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1
Reichenbach, Andreas, Andre Henke, Wolfgang Eberhardt, Winfried Reichelt, and Dietrich Dettmer. "K+ ion regulation in retina." Canadian Journal of Physiology and Pharmacology 70, S1 (May 15, 1992): S239—S247. http://dx.doi.org/10.1139/y92-267.
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During onset and offset of illumination, considerable changes in extracellular K+ concentration ([K+]e) occur within particular retinal layers. There are two ways in which glial cells may control [K+]e: (1) by space-independent processes, for example, by K+ uptake due to the Na+–K+ ATPase, and (2) by space-dependent processes, that is, by spatial buffering currents flowing through K+ channels. Rabbit retinal Müller (glial) cells were studied for expression of mechanisms supporting both kinds of processes. This review demonstrates that rabbit Müller cells have Na–K pumps whose distribution and properties are highly adapted to meet the needs of efficient K+ clearance. Furthermore, spatial buffering currents through specialized K+ channels of Müller cells greatly accelerate retinal K+ clearance during and after stimulation.Key words: glia, retina, potassium clearance, sodium–potassium pump, potassium channels.
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ZHONG, YI-SHENG, JING WANG, WANG-MIN LIU, and YI-HUA ZHU. "Potassium ion channels in retinal ganglion cells (Review)." Molecular Medicine Reports 8, no. 2 (June 4, 2013): 311–19. http://dx.doi.org/10.3892/mmr.2013.1508.
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Pramudita, James C., Vanessa K. Peterson, Justin A. Kimpton, and Neeraj Sharma. "Potassium-ion intercalation in graphite within a potassium-ion battery examined usingin situX-ray diffraction." Powder Diffraction 32, S2 (September 4, 2017): S43—S48. http://dx.doi.org/10.1017/s0885715617000902.
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Graphite has been widely used as a negative electrode material in lithium-ion batteries, and recently it has attracted attention for its use in potassium-ion batteries. In this study, the firstin situX-ray diffraction characterisation of a K/graphite electrochemical cell is performed. Various graphite intercalation compounds are found, including the stage three KC36and stage one KC8compounds,along with the disappearance of the graphite during the potassiation process. These results show new insights on the non-equilibrium states of potassium-ion intercalation into graphite in K/graphite electrochemical cells.
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Van Mil, H. G. J. "Analysis of a Model Describing the Dynamics of Intracellular Ion Composition in Biological Cells." International Journal of Bifurcation and Chaos 08, no. 05 (May 1998): 1043–47. http://dx.doi.org/10.1142/s0218127498000851.
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An electrophysiological model describing the dynamics of the intracellular ion concentration and the membrane potential (Vm) in biological cells is presented. The model links passive ion fluxes through channels of sodium, potassium and chloride to active ion fluxes generated by the sodium potassium pump. To model the interaction of Vm to the ionic fluxes Kirchhoff current law is used. Only one Vm-dependent permeability as represented by an inwardly rectifying potassium channel (IKR) is incorporated. It is shown that the resulting system of ordinary differential equations is degenerate. Decomposition of the system into noninteracting subsystems allows a dynamically independent description of the currents of sodium and potassium in relation to Vm. Physical and mathematical arguments for the decomposition into subsystems are presented. Analysis of the model show hysteresis properties that can account for the experimentally-observed bistability in skeletal and heart muscles fibers.
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Quraishi, Imran H., and Robert M. Raphael. "Computational model of vectorial potassium transport by cochlear marginal cells and vestibular dark cells." American Journal of Physiology-Cell Physiology 292, no. 1 (January 2007): C591—C602. http://dx.doi.org/10.1152/ajpcell.00560.2005.
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Cochlear marginal cells and vestibular dark cells transport potassium into the inner ear endolymph, a potassium-rich fluid, the homeostasis of which is essential for hearing and balance. We have formulated an integrated mathematical model of ion transport across these epithelia that incorporates the biophysical properties of the major ion transporters and channels located in the apical and basolateral membranes of the constituent cells. The model is constructed for both open- and short-circuit situations to test the extremes of functional capacity of the epithelium and predicts the steady-state voltages, ion concentrations, and transepithelial currents as a function of various transporter and channel densities. We validate the model by establishing that the cells are capable of vectorial ion transport consistent with several experimental measurements. The model indicates that cochlear marginal cells do not make a significant direct contribution to the endocochlear potential and illustrates how changes to the activity of specific transport proteins lead to reduced K+ flux across the marginal and dark cell layers. In particular, we investigate the mechanisms of loop diuretic ototoxicity and diseases with hearing loss in which K+ and Cl− transport are compromised, such as Jervell and Lange-Nielsen syndrome and Bartter syndrome, type IV, respectively. Such simulations demonstrate the utility of compartmental modeling in investigating the role of ion homeostasis in inner ear physiology and pathology.
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Cho, Youngtak, Viet Anh Pham Ba, Jin-Young Jeong, Yoonji Choi, and Seunghun Hong. "Ion-Selective Carbon Nanotube Field-Effect Transistors for Monitoring Drug Effects on Nicotinic Acetylcholine Receptor Activation in Live Cells." Sensors 20, no. 13 (June 30, 2020): 3680. http://dx.doi.org/10.3390/s20133680.
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We developed ion-selective field-effect transistor (FET) sensors with floating electrodes for the monitoring of the potassium ion release by the stimulation of nicotinic acetylcholine receptors (nAChRs) on PC12 cells. Here, ion-selective valinomycin-polyvinyl chloride (PVC) membranes were coated on the floating electrode-based carbon nanotube (CNT) FETs to build the sensors. The sensors could selectively measure potassium ions with a minimum detection limit of 1 nM. We utilized the sensor for the real-time monitoring of the potassium ion released from a live cell stimulated by nicotine. Notably, this method also allowed us to quantitatively monitor the cell responses by agonists and antagonists of nAChRs. These results suggest that our ion-selective CNT-FET sensor has potential uses in biological and medical researches such as the monitoring of ion-channel activity and the screening of drugs.
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Hedrich, Rainer. "Ion Channels in Plants." Physiological Reviews 92, no. 4 (October 2012): 1777–811. http://dx.doi.org/10.1152/physrev.00038.2011.
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Since the first recordings of single potassium channel activities in the plasma membrane of guard cells more than 25 years ago, patch-clamp studies discovered a variety of ion channels in all cell types and plant species under inspection. Their properties differed in a cell type- and cell membrane-dependent manner. Guard cells, for which the existence of plant potassium channels was initially documented, advanced to a versatile model system for studying plant ion channel structure, function, and physiology. Interestingly, one of the first identified potassium-channel genes encoding the Shaker-type channel KAT1 was shown to be highly expressed in guard cells. KAT1-type channels from Arabidopsis thaliana and its homologs from other species were found to encode the K+-selective inward rectifiers that had already been recorded in early patch-clamp studies with guard cells. Within the genome era, additional Arabidopsis Shaker-type channels appeared. All nine members of the Arabidopsis Shaker family are localized at the plasma membrane, where they either operate as inward rectifiers, outward rectifiers, weak voltage-dependent channels, or electrically silent, but modulatory subunits. The vacuole membrane, in contrast, harbors a set of two-pore K+ channels. Just very recently, two plant anion channel families of the SLAC/SLAH and ALMT/QUAC type were identified. SLAC1/SLAH3 and QUAC1 are expressed in guard cells and mediate Slow- and Rapid-type anion currents, respectively, that are involved in volume and turgor regulation. Anion channels in guard cells and other plant cells are key targets within often complex signaling networks. Here, the present knowledge is reviewed for the plant ion channel biology. Special emphasis is drawn to the molecular mechanisms of channel regulation, in the context of model systems and in the light of evolution.
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CORREIA, MANNING J., KATHERINE J. RENNIE, and PAUL KOO. "Return of Potassium Ion Channels in Regenerated Hair Cells." Annals of the New York Academy of Sciences 942, no. 1 (January 25, 2006): 228–40. http://dx.doi.org/10.1111/j.1749-6632.2001.tb03749.x.
