title: Sialic acids attached to N- and O-glycans within the Nav1.4 D1S5-S6 linker contribute to channel gating.
abstract: BACKGROUND
  Voltage-gated Na+ channels (Nav) are responsible for the initiation and conduction of neuronal and muscle action potentials. Nav gating can be altered by sialic acids attached to channel N-glycans, typically through isoform-specific electrostatic mechanisms.
  
  
  METHODS
  Using two sets of Chinese Hamster Ovary cell lines with varying abilities to glycosylate glycoproteins, we show for the first time that sialic acids attached to O-glycans and N-glycans within the Nav1.4 D1S5-S6 linker modulate Nav gating.
  
  
  RESULTS
  All measured steady-state and kinetic parameters were shifted to more depolarized potentials under conditions of essentially no sialylation. When sialylation of only N-glycans or of only O-glycans was prevented, the observed voltage-dependent parameter values were intermediate between those observed under full versus no sialylation. Immunoblot gel shift analyses support the biophysical data.
  
  
  CONCLUSIONS
  The data indicate that sialic acids attached to both N- and O-glycans residing within the Nav1.4 D1S5-S6 linker modulate channel gating through electrostatic mechanisms, with the relative contribution of sialic acids attached to N- versus O-glycans on channel gating being similar.
  
  
  CONCLUSIONS
  Protein N- and O-glycosylation can modulate ion channel gating simultaneously. These data also suggest that environmental, metabolic, and/or congenital changes in glycosylation that impact sugar substrate levels, could lead, potentially, to changes in Nav sialylation and gating that would modulate AP waveforms and conduction.
authors.affiliation: Department of Molecular Pharmacology and Physiology, University of South Florida Morsani College of Medicine, Tampa, FL 33612, USA.
authors.forename: Andrew R
authors.initials: AR
authors.lastname: Ednie
authors.affiliation: Department of Molecular Pharmacology and Physiology, University of South Florida Morsani College of Medicine, Tampa, FL 33612, USA.
authors.forename: Jean M
authors.initials: JM
authors.lastname: Harper
authors.affiliation: Department of Molecular Pharmacology and Physiology, University of South Florida Morsani College of Medicine, Tampa, FL 33612, USA. Electronic address: esbennet@health.usf.edu.
authors.forename: Eric S
authors.initials: ES
authors.lastname: Bennett
mesh_terms: D000818:Animals; D016466:CHO Cells; D006224:Cricetinae; D003412:Cricetulus; D006023:Glycoproteins / Q000235:genetics / Q000378:metabolism*; D006031:Glycosylation; D015640:Ion Channel Gating / Q000502:physiology*; D062553:NAV1.4 Voltage-Gated Sodium Channel / Q000235:genetics / Q000378:metabolism*; D012794:Sialic Acids / Q000235:genetics / Q000378:metabolism*
chemical_list: D006023:Glycoproteins; D062553:NAV1.4 Voltage-Gated Sodium Channel; C106251:SCN4A protein, human; D012794:Sialic Acids
keywords: Ion channel gating; N-glycosylation; Neuraminic acid; O-glycosylation; Sialic acids; Voltage-gated Na(+) channels