7.

S100B requires DKK-1 activation to induce Wnt pathway disruption and tau protein hyperphosphorylation. (A) SHSY5Y cells were transfected with 150 nM DKK-1 siRNA and treated with S100B 5 μM. The pGSK-3β protein expression was evaluated 24 hrs following treatment by Western blot (upper panel) and densitometric analysis of corresponding bands (lower panel). GSK-3β served as a loading control.(B) β-catenin protein expression was evaluated 24 hrs following treatment by Western blot (upper panel) and densitometric analysis of corresponding bands (lower panel). β-actin served as a loading control.(C) pppTau protein expression was evaluated 48 hrs following treatment by Western blot (upper panel) and densitometric analysis of corresponding bands (lower panel). Tau served as a loading control. Statistics show that S100B required DKK-1 activation to reduce β-catenin protein expression and to promote pGSK-3β and pppTau protein expression. Untransfected and untreated cells were used as internal controls. Results are the mean ± S.E.M. of three independent experiments. ***P < 0.001 versus untreated cells; °°°P < 0.001 versus untrans-fected cells treated with S100B 5 μM.