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Berkowitz, L. R., and E. P. Orringer. "Passive sodium and potassium movements in sickle erythrocytes." American Journal of Physiology-Cell Physiology 249, no. 3 (September 1, 1985): C208—C214. http://dx.doi.org/10.1152/ajpcell.1985.249.3.c208.
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Deoxygenation causes an increase in passive Na and K movements across the membrane of the sickle erythrocyte. Some investigators find that these ion movements are accompanied by cell dehydration, while others find no evidence for cell water loss with sickling. Because gelation of hemoglobin S would be enhanced by cell water loss, we reinvestigated Na and K movements in sickle cells to define further the role that ion movements might play in the pathogenesis of sickling. With deoxygenation, we found that sickle cells gained Na and lost K without losing cell water. These net ion movements were not seen in control red blood cells. For sickle cells, deoxygenation also increased passive unidirectional influxes of Na and K, effects not observed when control red blood cells were deoxygenated. The deoxygenation-induced passive influxes of Na and K in sickle cells were not diminished by anion substitution or by the addition of the diuretic furosemide. We also found differences in passive Na and K fluxes between oxygenated sickle cells and normal red blood cells. The addition of furosemide or replacement of Cl with NO3 or SCN, maneuvers that largely reduced passive Na and K movements in oxygenated normal cells, had no effect on Na and K movements in oxygenated sickle cells. These findings militate against the idea that solute and water loss occur as a consequence of deoxygenation but do indicate that there are acquired membrane abnormalities in sickle red blood cells.
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Younes, Samar, Nisreen Mourad, Mohamed Salla, Mohamad Rahal, and Dalal Hammoudi Halat. "Potassium Ion Channels in Glioma: From Basic Knowledge into Therapeutic Applications." Membranes 13, no. 4 (April 15, 2023): 434. http://dx.doi.org/10.3390/membranes13040434.
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Ion channels, specifically those controlling the flux of potassium across cell membranes, have recently been shown to exhibit an important role in the pathophysiology of glioma, the most common primary central nervous system tumor with a poor prognosis. Potassium channels are grouped into four subfamilies differing by their domain structure, gating mechanisms, and functions. Pertinent literature indicates the vital functions of potassium channels in many aspects of glioma carcinogenesis, including proliferation, migration, and apoptosis. The dysfunction of potassium channels can result in pro-proliferative signals that are highly related to calcium signaling as well. Moreover, this dysfunction can feed into migration and metastasis, most likely by increasing the osmotic pressure of cells allowing the cells to initiate the “escape” and “invasion” of capillaries. Reducing the expression or channel blockage has shown efficacy in reducing the proliferation and infiltration of glioma cells as well as inducing apoptosis, priming several approaches to target potassium channels in gliomas pharmacologically. This review summarizes the current knowledge on potassium channels, their contribution to oncogenic transformations in glioma, and the existing perspectives on utilizing them as potential targets for therapy.
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Schwab, Albrecht, Peter Hanley, Anke Fabian, and Christian Stock. "Potassium Channels Keep Mobile Cells on the Go." Physiology 23, no. 4 (August 2008): 212–20. http://dx.doi.org/10.1152/physiol.00003.2008.
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Cell motility is a prerequisite for the creation of new life, and it is required for maintaining the integrity of an organism. Under pathological conditions, “too much” motility may cause premature death. Studies over the past few years have revealed that ion channels are essential for cell motility. This review highlights the importance of K+ channels in regulating cell motility.
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Cragg, Peter J. "Artificial Transmembrane Channels for Sodium and Potassium." Science Progress 85, no. 3 (August 2002): 219–41. http://dx.doi.org/10.3184/003685002783238780.
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Transport of alkali metals, particularly sodium and potassium, across cell membranes is an essential function performed by special proteins that enable cells to regulate inter- and extracellular ion concentrations with exceptional selectivity. The importance of these channel-forming proteins has led to researchers emulating of their structural features: an ion-specific filter and conduction at rates up to 108 ions per second. Synthetic helical and cyclic polypeptides form channels, however, the specificity of ion transport is often low. Ion-specific macrocycles have been used as filters from which membrane-spanning derivatives have been prepared. Success has been limited as many compounds act as ion carriers rather than forming transmembrane channels. Surfactant compounds also allow ions to cross membranes but any specificity is serendipitous. Overall it seems possible to mimic either ion specificity or efficient transmembrane ion transport. The goal for the future will be to combine both characteristics in one artificial system.
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Beacham, Daniel W., Trillium Blackmer, Michael O’ Grady, and George T. Hanson. "Cell-Based Potassium Ion Channel Screening Using the FluxOR™ Assay." Journal of Biomolecular Screening 15, no. 4 (March 5, 2010): 441–46. http://dx.doi.org/10.1177/1087057109359807.
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FluxOR™ technology is a cell-based assay used for high-throughput screening measurements of potassium channel activity. Using thallium influx as a surrogate indicator of potassium ion channel activity, the FluxOR™ Potassium Ion Channel Assay is based on the activation of a novel fluorescent dye. This indicator reports channel activity with a large fluorogenic response and is proportional to the number of open potassium channels on the cell, making it extremely useful for studying K+ channel targets. In contrast to BTC-AM ester, FluxOR™ dye is roughly 10-fold more thallium sensitive, requiring much lower thallium for a larger signal window. This also means that the assay is carried out in a physiological, normal-chloride saline. In this article, the authors describe how they used BacMam gene delivery to express Kv7.2 and 7.3 (KCNQ), Kir2.1, or Kv11.1 (hERG) potassium ion channels in U2-OS cells. Using these cells, they ran the FluxOR™ assay to identify and characterize channel-specific inhibitory compounds discovered within the library (Tocriscreen™ Mini 1200 and Sigma Sodium/Potassium Modulators Ligand set). The FluxOR™ assay was able to identify several known specific inhibitors of Kv7.2/7.3 or hERG, highlighting its potential to identify novel and more efficacious small-molecule modulators.
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Pleinis, John M., Logan Norrell, Radha Akella, John M. Humphreys, Haixia He, Qifei Sun, Feng Zhang, et al. "WNKs are potassium-sensitive kinases." American Journal of Physiology-Cell Physiology 320, no. 5 (May 1, 2021): C703—C721. http://dx.doi.org/10.1152/ajpcell.00456.2020.
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With no lysine (K) (WNK) kinases regulate epithelial ion transport in the kidney to maintain homeostasis of electrolyte concentrations and blood pressure. Chloride ion directly binds WNK kinases to inhibit autophosphorylation and activation. Changes in extracellular potassium are thought to regulate WNKs through changes in intracellular chloride. Prior studies demonstrate that in some distal nephron epithelial cells, intracellular potassium changes with chronic low- or high-potassium diet. We, therefore, investigated whether potassium regulates WNK activity independent of chloride. We found decreased activity of Drosophila WNK and mammalian WNK3 and WNK4 in fly Malpighian (renal) tubules bathed in high extracellular potassium, even when intracellular chloride was kept constant at either ∼13 mM or 26 mM. High extracellular potassium also inhibited chloride-insensitive mutants of WNK3 and WNK4. High extracellular rubidium was also inhibitory and increased tubule rubidium. The Na+/K+-ATPase inhibitor, ouabain, which is expected to lower intracellular potassium, increased tubule Drosophila WNK activity. In vitro, potassium increased the melting temperature of Drosophila WNK, WNK1, and WNK3 kinase domains, indicating ion binding to the kinase. Potassium inhibited in vitro autophosphorylation of Drosophila WNK and WNK3, and also inhibited WNK3 and WNK4 phosphorylation of their substrate, Ste20-related proline/alanine-rich kinase (SPAK). The greatest sensitivity of WNK4 to potassium occurred in the range of 80–180 mM, encompassing physiological intracellular potassium concentrations. Together, these data indicate chloride-independent potassium inhibition of Drosophila and mammalian WNK kinases through direct effects of potassium ion on the kinase.
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Fox, J. A., B. A. Pfeffer, and G. L. Fain. "Single-channel recordings from cultured human retinal pigment epithelial cells." Journal of General Physiology 91, no. 2 (February 1, 1988): 193–222. http://dx.doi.org/10.1085/jgp.91.2.193.
