• BMB Reports
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• v.39 no.1
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• pp.91-96
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• 2006

Previously, we have shown that nitric oxide (NO) directly activates the Maxi-K channels. In the present study, we have investigated whether NO has prolonged effects on the Maxi-K channels reconstituted in lipid bilayer. Application of S-nitroso-N-acetyl-D, L-penicillamine (SNAP), a NO donor, induced an immediate increase of open probability (Po) of Maxi-K channel in a dose-dependent manner. When SNAP was removed from the cytosolic solution, the Po did not simply returned to, but irreversibly decreased to a level lower than that of the control Po. At 0.2 mM, (Z)-[N-(3-Ammoniopropyl)-N-(n-propyl)amino] diazen-1-ium-1,2-diolate (PAPA-NO), another NO donor, produced a similar increase of Po and decrease of Po upon washout. The increasing effects of SNAP on Po were not blocked by either 50 U/ml superoxide dismutase (SOD) or 2 mM N-ethylmaleimide (NEM) pre-treatments. However, NEM appears to be ineffective when applied after SNAP. These results suggest that NO can modulate Maxi-K channel via direct interaction and chemical modification, such as S-nitrosylation in the brain.

• The Korean Journal of Physiology and Pharmacology
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• v.2 no.4
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• pp.529-539
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• 1998

The effects of membrane surface charge originated from lipid head groups on ion channels were tested by analyzing the activity of single large conductance $Ca^{2+}-activated\;K^+$ (maxi K) channel from rat skeletal muscle. The conductances and open-state probability ($P_o$) of single maxi K channels were compared in three types of planar lipid bilayers formed from a neutral phosphatidylethanolamine (PE) or two negatively-charged phospholipids, phosphatidylserine (PS) and phosphatidylinositol (PI). Under symmetrical KCl concentrations $(3{\sim}1,000\;mM)$, single channel conductances of maxi K channels in charged membranes were $1.1{\sim}1.7$ times larger than those in PE membranes, and the differences were more pronounced at the lower ionic strength. The average slope conductances at 100 mM KCl were $251{\pm}9.9$, $360{\pm}8.7$ and $356{\pm}12.4$ $(mean{\pm}SEM)$ pS in PE, PS and PI membranes respectively. The potentials at which $P_o$ was 1/2, appeared to have shifted left by 40 mV along voltage axis in the membranes formed with PS or PI. Such shift was consistently seen at pCa 5, 4.5, 4 and 3.5. Estimation of the effect of surface charge from these data indicated that maxi K channels sensed the surface potentials at a distance of $8{\sim}9\;{\AA}$ from the membrane surface. In addition, similar insulation distance ($7{\sim}9\;{\AA}$) of channel mouth from the bilayer surface charge was predicted by a 3-barrier-2-site model of energy profile for the permeation of $K^+$ ions. In conclusion, despite the differences in structure and fluidity of phospholipids in bilayers, the activities of maxi K channels in two charged membranes composed of PS or PI were strikingly similar and larger than those in bilayers of PE. These results suggest that the enhancement of conductance and $P_o$ of maxi channels is mostly due to negative charges in the phospholipid head groups.

• Proceedings of the Korean Biophysical Society Conference
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• 1996.07a
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• pp.36-36
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• 1996

The activities of Maxi-K channels were recorded using inside-out patches. The application of 30 nM of non-specific G protein activator, GTP $\gamma$S, to the intracellular side of the channels increases the channel activities about 3-fold, indicating that there exist some G proteins within the patch membranes to regulate the channel activities. (omitted)

• Proceedings of the Korean Biophysical Society Conference
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• 1999.06a
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• pp.63-63
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• 1999

Large conductance $Ca^{2＋}$-activated $K^{＋}$ channels (Maxi-K channel) have been implicated in many important physiological processes such as co-ordination of membrane excitability in neurons. Modulation of these channels are archived by the activity of various protein kinases. The most widely studied example of Maxi-K channel regulation by protein phosphorylation has been obtained using plasma membranes from the rat brain incorporated into lipid bilayers.(omitted)

• Proceedings of the Korean Biophysical Society Conference
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• 1998.06a
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• pp.33-33
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• 1998

Oxidation and reduction of amino acid residues in proteins affect their functional properties. Especially, redox modulation of ion channel activities has been reported in number of ion channel proteins. In this study, we investigated the effects of tertiary-butyl hydrogen peroxide (tBHP) on the large-conductance Ca$\^$2＋/ -activated K$\^$+/(Maxi-K) channel of rat brain using lipid bilayer reconstitution technique.(omitted)

• Proceedings of the Korean Biophysical Society Conference
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• 1997.07a
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• pp.24-24
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• 1997

We have investigated whether NO affects the activities of the rat brain Maxi- K channels reconstituted into the lipid bilayer. In order to introduce NO, we utilized an antibiotic, streptozotocin (STZ), which releases NO upon illumination. While adding STZ itself did not affect the channel activity, turning on the light in the presence of STZ induced an increase in the open probability (Po) of the channel.(omitted)

