Clem Jones Centre for Ageing Dementia Research, Queensland Brain Institute, The University of Queensland, Brisbane, Queensland 4072, Australia.
VIB Center for the Biology of Disease, 3000 Leuven, Belgium.
Nat Commun. 2017 Jan 3;8:13660. doi: 10.1038/ncomms13660.
Syntaxin1A is organized in nanoclusters that are critical for the docking and priming of secretory vesicles from neurosecretory cells. Whether and how these nanoclusters are affected by neurotransmitter release in nerve terminals from a living organism is unknown. Here we imaged photoconvertible syntaxin1A-mEos2 in the motor nerve terminal of Drosophila larvae by single-particle tracking photoactivation localization microscopy. Opto- and thermo-genetic neuronal stimulation increased syntaxin1A-mEos2 mobility, and reduced the size and molecular density of nanoclusters, suggesting an activity-dependent release of syntaxin1A from the confinement of nanoclusters. Syntaxin1A mobility was increased by mutating its polyphosphoinositide-binding site or preventing SNARE complex assembly via co-expression of tetanus toxin light chain. In contrast, syntaxin1A mobility was reduced by preventing SNARE complex disassembly. Our data demonstrate that polyphosphoinositide favours syntaxin1A trapping, and show that SNARE complex disassembly leads to syntaxin1A dissociation from nanoclusters. Lateral diffusion and trapping of syntaxin1A in nanoclusters therefore dynamically regulate neurotransmitter release.
突触融合蛋白 1A（Syntaxin1A）形成纳米簇，对于神经分泌细胞中分泌囊泡的停靠和引发至关重要。目前尚不清楚这些纳米簇是否以及如何受到来自活生物体的神经递质释放的影响。在这里，我们通过单颗粒跟踪光激活定位显微镜对果蝇幼虫运动神经末梢中的光转化型突触融合蛋白 1A-mEos2 进行了成像。光遗传和热敏遗传神经元刺激增加了突触融合蛋白 1A-mEos2 的流动性，并减小了纳米簇的大小和分子密度，这表明突触融合蛋白 1A 从纳米簇的限制中释放出来与活性有关。通过突变其多磷酸肌醇结合位点或通过共表达破伤风毒素轻链来阻止 SNARE 复合物组装，增加了突触融合蛋白 1A 的流动性。相比之下，通过阻止 SNARE 复合物的解体来降低突触融合蛋白 1A 的流动性。我们的数据表明多磷酸肌醇有利于突触融合蛋白 1A 的捕获，并表明 SNARE 复合物的解体导致突触融合蛋白 1A 从纳米簇中解离。因此，突触融合蛋白 1A 在纳米簇中的侧向扩散和捕获动态调节神经递质释放。