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We have applied patch-clamp techniques to on-cell and excised-membrane patches from human retinal pigment epithelial cells in tissue culture. Single-channel currents from at least four ion channel types were observed: three or more potassium-selective channels with single-channel slope conductances near 100, 45, and 25 pS as measured in on-cell patches with physiological saline in the pipette, and a relatively nonselective channel with subconductance states, which has a main-state conductance of approximately 300 pS at physiological ion concentrations. The permeability ratios, PK/PNa, measured in excised patches were 21 for the 100-pS channels, 3 for the 25-pS channels, and 0.8 for the 300-pS nonselective channel. The 45-pS channels appeared to be of at least two types, with PK/PNa's of approximately 41 for one type and 3 for the other. The potassium-selective channels were spontaneously active at all potentials examined. The average open time for these channels ranged from a few milliseconds to many tens of milliseconds. No consistent trend relating potassium-selective channel kinetics to membrane potential was apparent, which suggests that channel activity was not regulated by the membrane potential. In contrast to the potassium-selective channels, the activity of the nonselective channel was voltage dependent: the open probability of this channel declined to low values at large positive or negative membrane potentials and was maximal near zero. Single-channel conductances observed at several symmetrical KCl concentrations have been fitted with Michaelis-Menten curves in order to estimate maximum channel conductances and ion-binding constants for the different channel types. The channels we have recorded are probably responsible for the previously observed potassium permeability of the retinal pigment epithelium apical membrane.
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Hambleton, T. A., J. R. Bourke, G. J. Huxham, and S. W. Manley. "Sodium dependence of the thyrotrophin-induced depolarization in cultured porcine thyroid cells." Journal of Endocrinology 108, no. 2 (February 1986): 225–30. http://dx.doi.org/10.1677/joe.0.1080225.
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ABSTRACT Cultured porcine thyroid cells exhibit a resting membrane potential of about − 73 mV and depolarize to about − 54 mV on exposure to TSH. The depolarizing response to TSH was preserved in a medium consisting only of inorganic salts and buffers, but was abolished in sodium-free medium, demonstrating dependence on an inward sodium current. Increasing the potassium concentration of the medium resulted in a reduction in the resting membrane potential of 60 mV per tenfold change in potassium concentration, and a diminished TSH response. A hyperpolarizing TSH response was observed in a sodium- and bicarbonate-free medium, indicating that a hyperpolarizing ion current (probably carried by potassium) was also enhanced in the presence of TSH. Tetrodotoxin blocked the TSH response. We conclude that the response of the thyroid cell membrane to TSH involves increases in permeability to sodium and potassium, and that the thyroid membrane ion channels bear some similarity to the voltage-dependent sodium channels of excitable tissues, despite the absence of action potentials in the thyroid. J. Endocr. (1986) 108, 225–230
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Herranz, Carmen, Luis M. Cintas, Pablo E. Hernández, Gert N. Moll, and Arnold J. M. Driessen. "Enterocin P Causes Potassium Ion Efflux from Enterococcus faecium T136 Cells." Antimicrobial Agents and Chemotherapy 45, no. 3 (March 1, 2001): 901–4. http://dx.doi.org/10.1128/aac.45.3.901-904.2001.
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ABSTRACT Enterocin P is a bacteriocin produced by Enterococcus faecium P13. We studied the mechanism of its bactericidal action using enterocin-P-sensitive E. faecium T136 cells. The bacteriocin is incapable of dissipating the transmembrane pH gradient. On the other hand, depending on the buffer used, enterocin P dissipates the transmembrane potential. Enterocin P efficiently elicits efflux of potassium ions, but not of intracellularly accumulated anions like phosphate and glutamate. Taken together, these data demonstrate that enterocin P forms specific, potassium ion-conducting pores in the cytoplasmic membrane of target cells.
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Ubels, John L., Rachel E. Van Dyken, Julienne R. Louters, Mark P. Schotanus, and Loren D. Haarsma. "Potassium ion fluxes in corneal epithelial cells exposed to UVB." Experimental Eye Research 92, no. 5 (May 2011): 425–31. http://dx.doi.org/10.1016/j.exer.2011.02.019.
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Harjes, Daniel I., J. Matthew Dubach, Anthony Rosenzweig, Saumya Das, and Heather A. Clark. "Ion-Selective Optodes Measure Extracellular Potassium Flux in Excitable Cells." Macromolecular Rapid Communications 31, no. 2 (August 13, 2009): 217–21. http://dx.doi.org/10.1002/marc.200900297.
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Russell, John M. "Sodium-Potassium-Chloride Cotransport." Physiological Reviews 80, no. 1 (January 1, 2000): 211–76. http://dx.doi.org/10.1152/physrev.2000.80.1.211.
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Obligatory, coupled cotransport of Na+, K+, and Cl− by cell membranes has been reported in nearly every animal cell type. This review examines the current status of our knowledge about this ion transport mechanism. Two isoforms of the Na+-K+-Cl− cotransporter (NKCC) protein (∼120–130 kDa, unglycosylated) are currently known. One isoform (NKCC2) has at least three alternatively spliced variants and is found exclusively in the kidney. The other (NKCC1) is found in nearly all cell types. The NKCC maintains intracellular Cl− concentration ([Cl−]i) at levels above the predicted electrochemical equilibrium. The high [Cl−]i is used by epithelial tissues to promote net salt transport and by neural cells to set synaptic potentials; its function in other cells is unknown. There is substantial evidence in some cells that the NKCC functions to offset osmotically induced cell shrinkage by mediating the net influx of osmotically active ions. Whether it serves to maintain cell volume under euvolemic conditons is less clear. The NKCC may play an important role in the cell cycle. Evidence that each cotransport cycle of the NKCC is electrically silent is discussed along with evidence for the electrically neutral stoichiometries of 1 Na+:1 K+:2 Cl− (for most cells) and 2 Na+:1 K+:3 Cl− (in squid axon). Evidence that the absolute dependence on ATP of the NKCC is the result of regulatory phosphorylation/dephosphorylation mechanisms is decribed. Interestingly, the presumed protein kinase(s) responsible has not been identified. An unusual form of NKCC regulation is by [Cl−]i. [Cl−]i in the physiological range and above strongly inhibits the NKCC. This effect may be mediated by a decrease of protein phosphorylation. Although the NKCC has been studied for ∼20 years, we are only beginning to frame the broad outlines of the structure, function, and regulation of this ubiquitous ion transport mechanism.
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Rane, S. G. "A Ca2(+)-activated K+ current in ras-transformed fibroblasts is absent from nontransformed cells." American Journal of Physiology-Cell Physiology 260, no. 1 (January 1, 1991): C104—C112. http://dx.doi.org/10.1152/ajpcell.1991.260.1.c104.
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Biochemical similarities between ras proteins and the GTP-binding proteins and correlation of ras-induced cell transformation with altered transmembrane cation fluxes indicate that ras proteins may act to modulate ion channel activity. To test this idea, whole cell, tight-seal, patch-clamp recording was used to compare macroscopic currents of ras-transformed fibroblasts with currents of their nontransformed counterparts. A prominent calcium-activated, voltage-independent potassium current was observed in 83-100% of cells from three separate fibroblast lines transformed by two different oncogenic ras alleles, whereas the same current was present at much smaller amplitudes in only 0-15% of nontransformed cells. The calcium-activated potassium current is blocked by charybdotoxin and by concentrations of tetraethylammonium above 1 mM, but it is insensitive to apamin. Both normal and ras-transformed cells have another calcium-activated current that is not potassium selective, and, consistent with other studies, normal cells display a voltage-activated calcium conductance. These results suggest that the mechanisms by which ras triggers or maintains cell transformation may involve alterations in the number or activity of certain ion channels, in particular, a type of calcium-activated potassium channel.