• Proceedings of the Korean Biophysical Society Conference
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• 1999.06a
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• pp.51-51
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• 1999

Polyamines are polyvalent cations which are ubiquitously present in pro- and eukaryotic cells. In the present study we investigated the action mechanism of spermine$\^$＋4/ (C$\sub$10/), a natural polyamine, on the large-conductance Ca$\^$2＋/-activated K (maxi-K) channel using excised patches from the human gastric smooth muscle.(omitted)

• Journal of Ginseng Research
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• v.23 no.4
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• pp.230-234
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• 1999

Potassium channels play an important role in regulating vascular smooth muscle tone. Four types of $K^+$ channels areknown to be expressed in vascular smooth muscle cells, and maxi $Ca^{2+}-activated\;K^+$ channel $(BK_{Ca})$ is a dominant type of $K^+$ channels in these cells. Because total ginseng saponins and ginsenoside $Rg_3$ cause vasodilation with unclear mechanisms, we hypothesized that total ginseng saponins and ginsenoside $Rg_3$ induce vasodilation via activation of maxi $Ca^{2+}-activated\;K+$ channels. Whole-cell BKe. currents were voltage-dependent with half maximum activation at -14 mV, and the currents were sensitive to nanomolar ChTX and millimolar TEA. External application of total ginseng saponins increased the anlplitude of the whole-cell BKe. current in a concentration-dependent manner. Single-channel analysis indicates that total ginseng saponins caused the channel opening for a longer period of time. Ginsenoside $Rg_3$ increased the amplitude of whole-cell $K_{Ca}$ currents without affecting voltage dependence of the currents and increased single-channel open time. Hence, the results suggest that ginseng saponin-induced vasodilation may be due to activation of $K_{Ca}$.

• The Korean Journal of Physiology
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• v.28 no.1
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• pp.37-50
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• 1994

Synthetic potassium channel openers (KCOs) are agents capable of opening K-channels in excitable cells. These agents are known to have their maximal potency in the smooth muscle tissue, especially in the vascular smooth muscle. Much attention has been focused on the type of K-channel that is responsible for mediating the effects of KCOs. As the KCO-induced changes are antagonized by glibenclamide, an $K_{ATP}$ (ATP-sensitive K-channel) blocker in the pancreatic ${\beta}-cell,\;K_{ATP}$ was suggested to be the channel responsible. However, there also are many results in favor of other types of K-channel $$(maxi-K,\;small\;conductance\;K_{Ca,}\; SK_{ATP}) mediating the effects of KCOs. Effects of lemakalim, (-)enantiomer of cromakalim (BRL 34915), on the spontaneous contractions and slow waves, were investigated in the antral circular muscle of the guinea-pig stomach. Membrane currents and the effects on membrane currents and single channel activities were also measured in single smooth muscle cells and excised membrane patches by using the patch clamp method. Lemakalim induced hyperpolarization and inhibited spontaneous contractions in a dose-dependent manner. These effects were blocked by glibenclamide and low concentrations of tetraethyl ammonium (< mM). Glibenclamide blocked the effect of lemakalim on the membrane potential and slow waves. The mechanoinhibitory effect of lemakalim was blocked by pretreatment with glibenclamide. In a whole ceIl patch clamp condition, lemakalim largely increased outward K currents. These outward K currents were blocked by TEA, glibenclamide and a high concentration of intracelIular EGTA (10 mM). Volatage-gated Ca currents were not affected by lemakalim. In inside-out patch clamp experiments, lemakalim increased the opening frequency of the large conductance $Ca^{2+}-activated$ K channels $(BK_{Ca},\;Maxi-K).$ From these results, it is suggested that lemakalim induces hyperpolarization by opening K-channels which are sensitive to internal Ca and such a hyperpolarization leads to the inhibition of the spontaneous contraction.

• The Korean Journal of Physiology and Pharmacology
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• v.12 no.6
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• pp.337-342
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• 2008

Human bone marrow mesenchymal stem cells (hBM-MSCs) represent a potentially valuable cell type for clinical therapeutic applications. The present study was designed to evaluate the effect of long-term culturing (up to $10^{th}$ passages) of hBM-MSCs from eight individual amyotrophic lateral sclerosis (ALS) patients, focusing on functional ion channels. All hBM-MSCs contain several MSCs markers with no significant differences, whereas the distribution of functional ion channels was shown to be different between cells. Four types of $K^+$ currents, including noise-like $Ca^{+2}$-activated $K^+$ current ($IK_{Ca}$), a transient outward $K^+$ current ($I_{to}$), a delayed rectifier $K^+$ current ($IK_{DR}$), and an inward-rectifier $K^+$ current ($K_{ir}$) were heterogeneously present in these cells, and a TTX-sensitive $Na^+$ current ($I_{Na,TTX}$) was also recorded. In the RT-PCR analysis, Kv1.1,, heag1, Kv4.2, Kir2.1, MaxiK, and hNE-Na were detected. In particular, ($I_{Na,TTX}$) showed a significant passage-dependent increase. This is the first report showing that functional ion channel profiling depend on the cellular passage of hBM-MSCs.