Laboratory of Molecular Neuroscience, German Center for Neurodegenerative Diseases (DZNE), 10117 Berlin, Germany.
Charité - Universitätsmedizin Berlin, Institute of Biochemistry, 10117 Berlin, Germany.
J Mol Biol. 2021 Jun 11;433(12):166961. doi: 10.1016/j.jmb.2021.166961. Epub 2021 Mar 25.
Neurotransmission relies on the tight spatial and temporal regulation of the synaptic vesicle (SV) cycle. Nerve terminals contain hundreds of SVs that form tight clusters. These clusters represent a distinct liquid phase in which one component of the phase are SVs and the other synapsin 1, a highly abundant synaptic protein. Another major family of disordered proteins at the presynapse includes synucleins, most notably α-synuclein. The precise physiological role of α-synuclein in synaptic physiology remains elusive, albeit its role has been implicated in nearly all steps of the SV cycle. To determine the effect of α-synuclein on the synapsin phase, we employ the reconstitution approach using natively purified SVs from rat brains and the heterologous cell system to generate synapsin condensates. We demonstrate that synapsin condensates recruit α-synuclein, and while enriched into these synapsin condensates, α-synuclein still maintains its high mobility. The presence of SVs enhances the rate of synapsin/α-synuclein condensation, suggesting that SVs act as catalyzers for the formation of synapsin condensates. Notably, at physiological salt and protein concentrations, α-synuclein alone is not able to cluster isolated SVs. Excess of α-synuclein disrupts the kinetics of synapsin/SV condensate formation, indicating that the molar ratio between synapsin and α-synuclein is important in assembling the functional condensates of SVs. Understanding the molecular mechanism of α-synuclein interactions at the nerve terminals is crucial for clarifying the pathogenesis of synucleinopathies, where α-synuclein, synaptic proteins and lipid organelles all accumulate as insoluble intracellular inclusions.
神经递质的传递依赖于突触囊泡 (SV) 循环的紧密时空调节。神经末梢含有数百个形成紧密簇的 SV。这些簇代表了一个独特的液相，其中一个组成部分是 SV，另一个是突触蛋白 1，一种高度丰富的突触蛋白。突触前另一个主要的无序蛋白家族包括突触核蛋白，最著名的是α-突触核蛋白。尽管其在 SV 循环的几乎所有步骤中都有作用，但α-突触核蛋白在突触生理学中的精确生理作用仍然难以捉摸。为了确定α-突触核蛋白对突触蛋白相的影响，我们采用了使用来自大鼠大脑的天然纯化 SV 进行重组的方法，以及异源细胞系统来产生突触蛋白凝聚物。我们证明突触蛋白凝聚物会募集α-突触核蛋白，而尽管α-突触核蛋白在这些突触蛋白凝聚物中富集，但它仍然保持高迁移率。SV 的存在会增加突触蛋白/α-突触核蛋白凝聚的速度，这表明 SV 作为形成突触蛋白凝聚物的催化剂。值得注意的是，在生理盐和蛋白质浓度下，单独的α-突触核蛋白不能使分离的 SV 聚类。过量的α-突触核蛋白会破坏突触蛋白/SV 凝聚物形成的动力学，这表明突触蛋白和α-突触核蛋白之间的摩尔比在组装 SV 的功能性凝聚物方面很重要。了解α-突触核蛋白在神经末梢的相互作用的分子机制对于阐明突触核蛋白病的发病机制至关重要，在突触核蛋白病中，α-突触核蛋白、突触蛋白和脂质细胞器都作为不溶性细胞内包涵体积累。
