FIGURE 6.

Arrestin-3 facilitates phosphorylation of purified JNK1α1 and JNK2α2 by MKK4 and MKK7. Representative blots show JNK1α1 (A and D) or JNK2α2 (B and E) phosphorylation in the presence of MKK4 (A and B) or MKK7 (D and E) and increasing amounts of arrestin-3. Quantification of phosphorylation data for JNK1α1 and JNK2α2 in the presence of MKK4 (C) or MKK7 (F) yielded bell-shaped curves as functions of arrestin-3 concentration. Means ± S.D. of three independent experiments are shown. IB, immunoblot. ANOVA analysis with arrestin-3 as the main factor demonstrated significance of arrestin-3 concentration in the presence of MKK4 for both JNK1α1 and JNK2α2 (p < 0.001) and in the presence of MKK7 for both JNK isoforms (p < 0.001). *, −p < 0.001; **, −p < 0.01; *, −p < 0.05 to maximal values (at 5 or 10 μm arrestin-3, respectively) according to Bonferroni/Dunn post-hoc test with correction for multiple comparisons.