Immunolocalization of BK channels in hippocampal pyramidal neurons

• Published in: The European journal of neuroscience Vol. 24; no. 2; pp. 442 - 454
• Main Authors: Sailer, Claudia A., Kaufmann, Walter A., Kogler, Michaela, Chen, Lie, Sausbier, Ulrike, Ottersen, Ole Petter, Ruth, Peter, Shipston, Michael J., Knaus, Hans-Günther
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01.07.2006
• Subjects: Animals; Calcium - metabolism; Calcium Signaling - physiology; Cells, Cultured; Dendrites - metabolism; Dendrites - ultrastructure; Disks Large Homolog 4 Protein; electron microscopy; Guanylate Kinases; Hippocampus - metabolism; Hippocampus - ultrastructure; Immunohistochemistry; Intracellular Signaling Peptides and Proteins - metabolism; Large-Conductance Calcium-Activated Potassium Channels - metabolism; localization; Membrane Proteins - metabolism; Mice; Mice, Inbred C57BL; Microscopy, Electron, Transmission; mouse hippocampal culture; potassium channels; Presynaptic Terminals - metabolism; Presynaptic Terminals - ultrastructure; Protein Subunits - metabolism; PSD; Pyramidal Cells - metabolism; Pyramidal Cells - ultrastructure; Receptors, Glutamate - metabolism; Synaptic Membranes - metabolism; Synaptic Membranes - ultrastructure; Synaptic Transmission - physiology
• ISSN: 0953-816X; 1460-9568
• DOI: 10.1111/j.1460-9568.2006.04936.x

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 Ca2+‐ 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.