Polyunsaturated fatty acids are potent openers of human M‐channels expressed in Xenopus laevis oocytes

Abstract

Methods: Effects of fatty acids and fatty-acid analogues on mouse dorsal root ganglion neurons and on the human K V 7.2/3 channel expressed in Xenopus laevis oocytes were studied using electrophysiology. Conclusions: These findings suggest that circulating polyunsaturated fatty acids, with a minimum requirement of multiple double bonds and a charged carboxyl group, dampen excitability by opening neuronal M-channels. Collectively, our data bring light to the molecular targets of polyunsaturated fatty acids and thus a possible mechanism by which polyunsaturated fatty acids reduce neuronal excitability. Results

Site and Mechanism of Action of Resin Acids on Voltage-Gated Ion Channels

“…PUFAs open the WT and 3R Shaker KV channel (Börjesson and Elinder, 2011;Börjesson et al, , 2010Elinder and Liin, 2017;Ottosson et al, 2014;Xu et al, 2008), and the human KV7.1 and KV7.2/7.3 channel (Liin et al, 2015(Liin et al, , 2016a(Liin et al, , 2016b, via an electrostatic mechanism of action, exerted on the positively charged voltage sensor S4 ( Figure 5B). The negatively charged carboxyl group facilitate the outward movement of the voltage sensor, in the final opening step, and as consequence the KV channels open at more negative membrane potentials ( Figure 5C) (Börjesson et al, , 2010Liin et al, 2015Liin et al, , 2016b. The hydrophobic tail, with at least two double bounds in cis-configuration, is needed for anchoring the PUFA close to the voltage sensor.…”

“…For measuring the early activation steps the W434F-ILT Shaker mutant (C245V, V369I, I372L, S376T, C426A, W434F) was used, because the W434F mutation remove the ion conduction (completely C-type inactivated) without affecting the gating currents (Perozo et al, 1993;Yang et al, 1997). The human M-type KV channel was expressed by co-injection of hKv7.3 and hKv7.2 in a 1:1 ratio (Liin et al, 2016b).…”

“…However, due to side effects (related to off-targets and/or metabolites) it was taken out of use (Garin Shkolnik et al, 2014;Stas et al, 2016;Tompson et al, 2016). In addition, both KV7.2 and KV7.3, have a similar charge profile around S4 to that of the Shaker KV channel, and it is known that the PUFA docosahexaenoic acid (DHA), that also acts via an electrostatic mechanism (Börjesson and Elinder, 2011), opens the hKV7.2/7.3 channel at low concentrations (Liin et al, 2016b).…”

“…The modulation of voltage-gated ion channels by different compounds, ions, toxins and lipids, is diverse in terms of binding site and mechanisms (Cestèle and Catterall, 2000;Elinder and Arhem, 2003;Liin et al, 2016b;Wulff et al, 2009). Metal ions affect the gating of voltage-gated ion channels, both electrostatically (e.g.…”

“…However, even for channels that have a similar charge profile at the top of the voltage sensor, quantitative differences are seen. For example, both PUFAs (Liin et al, 2016b) and resin acids (Article II) have a larger G(V)-shifting effect on the human M-type (hKV 7.2/7.3) channel than on the Shaker KV channel. Thus, suggesting that the affinity to the VSD and/or the closeness between the effector and gating charges also plays a role.…”