title: The role of the IsK protein in the specific pharmacological properties of the IKs channel complex.
abstract: IKs channels are composed of IsK and KvLQT1 subunits and underly the slowly activating, voltage-dependent IKs conductance in heart. Although it appears clear that the IsK protein affects both the biophysical properties and regulation of IKs channels, its role in channel pharmacology is unclear. In the present study we demonstrate that KvLQT1 homopolymeric K+ channels are inhibited by the IKs blockers 293B, azimilide and 17-beta-oestradiol. However, IKs channels induced by the coexpression of IsK and KvLQT1 subunits have a 6-100 fold higher affinity for these blockers. Moreover, the IKs activators mefenamic acid and DIDS had little effect on KvLQT1 homopolymeric channels, although they dramatically enhanced steady-state currents through heteropolymeric IKs channels by arresting them in an open state. In summary, the IsK protein modulates the effects of both blockers and activators of IKs channels. This finding is important for the action and specificity of these drugs as IsK protein expression in heart and other tissues is regulated during development and by hormones.
authors.affiliation: Max-Planck-Institut für experimentelle Medizin, Göttingen, Germany.
authors.forename: A E
authors.initials: AE
authors.lastname: Busch
authors.forename: G L
authors.initials: GL
authors.lastname: Busch
authors.forename: E
authors.initials: E
authors.lastname: Ford
authors.forename: H
authors.initials: H
authors.lastname: Suessbrich
authors.forename: H J
authors.initials: HJ
authors.lastname: Lang
authors.forename: R
authors.initials: R
authors.lastname: Greger
authors.forename: K
authors.initials: K
authors.lastname: Kunzelmann
authors.forename: B
authors.initials: B
authors.lastname: Attali
authors.forename: W
authors.initials: W
authors.lastname: Stühmer
mesh_terms: D000818:Animals; D002839:Chromans / Q000494:pharmacology*; D004958:Estradiol / Q000494:pharmacology*; D006801:Humans; D006827:Hydantoins; D007093:Imidazoles / Q000494:pharmacology*; D048289:Imidazolidines; D051656:KCNQ Potassium Channels; D051657:KCNQ1 Potassium Channel; D008528:Mefenamic Acid / Q000494:pharmacology*; D051379:Mice; D009865:Oocytes / Q000378:metabolism; D018408:Patch-Clamp Techniques; D010879:Piperazines / Q000494:pharmacology*; D015221:Potassium Channels / Q000096:biosynthesis / Q000187:drug effects* / Q000502:physiology*; D024642:Potassium Channels, Voltage-Gated; D013449:Sulfonamides / Q000494:pharmacology*; D014981:Xenopus
chemical_list: D002839:Chromans; D006827:Hydantoins; D007093:Imidazoles; D048289:Imidazolidines; D051656:KCNQ Potassium Channels; D051657:KCNQ1 Potassium Channel; C496909:KCNQ1 protein, human; C496910:Kcnq1 protein, mouse; D010879:Piperazines; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated; D013449:Sulfonamides; C059983:potassium channel protein I(sk); C103474:6-cyano-4-(N-ethylsulfonyl-N-methylamino)-3-hydroxy-2,2-dimethylchromane; D008528:Mefenamic Acid; D004958:Estradiol; C086123:azimilide