Reduced Phospholipase A₂ Activity Is Not Accompanied by Reduced Arachidonic Acid Release

Arachidonic acid release in cells highly over expressing cytosolic phospholipase A₂ has been attributed to mitogen-activated protein kinase phosphorylation of cytosolic phospholipase A₂ on serine-505. To investigate the role of cytosolic phospholipase A₂ in cellular physiology, we attempted to inhibit cytosolic phospholipase A₂ in the intact cell employing an antisense RNA strategy. Swiss 3T3 cells were stably transfected with an antisense cytosolic phospholipase A₂ expression vector. A clone of cells with reduced immunodetectable cytosolic phospholipase A₂, compared to a vector transfected cell line, was identified by Western blotting and a corresponding decrease in phospholipase A₂ activity was confirmed by enzymatic assay in cell free extracts. However, arachidonic acid release from intact cells in response to agonists was not different between antisense and control cell lines. Thus, arachidonic acid release in intact cells with decreased cytosolic phospholipase A₂ activity is likely to be modulated by rate limiting factors that are extrinsic to cytosolic phospholipase A₂.