Molecular mechanisms underlying the effect of the novel BK channel opener GoSlo: Involvement of the S4/S5 linker and the S6 segment

Abstract

GoSlo-SR-5-6 is a novel large-conductance Ca 2+ -activated K + (BK) channel agonist that shifts the activation V 1/2 of these channels in excess of −100 mV when applied at a concentration of 10 μM. Although the structure-activity relationship of this family of molecules has been established, little is known about how they open BK channels. To help address this, we used a combination of electrophysiology, mutagenesis, and mathematical modeling to investigate the molecular mechanisms underlying the effect of GoSlo-SR-5-6. Our data demonstrate that the effects of this agonist are practically abolished when three point mutations are made: L227A in the S4/S5 linker in combination with S317R and I326A in the S6C region. Our data suggest that GoSlo-SR-5-6 interacts with the transmembrane domain of the channel to enhance pore opening. The Horrigan-Aldrich model suggests that GoSlo-SR-5-6 works by stabilizing the open conformation of the channel and the activated state of the voltage sensors, yet decouples the voltage sensors from the pore gate.

Vasodilation of rat skeletal muscle arteries by the novel BK channel opener GoSlo is mediated by the simultaneous activation of BK and Kv7 channels

“…This supports the idea that they relaxed Gracilis muscle arteries by activating both BK and K v 7 channels. This dual action of GoSlo‐SR compounds on BK and K v 7.4/K v 7.5 channels is further supported by the findings made on single cells expressing these channels, that is, (a) our findings reported in the present study demonstrating that GoSlo‐SR compounds produce a large stimulation of native BK currents and K v 7.4 and K v 7.5 channels and (b) previously published findings showing that GoSlo‐SR compounds activate expressed as well as native BK channels (Hannigan et al, ; Kshatri et al, ; Large et al, ; Roy et al, ; Roy et al, ; Webb et al, ). Incidentally, the BK channel opener NS11021 has been shown to stimulate expressed K v 7.4 channels (Bentzen et al, ), and BMS204352 activates both BK and K v 7 channels (Schroder, Strobaek, Olesen, & Christophersen, ).…”

“…These data suggested that GoSlo‐SR compounds either interfered with the binding of BK channel blockers or that they activated other K + channels. The former explanation appears unlikely, given that the effects of GoSlo‐SR compounds have been shown to be blocked with IBTX and penitrem A in tissue strips (Hannigan et al, ; Large et al, ) and in single cells (Webb et al, ) and that in our study IBTX inhibited the effect of GoSlo‐SR compounds in the tail artery and regained a blocking effect against GoSlo‐SR compounds in the presence of the K v 7 channel inhibitor XE991 (for more details, see below).…”

“…Recently, a more efficacious family of BK channel openers called the GoSlo‐SR compounds have been developed (Roy et al, ; Roy et al, ). The efficacy of some of them has been reported to depend on the presence of BK channel regulatory β and γ‐subunits (Kshatri et al, ; Large et al, ; Webb et al, ). These compounds, in particular GoSlo‐SR‐5‐130 and GoSlo‐SR‐5‐6,activated BK channels in freshly isolated smooth muscle cells from rabbit bladder (Large et al, ), rabbit corpus cavernosum (Hannigan et al, ), and bronchial smooth muscle (Bradley et al, ).…”

“…These compounds, in particular GoSlo‐SR‐5‐130 and GoSlo‐SR‐5‐6,activated BK channels in freshly isolated smooth muscle cells from rabbit bladder (Large et al, ), rabbit corpus cavernosum (Hannigan et al, ), and bronchial smooth muscle (Bradley et al, ). Furthermore, Webb et al () demonstrated that the effects of GoSlo‐SR‐5‐6 were reduced by >80%, when a triplet of mutations were introduced on the S4/S5 linker and S6 helix.…”

Differential regulation of BK channels by fragile X mental retardation protein

“…where L 0 is the value of L at 0 mV, Z L is the partial charge associated with the channel opening (C → O), and V, K, and T are same as above. The logarithmic slope of the P O -V curve relationship gives the mean activation displacement Qa, which estimates the total charge movement upon channel opening (Sigg and Bezanilla, 1997;Webb et al, 2015). This is defined as (Eq.…”