HuMCs, transduced with scrambled shRNA (shContr) or shRNA for GSK3β (shGSK3β-B), were sensitized overnight and then stimulated with SA (100 ng/ml) and SCF (30 ng/ml) for 30 min as described in materials and methods. Whole-cell extracts were prepared and immunoblotted with anti-phospho-cJun (S73), total cJun, anti-phospho-ATF2(T71), or anti-phospho-NF-κB(S536) antibodies (A). Protein loading of the samples was normalized by probing for Syk (A). Data in B–D were generated by scanning in 3–4 independent experiments and normalizing to the responses obtained with SA/SCF stimulation ( *p < 0.05 **p < 0.001 and ***p < 0.0001, by Student’s t test).