title: Distinct Cell- and Layer-Specific Expression Patterns and Independent Regulation of Kv2 Channel Subtypes in Cortical Pyramidal Neurons.
abstract: The Kv2 family of voltage-gated potassium channel α subunits, comprising Kv2.1 and Kv2.2, mediate the bulk of the neuronal delayed rectifier K(+) current in many mammalian central neurons. Kv2.1 exhibits robust expression across many neuron types and is unique in its conditional role in modulating intrinsic excitability through changes in its phosphorylation state, which affect Kv2.1 expression, localization, and function. Much less is known of the highly related Kv2.2 subunit, especially in forebrain neurons. Here, through combined use of cortical layer markers and transgenic mouse lines, we show that Kv2.1 and Kv2.2 are localized to functionally distinct cortical cell types. Kv2.1 expression is consistently high throughout all cortical layers, especially in layer (L) 5b pyramidal neurons, whereas Kv2.2 expression is primarily limited to neurons in L2 and L5a. In addition, L4 of primary somatosensory cortex is strikingly devoid of Kv2.2 immunolabeling. The restricted pattern of Kv2.2 expression persists in Kv2.1-KO mice, suggesting distinct cell- and layer-specific functions for these two highly related Kv2 subunits. Analyses of endogenous Kv2.2 in cortical neurons in situ and recombinant Kv2.2 expressed in heterologous cells reveal that Kv2.2 is largely refractory to stimuli that trigger robust, phosphorylation-dependent changes in Kv2.1 clustering and function. Immunocytochemistry and voltage-clamp recordings from outside-out macropatches reveal distinct cellular expression patterns for Kv2.1 and Kv2.2 in intratelencephalic and pyramidal tract neurons of L5, indicating circuit-specific requirements for these Kv2 paralogs. Together, these results support distinct roles for these two Kv2 channel family members in mammalian cortex.
  
  
  CONCLUSIONS
  Neurons within the neocortex are arranged in a laminar architecture and contribute to the input, processing, and/or output of sensory and motor signals in a cell- and layer-specific manner. Neurons of different cortical layers express diverse populations of ion channels and possess distinct intrinsic membrane properties. Here, we show that the Kv2 family members Kv2.1 and Kv2.2 are expressed in distinct cortical layers and pyramidal cell types associated with specific corticostriatal pathways. We find that Kv2.1 and Kv2.2 exhibit distinct responses to acute phosphorylation-dependent regulation in brain neurons in situ and in heterologous cells in vitro. These results identify a molecular mechanism that contributes to heterogeneity in cortical neuron ion channel function and regulation.
authors.affiliation: Department of Neurobiology, Physiology and Behavior and.
authors.forename: Hannah I
authors.identifier: http://orcid.org/0000-0002-5846-5885
authors.initials: HI
authors.lastname: Bishop
authors.affiliation: Department of Anatomy and Neurobiology, University of Tennessee Health Science Center, Memphis, Tennessee 38163.
authors.forename: Dongxu
authors.initials: D
authors.lastname: Guan
authors.affiliation: Department of Biomedical Sciences, Laboratory for Molecular Biophysics, Physiology, and Pharmacology, University of Antwerp, 2610 Antwerp, Belgium.
authors.forename: Elke
authors.initials: E
authors.lastname: Bocksteins
authors.affiliation: Center for Neuroscience, University of California, Davis, California 95616.
authors.forename: Laxmi Kumar
authors.initials: LK
authors.lastname: Parajuli
authors.affiliation: Center for Neuroscience, University of California, Davis, California 95616.
authors.forename: Karl D
authors.initials: KD
authors.lastname: Murray
authors.affiliation: Department of Neurobiology, Physiology and Behavior and.
authors.forename: Melanie M
authors.initials: MM
authors.lastname: Cobb
authors.affiliation: Graduate School of Brain Science, Doshisha University, Kyoto 619-0225, Japan, and.
authors.forename: Hiroaki
authors.identifier: http://orcid.org/0000-0001-5892-1804
authors.initials: H
authors.lastname: Misonou
authors.affiliation: Department of Neurobiology, Physiology and Behavior and Center for Neuroscience, University of California, Davis, California 95616.
authors.forename: Karen
authors.initials: K
authors.lastname: Zito
authors.affiliation: Department of Anatomy and Neurobiology, University of Tennessee Health Science Center, Memphis, Tennessee 38163.
authors.forename: Robert C
authors.initials: RC
authors.lastname: Foehring
authors.affiliation: Department of Neurobiology, Physiology and Behavior and Department of Physiology and Membrane Biology, University of California Davis School of Medicine, Davis, California 95616 jtrimmer@ucdavis.edu.
authors.forename: James S
authors.identifier: http://orcid.org/0000-0002-6117-3912
authors.initials: JS
authors.lastname: Trimmer
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D005786:Gene Expression Regulation; D057809:HEK293 Cells; D006801:Humans; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D019579:Neocortex / Q000166:cytology / Q000378:metabolism*; D009474:Neurons / Q000378:metabolism*; D009924:Organ Culture Techniques; D017966:Pyramidal Cells / Q000166:cytology / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D051669:Shab Potassium Channels / Q000096:biosynthesis*
chemical_list: D051669:Shab Potassium Channels
keywords: electrophysiology; immunohistochemistry; localization; modulation; neocortex; network