MAPT and amyloidosis: Finally, it is worth noting that the presence of beta amyloid peptide, that could stimulate GSK3 [28], did not result in a change in the level of neither TIR-MAPT nor W-Tau (Fig. 5a, b), probably because GSK3 is constitutively active and, therefore, amyloid-treated cells behave as untreated control cells containing already SC35 in its phosphorylated form.