Fig. 6

β-catenin activation by cAMP/PPKA signaling in MSC-H cells. Intracellular cAMP level was significantly higher in MSC-H cells than MSC-C cells. HMGB1 knock-down reduced intracellular cAMP as shown in siH2 and siH3 cells (a). In accordance, PKA activity was increased in MSC-H cells but inhibited by HMGB1 knock-down (b). The Ser675 of β-catenin and the Ser9 of GSK3β were increasingly phosphorylated, which was associated with high expression of PKA catalytic subunit in MSC-H cells. HMGB1 knock-down inhibited the expression of PKA catalytic subunit and phosphorylation of β-catenin and GSK3β. c Blockage of PKA by 10 μmol/l H89 inhibited phosphorylation of β-catenin at Ser657 and GSK3β at Ser9 in MSC-H cells (d). The asterisk indicated a P value < 0.05