The cardiac inward rectifier K+ channel subunit, CIR, does not comprise the ATP-sensitive K+ channel, IKATP.
Cardiac IKACh is comprised of two inwardly rectifying K+ channel subunits, CIR and GIRK1 (Krapivinsky, G., Gordon, E. G., Wickman, K., Velimirovic, B., Krapivinsky, L., and Clapham, D. E. (1995) Nature 374, 135-141). A cardiac protein virtually identical to CIR, termed rcKATP-1 (Ashford, M. L. J., Bond, C. T., Blair, T. A., and Adelman, J. P. (1994) Nature 370, 456-459), was reported to form an ATP-sensitive inwardly rectifying K+ channel, IKATP. We attempted to determine whether CIR alone or together with an unknown protein(s) participated in the formation of cardiac IKATP. Expression of CIR in insect, oocyte, and mammalian cell systems did not increase the appearance of ATP-sensitive currents, but rather gave rise to unique strongly inwardly rectifying, G protein-regulated K+ currents. CIR protein is found exclusively in atria, in contrast to the predominance of IKATP functional activity in ventricle. Also, CIR was completely depleted from heart membrane after immunodepletion of GIRK1. We conclude that CIR/rcKATP-1 is not a subunit of cardiac IKATP and that GIRK1 is the only channel protein coassociating with CIR in heart.
D018528:ATP-Binding Cassette Transporters; D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D016367:Baculoviridae / Q000235:genetics; D016466:CHO Cells; D002417:Cattle; D002460:Cell Line; D006224:Cricetinae; D051676:G Protein-Coupled Inwardly-Rectifying Potassium Channels; D006325:Heart Atria / Q000378:metabolism*; D006352:Heart Ventricles / Q000378:metabolism*; D006801:Humans; D054086:KATP Channels; D015221:Potassium Channels / Q000235:genetics / Q000378:metabolism*; D024661:Potassium Channels, Inwardly Rectifying; D018411:Spodoptera
D018528:ATP-Binding Cassette Transporters; D051676:G Protein-Coupled Inwardly-Rectifying Potassium Channels; D054086:KATP Channels; C484274:KCNJ5 protein, human; D015221:Potassium Channels; D024661:Potassium Channels, Inwardly Rectifying; C092520:uK-ATP-1 potassium channel; D000255:Adenosine Triphosphate