Abstract
Human mutations in the cytoplasmic C-terminal domain of Slack sodium-activated potassium (KNa) channels result in childhood epilepsy with severe intellectual disability. Slack currents can be increased by pharmacological activators or by phosphorylation of a Slack C-terminal residue by protein kinase C. Using an optical biosensor assay, we find that Slack channel stimulation in neurons or transfected cells produces loss of mass near the plasma membrane. Slack mutants associated with intellectual disability fail to trigger any change in mass. The loss of mass results from the dissociation of the protein phosphatase 1 (PP1) targeting protein, Phactr-1, from the channel. Phactr1 dissociation is specific to wild-type Slack channels and is not observed when related potassium channels are stimulated. Our findings suggest that Slack channels are coupled to cytoplasmic signaling pathways and that dysregulation of this coupling may trigger the aberrant intellectual development associated with specific childhood epilepsies.
Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.
MeSH terms
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Adaptor Proteins, Signal Transducing / antagonists & inhibitors
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Adaptor Proteins, Signal Transducing / genetics
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Adaptor Proteins, Signal Transducing / metabolism
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Animals
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Biosensing Techniques
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Bithionol / pharmacology
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Bridged Bicyclo Compounds, Heterocyclic / pharmacology
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Cell Membrane / drug effects
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Cell Membrane / metabolism*
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Cerebral Cortex / cytology
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Cerebral Cortex / drug effects
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Cerebral Cortex / metabolism
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Fragile X Mental Retardation Protein / antagonists & inhibitors
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Fragile X Mental Retardation Protein / genetics*
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Fragile X Mental Retardation Protein / metabolism
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Gene Expression Regulation
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HEK293 Cells
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Humans
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Ion Transport / drug effects
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Mice
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Mice, Knockout
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Microfilament Proteins / antagonists & inhibitors
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Microfilament Proteins / genetics*
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Microfilament Proteins / metabolism
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Mutation
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Nerve Tissue Proteins / agonists
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Nerve Tissue Proteins / genetics*
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Nerve Tissue Proteins / metabolism
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Neurons / cytology
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Neurons / drug effects
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Neurons / metabolism*
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Patch-Clamp Techniques
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Phosphorylation
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Potassium Channels / agonists
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Potassium Channels / genetics*
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Potassium Channels / metabolism
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Potassium Channels, Sodium-Activated
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Primary Cell Culture
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Protein Binding
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RNA, Small Interfering / genetics
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RNA, Small Interfering / metabolism
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Signal Transduction*
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Thiazolidines / pharmacology
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Xenopus laevis
Substances
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Adaptor Proteins, Signal Transducing
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Bridged Bicyclo Compounds, Heterocyclic
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CYFIP1 protein, human
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FMR1 protein, human
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KCNT1 protein, human
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Microfilament Proteins
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Nerve Tissue Proteins
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PHACTR1 protein, human
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Potassium Channels
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Potassium Channels, Sodium-Activated
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RNA, Small Interfering
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Thiazolidines
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Fragile X Mental Retardation Protein
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Bithionol
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latrunculin B