Closed-locked and Apo-resting State Structures of the Human α7 Nicotinic Receptor: a Computational Study

Letizia Chiodo (1) , Thérèse Malliavin (2) , Sergio Giuffrida , Luca Maragliano (3) , Grazia Cottone (4)

1 Center for Life Nano Science at Sapienza
2 Bioinformatique structurale - Structural Bioinformatics
3 Dpt of Neuroscience and Brain Technologies [Genova]
4 Department of Physics and Chemistry

Nicotinic acetylcholine receptors, belonging to the Cys-loop super-family of ligand-gated ion channels (LGICs), are membrane proteins present in neurons and at neuromuscular junctions. 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 understand the basis of ligand-receptor interaction, in view of new pharmacological approaches to control receptor activity. However, the scarcity of experimentally derived structures of human channels makes this perspective extremely challenging. To contribute overcoming this issue, we have recently reported structural models for the open and the desensitized states of the human α7 nicotinic receptor. Here, we provide all-atom structural models of the same receptor in two different non-conductive states. The first structure, built via homology modeling and relaxed with extensive Molecular Dynamics simulations, represents the receptor bound to the natural antagonist α-conotoxin ImI. After comparison with available experimental data and computational models of other eukaryotic LGICs, we deem it consistent with the "closed-locked" state. The second model, obtained with simulations from the spontaneous relaxation of the open, agonist-bound α7 structure after ligand removal, recapitulates the characteristics of the apo-resting state of the receptor. These results add to our previous work on the active and desensitized state conformations, contributing to the structural characterization of the conformational landscape of the human α7 receptor, and suggesting benchmarks to discriminate among conformations found in experiments or in simulations of LGICs. In particular key interactions at the interface between the extracellular domain and the transmembrane domain are identified, that could be critical to the α7 receptor function.

Domaines: Biologie structurale [q-bio.BM]; Bio-informatique [q-bio.QM]; Biophysique

Letizia Chiodo, Thérèse Malliavin, Sergio Giuffrida, Luca Maragliano, Grazia Cottone. Closed-locked and Apo-resting State Structures of the Human α7 Nicotinic Receptor: a Computational Study. Journal of Chemical Information and Modeling, 2018, ⟨10.1021/acs.jcim.8b00412⟩. ⟨hal-01907201⟩