Effect of sulfhydryl oxidoreduction on permeability of cardiac tetrodotoxin-insensitive sodium channel

Kurata, Yasutaka; Hisatome, Ichiro; Tsuboi, Mariko; Uenishi, Hiroaki; Zhang, G.; Oyaizu, M.; Satō, Ryōichi; Imanishi, Sunao

doi:10.1016/s0024-3205(98)00364-6

Cited by 18 publications

(19 citation statements)

References 18 publications

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“…In the case of Na + channels, DTT, the reducing agent, has been reported to reduce extracellular native S-S bonds of Na + channels, which frees the SH group to block tetrodotoxin-insensitive Na + channels, thereby inducing thiol-dependent redoxmediated conformational changes of Na + channels pore. 14,15 In the present study, after exposure to DTT, L-cysteine did not affect the hH1, indicating that the site of Na + channel for L-cysteine corresponds to that for DTT. While it remains unknown whether the reduction of native S-S bonds of the Na + channels can inhibit the Na + current, the disulfide bridge formation in the pore region of the channel will change conductance, as described by Benitah et al 21 Thus, it is likely that L-cysteine, as well as DTT, reduces the native S-S bonds of hH1 to free SH groups and thus block hH1.…”

Section: L-cysteine Partially Blocks Na + Channelssupporting

confidence: 42%

L-Cysteine Prevents Oxidation-Induced Block of the Cardiac Na+ Channel Via Interaction With Heart-Specific Cysteinyl Residues in the P-Loop Region.

Yatsuhashi

Hisatome

Kurata

et al. 2002

Circ J

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The present study investigated the protective effects of L-cysteine on the oxidation-induced blockade of Na + channel -subunits, hH1 (cardiac) and hSkM1 (skeletal), expressed in COS7 cells. Na + currents were recorded by the whole-cell patch clamp technique (n = 3-7). L-cysteine alone blocked hH1 and hSkM1 in a dose-dependent manner, with saturating L-cysteine block at 3,000 mol/L. Hg 2+ , a potent sulfhydryl oxidizing agent, blocked hH1 with a time to 50% inhibition (Time50%) of 20 s. Preperfusion of COS7 cells with 100 mol/L Lcysteine significantly slowed the Hg 2+ block of hH1 (Time50% = 179 s). L-cysteine did not prevent Hg 2+ block of hSkM1 (Time50% = 37 s) or the C373Y hH1 mutant (Time50% = 43 s). As for other sulfo-amino acids, homocysteine prevented the Hg 2+ block of hH1, with the Time50% (70 s) being significantly smaller than that of L-cysteine, whereas methionine did not prevent the Hg 2+ block of hH1. L-cysteine did not prevent the Cd 2+ block of hH1. These results indicate that L-cysteine selectively acts on heart-specific Cys 373 in the P-loop region of hH1 to prevent Cys 373 from the oxidation-induced sulfur-Hg-sulfur bridge formation. (Circ J 2002; 66: 846 -850)

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Section: L-cysteine Partially Blocks Na + Channelssupporting

confidence: 42%

L-Cysteine Prevents Oxidation-Induced Block of the Cardiac Na+ Channel Via Interaction With Heart-Specific Cysteinyl Residues in the P-Loop Region.

Yatsuhashi

Hisatome

Kurata

et al. 2002

Circ J

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“…This is an indication that thimerosal-induced current can be rendered reversible and are not due to irreversible membrane permeability changes, and this may explain the data for the lower concentrations of HgCl 2 used in the present investigation. The immediate inhibitory effect of external 1,4-dithiothreitol [21,27] was attributed to an action on the external face of the cell [44], which leads us to arrive at a similar conclusion. It should be noted also that thiols are oxidized to disulfides by oxidizing agents such as HgCl 2 .…”

Section: Discussionmentioning

confidence: 54%

“…This is perhaps an indication that the action of HgCl 2 on OHCs was not due to a nonspecific effect but would perhaps suggest that the block was caused by sulfhydryl (-SH) oxidation, the important functional group of thiols [3]. Usually, mercurials are effective only when added to the cytoplasmic side of the membrane [25,27]. We observed an effect, however, when HgCl 2 was applied to the external face of the hair cell membrane.…”

