Block of cloned BK Ca channels ( rSlo ) expressed in HEK 293 cells by N- methyl d - glucamine

Lippiat, Jonathan D.; Standen, N B; Davies, Noel W.

doi:10.1007/s004240050708

Cited by 15 publications

(106 citation statements)

References 6 publications

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“…Osmolarity was adjusted by adding sucrose to the bath solution and ranged from 280 to 306 mosmol/l. The addition of the N-methyl D-glucamine to the solutions was avoided due to the interference of this substance with BK channel currents [32]. CaCl 2 was added to the pipette and bath solutions to give free Ca 2+ ion concentration of 10 −6 M in whole cell experiments.…”

Section: Methodsmentioning

confidence: 99%

Emerging Role of Calcium-Activated Potassium Channel in the Regulation of Cell Viability Following Potassium Ions Challenge in HEK293 Cells and Pharmacological Modulation

et al. 2013

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Emerging evidences suggest that Ca2+activated-K+-(BK) channel is involved in the regulation of cell viability. The changes of the cell viability observed under hyperkalemia (15 mEq/L) or hypokalemia (0.55 mEq/L) conditions were investigated in HEK293 cells expressing the hslo subunit (hslo-HEK293) in the presence or absence of BK channel modulators. The BK channel openers(10-11-10-3M) were: acetazolamide(ACTZ), Dichlorphenamide(DCP), methazolamide(MTZ), bendroflumethiazide(BFT), ethoxzolamide(ETX), hydrochlorthiazide(HCT), quercetin(QUERC), resveratrol(RESV) and NS1619; and the BK channel blockers(2x10-7M-5x10-3M) were: tetraethylammonium(TEA), iberiotoxin(IbTx) and charybdotoxin(ChTX). Experiments on cell viability and channel currents were performed using cell counting kit-8 and patch-clamp techniques, respectively. Hslo whole-cell current was potentiated by BK channel openers with different potency and efficacy in hslo-HEK293. The efficacy ranking of the openers at -60 mV(Vm) was BFT> ACTZ >DCP ≥RESV≥ ETX> NS1619> MTZ≥ QUERC; HCT was not effective. Cell viability after 24 h of incubation under hyperkalemia was enhanced by 82+6% and 33+7% in hslo-HEK293 cells and HEK293 cells, respectively. IbTx, ChTX and TEA enhanced cell viability in hslo-HEK293. BK openers prevented the enhancement of the cell viability induced by hyperkalemia or IbTx in hslo-HEK293 showing an efficacy which was comparable with that observed as BK openers. BK channel modulators failed to affect cell currents and viability under hyperkalemia conditions in the absence of hslo subunit. In contrast, under hypokalemia cell viability was reduced by -22+4% and -23+6% in hslo-HEK293 and HEK293 cells, respectively; the BK channel modulators failed to affect this parameter in these cells. In conclusion, BK channel regulates cell viability under hyperkalemia but not hypokalemia conditions. BFT and ACTZ were the most potent drugs either in activating the BK current and in preventing the cell proliferation induced by hyperkalemia. These findings may have relevance in disorders associated with abnormal K+ ion homeostasis including periodic paralysis and myotonia.

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Section: Methodsmentioning

confidence: 99%

Emerging Role of Calcium-Activated Potassium Channel in the Regulation of Cell Viability Following Potassium Ions Challenge in HEK293 Cells and Pharmacological Modulation

et al. 2013

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“…Before the molecular characterization of glioma Cl − channels, which we now presume to be primarily ClC-3 channels, we found that Cltx, a scorpion-derived 36-residue peptide that was isolated as a putative Cl − -channel blocker (DeBin et al, 1993) inhibits whole-cell Cl − currents in glioma cells in vitro (Lippiat et al, 1998) and in situ (Ullrich et al, 1998). Moreover, Cltx inhibits glioma-cell invasion in several in situ invasion models, as does the Cl − -channel inhibitor NPPB (Soroceanu et al, 1999).…”

