Representative western blot analysis of IRS1, p-P70S6K (T389), P70S6K, p-AKT (T308), AKT, p-cJUN (s73) and cJUN in RCS chondrocytes treated with vehicle (5% ABS) and FGF18 (50 ng/mL) for 12h. JNK inhibitor (50 μM for 12h) to inhibit JNK (D) activity, respectively. β-actin was used as loading control. N=3 independent experiments. Bar graphs showed quantification of indicated proteins normalized to their totals. IRS1 was normalized to β-actin. Mean +/- standard error of the mean (sem). Student's paired T-test **p<0.005; *p<0.05; NS not significant. 