FIGURE 3.

Arrestin-3 promotes JNK1/2 activation induced by the expression of ASK1. A, representative Western blot (IB) showing phosphorylation of endogenous JNK1/2 isoforms with or without arrestin-3 in COS-7 cells expressing varying amounts of ASK1. The upper p-JNK blot is the same as the lower blot exposed for a longer time to visualize p54 isoforms. B, quantification of phosphorylation of JNK p46H and p54 isoforms with or without arrestin-3. Analysis of covariance with Arr3 as factor and ASK1 concentration as co-variate showed a significant effect of ASK1 concentration on the level of p46H and p54 phosphorylation (p < 0.0001). Significant Arr3 × ASK1 interaction (p < 0.0001) indicated a difference in slopes due to co-expression of arrestin-3. *, −p < 0.05; **, −p < 0.01 to −Arr3; Student's t test for individual points.