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Aditya, Grahita, Hikmah Nuraini, and Whinahyu Aji Sekarini. "Pengaruh Material Konservasi Kolostrum terhadap Pelepasan Ion Ni." Jurnal Teknosains 9, no. 1 (December 22, 2019): 12. http://dx.doi.org/10.22146/teknosains.37727.
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Nickel in orthodontic bracket will be released immediately in the oral cavity. The release of Ni ion may trigger type IV hypersensitivity reaction. Colostrum has a high content of lactoferrin which can inhibit T cells proliferation after nickel sensitization, and decrease oxidative stress. Adding potassium sorbat 0.5%, or fermentation of colostrum may extend colostrum storage. The purpose of this research is to know the difference of nickel ion release in colostrum with 0.5% potassium sorbat addition and fermented colostrum. Methods of the study were laboratory experimental with four groups, colostrum and 0.5% potassium sorbat, fermented colostrum, sodium fluoride and artificial saliva. The sample was incubated in 40°C for 7 days. Nickel ions was measured using an inductively coupled plasma-optical emission spectrophotometry (ICP-OES Perlun Elmer Optima 8300®). Ni ions release differences were tested using the Kruskall-Wallis and Mann Whitney test.The lowest rate of Ni ion release wasfound in the colostrum group with 0.5% potassium sorbat followed by the fermented colostrum group. Kruskal-Wallis test no significant difference (p> 0,05) in each study group. The Mann Whitney test found significant differences between colostrum solution with 0.5% potassium sorbat and sodium fluoride, and also artificial saliva. The results concluded that colostrum with 0.5% potassium sorbat inhibit the release of Ni ions.
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White, H. Steve, Sien Yao Chow, Y. C. Yen-Chow, and Dixon M. Woodbury. "Effect of elevated potassium on the ion content of mouse astrocytes and neurons." Canadian Journal of Physiology and Pharmacology 70, S1 (May 15, 1992): S263—S268. http://dx.doi.org/10.1139/y92-271.
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Potassium is tightly regulated within the extracellular compartment of the brain. Nonetheless, it can increase 3- to 4-fold during periods of intense seizure activity and 10- to 20-fold under certain pathological conditions such as spreading depression. Within the central nervous system, neurons and astrocytes are both affected by shifts in the extracellular concentration of potassium. Elevated potassium can lead to a redistribution of other ions (e.g., calcium, sodium, chloride, hydrogen, etc.) within the cellular compartment of the brain. Small shifts in the extracellular potassium concentration can markedly affect acid–base homeostasis, energy metabolism, and volume regulation of these two brain cells. Since normal neuronal function is tightly coupled to the ability of the surrounding glial cells to regulate ionic shifts within the brain and since both cell types can be affected by shifts in the extracellular potassium, it is important to characterize their individual response to an elevation of this ion. This review describes the results of side-by-side studies conducted on cortical neurons and astrocytes, which assessed the effect of elevated potassium on their resting membrane potential, intracellular volume, and their intracellular concentration of potassium, sodium, and chloride. The results obtained from these studies suggest that there exists a marked cellular heterogeneity between neurons and astrocytes in their response to an elevation in the extracellular potassium concentration.Key words: astrocytes, neurons, ion concentration, neuronal–glial interactions, mouse, cell culture.
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Morris, A. P., D. V. Gallacher, C. M. Fuller, and J. Scott. "Cholinergic Receptor-regulation of Potassium Channels and Potassium Transport in Human Submandibular Acinar Cells." Journal of Dental Research 66, no. 2 (February 1987): 541–46. http://dx.doi.org/10.1177/00220345870660022601.
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The cholinergic receptor-regulation of K+ transport was studied in human submandibular glands. Acetylcholine stimulation 10 μmol/L results in an increase in membrane permeability (86Rb+ efflux) for, and a net efflux of, K+ ions from the glandular tissue. In the post-stimulus period, there is a net re-uptake of K+ ions into the tissue. Patch-clamp electrophysiological techniques were employed to demonstrate the presence of a large conductance K+ selective ion channel in the basolateral membranes of isolated human submandibular acinar cells. The patch-clamp results indicate that this voltage- and calcium-activated K+ channel operates to regulate the K+ permeability in both the resting and acetylcholine-stimulated acinar cells. We discuss the role of the K+ channel, K+ efflux, and K+ re-uptake in relation to stimulus-secretion coupling.
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Wolowyk, M. W., and J. C. Ellory. "Changes in the cation composition and active K+ transport in the red cells of fetal sheep prepartum." Canadian Journal of Physiology and Pharmacology 63, no. 11 (November 1, 1985): 1454–59. http://dx.doi.org/10.1139/y85-238.
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The red blood cells of lambs, genotypically low potassium type, undergo a transition from high potassium to low potassium cell type from parturition onwards. This involves gradual changes in cell ion content, sodium pump activity, and ouabain binding. In the present study we investigated the properties of fetal red blood cells from 30 days prepartum using the chronically cannulated pregnant ewe preparation. We demonstrate that intracellular sodium increases and potassium decreases from −30 days onwards. Sodium pump activity monitored either by tracer potassium influx or ouabain binding is markedly higher in the early fetal samples examined and declines fourfold during the final month in utero. Unlike the maternal low potassium cells the early fetal red cells are refractory in terms of sodium pump stimulation by anti-L, the antibody in fact consistently inhibiting the pump. Finally, we have investigated the volume sensitivity and development of the ouabain-insensitive potassium fluxes in these cells and found that both fetal and maternal cells show a marked chloride-dependent, volume-sensitive passive potassium flux. We conclude that the decrease in active sodium transport between fetal red cells and adult low potassium cells is achieved partly by a reduction in the density of sodium pumps per cell, and then later by the introduction into the circulation of cells with Lp-antigen-modified sodium pumps.
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Deftu, Alexandru-Florian, Violeta Ristoiu, and Marc Rene Suter. "Intrathecal Administration of CXCL1 Enhances Potassium Currents in Microglial Cells." Pharmacology 101, no. 5-6 (2018): 262–68. http://dx.doi.org/10.1159/000486865.
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The functioning of microglial cells inside the central nervous system depends on their ion channels expression. Microglia are capable of synthesizing different cytokines and chemokines, including CXCL1, and responding to their action via specific receptors. In this study, we explore the effect of intrathecal injection of CXCL1 on potassium currents, expressed in CX3CR1-Green Fluorescent Protein labeled microglia in transgenic mice. The results showed that CXCL1 hyperpolarized the cells by enhancing inward rectifying potassium currents and increasing the membrane area, suggesting an activating effect on microglia.
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Chirra, Martina, Hannah S. Newton, Vaibhavkumar S. Gawali, Trisha M. Wise-Draper, Ameet A. Chimote, and Laura Conforti. "How the Potassium Channel Response of T Lymphocytes to the Tumor Microenvironment Shapes Antitumor Immunity." Cancers 14, no. 15 (July 22, 2022): 3564. http://dx.doi.org/10.3390/cancers14153564.
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Competent antitumor immune cells are fundamental for tumor surveillance and combating active cancers. Once established, tumors generate a tumor microenvironment (TME) consisting of complex cellular and metabolic elements that serve to suppress the function of antitumor immune cells. T lymphocytes are key cellular elements of the TME. In this review, we explore the role of ion channels, particularly K+ channels, in mediating the suppressive effects of the TME on T cells. First, we will review the complex network of ion channels that mediate Ca2+ influx and control effector functions in T cells. Then, we will discuss how multiple features of the TME influence the antitumor capabilities of T cells via ion channels. We will focus on hypoxia, adenosine, and ionic imbalances in the TME, as well as overexpression of programmed cell death ligand 1 by cancer cells that either suppress K+ channels in T cells and/or benefit from regulating these channels’ activity, ultimately shaping the immune response. Finally, we will review some of the cancer treatment implications related to ion channels. A better understanding of the effects of the TME on ion channels in T lymphocytes could promote the development of more effective immunotherapies, especially for resistant solid malignancies.
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Wu, Yuhan, Yang Xu, Yueliang Li, Pengbo Lyu, Jin Wen, Chenglin Zhang, Min Zhou, et al. "Unexpected intercalation-dominated potassium storage in WS2 as a potassium-ion battery anode." Nano Research 12, no. 12 (November 5, 2019): 2997–3002. http://dx.doi.org/10.1007/s12274-019-2543-0.
