Phospholipase C, protein kinase C, Ca2+/calmodulin-dependent protein kinase II, and redox state are involved in epigallocatechin gallate-induced phospholipase D activation in human astroglioma cells

Abstract

We show that epigallocatechin-3 gallate (EGCG), a major component of green tea, stimulates phospholipase D (PLD) activity in U87 human astroglioma cells. EGCG-induced PLD activation was abolished by the phospholipase C (PLC) inhibitor and a lipase inactive PLC-c1mutant,which is dependent on intracellular or extracellular Ca2+, with the possible involvement of Ca2+/calmodulin-dependent protein kinase II (CaM kinase II). EGCGinduced translocation of PLC-c1 from the cytosol to the membrane and PLC-c1 interactionwith PLD1.EGCGregulates the activity of PLD by modulating the redox state of the cells, and antioxidants reverse this effect. Moreover, EGCG-induced PLD activation was reduced by PKC inhibitors or down-regulation of PKC. Taken together, these results show that, in human astroglioma cells, EGCG regulates PLD activity via a signaling pathway involving changes in the redox state that stimulates a PLC-c1 [Ins(1,4,5)P3-Ca2+]–CaM kinase II–PLDpathway and a PLC-c1 (diacylglycerol)–PKC–PLD pathway. Keywords: Ca2+/calmodulin-dependent protein kinase II; epigallocatechin-3 gallate; phospholipase C-c1; phospholipase D; reactive oxygen species.