Lipid Modulation of Ligand-Gated Ion Channels

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Project Summary/Abstract Pentameric ligand-gated ion channels (pLGICs) mediate synaptic transmission and are the targets of many neuroactive drugs, which are allosteric modulators of pLGIC activity. Endogenous lipids including phospholipids, fatty acids and steroids are also allosteric modulators of pLGICs, and the effects of these lipids are fundamental to our understanding of pLGIC biology and regulation. The long-term goal of this project is to understand the molecular mechanisms by which lipids modulate pLGICs. We have developed innovative biophysical and biochemical techniques to examine lipid binding and modulation in the model pLGIC, Erwinia chrysanthemi ligand-gated ion channel (ELIC), including native ion mobility mass spectrometry (MS), functional analysis in model membranes, and covalent modification/photolabeling. Using these techniques, we discovered that the anionic phospholipid, 1-palmitoyl-2-oleoyl-phosphatidylglycerol (POPG), directly binds to ELIC and modulates channel gating by stabilizing the open relative to the desensitized state. We now propose to investigate the mechanisms of phospholipid, fatty acid and steroid modulation of two model pLGICs, ELIC and GLIC (Gloeobacter ligand-gated ion channel), with a focus on elucidating the specificity and sites of interaction, and the effects of lipid binding. The overall vision of this research program is to develop a detailed structural model of lipid modulation of pLGICs that encompasses the potential diversity of mechanisms present in different pLGICs.