Cloning and functional expression of the cDNA encoding a novel ATP-sensitive potassium channel subunit expressed in pancreatic beta-cells, brain, heart and skeletal muscle.
A cDNA clone encoding an inwardly-rectifying potassium channel subunit (Kir6.2) was isolated from an insulinoma cDNA library. The mRNA is strongly expressed in brain, skeletal muscle, cardiac muscle and in insulinoma cells, weakly expressed in lung and kidney and not detectable in spleen, liver or testis. Heterologous expression of Kir6.2 in HEK293 cells was only observed when the cDNA was cotransfected with that of the sulphonylurea receptor (SUR). Whole-cell Kir6.2/SUR currents were K(+)-selective, time-independent and showed weak inward rectification. They were blocked by external barium (5 mM), tolbutamide (Kd = 4.5 microM) or quinine (20 microM) and by 5 mM intracellular ATP. The single-channel conductance was 73 pS. Single-channel activity was voltage-independent and was blocked by 1 mM intracellular ATP or 0.5 mM tolbutamide. We conclude that the Kir6.2/SUR channel complex comprises the ATP-sensitive K-channel.
University Laboratory of Physiology, Oxford, UK.
H
H
Sakura
C
C
Ammälä
P A
PA
Smith
F M
FM
Gribble
F M
FM
Ashcroft
D018528:ATP-Binding Cassette Transporters; D000255:Adenosine Triphosphate / Q000494:pharmacology; D000595:Amino Acid Sequence; D000818:Animals; D001921:Brain / Q000378:metabolism; D018076:DNA, Complementary / Q000235:genetics; D004553:Electric Conductivity; D004594:Electrophysiology; D015723:Gene Library; D007340:Insulinoma; D007515:Islets of Langerhans / Q000378:metabolism*; D051379:Mice; D008969:Molecular Sequence Data; D018482:Muscle, Skeletal / Q000378:metabolism; D009206:Myocardium / Q000378:metabolism; D026902:Potassium Channel Blockers; D015221:Potassium Channels / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism*; D024661:Potassium Channels, Inwardly Rectifying; D011955:Receptors, Drug / Q000235:genetics / Q000378:metabolism; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D064233:Sulfonylurea Receptors; D014018:Tissue Distribution; D014162:Transfection
D018528:ATP-Binding Cassette Transporters; D018076:DNA, Complementary; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D024661:Potassium Channels, Inwardly Rectifying; D011955:Receptors, Drug; D064233:Sulfonylurea Receptors; D000255:Adenosine Triphosphate