Modulation of large conductance Ca2+-activated K+ channel by Gαh (transglutaminase II) in the vascular smooth muscle cell

 Among G-proteins, G_h is unique in structural differences in the GTP-binding domain and possessing transglutaminase activity. We have studied the role of G protein in modulation of large conductance Ca²⁺-activated K⁺ (Maxi-K⁺) channel by the inside-out mode of patch clamp in smooth muscle cells from superior mesenteric artery of the rabbit. When the non-hydrolyzable GTP analogue, GTPγS, was applied, the channel activity was increased about 2.5-fold. Addition of GDPβS resulted in reversal of the GTPγS effect. When the Gα_h7 antibody was applied, the GTPγS-stimulated channel activity was significantly inhibited to control level, suggesting that Gα_h is involved in activation of the Maxi-K⁺ channel in smooth muscle cells. Received: 23 September 1996 / Received after revision: 26 November 1996 / Accepted: 3 December 1996