Functional Characterization of a Small Conductance GIRK Channel in Rat Atrial Cells

ECU Author/Contributor (non-ECU co-authors, if there are any, appear on document)
Tatyana T. Ivanova-Nikolova (Creator)
Emil N. Nikolov (Creator)
East Carolina University (ECU )
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Abstract: Muscarinic K1 (KACh) channels are key determinants of the inhibitory synaptic transmission in the heart. These channels are heterotetramers consisting of two homologous subunits G-protein-gated inwardly rectifying K1 (GIRK)1 and GIRK4 and have unitary conductance of ;35 pS with symmetrical 150 mM KCl solutions. Activation of atrial KACh channels however is often accompanied by the appearance of openings with a lower conductance suggesting a functional heterogeneity of G-protein-sensitive ion channels in the heart. Here we report the characterization of a small conductance GIRK (scGIRK) channel present in rat atria. This channel is directly activated by Gbg subunits and has a unitary conductance of 16 pS. The cGIRK and KACh channels display similar affinities for Gbg binding and are frequently found in the same membrane patches. Furthermore Gbg-activated scGIRK channels—like their KACh counterparts—exhibit complex gating behavior fluctuating among four functional modes conferred by the apparent binding of a different number of Gbg subunits to the channel. The electrogenic efficacy of the scGIRK channels however is negligible compared to that of KACh channels. Thus Gbg subunits employ the same signaling strategy to regulate two ion channels that are apparently endowed with very different functions in the atrial membrane. Originally published Biophysical Journal Vol. 87 No. 5 Nov 2004

Additional Information

Biophysical Journal. 87:5(November 2004) p. 3122-3136.
Language: English
Date: 2011
rat atria, GIRK channel, G-protein-sensitive

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