Vanderbilt Brain Institute, Vanderbilt University, Nashville, TN 3729-7933, USA.
Vanderbilt Brain Institute, Vanderbilt University, Nashville, TN 3729-7933, USA; Department of Pharmacology, Vanderbilt University, Nashville, TN 37240-7933, USA.
Cell Rep. 2023 Oct 31;42(10):113201. doi: 10.1016/j.celrep.2023.113201. Epub 2023 Sep 30.
Calcium (Ca) signaling is tightly regulated within a presynaptic bouton. Here, we visualize Ca signals within hippocampal presynaptic boutons using GCaMP8s tagged to synaptobrevin, a synaptic vesicle protein. We identify evoked presynaptic Ca transients (ePreCTs) that derive from synchronized voltage-gated Ca channel openings, spontaneous presynaptic Ca transients (sPreCTs) that originate from ryanodine sensitive Ca stores, and a baseline Ca signal that arises from stochastic voltage-gated Ca channel openings. We find that baseline Ca, but not sPreCTs, contributes to spontaneous glutamate release. We employ photobleaching as a use-dependent tool to probe nano-organization of Ca signals and observe that all three occur in non-overlapping domains within the synapse at near-resting conditions. However, increased depolarization induces intermixing of these Ca domains via both local and non-local synaptic vesicle turnover. Our findings reveal nanosegregation of Ca signals within a presynaptic terminal that derive from multiple sources and in turn drive specific modes of neurotransmission.
钙信号在突触前末梢内受到严格调控。在这里，我们使用突触融合蛋白 synaptobrevin 标记的 GCaMP8s 来可视化海马体突触前末梢内的钙信号。我们鉴定了源自同步电压门控钙通道开放的诱发突触前钙瞬变 (ePreCTs)、源自ryanodine 敏感钙库的自发突触前钙瞬变 (sPreCTs)，以及源自随机电压门控钙通道开放的基线钙信号。我们发现基线钙，但不是 sPreCTs，有助于自发谷氨酸释放。我们利用光漂白作为一种使用依赖性工具来探测钙信号的纳米组织，并观察到在接近静止状态下，所有这三种钙信号都发生在突触内不重叠的区域。然而，增加去极化会通过局部和非局部突触囊泡周转来混合这些钙域。我们的发现揭示了源自多个来源的突触前末梢内钙信号的纳米分隔，并进而驱动特定的神经递质传递模式。
