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Editing slows Kvβ1.1-induced inactivation kinetics of I407M and V408A channels. (a,c) Representative β -inactivation traces, depicting whole-cell K + currents, were recorded from oocytes coexpressing the Kvβ 1.1 subunit and either the (a) I407M or (c) V408A channel, in the non-edited (N) or edited (E) isoform. Test potentials were elicited in 10 mV voltage steps from 10 to 80 mV, from a holding potential of − 80 mV. (b,d) Inactivation kinetics were measured by fitting single exponential curves to the test pulse currents, to determine the associated τ value (mean ± SEM, n = 3–6 oocytes). (b) I407M E channels were significantly slower to inactivate than I407M N channels at every voltage (p ≤ 0.0001) and both I407M N and I407M E channels were slower than WT N and WT E channels, respectively, at every voltage (p ≤ 0.0001). (d) V408A E channels were significantly slower than V408A N channels from 10 to 50 mV (0.05 > p ≥ 0.0005). V408A E channels were slower than WT E channels from 10 to 60 mV (0.05 > p ≥ 0.0001). V408A N channels were significantly slower than WT N channels at all voltages (p ≤ 0.0001). Small error bars were obscured by the data symbols in some cases.
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Adenosine-to-inosine RNA editing in transcripts encoding the voltage-gated potassium channel Kv1.1 converts an isoleucine to valine codon for amino acid 400, speeding channel recovery from inactivation. Numerous Kv1.1 mutations have been associated with the human disorder Episodic Ataxia Type-1 (EA1), characterized by stress-induced ataxia, myokymi...
Citations
... Millions of RNA editing sites have been identified in humans, though their significance is obscured as over 95% occur in Alu elements, non-coding mobile DNA retroelements that comprise ~11% of the human genome [28][29][30][31] . However, aberrant editing of mRNAs encoding ion channels is associated with several neurological conditions in humans [32][33][34][35][36] . A major role for RNA editing in mammalian neurons is the substitution of a glutamine (E) by an arginine (R) residue in the AMPA GluR2 receptor subunit that controls the channel's Ca 2+ permeability 37,38 . ...
RNA editing is a post-transcriptional source of protein diversity and occurs across the animal kingdom. Given the complete profile of mRNA targets and their editing rate in individual cells is unclear, we analyzed single cell RNA transcriptomes from Drosophila larval tonic and phasic glutamatergic motoneuron subtypes to determine the most highly edited targets and identify cell-type specific editing. From ∼15,000 genes encoded in the genome, 316 high confidence A-to-I canonical RNA edit sites were identified, with 102 causing missense amino acid changes in proteins regulating membrane excitability, synaptic transmission, and cellular function. Some sites showed 100% editing in single neurons as observed with mRNAs encoding mammalian AMPA receptors. However, most sites were edited at lower levels and generated variable expression of edited and unedited mRNAs within individual neurons. Together, these data provide insights into how the RNA editing landscape alters protein function to modulate the properties of two well-characterized neuronal populations in Drosophila .
... The Flag-tag protein affinity sequence (DYKDDDDK; Sigma-Aldrich) was added to the N-terminal to enable confirmation of expression. The cDNA was subcloned into the Xenopus expression vector pGEM HE as described previously [38]. The Bgl-FaNaC full-length RNA was transcribed in vitro, capped and polyadenylated using the T7 mScript Standard mRNA Production System (CellScript, Madison WI). ...
... Injected oocytes were placed at the bottom of a plastic recording chamber (3 ml volume) lined with a nylon mesh and continuously perfused with ND96 (96 mM NaCl, 2 mM KCl, 1.8 mM CaCl 2 , 1 mM MgCl 2 , 5 mM HEPES, pH 7.6; see detailed methods in [38]). An OC725B oocyte clamp (Warner Instruments LLC., Hamden CT) was used to clamp the membrane potential at -60 mV with independent microelectrodes for recording (0.1 M potassium chloride) and passing current (3 M potassium chloride). ...
