title: Human CLC-K Channels Require Palmitoylation of Their Accessory Subunit Barttin to Be Functional.
abstract: CLC-K/barttin chloride channels are essential for NaCl re-absorption in Henle's loop and for potassium secretion by the stria vascularis in the inner ear. Here, we studied the posttranslational modification of such channels by palmitoylation of their accessory subunit barttin. We found that barttin is palmitoylated in vivo and in vitro and identified two conserved cysteine residues at positions 54 and 56 as palmitoylation sites. Point mutations at these two residues reduce the macroscopic current amplitudes in cells expressing CLC-K/barttin channels proportionally to the relative reduction in palmitoylated barttin. CLC-K/barttin expression, plasma membrane insertion, and single channel properties remain unaffected, indicating that these mutations decrease the number of active channels. R8W and G47R, two naturally occurring barttin mutations identified in patients with Bartter syndrome type IV, reduce barttin palmitoylation and CLC-K/barttin channel activity. Palmitoylation of the accessory subunit barttin might thus play a role in chloride channel dysfunction in certain variants of Bartter syndrome. We did not observe pronounced alteration of barttin palmitoylation upon increased salt and water intake or water deprivation, indicating that this posttranslational modification does not contribute to long term adaptation to variable water intake. Our results identify barttin palmitoylation as a novel posttranslational modification of CLC-K/barttin chloride channels.
authors.affiliation: From the Institut für Neurophysiologie, Medizinische Hochschule Hannover, 30625 Hannover, Germany.
authors.forename: Kim Vanessa
authors.initials: KV
authors.lastname: Steinke
authors.affiliation: From the Institut für Neurophysiologie, Medizinische Hochschule Hannover, 30625 Hannover, Germany.
authors.forename: Nataliya
authors.initials: N
authors.lastname: Gorinski
authors.affiliation: From the Institut für Neurophysiologie, Medizinische Hochschule Hannover, 30625 Hannover, Germany, Institute of Complex Systems, Zelluläre Biophysik (ICS-4), FZ Jülich, 52428 Jülich, Germany, and.
authors.forename: Daniel
authors.initials: D
authors.lastname: Wojciechowski
authors.affiliation: Laboratory for Experimental Nephrology, Division of Nephrology, University Hospital Dresden, 01307 Dresden Germany.
authors.forename: Vladimir
authors.initials: V
authors.lastname: Todorov
authors.affiliation: From the Institut für Neurophysiologie, Medizinische Hochschule Hannover, 30625 Hannover, Germany.
authors.forename: Daria
authors.initials: D
authors.lastname: Guseva
authors.affiliation: From the Institut für Neurophysiologie, Medizinische Hochschule Hannover, 30625 Hannover, Germany.
authors.forename: Evgeni
authors.initials: E
authors.lastname: Ponimaskin
authors.affiliation: Institute of Complex Systems, Zelluläre Biophysik (ICS-4), FZ Jülich, 52428 Jülich, Germany, and c.fahlke@fz-juelich.de.
authors.forename: Christoph
authors.initials: C
authors.lastname: Fahlke
authors.affiliation: From the Institut für Neurophysiologie, Medizinische Hochschule Hannover, 30625 Hannover, Germany, fischer.martin@mh-hannover.de.
authors.forename: Martin
authors.initials: M
authors.lastname: Fischer
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000818:Animals; D001477:Bartter Syndrome / Q000235:genetics / Q000378:metabolism; D018118:Chloride Channels / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D003545:Cysteine / Q000737:chemistry; D004285:Dogs; D057809:HEK293 Cells; D006319:Hearing Loss, Sensorineural / Q000235:genetics / Q000378:metabolism; D006801:Humans; D054878:Lipoylation; D061985:Madin Darby Canine Kidney Cells; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D050505:Mutant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017354:Point Mutation; D021122:Protein Subunits; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid
chemical_list: C440005:BSND protein, human; C489932:CLCNKA protein, human; C412733:CLCNKB protein, human; D018118:Chloride Channels; D050505:Mutant Proteins; D021122:Protein Subunits; D011994:Recombinant Proteins; D003545:Cysteine
keywords: barttin; chloride channel; electrophysiology; gating; intracellular trafficking; post-translational modification (PTM); protein palmitoylation; renal physiology