Abstract
The voltage-gated sodium channel Nav1.5 initiates the cardiac action potential. Germline mutations that disrupt Nav1.5 activity predispose affected individuals to inherited cardiopathologies. Some of these Nav1.5 mutations alter amino acids in extracellular turret domains DII and DIII. Yet the mechanism is unclear. In the rat Nav1.5 structure determined by cryogenic electron microscopy, the wild-type residues corresponding to these mutants form a complex salt-bridge between the DII and DIII turret interface. Furthermore, adjacent aromatic residues form cation-π interactions with the complex salt-bridge. Here, we examine this region using site-directed mutagenesis, electrophysiology and in silico modeling. We confirm functional roles for the salt-bridges and the aromatic residues. We show that their disruption perturbs the geometry of both the DEKA selectivity ring and the inner pore vestibule that are crucial for sodium ion permeability. Our findings provide insights into a class of pathological mutations occurring not only in Nav1.5 but also in other sodium channel isoforms too. Our work illustrates how the sodium channel structures now being reported can be used to formulate and guide novel functional hypotheses.
Competing Interest Statement
The authors have declared no competing interest.
Footnotes
Authorship note: ZFH and MK made an equal contribution to this work.
Conflict of interest statement: The authors have declared that no conflict of interest exists.
Abbreviations
- ANOVA
- Analysis of variance
- BrS
- Brugada syndrome
- Cryo-EM
- cryogenic electron microscopy
- DTT
- Dithiothreitol
- ECL
- Enhanced chemiluminescence
- ER
- Endoplasmic reticulum
- HRP
- Horseradish peroxidase
- MD
- Molecular dynamics
- PDB
- Protein database
- RMSD
- Root-mean-square deviation of atomic positions
- SND
- Sinus node dysfunction