Körber Christoph, Kuner Thomas
Department of Functional Neuroanatomy, Institute of Anatomy and Cell Biology, Heidelberg University Heidelberg, Germany.
Front Synaptic Neurosci. 2016 Mar 2;8:5. doi: 10.3389/fnsyn.2016.00005. eCollection 2016.
The fusion of synaptic vesicles (SVs) with the plasma membrane of the active zone (AZ) upon arrival of an action potential (AP) at the presynaptic compartment is a tightly regulated probabilistic process crucial for information transfer. The probability of a SV to release its transmitter content in response to an AP, termed release probability (Pr), is highly diverse both at the level of entire synapses and individual SVs at a given synapse. Differences in Pr exist between different types of synapses, between synapses of the same type, synapses originating from the same axon and even between different SV subpopulations within the same presynaptic terminal. The Pr of SVs at the AZ is set by a complex interplay of different presynaptic properties including the availability of release-ready SVs, the location of the SVs relative to the voltage-gated calcium channels (VGCCs) at the AZ, the magnitude of calcium influx upon arrival of the AP, the buffering of calcium ions as well as the identity and sensitivity of the calcium sensor. These properties are not only interconnected, but can also be regulated dynamically to match the requirements of activity patterns mediated by the synapse. Here, we review recent advances in identifying molecules and molecular machines taking part in the determination of vesicular Pr at the AZ.
当动作电位（AP）到达突触前区室时，突触小泡（SVs）与活性区（AZ）的质膜融合是一个严格调控的概率性过程，对信息传递至关重要。一个SV响应AP释放其递质内容物的概率，称为释放概率（Pr），在整个突触水平以及给定突触处的单个SV水平上都高度不同。Pr在不同类型的突触之间、同一类型的突触之间、来自同一轴突的突触之间甚至同一突触前终末内不同的SV亚群之间都存在差异。AZ处SV的Pr由不同突触前特性的复杂相互作用决定，这些特性包括随时可释放的SV的可用性、SV相对于AZ处电压门控钙通道（VGCCs）的位置、AP到达时钙内流的大小、钙离子的缓冲以及钙传感器的特性和敏感性。这些特性不仅相互关联，还可以动态调节以匹配由突触介导的活动模式的需求。在这里，我们综述了在识别参与确定AZ处囊泡Pr的分子和分子机器方面的最新进展。
