A Specific Two-pore Domain Potassium Channel Blocker Defines the Structure of the TASK-1 Open Pore*

Two-pore domain potassium (K2P) channels play a key role in setting the membrane potential of excitable cells. Despite their role as putative targets for drugs and general anesthetics, little is known about the structure and the drug binding site of K2P channels. We describe A1899 as a potent and highly selective blocker of the K2P channel TASK-1. As A1899 acts as an open-channel blocker and binds to residues forming the wall of the central cavity, the drug was used to further our understanding of the channel pore. Using alanine mutagenesis screens, we have identified residues in both pore loops, the M2 and M4 segments, and the halothane response element to form the drug binding site of TASK-1. Our experimental data were used to validate a K2P open-pore homology model of TASK-1, providing structural insights for future rational design of drugs targeting K2P channels

Spectrum of Phenotypic, Genetic, and Functional Characteristics in Epilepsy Patients With KCNC2 Pathogenic Variants 10.1212/WNL.0000000000200660

Background: KCNC2 encodes Kv3.2, a member of the Shaw-related (Kv3) voltage-gated potassium channel subfamily, which is important for sustained high-frequency firing and optimized energy efficiency of action potentials in the brain. The objective of this study was to analyse the clinical phenotype, genetic background, and biophysical function of disease-associated Kv3.2 variants.Methods: Individuals with KCNC2 variants detected by exome sequencing were selected for clinical, further genetic, and functional analysis. Cases were referred through clinical and research collaborations. Selected de novo variants were examined electrophysiologically in Xenopus laevis oocytes.Results: We identified novel KCNC2 variants in 18 patients with various forms of epilepsy including genetic generalized epilepsy (GGE), developmental and epileptic encephalopathy (DEE) including early-onset absence epilepsy (EOAE), focal epilepsy (FE), and myoclonic-atonic epilepsy (MAE). 10/18 variants were de novo and 8/18 variants were classified as modifying variants. 8 drug responsive cases became seizure-free using valproic acid as monotherapy or in combination including severe DEE cases. Functional analysis of four variants demonstrated gain-of-function in three severely affected DEE cases and loss-of-function in one case with a milder phenotype (GGE) as the underlying pathomechanisms.Conclusion: These findings implicate KCNC2 as a novel causative gene for epilepsy and emphasize the critical role of KV3.2 in the regulation of brain excitability