The aggregation of tau, a
microtubule-associated protein, is known to play an important role in several
neurological disorders including
Alzheimer's disease.
Alzheimer's disease is considered to be associated with the dyshomeostasis of
metal ions such as
aluminum,
zinc,
copper, and ferric
ions. Tau is predominately acetylated at the K274 residue in
Alzheimer's disease, and the acetylation of the K274 residue is thought to be linked with
dementia. Using acetyl mimicking K274Q mutation in tau, we have examined the effects of the acetylation at K274 residue of tau on the interactions of tau with
metal ions and also on the ability of tau to protect
DNA from the heat and other stressors. We found that Zn2+ and Al3+ increased the liquid-liquid phase separation of tau, an initial stage of tau aggregation. Further, Zn2+ and Al3+ considerably reduced the critical concentration for the phase separation of K274Q tau. Using far-UV circular dichroism and fluorescence spectroscopy, we provide evidence suggesting that the binding of Zn2+ and Al3+ induces conformational changes in tau. The K274Q mutation enhanced the binding affinity of tau for Zn2+, Al3+, Cu2+, and Fe3+
ions. In addition, Zn2+, Al3+, Cu2+, and Fe3+ significantly enhanced the aggregation propensity of K274Q tau in comparison to tau. Interestingly, tau binds to
DNA with a higher affinity than K274Q tau. Tau protects
DNA from the
DNase treatment in vitro as well as from the heat stress in
neuroblastoma cells more efficiently than K274Q tau. The results indicated that the acetylation of K274 residue of tau may increase
metal ion-induced toxicity and diminish the ability of tau to protect
DNA.