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Neuron Nov 2001Essential to nerve and muscle function, little is known about how potassium leak channels operate. KCNKØ opens and closes in a kinase-dependent fashion. Here, the...
Essential to nerve and muscle function, little is known about how potassium leak channels operate. KCNKØ opens and closes in a kinase-dependent fashion. Here, the transition is shown to correspond to changes in the outer aspect of the ion conduction pore. Voltage-gated potassium (VGK) channels open and close via an internal gate; however, they also have an outer pore gate that produces "C-type" inactivation. While KCNKØ does not inactivate, KCNKØ and VGK channels respond in like manner to outer pore blockers, potassium, mutations, and chemical modifiers. Structural relatedness is confirmed: VGK residues that come close during C-type gating predict KCNKØ sites that crosslink (after mutation to cysteine) to yield channels controlled by reduction and oxidization. We conclude that similar outer pore gates mediate KCNKØ opening and closing and VGK channel C-type inactivation despite their divergent structures and physiological roles.
Topics: Animals; Gene Deletion; Histidine; Ion Channel Gating; Mutagenesis; Oocytes; Potassium; Potassium Channel Blockers; Potassium Channels; Potassium Channels, Voltage-Gated; Protein Structure, Tertiary; Shaker Superfamily of Potassium Channels; Tetraethylammonium; Xenopus laevis; Zinc
PubMed: 11719204
DOI: 10.1016/s0896-6273(01)00503-7 -
Journal of Neurochemistry Sep 2003Necrotic insults such as seizure are excitotoxic. Logically, membrane hyperpolarization by increasing outwardly conducting potassium channel currents should attenuate...
Necrotic insults such as seizure are excitotoxic. Logically, membrane hyperpolarization by increasing outwardly conducting potassium channel currents should attenuate hyperexcitation and enhance neuron survival. Therefore, we overexpressed a small-conductance calcium-activated (SK2) or voltage-gated (Kv1.1) channel via viral vectors in cultured hippocampal neurons. We found that SK2 or Kv1.1 protected not only against kainate or glutamate excitotoxicity but also increased survival after sodium cyanide or staurosporine. In vivo overexpression of either channel in dentate gyrus reduced kainate-induced CA3 lesions. In hippocampal slices, the kainate-induced increase in granule cell excitability was reduced by overexpression of either channel, suggesting that these channels exert their protective effects during hyperexcitation. It is also important to understand any functional disturbances created by transgene overexpression alone. In the absence of insult, overexpression of Kv1.1, but not SK2, reduced baseline excitability in dentate gyrus granule cells. Furthermore, while no behavioral disturbances during spatial acquisition in the Morris water maze were observed with overexpression of either channel, animals overexpressing SK2, but not Kv1.1, exhibited a memory deficit post-training. This difference raises the possibility that the means by which these channel subtypes protect may differ. With further development, potassium channel vectors may be an effective pre-emptive strategy against necrotic insults.
Topics: Animals; Apoptosis; Cell Death; Cell Survival; Cells, Cultured; Dose-Response Relationship, Drug; Enzyme Inhibitors; Excitatory Amino Acid Agonists; Gene Expression; Genetic Therapy; Hippocampus; In Vitro Techniques; Kv1.1 Potassium Channel; Male; Maze Learning; Memory Disorders; Neurons; Potassium Channels; Potassium Channels, Calcium-Activated; Potassium Channels, Voltage-Gated; Rats; Rats, Sprague-Dawley; Small-Conductance Calcium-Activated Potassium Channels; Sodium Cyanide
PubMed: 12911616
DOI: 10.1046/j.1471-4159.2003.01880.x -
The Journal of Biological Chemistry Nov 2022Among voltage-gated potassium channel (K) isoforms, K1.6 is one of the most widespread in the nervous system. However, there are little data concerning its physiological...
