FIGURE 4.

sPLA2-IIA-induced proliferation of U937 human monocytic lymphoma cells in an-integrin-dependent manner. a, effect of sPLA2-IIA mutants on cell proliferation. U937 cells (αvβ3+, α4β1+) were plated in wells of 96-well plates (10,000 cells/well), and serum-starved for 48 h. After treatment with Wt or mutant sPLA2-IIA for 48 h, we measured cell proliferation by MTS assays. p < 0.0001 between Wt and R74E/R100E by 2-way analysis of variance. b, Wt and catalytically inactive H47Q mutant of sPLA2-IIA induced ERK1/2, but integrin binding-defective R74E/R100E mutant did not. U937 cells were serum-starved for 24 h, and stimulated with Wt and mutant sPLA2-IIA (0.5 μg/ml) for 10 min at 37 °C. Cell lysates were analyzed by Western blotting with anti-phospho ERK1/2 or anti-ERK1/2 antibodies. The blot is representative of three independent experiments.