Subtype-specific modulation of human K_V 7 channels by the anticonvulsant cannabidiol through a lipid-exposed...

Cannabidiol (CBD) is used clinically as an anticonvulsant. Its precise mechanism of action has remained unclear. CBD was recently demonstrated to enhance the activity of the neuronal K_V 7.2/7.3 channel, which may be one important contributor to CBD anticonvulsant effect. Curiously, CBD inhibits the closely related cardiac K_V 7.1/KCNE1 channel. Whether and how CBD affects other K_V 7 subtypes remains uninvestigated and the CBD interaction sites mediating these diverse effects remain unknown.

Here, we used electrophysiology, molecular dynamics simulations, molecular docking and site-directed mutagenesis to address these questions.

We found that CBD modulates the activity of all human K_V 7 subtypes and that the effects are subtype dependent. CBD enhanced the activity of K_V 7.2-7.5 subtypes, seen as a V₅₀ shift towards more negative voltages or increased maximum conductance. In contrast, CBD inhibited the K_V 7.1 and K_V 7.1/KCNE1 channels, seen as a V₅₀ shift towards more positive voltages and reduced conductance. In K_V 7.2 and K_V 7.4, we propose a CBD interaction site at the subunit interface in the pore domain that overlaps with the interaction site of other compounds, notably the anticonvulsant retigabine. However, CBD relies on other residues for its effects than the conserved tryptophan that is critical for retigabine effects. We propose a similar, though not identical CBD site in K_V 7.1, with a non-conserved phenylalanine being important.

We identify novel targets of CBD, contributing to a better understanding of CBD clinical effects and provide mechanistic insights into how CBD modulates different K_V 7 subtypes.