Single inwardly rectifying potassium channels in cultured muscle cells from rat and mouse.

Matsuda, Hiroko; Stanfield, Peter

doi:10.1113/jphysiol.1989.sp017679

Cited by 50 publications

(46 citation statements)

References 29 publications

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“…The tissue distribution of HIR transcripts overlaps with that reported for IRK1-and GIRK1/KGArelated messages (13)(14)(15)(16). This mRNA colocalization parallels the observation that single cells can display both smalland large-conductance inwardly rectifying K+ channels (29)(30)(31)(32). Developmental regulation or formation of heteromultimeric inward rectifiers may provide additional functional diversity (30,32).…”

Section: Discussionsupporting

confidence: 58%

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Primary structure and characterization of a small-conductance inwardly rectifying potassium channel from human hippocampus.

Périer

Radeke

Vandenberg

1994

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

126

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We have isolated a human hippocampus cDNA that encodes an inwardly reying potasi channel, termed HIR (hippocampal inward rectifier), with strong rectifcation characteristics. Single-channel recordings indicate that the HIR channel has an unusually small conductance (13 pS), diinguishing HIR from other cloned inward rectifiers.RNA blot analyses show that HIR transcripts are present in heart, skeletal muscle, and several different brain regions, including the hippocampus.K+ channels constitute a highly diverse group including voltage-gated and Ca2+-activated channels belonging to the Shaker superfamily (1) and a distinct class of channels, the inward rectifiers. Inwardly rectifying K+ channels are characterized by a decrease in K+ conductance as the membrane potential becomes positive with respect to the K+ equilibrium potential (EK); as a result, these channels carry large inward currents and small outward currents (2).The asymmetrical conductances of inward rectifiers are critical for the maintenance and modulation of cellular excitability. Inward rectifiers constitute the major class of K+ channels in the heart, where they are involved in the onset and termination of the long-duration action potentials, in the regulation of heart-beat frequency, and in the determination of the resting potential (2-4). In the central nervous system, inwardly rectifying K+ currents are present in neuronal and nonneuronal cells, including hippocampal neurons and astrocytes (5-8), and are thought to participate in electrical signaling and information processing.In contrast to the fixed voltage-dependence of most ion channel mechanisms, the voltage-dependence of inward rectification varies with the external K+ concentration ([K+]O), causing the voltage at which rectification occurs to shift in parallel with EK. Open channel block by internal Mg2+ is the primary cause ofboth rapid inward rectification (9-11) and the dependence of rectification on external K+ (9,11,12 The primary structures of three inwardly rectifying K+ channels, ROMK1, IRK1, and GIRK1/KGA have been reported recently (13-16). These inward rectifiers show homologies with K+ channels of the Shaker superfamily in the H5 domain, thought to be the central core of the channel pore (13, 14), but are markedly different in other regions. In addition, only two putative membrane-spanning domains bracket the H5 region of inward rectifier polypeptides, in contrast to the six transmembrane domains of Shaker-type K+ channels.We have cloned a cDNA encoding a human inwardly rectifying K+ channel, HIR (hippocampal inward rectifier), present in brain and muscle tissues.* We have expressed the HIR channel in Xenopus oocytes, and we have shown that it is a classical strong inward rectifier, displaying large inward currents and minimal outward currents. The amino acid sequence of HIR has homology to those of other inward rectifiers but contains significant differences, indicating that HIR is a previously unreported member of the inward rectifier family. Electrophysiological analy...

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Section: Discussionsupporting

confidence: 58%

“…5a). As noted for many other strongly inwardly rectifying K+ channels, HIR gating kinetics were slow, with long open times at negative potentials and a reduction in channel open time at very negative potentials (14,24,25,(28)(29)(30)(31)(32).…”

mentioning

confidence: 99%

Primary structure and characterization of a small-conductance inwardly rectifying potassium channel from human hippocampus.

