The inositol (1,4,5)-trisphosphate 3-kinase of Xenopus oocyte is activatedby CaMKII and involved in the regulation of InsP(3)-mediated Ca2+ release

The effect of Ca2+ on inositol (1,4,5)-trisphosphate 3-kinase (3-kinase) ac tivity was measured on Xenopus oocyte cytosolic extracts. The Ca2+-evoked e levation in 3-kinase activity appeared to he mediated by calmodulin (CaM) a nd the calmodulin-dependent protein kinase II (CaMKII). The results observe d in vitro were totally retrieved in intact oocytes and tend to demonstrate the involvement of a CaMKII-mediated phosphorylation in the regulation of 3-kinase activity. Finally, electrophysiological recordings of InsP(3)-elic ited chloride current transients in the presence of CaM/CaMKII inhibitors a llowed to postulate an involvement of 3-kinase activity in the regulation o f InsP(3)-mediated Ca2+ release. (C) 1999 Federation of European Biochemica l Societies.