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. General Significance Protein N- and O-glycosylation can modulate ion channel gating simultaneously. These data also suggest that Nav gating might be altered simply through exposure to different levels of sugar residues that serve as substrates for N- and O-glycosylation. Thus, in disease states that affect sugar substrate levels, the glycosylation process would be impacted, likely resulting in changes in Nav sialylation levels that would lead to modulated channel gating, AP waveforms and conduction.

A recurrent missense variant inSLC9A7causes nonsyndromic X-linked intellectual disability with alteration of Golgi acidification and aberrant glycosylation

“…Within synapses, N-glycosylation of synaptophysin and synaptic vesicle protein 2 is required for optimal synaptic vesicle trafficking (107,108). Likewise, N-glycosylation promotes protein stability, membrane trafficking and/or activity of various neurotransmitter transporters (109)(110)(111)(112)(113)(114) and voltage-gated ion channels (115)(116)(117)(118)(119)(120)(121), which are crucial for membrane excitability and neurotransmission, and is necessary for cellular processes underlying learning and memory (122,123).…”

Decisive structural elements in water and ion permeation through mechanosensitive channels of large conductance: insights from molecular dynamics simulation

“…Mechanosensitive (MS) channels are pervasive membrane proteins in prokaryotic and eukaryotic cell membranes, and their gating function results in some conformational changes to reach the open and closed states in response to mechanical stimuli such as tension, shear, and pressure. 6 These proteins play a pivotal role in physiological processes such as sense of touch, hearing, and regulation of blood pressure as transducers of mechanical stimulations into an electrical signal. [7][8][9][10][11][12] Understanding the nature of mechanotransduction at the atomic level provides a more comprehensive insight into improving therapeutic plans.…”

Cell Surface Sialylated N-Glycan Alterations during Development

“…The number and location of sialylated chains and their attached pore forming or auxiliary subunits change the activity of Na v (9,10). The comparison of N-and O-linked Sia contributions on channel gating is found to be similar (11) but, Sia and polySia have different effects on gating of the Na v (12). Slight changes in channel function may cause several cardiac disorders (13).…”