Molecular and Theoretical Neuroscience, Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), Berlin, Germany; Einstein Center for Neurosciences Berlin, Charité Universitätsmedizin Berlin, Berlin, Germany.
Department of Neuroscience, University of Copenhagen, Copenhagen, Denmark.
Cell Rep. 2023 Jun 27;42(6):112541. doi: 10.1016/j.celrep.2023.112541. Epub 2023 May 26.
Presynaptic plasticity adjusts neurotransmitter (NT) liberation. Short-term facilitation (STF) tunes synapses to millisecond repetitive activation, while presynaptic homeostatic potentiation (PHP) of NT release stabilizes transmission over minutes. Despite different timescales of STF and PHP, our analysis of Drosophila neuromuscular junctions reveals functional overlap and shared molecular dependence on the release-site protein Unc13A. Mutating Unc13A's calmodulin binding domain (CaM-domain) increases baseline transmission while blocking STF and PHP. Mathematical modeling suggests that Ca/calmodulin/Unc13A interaction plastically stabilizes vesicle priming at release sites and that CaM-domain mutation causes constitutive stabilization, thereby blocking plasticity. Labeling the functionally essential Unc13A MUN domain reveals higher STED microscopy signals closer to release sites following CaM-domain mutation. Acute phorbol ester treatment similarly enhances NT release and blocks STF/PHP in synapses expressing wild-type Unc13A, while CaM-domain mutation occludes this, indicating common downstream effects. Thus, Unc13A regulatory domains integrate signals across timescales to switch release-site participation for synaptic plasticity.
突触前可塑性调节神经递质（NT）释放。短期易化（STF）使突触适应毫秒级重复激活，而 NT 释放的突触前稳态增强（PHP）则在数分钟内稳定传输。尽管 STF 和 PHP 的时间尺度不同，但我们对果蝇肌神经接头的分析揭示了功能上的重叠和对释放位点蛋白 Unc13A 的共同分子依赖性。突变 Unc13A 的钙调蛋白结合域（CaM 域）会增加基线传输，同时阻断 STF 和 PHP。数学模型表明，Ca/钙调蛋白/Unc13A 相互作用可使囊泡在释放位点的引发状态发生塑性稳定，而 CaM 域突变导致组成性稳定，从而阻断可塑性。标记功能上必需的 Unc13A MUN 结构域显示，在 CaM 结构域突变后，靠近释放位点的 STED 显微镜信号更高。急性佛波酯处理同样增强了 NT 释放，并阻断了表达野生型 Unc13A 的突触中的 STF/PHP，而 CaM 结构域突变则阻止了这种情况，表明存在共同的下游效应。因此，Unc13A 的调节结构域整合了跨越时间尺度的信号，以切换释放位点参与突触可塑性。
