Zeng Menglong, Ye Fei, Xu Jia, Zhang Mingjie
Division of Life Science, State Key Laboratory of Molecular Neuroscience, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China.
Division of Life Science, State Key Laboratory of Molecular Neuroscience, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China; Center of Systems Biology and Human Health, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China.
J Mol Biol. 2018 Jan 5;430(1):69-86. doi: 10.1016/j.jmb.2017.11.003. Epub 2017 Nov 11.
Discs large (DLG) MAGUKs are abundantly expressed in glutamatergic synapses, crucial for synaptic transmission, and plasticity by anchoring various postsynaptic components including glutamate receptors, downstream scaffold proteins and signaling enzymes. Different DLG members have shared structures and functions, but also contain unique features. How DLG family proteins function individually and cooperatively is largely unknown. Here, we report that PSD-95 PDZ3 directly couples with SH3-GK tandem in a PDZ ligand binding-dependent manner, and the coupling can promote PSD-95 dimerization and multimerization. Aided by sortase-mediated protein ligation and selectively labeling, we elucidated the PDZ3/SH3-GK conformational coupling mechanism using NMR spectroscopy. We further demonstrated that PSD-93, but not SAP102, can also undergo PDZ3 ligand binding-induced conformational coupling with SH3-GK and form homo-oligomers. Interestingly, PSD-95 and PSD-93 can also form ligand binding-induced hetero-oligomers, suggesting a cooperative assembly mechanism for the mega-N-methyl-d-aspartate receptor synaptic signaling complex. Finally, we provide evidence showing that ligand binding-induced conformational coupling between PDZ and SH3-GK is a common feature for other MAGUKs including CASK and PALS1.
盘状大蛋白（DLG）家族的膜相关鸟苷酸激酶（MAGUKs）在谷氨酸能突触中大量表达，通过锚定包括谷氨酸受体、下游支架蛋白和信号酶在内的各种突触后成分，对突触传递和可塑性至关重要。不同的DLG成员具有共同的结构和功能，但也包含独特的特征。DLG家族蛋白如何单独发挥作用以及协同作用在很大程度上尚不清楚。在这里，我们报告PSD-95的PDZ3结构域以依赖于PDZ配体结合的方式直接与SH3-GK串联结构偶联，并且这种偶联可以促进PSD-95的二聚化和多聚化。借助分选酶介导的蛋白质连接和选择性标记，我们使用核磁共振光谱阐明了PDZ3/SH3-GK的构象偶联机制。我们进一步证明，PSD-93而非SAP102也可以通过PDZ3配体结合诱导与SH3-GK发生构象偶联并形成同源寡聚体。有趣的是，PSD-95和PSD-93也可以形成配体结合诱导的异源寡聚体，这表明巨型N-甲基-D-天冬氨酸受体突触信号复合物存在协同组装机制。最后，我们提供的证据表明，PDZ和SH3-GK之间的配体结合诱导的构象偶联是包括CASK和PALS1在内的其他MAGUKs的共同特征。
