Expression of an atrial G-protein-activated potassium channel in Xenopus oocytes

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Abstract

Injection of rat atrial RNA into Xenopus oocytes resulted in the expression of a guanine nucleotide binding (G) protein-activated K+ channel. Current through the channel could be activated by acetylcholine or, if RNA encoding a neuronal 5HT1A receptor was coinjected with atrial RNA, by serotonin (5HT). A 5HT-evoked current (1(5HT)) was observed in oocytes injected with ventricle RNA fractions (of 2.5-5.5 kb) and 5HT1A receptor RNA. 1(5HT) displayed strong inward rectification with very little conductance above the K+ equilibrium potential, was highly selective for K+ over Na+, and was blocked by 5-300 μM Ba2+. 1(5HT) was suppressed by intracellular injection of the nonhydrolyzable analog of GDP, guanosine 5'-[β- thio]diphosphate, but not by treatment with pertussis toxin (PTX), suggesting coupling of the receptor to the G-protein-activated K+ channel via a PTX- insensitive G protein, possibly endogenously present in the oocyte. Coexpression of the α subunit of a PTX-sensitive G protein, G(i2), rendered 1(5HT) sensitive to PTX inhibition. Native oocytes displayed a constitutively active inwardly rectifying K+ current with a lower sensitivity to Ba2+ block; expression of a similar current was also directed by atrial or ventricle RNA of 1.5-3 kb. Xenopus oocytes may be employed for cloning of the G-protein-activated K+ channel cDNA and for studying the coupling between this channel and G proteins.

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Dascal, N., Lim, N. F., Schreibmayer, W., Wang, W., Davidson, N., & Lester, H. A. (1993). Expression of an atrial G-protein-activated potassium channel in Xenopus oocytes. Proceedings of the National Academy of Sciences of the United States of America, 90(14), 6596–6600. https://doi.org/10.1073/pnas.90.14.6596

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