title: Frequency-dependent inactivation of mammalian A-type K+ channel KV1.4 regulated by Ca2+/calmodulin-dependent protein kinase.
abstract: Ca2+/calmodulin dependent protein kinase (CaMKII) and protein phosphatase 2B (calcineurin) are key enzymes in the regulation of synaptic strength, controlling the phosphorylation status of pre- and postsynaptic target proteins. Here, we show that the inactivation gating of the Shaker-related fast-inactivating KV channel, Kv1.4 is controlled by CaMKII and the calcineurin/inhibitor-1 protein phosphatase cascade. CaMKII phosphorylation of an amino-terminal residue of KV1.4 leads to slowing of inactivation gating and accelerated recovery from N-type inactivated states. In contrast, dephosphorylation of this residue induces a fast inactivating mode of KV1.4 with time constants of inactivation 5 to 10 times faster compared with the CaMKII-phosphorylated form. Dephosphorylated KV1.4 channels also display slowed and partial recovery from inactivation with increased trapping of KV1.4 channels in long-absorbing C-type inactivated states. In consequence, dephosphorylated KV1.4 displays a markedly increased tendency to undergo cumulative inactivation during repetitive stimulation. The balance between phosphorylated and dephosphorylated KV1.4 channels is regulated by changes in intracellular Ca2+ concentration rendering KV1.4 inactivation gating Ca2+-sensitive. The reciprocal CaMKII and calcineurin regulation of cumulative inactivation of presynaptic KV1.4 may provide a novel mechanism to regulate the critical frequency for presynaptic spike broadening and induction of synaptic plasticity.
authors.affiliation: Zentrum für Molekulare Neurobiologie, Martinistrasse 52, D-20246 Hamburg, Germany.
authors.forename: J
authors.initials: J
authors.lastname: Roeper
authors.forename: C
authors.initials: C
authors.lastname: Lorra
authors.forename: O
authors.initials: O
authors.lastname: Pongs
mesh_terms: D000818:Animals; D019703:Calcineurin; D002118:Calcium / Q000502:physiology; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D002148:Calmodulin-Binding Proteins / Q000378:metabolism; D002460:Cell Line / Q000737:chemistry / Q000502:physiology; D015971:Gene Expression Regulation, Enzymologic / Q000502:physiology; D006801:Humans; D015640:Ion Channel Gating / Q000502:physiology*; D007668:Kidney / Q000166:cytology; D007700:Kinetics; D008322:Mammals; D016297:Mutagenesis, Site-Directed / Q000502:physiology; D018408:Patch-Clamp Techniques; D010749:Phosphoprotein Phosphatases / Q000378:metabolism; D010766:Phosphorylation; D011188:Potassium / Q000378:metabolism; D015221:Potassium Channels / Q000235:genetics* / Q000378:metabolism; D051637:Shaker Superfamily of Potassium Channels; D014162:Transfection
chemical_list: D002148:Calmodulin-Binding Proteins; D015221:Potassium Channels; D051637:Shaker Superfamily of Potassium Channels; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D019703:Calcineurin; D010749:Phosphoprotein Phosphatases; D011188:Potassium; D002118:Calcium