Regulation of phospholipase D in astroglial cells by calcium-activated protein kinase C

To assess the contribution of phospholipase D to agonist-evoked arachidonic acid mobilization in central nervous system astroglial cells, enzyme activity was determined by formation of phosphatidylethanol. Phosphatidylethanol was formed upon stimulation of the cells with phorbol esters and also ionomycin and thapsigargin, agents which increase intracellular [Ca(2+)]. However, various receptor agonists did not activate phospholipase D. Phospholipase D activation by phorbol esters and elevators of intracellular [Ca(2+)] was abolished when cells were first depleted of protein kinase C, but direct activation of phospholipase D by stearylamine was unaffected. These results suggest that the actions of ionophore and thapsigargin on phospholipase D may be mediated by a Ca(2+)-activated protein kinase C subtype in astroglial cells.