The peptidylprolyl cis/trans-isomerase Pin1 modulates stress-induced dephosphorylation of Tau in neurons. Implication in a pathological mechanism related to Alzheimer disease.

Deregulation of Tau phosphorylation is a key question in Alzheimer disease pathogenesis. Recently, Pin1, a peptidylprolyl cis/trans-isomerase, was proposed to be a new modulator in Tau phosphorylation in Alzheimer disease. In vitro, Pin1 was reported to present a high affinity for both Thr(P)-231, a crucial site for microtubule binding, and Thr(P)-212. In fact, Pin1 may facilitate Thr(P)-231 dephosphorylation by protein phosphatase 2A through trans isomerization of the Thr(P)-Pro peptide bound. However, whether Pin1 binding to Tau leads to isomerization of a single site or of multiple Ser/Thr(P)-Pro sites in vivo is still unknown. In the present study, Pin1 involvement was investigated in stress-induced Tau dephosphorylation with protein phosphatase 2A activation. Both oxidative (H2O2) and heat stresses induced hypophosphorylation of a large set of phospho-Tau epitopes in primary cortical cultures. In both cases, juglone, a Pin1 pharmacological inhibitor, partially prevented dephosphorylation of Tau at Thr-231 among a set of phosphoepitopes tested. Moreover, Pin1 is physiologically found in neurons and partially co-localized with Tau. Furthermore, in Pin1-deficient neuronal primary cultures, H2O2 stress-induced Tau dephosphorylation at Thr(P)-231 was significantly lower than in wild type neurons. Finally, Pin1 transfection in Pin1-deficient neuronal cell cultures allowed for rescuing the effect of H2O2 stress-induced Tau dephosphorylation, whereas a Pin1 catalytic mutant did not. This is the first demonstration of an in situ Pin1 involvement in a differential Tau dephosphorylation on the full-length multiphosphorylated substrate.