title: Kv3.3 immunoreactivity in the vestibular nuclear complex of the rat with focus on the medial vestibular nucleus: targeting of Kv3.3 neurones by terminals positive for vesicular glutamate transporter 1.
abstract: Kv3 voltage-gated K(+) channels are important in shaping neuronal excitability and are abundant in the CNS, with each Kv3 gene exhibiting a unique expression pattern. Mice lacking the gene encoding for the Kv3.3 subunit exhibit motor deficits. Furthermore, mutations in this gene have been linked to the human disease spinocerebellar ataxia 13, associated with cerebellar and extra-cerebellar symptoms such as imbalance and nystagmus. Kv subunit localisation is important in defining their functional roles and thus, we investigated the distribution of Kv3.3-immunoreactivity in the vestibular nuclear complex of rats with particular focus on the medial vestibular nucleus (MVN). Kv3.3-immunoreactivity was widespread in the vestibular nuclei and was detected in somata, dendrites and synaptic terminals. Kv3.3-immunoreactivity was observed in distinct neuronal populations and dual labelling with the neuronal marker NeuN revealed 28.5+/-1.9% of NeuN labelled MVN neurones were Kv3.3-positive. Kv3.3-immunoreactivity co-localised presynaptically with the synaptic vesicle marker SV2, parvalbumin, the vesicular glutamate transporter VGluT2 and the glycine transporter GlyT2. VGluT1 terminals were scarce within the MVN (2.5+/-1.1 per 50 microm(2)) and co-localisation was not observed. However, 85.4+/-9.4% of VGluT1 terminals targeted and enclosed Kv3.3-immunoreactive somata. Presynaptic Kv3.3 co-localisation with the GABAergic marker GAD67 was also not observed. Cytoplasmic GlyT2 labelling was observed in a subset of Kv3.3-positive neurones. Electron microscopy confirmed a pre- and post-synaptic distribution of the Kv3.3 protein. This study provides evidence supporting a role for Kv3.3 subunits in vestibular processing by regulating neuronal excitability pre- and post-synaptically.
authors.affiliation: School of Healthcare, University of Leeds, Leeds, UK. r.e.brooke@leeds.ac.uk
authors.forename: Ruth Elizabeth
authors.initials: RE
authors.lastname: Brooke
authors.forename: Laura
authors.initials: L
authors.lastname: Corns
authors.forename: Ian James
authors.initials: IJ
authors.lastname: Edwards
authors.forename: Jim
authors.initials: J
authors.lastname: Deuchars
mesh_terms: D000818:Animals; D034961:Antigens, Nuclear / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism / Q000648:ultrastructure; D003712:Dendrites / Q000378:metabolism / Q000648:ultrastructure; D005968:Glutamate Decarboxylase / Q000378:metabolism; D050487:Glycine Plasma Membrane Transport Proteins / Q000378:metabolism; D007150:Immunohistochemistry; D008562:Membrane Glycoproteins / Q000378:metabolism; D018613:Microscopy, Confocal; D008854:Microscopy, Electron; D009419:Nerve Tissue Proteins / Q000378:metabolism; D009474:Neurons / Q000378:metabolism* / Q000648:ultrastructure; D010320:Parvalbumins / Q000378:metabolism; D017729:Presynaptic Terminals / Q000378:metabolism / Q000648:ultrastructure; D051381:Rats; D017208:Rats, Wistar; D051670:Shaw Potassium Channels / Q000378:metabolism*; D013569:Synapses / Q000378:metabolism / Q000648:ultrastructure; D050598:Vesicular Glutamate Transport Protein 1 / Q000378:metabolism*; D050599:Vesicular Glutamate Transport Protein 2 / Q000378:metabolism; D014726:Vestibular Nuclei / Q000378:metabolism*
chemical_list: D034961:Antigens, Nuclear; D050487:Glycine Plasma Membrane Transport Proteins; C484184:Kcnc3 protein, rat; D008562:Membrane Glycoproteins; D009419:Nerve Tissue Proteins; D010320:Parvalbumins; C546339:Rbfox3 protein, rat; D051670:Shaw Potassium Channels; C493475:Slc17a6 protein, rat; C493466:Slc17a7 protein, rat; C493269:Slc6a5 protein, rat; C489618:Sv2a protein, rat; D050598:Vesicular Glutamate Transport Protein 1; D050599:Vesicular Glutamate Transport Protein 2; D005968:Glutamate Decarboxylase; C402565:glutamate decarboxylase 1