FIGURE 9.

Mutations in putative ERK phosphorylation sites do not affect iPLA₂γ activity. COS-1 cells were transiently transfected with M1-GFP-iPLA₂γ WT, the S168A and S271A mutants, or the S168A/S271A double mutant together with COX1. A, after 24 h, cells were untreated or were incubated with EGF (100 ng/ml) + ionomycin (Iono, 1.5 μm) for 40 min. PGE₂ release was stimulated significantly by EGF + ionomycin in the cells expressing M1 GFP-iPLA₂γ WT and all mutants. *, p < 0.05; **, p < 0.01 versus corresponding untreated groups, seven experiments. In these experiments basal PGE₂ release (vector + COX1-transfected, untreated cells) was 827 pg/ml. B, cell lysates were immunoblotted with antibodies to GFP or tubulin. The blot shows comparable levels of expression.