The Experts below are selected from a list of 7329 Experts worldwide ranked by ideXlab platform
Jinchung Lin - One of the best experts on this subject based on the ideXlab platform.
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molecular docking of the scorpion toxin tc1 to the structural model of the voltage gated Potassium Channel Kv1.1 from human homo sapiens
Journal of Biomolecular Structure & Dynamics, 2004Co-Authors: Hsuanliang Liu, Jinchung LinAbstract:In this study, structural model of the pore loop region of the voltage-gated Potassium Channel Kv1.1 from human Homo sapiens was constructed based on the crystallographic structure of KcsA by structural homology. The pore loop region of Kv1.1 exhibits similar folds as that of KcsA. The structural feature of the selectivity filter of Kv1.1 is nearly identical to that of KcsA, whereas most of the structural variations occur in the turret as well as in the inner and outer helices. Molecular docking experiments of the scorpion toxin Tc1 from Tityus cambridgei to the outer vestibule of KcsA as well as Kv1.1 were subsequently performed with various initial Tc1 orientations. Tc1 was found to form the most stable complexes with these two K+ Channels when the side chain of Lys14 occupies the pore of the selectivity filter through electrostatic interaction. Tc1 binds preferentially towards Kv1.1 than KcsA due to stronger hydrophobic and electrostatic interactions formed between the toxin and the selectivity filter and outer vestibule of Kv1.1. Furthermore, surface complementarity of the outer vestibules of the Channels to the Tc1 spatial conformations also plays an important role in stabilizing both the Tc1/KcsA and Tc1/Kv1.1 complexes.
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structural model of the voltage gated Potassium Channel Kv1.1 and molecular docking of tc1 toxin from tityus cambridgei to kcsa and Kv1.1
Chemical Physics Letters, 2003Co-Authors: Hsuanliang Liu, Jinchung LinAbstract:Abstract In this study, structural model of the pore loop region of the voltage-gated Potassium Channel Kv1.1 was constructed based on the crystallographic structure of KcsA. Subsequently, molecular docking experiments of Tc1 towards KcsA as well as Kv1.1 were performed. Tc1 forms the most stable complexes with these two Channels when the side chain of K14 occupies the first K + binding site. Tc1 binds preferentially towards Kv1.1 than KcsA due to the stronger electrostatic and hydrophobic interactions. Furthermore, surface complementarity of the outer vestibules of the Channel to the Tc1 spatial conformations also plays an important role in stabilizing these Tc1/Channel complexes.
Niels Decher - One of the best experts on this subject based on the ideXlab platform.
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RNA Editing in the Central Cavity as a Mechanism to Regulate Surface Expression of the Voltage-gated Potassium Channel Kv1.1
Journal of Biological Chemistry, 2014Co-Authors: Anne K. Streit, Lina A. Matschke, Susanne Rinne, Amalia M Dolga, Niels DecherAbstract:Voltage-gated Potassium (Kv) 1.1 Channels undergo a specific enzymatic RNA deamination, generating a Channel with a single amino acid exchange located in the inner pore cavity (Kv1.1I400V). We studied I400V-edited Kv1.1 Channels in more detail and found that Kv1.1I400V gave rise to much smaller whole-cell currents than Kv1.1. To elucidate the mechanism behind this current reduction, we conducted electrophysiological recordings on single-Channel level and did not find any differences. Next we examined Channel surface expression in Xenopus oocytes and HeLa cells using a chemiluminescence assay and found the edited Channels to be less readily expressed at the surface membrane. This reduction in surface expression was verified by fluorescence imaging experiments. Western blot analysis for comparison of protein abundances and glycosylation patterns did not show any difference between Kv1.1 and Kv1.1I400V, further indicating that changed trafficking of Kv1.1I400V is causing the current reduction. Block of endocytosis by dynasore or AP180C did not abolish the differences in current amplitudes between Kv1.1 and Kv1.1I400V, suggesting that backward trafficking is not affected. Therefore, our data suggest that I400V RNA editing of Kv1.1 leads to a reduced current size by a decreased forward trafficking of the Channel to the surface membrane. This effect is specific for Kv1.1 because coexpression of Kv1.4 Channel subunits with Kv1.1I400V abolishes these trafficking effects. Taken together, we identified RNA editing as a novel mechanism to regulate homomeric Kv1.1 Channel trafficking. Fine-tuning of Kv1.1 surface expression by RNA editing might contribute to the complexity of neuronal Kv Channel regulation.
Dimitri M Kullmann - One of the best experts on this subject based on the ideXlab platform.
