Alkanols inhibit voltage-gated K(+) channels via a distinct gating modifying mechanism that prevents gate opening

Dual regulation of Kv7.2/7.3 channels by long-chain n-alcohols

Normal alcohols (n-alcohols) can induce anesthetic effects by acting on neuronal ion channels. Recent studies have revealed the effects of n-alcohols on various ion channels; however, the underlying molecular mechanisms remain unclear. Here, we provide evidence that long-chain n-alcohols have dual effects on Kv7.2/7.3 channels, resulting in channel activation as the net effect. Using heterologous expression systems, we found that n-alcohols could differentially regulate the Kv7.2/7.3 channel depending on their chain length. Treatment with short-chain ethanol and propanol diminished Kv7.2/7.3 currents, whereas treatment with long-chain hexanol and octanol enhanced the currents. However, the long-chain alcohols failed to potentiate Kv7.2 currents pre-activated by retigabine. Instead, they inhibited the currents, similar to short-chain ethanol. The stimulatory effect of the long-chain n-alcohols was also converted into an inhibitory one in the mutant Kv7.2(W236L) channels, while the inhibitory effect of ethanol did not differ between wild-type Kv7.2 and mutant Kv7.2(W236L). The inhibition of currents by n-alcohols was also seen in Kv7.1 channel which does not have the tryptophan (W) residue in S5. These findings suggest that long-chain n-alcohols exhibit dual effects through independent working sites on the Kv7.2 channel. Finally, we confirmed that the hydroxyl group with a negative electrostatic potential surface is essential for the dual actions of n-alcohol. Together, our data suggest that long-chain n-alcohols regulate Kv7.2/7.3 channels by interacting with both stimulatory and inhibitory sites and that their stimulatory action depends on the conserved tryptophan 236 residue in S5 and could be important for triggering their anesthetic effects.

Gambierol and n-alkanols inhibit Shaker Kv channel via distinct binding sites outside the K(+) pore

The marine polycyclic-ether toxin gambierol and 1-butanol (n-alkanol) inhibit Shaker-type Kv channels by interfering with the gating machinery. Competition experiments indicated that both compounds do not share an overlapping binding site but gambierol is able to affect 1-butanol affinity for Shaker through an allosteric effect. Furthermore, the Shaker-P475A mutant, which inverses 1-butanol effect, is inhibited by gambierol with nM affinity. Thus, gambierol and 1-butanol inhibit Shaker-type Kv channels via distinct parts of the gating machinery.