Neurofibrillary tangles and tau phosphorylation

Area of Science:

• Neuroscience
• Cell Biology
• Pathology

Background:

• Neurofibrillary tangles (NFTs) composed of hyperphosphorylated tau are hallmarks of Alzheimer's disease (AD).
• Microtubule stability is crucial for neuronal function.

Purpose of the Study:

• Investigate the relationship between NFTs and microtubule stability.
• Examine how tau phosphorylation and function are affected in AD models.
• Determine the role of glycogen synthase kinase-3 beta (GSK-3 beta) in tau phosphorylation and microtubule interactions.

Main Methods:

• Analysis of acetylated alpha-tubulin and tubulin mRNA in NFT-bearing neurons.
• Transfection studies with mutated tau forms and co-expression with beta-amyloid precursor protein and presenilins.
• Neuroanatomical study of GSK-3 beta distribution.
• Studies on GSK-3 beta activity in cultured neurons and transfected cells.
• Generation of transgenic mouse models (tau isoform, tau + mutated presenilin 1).

Main Results:

• NFT-bearing neurons showed reduced acetylated alpha-tubulin and tubulin mRNA.
• Mutated tau forms were less effective in sustaining microtubule growth.
• GSK-3 beta compartmentalization paralleled phosphorylated tau development.
• GSK-3 beta activity controlled tau phosphorylation and microtubule interaction.
• Tau phosphorylation was unaffected by beta-amyloid precursor protein overexpression.
• Transgenic mice showed somatodendritic accumulation of phosphorylated tau but not NFTs.

Conclusions:

• Microtubule network destabilization is a key mechanism in Alzheimer's disease neuronal dysfunction.
• GSK-3 beta plays a critical role in regulating tau phosphorylation and its interaction with microtubules.
• Additional factors beyond tau and presenilin mutations may be required for NFT formation.