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.
OBJECTIVE
N,No-[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 (I(K)) and fast transient K+ currents (I(A)) with IC50 values of 2.1+/-1.1 micromol/L and 27.8+/-1.5 micromol/L, respectively. The inhibition was voltage independent. OMBSA markedly accelerated the decay time course of IK, without a significant effect on that of I(A). 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 I(A) and slowed down its recovery from inactivation. Intracellular dialysis of OMBSA had no effect on both I(K) and I(A).


CONCLUSIONS
The results demonstrate that OMBSA blocks both I(K) and I(A) 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.
Gao
Zhao-bing
ZB
State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China.
Chen
Xue-qin
XQ
Jiang
Hua-liang
HL
Liu
Hong
H
Hu
Guo-yuan
GY
D000818:Animals; D000831:Animals, Newborn; D001555:Benzene Derivatives / Q000494:pharmacology*; D051668:Delayed Rectifier Potassium Channels / Q000037:antagonists & inhibitors / Q000502:physiology; D004594:Electrophysiology; D006624:Hippocampus / Q000166:cytology / Q000502:physiology; D020128:Inhibitory Concentration 50; D015640:Ion Channel Gating / Q000187:drug effects; D007700:Kinetics; D015394:Molecular Structure; D008970:Molecular Weight; D009474:Neurons / Q000187:drug effects / Q000502:physiology; D018408:Patch-Clamp Techniques; D026902:Potassium Channel Blockers / Q000737:chemistry / Q000494:pharmacology*; D015221:Potassium Channels / Q000187:drug effects / Q000502:physiology; D024642:Potassium Channels, Voltage-Gated / Q000378:metabolism; D017966:Pyramidal Cells / Q000187:drug effects / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013449:Sulfonamides / Q000737:chemistry / Q000494:pharmacology*; D019789:Tetraethylammonium / Q000494:pharmacology; D000096926:Benzenesulfonamides
D001555:Benzene Derivatives; D051668:Delayed Rectifier Potassium Channels; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated; D013449:Sulfonamides; D019789:Tetraethylammonium; D000096926:Benzenesulfonamides; C540255:N,N'-(oxybis(2,1-ethanediyloxy-2,1-ethanediyl))bis(4-methyl)-benzenesulfonamide