scholarly journals Identification of Critical Residues Controlling G Protein-gated Inwardly Rectifying K+Channel Activity through Interactions with the βγ Subunits of G Proteins

2001 ◽  
Vol 277 (8) ◽  
pp. 6088-6096 ◽  
Author(s):  
Cheng He ◽  
Xixin Yan ◽  
Hailin Zhang ◽  
Tooraj Mirshahi ◽  
Taihao Jin ◽  
...  
Keyword(s):  
G Protein ◽  
G Proteins ◽  
K Channel ◽  
Channel Activity ◽  
Critical Residues ◽  
Inwardly Rectifying

Muscarine-gated K+ channel: subunit stoichiometry and structural domains essential for G protein stimulation

1996 ◽  
Vol 271 (1) ◽  
pp. H379-H385 ◽  
Author(s):  
S. J. Tucker ◽  
M. Pessia ◽  
J. P. Adelman
Keyword(s):  
G Protein ◽  
Xenopus Oocytes ◽  
K Channel ◽  
Channel Activity ◽  
Atrial Myocytes ◽  
Structural Domains ◽  
Maximal Stimulation ◽  
Subunit Stoichiometry ◽  
K Current ◽  
Inwardly Rectifying

Coexpression in Xenopus oocytes of the cloned cardiac inward rectifier subunits Kir 3.1 and Kir 3.4 results in G protein-stimulated channel activity closely resembling the muscarinic channel underlying the inwardly rectifying K+ current in atrial myocytes. To determine the stoichiometry and relative subunit positions within the channel, Kir 3.1 and Kir 3.4 were coexpressed in varying ratios with cloned G beta 1 gamma 2 subunits and also as tandemly linked tetramers with different relative subunit positions. The results reveal that the most efficient channel comprises two subunits of each type in an alternating array within the tetramer. To localize regions important for subunit coassembly and G protein sensitivity, chimeric subunits containing domains from either Kir 3.1, Kir 3.4, or the G protein-insensitive subunit Kir 4.1 were expressed. The results demonstrate that the transmembrane domains dictate the potentiation of the coassembled channels and that, although the NH4- or COOH-termini of both subunits alone can confer G protein sensitivity, both termini are required for maximal stimulation by G beta 1 gamma 2.

scholarly journals A G protein-gated K channel is activated via beta 2-adrenergic receptors and G beta gamma subunits in Xenopus oocytes.

1995 ◽  
Vol 105 (3) ◽  
pp. 421-439 ◽  
Author(s):  
N F Lim ◽  
N Dascal ◽  
C Labarca ◽  
N Davidson ◽  
H A Lester
Keyword(s):  
G Protein ◽  
G Proteins ◽  
Xenopus Oocytes ◽  
K Channel ◽  
Intracellular Camp ◽  
Heterotrimeric G Proteins ◽  
M2 Muscarinic Receptor ◽  
Gamma Subunits ◽  
Beta 2 ◽  
Inwardly Rectifying

In many tissues, inwardly rectifying K channels are coupled to seven-helix receptors via the Gi/Go family of heterotrimeric G proteins. This activation proceeds at least partially via G beta gamma subunits. These experiments test the hypothesis that G beta gamma subunits activate the channel even if released from other classes of heterotrimeric G proteins. The G protein-gated K channel from rat atrium, KGA/GIRK1, was expressed in Xenopus oocytes with various receptors and G proteins. The beta 2-adrenergic receptor (beta 2AR), a Gs-linked receptor, activated large KGA currents when the alpha subunit, G alpha s, was also overexpressed. Although G alpha s augmented the coupling between beta 2AR and KGA, G alpha s also inhibited the basal, agonist-independent activity of KGA. KGA currents stimulated via beta 2AR activated, deactivated, and desensitized more slowly than currents stimulated via Gi/Go-linked receptors. There was partial occlusion between currents stimulated via beta 2AR and the m2 muscarinic receptor (a Gi/Go-linked receptor), indicating some convergence in the mechanism of activation by these two receptors. Although stimulation of beta 2AR also activates adenylyl cyclase and protein kinase A, activation of KGA via beta 2AR is not mediated by this second messenger pathway, because direct elevation of intracellular cAMP levels had no effect on KGA currents. Experiments with other coexpressed G protein alpha and beta gamma subunits showed that (a) a constitutively active G alpha s mutant did not suppress basal KGA currents and was only partially as effective as wild type G alpha s in coupling beta 2AR to KGA, and (b) beta gamma subunits increased basal KGA currents. These results reinforce present concepts that beta gamma subunits activate KGA, and also suggest that beta gamma subunits may provide a link between KGA and receptors not previously known to couple to inward rectifiers.

