• Proceedings of the Korean Biophysical Society Conference
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• 1998.06a
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• pp.38-38
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• 1998

Resting membrane potential of atrial myocytes is less negative than K+ equilibrium potential, suggesting the presence of ion channels carrying inward currents. We investigated the background Na$\^$＋/ current in rat atrial myocytes using both conventional whole cell voltage clamp technique and single channel recording.(omitted)

• The Korean Journal of Physiology and Pharmacology
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• v.23 no.3
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• pp.219-227
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• 2019

Polycystic kidney disease 2-like-1 (PKD2L1), polycystin-L or transient receptor potential polycystin 3 (TRPP3) is a TRP superfamily member. It is a calcium-permeable non-selective cation channel that regulates intracellular calcium concentration and thereby calcium signaling. Although the calmodulin (CaM) inhibitor, calmidazolium, is an activator of the PKD2L1 channel, the activating mechanism remains unclear. The purpose of this study is to clarify whether CaM takes part in the regulation of the PKD2L1 channel, and if so, how. With patch clamp techniques, we observed the current amplitudes of PKD2L1 significantly reduced when co-expressed with CaM and $CaM{\triangle}N$. This result suggests that the N-lobe of CaM carries a more crucial role in regulating PKD2L1 and guides us into our next question on the different functions of two lobes of CaM. We also identified the predicted CaM binding site, and generated deletion and truncation mutants. The mutants showed significant reduction in currents losing PKD2L1 current-voltage curve, suggesting that the C-terminal region from 590 to 600 is crucial for maintaining the functionality of the PKD2L1 channel. With PKD2L1608Stop mutant showing increased current amplitudes, we further examined the functional importance of EF-hand domain. Along with co-expression of CaM, ${\triangle}EF$-hand mutant also showed significant changes in current amplitudes and potentiation time. Our findings suggest that there is a constitutive inhibition of EF-hand and binding of CaM C-lobe on the channel in low calcium concentration. At higher calcium concentration, calcium ions occupy the N-lobe as well as the EF-hand domain, allowing the two to compete to bind to the channel.

• Electronics and Telecommunications Trends
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• v.33 no.2
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• pp.39-47
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• 2018

The fundamental problem of communication is that of transmitting a message from a source to a destination over a channel through the use of a transmitter and receiver. To derive a theoretically optimal solution, the transmitter and receiver can be divided into several processing blocks, with each component analyzed and optimized. The idea of machine learning (or deep learning) communications systems goes back to the original definition of the communi-cation problem, and optimizes the transmitter and receiver jointly. Although today's systems have been optimized over the last decades, and it seems difficult to compete with their performance, deep learning based communication is attractive owing to its simplicity and the fact that it can learn to communicate over any type of channel without the need for mathematical modeling or analysis.

• Proceedings of the Korean Biophysical Society Conference
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• 2001.06a
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• pp.36-36
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• 2001

Small conductance $Ca^{2＋}$-activated $K^{+}$ channels (or S $K_{Ca}$ channels) are a group of $K^{＋}$-selective ion channels activated by sub-micromolar concentrations of intracellular $Ca^{2＋}$ independent of membrane voltage. We expressed a cloned S $K_{Ca}$ channel, rSK2, in Xenopus oocytes and investigated the monovalent cation selectivity of the channels. We have used site-directed mutagenesis and macro-channel recordings to identify amino acid residues influencing the ion selectivity.(omitted)d)

• Proceedings of the PSK Conference
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• 2002.10a
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• pp.349.1-349.1
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• 2002

Capsaicin. the pungent component of chili pepper. opens a novel cation selective ion channel in the plasma membrane of peripheral sensory neurons. Capsaicin channel agonists induce pain upon topical application in the early stage. which is followed by a period of desensitization. Although the agonists have been studied as a analgesics, their initial irritancy became sever side effect. So competive antagonists have been pursued as a novel pharmacological agent for analgesics, rather than agonists. (omitted)

• The Korean Journal of Physiology and Pharmacology
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• v.2 no.2
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• pp.133-145
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• 1998

$Ca^{2+}-signals$ in endothelial cells are determined by release from intracellular stores and entry through the plasma membrane. In this review, the nature of $Ca^{2+}$ entry and mechanisms of its control are reviewed. The following ion channels play a pivotal role in regulation of the driving force for $Ca^{2+}$ entry: an inwardly rectifying $K^+$ channel, identified as Kir2.1, a big-conductance, $Ca^{2+}-activated$ $K^+$ channel (hslo) and at least two $Cl^-$ channels (a volume regulated $Cl^-$ channel, VRAC, and a $Ca^{2+}$ activated $Cl^-$ channel, CaCC). At least two different types of $Ca^{2+}$-entry channels exist: 1. A typical CRAC-like, highly selective $Ca^{2+}$ channel is described. Current density for this $Ca^{2+}$ entry is approximately 0.1pA/pF at 0 mV and thus 10 times smaller than in Jurkat or mast cells. 2. Another entry pathway for $Ca^{2+}$ entry is a more non-selective channel, which might be regulated by intracellular $Ca^{2+}$. Although detected in endothelial cells, the functional role of trp1,3,4 as possible channel proteins is unclear. Expression of trp3 in macrovascular endothelial cells from bovine pulmonary artery induced non-selective cation channels which are probably not store operated or failed to induce any current. Several features as well as a characterisation of $Ca^{2+}$-oscillations in endothelial cells is also presented.

