Voltage-gated K+ channel modulation by resin-acid derivatives - a computational study

Abstract: Voltage-gated K+ (Kv) channels are known to cause serious disease upon their malfunction. Kv channels desensitised to voltage show inability to fully repolarise the membrane in excitable cells, which can make the membrane hyperexcited and in turn cause seizures such as in epilepsy, periodic ataxia or heart arrhythmia. Therefore, enhancers of Kv channels could serve as potential drugs. Some of these enhancers are polyunsaturated fatty acids and resin-acids which bind at the proteinlipid surface and affect the movement of the voltage sensor in the channel by a mechanism called the lipoelectric effect. To explore the lipoelectric modulation mechanism, we have performed an extensive computational study including docking and molecular dynamics simulations on resin-acid derivatives added to a model potassium channel called Shaker. Four derivatives, Wu32 and Wu50 that excite the channel and thus induce repolarisation of the membrane, as well as Wu18 and Wu27, who were found to be non-potent in previous experimental studies, have helped to point out a novel binding site in Shaker. The site is located between the pore and voltage-sensing domain of the channel and is in direct contact with the first gating charge arginine, R1, and the residue W454. We hypothesize that it is possible for resinacid derivatives to directly bind to the voltage-sensor when it is in an activated state, prolonging the time Shaker stays open. Further experimental studies on Shaker and human homologs are now needed to test our hypothesis. Therefore, we suggest recording the sensitivity of Shaker towards potent derivatives in combination with mutations of W454. If our findings of the novel binding site are correct, the suitability of Shaker as a model system for human Kv channel modulation by lipoelectric modulators can be questioned as W454 is replaced by small hydrophobic side chains in mammalian Shaker homologs.