Modulation of ATP sensitive potassium channels by the G-protein βγ complex

• Published in: Japanese Journal of Pharmacology Vol. 79; no. suppl.1; p. 144
• Main Authors: Wada, Yoshiyuki, Yamashita, Toshikazu, Kokubun, Shinichiro, Asano, Tomiko, Miura, Reiko, Nukada, Toshihide
• Format: Journal Article
• Language: English
• Published: The Japanese Pharmacological Society 1999
• ISSN: 0021-5198; 1347-3506
• DOI: 10.1016/S0021-5198(19)34590-1

Modulation of the ATP sensitive potassium channels reconstituted with Kir6.2 and SUR2A by G-protein βγ2 complex (Gβγ2) was investigated using the inside-out patch-clamp technique. Intracellular application of Gβγ2 concentration-dependently increased the open-state probability (NPo) in the presence of ATP. NPo observed with 0.1 mM ATP was 2.1, 3.1 and 4.0-fold of the control after addition of 5, 50 and 500 pM Gβγ2, respectively. When relationships between NPo and ATP concentration were examined, half-maximal inhibition of the channel was achieved by ATP of 16.1 and 41.2 μM in the absence and the presence of 50 pM Gβγ2, respectively, while the Hill coefficient remained unchanged (approximately 1.4). In a binding assay, Gβγ2 bound to both of the GST fusion proteins containing the first or the second nucleotide-binding domain of SUR2A, but not to one containing the C-terminal segment of Kir6.2. Furthermore, Gβγ2 did not increase NPo of the C-terminal deletion mutant of Kir6.2 which expresses functional channels without SUR subunits. These findings suggest that Gβγ2 antagonize the inhibitory action of ATP in the reconstituted channel with Kir6.2 and SUR2A through a direct interaction with the SUR subunit.