Périer

Radeke

Vandenberg

1994

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

126

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“…Although subconductance levels have also been found in 2TM K ϩ channels [KcsA (5, 9-11) and K IR (15)(16)(17)], only a little is known about the underlying mechanism. In K IR 2.1, Xie et al (17) suggested that the binding of a single PIP 2 leads to opening of subconductance levels and full opening of the channel.…”

mentioning

confidence: 99%

Fluorescence detection of the movement of single KcsA subunits reveals cooperativity

Blunck

McGuire

Hyde

et al. 2008

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

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The prokaryotic KcsA channel is gated at the helical bundle crossing by intracellular protons and inactivates at the extracellular selectivity filter. The C-terminal transmembrane helix has to undergo a conformational change for potassium ions to access the central cavity. Whereas a partial opening of the tetrameric channel is suggested to be responsible for subconductance levels of ion channels, including KcsA, a cooperative opening of the 4 subunits is postulated as the final opening step. In this study, we used single-channel fluorescence spectroscopy of KcsA to directly observe the movement of each subunit and the temporal correlation between subunits. Purified KcsA channels labeled at the C terminus near the bundle crossing have been inserted into supported lipid bilayer, and the fluorescence traces analyzed by means of a cooperative or independent Markov model. The analysis revealed that the 4 subunits do not move fully independently but instead showed a certain degree of cooperativity. However, the 4 subunits do not simply open in 1 concerted step.gating ͉ ion channel ͉ single-molecule

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“…Both P o and kinetic parameters depended on the pipette solution used. This dependence is not directly due to the change in [K + ] o , but to a voltage-dependent block by Na + [23]. With 25 mM [K + ] solution, P o declined markedly upon changing from a slightly negative pipette potential to strongly hyperpolarizing potentials (Fig.…”

Section: Delayed-rectifier K + Channels (K Dr )mentioning

confidence: 96%

“…With pipette [K + ] above physiological levels, inwards currents with long-lasting openings and low open-state noise, typical of K IR channels [17,23,28], could be observed in several cell-attached recordings (Fig. 2).…”

Section: Inwards-rectifying K + Channels (K Ir )mentioning

confidence: 99%

Maturation and myotonia influence the abundance of cation channels KDR, KIR and CIR differently: a patch-clamp study on mouse interosseus muscle fibres

Kurtz

Schirm

Jockusch

1999

Pflügers Arch – Eur J Physiol

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To detect cation channels, the expression of which is dependent on the physiological state of muscle, single-channel activities of dissociated fibres of the mouse interosseus muscle were recorded using the patch-clamp technique in the cell-attached mode. Fibres were prepared from juvenile and adult wild-type (WT), from chloride channel-deficient myotonic and from denervated adult WT muscles. In all cases delayed-rectifier K + channels (K DR ) with a unitary conductance of 11 pS were recorded in more than 95% of sarcolemmal patches, but with a low, steady-state open probability. Inwards-rectifying K + channels (K IR ) with a conductance of 31 pS in 140 mM [K + ] o were active in about 50% of the membrane patches from WT and in more than 90% of those from myotonic fibres. A hitherto undescribed, inwards-rectifying, cation channel, provisionally termed C IR , with fast kinetics and a unitary conductance of 36 pS, was active in nearly every membrane patch from juvenile mice, both WT and myotonic. The abundance of C IR decreased during development, but was not changed 7 days after denervation of adult WT muscle. Ca 2+ -dependent K + channels were seen sporadically. Channels with the characteristics of adenosine 5'-triphosphate (ATP)-sensitive K + channels were recorded frequently upon excision of membrane patches, but remained inactive in most cell-attached recordings. In conclusion, of the investigated ion channels, only K IR was responsive to the activity pattern of adult muscle, whereas C IR was down-regulated during muscle maturation.

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Single inwardly rectifying potassium channels in cultured muscle cells from rat and mouse.

Cited by 50 publications

References 29 publications

Primary structure and characterization of a small-conductance inwardly rectifying potassium channel from human hippocampus.

Primary structure and characterization of a small-conductance inwardly rectifying potassium channel from human hippocampus.

Fluorescence detection of the movement of single KcsA subunits reveals cooperativity

Maturation and myotonia influence the abundance of cation channels KDR, KIR and CIR differently: a patch-clamp study on mouse interosseus muscle fibres

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