Molecular Mechanism of Polyunsaturated Fatty Acid Analogues as KV7.1-Channel Modulators

Abstract

Negatively charged analogues of polyunsaturated fatty acids (PUFAs) have been shown to activate the human KV7.1+KCNE1 channel, which generates the repolarizing cardiac IKs current. Specific PUFA analogues activate both wild type KV7.1+KCNE1 and KV7.1+KCNE1 containing Long QT syndrome-associated mutations. Therefore, PUFA analogues represent a new class of KV7.1+KCNE1 channel activators that may aid in development of novel anti-arrhythmic drugs. To determine the molecular mechanism of how PUFA analogues activate KV7.1+KCNE1, we here combine electrophysiology recordings and site-directed mutagenesis with a panel of PUFA analogues with distinct properties. We identify two main effects of PUFA analogues on KV7.1 that are dependent on discrete channel motifs. The first effect is a shift in the voltage dependence of channel opening that is critically dependent on specific S4 arginines in the voltage sensor domain of KV7.1. Intriguingly, different S4 arginines are important in KV7.1 and KV7.1+KCNE1. The second effect is alteration in the maximum conductance that is critically dependent on the S6 residue K326 in the pore domain of KV7.1. Both effects appear to be primarily electrostatic. Our findings provide novel insights into how KV7.1+KCNE1 channel activators, such as PUFA analogues, simultaneously may interact with the voltage sensor domain and the pore domain to alter channel activity. Our findings also contribute pharmacological support to the hypothesis that KV7.1 and KV7.1+KCNE1 open from different conformational states.