Cytokine-mediated cPLA(2) phosphorylation is regulated by multiple MAPK family members

Cytosolic phospholipase A(2) (cPLA(2)) plays a critical role in various neu trophil functions including the generation of leukotrienes and platelet-act ivating factor release. Enzyme activity is regulated both by translocation to the membrane in a Ca2+-dependent manner and serine phosphorylation by me mbers of the mitogen-activated protein kinase (MAPK) family. In this report , we have investigated the role of granulocyte/macrophage colony-stimulatin g factor (GM-CSF)mediated signalling pathways in the regulation of cPLA(2), GM-CSF-induced cPLA(2) phosphorylation was not affected by pharmacological inhibition of p38 MAPK, phosphatidylinositol 3-kinase or Src, However, inh ibition of extracellular signal-regulated kinase (ERK) MAPK activation resu lted in a partial inhibition of cPLA(2) phosphorylation, revealed in a slow er onset of phosphorylation. A cell line stably transfected with the GM-CS F receptor was used to further analyze GM-CSF-mediated cPLA(2) phosphorylat ion. Mutation of tyrosine residues 577 and 612 resulted in a delayed cPLA(2 ) phosphorylation similar to the pharmacological ERK inhibition. Furthermor e, inhibition of p38 MAPK in cells bearing the double mutant beta c577/612 completely abrogated GM-CSF-induced cPLA(2) phosphorylation. We conclude th at GM-CSF can mediate cPLA(2) phosphorylation through the redundant activat ion of both p38 and ERK MAP kinases. (C) 2000 Federation of European Bioche mical Societies.