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Slow modal gating of single G protein-activated K+ channels expressed in Xenopus oocytes.
Yakubovich D, Pastushenko V, Bitler A, Dessauer CW, Dascal N.
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The slow kinetics of G protein-activated K+ (GIRK) channels expressed in Xenopus oocytes were studied in single-channel, inside-out membrane patches. Channels formed by GIRK1 plus GIRK4 subunits, which are known to form the cardiac acetylcholine (ACh)-activated GIRK channel (KACh), were activated by a near-saturating dose of G protein betagamma subunits (Gbetagamma; 20 nM). The kinetic parameters of the expressed GIRK1/4 channels were similar to those of cardiac KACh. GIRK1/4 channels differed significantly from channels formed by GIRK1 with the endogenous oocyte subunit GIRK5 (GIRK1/5) in some of their kinetic parameters and in a 3-fold lower open probability, Po. The unexpectedly low Po (0.025) of GIRK1/4 was due to the presence of closures of hundreds of milliseconds; the channel spent approximately 90 % of the time in the long closed states. GIRK1/4 channels displayed a clear modal behaviour: on a time scale of tens of seconds, the Gbetagamma-activated channels cycled between a low-Po mode (Po of about 0.0034) and a bursting mode characterized by an approximately 30-fold higher Po and a different set of kinetic constants (and, therefore, a different set of channel conformations). The available evidence indicates that the slow modal transitions are not driven by binding and unbinding of Gbetagamma. The GTPgammaS-activated Galphai1 subunit, previously shown to inhibit GIRK channels, substantially increased the time spent in closed states and apparently shifted the channel to a mode similar, but not identical, to the low-Po mode. This is the first demonstration of slow modal transitions in GIRK channels. The detailed description of the slow gating kinetics of GIRK1/4 may help in future analysis of mechanisms of GIRK gating.
Ashford,
Cloning and functional expression of a rat heart KATP channel.
1994, Pubmed
Ashford,
Cloning and functional expression of a rat heart KATP channel.
1994,
Pubmed Blatz,
Quantitative description of three modes of activity of fast chloride channels from rat skeletal muscle.
1986,
Pubmed Bünemann,
Downregulation of muscarinic M2 receptors linked to K+ current in cultured guinea-pig atrial myocytes.
1996,
Pubmed Chan,
Control of channel activity through a unique amino acid residue of a G protein-gated inwardly rectifying K+ channel subunit.
1996,
Pubmed
,
Xenbase Chan,
A recombinant inwardly rectifying potassium channel coupled to GTP-binding proteins.
1996,
Pubmed
,
Xenbase Colquhoun,
On the stochastic properties of single ion channels.
1981,
Pubmed Colquhoun,
Fast events in single-channel currents activated by acetylcholine and its analogues at the frog muscle end-plate.
1985,
Pubmed Corey,
Number and stoichiometry of subunits in the native atrial G-protein-gated K+ channel, IKACh.
1998,
Pubmed Dascal,
Atrial G protein-activated K+ channel: expression cloning and molecular properties.
1993,
Pubmed
,
Xenbase Dascal,
Signalling via the G protein-activated K+ channels.
1997,
Pubmed Delcour,
Multiple modes of N-type calcium channel activity distinguished by differences in gating kinetics.
1993,
Pubmed Delcour,
Altered prevalence of gating modes in neurotransmitter inhibition of N-type calcium channels.
1993,
Pubmed Duprat,
Heterologous multimeric assembly is essential for K+ channel activity of neuronal and cardiac G-protein-activated inward rectifiers.
1995,
Pubmed
,
Xenbase Grigg,
Single-channel properties of a G-protein-coupled inward rectifier potassium channel in brain neurons.
1996,
Pubmed Hedin,
Cloning of a Xenopus laevis inwardly rectifying K+ channel subunit that permits GIRK1 expression of IKACh currents in oocytes.
1996,
Pubmed
,
Xenbase Hess,
Different modes of Ca channel gating behaviour favoured by dihydropyridine Ca agonists and antagonists.
,
Pubmed Hille,
G protein-coupled mechanisms and nervous signaling.
1992,
Pubmed Huang,
Evidence that direct binding of G beta gamma to the GIRK1 G protein-gated inwardly rectifying K+ channel is important for channel activation.
1995,
Pubmed
,
Xenbase Huang,
Direct activation of inward rectifier potassium channels by PIP2 and its stabilization by Gbetagamma.
1998,
Pubmed
,
Xenbase Imredy,
Mechanism of Ca(2+)-sensitive inactivation of L-type Ca2+ channels.
1994,
Pubmed Inanobe,
Immunological and physical characterization of the brain G protein-gated muscarinic potassium channel.
1995,
Pubmed Iñiguez-Lluhi,
G protein beta gamma subunits synthesized in Sf9 cells. Functional characterization and the significance of prenylation of gamma.
