Pharmacological analysis of negative allosteric modulation of the α7 nicotinic receptor by polyunsaturated free fatty acids

This is the authors' abstract. We don't add key points for this paper.

The α7 nicotinic acetylcholine receptor is a pentameric ligand-gated ion channel mediating cholinergic signaling. Its implication in neurological disorders and inflammation has spurred the development of synthetic effectors, either orthosteric agonists acting on the extracellular domain, or positive allosteric modulators (PAMs) acting at the transmembrane domain. In this context, endogenous polyunsaturated free fatty acids (PUFAs) were early recognized to modulate the receptor function, but their site of action remained unexplored. Here, we characterized a series of PUFAs by two-electrode voltage-clamp (TEVC) electrophysiology and used coarse-grained molecular dynamics (CG-MD) simulations coupled to mutational analysis to identify their binding sites. Data reveal that PUFAs are negative allosteric modulators (NAMs) whose strength depends on the length and degree of unsaturation of the hydrophobic tail and the polarity of the head group. Combined CG-MD and mutational data identified a major “structural” intrasubunit M1/M4 site which does not contribute to the NAM effect, and a minor intersubunit M3 + /M1- site where mutations strongly impair NAM activity. The M3 + /M1- site overlaps with the site for synthetic PAMs, showing a common hotspot for positive and negative allosteric modulation with implications for drug design and functional regulation in physiological conditions.