The neglected tropical disease schistosomiasis impacts over 700 million people globally. Schistosoma mansoni, the trematode parasite that causes the most common type of schistosomiasis, requires planorbid pond snails of the genus Biomphalaria to support its larval development and transformation to the cercarial form that can infect humans. A greater understanding of neural signaling systems that are specific to the Biomphalaria intermediate host could lead to novel strategies for parasite or snail control. This study examined a Biomphalaria glabrata neural channel that is gated by the neuropeptide FMRF-NH2. The Biomphalaria glabrata FMRF-NH2 gated sodium channel (Bgl-FaNaC) amino acid sequence was highly conserved with FaNaCs found in related gastropods, especially the planorbid Planorbella trivolvis (91% sequence identity). In common with the P. trivolvis FaNaC, the B. glabrata channel exhibited a low affinity (EC50: 3 x 10-4 M) and high specificity for the FMRF-NH2 agonist. Its expression in the central nervous system, detected with immunohistochemistry and in situ hybridization, was widespread, with the protein localized mainly to neuronal fibers and the mRNA confined to cell bodies. Colocalization of the Bgl-FaNaC message with its FMRF-NH2 agonist precursor occurred in some neurons associated with male mating behavior. At the mRNA level, Bgl-FaNaC expression was decreased at 20 and 35 days post infection (dpi) by S. mansoni. Increased expression of the transcript encoding the FMRF-NH2 agonist at 35 dpi was proposed to reflect a compensatory response to decreased receptor levels. Altered FMRF-NH2 signaling could be vital for parasite proliferation in its intermediate host and may therefore present innovative opportunities for snail control.
... Defects in Kv1.1 channels result in accelerated decay of outward potassium current during prolonged depolarization of the membrane potential and ultimately in reduced Kv1.1 current amplitude in cerebellar basket cells (Peters et al., 2011). Noteworthily, some missense variants in KCNA1 have been demonstrated to decrease Kv1.1 RNA editing both in vitro and in vivo (mouse model) (Ferrick-Kiddie et al., 2017). Wide inter-and intrafamilial phenotypic variability is recognized in EA1 (Graves et al., 2014;D'Adamo et al., 2015). ...
Paroxysmal movement disorders have traditionally been classified into paroxysmal dyskinesia (PxD), which consists in attacks of involuntary movements (mainly dystonia and/or chorea) without loss of consciousness, and episodic ataxia (EA), which features spells of cerebellar dysfunction with or without interictal neurological manifestations. In this chapter, PxD will be discussed first according to the trigger-based classification, thus reviewing clinical, genetic, and molecular features of paroxysmal kinesigenic dyskinesia, paroxysmal nonkinesigenic dyskinesia, and paroxysmal exercise-induced dyskinesia. EA will be presented thereafter according to their designated gene or genetic locus. Clinicogenetic similarities among paroxysmal movement disorders have progressively emerged, which are herein highlighted along with growing evidence that their pathomechanisms overlap those of epilepsy and migraine. Advances in our comprehension of the biological pathways underlying paroxysmal movement disorders, which involve ion channels as well as proteins associated with the vesical synaptic cycle or implicated in neuronal energy metabolism, may represent the cornerstone for defining a shared pathophysiologic framework and developing target-specific therapies.
... K V 1.1 I/V editing reduces the rate of K V 1.1-induced inactivation and have reduced membrane expression of homomeric K V 1.1 channels [17,141]. Reduction of K V 1.1 I/V editing was observed in patients suffering from episodic ataxia type 1 and the genetic mutations are located within the double-stranded loop structure that is formed by the ECS and the sequence that contains the editing site [40]. Highly unsaturated fatty acids, arachidonic acid (AA), docosahexaenoic acid and anandamide (N-arachidonylethanolamide), which are involved in both neurodevelopment and α-synucleinrelated diseases (e.g. ...
Adenosine-to-inosine (A-to-I) RNA editing is a post-transcriptional modification that diversifies protein functions by recoding RNA or alters protein quantity by regulating mRNA level. A-to-I editing is catalyzed by adenosine deaminases that act on RNA. Millions of editing sites have been reported, but they are mostly found in non-coding sequences. However, there are also several recoding editing sites in transcripts coding for ion channels or transporters that have been shown to play important roles in physiology and changes in editing level are associated with neurological diseases. These editing sites are not only found to be evolutionary conserved across species, but they are also dynamically regulated spatially, developmentally and by environmental factors. In this review, we discuss the current knowledge of A-to-I RNA editing of ion channels and receptors in the context of their roles in physiology and pathological disease. We also discuss the regulation of editing events and site-directed RNA editing approaches for functional study that offer a therapeutic pathway for clinical applications.
... This editing event increases fourfold in the entorhinal cortex of chronic epileptic rats compared to their healthy counterparts [64]. Mutations in the gene that encodes Kv1.1 (KCNA1) that hinder the Kv1.1 I/V site editing are also hypothesized to be responsible for the epileptic events observed in patients suffering from episodic ataxia type 1 (EA1) [66]. ...
