Imam Nasir, Choudhury Susobhan, Heinze Katrin G, Schindelin Hermann
Institute of Structural Biology, Rudolf Virchow Center for Integrative and Translational Bioimaging, University of Würzburg, Würzburg, Germany.
Molecular Microscopy, Rudolf Virchow Center for Integrative and Translational Bioimaging, University of Würzburg, Würzburg, Germany.
Front Synaptic Neurosci. 2022 Aug 4;14:959875. doi: 10.3389/fnsyn.2022.959875. eCollection 2022.
Interneuronal synaptic transmission relies on the proper spatial organization of presynaptic neurotransmitter release and its reception on the postsynaptic side by cognate neurotransmitter receptors. Neurotransmitter receptors are incorporated into and arranged within the plasma membrane with the assistance of scaffolding and adaptor proteins. At inhibitory GABAergic postsynapses, collybistin, a neuronal adaptor protein, recruits the scaffolding protein gephyrin and interacts with various neuronal factors including cell adhesion proteins of the neuroligin family, the GABA receptor α2-subunit and the closely related small GTPases Cdc42 and TC10 (RhoQ). Most collybistin splice variants harbor an N-terminal SH3 domain and exist in an autoinhibited/closed state. Cdc42 and TC10, despite sharing 67.4% amino acid sequence identity, interact differently with collybistin. Here, we delineate the molecular basis of the collybistin conformational activation induced by TC10 with the aid of recently developed collybistin FRET sensors. Time-resolved fluorescence-based FRET measurements reveal that TC10 binds to closed/inactive collybistin leading to relief of its autoinhibition, contrary to Cdc42, which only interacts with collybistin when forced into an open state by the introduction of mutations destabilizing the closed state of collybistin. Taken together, our data describe a TC10-driven signaling mechanism in which collybistin switches from its autoinhibited closed state to an open/active state.
神经元间的突触传递依赖于突触前神经递质释放的适当空间组织及其在突触后通过同源神经递质受体的接收。神经递质受体在支架蛋白和衔接蛋白的协助下整合到质膜中并在质膜内排列。在抑制性GABA能突触后，神经元衔接蛋白collybistin招募支架蛋白gephyrin，并与各种神经元因子相互作用，包括神经连接蛋白家族的细胞粘附蛋白、GABA受体α2亚基以及密切相关的小GTP酶Cdc42和TC10（RhoQ）。大多数collybistin剪接变体含有一个N端SH3结构域，并以自抑制/封闭状态存在。Cdc42和TC10尽管氨基酸序列同一性为67.4%，但与collybistin的相互作用不同。在这里，我们借助最近开发的collybistin FRET传感器，描绘了由TC10诱导的collybistin构象激活的分子基础。基于时间分辨荧光的FRET测量结果表明，与Cdc42相反，TC10与封闭/无活性的collybistin结合，导致其自抑制解除，Cdc42只有在通过引入使collybistin封闭状态不稳定的突变而被迫进入开放状态时才与collybistin相互作用。综上所述，我们的数据描述了一种由TC10驱动的信号传导机制，其中collybistin从其自抑制的封闭状态转变为开放/活性状态。
