Department of Anesthesiology, Washington University, Saint Louis, United States.
Department of Internal Medicine, Mass Spectrometry Resource, Division of Endocrinology, Diabetes, Metabolism, and Lipid Research, Washington University, Saint Louis, United States.
Elife. 2019 Nov 14;8:e50766. doi: 10.7554/eLife.50766.
Pentameric ligand-gated ion channels (pLGICs) are essential determinants of synaptic transmission, and are modulated by specific lipids including anionic phospholipids. The exact modulatory effect of anionic phospholipids in pLGICs and the mechanism of this effect are not well understood. Using native mass spectrometry, coarse-grained molecular dynamics simulations and functional assays, we show that the anionic phospholipid, 1-palmitoyl-2-oleoyl phosphatidylglycerol (POPG), preferentially binds to and stabilizes the pLGIC, Erwinia ligand-gated ion channel (ELIC), and decreases ELIC desensitization. Mutations of five arginines located in the interfacial regions of the transmembrane domain (TMD) reduce POPG binding, and a subset of these mutations increase ELIC desensitization. In contrast, a mutation that decreases ELIC desensitization, increases POPG binding. The results support a mechanism by which POPG stabilizes the open state of ELIC relative to the desensitized state by direct binding at specific sites.
五聚体配体门控离子通道（pLGICs）是突触传递的重要决定因素，受特定脂质的调节，包括阴离子磷脂。阴离子磷脂在 pLGICs 中的精确调节作用及其作用机制尚不清楚。本研究采用天然质谱、粗粒分子动力学模拟和功能测定，表明阴离子磷脂 1-棕榈酰基-2-油酰基磷脂酰甘油（POPG）优先与 Erwinia 配体门控离子通道（ELIC）结合并稳定该通道，从而降低 ELIC 的脱敏。位于跨膜域（TMD）界面区域的五个精氨酸的突变会减少 POPG 的结合，其中一部分突变会增加 ELIC 的脱敏。相反，降低 ELIC 脱敏的突变会增加 POPG 的结合。这些结果支持了一种机制，即 POPG 通过在特定部位直接结合，相对于脱敏状态稳定 ELIC 的开放状态。
