title: Electrophysiological characterization of 14-benzoyltalatisamine, a selective blocker of the delayed rectifier K+ channel found in virtual screening.
abstract: 14-Benzoyltalatisamine is a potent and selective blocker of the delayed rectifier K+ channel found in a computational virtual screening study. The compound was found to block the K+ channel from the extracellular side. However, it is unclear whether 14-benzoyltalatisamine shares the same block mechanism with tetraethylammonium (TEA). In order to elucidate how the hit compound found by the virtual screening interacts with the outer vestibule of the K+ channel, the effects of 14-benzoyltalatisamine and TEA on the delayed rectifier K+ current of rat dissociated hippocampal neurons were compared using whole-cell voltage-clamp recording. External application of 14-benzoyltalatisamine and TEA reversibly inhibited the current with IC50 values of 10.1+/-2.2 microM and 1.05+/-0.21 mM, respectively. 14-Benzoyltalatisamine exerted voltage-dependent inhibition, markedly accelerated the decay of the current, and caused a significant hyperpolarizing shift of the steady-state activation curve, whereas TEA caused voltage-independent inhibition, without affecting the kinetic parameters of the current. The blockade by 14-benzoyltalatisamine, but not by TEA, was significantly diminished in a high K+ (60 mM) external solution. The potency of 14-benzoyltalatisamine was markedly reduced in the presence of 15 mM TEA. The results suggest that 14-benzoyltalatisamine bind to the external pore entry of the delayed rectifier K+ channel with partial insertion into the selectivity filter, which is in conformity with that predicted by the molecular docking model in the virtual screening.
authors.affiliation: State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, 555 Zu-Chong-Zhi Road, Shanghai 201203, PR China.
authors.forename: Ming-Ke
authors.initials: MK
authors.lastname: Song
authors.forename: Hong
authors.initials: H
authors.lastname: Liu
authors.forename: Hua-Liang
authors.initials: HL
authors.lastname: Jiang
authors.forename: Jian-Min
authors.initials: JM
authors.lastname: Yue
authors.forename: Guo-Yuan
authors.initials: GY
authors.lastname: Hu
mesh_terms: D000157:Aconitine / Q000031:analogs & derivatives* / Q000737:chemistry / Q000494:pharmacology; D000818:Animals; D051668:Delayed Rectifier Potassium Channels / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D008564:Membrane Potentials / Q000187:drug effects; D015394:Molecular Structure; D011188:Potassium / Q000494:pharmacology; D026902:Potassium Channel Blockers / Q000737:chemistry / Q000494:pharmacology*; D017966:Pyramidal Cells / Q000187:drug effects / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D019789:Tetraethylammonium / Q000494:pharmacology; D013997:Time Factors
chemical_list: C114773:14-benzoyltalitasamine; D051668:Delayed Rectifier Potassium Channels; D026902:Potassium Channel Blockers; D019789:Tetraethylammonium; D011188:Potassium; D000157:Aconitine