Department of Genetics, Yale School of Medicine, Howard Hughes Medical Institute, New Haven, CT 06510
Laboratory of Systems Pharmacology, Program in Therapeutic Science, Harvard Medical School, Boston, MA 02115.
eNeuro. 2020 Apr 22;7(2). doi: 10.1523/ENEURO.0369-19.2020. Print 2020 Mar/Apr.
Altered synaptic function is thought to play a role in many neurodegenerative diseases, but little is known about the underlying mechanisms for synaptic dysfunction. The squid giant synapse (SGS) is a classical model for studying synaptic electrophysiology and ultrastructure, as well as molecular mechanisms of neurotransmission. Here, we conduct a multidisciplinary study of synaptic actions of misfolded human G85R-SOD1 causing familial amyotrophic lateral sclerosis (ALS). G85R-SOD1, but not WT-SOD1, inhibited synaptic transmission, altered presynaptic ultrastructure, and reduced both the size of the readily releasable pool (RRP) of synaptic vesicles and mobility from the reserved pool (RP) to the RRP. Unexpectedly, intermittent high-frequency stimulation (iHFS) blocked inhibitory effects of G85R-SOD1 on synaptic transmission, suggesting aberrant Ca signaling may underlie G85R-SOD1 toxicity. Ratiometric Ca imaging showed significantly increased presynaptic Ca induced by G85R-SOD1 that preceded synaptic dysfunction. Chelating Ca using EGTA prevented synaptic inhibition by G85R-SOD1, confirming the role of aberrant Ca in mediating G85R-SOD1 toxicity. These results extended earlier findings in mammalian motor neurons and advanced our understanding by providing possible molecular mechanisms and therapeutic targets for synaptic dysfunctions in ALS as well as a unique model for further studies.
突触功能的改变被认为在许多神经退行性疾病中发挥作用，但对于突触功能障碍的潜在机制知之甚少。鱿鱼巨大突触（SGS）是研究突触电生理学和超微结构以及神经递质传递分子机制的经典模型。在这里，我们对导致家族性肌萎缩侧索硬化症（ALS）的错误折叠的人 G85R-SOD1 的突触作用进行了多学科研究。G85R-SOD1 但不是 WT-SOD1，抑制突触传递，改变突触前超微结构，并减少易释放池（RRP）中的突触小泡大小和从保留池（RP）到 RRP 的流动性。出乎意料的是，间歇性高频刺激（iHFS）阻断了 G85R-SOD1 对突触传递的抑制作用，表明异常的 Ca 信号可能是 G85R-SOD1 毒性的基础。比率 Ca 成像显示 G85R-SOD1 引起的突触前 Ca 显著增加，这先于突触功能障碍。使用 EGTA 螯合 Ca 可防止 G85R-SOD1 引起的突触抑制，证实异常 Ca 在介导 G85R-SOD1 毒性中的作用。这些结果扩展了哺乳动物运动神经元中的早期发现，并通过为 ALS 中的突触功能障碍提供可能的分子机制和治疗靶点以及进一步研究的独特模型，推进了我们的理解。
