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

Among G-proteins, Gh 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, GTPgammaS, was applied, the channel activity was increased about 2.5-fold. Addition of GDPbetaS resulted in reversal of the GTPgammaS effect. When the Galphah7 antibody was applied, the GTPgammaS-stimulated channel activity was significantly inhibited to control level, suggesting that Galphah is involved in activation of the Maxi-K+ channel in smooth muscle cells.