Active zone scaffolds differentially accumulate Unc13 isoforms to tune Ca2+ channel-vesicle coupling
Active zone scaffolds differentially accumulate Unc13 isoforms to tune Ca2+ channel-vesicle coupling
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DOI：
10.1038/nn.4364
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发表时间：
2016-10-01
影响因子：
25
通讯作者：
Sigrist, Stephan J.
中科院分区：
文献类型：
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作者：
Boehme, Mathias A.;Beis, Christina;Sigrist, Stephan J.
大脑的功能依赖于活动区(AZs)突触小泡(SV)的快速和精确的释放。SV释放的效果取决于从SV到钙离子通道的距离，但控制这一过程的分子机制尚不清楚。在这里，我们发现可以通过将两个UNC-13(UnC13)亚型靶向突触前AZ亚域来定义距离。对发育中的果蝇谷氨酸能突触的超分辨和活体成像显示，Unc13B亚型被支架蛋白Syd-1和Liprin-α招募到新生的AZ，而Unc13A被Bruchilot和Rim结合蛋白复合体定位在成熟的AZ。Unc13B定位在距钙通道120 nm处，而Unc13A定位在70 nm处，负责在此距离处对接SVS。Unc13A(空)突变体存在释放效率低、延迟和EGTA超敏感的问题。数学模型表明，突触通常通过两条独立的释放途径工作，这两条途径定位不同于任何一种异构体。我们发现了调控SV-Ca~(2+)-通道拓扑结构的Unc13-AZ异构体相互作用，其发育收紧优化了突触传递。
Brain function relies on fast and precisely timed synaptic vesicle (SV) release at active zones (AZs). Efficacy of SV release depends on distance from SV to Ca2+ channel, but molecular mechanisms controlling this are unknown. Here we found that distances can be defined by targeting two unc-13 (Unc13) isoforms to presynaptic AZ subdomains. Super-resolution and intravital imaging of developing Drosophila melanogaster glutamatergic synapses revealed that the Unc13B isoform was recruited to nascent AZs by the scaffolding proteins Syd-1 and Liprin-alpha, and Unc13A was positioned by Bruchpilot and Rim-binding protein complexes at maturing AZs. Unc13B localized 120 nm away from Ca2+ channels, whereas Unc13A localized only 70 nm away and was responsible for docking SVs at this distance. Unc13A(null) mutants suffered from inefficient, delayed and EGTA-supersensitive release. Mathematical modeling suggested that synapses normally operate via two independent release pathways differentially positioned by either isoform. We identified isoform-specific Unc13-AZ scaffold interactions regulating SV-Ca2+-channel topology whose developmental tightening optimizes synaptic transmission.