Dataset Information

Structure-Based Identification and Characterization of Inhibitors of the Epilepsy-Associated K_Na1.1 (KCNT1) Potassium Channel.

ABSTRACT: Drug-resistant epileptic encephalopathies of infancy have been associated with KCNT1 gain-of-function mutations, which increase the activity of K_Na1.1 sodium-activated potassium channels. Pharmacological inhibition of hyperactive K_Na1.1 channels by quinidine has been proposed as a stratified treatment, but mostly this has not been successful, being linked to the low potency and lack of specificity of the drug. Here we describe the use of a previously determined cryo-electron microscopy-derived K_Na1.1 structure and mutational analysis to identify how quinidine binds to the channel pore and, using computational methods, screened for compounds predicated to bind to this site. We describe six compounds that inhibited K_Na1.1 channels with low- and sub-micromolar potencies, likely also through binding in the intracellular pore vestibule. In hERG inhibition and cytotoxicity assays, two compounds were ineffective. These may provide starting points for the development of new pharmacophores and could become tool compounds to study this channel further.

SUBMITTER: Cole BA

PROVIDER: S-EPMC7225746 | biostudies-literature | 2020 May

REPOSITORIES: biostudies-literature

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Publications

Structure-Based Identification and Characterization of Inhibitors of the Epilepsy-Associated KNa1.1 (KCNT1) Potassium Channel.

Cole Bethan A BA Johnson Rachel M RM Dejakaisaya Hattapark H Pilati Nadia N Fishwick Colin W G CWG Muench Stephen P SP Lippiat Jonathan D JD

iScience 20200425 5

Drug-resistant epileptic encephalopathies of infancy have been associated with KCNT1 gain-of-function mutations, which increase the activity of KNa1.1 sodium-activated potassium channels. Pharmacological inhibition of hyperactive KNa1.1 channels by quinidine has been proposed as a stratified treatment, but mostly this has not been successful, being linked to the low potency and lack of specificity of the drug. Here we describe the use of a previously determined cryo-electro ...[more]

PMID: 32408169

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Project description:The Alzheimer BACE1 enzyme cleaves numerous substrates, with largely unknown physiological consequences. We have previously identified the contribution of elevated BACE1 activity to voltage-gated sodium channel Na(v)1.1 density and neuronal function. Here, we analyzed physiological changes in sodium channel metabolism in BACE1-null mice. Mechanistically, we first confirmed that endogenous BACE1 requires its substrate, the ?-subunit Na(v)?(2), to regulate levels of the pore-forming ?-subunit Na(v)1.1 in cultured primary neurons. Next, we analyzed sodium channel ?-subunit levels in brains of BACE1-null mice at 1 and 3 months of age. At both ages, we found that Na(v)1.1 protein levels were significantly decreased in BACE1-null versus wild-type mouse brains, remaining unchanged in BACE1-heterozygous mouse brains. Interestingly, levels of Na(v)1.2 and Na(v)1.6 ?-subunits also decreased in 1-month-old BACE1-null mice. In the hippocampus of BACE1-null mice, we found a robust 57% decrease of Na(v)1.1 levels. Next, we performed surface biotinylation studies in acutely dissociated hippocampal slices from BACE1-null mice. Hippocampal surface Na(v)1.1 levels were significantly decreased, but Na(v)1.2 surface levels were increased in BACE1-null mice perhaps as a compensatory mechanism for reduced surface Na(v)1.1. We also found that Na(v)?(2) processing and Na(v)1.1 mRNA levels were significantly decreased in brains of BACE1-null mice. This suggests a mechanism consistent with BACE1 activity regulating mRNA levels of the ?-subunit Na(v)1.1 via cleavage of cell-surface Na(v)?(2). Together, our data show that endogenous BACE1 activity regulates total and surface levels of voltage-gated sodium channels in mouse brains. Both decreased Na(v)1.1 and elevated surface Na(v)1.2 may result in a seizure phenotype. Our data caution that therapeutic BACE1 activity inhibition in Alzheimer disease patients may affect Na(v)1 metabolism and alter neuronal membrane excitability in Alzheimer disease patients.

Dataset Information

Structure-Based Identification and Characterization of Inhibitors of the Epilepsy-Associated K_Na1.1 (KCNT1) Potassium Channel.

Publications

Structure-Based Identification and Characterization of Inhibitors of the Epilepsy-Associated K<sub>Na</sub>1.1 (KCNT1) Potassium Channel.

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