title: Nav1.5 channels can reach the plasma membrane through distinct N-glycosylation states.
abstract: BACKGROUND
  Like many voltage-gated sodium channels, the cardiac isoform Nav1.5 is well known as a glycoprotein which necessarily undergoes N-glycosylation processing during its transit to the plasma membrane. In some cardiac disorders, especially the Brugada syndrome (BrS), mutations in Nav1.5 encoding gene lead to intracellular retention and consequently trafficking defect of these proteins. We used two BrS mutants as tools to clarify both Nav1.5 glycosylation states and associated secretory behaviors.
  
  
  METHODS
  Patch-clamp recordings and surface biotinylation assays of HEK293T cells expressing wild-type (WT) and/or mutant Nav1.5 proteins were performed to assess the impact of mutant co-expression on the membrane activity and localization of WT channels. Enzymatic deglycosylation assays and brefeldin A (BFA) treatments were also employed to further characterize recombinant and native Nav1.5 maturation.
  
  
  RESULTS
  The present data demonstrate that Nav1.5 channels mainly exist as two differentially glycosylated forms. We reveal that dominant negative effects induced by BrS mutants upon WT channel current result from the abnormal surface expression of the fully-glycosylated forms exclusively. Furthermore, we show that core-glycosylated channels can be found at the surface membrane of BFA-treated or untreated cells, but obviously without generating any sodium current.
  
  
  CONCLUSIONS
  Our findings provide evidence that native and recombinant Nav1.5 subunits are expressed as two distinct matured forms. Fully-glycosylated state of Nav1.5 seems to determine its functionality whereas core-glycosylated forms might be transported to the plasma membrane through an unconventional Golgi-independent secretory route.
  
  
  CONCLUSIONS
  This work highlights that N-linked glycosylation processing would be critical for Nav1.5 membrane trafficking and function.
authors.affiliation: Laboratoire Signalisation et Transports Ioniques Membranaires (STIM), ERL CNRS 7368, Université de Poitiers, Pôle Biologie Santé, Bâtiment B36, 1 rue Georges Bonnet, TSA 51106, 86073 Poitiers Cedex 9, France.
authors.forename: Aurélie
authors.initials: A
authors.lastname: Mercier
authors.affiliation: Laboratoire Signalisation et Transports Ioniques Membranaires (STIM), ERL CNRS 7368, Université de Poitiers, Pôle Biologie Santé, Bâtiment B36, 1 rue Georges Bonnet, TSA 51106, 86073 Poitiers Cedex 9, France.
authors.forename: Romain
authors.initials: R
authors.lastname: Clément
authors.affiliation: Laboratoire Signalisation et Transports Ioniques Membranaires (STIM), ERL CNRS 7368, Université de Poitiers, Pôle Biologie Santé, Bâtiment B36, 1 rue Georges Bonnet, TSA 51106, 86073 Poitiers Cedex 9, France; CHU de Poitiers, 1 rue de la Milétrie, 86021 Poitiers CEDEX, France.
authors.forename: Thomas
authors.initials: T
authors.lastname: Harnois
authors.affiliation: Laboratoire Signalisation et Transports Ioniques Membranaires (STIM), ERL CNRS 7368, Université de Poitiers, Pôle Biologie Santé, Bâtiment B36, 1 rue Georges Bonnet, TSA 51106, 86073 Poitiers Cedex 9, France; CHU de Poitiers, 1 rue de la Milétrie, 86021 Poitiers CEDEX, France.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Bourmeyster
authors.affiliation: Laboratoire Signalisation et Transports Ioniques Membranaires (STIM), ERL CNRS 7368, Université de Poitiers, Pôle Biologie Santé, Bâtiment B36, 1 rue Georges Bonnet, TSA 51106, 86073 Poitiers Cedex 9, France.
authors.forename: Patrick
authors.initials: P
authors.lastname: Bois
authors.affiliation: Laboratoire Signalisation et Transports Ioniques Membranaires (STIM), ERL CNRS 7368, Université de Poitiers, Pôle Biologie Santé, Bâtiment B36, 1 rue Georges Bonnet, TSA 51106, 86073 Poitiers Cedex 9, France. Electronic address: aurelien.chatelier@univ-poitiers.fr.
authors.forename: Aurélien
authors.initials: A
authors.lastname: Chatelier
mesh_terms: D020126:Brefeldin A / Q000494:pharmacology; D002462:Cell Membrane / Q000378:metabolism*; D006031:Glycosylation; D057809:HEK293 Cells; D006801:Humans; D008564:Membrane Potentials; D009154:Mutation; D062554:NAV1.5 Voltage-Gated Sodium Channel / Q000235:genetics / Q000378:metabolism*; D010641:Phenotype; D011499:Protein Processing, Post-Translational; D021381:Protein Transport / Q000187:drug effects; D014162:Transfection
chemical_list: D062554:NAV1.5 Voltage-Gated Sodium Channel; C568320:SCN5A protein, human; D020126:Brefeldin A
keywords: Brugada syndrome; N-glycosylation; Na(v)1.5; Negative dominance; Secretory pathway; Voltage-gated sodium channel