Calcium dependence of neurotransmitter release at a high fidelity synapse.
Calcium dependence of neurotransmitter release at a high fidelity synapse.
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高保真突触神经递质释放的钙依赖性。
DOI：
10.7554/elife.70408
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发表时间：
2021-10-06
期刊：
影响因子：
7.7
通讯作者：
Hallermann S
中科院分区：
文献类型：
--
作者：
Eshra A;Schmidt H;Eilers J;Hallermann S
突触囊泡的启动、融合和补充的Ca 2+依赖性是控制神经递质释放和突触可塑性的基本参数。尽管付出了巨大的努力，但由于解开囊泡引发、融合和补充的技术挑战，突触囊泡周期中的这些重要步骤仍然知之甚少。在这里，我们研究了这些步骤的钙敏感性苔藓纤维突触在啮齿类动物小脑，其特征在于快速囊泡补充介导的高频信号。我们发现，基础游离Ca2+浓度（<200 nM）严格控制动作电位诱发的释放，表明囊泡引发的高亲和力Ca2+传感器。Ca2+释放实验揭示了释放速率和细胞内Ca2+浓度之间令人惊讶的浅和非饱和关系，高达50 μM。在持续升高的细胞内Ca 2+浓度的囊泡补充率表现出很小的Ca 2+依赖性。最后，定量机械释放计划与五个钙离子结合的步骤，通过并行或顺序囊泡池纳入快速囊泡补充可以解释我们的数据。因此，我们表明，共存的高亲和力和低亲和力的Ca2+传感器介导的启动，融合，并在高保真突触的突触囊泡的补充。
The Ca2+-dependence of the priming, fusion, and replenishment of synaptic vesicles are fundamental parameters controlling neurotransmitter release and synaptic plasticity. Despite intense efforts, these important steps in the synaptic vesicles’ cycle remain poorly understood due to the technical challenge in disentangling vesicle priming, fusion, and replenishment. Here, we investigated the Ca2+-sensitivity of these steps at mossy fiber synapses in the rodent cerebellum, which are characterized by fast vesicle replenishment mediating high-frequency signaling. We found that the basal free Ca2+ concentration (<200 nM) critically controls action potential-evoked release, indicating a high-affinity Ca2+ sensor for vesicle priming. Ca2+ uncaging experiments revealed a surprisingly shallow and non-saturating relationship between release rate and intracellular Ca2+ concentration up to 50 μM. The rate of vesicle replenishment during sustained elevated intracellular Ca2+ concentration exhibited little Ca2+-dependence. Finally, quantitative mechanistic release schemes with five Ca2+ binding steps incorporating rapid vesicle replenishment via parallel or sequential vesicle pools could explain our data. We thus show that co-existing high- and low-affinity Ca2+ sensors mediate priming, fusion, and replenishment of synaptic vesicles at a high-fidelity synapse.