Phosphorylation of cytosolic group IV phospholipase A2 is necessary but not sufficient for arachidonic acid release in P388D1 macrophages

Activation of the cytosolic Group IV phospholipase A(2) (cPLA(2)) by agonists has been correlated with the direct phosphorylation of the enzyme by members of the mitogen-activated protein kinase (R24PK) cascade. Phosphorylation of the cPLA(2) increases the specific activity of the enzyme, thereby stimulating the arachidonic acid release. We show here, however, that conditions that lead to full phosphorylation of the cPLA(2) do not lead to enhanced AA release. As the above observations were made under both Ca2+-dependent and Ca2+-independent conditions, they emphasize that the current paradigm for activation of the cPLA(2) in cells involving both phosphorylation and Ca2+ is incomplete and that other factors should be taken into account. (C) 2000 Academic Press.