Pin1 promotes production of Alzheimer's amyloid beta from beta-cleaved amyloid precursor protein

Here we show that prolyl isomerase Pin1 is involved in the Abeta production central to the pathogenesis of Alzheimer's disease. Enzyme immunoassay of brains of the Pin1-deficient mice revealed that production of Abeta40 and Abeta42 was lower than that of the wild-type mice, indicating that Pin1 promotes Abeta production in the brain. GST-Pin1 pull-down and immunoprecipitation assay revealed that Pin1 binds phosphorylated Thr668-Pro of C99. In the Pin1-/- MEF transfected with C99, Pin1 co-transfection enhanced the levels of Abeta40 and Abeta42 compared to that without Pin1 co-transfection. In COS7 cells transfected with C99, Pin1 co-transfection enhanced the generation of Abeta40 and Abeta42, and reduced the expression level of C99, facilitating the C99 turnover. Thus, Pin1 interacts with C99 and promotes its gamma-cleavage, generating Abeta40 and Abeta42. Further, GSK3 inhibitor lithium blocked Pin1 binding to C99 by decreasing Thr668 phosphorylation and attenuated Abeta generation, explaining the inhibitory effect of lithium on Abeta generation.