TWEAK induces TRAF3IP2-dependent p38 MAPK, NF-κB, and AP-1 activation in cardiac fibroblasts. TWEAK (10 ng/ml) induced time-dependent p38 MAPK activation (Thr180/Tyr182 phosphorylation) in CF (A), an effect inhibited by TRAF3IP2 knockdown (lentiviral shRNA, moi0.5 for 48 h, shown on the right) or pretreatment with the p38 MAPK-specific inhibitor SB239063 (10 μM in DMSO for 1 h; B). Similarly, TWEAK induced NF-κB activation (Ser536 phosphorylation of p65) in a time-dependent manner, an effect also inhibited by TRAF3IP2 knockdown or pre-treatment with SB239063 (D). Further, TWEAK induced time-dependent JNK (Thr183/Tyr185 phosphorylation) and AP-1 activation (Ser63 phosphorylation of c-Jun) in CF (E), an effect blunted by TRAF3IP2 knockdown (F). A-E: A representative image from three independent immunoblotting experiments with similar results is shown at the top and summarized semi-quantification of intensity of immunoreactive bands by densitometry from all three experiments in the respective bottom panels. *P < 0.05 versus Untreated, †P < 0.05 versus TWEAK, §P < 0.05 versus Untreated.