The potential-dependent K+ channel in molluscan neurones is organized in a cluster of elementary channels

Kazachenko, V.N.; Geletyuk, V.I.

doi:10.1016/0005-2736(84)90558-3

Cited by 37 publications

(16 citation statements)

References 17 publications

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“…Indeed, these fluctuations were resolved clearly to be unitary two-state events (1). Subsequently, data were reported confirming that twostate behavior was induced by EIM and, in addition, described two new features in the current response (17,18 21). Indeed, recordings showed clearly responses that were described as consisting of "three transitions" (figure 6 in ref.…”

Section: Discussionmentioning

confidence: 72%

“…With regard to a complex of channels acting as a unit, it should be noted that a unit consisting of two channels was postulated to interpret current data obtained on extracted from Torpedo californica electroplax inserted into the planar lipid bilayers (19). Recently, in cell membranes, evidence has been obtained with the voltage patch-clamp method for multilevel currents in mouse pulmonary alveolar epithelial cells (20), molluscan neurons (21,22), and renal tubules (23). In each case, two alternative hypotheses are considered to explain the patch current recordings: the current arises from either a single channel or a "cluster" of channels acting as a unit.…”

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Voltage gating of conductance in lipid bilayers induced by porin from outer membrane of Neisseria gonorrhoeae.

Mauro

Blake

Labarca

1988

Proc. Natl. Acad. Sci. U.S.A.

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Porins, polypeptides of =35 kDa, are present as integral membrane proteins in the outer membranes of a variety of Gram-negative bacteria. As reported previously for a purified porin from Escherichia coli, voltage gating of conductance was found to be induced in a lipid bilayer by the solubilized purified porin, protein I, from Neisseria gonorrhoeae. The unitary response to an applied potential showed a cascade of current from an initial level through at least three levels, more or less equal, to a persisting lower level. The initial level of current corresponded to 1.0-1.3 nS for 0.2 M NaCl on either side of the bilayer. Briefly reducing the potential to zero restored the current to its initial level. Interpretation of the unitary response is suggested by electron microscopic data obtained on negatively stained outer membranes of E. coli indicating the presence of "pores" appearing in triplets. Moreover, low-resolution x-ray and neutron diffraction studies on crystals obtained with an E. coli porin show that three polypeptides associate to form a unit. Combining such structural data with the present electrical data lends support for the hypothesis that the unitary response results from three pores acting as a unit in response to an applied potential. Evidence obtained with the patch-clamp technique is mounting for a similar mechanism of many channels operating as a unit in a variety of cell membranes. The porin channel holds promise as a concrete model for the analysis of voltage gating of ionic conductance.

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Section: Discussionmentioning

confidence: 72%

Section: Discussionmentioning

confidence: 99%

Voltage gating of conductance in lipid bilayers induced by porin from outer membrane of Neisseria gonorrhoeae.

Mauro

Blake

Labarca

1988

Proc. Natl. Acad. Sci. U.S.A.

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“…This has also been reported to be the case in Helix nerve cells by Ewald et al (1985), by Kazachenko & Geletyuk (1984) with voltage-dependent K+ channels, by Taylor (1987) and Ram & Dagan (1987) with A-channels, and by Partridge & Swandulla (1987) with Ca2+-activated cation channels. The discrete channel localization from a variety of preparations has been reviewed by Almers & Stirling (1984).…”

Section: Channel Clusteringmentioning

confidence: 80%

Ca2(+)‐activated K+ current involvement in neuronal function revealed by in situ single‐channel analysis in Helix neurones.