Section: Discussionmentioning

confidence: 66%

“…This was much more evident at the high concentration of 100 mM than that for the lower dose of 1.0 mM. Most of the in vivo as well as in vitro studies have demonstrated similar abnormal status of biological preparations other than OHCs when exposed to higher levels of mercury concentrations [21,27]. Interestingly, in comparison to clinical data, concentrations of HgCl 2 at these levels are not for the most part manifested in large deficits in hearing thresholds shifts [14], although central auditory processing was largely affected by the mercury [35], but unfortunately, the high dose of dimethylmercury exposure in this case proved fatal to the patient.…”

Section: Discussionmentioning

confidence: 85%

“…Reversible block of a calcium-activated nonselective cation channel was observed in brown fat cells by the sulfhydryl reagent HgCl 2 as well as by thimerosal [25]. On the other hand, thimerosal completely reversed the effect of HgCl 2 in the whole cell recording mode [27]. This is an indication that thimerosal-induced current can be rendered reversible and are not due to irreversible membrane permeability changes, and this may explain the data for the lower concentrations of HgCl 2 used in the present investigation.…”

Section: Discussionmentioning

confidence: 98%

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The heavy metal mercury (Hg 2 + ) is an insidious environmental pollutant that causes toxic effects on sensory systems. It is well known that the group IIB divalent cation Hg 2 + is an inhibitor of the group I monovalent potassium (K + ) cation pore-forming channel in several biological preparations. Here, we used the whole cell patch clamp technique on freshly isolated outer hair cells (OHCs) of the guinea pig cochlea to record outward K + currents and inward K + currents treated with mercuric chloride (HgCl 2 ). HgCl 2 affected K + currents in a voltage-and dose-dependent manner. The effects of HgCl 2 at 1.0 -100 mM are more pronounced on onset peak current than on steady-state end current. HgCl 2 depolarized also the resting membrane potential. Although the effect of HgCl 2 at 1.0 mM was partially washed out over several minutes, the effects at 10 and 100 mM were irreversible to washout. Since K + channels of OHCs are targets for HgCl 2 ototoxicity, this may lead to auditory transduction problems, including a loss in hearing sensitivity. A better understanding of fundamental mechanisms underlying K + channelopathies in OHCs due to HgCl 2 poisoning may lead to better preventive or therapeutic agents. D

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Enhancement of plasmid DNA transformation efficiencies in early stationary‐phase yeast cell cultures

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et al. 2013

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Chemical-based methods have been developed for transformation of DNA into log phase cells of the budding yeast Saccharomyces cerevisiae with high efficiency. Transformation of early stationary phase cells, e.g., cells grown in overnight liquid cultures or as colonies on plates, is less efficient than log phase cells but is simpler and more adaptable to high throughput projects. In this study we have tested different approaches for transformation of early stationary phase cell cultures and identified a method utilizing polyethylene glycol (PEG), lithium acetate and dimethyl sulfoxide (DMSO) as most efficient. Plasmid DNA transformations using this method could be improved modestly by allowing cells to recover from the chemical treatment in rich broth before plating to selective media. Strong increases in transformation efficiencies were observed when cells were treated briefly with dithiothreitol (DTT). Tests using several different yeast strain backgrounds indicated that DTT treatment could enhance transformation efficiencies by up to 40-fold. Evaluation of multiple parameters affecting the efficiency of the method led to development of an optimized protocol achieving >50,000 transformants per µg DNA in most backgrounds tested.

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Effect of sulfhydryl oxidoreduction on permeability of cardiac tetrodotoxin-insensitive sodium channel

Cited by 18 publications

References 18 publications

L-Cysteine Prevents Oxidation-Induced Block of the Cardiac Na+ Channel Via Interaction With Heart-Specific Cysteinyl Residues in the P-Loop Region.

L-Cysteine Prevents Oxidation-Induced Block of the Cardiac Na+ Channel Via Interaction With Heart-Specific Cysteinyl Residues in the P-Loop Region.

Mercury (Hg2+) suppression of potassium currents of outer hair cells

Enhancement of plasmid DNA transformation efficiencies in early stationary‐phase yeast cell cultures

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