Intracellular nucleotide-mediated gating of SUR/Kir6.0 complex potassium channels expressed in a mammalian cell line and its modification by pinacidil

• Published in: The Journal of physiology 1998-09, Vol.511 (3), p.663-674
• Main Authors: Satoh, Eisaku, Yamada, Mitsuhiko, Kondo, Chikako, Repunte, Vez P., Horio, Yoshiyuki, Iijima, Toshihiko, Kurachi, Yoshihisa
• Format: Article
• Language: English
• Subjects: Adenosine Diphosphate - pharmacology; Adenosine Triphosphate - pharmacology; Animals; Cell Line; Electrophysiology; Humans; Ion Channel Gating - drug effects; Kidney - chemistry; Kidney - cytology; Kinetics; Mammals; Mixed Function Oxygenases - physiology; Original; Pinacidil - pharmacology; Potassium Channels - physiology; Potassium Channels, Inwardly Rectifying; Uridine Diphosphate - pharmacology; Uridine Triphosphate - pharmacology; Vasodilator Agents - pharmacology
• ISSN: 0022-3751; 1469-7793
• DOI: 10.1111/j.1469-7793.1998.663bg.x

We have examined the properties of intracellular nucleotide-mediated gating of K + channel constructs composed of the sulphonylurea receptor 2B and the inwardly rectifying K + channel subunits Kir6.1 and Kir6.2 (SUR2B/Kir6.1 and SUR2B/Kir6.2 complex K + channels) heterologously expressed in human embryonic kidney (HEK) 293T cells. In the cell-attached form, both types of K + channel were activated by pinacidil. In inside-out (IO) patches, the SUR2B/Kir6.2 channels opened spontaneously and were inhibited by intracellular ATP (ATP i ). Pinacidil attenuated the ATP i -mediated channel inhibition in a concentration-dependent manner. In contrast, the SUR2B/Kir6.1 channels required intracellular nucleoside di- or tri-, but not mono-, phosphates for opening. The potency of adenine, guanine or uracil nucleotides to activate SUR2B/Kir6.1 channels was enhanced by pinacidil. In the presence of pinacidil, adenine and guanine, but not uracil, nucleotides exhibited bell-shaped concentration-dependent activating effects on SUR2B/Kir6.1 channels. This was due to channel inhibition caused by adenine and guanine nucleotides, which was unaffected by pinacidil. From power density spectrum analysis of SUR2B/Kir6.1 currents, channel activation could be described by the product of two gates, a nucleotide-independent fast channel gate and a nucleotide-dependent slow gate, which controlled the number of functional channels. Pinacidil specifically increased the potency of nucleotide action on the slow gate. We conclude that Kir6.0 subunits play a crucial role in the nucleotide-mediated gating of SUR/Kir6.0 complex K + channels and may determine the molecular mode of pinacidil action.