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Abstract Unexpected intercalation-dominated process is observed during K+ insertion in WS2 in a voltage range of 0.01–3.0 V. This is different from the previously reported two-dimensional (2D) transition metal dichalcogenides that undergo a conversion reaction in a low voltage range when used as anodes in potassium-ion batteries. Charge/discharge processes in the K and Na cells are studied in parallel to demonstrate the different ion storage mechanisms. The Na+ storage proceeds through intercalation and conversion reactions while the K+ storage is governed by an intercalation reaction. Owing to the reversible K+ intercalation in the van der Waals gaps, the WS2 anode exhibits a low decay rate of 0.07% per cycle, delivering a capacity of 103 mAh·g-1 after 100 cycles at 100 mA·g-1. It maintains 57% capacity at 800 mA·g-1 and shows stable cyclability up to 400 cycles at 500 mA·g-1. Kinetics study proves the facilitation of K+ transport is derived from the intercalation-dominated mechanism. Furthermore, the mechanism is verified by the density functional theory (DFT) calculations, showing that the progressive expansion of the interlayer space can account for the observed results.
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Zhao, Ke-Qing, Guoxiang Xiong, Morgan Wilber, Noam A. Cohen, and James L. Kreindler. "A role for two-pore K+ channels in modulating Na+ absorption and Cl− secretion in normal human bronchial epithelial cells." American Journal of Physiology-Lung Cellular and Molecular Physiology 302, no. 1 (January 1, 2012): L4—L12. http://dx.doi.org/10.1152/ajplung.00102.2011.
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Mucociliary clearance is the primary innate physical defense mechanism against inhaled pathogens and toxins. Vectorial ion transport, primarily sodium absorption and anion secretion, by airway epithelial cells supports mucociliary clearance. This is evidenced by diseases of abnormal ion transport such as cystic fibrosis and pseudohypoaldosteronism that are characterized by changes in mucociliary clearance. Sodium absorption and chloride secretion in human bronchial epithelial cells depend on potassium channel activity, which creates a favorable electrochemical gradient for both by hyperpolarizing the apical plasma membrane. Although the role of basolateral membrane potassium channels is firmly established and extensively studied, a role for apical membrane potassium channels has also been described. Here, we demonstrate that bupivacaine and quinidine, blockers of four-transmembrane domain, two-pore potassium (K2P) channels, inhibit both amiloride-sensitive sodium absorption and forskolin-stimulated anion secretion in polarized, normal human bronchial epithelial cells at lower concentrations when applied to the mucosal surface than when applied to the serosal surface. Transcripts from four genes, KCNK1 (TWIK-1), KCNK2 (TREK-1), KCNK5 (TASK-2), and KCNK6 (TWIK-2), encoding K2P channels were identified by RT-PCR. Protein expression at the apical membrane was confirmed by immunofluorescence. Our data provide further evidence that potassium channels, in particular K2P channels, are expressed and functional in the apical membrane of airway epithelial cells where they may be targets for therapeutic manipulation.
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Park, Kang-Sik, Jae-Won Yang, Edward Seikel, and James S. Trimmer. "Potassium Channel Phosphorylation in Excitable Cells: Providing Dynamic Functional Variability to a Diverse Family of Ion Channels." Physiology 23, no. 1 (February 2008): 49–57. http://dx.doi.org/10.1152/physiol.00031.2007.
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Phosphorylation of potassium channels affects their function and plays a major role in regulating cell physiology. Here, we review previous studies of potassium channel phosphorylation, focusing first on studies employing site-directed mutagenesis of recombinant channels expressed in heterologous cells. We then discuss recent mass spectrometric-based approaches to identify and quantify phosphorylation at specific sites on native and recombinant potassium channels, and newly developed mass spectrometric-based techniques that may prove beneficial to future studies of potassium channel phosphorylation, its regulation, and its mechanism of channel modulation.
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Chandra, S., E. P. Kable, G. H. Morrison, and W. W. Webb. "Calcium sequestration in the Golgi apparatus of cultured mammalian cells revealed by laser scanning confocal microscopy and ion microscopy." Journal of Cell Science 100, no. 4 (December 1, 1991): 747–52. http://dx.doi.org/10.1242/jcs.100.4.747.
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Co-localization of the elements calcium, potassium, sodium and magnesium with sequestering organelles has been achieved by application of two microscopy techniques on the same cell. Organelles were first localized by laser scanning confocal microscopy (LSCFM) using fluorescent organelle stains. The same cells were then analyzed for elemental distribution with ion microscopy. This approach has identified a perinuclear region of prominent total calcium concentration with the Golgi apparatus. Live cells were fluorescently stained with C6-NBD-ceramide for labeling the Golgi apparatus prior to cryogenic preparation and freeze-drying, and imaged with LSCFM for Golgi localization; identical cells were then analyzed with ion microscopy to image subcellular distributions of total calcium, potassium, sodium and magnesium. In three cell lines, LLC-PK1 porcine kidney epithelial cells, Swiss 3T3 mouse fibroblast cells and L5 rat myoblast cells, the Golgi regions contained significantly higher total calcium concentrations than any other region of the cell (as measured at the spatial resolution of ion microscopy of about 0.5 micron). Intracellular potassium, sodium and magnesium were homogeneously distributed throughout the cell and did not show this pattern. Measurements of depletion of calcium by exposure to calcium-free medium showed that the Golgi apparatus was substantially more resistant to calcium depletion than all other regions of these cells, but sequestered Ca2+ could be released from the Golgi by exposing the cells to calcium ionophore A23187. The Golgi apparatus appears to sequester about 5% of the total cell calcium in LLC-PK1 cells, about 2.5% in 3T3 cells and L5 cells.
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Rodriguez-Navarro, A., M. R. Blatt, and C. L. Slayman. "A potassium-proton symport in Neurospora crassa." Journal of General Physiology 87, no. 5 (May 1, 1986): 649–74. http://dx.doi.org/10.1085/jgp.87.5.649.
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Combined ion flux and electrophysiological measurements have been used to characterized active transport of potassium by cells of Neurospora crassa that have been moderately starved of K+ and then maintained in the presence of millimolar free calcium ions. These conditions elicit a high-affinity (K1/2 = 1-10 microM) potassium uptake system that is strongly depolarizing. Current-voltage measurements have demonstrated a K+-associated inward current exceeding (at saturation) half the total current normally driven outward through the plasma membrane proton pump. Potassium activity ratios and fluxes have been compared quantitatively with electrophysiological parameters, by using small (approximately 15 micron diam) spherical cells of Neurospora grown in ethylene glycol. All data are consistent with a transport mechanism that carries K ions inward by cotransport with H ions, which move down the electrochemical gradient created by the primary proton pump. The stoichiometry of entry is 1 K ion with 1 H ion; overall charge balance is maintained by pumped extrusion of two protons, to yield a net flux stoichiometry of 1 K+ exchanging for 1 H+. The mechanism is competent to sustain the largest stable K+ gradients that have been measured in Neurospora, with no direct contribution from phosphate hydrolysis or redox processes. Such a potassium-proton symport mechanism could account for many observations reported on K+ movement in other fungi, in algae, and in higher plants.
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Roden, D. M., and A. L. George. "Structure and function of cardiac sodium and potassium channels." American Journal of Physiology-Heart and Circulatory Physiology 273, no. 2 (August 1, 1997): H511—H525. http://dx.doi.org/10.1152/ajpheart.1997.273.2.h511.
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The application of patch-clamp and molecular approaches has resulted in an increasingly refined understanding of the molecular entities underlying cardiac sodium and potassium currents. The sodium current results from expression of a single large alpha-subunit, whereas multiple potassium currents and potassium channel alpha-subunits have been identified. Recapitulation of some ion currents in heterologous expression systems requires not only expression of alpha-subunits but also ancillary (beta) subunits. Domains common to functions such as activation, inactivation, and drug block are now being identified in alpha- and beta-gene products. Variability in the expression or function of individual ion-channel genes is an increasingly recognized source of variability in the ion currents recorded in heart cells under physiological conditions (e.g. during development) as well as in disease.
