Synaptotagmin2 (Syt2) Drives Fast Release Redundantly with Syt1 at the Output Synapses of Parvalbumin-Expressing Inhibitory Neurons
Synaptotagmin2 (Syt2) Drives Fast Release Redundantly with Syt1 at the Output Synapses of Parvalbumin-Expressing Inhibitory Neurons
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DOI：
10.1523/jneurosci.3736-16.2017
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发表时间：
2017-04-26
影响因子：
5.3
通讯作者：
Schneggenburger, Ralf
中科院分区：
文献类型：
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作者：
Bouhours, Brice;Gjoni, Enida;Schneggenburger, Ralf
哺乳动物中枢神经系统中表达小蛋白的抑制性神经元专门用于在其输出突触上快速释放递质。然而，Ca2+传感器被确定的抑制性突触使用，包括小蛋白表达抑制性神经元的输出突触，直到最近才开始被解决。在这里，我们研究了Syt1和Syt2在哺乳动物中枢神经系统中两种类型的快速释放抑制连接中的作用：梯形体内侧核与外侧上橄榄甘氨酸能突触和小脑篮状/星状细胞-浦肯野gaba能突触。我们使用条件敲除和常规敲除（KO）小鼠系，在体内产生Syt1-Syt2双KO突触，这些小鼠系具有病毒表达的cree -重组酶和光激活离子通道，用于对转导纤维进行光刺激。令人惊讶的是，我们发现，尽管免疫组织化学显示Syt2蛋白明显存在于抑制性神经末梢，但单独的Syt2蛋白对诱发的递质释放只有轻微的影响。我们发现Syt1在这些抑制性突触中弱共表达，并且必须与Syt2一起基因失活才能实现快速释放的显着减少和不同步。因此，我们的工作在快速释放的抑制性突触中确定了功能相关的Ca2+传感器，并表明两种主要的Syt亚型可以在给定的突触连接中协同介导释放。
Parvalbumin-expressing inhibitory neurons in the mammalian CNS are specialized for fast transmitter release at their output synapses. However, the Ca2+ sensor(s) used by identified inhibitory synapses, including the output synapses of parvalbumin-expressing inhibitory neurons, have only recently started to be addressed. Here, we investigated the roles of Syt1 and Syt2 at two types of fast-releasing inhibitory connections in the mammalian CNS: the medial nucleus of the trapezoid body to lateral superior olive glycinergic synapse, and the basket/stellate cell-Purkinje GABAergic synapse in the cerebellum. We used conditional and conventional knock-out (KO) mouse lines, with viral expression of Cre-recombinase and a light-activated ion channel for optical stimulation of the transduced fibers, to produce Syt1-Syt2 double KO synapses in vivo. Surprisingly, we found that KO of Syt2 alone had only minor effects on evoked transmitter release, despite the clear presence of the protein in inhibitory nerve terminals revealed by immunohistochemistry. We show that Syt1 is weakly coexpressed at these inhibitory synapses and must be genetically inactivated together with Syt2 to achieve a significant reduction and desynchronization of fast release. Thus, our work identifies the functionally relevant Ca2+ sensor(s) at fast-releasing inhibitory synapses and shows that two major Syt isoforms can cooperate to mediate release at a given synaptic connection.