The effects of nucleotides and potassium channel openers on the SUR2A/Kir6.2 complex K+ channel expressed in a mammalian cell line, HEK293T cells

• Published in: Pflügers Archiv 1998-04, Vol.435 (5), p.595-603
• Main Authors: Okuyama, Y, Yamada, M, Kondo, C, Satoh, E, Isomoto, S, Shindo, T, Horio, Y, Kitakaze, M, Hori, M, Kurachi, Y
• Format: Article
• Language: English
• Subjects: Adenosine Triphosphate - metabolism; Adenosine Triphosphate - pharmacology; ATP-Binding Cassette Transporters; Cell Line; Cells; Diazoxide - pharmacology; Guanidines - pharmacology; Humans; Membrane Potentials - drug effects; Niacinamide - analogs & derivatives; Niacinamide - pharmacology; Nicorandil; Patch-Clamp Techniques; Pinacidil; Potassium Channels - biosynthesis; Potassium Channels - drug effects; Potassium Channels, Inwardly Rectifying; Receptors, Drug - biosynthesis; Receptors, Drug - drug effects; Sulfonylurea Receptors; Uridine Diphosphate - pharmacology
• ISSN: 0031-6768; 1432-2013
• DOI: 10.1007/s004240050559

The effects of potassium channel opening drugs and intracellular nucleotides on the ATP-sensitive K+ (KATP) channel composed of SUR2A and Kir6.2 in HEK293T cells were examined using the patch-clamp technique. The SUR2A/Kir6.2 channel was activated effectively by pinacidil, marginally by nicorandil but not by diazoxide. The pinacidil-activated channel currents were inhibited by glibenclamide with a Ki value of 160 nM. Upon formation of inside-out (I-O) patches, spontaneous openings of the channels appeared, which were inhibited by intracellular ATP (ATPi) equipotently in the presence and in the absence of intracellular Mg2+ (Mg2+i). The channel activity ran-down gradually in I-O patches. The run-down channels could be reactivated by ATPi only in the presence of Mg2+i. Uridine 5'-diphosphate (UDP) antagonized the ATPi-mediated inhibition of the channel activity before run-down. After run-down, UDP activated the channel without antagonizing ATPi-mediated channel inhibition. Thus, the SUR2A/Kir6.2 reproduced the major properties of the native cardiac KATP channel well in terms of nucleotide regulation and pharmacology, and therefore can be a useful tool with which to elucidate the molecular mechanisms characterizing the KATP channel.