Evidence for an Increase in the Association of Cytosolic Phospholipase A2 with the Cytoskeltion of Stimulated Rabbit Platelets

Following stimulation of rabbit platelets with thrombin, phospholipase A2 (PLA2) activity increased in the Triton X-100-insoluble residue. Although the PLA2 activity was dependent on the protein content of the residue from the stimulated cells, the specific activity was higher than that in the case of unstimulated cells. The enzyme activity was inhibited by p-bromophenacyl bromide and increased significantly with 0.5-10 microM Ca2+. The enzyme hydrolyzed phospholipids having an arachidonoyl residue more effectively than ones with a linoleoyl residue. In addition, 70% of the enzyme activity was immunoprecipitated with a monoclonal antibody against cytosolic PLA2 of rabbit platelets, while it was inhibited by only 20% by an antibody that neutralizes the activity of group II PLA2. These results suggest an increase in the association of cytosolic PLA2 with cytoskeleton upon stimulation of rabbit platelets.