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Park, Jong-Hyeok, and Jin-Soo Park. "KOH-doped Porous Polybenzimidazole Membranes for Solid Alkaline Fuel Cells." Energies 13, no. 3 (January 21, 2020): 525. http://dx.doi.org/10.3390/en13030525.
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In this study the preparation and properties of potassium hydroxide-doped meta-polybenzimidazole membranes with 20–30 μm thickness are reported as anion conducting polymer electrolyte for application in fuel cells. Dibutyl phthalate as porogen forms an asymmetrically porous structure of membranes along thickness direction. One side of the membranes has a dense skin layer surface with 1.5–15 μm and the other side of the membranes has a porous one. It demonstrated that ion conductivity of the potassium hydroxide-doped porous membrane with the porogen content of 47 wt.% (0.090 S cm−1), is 1.4 times higher than the potassium hydroxide-doped dense membrane (0.065 S cm−1). This is because the porous membrane allows 1.4 times higher potassium hydroxide uptake than dense membranes. Tensile strength and elongation studies confirm that doping by simply immersing membranes in potassium hydroxide solutions was sufficient to fill in the inner pores. The membrane-electrode assembly using the asymmetrically porous membrane with 1.4 times higher ionic conductivity than the dense non-doped polybenzimidazole (mPBI) membrane showed 1.25 times higher peak power density.
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Lin, Yechao, Jiacen Liu, Liluo Shi, Nannan Guo, Zongfu Sun, Chao Geng, Jiangmin Jiang, Quanchao Zhuang, Yaxin Chen, and Zhicheng Ju. "Dual stabilization in potassium Prussian blue and cathode/electrolyte interface enables advanced potassium-ion full-cells." Journal of Colloid and Interface Science 623 (October 2022): 1–8. http://dx.doi.org/10.1016/j.jcis.2022.05.023.
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Nilius, B., T. B�hm, and W. Wohlrab. "Properties of a potassium-selective ion channel in human melanoma cells." Pfl�gers Archiv European Journal of Physiology 417, no. 3 (November 1990): 269–77. http://dx.doi.org/10.1007/bf00370992.
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Kim, Hyun Jong, Seorin Park, Hui Young Shin, Yu Ran Nam, Phan Thi Lam Hong, Young-Won Chin, Joo Hyun Nam, and Woo Kyung Kim. "Inhibitory effects of α-Mangostin on T cell cytokine secretion via ORAI1 calcium channel and K+ channels inhibition." PeerJ 9 (March 3, 2021): e10973. http://dx.doi.org/10.7717/peerj.10973.
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Background As one of the main components of mangosteen (Garcinia mangostana), a tropical fruit, α-mangostin has been reported to have numerous pharmacological benefits such as anti-cancer, anti-inflammatory, and anti-allergic effects through various mechanisms of action. The effects of α-mangostin on intracellular signaling proteins is well studied, but the effects of α-mangostin on ion channels and its physiological effects in immune cells are unknown. Generation of intracellular calcium signaling is a fundamental step for T cell receptor stimulation. This signaling is mediated not only by the ORAI1 calcium channel, but also by potassium ion channels, which provide the electrical driving forces for generating sufficient calcium ion influx. This study investigated whether α-mangosteen suppress T cell stimulation by inhibiting ORAI1 and two kinds of potassium channels (Kv1.3 and KCa3.1), which are normally expressed in human T cells. Methods This study analyzed the inhibitory effect of α-mangostin on immune cell activity via inhibition of calcium and potassium ion channels expressed in immune cells. Results α-mangostin inhibited ORAI1 in a concentration-dependent manner, and the IC50 value was 1.27 ± 1.144 µM. Kv1.3 was suppressed by 41.38 ± 6.191% at 3 µM, and KCa3.1 was suppressed by 51.16 ± 5.385% at 3 µM. To measure the inhibition of cytokine secretion by immune cells, Jurkat T cells were stimulated to induce IL-2 secretion, and α-mangostin was found to inhibit it. This study demonstrated the anti-inflammatory effect of α-mangostin, the main component of mangosteen, through the regulation of calcium signals.
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Kashtoh, Hamdy, and Kwang-Hyun Baek. "Structural and Functional Insights into the Role of Guard Cell Ion Channels in Abiotic Stress-Induced Stomatal Closure." Plants 10, no. 12 (December 15, 2021): 2774. http://dx.doi.org/10.3390/plants10122774.
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A stomatal pore is formed by a pair of specialized guard cells and serves as a major gateway for water transpiration and atmospheric CO2 influx for photosynthesis in plants. These pores must be tightly controlled, as inadequate CO2 intake and excessive water loss are devastating for plants. When the plants are exposed to extreme weather conditions such as high CO2 levels, O3, low air humidity, and drought, the turgor pressure of the guard cells exhibits an appropriate response against these stresses, which leads to stomatal closure. This phenomenon involves a complex network of ion channels and their regulation. It is well-established that the turgor pressure of guard cells is regulated by ions transportation across the membrane, such as anions and potassium ions. In this review, the guard cell ion channels are discussed, highlighting the structure and functions of key ion channels; the SLAC1 anion channel and KAT1 potassium channel, and their regulatory components, emphasizing their significance in guard cell response to various stimuli.
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Nakamura, Kazuyoshi, Hikaru Hayashi, and Manabu Kubokawa. "Proinflammatory Cytokines and Potassium Channels in the Kidney." Mediators of Inflammation 2015 (2015): 1–8. http://dx.doi.org/10.1155/2015/362768.
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Proinflammatory cytokines affect several cell functions via receptor-mediated processes. In the kidney, functions of transporters and ion channels along the nephron are also affected by some cytokines. Among these, alteration of activity of potassium ion (K+) channels induces changes in transepithelial transport of solutes and water in the kidney, since K+channels in tubule cells are indispensable for formation of membrane potential which serves as a driving force for the transepithelial transport. Altered K+channel activity may be involved in renal cell dysfunction during inflammation. Although little information was available regarding the effects of proinflammatory cytokines on renal K+channels, reports have emerged during the last decade. In human proximal tubule cells, interferon-γshowed a time-dependent biphasic effect on a 40 pS K+channel, that is, delayed suppression and acute stimulation, and interleukin-1βacutely suppressed the channel activity. Transforming growth factor-β1 activated KCa3.1 K+channel in immortalized human proximal tubule cells, which would be involved in the pathogenesis of renal fibrosis. This review discusses the effects of proinflammatory cytokines on renal K+channels and the causal relationship between the cytokine-induced changes in K+channel activity and renal dysfunction.
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Gaber, R. F., C. A. Styles, and G. R. Fink. "TRK1 encodes a plasma membrane protein required for high-affinity potassium transport in Saccharomyces cerevisiae." Molecular and Cellular Biology 8, no. 7 (July 1988): 2848–59. http://dx.doi.org/10.1128/mcb.8.7.2848-2859.1988.
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We identified a 180-kilodalton plasma membrane protein in Saccharomyces cerevisiae required for high-affinity transport (uptake) of potassium. The gene that encodes this putative potassium transporter (TRK1) was cloned by its ability to relieve the potassium transport defect in trk1 cells. TRK1 encodes a protein 1,235 amino acids long that contains 12 potential membrane-spanning domains. Our results demonstrate the physical and functional independence of the yeast potassium and proton transport systems. TRK1 is nonessential in S. cerevisiae and maps to a locus unlinked to PMA1, the gene that encodes the plasma membrane ATPase. Haploid cells that contain a null allele of TRK1 (trk1 delta) rely on a low-affinity transporter for potassium uptake and, under certain conditions, exhibit energy-dependent loss of potassium, directly exposing the activity of a transporter responsible for the efflux of this ion.
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Gaber, R. F., C. A. Styles, and G. R. Fink. "TRK1 encodes a plasma membrane protein required for high-affinity potassium transport in Saccharomyces cerevisiae." Molecular and Cellular Biology 8, no. 7 (July 1988): 2848–59. http://dx.doi.org/10.1128/mcb.8.7.2848.
