title: Glucose induces anion conductance and cytosol-to-membrane transposition of ICln in INS-1E rat insulinoma cells.
abstract: The metabolic coupling of insulin secretion by pancreatic beta cells is mediated by membrane depolarization due to increased glucose-driven ATP production and closure of K(ATP) channels. Alternative pathways may involve the activation of anion channels by cell swelling upon glucose uptake. In INS-1E insulinoma cells superfusion with an isotonic solution containing 20 mM glucose or a 30% hypotonic solution leads to the activation of a chloride conductance with biophysical and pharmacological properties of anion currents activated in many other cell types during regulatory volume decrease (RVD), i.e. outward rectification, inactivation at positive membrane potentials and block by anion channel inhibitors like NPPB, DIDS, 4-hydroxytamoxifen and extracellular ATP. The current is not inhibited by tolbutamide and remains activated for at least 10 min when reducing the extracellular glucose concentration from 20 mM to 5 mM, but inactivates back to control levels when cells are exposed to a 20% hypertonic extracellular solution containing 20 mM glucose. This chloride current can likewise be induced by 20 mM 3-Omethylglucose, which is taken up but not metabolized by the cells, suggesting that cellular sugar uptake is involved in current activation. Fluorescence resonance energy transfer (FRET) experiments show that chloride current activation by 20 mM glucose and glucose-induced cell swelling are accompanied by a significant, transient redistribution of the membrane associated fraction of ICln, a multifunctional 'connector hub' protein involved in cell volume regulation and generation of RVD currents.
authors.affiliation: Institute of Physiology and Pathophysiology, Paracelsus Private Medical University, Salzburg.
authors.forename: Martin
authors.initials: M
authors.lastname: Jakab
authors.forename: Michael
authors.initials: M
authors.lastname: Grundbichler
authors.forename: Julius
authors.initials: J
authors.lastname: Benicky
authors.forename: Andrea
authors.initials: A
authors.lastname: Ravasio
authors.forename: Sabine
authors.initials: S
authors.lastname: Chwatal
authors.forename: Sabine
authors.initials: S
authors.lastname: Schmidt
authors.forename: Vladimir
authors.initials: V
authors.lastname: Strbak
authors.forename: Johannes
authors.initials: J
authors.lastname: Fürst
authors.forename: Markus
authors.initials: M
authors.lastname: Paulmichl
authors.forename: Markus
authors.initials: M
authors.lastname: Ritter
mesh_terms: D019325:3-O-Methylglucose / Q000494:pharmacology; D000818:Animals; D000838:Anions / Q000378:metabolism*; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000378:metabolism*; D003600:Cytosol / Q000378:metabolism*; D031541:Fluorescence Resonance Energy Transfer / Q000379:methods; D005947:Glucose / Q000494:pharmacology*; D006982:Hypertonic Solutions / Q000494:pharmacology; D007004:Hypoglycemic Agents / Q000494:pharmacology; D007038:Hypotonic Solutions / Q000494:pharmacology; D007340:Insulinoma / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology; D007473:Ion Channels / Q000378:metabolism*; D008564:Membrane Potentials / Q000187:drug effects; D018408:Patch-Clamp Techniques / Q000379:methods; D021381:Protein Transport / Q000187:drug effects; D051381:Rats; D014044:Tolbutamide / Q000494:pharmacology
chemical_list: D000838:Anions; C498729:Clns1a protein, rat; D006982:Hypertonic Solutions; D007004:Hypoglycemic Agents; D007038:Hypotonic Solutions; D007473:Ion Channels; D019325:3-O-Methylglucose; D014044:Tolbutamide; D005947:Glucose