title: PKC-dependent regulation of Kv7.5 channels by the bronchoconstrictor histamine in human airway smooth muscle cells.
abstract: Kv7 potassium channels have recently been found to be expressed and functionally important for relaxation of airway smooth muscle. Previous research suggests that native Kv7 currents are inhibited following treatment of freshly isolated airway smooth muscle cells with bronchoconstrictor agonists, and in intact airways inhibition of Kv7 channels is sufficient to induce bronchiolar constriction. However, the mechanism by which Kv7 currents are inhibited by bronchoconstrictor agonists has yet to be elucidated. In the present study, native Kv7 currents in cultured human trachealis smooth muscle cells (HTSMCs) were observed to be inhibited upon treatment with histamine; inhibition of Kv7 currents was associated with membrane depolarization and an increase in cytosolic Ca2+([Ca2+]cyt). The latter response was inhibited by verapamil, a blocker of L-type voltage-sensitive Ca2+channels (VSCCs). Protein kinase C (PKC) has been implicated as a mediator of bronchoconstrictor actions, although the targets of PKC are not clearly established. We found that histamine treatment significantly and dose-dependently suppressed currents through overexpressed wild-type human Kv7.5 (hKv7.5) channels in cultured HTSMCs, and this effect was inhibited by the PKC inhibitor Ro-31-8220 (3 µM). The PKC-dependent suppression of hKv7.5 currents corresponded with a PKC-dependent increase in hKv7.5 channel phosphorylation. Knocking down or inhibiting PKCα, or mutating hKv7.5 serine 441 to alanine, abolished the inhibitory effects of histamine on hKv7.5 currents. These findings provide the first evidence linking PKC activation to suppression of Kv7 currents, membrane depolarization, and Ca2+influx via L-type VSCCs as a mechanism for histamine-induced bronchoconstriction.
authors.affiliation: Department of Molecular Pharmacology and Therapeutics, Stritch School of Medicine, Loyola University Chicago, Maywood, Illinois.
authors.forename: Jennifer M
authors.initials: JM
authors.lastname: Haick
authors.affiliation: Department of Molecular Pharmacology and Therapeutics, Stritch School of Medicine, Loyola University Chicago, Maywood, Illinois.
authors.forename: Lioubov I
authors.initials: LI
authors.lastname: Brueggemann
authors.affiliation: Department of Cell & Molecular Physiology, Stritch School of Medicine, Loyola University Chicago, Maywood, Illinois.
authors.forename: Leanne L
authors.initials: LL
authors.lastname: Cribbs
authors.affiliation: Department of Pathology, Stritch School of Medicine, Loyola University Chicago, Maywood, Illinois; and.
authors.forename: Mitchell F
authors.initials: MF
authors.lastname: Denning
authors.affiliation: Department of Thoracic and Cardiovascular Surgery, Stritch School of Medicine, Loyola University Chicago, Maywood, Illinois.
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Schwartz
authors.affiliation: Department of Molecular Pharmacology and Therapeutics, Stritch School of Medicine, Loyola University Chicago, Maywood, Illinois; kbyron@luc.edu.
authors.forename: Kenneth L
authors.initials: KL
authors.lastname: Byron
mesh_terms: D016085:Bronchoconstrictor Agents / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D003600:Cytosol / Q000187:drug effects / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D006632:Histamine / Q000494:pharmacology*; D006801:Humans; D015640:Ion Channel Gating / Q000187:drug effects; D051656:KCNQ Potassium Channels / Q000378:metabolism*; D008564:Membrane Potentials / Q000187:drug effects; D032389:Myocytes, Smooth Muscle / Q000187:drug effects / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D010768:Phosphoserine / Q000378:metabolism; D011493:Protein Kinase C / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014132:Trachea / Q000166:cytology*
chemical_list: D016085:Bronchoconstrictor Agents; D051656:KCNQ Potassium Channels; C412231:KCNQ5 protein, human; D010768:Phosphoserine; D006632:Histamine; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium
keywords: KCNQ voltage-activated potassium channel; airway smooth muscle; bronchoconstrictor signal transduction; protein kinase C