Amyloid-β Modulates Both AβPP and Tau Phosphorylation

Area of Science:

• Neuroscience
• Molecular Biology
• Biochemistry

Background:

• Alzheimer's disease (AD) is characterized by neurofibrillary tangles (tau) and amyloid plaques (Aβ).
• Aβ is implicated in altered kinase/phosphatase activity, affecting tau phosphorylation.
• Amyloid-beta precursor protein (AβPP) is hyperphosphorylated at residues like Thr668 in AD brains.

Purpose of the Study:

• To investigate the direct effect of Aβ(42) on AβPP phosphorylation at Thr668.
• To identify kinases and phosphatases involved in AβPP phosphorylation/dephosphorylation at Thr668.
• To explore the link between Aβ, AβPP phosphorylation, and tau phosphorylation.

Main Methods:

• Primary cortical neuron cultures.
• Treatment with Aβ(42) peptide.
• Analysis of AβPP phosphorylation at Thr668.
• Assays for kinase (GSK3β, Cdk5) and phosphatase (PP1, PP2B) activity.

Main Results:

• Aβ(42) significantly impacts AβPP phosphorylation at the Thr668 residue.
• GSK3β and Cdk5 mediate AβPP phosphorylation at Thr668.
• PP1 and PP2B are involved in AβPP dephosphorylation at Thr668.
• Aβ(42) increases tau phosphorylation at Ser396 and Ser262.

Conclusions:

• Aβ(42) directly modulates AβPP phosphorylation at Thr668, suggesting a feedback loop in Aβ production.
• Kinases GSK3β and Cdk5, and phosphatases PP1 and PP2B, are key players in regulating AβPP phosphorylation.
• Aβ promotes cross-talk between signaling pathways, leading to hyperphosphorylation of both AβPP and tau.
• Aβ's effect on kinases and phosphatases offers a potential mechanism linking Aβ and tau pathology in AD.