Electrophysiological characterization of a novel Kv channel blocker N, N′-[oxybis(2,1-ethanediyloxy-2,1-ethanediyl)]bis(4-methyl)-benzenesulfonamide found in virtual screening
AbstractAim:N,N′-[oxybis(2,1-ethanediyloxy-2,1-ethanediyl)]bis(4-methyl)-benzenesulfonamide (OMBSA) is a hit compound with potent voltage-gated K+ (Kv) channel-blocking activities that was found while searching the MDL Available Chemicals Directory with a virtual screening approach. In the present study, the blocking actions of OMBSA on Kv channels and relevant mechanisms were characterized.Methods:Whole-cell voltage-clamp recording was made in acutely dissociated hippocampal CA1 pyramidal neurons of newborn rats.Results:Superfusion of OMBSA reversibly inhibited both the delayed rectifier (IK) and fast transient K+ currents (IA) with IC50 values of 2.1±1.1 μmol/L and 27.8±1.5 μmol/L, respectively. The inhibition was voltage independent. OMBSA markedly accelerated the decay time course of IK, without a significant effect on that of IA. OMBSA did not change the activation, steady-state inactivation of IK, and its recovery from inactivation, but the compound caused a significant hyperpolarizing shift of the voltage dependence of the steady-state inactivation of IA and slowed down its recovery from inactivation. Intracellular dialysis of OMBSA had no effect on both IK and IA.Conclusion:The results demonstrate that OMBSA blocks both IK and IA through binding to the outer mouth of the channel pore, as predicted by the molecular docking model used in the virtual screening. In addition, the compound differentially moderates the inactivation kinetics of the K+ channels through allosteric mechanisms.