| Popis: |
A number of neurodegenerative diseases, including Alzheimer's disease, are associated with the deposition of aggregated tau protein in the form of neurofibrillary tangles (NFTs). Although a causal relationship between NFTs and disease has not been conclusively resolved, it is hypothesized that either the aggregates themselves or the process of aggregation is pathological. Tau is an intrinsically unstructured protein expressed in neurons, primarily functioning to stabilize and catalyze microtubule assembly. Studies indicate that tau binding of lipid vesicles may serve as a mimic of microtubule binding. We measured the affinity of the various constructs of tau encompassing the microtubule binding region to synthetic lipid vesicles using fluorescence correlation spectroscopy (FCS). Importantly, we observe that the binding behavior is dramatically affected by solution pH. At pH 7.4, the protein binds stably and we are able to extract a partition coefficient for both wild-type and the disease-associated point mutant, P301L. However, at low pH, binding to lipid bilayers triggers rapid aggregation of the tau fragments, which we were able to confirm as amyloid using Thioflavin T binding and electron microscopy. |