Section: A Putative CL − Channel Inhibitor (Cltx) Is Currently In Climentioning

confidence: 99%

A role for ion channels in glioma cell invasion

McFerrin¹,

2005

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Many cells, including neuronal and glial progenitor cells, stem cells and microglial cells, have the capacity to move through the extracellular spaces of the developing and mature brain. This is particularly pronounced in astrocyte-derived tumors, gliomas, which diffusely infiltrate the normal brain. Although a significant body of literature exists regarding signals that are involved in the guidance of cells and their processes, little attention has been paid to cell-shape and cell-volume changes of migratory cells. However, extracellular spaces in the brain are very narrow and represent a major obstacle that requires cells to dynamically regulate their volume. Recent studies in glioma cells show that this involves the secretion of Cl − and K + with water. Pharmacological inhibition of Cl − channels impairs their ability to migrate and limits tumor progression in experimental tumor models. One Cl − -channel inhibitor, chlorotoxin, is currently in Phase II clinical trials to treat malignant glioma. This article reviews our current knowledge of cell-volume changes and the role of ion channels during the migration of glioma cells. It also discusses evidence that supports the importance of channel-mediated cell-volume changes in the migration of immature neurons and progenitor cells during development. New unpublished data is presented, which demonstrates that Cl − and K + channels involved in cell shrinkage localize to lipid-raft domains on the invadipodia of glioma cells and that their presence might be regulated by trafficking of these proteins in and out of lipid rafts.

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“…NMDG itself has a variety of cellular effects (Hoener 2000;Mroz and Lechene 1993). As expected from the above data on other amines, these include blocking I A (Melishchuk and Armstrong 2001) and calcium-activated potassium (Lippiat et al 1998) channels when applied internally. Internal NMDG also decreases calcium current and alters calcium current kinetics and voltage dependence (Malécot et al 1988), which would also alter calcium-activated potassium currents.…”

Section: Introductionmentioning

confidence: 71%

Choline and NMDG directly reduce outward currents: reduced outward current when these substances replace Na⁺is alone not evidence of Na⁺-activated K⁺currents

Thuma

Hooper

2018

Journal of Neurophysiology

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Choline chloride is often, and N-methyl-d-glucamine (NMDG) sometimes, used to replace sodium chloride in studies of sodium-activated potassium channels. Given the high concentrations used in sodium replacement protocols, it is essential to test that it is not the replacement substances themselves, as opposed to the lack of sodium, that cause any observed effects. We therefore compared, in lobster stomatogastric neurons and leech Retzius cells, the effects of applying salines in which choline chloride replaced sodium chloride, and in which choline hydroxide or sucrose was added to normal saline. We also tested, in stomatogastric neurons, the effect of adding NMDG to normal saline. These protocols allowed us to measure the direct effects (i.e., effects not due to changes in sodium concentration or saline osmolarity or ionic strength) of choline on stomatogastric and leech currents, and of NMDG on stomatogastric currents. Choline directly reduced transient and sustained depolarization-activated outward currents in both species, and NMDG directly reduced transient depolarization-activated outward currents in stomatogastric neurons. Experiments with lower choline concentrations showed that adding as little as 150 mM (stomatogastric) or 5 mM (leech) choline reduced at least some depolarization-activated outward currents. Reductions in outward current with choline chloride or NMDG replacement alone are thus not evidence of sodium-activated potassium currents. NEW & NOTEWORTHY We show that choline or N-methyl-d-glucamine (NMDG) directly (i.e., not due to changes in extracellular sodium) decrease outward currents. Prior work studying sodium-activated potassium channels in which sodium was replaced with choline or NMDG without an addition control may therefore be artifactual.

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Block of cloned BK Ca channels ( rSlo ) expressed in HEK 293 cells by N- methyl d - glucamine

Cited by 15 publications

References 6 publications

Emerging Role of Calcium-Activated Potassium Channel in the Regulation of Cell Viability Following Potassium Ions Challenge in HEK293 Cells and Pharmacological Modulation

Emerging Role of Calcium-Activated Potassium Channel in the Regulation of Cell Viability Following Potassium Ions Challenge in HEK293 Cells and Pharmacological Modulation

A role for ion channels in glioma cell invasion

Choline and NMDG directly reduce outward currents: reduced outward current when these substances replace Na⁺is alone not evidence of Na⁺-activated K⁺currents

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Block of cloned BK Ca channels ( rSlo ) expressed in HEK 293 cells by N- methyl d - glucamine

Cited by 15 publications

References 6 publications

Emerging Role of Calcium-Activated Potassium Channel in the Regulation of Cell Viability Following Potassium Ions Challenge in HEK293 Cells and Pharmacological Modulation

Emerging Role of Calcium-Activated Potassium Channel in the Regulation of Cell Viability Following Potassium Ions Challenge in HEK293 Cells and Pharmacological Modulation

A role for ion channels in glioma cell invasion

Choline and NMDG directly reduce outward currents: reduced outward current when these substances replace Na+is alone not evidence of Na+-activated K+currents

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Choline and NMDG directly reduce outward currents: reduced outward current when these substances replace Na⁺is alone not evidence of Na⁺-activated K⁺currents