Removal of sodium channel inactivation in squid axon by the oxidant chloramine-T.

Wang, Ging Kuo; Brodwick, Malcolm S.; Eaton, Douglas C.

doi:10.1085/jgp.86.2.289

Cited by 64 publications

(46 citation statements)

References 33 publications

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“…When 3.6 mM chloramine-T was included in the external solution the sodium currents were prolonged, indicating a removal of sodium inactivation as reported by Wang et al (1985). Concomitantly the birefringence traces were altered, the slow phases were removed and the rapid phases at the beginning and the end of the pulse became the same size (Fig.…”

Section: Chloramine-t Removes the Slow Phasesupporting

confidence: 61%

“…This paper presents more kinetic data on the slow birefringence responses and examines the effects of chloramine-T, a mild oxidant, which prolongs sodium currents (Wang, Brodwick & Eaton, 1985) and prevents immobilization of gating charge (Tanguy & Yeh, 1988). Two other agents which modify sodium currents and gating currents have been tested for effects on the birefringence change.…”

Section: Introductionmentioning

confidence: 99%

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Chloramine-T alters the nerve membrane birefringence response

Landowne

1990

J. Membrain Biol.

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The change in birefringence during depolarizing voltage-clamp pulses of internally perfused squid giant axons are biphasic. There is a rapid decrease in birefringence with a 220-microsec half time at 8 degrees C followed by a slow decrease over the next several milliseconds. After the pulse there is a rapid recovery which is smaller than the initial rapid decrease followed by a slow recovery phase. The rate of change of the slow phase during the pulse is more rapid for larger depolarizations. After the pulse the rate of change is more rapid for more negative potentials. 3.6 mM chloramine-T, applied externally until the sodium currents were prolonged and inactivation was removed, removed the slow phase of the birefringence response both during and after the pulse and made the fast 'off' response as large as the fast 'on' response. Two anesthetics reduced the birefringence response by about 20%. A rocking helix model is presented which relates the birefringence findings and earlier gating current experiments.

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Section: Chloramine-t Removes the Slow Phasesupporting

confidence: 61%

Section: Introductionmentioning

confidence: 99%

Chloramine-T alters the nerve membrane birefringence response

Landowne

1990

J. Membrain Biol.

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“…ChT is an oxidizing agent that preferentially oxidizes methionine to methionine sulfoxide (MetO) but it can also oxidize cysteine. Selective oxidation of methionine to MetO by ChT (< 10 mM) has been demonstrated in different proteins [33][34][35][36][37][38][39][40]. Particularly in other ion channels, ChT does indeed act as a Met-preferring oxidizing agent as demonstrated by using electrophysiology and site-directed mutagenesis [20,23].…”

Section: Discussionmentioning

confidence: 98%

Functional consequences of methionine oxidation of hERG potassium channels

Limberis

Martin

et al. 2007

Biochemical Pharmacology

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Reactive species oxidatively modify numerous proteins including ion channels. Oxidative sensitivity of ion channels is often conferred by amino acids containing sulfur atoms, such as cysteine and methionine. Functional consequences of oxidative modification of methionine in hERG1 (human ether à go-go related gene 1), which encodes cardiac I Kr channels, are unknown. Here we used chloramine-T (ChT), which preferentially oxidizes methionine, to examine the functional consequences of methionine oxidation of hERG channels stably expressed in a human embryonic kidney cell line (HEK 293) and native hERG channels in a human neuroblastoma cell line (SH-SY5Y). ChT (300 µM) significantly decreased whole-cell hERG current in both HEK 293 and SH-SY5Y cells. In HEK 293 cells, the effects of ChT on hERG current were time-and concentration-dependent, and were markedly attenuated in the presence of enzyme methionine sulfoxide reductase A that specifically repairs oxidized methionine. After treatment with ChT, the channel deactivation upon repolarization to −60 or −100 mV was significantly accelerated. The effect of ChT on channel activation kinetics was voltage-dependent; activation slowed during depolarization to +30 mV but accelerated during depolarization to 0 or −10 mV. In contrast, the reversal potential, inactivation kinetics, and voltage-dependence of steady-state inactivation remained unaltered. Our results demonstrate that the redox status of methionine is an important modulator of hERG channel.

