The reserve pool of synaptic vesicles acts as a buffer for proteins involved in synaptic vesicle recycling
The reserve pool of synaptic vesicles acts as a buffer for proteins involved in synaptic vesicle recycling
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DOI：
10.1073/pnas.1112690108
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发表时间：
2011-10-11
影响因子：
11.1
通讯作者：
Rizzoli, Silvio O.
中科院分区：
文献类型：
--
作者：
Denker, Annette;Kroehnert, Katharina;Rizzoli, Silvio O.
突触前神经末梢包含数百个囊泡（例如在小的CNS突触中）和数万个囊泡（如在神经肌肉接头中）。虽然长期以来人们一直认为，在高需求条件下，需要如此大量的囊泡来维持神经传递，但我们发现，体内活动只需要回收百分之几的囊泡。然而，在许多进化上不同的物种中维持大量的储备囊泡表明它们与突触功能有关。我们在这里建议，这些囊泡构成缓冲液的可溶性辅助蛋白参与囊泡回收，防止其损失到轴突。支持这一假设，我们发现，囊泡集群包含大量的各种蛋白质所需的囊泡回收，但没有一个明显的功能内的集群。通过应用黑寡妇蜘蛛毒液破坏簇导致许多可溶性蛋白质扩散到轴突中。长时间的刺激和离子霉素的应用有类似的效果，这表明钙离子内流导致可溶性蛋白从囊泡的解结合。重申这一假设，我们发现，孤立的突触囊泡在体外隔离可溶性蛋白质从细胞质中的一个过程中，被抑制钙添加。我们的结论是，储备囊泡间接支持神经传递，确保可溶性回收蛋白质在突触活动期间按需传递。
Presynaptic nerve terminals contain between several hundred vesicles (for example in small CNS synapses) and several tens of thousands (as in neuromuscular junctions). Although it has long been assumed that such high numbers of vesicles are required to sustain neurotransmission during conditions of high demand, we found that activity in vivo requires the recycling of only a few percent of the vesicles. However, the maintenance of large amounts of reserve vesicles in many evolutionarily distinct species suggests that they are relevant for synaptic function. We suggest here that these vesicles constitute buffers for soluble accessory proteins involved in vesicle recycling, preventing their loss into the axon. Supporting this hypothesis, we found that vesicle clusters contain a large variety of proteins needed for vesicle recycling, but without an obvious function within the clusters. Disrupting the clusters by application of black widow spider venom resulted in the diffusion of numerous soluble proteins into the axons. Prolonged stimulation and ionomycin application had a similar effect, suggesting that calcium influx causes the unbinding of soluble proteins from vesicles. Confirming this hypothesis, we found that isolated synaptic vesicles in vitro sequestered soluble proteins from the cytosol in a process that was inhibited by calcium addition. We conclude that the reserve vesicles support neurotransmission indirectly, ensuring that soluble recycling proteins are delivered upon demand during synaptic activity.