title: Induction of stable ER-plasma-membrane junctions by Kv2.1 potassium channels.
abstract: Junctions between cortical endoplasmic reticulum (cER) and the plasma membrane are a subtle but ubiquitous feature in mammalian cells; however, very little is known about the functions and molecular interactions that are associated with neuronal ER-plasma-membrane junctions. Here, we report that Kv2.1 (also known as KCNB1), the primary delayed-rectifier K(+) channel in the mammalian brain, induces the formation of ER-plasma-membrane junctions. Kv2.1 localizes to dense, cell-surface clusters that contain non-conducting channels, indicating that they have a function that is unrelated to membrane-potential regulation. Accordingly, Kv2.1 clusters function as membrane-trafficking hubs, providing platforms for delivery and retrieval of multiple membrane proteins. Using both total internal reflection fluorescence and electron microscopy we demonstrate that the clustered Kv2.1 plays a direct structural role in the induction of stable ER-plasma-membrane junctions in both transfected HEK 293 cells and cultured hippocampal neurons. Glutamate exposure results in a loss of Kv2.1 clusters in neurons and subsequent retraction of the cER from the plasma membrane. We propose Kv2.1-induced ER-plasma-membrane junctions represent a new macromolecular plasma-membrane complex that is sensitive to excitotoxic insult and functions as a scaffolding site for both membrane trafficking and Ca(2+) signaling.
authors.affiliation: Department of Biomedical Sciences, Colorado State University, Fort Collins, CO 80523, USA.
authors.forename: Philip D
authors.initials: PD
authors.lastname: Fox
authors.affiliation: Department of Biomedical Sciences, Colorado State University, Fort Collins, CO 80523, USA.
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Haberkorn
authors.affiliation: Department of Biomedical Sciences, Colorado State University, Fort Collins, CO 80523, USA.
authors.forename: Elizabeth J
authors.initials: EJ
authors.lastname: Akin
authors.affiliation: School of Biomedical Engineering, Colorado State University, Fort Collins, CO 80523, USA.
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Seel
authors.affiliation: School of Biomedical Engineering, Colorado State University, Fort Collins, CO 80523, USA Department of Electrical and Computer Engineering, Colorado State University, Fort Collins, CO 80523, USA.
authors.forename: Diego
authors.initials: D
authors.lastname: Krapf
authors.affiliation: Department of Biomedical Sciences, Colorado State University, Fort Collins, CO 80523, USA Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO 80523, USA michael.tamkun@colostate.edu.
authors.forename: Michael M
authors.initials: MM
authors.lastname: Tamkun
mesh_terms: D002118:Calcium / Q000378:metabolism; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism*; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D018698:Glutamic Acid / Q000378:metabolism; D057809:HEK293 Cells; D006624:Hippocampus / Q000378:metabolism; D006801:Humans; D008564:Membrane Potentials / Q000502:physiology; D008565:Membrane Proteins / Q000378:metabolism; D009474:Neurons / Q000378:metabolism; D021381:Protein Transport / Q000502:physiology; D051669:Shab Potassium Channels / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology
chemical_list: C496988:KCNB1 protein, human; D008565:Membrane Proteins; D051669:Shab Potassium Channels; D018698:Glutamic Acid; D002118:Calcium
keywords: Ion channels; Membrane contact sites; Sub-surface cisterns