. Lonart;T. Südhof
中科院分区：
文献类型：
--
作者：
G. Lonart;T. Südhof
神经递质释放的精确调节对于神经网络的正常功能至关重要，但所涉及的机制在很大程度上尚不清楚。使用灌流突触体，我们研究了突触囊泡的容易释放池，测量高渗蔗糖触发的释放量。我们发现，突触前代谢型谷氨酸受体的激活二羟苯甘氨酸和蛋白激酶C的刺激佛波酯增强谷氨酸的易释放池。尽管易于释放的库的分子性质尚不清楚，但一种可能性是，在其产生过程中，SNARE蛋白形成完整的核心复合物，并且核心复合物的形成发生在神经递质释放之前。为了测试这种可能性，我们采用了N-乙基马来酰亚胺（NEM），ATP酶N-乙基马来酰亚胺敏感因子的抑制剂，解离核心复合物，研究突触体中的核心复合物组装容易释放池的关系。NEM诱导的剂量依赖性增加的神经递质容易释放池，但本身并没有触发释放。核心复合物的直接测量证实，NEM引起的SNARE核心复合物在这些条件下的水平增加。我们的数据表明，在突触囊泡容易释放池，陷阱蛋白完全组装成核心复合物，和陷阱复合物组装是突触前调控的目标。
Precise regulation of neurotransmitter release is essential for the normal function of neural networks, but the mechanisms involved are largely unclear. Using superfused synaptosomes, we have studied the readily releasable pool of synaptic vesicles, measured as the amount of release triggered by hypertonic sucrose. We show that activation of presynaptic metabotropic glutamate receptors by dihydroxyphenylglycine and stimulation of protein kinase C by phorbol esters enhance the readily releasable pool of glutamate. Although the molecular nature of the readily releasable pool is unknown, one possibility is that during its generation, SNARE proteins form full core complexes, and that core complex formation occurs prior to neurotransmitter release. To test this possibility, we employed N-ethylmaleimide (NEM), an inhibitor of the ATPase N-ethylmaleimide-sensitive factor that dissociates core complexes, to study the relation of the readily releasable pool to core complex assembly in synaptosomes. NEM induced a dose-dependent increase in the readily releasable pool of neurotransmitters but by itself did not trigger release. Direct measurements of core complexes confirmed that NEM caused an increase in the levels of SNARE core complexes under these conditions. Our data suggest that in the readily releasable pool of synaptic vesicles, SNARE proteins are fully assembled into core complexes, and that SNARE complex assembly is a target of presynaptic regulation.