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“…In view of reports that sodium channel inactivation can be modified by chemical reagents applied to the external membrane surface (Nonner et al 1980;Wang et al 1985), we examined the effects of SITS and NBA applied to the outside of GH3 cells using the U-tube apparatus. As opposed to the effects seen with internal application (Fig.…”

Section: External Chemical Modification Of K+ Channel Inactivationmentioning

confidence: 99%

“…Our present concepts regarding the molecular mechanisms of inactivation gating in Na+ channels have arisen not only from detailed biophysical analysis of behaviours at the single-and multichannel level, but also from attempts to selectively modify these behaviours with group-specific chemical reagents and enzymes. Clues concerning the membrane orientation and nature of reactive residues involved in inactivation have resulted from this approach (Oxford, Wu & Narahashi, 1978;Eaton, Brodwick, Oxford & Rudy, 1978;Nonner, Spaulding & Hille, 1980;Brodwick & Eaton, 1982;Wang, Brodwick & Eaton, 1985;Rack, Rubly & Waschow, 1986;Gonoi & Hille, 1987). Modification of inactivation by these agents has also been manifest at the single-channel level and has aided in discrimination of gating models (Patlak & Horn, 1982).…”

Section: Introductionmentioning

confidence: 99%

The inactivating K+ current in GH3 pituitary cells and its modification by chemical reagents.

Oxford

Wagoner

1989

The Journal of Physiology

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SUMMARY1. Whole-cell and single-channel recording techniques were applied to the study of the permeability and gating of inactivating K+ channels from clonal pituitary cells.2. The cation selectivity sequence (measured from reversal potentials) for the channels underlying the inactivating K+ current was TlV > K+ > Rb+ > NH4+. The conductance sequence (determined from current amplitudes) was K+ = Tl > Rb+ > NH4t3. The inactivating current (IK(i)) which was blocked by 4-aminopyridine (4-AP), activated at voltages more positive than -40 mV and half-inactivated at that voltage. Inactivation proceeded as the sum of two exponentials with mean time constants of 21 and 82 ms. Deactivation followed a single-exponential time course.4. Recovery from inactivation was slow, voltage dependent and multi-exponential, taking more than 50 s near the cell's resting potential.5. The magnitudes of outward current and of slope conductance increased as the concentration of external K+ was increased.6. On-cell and outside-out membrane patches revealed minicurrents with gating and pharmacological properties identical to whole-cell currents. 'Single channels with inactivating characteristics, while rarely observed, had an average slope conductance of 6-8 pS.7. Intracellular application of the disulphonic stilbene derivative, SITS, and the protein-modifying reagent, N-bromoacetamide (NBA), at concentrations of 0 2-1 mm for several tens of minutes dramatically slowed the decay (inactivation) of K+ currents and caused coincident increases in the magnitude of outward IK(i).8. Extracellular application of NBA at much lower concentrations (1-100 1uM) and much shorter exposure times (1-30 s) also slowed inactivation. This effect was reversible for brief applications at low doses, but became irreversible after longer exposures.9. Both internal and external NBA shifted the steady-state inactivation-voltage relation by+ 10 mV and reduced inactivation at voltages more positive than 0 mV.10. The efficacy of external NBA was independent of holding potential between -80 and 0 mV.

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Removal of sodium channel inactivation in squid axon by the oxidant chloramine-T.

Cited by 64 publications

References 33 publications

Chloramine-T alters the nerve membrane birefringence response

Chloramine-T alters the nerve membrane birefringence response

Functional consequences of methionine oxidation of hERG potassium channels

The inactivating K+ current in GH3 pituitary cells and its modification by chemical reagents.

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