title: Distribution of high-conductance Ca(2+)-activated K+ channels in rat brain: targeting to axons and nerve terminals.
abstract: Tissue expression and distribution of the high-conductance Ca(2+)-activated K+ channel Slo was investigated in rat brain by immunocytochemistry, in situ hybridization, and radioligand binding using the novel high-affinity (Kd 22 pM) ligand [3H]iberiotoxin-D19C ([3H]IbTX-D19C), which is an analog of the selective maxi-K peptidyl blocker IbTX. A sequence-directed antibody directed against Slo revealed the expression of a 125 kDa polypeptide in rat brain by Western blotting and precipitated the specifically bound [3H]IbTX-D19C in solubilized brain membranes. Slo immunoreactivity was highly concentrated in terminal areas of prominent fiber tracts: the substantia nigra pars reticulata, globus pallidus, olfactory system, interpeduncular nucleus, hippocampal formation including mossy fibers and perforant path terminals, medial forebrain bundle and pyramidal tract, as well as cerebellar Purkinje cells. In situ hybridization indicated high levels of Slo mRNA in the neocortex, olfactory system, habenula, striatum, granule and pyramidal cell layer of the hippocampus, and Purkinje cells. The distribution of Slo protein was confirmed in microdissected brain areas by Western blotting and radioligand-binding studies. The latter studies also established the pharmacological profile of neuronal Slo channels. The expression pattern of Slo is consistent with its targeting into a presynaptic compartment, which implies an important role in neural transmission.
authors.affiliation: Institut für Biochemische Pharmakologie, Innsbruck, Austria.
authors.forename: H G
authors.initials: HG
authors.lastname: Knaus
authors.forename: C
authors.initials: C
authors.lastname: Schwarzer
authors.forename: R O
authors.initials: RO
authors.lastname: Koch
authors.forename: A
authors.initials: A
authors.lastname: Eberhart
authors.forename: G J
authors.initials: GJ
authors.lastname: Kaczorowski
authors.forename: H
authors.initials: H
authors.lastname: Glossmann
authors.forename: F
authors.initials: F
authors.lastname: Wunder
authors.forename: O
authors.initials: O
authors.lastname: Pongs
authors.forename: M L
authors.initials: ML
authors.lastname: Garcia
authors.forename: G
authors.initials: G
authors.lastname: Sperk
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D001369:Axons / Q000737:chemistry*; D001483:Base Sequence; D001667:Binding, Competitive; D015153:Blotting, Western; D001923:Brain Chemistry; D002118:Calcium / Q000502:physiology*; D002451:Cell Compartmentation; D018999:Charybdotoxin / Q000378:metabolism; D017403:In Situ Hybridization; D015640:Ion Channel Gating / Q000502:physiology; D051037:Large-Conductance Calcium-Activated Potassium Channel alpha Subunits; D051036:Large-Conductance Calcium-Activated Potassium Channels; D008297:Male; D008565:Membrane Proteins / Q000032:analysis* / Q000187:drug effects / Q000276:immunology; D008969:Molecular Sequence Data; D009411:Nerve Endings / Q000737:chemistry*; D009419:Nerve Tissue Proteins / Q000032:analysis* / Q000276:immunology; D009928:Organ Specificity; D010446:Peptide Fragments / Q000276:immunology; D010455:Peptides / Q000378:metabolism; D011188:Potassium / Q000378:metabolism*; D015221:Potassium Channels / Q000032:analysis* / Q000187:drug effects / Q000276:immunology; D024681:Potassium Channels, Calcium-Activated; D012333:RNA, Messenger / Q000032:analysis; D011869:Radioligand Assay; D051381:Rats; D017207:Rats, Sprague-Dawley; D011994:Recombinant Proteins / Q000494:pharmacology
chemical_list: D000911:Antibodies, Monoclonal; C494842:Kcnma1 protein, rat; D051037:Large-Conductance Calcium-Activated Potassium Channel alpha Subunits; D051036:Large-Conductance Calcium-Activated Potassium Channels; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D010446:Peptide Fragments; D010455:Peptides; D015221:Potassium Channels; D024681:Potassium Channels, Calcium-Activated; D012333:RNA, Messenger; D011994:Recombinant Proteins; C087375:charybdotoxin receptor; D018999:Charybdotoxin; C064719:iberiotoxin; D011188:Potassium; D002118:Calcium