Erk-dependent cytosolic phospholipase A(2) activity is induced by CD95 ligand cross-linking in the mouse derived Sertoli cell line TM4 and is required to trigger apoptosis in CD95 bearing cells

In the present study we demonstrated that CD95L crosslinking generated reve rse signalling in the mouse derived Sertoli cell line TM4, Treatment of TM4 cells with mAb anti-CD95L induced activation of the cytosolic phospholipas e A(2) (cPLA(2)), Cytosolic PLA, activation was controlled by the MAPK path way as indicated by the ability of the specific MEK inhibitor, PD098059, to abolish cPLA2 activation, In addition, Western blot experiments showed a r apid increase in phosphorylated Erk1/2 following CD95L cross-linking, while no effect on the phosphorylation of other MAPK, p38 or JNK, was observed, CD95L cross-linking by mAb increased the levels of soluble CD95L and apopto tic activity of TM4 cell supernatants, which was blacked by co-incubation w ith the PLA, inhibitor, AACOCF3 or PD098059, Finally, pre-treatment of TM4 cells with AACOCF(3) or PD098059 completely abolished TM4-induced apoptosis of Jurkat T cells, thus indicating that the Erk/cPLA(2) pathway is require d for CD95L-induced apoptosis.