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We identified a 180-kilodalton plasma membrane protein in Saccharomyces cerevisiae required for high-affinity transport (uptake) of potassium. The gene that encodes this putative potassium transporter (TRK1) was cloned by its ability to relieve the potassium transport defect in trk1 cells. TRK1 encodes a protein 1,235 amino acids long that contains 12 potential membrane-spanning domains. Our results demonstrate the physical and functional independence of the yeast potassium and proton transport systems. TRK1 is nonessential in S. cerevisiae and maps to a locus unlinked to PMA1, the gene that encodes the plasma membrane ATPase. Haploid cells that contain a null allele of TRK1 (trk1 delta) rely on a low-affinity transporter for potassium uptake and, under certain conditions, exhibit energy-dependent loss of potassium, directly exposing the activity of a transporter responsible for the efflux of this ion.
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Dong, J., and N. A. Delamere. "Protein kinase C inhibits Na(+)-K(+)-2Cl- cotransporter activity in cultured rabbit nonpigmented ciliary epithelium." American Journal of Physiology-Cell Physiology 267, no. 6 (December 1, 1994): C1553—C1560. http://dx.doi.org/10.1152/ajpcell.1994.267.6.c1553.
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We examined the regulation of Na(+)-K(+)-2Cl- transporter activity by protein kinase C (PKC) in a cell line derived from rabbit nonpigmented ciliary epithelium. Na(+)-K(+)-2Cl- cotransporter activity was measured as the rate of bumetanide-sensitive potassium (86Rb) transport. Phorbol 12,13-dibutyrate (PBDu) was used to activate PKC. PBDu inhibited bumetanide-sensitive potassium (86Rb) uptake, with a half-maximal inhibitory concentration of approximately 0.1 microM. The inhibitory effect of PBDu on potassium uptake by the N(+)-K(+)-2Cl- cotransporter was abolished by PCK downregulation and diminished by 1-(5-isoquinolinylsulfonyl)-2-methylpiperazine, a PKC inhibitor. PBDu inhibited Na(+)-K(+)-2Cl- cotransporter-mediated inward potassium (86Rb) transport by approximately 26% in control cells and by 40% in cells pretreated with ouabain. PKC activation also reduced the rate of bumetanide-sensitive potassium (86Rb) efflux in ouabain-treated cells but not in control (no oubain) cells. PBDu caused little change of intracellular sodium, potassium, or chloride, suggesting that an alteration of cytoplasmic ion composition is not responsible for the observed PBDu-induced changes in the rate of either inward or outward potassium movement mediated by the Na(+)-K(+)-2Cl- cotransporter.
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Pérez-García, M. Teresa, Pilar Cidad, and José R. López-López. "The secret life of ion channels: Kv1.3 potassium channels and proliferation." American Journal of Physiology-Cell Physiology 314, no. 1 (January 1, 2018): C27—C42. http://dx.doi.org/10.1152/ajpcell.00136.2017.
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Kv1.3 channels are involved in the switch to proliferation of normally quiescent cells, being implicated in the control of cell cycle in many different cell types and in many different ways. They modulate membrane potential controlling K+ fluxes, sense changes in potential, and interact with many signaling molecules through their intracellular domains. From a mechanistic point of view, we can describe the role of Kv1.3 channels in proliferation with at least three different models. In the “membrane potential model,” membrane hyperpolarization resulting from Kv1.3 activation provides the driving force for Ca2+ influx required to activate Ca2+-dependent transcription. This model explains most of the data obtained from several cells from the immune system. In the “voltage sensor model,” Kv1.3 channels serve mainly as sensors that transduce electrical signals into biochemical cascades, independently of their effect on membrane potential. Kv1.3-dependent proliferation of vascular smooth muscle cells (VSMCs) could fit this model. Finally, in the “channelosome balance model,” the master switch determining proliferation may be related to the control of the Kv1.3 to Kv1.5 ratio, as described in glial cells and also in VSMCs. Since the three mechanisms cannot function independently, these models are obviously not exclusive. Nevertheless, they could be exploited differentially in different cells and tissues. This large functional flexibility of Kv1.3 channels surely gives a new perspective on their functions beyond their elementary role as ion channels, although a conclusive picture of the mechanisms involved in Kv1.3 signaling to proliferation is yet to be reached.
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Pozdnyakov, Ilya, Olga Matantseva, and Sergei Skarlato. "Consensus channelome of dinoflagellates revealed by transcriptomic analysis sheds light on their physiology." Algae 36, no. 4 (December 15, 2021): 315–26. http://dx.doi.org/10.4490/algae.2021.36.12.2.
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Ion channels are membrane protein complexes mediating passive ion flux across the cell membranes. Every organism has a certain set of ion channels that define its physiology. Dinoflagellates are ecologically important microorganisms characterized by effective physiological adaptability, which backs up their massive proliferations that often result in harmful blooms (red tides). In this study, we used a bioinformatics approach to identify homologs of known ion channels that belong to 36 ion channel families. We demonstrated that the versatility of the dinoflagellate physiology is underpinned by a high diversity of ion channels including homologs of animal and plant proteins, as well as channels unique to protists. The analysis of 27 transcriptomes allowed reconstructing a consensus ion channel repertoire (channelome) of dinoflagellates including the members of 31 ion channel families: inwardly-rectifying potassium channels, two-pore domain potassium channels, voltage-gated potassium channels (Kv), tandem Kv, cyclic nucleotide-binding domain-containing channels (CNBD), tandem CNBD, eukaryotic ionotropic glutamate receptors, large-conductance calcium-activated potassium channels, intermediate/small-conductance calcium-activated potassium channels, eukaryotic single-domain voltage-gated cation channels, transient receptor potential channels, two-pore domain calcium channels, four-domain voltage-gated cation channels, cation and anion Cys-loop receptors, small-conductivity mechanosensitive channels, large-conductivity mechanosensitive channels, voltage-gated proton channels, inositole-1,4,5- trisphosphate receptors, slow anion channels, aluminum-activated malate transporters and quick anion channels, mitochondrial calcium uniporters, voltage-dependent anion channels, vesicular chloride channels, ionotropic purinergic receptors, animal volage-insensitive cation channels, channelrhodopsins, bestrophins, voltage-gated chloride channels H+/Cl- exchangers, plant calcium-permeable mechanosensitive channels, and trimeric intracellular cation channels. Overall, dinoflagellates represent cells able to respond to physical and chemical stimuli utilizing a wide range of Gprotein coupled receptors- and Ca2+-dependent signaling pathways. The applied approach not only shed light on the ion channel set in dinoflagellates, but also provided the information on possible molecular mechanisms underlying vital cellular processes dependent on the ion transport.
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Dey, Sonjoy, and Gurpreet Singh. "WS2 Nanosheet Loaded Silicon-Oxycarbide Electrode for Sodium and Potassium Batteries." Nanomaterials 12, no. 23 (November 25, 2022): 4185. http://dx.doi.org/10.3390/nano12234185.
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Transition metal dichalcogenides (TMDs) such as the WS2 have been widely studied as potential electrode materials for lithium-ion batteries (LIB) owing to TMDs’ layered morphology and reversible conversion reaction with the alkali metals between 0 to 2 V (v/s Li/Li+) potentials. However, works involving TMD materials as electrodes for sodium- (NIBs) and potassium-ion batteries (KIBs) are relatively few, mainly due to poor electrode performance arising from significant volume changes and pulverization by the larger size alkali-metal ions. Here, we show that Na+ and K+ cyclability in WS2 TMD is improved by introducing WS2 nanosheets in a chemically and mechanically robust matrix comprising precursor-derived ceramic (PDC) silicon oxycarbide (SiOC) material. The WS2/SiOC composite in fibermat morphology was achieved via electrospinning followed by thermolysis of a polymer solution consisting of a polysiloxane (precursor to SiOC) dispersed with exfoliated WS2 nanosheets. The composite electrode was successfully tested in Na-ion and K-ion half-cells as a working electrode, which rendered the first cycle charge capacity of 474.88 mAh g−1 and 218.91 mAh g−1, respectively. The synergistic effect of the composite electrode leads to higher capacity and improved coulombic efficiency compared to the neat WS2 and neat SiOC materials in these cells.
