Downregulation of protein phosphatase 2A by apolipoprotein E: Implications for Alzheimer's disease.

The apolipoprotein E ε4 allele is the single most important genetic risk factor associated with Alzheimer's disease (AD). Tau phosphorylation and hyperphosphorylation is an underlying feature of AD and is regulated by specific kinases and phosphatases. Among phosphatases, protein phosphatase 2A (PP2A) is the principal tau dephosphorylating enzyme in the brain. Several abnormalities of PP2A have been reported in AD, including among others decreased protein levels of PP2A, decreased mRNA and protein levels of the catalytic subunit PP2A