Actions and Mechanisms of Polyunsaturated Fatty Acids on Voltage-Gated Ion Channels

Polyunsaturated fatty acids (PUFAs) act on most ion channels, thereby having significant physiological and pharmacological effects. In this review we summarize data from numerous PUFAs on voltage-gated ion channels containing one or several voltage-sensor domains, such as voltage-gated sodium (NaV), potassium (KV), calcium (CaV), and proton (HV) channels, as well as calcium-activated potassium (KCa), and transient receptor potential (TRP) channels. Some effects of fatty acids appear to be channel specific, whereas others seem to be more general. Common features for the fatty acids to act on the ion channels are at least two double bonds in cis geometry and a charged carboxyl group. In total we identify and label five different sites for the PUFAs. PUFA site 1: The intracellular cavity. Binding of PUFA reduces the current, sometimes as a time-dependent block, inducing an apparent inactivation. PUFA site 2: The extracellular entrance to the pore. Binding leads to a block of the channel. PUFA site 3: The intracellular gate. Binding to this site can bend the gate open and increase the current. PUFA site 4: The interface between the extracellular leaflet of the lipid bilayer and the voltage-sensor domain. Binding to this site leads to an opening of the channel via an electrostatic attraction between the negatively charged PUFA and the positively charged voltage sensor. PUFA site 5: The interface between the extracellular leaflet of the lipid bilayer and the pore domain. Binding to this site affects slow inactivation. This mapping of functional PUFA sites can form the basis for physiological and pharmacological modifications of voltage-gated ion channels.Funding Agencies|Swedish Research Council; Swedish Brain Foundation; Swedish Society for Medical Research; Swedish Heart-Lung Foundation</p

Long-QT mutations in KCNE1 modulate the 17β-estradiol response of Kv7.1/KCNE1.

Estradiol (17[Formula: see text]-E2) is implicated in higher arrhythmia risk of women with congenital or acquired long-QT syndrome (LQTS) compared to men. However, the underlying mechanisms remain poorly understood, and little is known about the impact of LQTS-associated mutations. We show that 17[Formula: see text]-E2 inhibits the human cardiac Kv7.1/KCNE1 channel expressed in Xenopus oocytes. We find that the 17[Formula: see text]-E2 effect depends on the Kv7.1 to KCNE1 stoichiometry, and we reveal a critical function of the KCNE1 carboxyl terminus for the effect. LQTS-associated mutations in the KCNE1 carboxyl terminus show a range of responses to 17[Formula: see text]-E2, from a wild-type like response to impaired or abolished response. Together, this study increases our understanding of the mechanistic basis for 17[Formula: see text]-E2 inhibition of Kv7.1/KCNE1 and demonstrates mutation-dependent responses to 17[Formula: see text]-E2. These findings suggest that the 17[Formula: see text]-E2 effect on Kv7.1/KCNE1 might contribute to the higher arrhythmia risk of women, particularly in carriers with specific LQTS-associated mutations

Liability of a Surgeon for the Extension of an Authorized Operation

Polyunsaturated fatty acids modulate the voltage dependence of several voltage-gated ion channels, thereby being potent modifiers of cellular excitability. Detailed knowledge of this molecular mechanism can be used in designing a new class of small-molecule compounds against hyperexcitability diseases. Here, we show that arginines on one side of the helical K-channel voltage sensor S4 increased the sensitivity to docosahexaenoic acid (DHA), whereas arginines on the opposing side decreased this sensitivity. Glutamates had opposite effects. In addition, a positively charged DHA-like molecule, arachidonyl amine, had opposite effects to the negatively charged DHA. This suggests that S4 rotates to open the channel and that DHA electrostatically affects this rotation. A channel with arginines in positions 356, 359, and 362 was extremely sensitive to DHA: 70 mu M DHA at pH 9.0 increased the current greater than500 times at negative voltages compared with wild type (WT). The small-molecule compound pimaric acid, a novel Shaker channel opener, opened the WT channel. The 356R/359R/362R channel drastically increased this effect, suggesting it to be instrumental in future drug screening

ASIC3, a proton-gated ion channel with preference for polyunsaturated lipids with specific headgroup and tail properties

Funding Agencies|Swedish Research Council [2021-01885]</p

Polyunsaturated Fatty Acids as Modulators of K(V)7 Channels

Voltage-gated potassium channels of the K(V)7 family are expressed in many tissues. The physiological importance of K(V)7 channels is evident from specific forms of disorders linked to dysfunctional K(V)7 channels, including variants of epilepsy, cardiac arrhythmia and hearing impairment. Thus, understanding how K(V)7 channels are regulated in the body is of great interest. This Mini Review focuses on the effects of polyunsaturated fatty acids (PUFAs) on K(V)7 channel activity and possible underlying mechanisms of action. By summarizing reported effects of PUFAs on K(V)7 channels and native K(V)7-mediated currents, we conclude that the generally observed effect is a PUFA-induced increase in current amplitude. The increase in current is commonly associated with a shift in the voltage-dependence of channel opening and in some cases with increased maximum conductance. Auxiliary KCNE subunits, which associate with K(V)7 channels in certain tissues, may influence PUFA effects, though findings are conflicting. Both direct and indirect activating PUFA effects have been described, direct effects having been most extensively studied on K(V)7.1. The negative charge of the PUFA head-group has been identified as critical for electrostatic interaction with conserved positively charged amino acids in transmembrane segments 4 and 6. Additionally, the localization of double bonds in the PUFA tail tunes the apparent affinity of PUFAs to K(V)7.1. Indirect effects include those mediated by PUFA metabolites. Indirect inhibitory effects involve K(V)7 channel degradation and re-distribution from lipid rafts. Understanding how PUFAs regulate K(V)7 channels may provide insight into physiological regulation of K(V)7 channels and bring forth new therapeutic strategies.Funding Agencies|European Research Council (ERC) under the European Unions Horizon 2020 research and innovation programEuropean Research Council (ERC) [850622]</p