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epilepsy gene therapy using non integrating lentiviral delivery of an engineered Potassium Channel gene
bioRxiv, 2018Co-Authors: Albert Snowball, Dimitri M Kullmann, Elodie Chabrol, Robert C Wykes, Andreas Lieb, Kevan S Hashemi, Matthew C Walker, Stephanie SchorgeAbstract:Refractory focal neocortical epilepsy is a devastating disease for which there is frequently no effective treatment. Gene therapy represents a promising alternative, but treating epilepsy in this way involves irreversible changes to brain tissue, so vector design must be carefully optimized to guarantee safety without compromising efficacy. We set out to develop an epilepsy gene therapy vector optimized for clinical translation. The gene encoding the voltage-gated Potassium Channel Kv1.1, KCNA1, was codon-optimized for human expression and mutated to accelerate the Channels9 recovery from inactivation. For improved safety, this engineered Potassium Channel (EKC) gene was packaged into a non-integrating lentiviral vector under the control of a cell type-specific CAMK2A promoter. In a blinded, randomized, placebo-controlled pre-clinical trial, the EKC lentivector robustly reduced seizure frequency in a rat model of focal neocortical epilepsy characterized by discrete spontaneous seizures. This demonstration of efficacy in a clinically relevant setting, combined with the improved safety conferred by cell type-specific expression and integration-deficient delivery, identify EKC gene therapy as ready for clinical translation in the treatment of refractory focal epilepsy.
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action potential broadening in a presynaptic Channelopathy
Nature Communications, 2016Co-Authors: Rahima Begum, Yamina Bakiri, Kirill E Volynski, Dimitri M KullmannAbstract:Brain development and interictal function are unaffected in many paroxysmal neurological Channelopathies, possibly explained by homoeostatic plasticity of synaptic transmission. Episodic ataxia type 1 is caused by missense mutations of the Potassium Channel Kv1.1, which is abundantly expressed in the terminals of cerebellar basket cells. Presynaptic action potentials of small inhibitory terminals have not been characterized, and it is not known whether developmental plasticity compensates for the effects of Kv1.1 dysfunction. Here we use visually targeted patch-clamp recordings from basket cell terminals of mice harbouring an ataxia-associated mutation and their wild-type littermates. Presynaptic spikes are followed by a pronounced afterdepolarization, and are broadened by pharmacological blockade of Kv1.1 or by a dominant ataxia-associated mutation. Somatic recordings fail to detect such changes. Spike broadening leads to increased Ca(2+) influx and GABA release, and decreased spontaneous Purkinje cell firing. We find no evidence for developmental compensation for inherited Kv1.1 dysfunction.
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Episodic ataxia type 1 mutations differentially affect neuronal excitability and transmitter release.
Disease Models & Mechanisms, 2009Co-Authors: Joost H. Heeroma, Stephanie Schorge, S Rajakulendran, Christian Henneberger, Michael G. Hanna, Dimitri M KullmannAbstract:SUMMARY Heterozygous mutations of KCNA1 , the gene encoding Potassium Channel Kv1.1 subunits, cause episodic ataxia type 1 (EA1), which is characterized by paroxysmal cerebellar incoordination and interictal myokymia. Some mutations are also associated with epilepsy. Although Kv1.1-containing Potassium Channels play important roles in neuronal excitability and neurotransmitter release, it is not known how mutations associated with different clinical features affect the input-output relationships of individual neurons. We transduced rat hippocampal neurons, which were cultured on glial micro-islands, with lentiviruses expressing wild-type or mutant human KCNA1 , and injected either depolarizing currents to evoke action potentials or depolarizing voltage commands to evoke autaptic currents. α-Dendrotoxin and tetraethylammonium allowed a pharmacological dissection of Potassium currents underlying excitability and neurotransmission. Overexpression of wild-type Kv1.1 decreased both neuronal excitability and neurotransmitter release. By contrast, the C-terminus-truncated R417stop mutant, which is associated with severe drug-resistant EA1, had the opposite effect: increased excitability and release probability. Another mutant, T226R, which is associated with EA1 that is complicated by contractures and epilepsy, had no detectable effect on neuronal excitability; however, in common with R417stop, it markedly enhanced neurotransmitter release. The results provide direct evidence that EA1 mutations increase neurotransmitter release, and provide an insight into mechanisms underlying the phenotypic differences that are associated with different mutations.
