Amyloid plaques and neurofibrillary tangles (NFTs) are the two classic hallmarks of Alzheimer’s disease (AD), but the connection between their two respective proteins—beta-amyloid and tau—has remained mysterious. Now, a paper published on July 21 in the prestigious journal Cell details a molecular mechanism that links tau to beta-amyloid toxicity at the synapse. The groundbreaking new study was led by Professor Jürgen Götz and Dr Lars Ittner, based at the University of Sydney.
Back in 2004, scientists from the University of California at Irvine injected anti-beta-amyloid antibodies in the brains of transgenic mice that develop both beta-amyloid deposits and NFTs. This treatment led to a rapid reduction of beta-amyloid deposits and reversed the accumulation of abnormal tau (Oddo et al., 2004). When the anti-beta-amyloid antibodies were removed, the beta-amyloid pathology re-emerged. This was followed by the reappearance of tau pathology. These findings from animal models provided some proof that beta-amyloid and tau pathology were linked in that levels of beta-amyloid deposits influence levels of NFTs.
In the new findings*, researchers from the University of Sydney, show that tau is essential for the positioning of yet another protein, FYN, at the synapse, which then renders the neuron vulnerable to beta-amyloid. They demonstrate that tau functions at the synapse, and links beta-amyloid to toxicity at specific receptors, and that its effects are subsequent to beta-amyloid action. Tau-based treatments may indeed be critical in developing therapies aimed at slowing down the progression of AD.
*Ittner et al, Dendritic Function of Tau Mediates Amyloid-beta Toxicity in Alzheimer’s Disease Mouse Models. Cell. 2010 Jul 21.