Internal and external K+ help gate the inward rectifier

Cohen, Ira S.; DiFrancesco, Dario; Mulrine, N K; Pennefather, Peter

doi:10.1016/s0006-3495(89)82792-4

Cited by 33 publications

(46 citation statements)

References 19 publications

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“…In the presence of Spm, the time course of the deactivation was so fast that the time constant could not be determined by the envelope test (n = 6). These findings support further the idea that Spm is the blocking molecule of the channel causing the non-conductive state C. (Ishihara et al 1989;Cohen, DiFrancesco, Mulrine & Pennefather, 1989) and in the IRK1 channel (Stanfield et al 1994a). Using the pipettes containing 1 mm free Mg2+, we confirmed that the increase of the channels in the state C also becomes slower as the depolarization becomes larger (Fig.…”

Section: Solutionssupporting

confidence: 88%

The tetravalent organic cation spermine causes the gating of the IRK1 channel expressed in murine fibroblast cells.

Ishihara

Hiraoka

Ochi

1996

The Journal of Physiology

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1. The activation kinetics of the IRK1 channel stably expressed in L cells (a murine fibroblast cell line) were studied under the whole-cell voltage clamp. Without polyamines or Mg2+ in the pipettes, inward currents showed an exponential activation on hyperpolarization. The steep inward rectification of the currents around the reversal potential (Erev) could bedescribed by the open-close transition of the channel with first-order kinetics. 2. When the tetravalent organic cation spermine (Spm) was added in the pipettes, the activation kinetics changed; this was explicable by the increase in the closing rate constant.The activation of the currents observed without Spm or Mg2+ in the pipettes was ascribed to the unblocking of the 'endogenous-Spm block'.3. In the presence of the divalent cation putrescine (Put) (Hagiwara, Miyazaki & Rosenthal, 1976;Leech & dependent activation following an instantaneous current Stanfield, 1981;Kurachi, 1985). As the mechanism jump on hyperpolarization. The steep inward rectification accounting for this inward rectification, the block of the around the reversal potential (Erev), and the time-channel by an internal molecule has been proposed dependent property of the currents have been described (Hagiwara & Takahashi, 1974;Hille & Schwarz, 1978). The by the open-close transition of the activation gate, which intracellular cations Mg2+ (Horie,

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Section: Solutionssupporting

confidence: 88%

The tetravalent organic cation spermine causes the gating of the IRK1 channel expressed in murine fibroblast cells.

Ishihara

Hiraoka

Ochi

1996

The Journal of Physiology

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“…Time-dependent activation of Kir2.1 is dependent on external K ϩ concentration and is reduced as the external K ϩ is increased (27,28). With Kir2.1, this was shown to be due to competition between K ϩ and polyamines (28).…”

Section: Effect Of H5 Mutations On Slowmentioning

confidence: 99%

Residues and Mechanisms for Slow Activation and Ba2+Block of the Cardiac Muscarinic K+ Channel, Kir3.1/Kir3.4

Lancaster¹,

Dibb²,

Quinn³

et al. 2000

Journal of Biological Chemistry

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Mechanisms and residues responsible for slow activation and Ba 2؉ block of the cardiac muscarinic K ؉ channel, Kir3.1/Kir3.4, were investigated using site-directed mutagenesis. Mutagenesis of negatively charged residues located throughout the pore of the channel (in H5, M2, and proximal C terminus) reduced or abolished slow activation. The strongest effects resulted from mutagenesis of residues in H5 close to the selectivity filter; mutagenesis of residues in M2 and proximal C terminus equivalent to those identified as important determinants of the activation kinetics of Kir2.1 was less effective. In giant patches, slow activation was present in cell-attached patches, lost on excision of the patch, and restored on perfusion with polyamine. Mutagenesis of residues in H5 and M2 close to the selectivity filter also decreased Ba 2؉ block of the channel. A critical residue for Ba 2؉ block was identified in Kir3.4. Mutagenesis of the equivalent residue in Kir3.1 failed to have as pronounced an effect on Ba 2؉ block, suggesting an asymmetry of the channel pore. It is concluded that slow activation is principally the result of unbinding of polyamines from negatively charged residues close to the selectivity filter of the channel and not an intrinsic gating mechanism. Ba 2؉ block involves an interaction with the same residues.

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“…For the/~r channel in frog skeletal muscle fibers, "tact is <5 ms at 13~ (Leech and Stanfield, 1981). For the cardiac background/~r channel (iKl), "r~t is <5 ms at 30-370C (Kurachi, 1985;Tourneur, Mitra, Morad, and Rougier, 1987;Harvey and Ten Eick, 1988) and can be slowed down to <10 ms at 14-15~ (Saigusa and Matsuda, 1988;Ishihara et al, 1989) and <20 ms at 8-10~ (Cohen, DiFrancesco, Mulrine, and Pennefather, 1989). For the/~r channel current in bovine pulmonary endothelial cells, %ct is <5 ms at 20-23~ (Silver and DeCoursey, 1990).…”

Section: Comparison Of Intrinsic Girki Gating With Other Ir Channelsmentioning

confidence: 99%

Intrinsic gating properties of a cloned G protein-activated inward rectifier K+ channel.

Doupnik

Lim

Kofuji

et al. 1995

The Journal of General Physiology

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The voltage-, time-, and K § properties of a G proteinactivated inwardly rectif~ng K + channel (GIRK1/KGA/Kir3.1) cloned from rat atrium were studied in Xenopus oocytes under two-electrode voltage clamp. During maintained G protein activation and in the presence of high external K + (Vx = 0 mV), voltage jumps from Vx to negative membrane potentials activated inward GIRK1 K + currents with three distinct time-resolved current components. GIRK1 current activation consisted of an instantaneous component that was followed by two components with time constants q'f r~50 ms and x, ,-0400 ms. These activation time constants were weakly voltage dependent, increasing approximately twofold with maximal hyperpolarization from Vx. Voltage-dependent GIRK1 availability, reveaied by tail currents at -80 mV after long prepulses, was greatest at potentials negative to Vx and declined to a plateau of approximately half the maximal level at positive voltages. Voltage-dependent GIRK1 availability shifted with VK and was half maximal at VK--20 mV; the equivalent gating charge was ,'d.6 e-. The voltage-dependent gating parameters of GIRK1 did not significantly differ for G protein activation by three heterologously expressed signaling pathways: m2 muscarinic receptors, serotonin 1A receptors, or G protein 131~/2 subunits. Voltage dependence was also unaffected by agonist concentration. These results indicate that the voltage-dependent gating properties of GIRK1 are not due to extrinsic factors such as agonist-receptor interactions and G proteinchannel coupling, but instead are analogous to the intrinsic gating behaviors of other inwardly rectifying K + channels.

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Internal and external K+ help gate the inward rectifier

Cited by 33 publications

References 19 publications

The tetravalent organic cation spermine causes the gating of the IRK1 channel expressed in murine fibroblast cells.

The tetravalent organic cation spermine causes the gating of the IRK1 channel expressed in murine fibroblast cells.

Residues and Mechanisms for Slow Activation and Ba2+Block of the Cardiac Muscarinic K+ Channel, Kir3.1/Kir3.4

Intrinsic gating properties of a cloned G protein-activated inward rectifier K+ channel.

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