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a novel mutation in the human voltage gated Potassium Channel gene Kv1.1 associates with episodic ataxia type 1 and sometimes with partial epilepsy
Brain, 1999Co-Authors: Sameer M Zuberi, Dimitri M Kullmann, L H Eunson, A Spauschus, R De Silva, John Tolmie, Nicholas W Wood, Robert Mcwilliam, J P B Stephenson, M G HannaAbstract:Episodic ataxia type 1 (EA1) is a rare autosomal dominant disorder characterized by brief episodes of ataxia associated with continuous interattack myokymia. Point mutations in the human voltage-gated Potassium Channel (Kv1.1) gene on chromosome 12p13 have recently been shown to associate with EA1. A Scottish family with EA1 harbouring a novel mutation in this gene is reported. Of the five affected individuals over three generations, two had partial epilepsy in addition to EA1. The detailed clinical, electrophysiological and molecular genetic findings are presented. The heterozygous point mutation is located at nucleotide position 677 and results in a radical amino acid substitution at a highly conserved position in the second transmembrane domain of the Potassium Channel. Functional studies indicated that mutant subunits exhibited a dominant negative effect on Potassium Channel function and would be predicted to impair neuronal repolarization. Potassium Channels determine the excitability of neurons and blocking drugs are proconvulsant. A critical review of previously reported EA1 families shows an over-representation of epilepsy in family members with EA1 compared with unaffected members. These observations indicate that this mutation is pathogenic and suggest that the epilepsy in EA1 may be caused by the dysfunctional Potassium Channel. It is possible that such dysfunction may be relevant to other epilepsies in man.
Ronald B. Emeson - One of the best experts on this subject based on the ideXlab platform.
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Mutations underlying Episodic Ataxia type-1 antagonize Kv1.1 RNA editing.
Scientific Reports, 2017Co-Authors: Elizabeth A. Ferrick-kiddie, Joshua J. C. Rosenthal, Gregory D. Ayers, Ronald B. EmesonAbstract:: 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, myokymia, and increased prevalence of seizures. Three EA1 mutations, V404I, I407M, and V408A, are located within the RNA duplex structure required for RNA editing. Each mutation decreased RNA editing both in vitro and using an in vivo mouse model bearing the V408A allele. Editing of transcripts encoding mutant Channels affects numerous biophysical properties including Channel opening, closing, and inactivation. Thus EA1 symptoms could be influenced not only by the direct effects of the mutations on Channel properties, but also by their influence on RNA editing. These studies provide the first evidence that mutations associated with human genetic disorders can affect cis-regulatory elements to alter RNA editing.
Hsuanliang Liu - One of the best experts on this subject based on the ideXlab platform.
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molecular docking of the scorpion toxin tc1 to the structural model of the voltage gated Potassium Channel Kv1.1 from human homo sapiens
Journal of Biomolecular Structure & Dynamics, 2004Co-Authors: Hsuanliang Liu, Jinchung LinAbstract:In this study, structural model of the pore loop region of the voltage-gated Potassium Channel Kv1.1 from human Homo sapiens was constructed based on the crystallographic structure of KcsA by structural homology. The pore loop region of Kv1.1 exhibits similar folds as that of KcsA. The structural feature of the selectivity filter of Kv1.1 is nearly identical to that of KcsA, whereas most of the structural variations occur in the turret as well as in the inner and outer helices. Molecular docking experiments of the scorpion toxin Tc1 from Tityus cambridgei to the outer vestibule of KcsA as well as Kv1.1 were subsequently performed with various initial Tc1 orientations. Tc1 was found to form the most stable complexes with these two K+ Channels when the side chain of Lys14 occupies the pore of the selectivity filter through electrostatic interaction. Tc1 binds preferentially towards Kv1.1 than KcsA due to stronger hydrophobic and electrostatic interactions formed between the toxin and the selectivity filter and outer vestibule of Kv1.1. Furthermore, surface complementarity of the outer vestibules of the Channels to the Tc1 spatial conformations also plays an important role in stabilizing both the Tc1/KcsA and Tc1/Kv1.1 complexes.
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structural model of the voltage gated Potassium Channel Kv1.1 and molecular docking of tc1 toxin from tityus cambridgei to kcsa and Kv1.1
Chemical Physics Letters, 2003Co-Authors: Hsuanliang Liu, Jinchung LinAbstract:Abstract In this study, structural model of the pore loop region of the voltage-gated Potassium Channel Kv1.1 was constructed based on the crystallographic structure of KcsA. Subsequently, molecular docking experiments of Tc1 towards KcsA as well as Kv1.1 were performed. Tc1 forms the most stable complexes with these two Channels when the side chain of K14 occupies the first K + binding site. Tc1 binds preferentially towards Kv1.1 than KcsA due to the stronger electrostatic and hydrophobic interactions. Furthermore, surface complementarity of the outer vestibules of the Channel to the Tc1 spatial conformations also plays an important role in stabilizing these Tc1/Channel complexes.