Channelpedia

Kir3.4

Description: potassium inwardly-rectifying channel, subfamily J, member 5
Gene: Kcnj5     Synonyms: Kir3.4, Girk4, kcnj5

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Introduction


Experimental data


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Gene

RGD ID Chromosome Position Species
61971 8 32082866-32104412 Rat
62264 9 32122368-32151822 Mouse
1349904 11 128761313-128787964 Human

Kcnj5 : potassium inwardly-rectifying channel, subfamily J, member 5


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Transcript

Acc No Sequence Length Source
NM_017297 n/A n/A NCBI
NM_010605 n/A n/A NCBI
NM_000890 n/A n/A NCBI

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Ontology

Accession Name Definition Evidence
GO:0016020 membrane Double layer of lipid molecules that encloses all cells, and, in eukaryotes, many organelles; may be a single or double lipid bilayer; also includes associated proteins. IEA
GO:0009897 external side of plasma membrane The side of the plasma membrane that is opposite to the side that faces the cytoplasm. IDA
GO:0016021 integral to membrane Penetrating at least one phospholipid bilayer of a membrane. May also refer to the state of being buried in the bilayer with no exposure outside the bilayer. When used to describe a protein, indicates that all or part of the peptide sequence is embedded in the membrane. IEA
GO:0030315 T-tubule Invagination of the plasma membrane of a muscle cell that extends inward from the cell surface around each myofibril. The ends of T-tubules make contact with the sarcoplasmic reticulum membrane. IDA

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Interaction

Co-expression of Kir2.1 with Kir3.4 in Xenopus oocytes and HEK293T cells did not yield currents with distinguishable features. However, co-expression of a dominant-negative Kir2.1 with the wild-type Kir3.4 decreased the Kir3.4 current amplitude in Xenopus oocytes. The results indicate that Kir2.1 is capable of forming heteromultimeric channels with Kir3.4. (Ishihara [996])

Stimulation of the M2 receptor by ACh causes dissociation of the coupled G-protein and the Gbc-subunits activate the Kir3.1/3.4 channel by direct binding (Logothetis [1002]).

phosphatidylinositol (4,5)-bisphosphate (PIP2) is a requirement for Kir channels activity and a decrease in bound PIP2 strongly decreases the open probability of the Kir3.1/ 3.4 channels (Huang [1003], Sui [1004]).

GIRK1/4 channel current can be blocked by BaCl(2) and enhanced by increasing the driving force for K(+) across the cell membrane. (Walsh [995])


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Protein


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Structure


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Distribution


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Expression

Kir3.1 is expressed in the heart and brain (Kubo [1000]), and is known to assemble with Kir3.4 in SAN and atrial myocytes in the heart and with Kir3.2 in the brain to form functional channels (Krapivinsky [998], Velimirovic [999]).


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Functional

Kir3.1 and Kir3.4, expressed mainly in SAN and atrial myocytes in the heart, form heterotetrameric channels, which are coupled to m2 muscarinic receptor via G-protein bc subunits and carry the ACh-activated K+ current (IK,ACh) regulating the heart rate (Krapivinsky [998], Corey [1001]).

Mice deficient of Kir3.1 or 3.4 exhibit mild resting tachycardia (Bettahi [1005]) and impaired beat-to-beat control (Wickman [1006]).

Kir3.4 deficient mice were resistant to atrial fibrillation caused by vagal stimulation (Kovoor [1007]). Kir3.4 could be predisposing to or even protecting against atrial fibrillation (Calloe [997]).


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Kinetics


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Model


References

197

Saitoh O. et al. RGS7 and RGS8 differentially accelerate G protein-mediated modulation of K+ currents.
J. Biol. Chem., 1999 Apr 2 , 274 (9899-904).

199

Mark MD. et al. G-protein mediated gating of inward-rectifier K+ channels.
Eur. J. Biochem., 2000 Oct , 267 (5830-6).

995

Walsh KB. et al. A real-time screening assay for GIRK1/4 channel blockers.
J Biomol Screen, 2010 Dec , 15 (1229-37).

996

Kubo Y. et al. Heteromeric assembly of inward rectifier channel subunit Kir2.1 with Kir3.1 and with Kir3.4.
Biochem. Biophys. Res. Commun., 2009 Mar 20 , 380 (832-7).

997

Schmitt N. et al. Characterizations of a loss-of-function mutation in the Kir3.4 channel subunit.
Biochem. Biophys. Res. Commun., 2007 Dec 28 , 364 (889-95).

Clapham DE. et al. Number and stoichiometry of subunits in the native atrial G-protein-gated K+ channel, IKACh.
J. Biol. Chem., 1998 Feb 27 , 273 (5271-8).

Logothetis DE. et al. Na+ activation of the muscarinic K+ channel by a G-protein-independent mechanism.
J. Gen. Physiol., 1996 Nov , 108 (381-91).

Marker CL. et al. Contribution of the Kir3.1 subunit to the muscarinic-gated atrial potassium channel IKACh.
J. Biol. Chem., 2002 Dec 13 , 277 (48282-8).

Clapham DE. et al. Abnormal heart rate regulation in GIRK4 knockout mice.
Neuron, 1998 Jan , 20 (103-14).

Clapham DE. et al. Evaluation of the role of I(KACh) in atrial fibrillation using a mouse knockout model.
J. Am. Coll. Cardiol., 2001 Jun 15 , 37 (2136-43).


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Credits