RNA editing contributes to transcriptome diversification through RNA modifications in relation to genome-encoded information (RNA-DNA differences, RDDs). The deamination of Adenosine (A) to Inosine (I) or Cytidine (C) to Uridine (U) is the most common type of mammalian RNA editing. It occurs as a nuclear co-and/or post-transcriptional event catalyzed by ADARs (Adenosine deaminases acting on RNA) and APOBECs (apolipoprotein B mRNA editing enzyme catalytic polypeptide-like genes). RNA editing may modify the structure, stability, and processing of a transcript. This review focuses on RNA editing in psychiatric, neurological, neurodegenerative (NDs), and autoimmune brain disorders in humans and rodent models. We discuss targeted studies that focus on RNA editing in specific neuron-enriched transcripts with well-established functions in neuronal activity, and transcriptome-wide studies, enabled by recent technological advances. We provide comparative editome analyses between human disease and corresponding animal models. Data suggest RNA editing to be an emerging mechanism in disease development, displaying common and disease-specific patterns. Commonly edited RNAs represent potential disease-associated targets for therapeutic and diagnostic values. Currently available data are primarily descriptive, calling for additional research to expand global editing profiles and to provide disease mechanistic insights. The potential use of RNA editing events as disease biomarkers and available tools for RNA editing identification, classification, ranking, and functional characterization that are being developed will enable comprehensive analyses for a better understanding of disease(s) pathogenesis and potential cures.
... Inactivation kinetics of Kv1.1 is an important channel property associated with neurological diseases. Previous functional studies about Kcna1 missense mutations found in EA1 patients generally exhibited changes in the recovery rate from inactivation, resulting in a slowing of activity-dependent recruitment of inactivation [42][43][44]. Such changes in channel kinetics would impact intrinsic membrane properties of a neuron, and spiking pattern as well. ...
The Shaker-related potassium channel Kv1.1 subunit has important implications for controlling neuronal excitabilities. A particular recoding by A-to-I RNA editing at I400 of Kv1.1 mRNA is an underestimated mechanism for fine-tuning the properties of Kv1.1-containing channels. Knowledge about functional differences between edited (I400V) and non-edited Kv1.1 isoforms is insufficient, especially in neurons. To understand their different roles, the two Kv1.1 isoforms were overexpressed in the prefrontal cortex via local adeno-associated virus-mediated gene delivery. The I400V isoform showed a higher competitiveness in membrane translocalization, but failed to reduce current-evoked discharges and showed weaker impact on spiking-frequency adaptation in the transduced neurons. The non-edited Kv1.1 overexpression led to slight elevations in both fast- and non-inactivating current components of macroscopic potassium current. By contrast, the I400V overexpression did not impact the fast-inactivating current component. Further isolation of Kv1.1-specific current by its specific blocker dendrotoxin-κ showed that both isoforms did result in significant increases in current amplitude, whereas the I400V was less efficient in contributing the fast-inactivating current component. Voltage-dependent properties of the fast-inactivating current component did not alter for both isoforms. For recovery kinetics, the I400V showed a significant acceleration of recovery from fast inactivation. The gene delivery of the I400V rather than the wild type exhibited anxiolytic activities, which was assessed by an open field test. These results suggest that the Kv1.1 RNA editing isoforms have different properties and outcomes, reflecting the functional and phenotypic significance of the Kv1.1 RNA editing in neurons.
... Three EA1-related mutations (V404I, I407M, and V408A) have been identified in the RNA duplex region required for Kv1.1RNA editing [79,80]. A study from in vitro and in vivo model systems showed that EA1 mutations lead to a significant reduction of Kv1.1 transcript editing, indicating that these mutations have both direct and indirect influences on EA1 symptoms (Fig. 3C) [81]. ...
Adenosine-to-inosine (A-to-I) editing is one of the most prevalent post-transcriptional RNA modifications in metazoan. This reaction is catalyzed by enzymes called adenosine deaminases acting on RNA (ADARs). RNA editing is involved in the regulation of protein function and gene expression. The numerous A-to-I editing sites have been identified in both coding and non-coding RNA transcripts. These editing sites are also found in various genes expressed in the central nervous system (CNS) and play an important role in neurological development and brain function. Aberrant regulation of RNA editing has been associated with the pathogenesis of neurological and psychiatric disorders, suggesting the physiological significance of RNA editing in the CNS. In this review, we discuss the current knowledge of editing on neurological disease and development.
... KCNA1 transcripts can be edited by human adenosine deaminase acting on RNA 2 (ADAR2). ADAR2 converts adenosine to an inosine in the KCNA1 transcript, thereby resulting in an isoleucine-to-valine substitution at amino acid (aa) 400 [65,66]. This editing process occurs normally in the brain, but the percentage of edited KCNA1 transcripts varies by region. ...
... This editing process occurs normally in the brain, but the percentage of edited KCNA1 transcripts varies by region. For example, in the mouse brain, approximately 20%, 35%, and 50% of transcripts are edited in the hippocampus, cortex, and cerebellum, respectively [66]. For this editing to take place, an RNA hairpin must form between complementary base pairs flanking the edit site on the transcript. ...
