Figure 2. Signaling activity of IHCA gp130 mutants is attenuated by SOCS3. (A and B) Plasmids engineered to express either inflammatory hepatocellular adenoma (IHCA)-associated gp130 mutants (black bars) or wild-type (WT) gp130 were transfected into Hep3B cells (n = 3) together with a STAT3-driven luciferase (Luc) reporter construct (pSIEM-Luc). STAT3 activation was measured by luciferase activity 6 h after serum starvation. Shown are the means ± SD luciferase activity. (A) STAT3 activity following the co-transfection of Hep3B cells with the STAT3-luciferase reporter and a control empty plasmid (EP) or constructs coding withWT gp130, Y186 gp130 mutant, Y759F gp130 mutant, or Y186/Y759F gp130 double mutant. (B) Hep3B cells were co-transfected with the STAT3-luciferase reporter and a vector expressing the Y186 gp130 mutant or the corresponding EP along with a SOCS3 expression construct (+) or the corresponding EP (−). Data shown are the mean luciferase activities ± SD relative to pSIEM-Luc alone (EP control) following serum starvation (6 h). Where indicated, cells were treated for the final 3 h with 100 ng/mL interleukin-6 (IL-6). Statistical significance was determined by 2-tailed Student t test; ***P < 0.001.