Among voltage-gated potassium channel (K) isoforms, K1.6 is one of the most widespread in the nervous system. However, there are little data concerning its physiological significance, in part due to the scarcity of specific ligands. The known high-affinity ligands of K1.6 lack selectivity, and conversely, its selective ligands show low affinity. Here, we present a designer peptide with both high affinity and selectivity to K1.6. Previously, we have demonstrated that K isoform-selective peptides can be constructed based on the simplistic α-hairpinin scaffold, and we obtained a number of artificial Tk-hefu peptides showing selective blockage of K1.3 in the submicromolar range. We have now proposed amino acid substitutions to enhance their activity. As a result, we have been able to produce Tk-hefu-11 that shows an EC of ≈70 nM against K1.3. Quite surprisingly, Tk-hefu-11 turns out to block K1.6 with even higher potency, presenting an EC of ≈10 nM. Furthermore, we have solved the peptide structure and used molecular dynamics to investigate the determinants of selective interactions between artificial α-hairpinins and K channels to explain the dramatic increase in K1.6 affinity. Since K1.3 is not highly expressed in the nervous system, we hope that Tk-hefu-11 will be useful in studies of K1.6 and its functions.
Topics: Potassium Channels, Voltage-Gated; Amino Acid Sequence; Potassium Channel Blockers; Peptides; Ligands; Protein Isoforms; Kv1.3 Potassium Channel; Kv1.1 Potassium Channel; Kv1.2 Potassium Channel; Kv1.5 Potassium Channel
PubMed: 36087839
DOI: 10.1016/j.jbc.2022.102467 -
Beijing Da Xue Xue Bao. Yi Xue Ban =... Apr 2009ATP-sensitive potassium channel(K(ATP)) consists of a 4.4 complex of an inwardly rectifying Kir6.x pore plus a sulfonylurea receptor, which is an ATP-binding cassette... (Review)
Review
ATP-sensitive potassium channel(K(ATP)) consists of a 4.4 complex of an inwardly rectifying Kir6.x pore plus a sulfonylurea receptor, which is an ATP-binding cassette transporter. K(ATP) has been indentified in a variety of tissues and recognized as an important drug target. It connects cell metabolism with cell electric activity. K(ATP) has been proposed to play protective roles during heart failure, arrhythmia, myocardial infarction, stress, myocardial ischemia and hypertension. In this review, a summary of K(ATP) is presented with molecular structure, localization, regulation, cardiovascular protective effect and its mechanisms.
Topics: ATP-Binding Cassette Transporters; Cardiovascular Diseases; KATP Channels; Potassium Channels, Inwardly Rectifying; Receptors, Drug; Sulfonylurea Receptors
PubMed: 19377640
DOI: No ID Found -
Structure (London, England : 1993) Dec 1997kappa-PVIIA is a 27-residue polypeptide isolated from the venom of Conus purpurascens and is the first member of a new class of conotoxins that block potassium channels....
BACKGROUND
kappa-PVIIA is a 27-residue polypeptide isolated from the venom of Conus purpurascens and is the first member of a new class of conotoxins that block potassium channels. By comparison to other ion channels of eukaryotic cell membranes, voltage-sensitive potassium channels are relatively simple and methodology has been developed for mapping their interactions with small-peptide toxins. PVIIA, therefore, is a valuable new probe of potassium channel structure. This study of the solution structure and mode of channel binding of PVIIA forms the basis for mapping the interacting residues at the conotoxin-ion channel interface.
RESULTS
The three-dimensional structure of PVIIA resembles the triple-stranded beta sheet/cystine-knot motif formed by a number of toxic and inhibitory peptides. Subtle structural differences, predominantly in loops 2 and 4, are observed between PVIIA and other conotoxins with similar structural frameworks, however. Electrophysiological binding data suggest that PVIIA blocks channel currents by binding in a voltage-sensitive manner to the external vestibule and occluding the pore. Comparison of the electrostatic surface of PVIIA with that of the well-characterised potassium channel blocker charybdotoxin suggests a likely binding orientation for PVIIA.
CONCLUSIONS
Although the structure of PVIIA is considerably different to that of the alphaK scorpion toxins, it has a similar mechanism of channel blockade. On the basis of a comparison of the structures of PVIIA and charybdotoxin, we suggest that Lys19 of PVIIA is the residue which is responsible for physically occluding the pore of the potassium channel.
