PHOSPHATIDIC-ACID ACTIVATION OF PROTEIN-KINASE-C IN LA-N-1 NEUROBLASTOMA-CELLS

Phosphatidic acid (PA), a hydrolytic product of phospholipase D activi ty, stimulated cytosolic protein kinase C (PKC) activity when LA-N-1 n euroblastoma cells in culture were treated with PA, without translocat ing the enzyme to the membrane. Treatment of cells with 12-O-tetradeca noylphorbol-13-acetate (TPA) translocated and activated PKC in a dogma tic manner. Partially purified PKC activity derived from LA-N-1 neurob lastoma cells was stimulated by PA alone or in the presence of phospha tidylserine or TPA, without affecting [H-3]phorbol dibutyrate binding, indicating that the site of action of PA was different from the phorb ol ester or diacylglycerol binding site. These results suggest an unor thodox pattern of PKC stimulation mediated by PA which appears to be y et another mode of PA signal transduction.