Expression of an atrial G-protein-activated potassium channel in Xenopus oocytes.
Injection of rat atrial RNA into Xenopus oocytes resulted in the expression of 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 (I5HT) was observed in oocytes injected with ventricle RNA fractions (of 2.5-5.5 kb) and 5HT1A receptor RNA. I5HT 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 microM Ba2+. I5HT was suppressed by intracellular injection of the nonhydrolyzable analog of GDP, guanosine 5'-[beta-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 alpha subunit of a PTX-sensitive G protein, G(i2), rendered I5HT 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.
Dascal
N
N
Division of Biology, California Institute of Technology, Pasadena 91125.
Lim
N F
NF
Schreibmayer
W
W
Wang
W
W
Davidson
N
N
Lester
H A
HA
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D001464:Barium / Q000494:pharmacology; D003217:Conductometry; D004305:Dose-Response Relationship, Drug; D005260:Female; D019204:GTP-Binding Proteins / Q000378:metabolism*; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000031:analogs & derivatives / Q000494:pharmacology; D006325:Heart Atria / Q000737:chemistry*; D008297:Male; D009865:Oocytes; D037342:Pertussis Toxin; D011188:Potassium / Q000378:metabolism*; D015221:Potassium Channels / Q000187:drug effects / Q000502:physiology*; D014176:Protein Biosynthesis; D051381:Rats; D012701:Serotonin / Q000494:pharmacology; D010566:Virulence Factors, Bordetella / Q000494:pharmacology; D014982:Xenopus laevis
D015221:Potassium Channels; D010566:Virulence Factors, Bordetella; C034883:guanosine 5'-O-(2-thiotriphosphate); D001464:Barium; D012701:Serotonin; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D037342:Pertussis Toxin; D019204:GTP-Binding Proteins; D000109:Acetylcholine; D011188:Potassium