Topics: Amino Acid Sequence; Animals; Conotoxins; Electrophysiology; Magnetic Resonance Spectroscopy; Molecular Sequence Data; Mollusk Venoms; Oocytes; Patch-Clamp Techniques; Potassium Channel Blockers; Potassium Channels; Protein Binding; Protein Structure, Secondary; Solutions; Xenopus laevis
PubMed: 9438859
DOI: 10.1016/s0969-2126(97)00307-9 -
Proceedings of the National Academy of... Feb 2002The gating mechanism of the potassium channel KcsA was studied by normal mode analysis. The results provided an atomic description of the locations of the pivot points...
The gating mechanism of the potassium channel KcsA was studied by normal mode analysis. The results provided an atomic description of the locations of the pivot points and the motional features of key structural elements in the gating process. Two pivot points were found in the motions of the inner TM2 helical bundle that directly modulate the size of the central channel pore. One point is an intrasubunit hinge point that sharply divides the structural flexibility between the more rigid selectivity filter and the more mobile peripheral transmembrane helices. Such a division is vital for KcsA because it permits the large-scale motions of transmembrane helices required for the gating and, in the meantime, maintains the rigidity of the filter region essential for the selectivity. The other pivot point is an intersubunit one at which all four TM2 helices are bundled together. During the gating process, each TM2 helix undergoes a lever-like swinging motion pivoting on the intrasubunit hinge, and the entire TM2 bundle undergoes a concerted rotational motion around the central channel axis constrained around the intersubunit bundle point. This series of motions leads to a dramatic enlargement of the intracellular gate without loosening up the structural integrity.
Topics: Bacterial Proteins; Electron Spin Resonance Spectroscopy; Hydrogen-Ion Concentration; Ions; Models, Molecular; Potassium; Potassium Channels; Protein Binding; Protein Conformation; Protein Structure, Secondary; Software
PubMed: 11842204
DOI: 10.1073/pnas.042650399 -
FEBS Letters Jul 2002We report the molecular cloning from foetal brain of the human potassium channel heag2. The cDNA encodes a protein of 988 amino acids, 73% identical to heag1. Heag2 is...
We report the molecular cloning from foetal brain of the human potassium channel heag2. The cDNA encodes a protein of 988 amino acids, 73% identical to heag1. Heag2 is expressed in the brain, but is also found in a range of tissues including skeletal muscle. In oocytes, the channel is a non-inactivating outward rectifier, with dependence of activation rate on holding potential. Compared with heag1, the conductance-voltage curve for heag2 was shifted to the left, the voltage sensitivity was less, activation kinetics were different, and the sensitivity to terfenadine was lower. The heag2 channel may have important physiological roles.
Topics: Amino Acid Sequence; Base Sequence; Cloning, Molecular; DNA Primers; DNA, Complementary; Ether-A-Go-Go Potassium Channels; Humans; Molecular Sequence Data; Potassium Channels; Potassium Channels, Voltage-Gated; RNA; Reverse Transcriptase Polymerase Chain Reaction; Sequence Homology, Amino Acid
PubMed: 12135768
DOI: 10.1016/s0014-5793(02)03055-7 -
Structure (London, England : 1993) Aug 2012The voltage-gated potassium channel Kv7.1 and its auxiliary subunit KCNE1 are expressed in the heart and give rise to the major repolarization current. The interaction...
The voltage-gated potassium channel Kv7.1 and its auxiliary subunit KCNE1 are expressed in the heart and give rise to the major repolarization current. The interaction of Kv7.1 with the single transmembrane helix of KCNE1 considerably slows channel activation and deactivation, raises single-channel conductance, and prevents slow voltage-dependent inactivation. We built a Kv7.1-KCNE1 model-structure. The model-structure agrees with previous disulfide mapping studies and enables us to derive molecular interpretations of electrophysiological recordings that we obtained for two KCNE1 mutations. An elastic network analysis of Kv7.1 fluctuations in the presence and absence of KCNE1 suggests a mechanistic perspective on the known effects of KCNE1 on Kv7.1 function: slow deactivation is attributed to the low mobility of the voltage-sensor domains upon KCNE1 binding, abolishment of voltage-dependent inactivation could result from decreased fluctuations in the external vestibule, and amalgamation of the fluctuations in the pore region is associated with enhanced ion conductivity.
