A structurally precise mechanism links an epilepsy-associated <i>KCNC2</i> potassium channel mutation to interneuron dysfunction
Jérôme Clatot, Christopher Brian Currin, Qiansheng Liang, Tanadet Pipatpolkai, Shavonne L. Massey, Ingo Helbig, Lucie Delemotte, Tim P. Vogels, Manuel Covarrubias, Ethan M. Goldberg
Abstract
De novo heterozygous variants in KCNC2 encoding the voltage-gated potassium (K + ) channel subunit Kv3.2 are a recently described cause of developmental and epileptic encephalopathy (DEE). A de novo variant in KCNC2 c.374G > A (p.Cys125Tyr) was identified via exome sequencing in a patient with DEE. Relative to wild-type Kv3.2, Kv3.2-p.Cys125Tyr induces K + currents exhibiting a large hyperpolarizing shift in the voltage dependence of activation, accelerated activation, and delayed deactivation consistent with a relative stabilization of the open conformation, along with increased current density. Leveraging the cryogenic electron microscopy (cryo-EM) structure of Kv3.1, molecular dynamic simulations suggest that a strong π-π stacking interaction between the variant Tyr125 and Tyr156 in the α-6 helix of the T1 domain promotes a relative stabilization of the open conformation of the channel, which underlies the observed gain of function. A multicompartment computational model of a Kv3-expressing parvalbumin-positive cerebral cortex fast-spiking γ-aminobutyric acidergic (GABAergic) interneuron (PV-IN) demonstrates how the Kv3.2-Cys125Tyr variant impairs neuronal excitability and dysregulates inhibition in cerebral cortex circuits to explain the resulting epilepsy.