title: Coupling strength between localized Ca(2+) transients and K(+) channels is regulated by protein kinase C.
abstract: Localized Ca(2+) transients resulting from inositol trisphosphate (IP(3))-dependent Ca(2+) release couple to spontaneous transient outward currents (STOCs) in murine colonic myocytes. Confocal microscopy and whole cell patch-clamp techniques were used to investigate coupling between localized Ca(2+) transients and STOCs. Colonic myocytes were loaded with fluo 3. Reduction in external Ca(2+) ([Ca(2+)](o)) reduced localized Ca(2+) transients but increased STOC amplitude and frequency. Simultaneous recordings of Ca(2+) transients and STOCs showed increased coupling strength between Ca(2+) transients and STOCs when [Ca(2+)](o) was reduced. Gd(3+) (10 microM) did not affect Ca(2+) transients but increased STOC amplitude and frequency. Similarly, an inhibitor of Ca(2+) influx, 1-2-(4-methoxyphenyl)-2-[3-(4-methoxyphenyl)propoxy]ethyl-1H-imidazole (SKF-96365), increased STOC amplitude and frequency. A protein kinase C (PKC) inhibitor, GF-109203X, also increased the amplitude and frequency of STOCs but had no effect on Ca(2+) transients. Phorbol 12-myristate 13-acetate (1 microM) reduced STOC amplitude and frequency but did not affect Ca(2+) transients. 4alpha-Phorbol (1 microM) had no effect on STOCs or Ca(2+) transients. Single channel studies indicated that large-conductance Ca(2+)-activated K(+) (BK) channels were inhibited by a Ca(2+)-dependent PKC. In summary 1) Ca(2+) release from IP(3) receptor-operated stores activates Ca(2+)-activated K(+) channels; 2) Ca(2+) influx through nonselective cation channels facilitates activation of PKC; and 3) PKC reduces the Ca(2+) sensitivity of BK channels, reducing the coupling strength between localized Ca(2+) transients and BK channels.
authors.affiliation: Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, Nevada 89557-0046, USA.
authors.forename: O
authors.initials: O
authors.lastname: Bayguinov
authors.forename: B
authors.initials: B
authors.lastname: Hagen
authors.forename: J L
authors.initials: JL
authors.lastname: Kenyon
authors.forename: K M
authors.initials: KM
authors.lastname: Sanders
mesh_terms: D000818:Animals; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000187:drug effects / Q000378:metabolism*; D003106:Colon / Q000166:cytology / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007093:Imidazoles / Q000494:pharmacology; D066298:In Vitro Techniques; D007211:Indoles / Q000494:pharmacology; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism; D008301:Maleimides / Q000494:pharmacology; D051379:Mice; D008807:Mice, Inbred BALB C; D018613:Microscopy, Confocal; D009130:Muscle, Smooth / Q000166:cytology / Q000378:metabolism; D015221:Potassium Channels / Q000187:drug effects / Q000378:metabolism*; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D015290:Second Messenger Systems / Q000187:drug effects / Q000502:physiology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
chemical_list: D002121:Calcium Channel Blockers; D015220:Calcium Channels; D004791:Enzyme Inhibitors; D007093:Imidazoles; D007211:Indoles; D008301:Maleimides; D015221:Potassium Channels; D015544:Inositol 1,4,5-Trisphosphate; D011493:Protein Kinase C; C063159:1-(2-(3-(4-methoxyphenyl)propoxy)-4-methoxyphenylethyl)-1H-imidazole; C070515:bisindolylmaleimide I; D013755:Tetradecanoylphorbol Acetate