Topics: Computer Simulation; Conserved Sequence; Humans; KCNQ1 Potassium Channel; Models, Molecular; Mutation, Missense; Potassium Channels, Voltage-Gated; Protein Structure, Quaternary; Protein Structure, Secondary; Protein Structure, Tertiary; Structural Homology, Protein
PubMed: 22771213
DOI: 10.1016/j.str.2012.05.016 -
Current Biology : CB Sep 2019Primary electroencephalographic (EEG) features of sleep arise in part from thalamocortical neural assemblies, and cortical potassium channels have long been thought to...
Primary electroencephalographic (EEG) features of sleep arise in part from thalamocortical neural assemblies, and cortical potassium channels have long been thought to play a critical role. We have exploited the regionally dynamic nature of sleep EEG to develop a novel screening strategy and used it to conduct an adeno-associated virus (AAV)-mediated RNAi screen for cellular roles of 31 different voltage-gated potassium channels in modulating cortical EEG features across the circadian sleep-wake cycle. Surprisingly, a majority of channels modified only electroencephalographic frequency bands characteristic of sleep, sometimes diurnally or even in specific vigilance states. Confirming our screen for one channel, we show that depletion of the KCa1.1 (or "BK") channel reduces EEG power in slow-wave sleep by slowing neuronal repolarization. Strikingly, this reduction completely abolishes transcriptomic changes between sleep and wake. Thus, our data establish an unexpected connection between transcription and EEG power controlled by specific potassium channels. We postulate that additive dynamic roles of individual potassium channels could integrate different influences upon sleep and wake within single neurons.
Topics: Animals; Brain; Cerebral Cortex; Circadian Rhythm; Electroencephalography; Humans; Large-Conductance Calcium-Activated Potassium Channel alpha Subunits; Male; Mice; Mice, Inbred C57BL; Neurons; Potassium Channels; Potassium Channels, Voltage-Gated; Sleep; Wakefulness
PubMed: 31474531
DOI: 10.1016/j.cub.2019.07.056 -
The EMBO Journal Jul 2009Voltage-gated K(+) channels co-assemble with auxiliary beta subunits to form macromolecular complexes. In heart, assembly of Kv7.1 pore-forming subunits with KCNE1 beta...
Voltage-gated K(+) channels co-assemble with auxiliary beta subunits to form macromolecular complexes. In heart, assembly of Kv7.1 pore-forming subunits with KCNE1 beta subunits generates the repolarizing K(+) current I(KS). However, the detailed nature of their interface remains unknown. Mutations in either Kv7.1 or KCNE1 produce the life-threatening long or short QT syndromes. Here, we studied the interactions and voltage-dependent motions of I(KS) channel intracellular domains, using fluorescence resonance energy transfer combined with voltage-clamp recording and in vitro binding of purified proteins. The results indicate that the KCNE1 distal C-terminus interacts with the coiled-coil helix C of the Kv7.1 tetramerization domain. This association is important for I(KS) channel assembly rules as underscored by Kv7.1 current inhibition produced by a dominant-negative C-terminal domain. On channel opening, the C-termini of Kv7.1 and KCNE1 come close together. Co-expression of Kv7.1 with the KCNE1 long QT mutant D76N abolished the K(+) currents and gated motions. Thus, during channel gating KCNE1 is not static. Instead, the C-termini of both subunits experience molecular motions, which are disrupted by the D76N causing disease mutation.
Topics: Animals; Cell Line; Fluorescence Resonance Energy Transfer; Humans; Immunoprecipitation; KCNQ1 Potassium Channel; Oocytes; Potassium Channels, Voltage-Gated; Protein Interaction Domains and Motifs; Xenopus
PubMed: 19521339
DOI: 10.1038/emboj.2009.157