Characterization of Alcohol Modulation of a Pentameric Ligand-gated Ion Channel with Electrophysiology and Molecular Dynamics Simulations

Abstract: Pentameric ligand-gated ion channels (pLGICs) are membrane receptors that play a crucial role in every living organism. The pLGIC protein structure forms a pore through the membrane of a cell that can let specific ions pass through, upon activation by endogenous agonists. pLGICs are allosterically modulated by ligands binding at allosteric sites, that either stabilize a certain conformation or change the binding affinity of the endogenous agonist. However, much remains unknown about the exact way in which these modulators bind to and affect pLGICs. An increased understanding could help in the search for novel and/or more effective target drugs. With this masters thesis, I hope to contribute by investigating the modulatory effect of ethanol on the bacterial Gloeobacter ligand-gated ion channel (GLIC). This has been done by performing oocyte electrophysiology recordings and analysis of molecular dynamics simulations, both with and without ethanol, and of four separate variants of GLIC that are either potentiated or inhibited by ethanol. Two possible allosteric sites were discovered in a transmembraneintrasubunit pocket: a potentiating allosteric site close to the M2 helix and residue V242, as well as an inhibitory membrane- and M4 helix-close intrasubunit site. Finally, evidence was found that could support a previously suggested inhibitory allosteric site in the pore around the 9’ hydrophobic gate.