[Regulation of inositol-1,4,5-triphosphate receptor by G(i)-protein]

The pertussis toxin (PT) inhibits thrombin-induced mobilising of Ca2+ but does not affect formation of inositol-1, 4, 5-triphosphate (IPh3). The latter being related to Gi and G0, the possibility of a direct effect of these proteins on the IPh3-induced release of Ca2+ from sarcoplasmic reticulum, was studied. The data obtained suggest existence of an association of the Gi3 protein with the IPh3-P on the sarcoplasmic reticulum membrane, as well as a direct modulation by the Gi protein of the Ca2+ release from intracellular stores.