G Protein Regulation of Inwardly Rectifying K+ Channels

Physiology ◽  
1999 ◽  
Vol 14 (5) ◽  
pp. 215-220 ◽  
Author(s):  
Andreas Karschin
Keyword(s):  
G Protein ◽  
G Proteins ◽  
Tyrosine Kinases ◽  
Cellular Responses ◽  
Signaling Cascades ◽  
Channel Activity ◽  
Protein Subunits ◽  
K Channels ◽  
Kir Channel ◽  
Inwardly Rectifying

Inwardly rectifying K+ (Kir) channels respond to receptor-stimulated signaling cascades that involve G proteins and other cytosolic messengers. Channel activity is controlled both by direct coupling of G protein subunits and by phosphorylation via protein serine/threonine and tyrosine kinases. The coincidence of both forms of Kir channel signaling may give rise to complex cellular responses.

Effects of ginsenoside on G protein-coupled inwardly rectifying K+ channel activity expressed in Xenopus oocytes

2003 ◽  
Vol 468 (2) ◽  
pp. 83-92 ◽  
Author(s):  
Seok Choi ◽  
Jun-Ho Lee ◽  
Yang In Kim ◽  
Man-Jong Kang ◽  
Hyewon Rhim ◽  
...  
Keyword(s):  
G Protein ◽  
Xenopus Oocytes ◽  
K Channel ◽  
Channel Activity ◽  
Inwardly Rectifying ◽  
G Protein Coupled

scholarly journals Familial Sinus Node Disease Caused by a Gain of GIRK (G-Protein Activated Inwardly Rectifying K + Channel) Channel Function

2019 ◽  
Vol 12 (1) ◽  
Author(s):  
Johanna Kuß ◽  
Birgit Stallmeyer ◽  
Matthias Goldstein ◽  
Susanne Rinné ◽  
Christiane Pees ◽  
...  
Keyword(s):  
G Protein ◽  
Sinus Node ◽  
K Channel ◽  
Channel Function ◽  
Node Disease ◽  
Sinus Node Disease ◽  
Inwardly Rectifying

Different properties of the atrial G protein-gated K+ channels activated by extracellular ATP and adenosine

1995 ◽  
Vol 269 (4) ◽  
pp. H1349-H1358 ◽  
Author(s):  
C. Fu ◽  
A. Pleumsamran ◽  
U. Oh ◽  
D. Kim
Keyword(s):  
G Protein ◽  
Single Channel ◽  
Extracellular Atp ◽  
K Channel ◽  
Affinity Constant ◽  
Channel Activity ◽  
K Channels ◽  
Atrial Cells ◽  
K Current ◽  
Inside Out

Extracellular ATP (ATPo) and adenosine activate G protein-gated inwardly rectifying K+ currents in atrial cells. Earlier studies have suggested that the two agonists may use separate pathways to activate the K+ current. Therefore, we examined whether the K+ channels activated by the two agonists have different properties under identical ionic conditions. In cell-attached patches, K+ channels activated by 100 microM ATP in the pipette had a single-channel conductance and mean open time of 32.0 +/- 0.2 pS and 0.5 +/- 0.1 ms, respectively, compared with 31.3 +/- 0.3 pS and 0.9 +/- 0.1 ms for the K+ channels activated by adenosine (140 mM KCl). With ATPo as the agonist, the K+ channel activity in cell-attached patches was approximately threefold lower than that in inside-out patches with 100 microM GTP in the bath. Applying ATP to the cytoplasmic side of the membrane (ATPi) produced a biphasic concentration-dependent effect on channel activity: an increase at low [mean affinity constant (K0.5) = 190 microM] and a decrease at high (K0.5 = 1.3 mM) concentrations. In contrast, with adenosine as the agonist, K+ channel activity in cell-attached patches was approximately fourfold greater than that in inside-out patches with 100 microM GTP in the bath. In inside-out patches, ATPi only augmented the K+ channel activity (K0.5 = 32 microM). These results show that although both ATPo and adenosine activate kinetically similar K+ channels in atrial cells, the channels are regulated differently by intracellular nucleotides.

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