Résumé : In this work, we study the mechanisms of classical activation and inactivation of signal transduction by the histamine H3 receptor, a 7-helix transmembrane bundle G-Protein Coupled Receptor through long-time-scale molecular dynamics simulations of the receptor embedded in a hydrated double layer of dipalmitoyl phosphatidyl choline, a zwitterionic poly-saturated ordered lipid. Three systems were prepared: the apo receptor, representing the constitutively active receptor; and two holo-receptors -the receptor coupled to the antagonist/inverse agonist ciproxifan and representing the inactive state of the receptor, and the receptor coupled to the endogenous agonist histamine and representing the active state of the receptor.
Abstract : An extensive analysis of the simulation shows that the three states of H3R present significant structural and dynamical differences, as well as a complex behavior given that the measured properties interact in multiple and inter-dependent ways. In addition, the simulations describe an unexpected escape of histamine from the orthosteric binding site, in agreement with the experimental modest affinities and rapid off-rates of agonists.