Présentation
Nicotinic acetylcholine receptors (nAchRs) are ligand-gated ion channels that regulate chemical transmission at the neuromuscular junction. They are responsible for signal transmission, and their function is regulated by neurotransmitters, agonists, and antagonists drugs. A detailed knowledge of their conformational transition in response to ligand binding is critical to understanding the basis of ligand-receptor interaction, in view of new pharmacological approaches to control receptor activity. The scarcity of experimental structures of human channels makes this perspective extremely challenging. To contribute overcoming this issue, we built, via homology modeling, and assessed, via extended molecular dynamics, an all-atom structural model of the human alpha7 nicotinic receptor in different conformations: the open-active conformation corresponding to the conductive state [1] and three different nonconductive conformations describing three different closed states: a desensitized [2], a closed-locked [3] and an apo-resting conformational state [3]. We carefully compared our structures with available experimental data and computational models of other eukaryotic LGICs, identifying key discriminators among states (in particular quaternary rearrangements, pore hydration level, intra-protein H-bonds networks, water rings in the pore), and therefore providing a detailed structural characterization of the conformational landscape of the human alpha7 receptor.