title: Immunolocalization of BK channels in hippocampal pyramidal neurons.
abstract: Neurons are highly specialized cells in which the integration and processing of electrical signals critically depends on the precise localization of ion channels. For large-conductance Ca(2+)- activated K(+) (BK) channels, targeting to presynaptic membranes in hippocampal pyramidal cells was reported; however, functional evidence also suggests a somatodendritic localization. Therefore we re-examined the subcellular distribution of BK channels in mouse hippocampus using a panel of independent antibodies in a combined approach of conventional immunocytochemistry on cultured neurons, pre- and postembedding electron microscopy and immunoprecipitation. In cultured murine hippocampal neurons, the colocalization of BK channels with both pre- and postsynaptic marker proteins was observed. Electron microscopy confirmed targeting of BK channels to axonal as well as dendritic membranes of glutamatergic synapses in hippocampus. A postsynaptic localization of BK channels was also supported by the finding that the channel coimmunoprecipitated with PSD95, a protein solely expressed in the postsynaptic compartment. These results thus demonstrate that BK channels reside in both post- and presynaptic compartments of hippocampal pyramidal neurons.
authors.affiliation: Department of Medical Genetics, Molecular and Clinical Pharmacology, Division for Molecular and Cellular Pharmacology, Medical University Innsbruck, Peter-Mayr Strasse 1, 6020 Innsbruck, Austria.
authors.forename: Claudia A
authors.initials: CA
authors.lastname: Sailer
authors.forename: Walter A
authors.initials: WA
authors.lastname: Kaufmann
authors.forename: Michaela
authors.initials: M
authors.lastname: Kogler
authors.forename: Lie
authors.initials: L
authors.lastname: Chen
authors.forename: Ulrike
authors.initials: U
authors.lastname: Sausbier
authors.forename: Ole Petter
authors.initials: OP
authors.lastname: Ottersen
authors.forename: Peter
authors.initials: P
authors.lastname: Ruth
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Shipston
authors.forename: Hans-Günther
authors.initials: HG
authors.lastname: Knaus
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling / Q000502:physiology; D002478:Cells, Cultured; D003712:Dendrites / Q000378:metabolism* / Q000648:ultrastructure; D000076122:Disks Large Homolog 4 Protein; D051528:Guanylate Kinases; D006624:Hippocampus / Q000378:metabolism* / Q000648:ultrastructure; D007150:Immunohistochemistry; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism; D051036:Large-Conductance Calcium-Activated Potassium Channels / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D046529:Microscopy, Electron, Transmission; D017729:Presynaptic Terminals / Q000378:metabolism* / Q000648:ultrastructure; D021122:Protein Subunits / Q000378:metabolism; D017966:Pyramidal Cells / Q000378:metabolism* / Q000648:ultrastructure; D017470:Receptors, Glutamate / Q000378:metabolism; D013570:Synaptic Membranes / Q000378:metabolism* / Q000648:ultrastructure; D009435:Synaptic Transmission / Q000502:physiology
chemical_list: D000076122:Disks Large Homolog 4 Protein; C501447:Dlg4 protein, mouse; D047908:Intracellular Signaling Peptides and Proteins; D051036:Large-Conductance Calcium-Activated Potassium Channels; D008565:Membrane Proteins; D021122:Protein Subunits; D017470:Receptors, Glutamate; D051528:Guanylate Kinases; D002118:Calcium