Searching for the Cannabidiol Binding Site on the α7 Nicotinic Acetylcholine Receptor

Abstract

The α7 nicotinic receptor is an acetylcholine-gated ion channel found in both neuronal and non-neuronal cells. Reduced α7 activity is associated with neurological and neurodegenerative disorders, whereas increased α7 activity may promote cancer progression. Therefore, both potentiation and inhibition of the receptor are of therapeutic interest. Cannabidiol (CBD), widely used for its therapeutic benefits and lack of psychoactive effects, is a known modulator of α7. Using patch-clamp recordings, we showed that CBD exerts two distinct modulatory effects on α7, each occurring at different time scales: a rapid reduction in the frequency of activation episodes, followed by a delayed effect characterized by prolonged activation episodes after several minutes. To predict CBD’s binding sites, we employed molecular dynamics simulations of α7 in both resting and desensitized states, embedded in a POPC:POPA:CHOL membrane with CBD molecules. Several candidate binding sites emerged for each receptor state. Representative structures were then backmapped to atomistic detail and further simulated to explore the stability and interactions at each site. In both states, the most stable binding site was located near the top of the transmembrane domain. Contact analysis identified multiple residues of interest for mutagenesis. Electrophysiological recordings of mutant receptors, compared to wild-type, displayed altered sensitivity to CBD’s effects, with some mutants showing reduced sensitivity to the immediate inhibitory effect, while others were more responsive to the kinetic changes. These findings confirm the role of specific residues in the allosteric modulation of α7 by CBD, with different residues contributing to its distinct effects on receptor function