Andrew R Ednie1, Jean M Harper1, Eric S Bennett2. 1. Department of Molecular Pharmacology and Physiology, University of South Florida Morsani College of Medicine, Tampa, FL 33612, USA. 2. Department of Molecular Pharmacology and Physiology, University of South Florida Morsani College of Medicine, Tampa, FL 33612, USA. Electronic address: esbennet@health.usf.edu.
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.
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.
Authors: Kshama D Chandrasekhar; Anatoli Lvov; Cecile Terrenoire; Grace Y Gao; Robert S Kass; William R Kobertz Journal: J Physiol Date: 2011-06-13 Impact factor: 5.182
Authors: E J Footitt; A Karimova; M Burch; T Yayeh; T Dupré; S Vuillaumier-Barrot; I Chantret; S E H Moore; N Seta; S Grunewald Journal: J Inherit Metab Dis Date: 2009-09-07 Impact factor: 4.982
Authors: Wujood Khayat; Anna Hackett; Marie Shaw; Alina Ilie; Tracy Dudding-Byth; Vera M Kalscheuer; Louise Christie; Mark A Corbett; Jane Juusola; Kathryn L Friend; Brian M Kirmse; Jozef Gecz; Michael Field; John Orlowski Journal: Hum Mol Genet Date: 2019-02-15 Impact factor: 6.150