Figure 3.

Activation loop phosphorylation is important for the invasion-promoting ability of ERK3 in lung cancer cells. A, Transwell Matrigel invasion assay of A549 cells stably expressing an empty vector, WT, or mutant myc-ERK3 as described in Fig. 1C. B, Transwell Matrigel invasion assay of H1299 cells with transient overexpression of an empty vector or WT or mutant HA-ERK3 as described in Fig. 1E. Quantitated invasion ability is presented as the number of invaded cells per field. Values in the bar graphs represent mean ± S.E. (n ≥ 6 fields). **, p < 0.0001 (significantly different compared with empty vector); *, p < 0.05 (significantly different compared with empty vector); #, p < 0.05 (significantly different compared with ERK3); one-way ANOVA. Representative images of invaded cells stained with crystal violet are shown below the bar graphs. Scale bars, 100 μm.