title: Acceleration of K+ channel inactivation by MEK inhibitor U0126.
abstract: Voltage-dependent (Kv)4.2-encoded A-type K+ channels play an important role in controlling neuronal excitability and are subject to modulation by various protein kinases, including ERK. In studies of ERK modulation, the organic compound U0126 is often used to suppress the activity of MEK, which is a kinase immediately upstream from ERK. We have observed that the inactivation time constant of heterologously expressed Kv4.2 channels was accelerated by U0126 at 1-20 microM. This effect, however, was not Kv4 family specific, because U0126 also converted noninactivating K+ currents mediated by Kv1.1 subunits into transient ones. To determine whether U0126 exerted these effects through kinase inhibition, we tested U0125, a derivative of U0126 that is less potent in MEK inhibition. At the same concentrations, U0125 had effects similar to those of U0126 on channel inactivation. Finally, we expressed a mutant form of Kv4.2 in which three identified ERK phosphorylation sites (T602, T607, and S616) were replaced with alanines. The inactivation of K+ currents mediated by this mutant was still accelerated by U0126. Our data favor the conclusion that the increase in the rate of channel inactivation by U0126 is likely to be independent of protein kinase inhibition and instead represents a direct action on channel gating.
authors.affiliation: Dept. of Neuroscience, Univ. of Minnesota, 6-145 Jackson Hall, 321 Church St., Minneapolis, MN 55455, USA. yuanx033@umn.edu
authors.forename: Li-Lian
authors.initials: LL
authors.lastname: Yuan
authors.forename: Xixi
authors.initials: X
authors.lastname: Chen
authors.forename: Kumud
authors.initials: K
authors.lastname: Kunjilwar
authors.forename: Paul
authors.initials: P
authors.lastname: Pfaffinger
authors.forename: Daniel
authors.initials: D
authors.lastname: Johnston
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002070:Butadienes / Q000494:pharmacology*; D016466:CHO Cells; D006224:Cricetinae; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D015640:Ion Channel Gating / Q000187:drug effects*; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000502:physiology; D020929:Mitogen-Activated Protein Kinase Kinases / Q000037:antagonists & inhibitors*; D008969:Molecular Sequence Data; D009570:Nitriles / Q000494:pharmacology*; D011188:Potassium / Q000378:metabolism; D021122:Protein Subunits / Q000235:genetics / Q000378:metabolism; D051381:Rats; D051672:Shal Potassium Channels / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D014162:Transfection
chemical_list: D002070:Butadienes; D004791:Enzyme Inhibitors; D009570:Nitriles; D021122:Protein Subunits; D051672:Shal Potassium Channels; C113580:U 0126; D020929:Mitogen-Activated Protein Kinase Kinases; D011188:Potassium