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The Journal of General Physiology Dec 1998Expressed in Xenopus oocytes, KvLQT1 channel subunits yield a small, rapidly activating, voltage- dependent potassium conductance. When coexpressed with the minK gene... (Comparative Study)
Comparative Study
Expressed in Xenopus oocytes, KvLQT1 channel subunits yield a small, rapidly activating, voltage- dependent potassium conductance. When coexpressed with the minK gene product, a slowly activating and much larger potassium current results. Using fluctuation analysis and single-channel recordings, we have studied the currents formed by human KvLQT1 subunits alone and in conjunction with human or rat minK subunits. With low external K+, the single-channel conductances of these three channel types are estimated to be 0.7, 4.5, and 6.5 pS, respectively, based on noise analysis at 20 kHz bandwidth of currents at +50 mV. Power spectra computed over the range 0.1 Hz-20 kHz show a weak frequency dependence, consistent with current interruptions occurring on a broad range of time scales. The broad spectrum causes the apparent single-channel current value to depend on the bandwidth of the recording, and is mirrored in very "flickery" single-channel events of the channels from coexpressed KvLQT1 and human minK subunits. The increase in macroscopic current due to the presence of the minK subunit is accounted for by the increased apparent single-channel conductance it confers on the expressed channels. The rat minK subunit also confers the property that the outward single-channel current is increased by external potassium ions.
Topics: Amino Acid Sequence; Animals; Electric Conductivity; Female; Gene Expression; Humans; In Vitro Techniques; Ion Transport; KCNQ Potassium Channels; KCNQ1 Potassium Channel; Kinetics; Long QT Syndrome; Membrane Potentials; Molecular Sequence Data; Oocytes; Potassium; Potassium Channels; Potassium Channels, Voltage-Gated; Rats; Recombinant Proteins; Sequence Homology, Amino Acid; Xenopus
PubMed: 9834139
DOI: 10.1085/jgp.112.6.665 -
Expert Opinion on Therapeutic Targets Feb 2010Cardiovascular disease is a leading cause of death in modern societies. Hyperpolarizing Ca(2+)-activated K(+) channels (K(Ca)) are important membrane proteins in the... (Review)
Review
IMPORTANCE OF THE FIELD
Cardiovascular disease is a leading cause of death in modern societies. Hyperpolarizing Ca(2+)-activated K(+) channels (K(Ca)) are important membrane proteins in the control of arterial tone and pathological vascular remodelling and thus could serve as new drug targets.
AREAS COVERED IN THIS REVIEW
We summarize recent advances in the field of vascular K(Ca) and their roles in cardiovascular pathologies such as hypertension and restenosis disease and draw attention to novel small-molecule channel modulators and their possible therapeutic utility. This review focuses on literature from the last four to five years.
WHAT THE READER WILL GAIN
Pharmacological opening of endothelial KCa3.1/KCa2.3 channels stimulates endothelium-derived-hyperpolarizing-factor-mediated arteriolar dilation and lowers blood pressure. Inhibition of smooth muscle KCa3.1 channels has beneficial effects in restenosis disease and atherosclerosis. We consider the therapeutic potential of KCa3.1/KCa2.3 openers as novel endothelium-specific antihypertensive drugs as well as of KCa3.1-blockers for the treatment of pathological vascular remodelling and discuss advantages and disadvantages of the pharmacotherapeutic approaches.
TAKE HOME MESSAGE
Pharmacological manipulation of vascular K(Ca) channels by novel small-molecule modulators offers new venues for alternative treatments of hypertension, restenosis and atherosclerosis. Additional efforts are required to optimize these compounds and to validate them as cardiovascular-protective drugs.
Topics: Animals; Atherosclerosis; Biological Factors; Endothelium, Vascular; Humans; Hypertension; Intermediate-Conductance Calcium-Activated Potassium Channels; Large-Conductance Calcium-Activated Potassium Channel alpha Subunits; Potassium Channels, Calcium-Activated; Vascular Diseases; Vasodilation
PubMed: 20055714
DOI: 10.1517/14728220903540257 -
The Journal of Biological Chemistry Jul 2000We have isolated KCNQ5, a novel human member of the KCNQ potassium channel gene family that is differentially expressed in subregions of the brain and in skeletal...
We have isolated KCNQ5, a novel human member of the KCNQ potassium channel gene family that is differentially expressed in subregions of the brain and in skeletal muscle. When expressed in Xenopus oocytes, KCNQ5 generated voltage-dependent, slowly activating K(+)-selective currents that displayed a marked inward rectification at positive membrane voltages. KCNQ5 currents were insensitive to the K(+) channel blocker tetraethylammonium but were strongly inhibited by the selective M-current blocker linopirdine. Upon coexpression with the structurally related KCNQ3 channel subunit, current amplitudes increased 4-5-fold. Compared with homomeric KCNQ5 currents, KCNQ3/KCNQ5 currents also displayed slower activation kinetics and less inward rectification, indicating that KCNQ5 combined with KCNQ3 to form functional heteromeric channel proteins. This functional interaction between KCNQ5 and KCNQ3, a component of the M-channel, suggests that KCNQ5 may contribute to a diversity of heteromeric channels underlying native neuronal M-currents.
