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Accueil > Teams > Pharmacognosy - Chemistry of Natural Products > PENTAGATE : Mechanisms of activation and desensitization of a pentameric channel receptor

PENTAGATE : Mechanisms of activation and desensitization of a pentameric channel receptor

The team of "Chimie des Substances Naturelles" (D. Joseph) is one partner of the ANR project untitled PENTAGATE which is coordinated by P.-J. Corringer (unit “Récepteurs-Canaux”, Institut Pasteur). Ligand-gated ion channels (LGICs) are key players in cellular excitability, neuronal communication and brain computation. While the three-dimensional structures of the major classes of LGICs have been solved by X-ray crystallography, the molecular mechanisms of their function remain poorly understood. Our project focuses on pentameric LGICs (pLGICs) that mediates neurotransmission by acetylcholine, serotonin, GABA and glycine. The latter are also major therapeutic targets for anxiolytics, sedatives, general anesthetics, cognitive facilitators, neuroprotectors (Alzheimer’s and Parkinson’s) and anti-smoking compounds. Through a study of the bacterial homolog from Gloeobacter violaceus named GLIC, PENTAGATE aims (i) to understand the molecular mechanisms of signal transduction of pLGICs, (ii) to identify new potential binding sites and (iii) to understand their reorganization during activation and desensitization. In this project, we will use environmentally friendly chemistry to prepare original ligands that will enable the stabilization of a given conformation of GLIC. In this way, the caffeic acid recently identified as ligand will serve as hit compound for the development of a series of ligands able to modulate the activity of GLIC. Highly soluble derivatives with anomalous or fluorescent properties will be developed to carry out crystallization, electrophysiology and fluorescence experiments. Indeed, GLIC mutants and GLIC-ligand complexes will be involved in crystallization experiments for the resolution of new conformations. In return, the contribution of these new conformations in the protein function will be explored by the labeling of GLIC by conformational fluorescent reporter. Experiments at equilibrium and resolved in time on GLIC reconstituted in liposome will allow to assign crystallographic conformations to allosteric state, whether rest, active, desensitized, or even intermediate. Finally, the molecular mechanisms explaining allosteric reorganizations will be explored by molecular dynamics on GLIC inserted into an explicit lipid membrane.