VIB-VUB Center for Structural Biology, Brussels, Belgium.
Structural Biology Brussels, Vrije Universiteit Brussel, Brussels, Belgium.
Elife. 2020 Dec 22;9:e64922. doi: 10.7554/eLife.64922.
Synaptojanin1 (Synj1) is a phosphoinositide phosphatase, important in clathrin uncoating during endocytosis of presynaptic vesicles. It was identified as a potential drug target for Alzheimer's disease, Down syndrome, and TBC1D24-associated epilepsy, while also loss-of-function mutations in Synj1 are associated with epilepsy and Parkinson's disease. Despite its involvement in a range of disorders, structural, and detailed mechanistic information regarding the enzyme is lacking. Here, we report the crystal structure of the 5-phosphatase domain of Synj1. Moreover, we also present a structure of this domain bound to the substrate diC8-PI(3,4,5)P, providing the first image of a 5-phosphatase with a trapped substrate in its active site. Together with an analysis of the contribution of the different inositide phosphate groups to catalysis, these structures provide new insights in the Synj1 mechanism. Finally, we analysed the effect of three clinical missense mutations (Y793C, R800C, Y849C) on catalysis, unveiling the molecular mechanisms underlying Synj1-associated disease.
突触结合蛋白 1（Synj1）是一种磷酸肌醇磷酸酶，在突触小泡内吞作用中环化蛋白解聚过程中起重要作用。它被认为是阿尔茨海默病、唐氏综合征和 TBC1D24 相关癫痫的潜在药物靶点，而 Synj1 的功能丧失突变也与癫痫和帕金森病有关。尽管它与多种疾病有关，但该酶的结构和详细的机制信息仍缺乏。在这里，我们报告了 Synj1 的 5-磷酸酶结构域的晶体结构。此外，我们还展示了该结构域与底物二 C8-PI（3,4,5）P 结合的结构，这是首次在其活性位点中捕获到 5-磷酸酶与底物结合的图像。结合对不同肌醇磷酸盐基团对催化作用的分析，这些结构为 Synj1 的作用机制提供了新的见解。最后，我们分析了三种临床意义上的错义突变（Y793C、R800C、Y849C）对催化作用的影响，揭示了 Synj1 相关疾病的分子机制。