Topics: Amino Acid Sequence; Animals; Cloning, Molecular; Genetic Variation; Humans; Ion Transport; KCNQ Potassium Channels; Molecular Sequence Data; Neurons; Potassium; Potassium Channels; Potassium Channels, Voltage-Gated; Sequence Alignment; Xenopus
PubMed: 10787416
DOI: 10.1074/jbc.M002378200 -
The Journal of Biological Chemistry Apr 2024Despite significant advances in the development of therapeutic interventions targeting autoimmune diseases and chronic inflammatory conditions, lack of effective...
Despite significant advances in the development of therapeutic interventions targeting autoimmune diseases and chronic inflammatory conditions, lack of effective treatment still poses a high unmet need. Modulating chronically activated T cells through the blockade of the Kv1.3 potassium channel is a promising therapeutic approach; however, developing selective Kv1.3 inhibitors is still an arduous task. Phage display-based high throughput peptide library screening is a rapid and robust approach to develop promising drug candidates; however, it requires solid-phase immobilization of target proteins with their binding site preserved. Historically, the KcsA bacterial channel chimera harboring only the turret region of the human Kv1.3 channel was used for screening campaigns. Nevertheless, literature data suggest that binding to this type of chimera does not correlate well with blocking potency on the native Kv1.3 channels. Therefore, we designed and successfully produced advanced KcsA-Kv1.3, KcsA-Kv1.1, and KcsA-Kv1.2 chimeric proteins in which both the turret and part of the filter regions of the human Kv1.x channels were transferred. These T+F (turret-filter) chimeras showed superior peptide ligand-binding predictivity compared to their T-only versions in novel phage ELISA assays. Phage ELISA binding and competition results supported with electrophysiological data confirmed that the filter region of KcsA-Kv1.x is essential for establishing adequate relative affinity order among selected peptide toxins (Vm24 toxin, Hongotoxin-1, Kaliotoxin-1, Maurotoxin, Stichodactyla toxin) and consequently obtaining more reliable selectivity data. These new findings provide a better screening tool for future drug development efforts and offer insight into the target-ligand interactions of these therapeutically relevant ion channels.
Topics: Animals; Humans; Bacterial Proteins; Binding Sites; Kv1.3 Potassium Channel; Ligands; Peptide Library; Potassium Channel Blockers; Potassium Channels; Recombinant Fusion Proteins; Cell Line
PubMed: 38479597
DOI: 10.1016/j.jbc.2024.107155 -
Quarterly Reviews of Biophysics Nov 1998
Review
Topics: Animals; Humans; Multigene Family; Mutation; Potassium Channels; Potassium Channels, Voltage-Gated
PubMed: 10709243
DOI: 10.1017/s0033583599003467 -
Biochimica Et Biophysica Acta Nov 2002Two-pore domain K(+) (K2P) channels have been cloned from a variety of species and tissues. They have been characterised biophysically as a 'background' K(+)-selective... (Comparative Study)
Comparative Study Review
Two-pore domain K(+) (K2P) channels have been cloned from a variety of species and tissues. They have been characterised biophysically as a 'background' K(+)-selective conductance and are gated by pH, stretch, heat, coupling to G-proteins and anaesthetics. Whilst their precise physiological function is unknown, they are likely to represent an increasingly important family of membrane proteins.
Topics: Amino Acid Sequence; Anesthetics; Animals; Biosensing Techniques; Brain; Brain Chemistry; Cloning, Molecular; Electric Conductivity; Heart; Humans; Membrane Potentials; Membrane Proteins; Molecular Sequence Data; Myocardium; Nerve Tissue Proteins; Potassium Channels; Potassium Channels, Tandem Pore Domain; Protein Structure, Tertiary
PubMed: 12421546
DOI: 10.1016/s0005-2736(02)00597-7 -
Progress in Biophysics and Molecular... Oct 2004We describe the application of genetic programming, an evolutionary computing method, to predicting whether small molecules will block the HERG cardiac potassium... (Review)
Review
We describe the application of genetic programming, an evolutionary computing method, to predicting whether small molecules will block the HERG cardiac potassium channel. Models based on a molecular fragment-based descriptor set achieve an accuracy of 85-90% in predicting whether the IC(50) of a 'blind' set of compounds is <1 microM. Analysis of the models provides a 'meta-SAR', which predicts a pharmacophore of two hydrophobic features, one preferably aromatic and one preferably nitrogen-containing, with a protonatable nitrogen asymmetrically situated between them. Our experience of the approach suggests that it is robust, and requires limited scientist input to generate valuable predictive results and structural understanding of the target.