Gola

Ducreux

Chagneux

1990

The Journal of Physiology

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SUMMARY1. The properties of single calcium-activated potassium channels (or C-channels) were studied in cell-attached patches using the patch-clamp technique. Experiments were performed on identified Ca2+-dependent U cells in juvenile specimens (1-2 months old) of Helix aspersa.2. The criteria used to identify C-channels were based on comparison between macroscopic C-currents and currents reconstructed from unitary recordings. Both currents had a slow activation rate at large positive potentials which turned into fast activation after large Ca2+ entries. Both currents were blocked by intracellularly injected EGTA. 4. C-channels in U cells were distributed in clusters of three to ten channels (mean 5-05 channels in seventy-five patches). Calcium channels were present in patches containing clustered C-channels. C-channels within clusters behaved independently. 5. With patch electrode containing 8 mM-calcium, C-channels opened transiently upon patch depolarization. Reopenings in quiescent depolarized patches were induced by whole-cell spikes triggered by current pulses applied to an intracellular electrode. Apparent inactivation of C-channels in depolarized patches was in fact due to a decrease in [Ca2+]i resulting from inactivation of Ca2+ channels.6. Calcium-free saline solutions in the patch electrodes prevented C-channels from opening upon patch depolarization. Entry of calcium through the surrounding membrane induced delayed openings in the patch. Peak opening probability PO occurred 330 + 30 ms after a brief Ca2+ entry with a lag period of 50-80 ms. With patch electrodes filled with Ca2+-containing saline solutions and under conditions which maximized C-channel opening, peak P1 was reached in 20-50 ms. The same value was observed for the whole-cell C-current.7. The peak P. at a given patch potential and in response to a whole-cell spike was not altered by a previous long-lasting patch depolarization, or by producing several * To whom correspondence should be addressed. MS 7550M. GOLA, C. DUCREUX AND H. CHAGNEUX successive Ca2+ entries. Thus, C-channels did not appear to be inactivated by depolarization or increase in [Ca2+]i.8. C-channels were found to be relatively highly voltage dependent, with an e-fold increase in PO per 14-9 mV increase in potential. The location of the PO-V curve on the voltage axis, but not its shape, was variable along a 60 mV span. Openings were never observed at potentials below -30 mV.9. Increasing Ca2+ influxes shifted the PO-V relationship towards negative potentials. Reverse shifts were observed during the PO decay following a brief Ca2+ entry.10. The latency to first opening was of 80-100 ms when patch depolarizations were applied immediately after a brief Ca2+ entry. The latency decreased to 10-20 ms when the depolarization was applied 300-600 ms after the Ca2+ entry. These data would indicate that the C-current activation was rate limited by calcium while the voltage-dependent step had fast kinetics.11. The distributions of open time, closed time and burst duration were con...

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“…Cooper & Shrier (1985) report an open-channel conductance of 22 pS for A-current channels in rat nodose ganglia cells, while Kazachenko & Geletyuk (1984) report a single-channel conductance of 40 pS for the fast channels in Lymnaea stagnalis neurone soma.…”

Section: Microscopic A-current Measurementsmentioning

confidence: 99%

“…The ionic selectivity of single-channel currents was reported in one publication but the channels could not be unequivocally identified as A-current channels (Kazachenko & Geletyuk, 1984). Recently, single-channel analysis of the A-current from rat nodose neurones has been published (Cooper & Shrier, 1985).…”

Section: Introductionmentioning

confidence: 99%

Selectivity and patch measurements of A‐current channels in Helix aspersa neurones.

Taylor

1987

The Journal of Physiology

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SUMMARY1. The ionic selectivity ofA-current K+ channels has been measured in single Helix aspersa neurones by recording the reversal potential shift in test solutions containing various monovalent cations.2. The A-current channel is permeable to Tl+, K+, Rb+, NH4+ and Cs+. The channels may also be sparingly permeable to Na+ and Li+. Organic cations have an apparent small permeability as judged from their reversal potentials, but this may be an artifact of K+ accumulation.3. A large patch electrode (3 ,m tip) isolated a region that appeared to contain only A-current channels. This may indicate that A-current channels are found in the membrane as rafts of at least 3 gtm in diameter.4. The single-channel conductance calculated from single-channel current steps was 14 pS.

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The potential-dependent K+ channel in molluscan neurones is organized in a cluster of elementary channels

Cited by 37 publications

References 17 publications

Voltage gating of conductance in lipid bilayers induced by porin from outer membrane of Neisseria gonorrhoeae.

Voltage gating of conductance in lipid bilayers induced by porin from outer membrane of Neisseria gonorrhoeae.

Ca2(+)‐activated K+ current involvement in neuronal function revealed by in situ single‐channel analysis in Helix neurones.

Selectivity and patch measurements of A‐current channels in Helix aspersa neurones.

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