title: TrkB activation by brain-derived neurotrophic factor inhibits the G protein-gated inward rectifier Kir3 by tyrosine phosphorylation of the channel.
abstract: G protein-activated inwardly rectifying potassium channels (Kir3) are widely expressed throughout the brain, and regulation of their activity modifies neuronal excitability and synaptic transmission. In this study, we show that the neurotrophin brain-derived neurotrophic factor (BDNF), through activation of TrkB receptors, strongly inhibited the basal activity of Kir3. This inhibition was subunit dependent as functional homomeric channels of either Kir3.1 or Kir3.4 were significantly inhibited, whereas homomeric channels composed of Kir3.2 were insensitive. The general tyrosine kinase inhibitors genistein, Gö 6976, and K252a but not the serine/threonine kinase inhibitor staurosporine blocked the BDNF-induced inhibition of the channel. BDNF was also found to directly stimulate channel phosphorylation because Kir3.1 immunoprecipitated from BDNF-stimulated cells showed enhanced labeling by anti-phosphotyrosine-specific antibodies. The BDNF effect required specific tyrosine residues in the amino terminus of Kir3.1 and Kir3.4 channels. Mutations of either Tyr-12, Tyr-67, or both in Kir3.1 or mutation of either Tyr-32, Tyr-53, or both of Kir3. 4 channels to phenylalanine significantly blocked the BDNF-induced inhibition. The insensitive Kir3.2 was made sensitive to BDNF by adding a tyrosine (D41Y) and a lysine (P32K) upstream to generate a phosphorylation site motif analogous to that present in Kir3.4. These results suggest that neurotrophin activation of TrkB receptors may physiologically control neuronal excitability by direct tyrosine phosphorylation of the Kir3.1 and Kir3.4 subunits of G protein-gated inwardly rectifying potassium channels.
authors.affiliation: Department of Pharmacology and Anesthesiology, University of Washington, Seattle 98195, USA.
authors.forename: S L
authors.initials: SL
authors.lastname: Rogalski
authors.forename: S M
authors.initials: SM
authors.lastname: Appleyard
authors.forename: A
authors.initials: A
authors.lastname: Pattillo
authors.forename: G W
authors.initials: GW
authors.lastname: Terman
authors.forename: C
authors.initials: C
authors.lastname: Chavkin
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D019208:Brain-Derived Neurotrophic Factor / Q000494:pharmacology*; D002227:Carbazoles / Q000494:pharmacology; D018076:DNA, Complementary / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004594:Electrophysiology; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D051676:G Protein-Coupled Inwardly-Rectifying Potassium Channels; D019204:GTP-Binding Proteins / Q000378:metabolism*; D019833:Genistein / Q000494:pharmacology; D026121:Indole Alkaloids; D007211:Indoles / Q000494:pharmacology; D008239:Lysine / Q000737:chemistry; D008954:Models, Biological; D008969:Molecular Sequence Data; D009154:Mutation; D009865:Oocytes / Q000187:drug effects / Q000378:metabolism; D010766:Phosphorylation; D015221:Potassium Channels / Q000737:chemistry / Q000378:metabolism*; D024661:Potassium Channels, Inwardly Rectifying; D011233:Precipitin Tests; D012333:RNA, Messenger / Q000378:metabolism; D020813:Receptor, trkB / Q000378:metabolism*; D019311:Staurosporine / Q000494:pharmacology; D014443:Tyrosine / Q000378:metabolism*; D014981:Xenopus
chemical_list: D019208:Brain-Derived Neurotrophic Factor; D002227:Carbazoles; D018076:DNA, Complementary; D004791:Enzyme Inhibitors; D051676:G Protein-Coupled Inwardly-Rectifying Potassium Channels; D026121:Indole Alkaloids; D007211:Indoles; D015221:Potassium Channels; D024661:Potassium Channels, Inwardly Rectifying; D012333:RNA, Messenger; C081021:Go 6976; D014443:Tyrosine; C049985:staurosporine aglycone; D019833:Genistein; D020813:Receptor, trkB; D019204:GTP-Binding Proteins; D019311:Staurosporine; D008239:Lysine