title: Redox- and calmodulin-dependent S-nitrosylation of the KCNQ1 channel.
abstract: Nitric oxide (NO) is a gaseous signal mediator showing numerous important biological effects. NO has been shown in many instances to exhibit its action via the protein S-nitrosylation mechanism, in which binding of NO to Cys residues regulate protein function independently of activation of soluble guanylate cyclase. The direct link between protein S-nitrosylation and functional modulation, however, has been demonstrated only in limited examples. Furthermore, although most proteins have more than one Cys residue, the mechanism by which a certain Cys becomes a specific target residue of S-nitrosylation is poorly understood. We have previously reported that NO regulates currents through the cardiac slowly activating delayed rectifier potassium channel (I(Ks)) irrespective of soluble guanylate cyclase activation. Here we demonstrate using a biotin-switch assay that NO induced S-nitrosylation of the alpha-subunit of the I(Ks) channel, KCNQ1, at Cys(445) in the C terminus. A redox motif flanking Cys(445) and the interaction of KCNQ1 with calmodulin are required for preferential S-nitrosylation of Cys(445). A patch clamp experiment shows that S-nitrosylation of Cys(445) modulates the KCNQ1/KCNE1 channel function. Our data provide a molecular basis of NO-mediated regulation of the I(Ks) channel. This novel regulatory mechanism of the I(Ks) channel may play a role in previously demonstrated NO-mediated phenomenon in cardiac electrophysiology, including shortening in action potential duration in response to intracellular Ca(2+) or sex hormones.
authors.affiliation: Department of Bio-informational Pharmacology, Medical Research Institute, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8510, Japan.
authors.forename: Ken
authors.initials: K
authors.lastname: Asada
authors.forename: Junko
authors.initials: J
authors.lastname: Kurokawa
authors.forename: Tetsushi
authors.initials: T
authors.lastname: Furukawa
mesh_terms: D000818:Animals; D002147:Calmodulin / Q000378:metabolism*; D002478:Cells, Cultured; D003545:Cysteine / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D006168:Guinea Pigs; D006801:Humans; D047468:Immunoprecipitation; D015640:Ion Channel Gating / Q000502:physiology*; D051657:KCNQ1 Potassium Channel / Q000235:genetics / Q000378:metabolism*; D007668:Kidney / Q000166:cytology / Q000378:metabolism; D032383:Myocytes, Cardiac / Q000166:cytology / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism*; D010084:Oxidation-Reduction; D018408:Patch-Clamp Techniques; D024642:Potassium Channels, Voltage-Gated / Q000235:genetics / Q000378:metabolism*
chemical_list: D002147:Calmodulin; C489622:KCNE1 protein, human; D051657:KCNQ1 Potassium Channel; C496909:KCNQ1 protein, human; D024642:Potassium Channels, Voltage-Gated; D009569:Nitric Oxide; D003545:Cysteine