A Degenerin Cation Channel Drives Activity-Dependent Remodeling of GABA Synapses

描述（由申请人提供）：神经回路在发育过程中被广泛完善，因为突触被创建或破坏以修改大脑功能。已知神经活动调节这些重塑事件，但驱动突触重组的分子机制知之甚少。这项研究测试的假设，DEG/ENaC家族的阳离子通道的成员作为神经活动和突触稳定性之间的分子联系的功能。这项工作利用了线虫C.在线虫中，GABA神经元的DD类的腹侧突触在幼虫发育期间重新定位到与背肌的新连接。这种突触重塑程序被VD运动神经元中的ESTA-55/COUP TF转录因子阻断，所述VD运动神经元通常与腹侧肌肉突触。米勒实验室在细胞特异性分析策略中利用了这种β-55功能，以确定19个在突触重塑中起作用的保守基因。我的工作现在已经表明，这些β-55的目标之一，变性蛋白/上皮钠通道（DEG/ENaC），β-8，促进突触重塑的机制，是由GABA能信号激活。这一发现很重要，因为DEG/ENaC蛋白与学习和记忆有关，但将DEG/ENaC功能与突触可塑性联系起来的分子途径在很大程度上是未知的。具体目标1测试GABA神经元活动在细胞自主机制中驱动重塑过程的预测。特异性目的2测试了以下关键假设：GABA-8定位于GABA神经元的突触前区域，并在这些细胞中发挥作用以促进重塑。特定目标3测试了新的预测，即GABA-8被伴随GABA释放的细胞外钙的瞬时消耗激活，并且这种效应触发突触前装置的解体。的结果 这项研究将提供一个更好的理解细胞机制，连接电路活动的动态事件在突触。此外，这项研究可能提供的见解，揭示了精神障碍的生物学基础，从功能失调的突触连接。

DESCRIPTION (provided by applicant): Neural circuits are extensively refined during development as synapses are either created or destroyed to modify brain function. Neural activity is known to regulate these remodeling events but the molecular mechanisms that drive synaptic reorganization are poorly understood. This study tests the hypothesis that a member of the DEG/ENaC family of cation channels functions as a molecular link between neural activity and synaptic stability. This work exploits a synaptic remodeling event in the nematode C. elegans in which ventral synapses for the DD class of GABA neurons are re-located to new connections with dorsal muscles during larval development. This synaptic remodeling program is blocked by the UNC-55/COUP TF transcription factor in VD motor neurons, which normally synapse with ventral muscles. The Miller lab exploited this UNC-55 function in a cell-specific profiling strategy to identify 19 conserved genes with roles in synaptic remodeling. My work has now shown that one of these UNC-55 targets, the degenerin/epithelial sodium channel (DEG/ENaC), UNC-8, promotes synaptic remodeling in a mechanism that is activated by GABAergic signaling. This finding is important because DEG/ENaC proteins have been implicated in learning and memory but the molecular pathways that connect DEG/ENaC function to synaptic plasticity are largely unknown. Specific Aim 1 tests the prediction that GABA neuron activity drives the remodeling process in a cell autonomous mechanism. Specific Aim 2 tests the key hypothesis that UNC-8 localizes to the presynaptic regions of GABA neurons and functions in these cells to promote remodeling. Specific Aim 3 tests the novel prediction that UNC-8 is activated by the transient depletion of extracellular calcium that accompanies GABA release and that this effect triggers disassembly of the presynaptic apparatus. The results of this study will provide a better understanding of the cellular mechanisms that connect circuit activity to dynamic events at the synapse. Additionally, this study may provide insights that reveal the biological basis of mental disorders that arise from dysfunctional synaptic connectivity.