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Hotchkiss, Karin, Margaret Harvey, Mary Pacheco, and Bernd Sokolowski. "Ion channel proteins in mouse and human vestibular tissue." Otolaryngology–Head and Neck Surgery 132, no. 6 (June 2005): 916–23. http://dx.doi.org/10.1016/j.otohns.2005.01.022.
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BACKGROUND AND OBJECTIVE: Electrical activity in hair cells and neurons of the inner ear is necessary for the transduction and modulation of stimuli that impinge on the cochlea and vestibular endorgans of the inner ear. The underlying basis of this activity is pore-forming proteins in the membrane of excitable cells that allow the influx and efflux of various ions, including Na+, Ca2+, and K+, among others. These channels are critical to both electrical activity as well as the development of excitable cells because they may initiate long-term signals that are important in the maintenance and survival of these cells. We investigated the expression of several Shaker potassium ion channel proteins and an accessory β subunit in the vestibular endorgans of mouse and human. METHODS: Vestibular tissue consisting of cristae ampullares was harvested from adult and neonatal mice as well as from human subjects undergoing vestibular surgery. Western blot analysis and immunoprecipitation were used to identify the presence or absence, in mouse, of α subunits Kv1.2, Kv1.4, and Kv1.5 and of β subunit Kvβ1.1 in mouse. Coimmunoprecipitation was used to identify interactions between α and β subunits. Immunohistochemistry was used to localize Kv1.2 in mouse and human tissues. RESULTS: The presence of Kvα1.2 and Kvβ1.1 was confirmed in adult mouse crista ampullaris by Western blotting. Coimmunoprecipitation experiments showed that Kv1.2 and Kvβ1.1 interact in these tissues. Immunostaining localized Kv1.2 to regions within and extraneous to the sensory epithelium of mouse and human cristae ampullares. In comparison, Kv1.4 and Kv1.5 were not found in the crista ampullaris. CONCLUSIONS: We describe the presence, location, and interaction of various potassium ion channel α subunits and a β subunit. These data are initial descriptions of potassium ion channels in the mammalian vestibular system and begin to provide an understanding of the protein subunits that form ion channels of the mammalian inner ear. In addition, our data show that there are interactions that occur that may regulate the biophysical properties of these channels, thereby contributing to the diversity of channel function. This knowledge is critical to understanding the genes that encode these channels and finding cures for pathologies of hearing and balance. SIGNIFICANCE: We detail initial characteristics of potassium ion channel proteins including α subunits Kv1.2, Kv1.4, and Kv1.5 and β subunit Kvβ1.1 in mammalian vestibular tissue. This knowledge is critical to understanding the processing of vestibular stimuli and the regulation of endolymphatic function. Mutations of ion channels can cause neurological pathologies including auditory and vestibular disorders in humans.
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Schär-Zammaretti, Prisca, Urs Ziegler, Ian Forster, Peter Groscurth, and Ursula E. Spichiger-Keller. "Potassium-Selective Atomic Force Microscopy on Ion-Releasing Substrates and Living Cells." Analytical Chemistry 74, no. 16 (August 2002): 4269–74. http://dx.doi.org/10.1021/ac025605n.
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Fukuda, Koichiro, Yuji Michisuji, Kiyoshi Kamiya, Takeshi Himeno, Takao Kiyota, and Torao Ishida. "Potassium ion enhances tissue-type plasminogen activator expression in cultured HEL cells." Journal of Fermentation and Bioengineering 76, no. 2 (January 1993): 111–16. http://dx.doi.org/10.1016/0922-338x(93)90066-h.
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Pappone, P. A., and M. T. Lucero. "Potassium channel block does not affect metabolic responses of brown fat cells." American Journal of Physiology-Cell Physiology 262, no. 3 (March 1, 1992): C678—C681. http://dx.doi.org/10.1152/ajpcell.1992.262.3.c678.
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Hormonally stimulated brown fat cells are capable of extremely high metabolic rates, making them an excellent system in which to examine the role of plasma membrane ion channels in cell metabolism. We have previously shown that brown fat cell membranes have both voltage-gated and calcium-activated potassium channels (Voltage-gated potassium channels in brown fat cells. J. Gen. Physiol. 93: 451-472, 1989; Membrane responses to norepinephrine in cultured brown fat cells. J. Gen. Physiol. 95: 523-544, 1990). Currents through both the voltage-activated potassium channels, IK,V, and the calcium-activated potassium channels, IK,Ca, can be blocked by the membrane-impermeant K channel blocker tetraethylammonium (TEA). We used microcalorimetric measurements from isolated neonatal rat brown fat cells to assess the role these potassium conductances play in the metabolic response of brown fat cells to adrenergic stimulation. Concentrations of TEA as high as 50 mM, sufficient to block approximately 95% of IK,V and 100% of IK,Ca, had no effect on norepinephrine-stimulated heat production. These results show that neither voltage-gated nor calcium-activated K channels are necessary for a maximal thermogenic response in brown fat cells and suggest that K channels are not involved in maintaining cellular homeostasis during periods of high metabolic activity.
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Khudyshkina, Anna D., Iurii Panasenko, Philip Henkel, Christian Njel, and Fabian Jeschull. "(Invited) Degradation Processes at the Potassium Hexacyanoferrate Electrode in Potassium-Ion Batteries." ECS Meeting Abstracts MA2022-02, no. 59 (October 9, 2022): 2205. http://dx.doi.org/10.1149/ma2022-02592205mtgabs.
Full textAbstract:
Prussian blue analogues (PBAs)[1] with the general composition A2M[Fe(CN)6] (A: alkali metal; M: Fe, Mn, etc) are an attractive positive electrode for potassium-ion batteries, owing to their chemical composition based on widely abundant materials, ease of synthesis, high electrochemical reversibility and higher average potential compared to its sodium congener [1]. The combination of a PBA electrode with a graphite negative electrode in a full cell configuration showed great promise as post-Li battery system. However, the upper cut-off potentials of K2Fe[Fe(CN)6] and K2Mn[Fe(CN)6] pose serious stability issues with respect to irreversible electrolyte degradation reactions. In addition, the electrolyte components have to be compatible with the potassium intercalation reaction at the graphite electrode[2], thus limiting the number of suitable electrolyte constituents. In this presentation, we discuss aspects of the material synthesis and electrolyte degradation processes at high potentials in liquid carbonate-based electrolytes. As we will be shown the choice of the precursors is paramount to arrive at suitable particle sizes and has a great impact on the electrochemical behavior of the material. Likewise, the density of Fe-vacancies strongly depends on the chosen synthesis and may lead to significant losses in the achievable discharge capacity. The electrode-electrolyte interface in half and full cell configurations was studied by in-house and synchrotron-based photoelectron spectroscopy (PES) for a detailed characterization of the surface layer and the oxidation states of iron in K2Fe[Fe(CN)6] electrodes. This combined analysis of electrochemical and surface-sensitive analytical studies provides a general picture of the electrode degradation at high potentials and fosters the development of better electrolyte mixtures. Our results further show, how a deliberate choice of electrolyte components can help to reduce irreversible reactions and improve cycling stability and cycle life of potassium-ion batteries. For this we have recently expanded our activities also to solid polymer electrolytes, showing superior capacity retention to liquid electrolyte systems[3]. Figure 1. left: K2Fe[Fe(CN)6] obtained using different Fe-precursors; right: capacity retention of PBA-K cells cycled in either a liquid (black) or solid polymer (red/purple) electrolyte. Reference s : [1] Kim et al., Trends Chem. 1 (2019) 682–692. [2] Allgayer et al., ACS Appl. Energy Mater. 5 (2022) 1136–1148. [3] Khudyshkina et al., ACS Appl. Polym. Mater. 4 (2022) 2734–2746. Figure 1