• Proceedings of the Korean Society of Applied Pharmacology
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• 1996.04a
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• pp.252-252
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• 1996

We Investigated the peripheral excitatory effect of capsaicin and KR-25018, a newly synthesized capsaicin derivative which was demonstrated to have a potent analgesic activity. KR-25018 and capsaicin were found to be both potent efficacious contractors of isolated guinea pig bronchial smooth muscle. KR-25018 was equipotent with capsaicin and [Sar$\^$9/,Met(O$_2$)$\^$11/]-substance P, 10-fold more potent than histamine and 10-fold less potent than (${\beta}$ -Ala$\^$8/)-neurokinin A(4-10), and their -log(M)EC$\_$50/ values were 6.94${\pm}$0.08, 6.86${\pm}$0.05, 6.96${\pm}$0.07, 5.64${\pm}$0.04, 7.96${\pm}$0.02, respectively. Contractile responses to KR-25018 and capsaicin were potentiated by phosphoramidon (1 ${\mu}$M), an inhibitor of neuropeptide-inactivating endopeptidase, but completely abolished in a calcium-free medium. These responses to KR-25018 and capsaicin were unaffected by the NK-1 antagonist CP96345 (1${\mu}$M), partially inhibited by the NK-2 antagonist SR48968 (1 ${\mu}$M) but almost completely abolished by a combination of the antagonists. A vanilloid receptor antagonist capsazepine competitively antagonized the responses to both KR-25018 and capsaicin (pA$_2$: aganst KR-25018, 5.98${\pm}$0.47; against capsaicin, 5.80${\pm}$0.31), and a capsaicin-sensitive cation channel antagonist ruthenium red caused significant reduction in the maximum responses to KR-25018 and capsaicin (pD'$_2$: against KR-25018, 4.61${\pm}$0.33; against capsaicin 4.96${\pm}$0.21). In conclusion, the present results suggest that KR-25018 and cpasaicin act on the same vanilloid receptor inducing the influx of calcium through ruthenium red-sensitive cation channel and produce contractile responses via the release of tachykinins that act on both NK-1 and NK-2 receptor subtypes.

• Journal of the Korean Chemical Society
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• v.28 no.1
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• pp.62-69
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• 1984

The reaction of toluene with ethanol was studied over various cation-exchanged pentasil zeolite catalysts. The toluene disproportionation reaction to produce xylenes increased with increasing reaction temperature and the activity of alkylation of toluene with ethanol showed maximum at around $400^{\circ}C$. Only Cs-ZSM-5 catalyst showed pronounced p-ethyltoluene selectivity increasing to 96% with increasing degree of Cs-exchange. The sorption rate of m-xylene was lower for Cs-exchanged ZSM-5 than H-ZSM-5 catalyst. These phenomena were interpreted in terms of shape selectivity arising from the partial blocking of channel intersections by large cesium ions.

• Animal cells and systems
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• v.11 no.2
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• pp.169-173
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• 2007

Hyperpolarization-activated nonselective cation channels (HCNs) play a pivotal role in producing rhythmic electrical activity in the heart and the nerve cells. In our previous experiments, voltage-dependent $Cd^{2+}$ access to one of the substituted cysteines in S6, T464C, supports the existence of an intracellular voltage-dependent activation gate. Direct binding of intracellular cAMP to HCN channels also modulates gating. Here we attempted to locate the cAMP-modulated structure that can modify the gating of HCN channels. SpHCN channels, a sea urchin homologue of the HCN family, became inactivated rapidly and intracellular cAMP removed this inactivation, resulting in about eight-fold increase of steady-state current level. T464C was probed with $Cd^{2+}$ applied to the intracellular side of the channel. We found that access of $Cd^{2+}$ to T464C was strongly gated by cAMP as well as voltage. Release of bound $Cd^{2+}$ by DMPS was also gated in a cAMP-dependent manner. Our results suggest the existence of an intracellular cAMP-modulated gate in the lower S6 region of spHCN channels.

• The Korean Journal of Physiology and Pharmacology
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• v.23 no.3
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• pp.191-201
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• 2019

The transient receptor potential canonical (TRPC) 5 channel, known as a nonselective cation channel, has a crucial role in calcium influx. TRPC5 has been reported to be activated by muscarinic receptor activation and extracellular pH change and inhibited by the protein kinase C pathway. Recent studies have also suggested that TRPC5 is extracellularly activated by englerin A (EA), but the mechanism remains unclear. The purpose of this study is to identify the EA-interaction sites in TRPC5 and thereby clarify the mechanism of TRPC5 activation. TRPC5 channels are over-expressed in human embryonic kidney (HEK293) cells. TRPC5 mutants were generated by site-directed mutagenesis. The whole-cell patch-clamp configuration was used to record TRPC5 currents. Western analysis was also performed to observe the expression of TRPC5 mutants. To identify the EA-interaction site in TRPC5, we first generated pore mutants. When screening the mutants with EA, we observed the EA-induced current increases of TRPC5 abolished in K554N, H594N, and E598Q mutants. The current increases of other mutants were reduced in different levels. We also examined the functional intactness of the mutants that had no effect by EA with TRPC5 agonists, such as carbachol or $GTP{\gamma}S$. Our results suggest that the three residues, Lys-554, His-594, and Glu-598, in TRPC5 might be responsible for direct interaction with EA, inducing the channel activation. We also suggest that although other pore residues are not critical, they could partly contribute to the EA-induced channel activation.