Sialic acids attached to N- and O-glycans within the Nav1.4 D1S5-S6 linker contribute to channel gating

Biochim Biophys Acta. 2015 Feb;1850(2):307-17. doi: 10.1016/j.bbagen.2014.10.027. Epub 2014 Oct 30.

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.

General significance: 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.

Keywords: Ion channel gating; N-glycosylation; Neuraminic acid; O-glycosylation; Sialic acids; Voltage-gated Na(+) channels.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • CHO Cells
  • Cricetinae
  • Cricetulus
  • Glycoproteins / genetics
  • Glycoproteins / metabolism*
  • Glycosylation
  • Ion Channel Gating / physiology*
  • NAV1.4 Voltage-Gated Sodium Channel / genetics
  • NAV1.4 Voltage-Gated Sodium Channel / metabolism*
  • Sialic Acids / genetics
  • Sialic Acids / metabolism*

Substances

  • Glycoproteins
  • NAV1.4 Voltage-Gated Sodium Channel
  • SCN4A protein, human
  • Sialic Acids