Investigating the role of the I-II linker in Nav1.5 channel function
Emily Wagner1, Martina Marras1, Shashi Kumar1
1Department of Biomedical Engineering, McKelvey School of Engineering, Washington University in St. Louis, St. Louis, MO, USA.
The Journal of General Physiology
|September 4, 2025
Summary
The cardiac sodium channel Nav1.5 I-II linker
Area of Science:
- Molecular biology
- Cardiovascular physiology
- Ion channel biophysics
Background:
- The cardiac voltage-gated sodium channel, Nav1.5, is crucial for initiating the cardiac action potential.
- Nav1.5 dysfunction is linked to life-threatening arrhythmias and sudden cardiac arrest.
- The I-II and II-III cytoplasmic linkers of Nav1.5 are structurally uncharacterized and their function is unclear.
Purpose of the Study:
- To investigate the functional role of the Nav1.5 I-II linker in cardiac action potential generation.
- To determine the impact of specific regions and mutations within the I-II linker on Nav1.5 channel function.
- To explore the potential role of the I-II linker in protein-protein interactions relevant to channel function and pathogenicity.
Main Methods:
- Site-directed mutagenesis to create Nav1.5 constructs with specific I-II linker regions deleted.
- Electrophysiological recordings (e.g., patch-clamp) to assess channel gating and current density.
- Phylogenetic analysis to identify conserved residues within the I-II linker across species.
Main Results:
- Deletion of large I-II linker regions had minimal effects on Nav1.5 gating, although two deletions reduced peak current.
- A specific proline residue (P627) in the I-II linker, conserved in mammals, significantly altered channel activation when mutated to serine (P627S).
- Neither phosphosilent (P627A) nor phosphomimetic (P627E) mutations at this site replicated the effect, suggesting phosphorylation or a specific serine property is involved.
Conclusions:
- The Nav1.5 I-II linker's primary role may involve facilitating interactions with other proteins rather than directly modulating gating.
- Specific point mutations within the I-II linker can have significant functional consequences, potentially impacting cardiac electrophysiology.
- Understanding these interactions is critical for evaluating the pathogenicity of Nav1.5 variants associated with cardiac arrhythmias.
Related Concept Videos
01:19Ligand-gated Ion Channels
12.7K
Ligand-gated ion channels are transmembrane proteins with a channel for ions to pass through and a binding site for a ligand. The channel opens only when a ligand attaches to the binding site.
Three Subfamilies of Ligand-gated Ion Channels
Ligand-gated ion channels fall into three subfamilies. The 'Cys-loop' includes the nicotinic acetylcholine receptors, γ-aminobutyric acid (GABA), glycine, and 5-hydroxytryptamine receptors. The second one is the 'Pore-loop' channels that...
Three Subfamilies of Ligand-gated Ion Channels
Ligand-gated ion channels fall into three subfamilies. The 'Cys-loop' includes the nicotinic acetylcholine receptors, γ-aminobutyric acid (GABA), glycine, and 5-hydroxytryptamine receptors. The second one is the 'Pore-loop' channels that...
12.7K
01:30Ligand-Gated Ion Channel Receptor: Gating Mechanism
2.6K
Ligand-gated ion channels are transmembrane proteins that play a vital role in intercellular communication and functions of the nervous system. They allow the influx of ions across the membrane once the neurotransmitter binds, allowing the subsequent transmission of electrical excitation across the neurons. Other ligand-gated ion channels, like the γ-aminobutyric acid (GABA) receptor, permit anions like chloride into the cells on the binding of the GABA molecule. Their entry into the cell...
2.6K
01:19Ion Channels
87.9K
The movement of ions like sodium, potassium, and calcium into and out of the cell is essential to maintain the electrochemical gradient in living cells. The ion channels—a class of membrane transport proteins—help maintain this ionic gradient for the smooth functioning of physiological activities such as maintaining cell size and volume, conducting nerve impulses, and gas and nutrient exchange.
Ion channels are specialized integral membrane proteins on the plasma membrane that allow...
Ion channels are specialized integral membrane proteins on the plasma membrane that allow...
87.9K
01:19The Role of Ion Channels in Neuronal Computation
3.3K
A postsynaptic neuron usually receives numerous impulses from several other presynaptic neurons. The axon hillock of the postsynaptic neuron integrates all these signals and determines the likelihood of firing an action potential.
Sometimes a single EPSP is strong enough to induce an action potential in the postsynaptic neuron. However, multiple presynaptic inputs must often create EPSPs around the same time for the postsynaptic neuron to be sufficiently depolarized to fire an action potential....
Sometimes a single EPSP is strong enough to induce an action potential in the postsynaptic neuron. However, multiple presynaptic inputs must often create EPSPs around the same time for the postsynaptic neuron to be sufficiently depolarized to fire an action potential....
3.3K
01:17Intracellular Signaling Affects Focal Adhesions
2.8K
Integrins act both as extracellular input receivers and as intracellular processing activators. As their name suggests, integrins are entirely integrated into the membrane structure. Their hydrophobic membrane-spanning regions interact with the phospholipid bilayer's hydrophobic region. These membrane receptors provide extracellular attachment sites for effectors like hormones and growth factors. They activate intracellular response cascades when their effectors are bound and active.
Some...
Some...
2.8K
00:49Ligand Binding and Linkage
4.9K
Allosteric proteins have more than one ligand binding site; the binding of a ligand to any of these sites influences the binding of ligands to the other sites. When a protein is allosteric, its binding sites are called coupled or linked. In the case of enzymes, the site that binds to the substrate is known as the active site and the other site is known as the regulatory site. When a ligand binds to the regulatory site, this leads to conformational changes in the protein that can influence...
4.9K