1992,
Pubmed Ivanova-Nikolova,
Muscarinic K+ channel in the heart. Modal regulation by G protein beta gamma subunits.
1998,
Pubmed Ivanova-Nikolova,
Effector contributions to G beta gamma-mediated signaling as revealed by muscarinic potassium channel gating.
1997,
Pubmed Jan,
Receptor-regulated ion channels.
1997,
Pubmed Keynes,
Bimodal gating of the Na+ channel.
1994,
Pubmed Kim,
Modulation of acetylcholine-activated K+ channel function in rat atrial cells by phosphorylation.
1991,
Pubmed Kim,
ATP-dependent regulation of a G protein-coupled K+ channel (GIRK1/GIRK4) expressed in oocytes.
1997,
Pubmed
,
Xenbase Kirsch,
Trypsin activation of atrial muscarinic K+ channels.
1989,
Pubmed Kofuji,
Evidence that neuronal G-protein-gated inwardly rectifying K+ channels are activated by G beta gamma subunits and function as heteromultimers.
1995,
Pubmed
,
Xenbase Kozasa,
Purification of recombinant G proteins from Sf9 cells by hexahistidine tagging of associated subunits. Characterization of alpha 12 and inhibition of adenylyl cyclase by alpha z.
1995,
Pubmed Krapivinsky,
The G-protein-gated atrial K+ channel IKACh is a heteromultimer of two inwardly rectifying K(+)-channel proteins.
1995,
Pubmed
,
Xenbase Kubo,
Primary structure and functional expression of a rat G-protein-coupled muscarinic potassium channel.
1993,
Pubmed
,
Xenbase Kurachi,
G protein regulation of cardiac muscarinic potassium channel.
1995,
Pubmed Lesage,
Molecular properties of neuronal G-protein-activated inwardly rectifying K+ channels.
1995,
Pubmed
,
Xenbase Lesage,
Cloning provides evidence for a family of inward rectifier and G-protein coupled K+ channels in the brain.
1994,
Pubmed
,
Xenbase Liao,
Heteromultimerization of G-protein-gated inwardly rectifying K+ channel proteins GIRK1 and GIRK2 and their altered expression in weaver brain.
1996,
Pubmed Linder,
Lipid modifications of G protein subunits. Myristoylation of Go alpha increases its affinity for beta gamma.
1991,
Pubmed Luchian,
A C-terminal peptide of the GIRK1 subunit directly blocks the G protein-activated K+ channel (GIRK) expressed in Xenopus oocytes.
1997,
Pubmed
,
Xenbase Nemec,
Gbetagamma binding increases the open time of IKACh: kinetic evidence for multiple Gbetagamma binding sites.
1999,
Pubmed Reuveny,
Contributions of a negatively charged residue in the hydrophobic domain of the IRK1 inwardly rectifying K+ channel to K(+)-selective permeation.
1996,
Pubmed
,
Xenbase Sakmann,
Acetylcholine activation of single muscarinic K+ channels in isolated pacemaker cells of the mammalian heart.
,
Pubmed Schreibmayer,
Inhibition of an inwardly rectifying K+ channel by G-protein alpha-subunits.
1996,
Pubmed
,
Xenbase Silverman,
Subunit stoichiometry of a heteromultimeric G protein-coupled inward-rectifier K+ channel.
1996,
Pubmed
,
Xenbase Slesinger,
Identification of structural elements involved in G protein gating of the GIRK1 potassium channel.
1995,
Pubmed
,
Xenbase Smith,
Mode switching characterizes the activity of large conductance potassium channels recorded from rat cortical fused nerve terminals.
1998,
Pubmed Spauschus,
A G-protein-activated inwardly rectifying K+ channel (GIRK4) from human hippocampus associates with other GIRK channels.
1996,
Pubmed
,
Xenbase Sui,
Na+ activation of the muscarinic K+ channel by a G-protein-independent mechanism.
1996,
Pubmed
,
Xenbase Sui,
Activation of the atrial KACh channel by the betagamma subunits of G proteins or intracellular Na+ ions depends on the presence of phosphatidylinositol phosphates.
1998,
Pubmed
,
Xenbase Vivaudou,
Probing the G-protein regulation of GIRK1 and GIRK4, the two subunits of the KACh channel, using functional homomeric mutants.
1997,
Pubmed
,
Xenbase Vorobiov,
Agonist-independent inactivation and agonist-induced desensitization of the G protein-activated K+ channel (GIRK) in Xenopus oocytes.
1998,
Pubmed
,
Xenbase Wickman,
Recombinant G-protein beta gamma-subunits activate the muscarinic-gated atrial potassium channel.
1994,
Pubmed Wickman,
Ion channel regulation by G proteins.
1995,
Pubmed Yamada,
G protein regulation of potassium ion channels.
1998,
Pubmed Zhou,
Multiple gating modes and the effect of modulating factors on the microI sodium channel.
1991,
Pubmed
,
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