... ADAR2 then recognizes and enzymatically processes this hairpin as a substrate [65]. The aa at position 400, which is subject to RNA editing, is predicted to line the pore in S6 where it may interact with the inactivation particle of the channel contributed by β-subunits [66]. In support of this, functional biophysical studies have demonstrated that this RNA editing event decreases the channel recovery time from inactivation [65,66]. ...
Mutations in the KCNA1 gene, which encodes voltage-gated Kv1.1 potassium channel α-subunits, cause a variety of human diseases, complicating simple genotype–phenotype correlations in patients. KCNA1 mutations are primarily associated with a rare neurological movement disorder known as episodic ataxia type 1 (EA1). However, some patients have EA1 in combination with epilepsy, whereas others have epilepsy alone. KCNA1 mutations can also cause hypomagnesemia and paroxysmal dyskinesia in rare cases. Why KCNA1 variants are associated with such phenotypic heterogeneity in patients is not yet understood. In this review, literature databases (PubMed) and public genetic archives (dbSNP and ClinVar) were mined for known pathogenic or likely pathogenic mutations in KCNA1 to examine whether patterns exist between mutation type and disease manifestation. Analyses of the 47 deleterious KCNA1 mutations that were identified revealed that epilepsy or seizure-related variants tend to cluster in the S1/S2 transmembrane domains and in the pore region of Kv1.1, whereas EA1-associated variants occur along the whole length of the protein. In addition, insights from animal models of KCNA1 channelopathy were considered, as well as the possible influence of genetic modifiers on disease expressivity and severity. Elucidation of the complex relationship between KCNA1 variants and disease will enable better diagnostic risk assessment and more personalized therapeutic strategies for KCNA1 channelopathy.
... A KCNA1 variant near the PVP motif (p.Val408Leu) was also associated with cognitive impairment and early-onset epilepsy in three family members [28]. Recently, a KCNA1 variant affecting amino-acid 408 changed channel opening, closing, and inactivation by altering RNA duplex structure, a novel post-translational modification effect [29]. A neonate of consanguineous parents with profound DEE was found to harbour a missense homozygous/ recessive KCNA1 variant p.Val368Leu (affecting the pore domain) demonstrating strong LOF effects. ...
Next-generation sequencing has enhanced discovery of many disease-associated genes in previously unexplained epilepsies, mainly in developmental and epileptic encephalopathies and familial epilepsies. We now classify these disorders according to the underlying molecular pathways, which encompass a diverse array of cellular and sub-cellular compartments/signalling processes including voltage-gated ion-channel defects. With the aim to develop and increase the use of precision medicine therapies, understanding the pathogenic mechanisms and consequences of disease-causing variants has gained major relevance in clinical care. The super-family of voltage-gated potassium channels is the largest and most diverse family among the ion channels, encompassing approximately 80 genes. Key potassium channelopathies include those affecting the KV, KCa and Kir families, a significant proportion of which have been implicated in neurological disease. As for other ion channel disorders, different pathogenic variants within any individual voltage-gated potassium channel gene tend to affect channel protein function differently, causing heterogeneous clinical phenotypes. The focus of this review is to summarise recent clinical developments regarding the key voltage-gated potassium (KV) family-related epilepsies, which now encompasses approximately 12 established disease-associated genes, from the KCNA-, KCNB-, KCNC-, KCND-, KCNV-, KCNQ- and KCNH-subfamilies.
... La ataxia episódica tipo 1 de los humanos es un trastorno neurológico infrecuente caracterizado por incoordinación motora inducida por el estrés asociada con mioquimia, y que puede coincidir con convulsiones ( Graves et al. 2014). Los análisis genéticos en la región del cromosoma 12p que codifica VGCK (KCNA1) identificaron más de 30 mutaciones heterocigotas de sentido erróneo, que indican que la ataxia episódica familiar con mioquimia resulta de mutaciones en dicho gen ( Browne et al. 1994;Graves et al. 2014;Ferrick-Kiddie et al. 2017). En medicina veterinaria se ha comunicado una degeneración espinocerebelosa en perros jóvenes del denominado "grupo Russell terriers", integrado por Jack Russell terrier, Parson Russell terrier y Fox terrier de pelo liso, todos ellos descendientes probablemente del mismo criador ( Bjorck et al. 1957;Wessmann et al. 2004;Rohdin et al. 2010;Vanhaesebrouck et al. 2010b;Simpson et al. 2012;Forman et al. 2013;Gilliam et al. 2014;Rohdin et al. 2015). ...
