A structurally precise mechanism links an epilepsy-associated KCNC2 potassium channel mutation to interneuron...

Area of Science:

• Neuroscience
• Molecular Biology
• Genetics

Background:

• De novo heterozygous variants in KCNC2, encoding the Kv3.2 potassium channel subunit, are a recently identified cause of developmental and epileptic encephalopathy (DEE).
• Understanding the molecular mechanisms underlying KCNC2-related DEE is crucial for developing targeted therapies.

Purpose of the Study:

• To investigate the functional consequences of a specific de novo KCNC2 variant (c.374G > A, p.Cys125Tyr) associated with DEE.
• To elucidate the structural and functional basis of the observed gain-of-function mutation in the Kv3.2 channel.

Main Methods:

• Exome sequencing identified the KCNC2 variant in a patient with DEE.
• Electrophysiological recordings characterized the functional properties of the mutant Kv3.2 channel.
• Cryogenic electron microscopy (cryo-EM) structures and molecular dynamic simulations were used to analyze the structural impact of the variant.
• Multicompartment computational modeling simulated the effect of the variant on neuronal excitability and circuit function.

Main Results:

• The Kv3.2-p.Cys125Tyr variant induced significant changes in K+ currents, including a hyperpolarizing shift in activation, accelerated activation, delayed deactivation, and increased current density.
• Molecular dynamics simulations suggested that the variant Tyr125 residue stabilizes the open channel conformation through π-π stacking interactions.
• Computational modeling demonstrated that the Kv3.2-Cys125Tyr variant impairs fast-spiking GABAergic interneuron excitability and dysregulates cortical circuits, explaining the epilepsy phenotype.

Conclusions:

• The KCNC2-p.Cys125Tyr variant results in a gain-of-function of the Kv3.2 channel, leading to impaired neuronal function and DEE.
• Structural and computational analyses provide a mechanistic link between the genetic variant and the observed epilepsy phenotype.
• This study deepens the understanding of KCNC2-related channelopathies and their impact on brain function.