Lipid Modulation of Ligand-Gated Ion Channels

PROJECT SUMMARY The family of pentameric ligand-gated ion channels (pLGICs) mediate synaptic transmission in the brain and are the targets of many drugs. This project seeks to understand the structural basis of pLGIC activation by agonists and modulation by lipids. pLGICs are very sensitive to the lipid membrane environment, and therefore an accurate understanding of structure-function relationships in these channels requires consideration of the effects of lipids. Previously, we determined the activated open-channel structure of the model pLGIC, ELIC, and characterized the effect of phospholipids and fatty acids on ELIC activation and desensitization. Building upon these advancements, we will determine the structures of intermediate states of ELIC activation and the mechanism by which certain phospholipids support ELIC activity. This will be accomplished by a multidisciplinary approach using single particle cryo-EM, functional measurements in model membranes, pulsed-EPR, and molecular dynamics simulations. A major goal of this project is to perform both cryo-EM and functional analysis of pLGICs in liposomes of defined composition, thereby providing rigorous understanding into the structural basis of ion channel activation and the effects of lipids. We will also expand the project to investigate the lipid sensitivity of a human pLGIC, applying technical and biological insights gained from ELIC. The outcomes of this research are detailed structural models of pLGIC function: fundamental information that will facilitate the design of therapeutics targeting these ion channels.