Subtype‐specific modulation of human K_V7 channels by the anticonvulsant cannabidiol through a lipid‐exposed pore‐domain site

Abstract

Background and PurposeCannabidiol (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 KV7.2/7.3 channel, which may be one important contributor to CBD anticonvulsant effect. Curiously, CBD inhibits the closely related cardiac KV7.1/KCNE1 channel. Whether and how CBD affects other KV7 subtypes remains uninvestigated and the CBD interaction sites mediating these diverse effects remain unknown.Experimental ApproachHere, we used electrophysiology, molecular dynamics simulations, molecular docking and site‐directed mutagenesis to address these questions.Key ResultsWe found that CBD modulates the activity of all human KV7 subtypes and that the effects are subtype dependent. CBD enhanced the activity of KV7.2–7.5 subtypes, seen as a V50 shift towards more negative voltages or increased maximum conductance. In contrast, CBD inhibited the KV7.1 and KV7.1/KCNE1 channels, seen as a V50 shift towards more positive voltages and reduced conductance. In KV7.2 and KV7.4, 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 KV7.1, with a non‐conserved phenylalanine being important.Conclusions and ImplicationsWe identify novel targets of CBD, contributing to a better understanding of CBD clinical effects and provide mechanistic insights into how CBD modulates different KV7 subtypes.