Association of Cdk5 and Soluble Oligomeric Species of β-amyloid Induced Tau Hyperphosphorylation

Alzheimer's disease (AD) is a progressive neurodegenerative disease with deteriorating memory loss in the aged population. Currently, its exact pathogenesis remains elusive. Some studies have shown that soluble oligomeric Aβ (β-amyloid), inducing hyperphosphorylation of tau, may be the initial link to AD pathogenesis. However, it is poorly known how Aβ influences tau phosphorylation; Results, in this study, soluble oligomeric Aβ42 peptide was injected into the hippocampus of mice with saline as a control. Hematoxylin and eosin (HE) staining showed that Aβ42 was mainly deposited in the Cornu Ammonis area 1 (CA1). Within 7 to 21 days after the operation, the area of Aβ42 decreased gradually. Compared to the control, the expression of phosphorylated tau (p-tau) was significantly increased, suggesting that soluble Aβ oligomers activated phosphorylation of tau and increased total tau. Meanwhile, we found that elevated Cdk5, mainly in the CA1 area and subgranular zone (SGZ), correlates with increased phosphorylation of tau. Conclusions, thus, the results suggest that hyperphosphorylation of tau induced by soluble amyloid Aβ is associated with an increased level of Cdk5.