Topics: Animals; Binding Sites; Cation Transport Proteins; ERG1 Potassium Channel; Ether-A-Go-Go Potassium Channels; Heart; Humans; Models, Biological; Models, Molecular; Potassium Channels; Potassium Channels, Voltage-Gated; ROC Curve
PubMed: 15288759
DOI: 10.1016/j.pbiomolbio.2003.09.001 -
Kidney International Oct 1995Reabsorption of NaCl in the thick ascending limb of Henle's loop in the kidney and in the surface cells in the distal colon involves the integrated function of several... (Review)
Review
Reabsorption of NaCl in the thick ascending limb of Henle's loop in the kidney and in the surface cells in the distal colon involves the integrated function of several membrane transport systems including ion channels, the Na,K,Cl-cotransport system and the Na,K-pump. To determine if their properties are consistent with a role in regulation of transepithelial transport, Ca(2+)-activated K+ channels from the luminal membrane of the TAL cells and from the basolateral membrane of the distal colon cells have been characterized by flux studies in plasma membrane vesicle preparations and by single channel measurements in lipid bilayers. The channels are found to be activated by Ca2+ in the physiological range of concentration with a strong dependence on intracellular pH and the membrane potential. The Ca(2+)-sensitivity of the K+ channels is modulated by phosphorylation and dephosphorylation and the K+ channel protein must be in a phosphorylated state to respond to intracellular concentrations of Ca2+. As a step towards purification of the K+ channel proteins, procedures for solubilization and reconstitution of the K+ channels have been developed. The observation that the epithelial Ca(2+)-activated K+ channels bind calmodulin in the presence of Ca2+ have allowed for partial purification of the K+ channel proteins by calmodulin affinity chromatography. In the sequences for the two cloned Ca(2+)-activated K+ channels, the mSlo channel and the slowpoke channel, putative calmodulin binding regions can be identified.
Topics: Amino Acid Sequence; Animals; Binding Sites; Calcium; Calmodulin; Cell Membrane; Colon; Epithelium; Humans; Hydrogen-Ion Concentration; In Vitro Techniques; Large-Conductance Calcium-Activated Potassium Channel alpha Subunits; Large-Conductance Calcium-Activated Potassium Channels; Lipid Bilayers; Loop of Henle; Membrane Potentials; Molecular Sequence Data; Potassium Channels; Potassium Channels, Calcium-Activated
PubMed: 8569066
DOI: 10.1038/ki.1995.388 -
Cerebellum (London, England) 2003Potassium (K) channels have a key role in the regulation of neuronal excitability. Over a hundred different subunits encoding distinct K channel subtypes have been... (Review)
Review
Potassium (K) channels have a key role in the regulation of neuronal excitability. Over a hundred different subunits encoding distinct K channel subtypes have been identified so far. A major challenge is to relate these many different channel subunits to the functional K currents observed in native neurons. In this review, we have concentrated on cerebellar granule neurons (CGNs). We have considered each of the three principal super families of K channels in turn, namely, the six transmembrane domain, voltage-gated super family, the two transmembrane domain, inward-rectifier super family and the four transmembrane domain, leak channel super family. For each super family, we have identified the subunits that are expressed in CGNs and related the properties of these expressed channel subunits to the functional currents seen in electrophysiological recordings from these neurons. In some cases, there are strong molecular candidates for proteins underlying observed currents. In other cases the correlation is less clear. We show that at least 26 potassium channel alpha subunits are moderately or strongly expressed in CGNs. Nevertheless, a good empirical model of CGN function has been obtained with just six distinct K conductances. The transient KA current in CGNs, seems due to expression of Kv4.2 channels or Kv4.2/4.3 heteromers, while the KCa current is due to expression of large-conductance slo channels. The G-protein activated KIR current is probably due to heteromeric expression of KIR3.1 and KIR3.2. Perhaps KIR2.2 subunits underlie the KIR current when it is constitutively active. The leak conductance can be attributed to TASK-1 and or TASK-3 channels. With less certainty, the IK-slow current may be due to expression of one or more members of the KCNQ or EAG family. Lastly, the delayed-rectifier Kv current has as many as six different potential contributors from the extensive Kv family of alpha subunits. Since many of these subunits are highly regulated by neurotransmitters, physiological regulators and, often, auxiliary subunits, the resulting electrical properties of CGNs may be highly dynamic and subject to constant fine-tuning.
Topics: Animals; Cerebellum; Humans; Neurons; Potassium Channels
PubMed: 12882230
DOI: 10.1080/14734220310015593 -
FEBS Letters Jun 1999The superfamily of voltage-activated potassium channels may express structurally and functionally diverse voltage-activated potassium channels in the nervous system. The... (Review)
Review
The superfamily of voltage-activated potassium channels may express structurally and functionally diverse voltage-activated potassium channels in the nervous system. The roles of some voltage-activated potassium channel types, e.g. rapidly inactivating (transiently active type) channels and muscarine sensitive muscarine sensitive channels, are beginning to be understood. They may significantly influence dendritic action-potential back-propagation, signal to noise ratios in presynaptic excitability or the responsiveness of a neuron to synaptic input. Inherited disorders related to changes in excitability (episodic ataxia, epilepsy, heart arrhythmia) or to defects in sensory perception (hearing loss) have been associated with mutations in a few voltage-activated potassium channel genes. Most likely, more voltage-activated potassium channel genes will be linked to related disorders in the near future.
Topics: Animals; Humans; Ion Channel Gating; Potassium Channels
PubMed: 10376673
DOI: 10.1016/s0014-5793(99)00535-9