Calcium phosphatase calcineurin influences tau metabolism

Alzheimer's disease (AD) is characterized by neuronal loss and the accumulation of β-amyloid plaques and neurofibrillary tangles in the brain. Cerebrospinal fluid (CSF) levels of β-amyloid and tau/phospho-tau181 (ptau181) are also associated with AD. We have previously demonstrated that a single nucleotide polymorphism in calcineurin is associated with CSF ptau181 levels and AD progression. In this study, we demonstrate that calcineurin protein levels are inversely correlated with dementia severity and Braak tangle stage in AD brains, and calcineurin activity is globally reduced in AD brains. We then sought to model the observed changes in CSF tau by measuring extracellular tau in cultured cells. SH-SY5Y cells treated with calcineurin inhibitors produced reduced calcineurin activity and a corresponding increase in extracellular ptau181. These findings are consistent with our observations in AD patients, who have elevated CSF ptau181 and reduced calcineurin activity in brain extracts. Thus, we have identified a gene that contributes to AD pathology and has functional consequences on tau metabolism in cultured cells.