Microtubule Networks Modulate Cellular Susceptibility to Aβ-Mediated Toxicity

Abstract

Alzheimer's disease (AD) is a fatal neurodegenerative disorder that is the most common cause of dementia. The self-assembly of the β-amyloid peptide (Aβ) into ordered aggregates, including oligomers and fibrils, is a major hallmark of AD. As we age, significant alterations in our cellular structure, with implications for cellular mechanics, occur. An example of such changes are alterations in the structure of microtubules within cells. As aging is the largest risk factor for the development of AD, we investigated the role of microtubule structure on a cell's ability to cope with exposure to Aβ. Microtubules in GT1-7 cells were systematically altered using a variety of microtubule-altering drugs. Nocodazole and cholchicine were used to disrupt microtubules; paclitaxel was used to stabilize microtubules. The effectiveness of the drugs to change microtubule structure was confirmed by fluorescence microscopy and mechanical measurements using an atomic force microscope. Control cells and cells with altered microtubule structure were then exposed to monomeric and oligomeric solutions of Aβ, as confirmed by several assays. Next, we determined the extent of Aβ binding to cells using flow cytometry, cell death using a variety of toxicity assays, and Aβ-induced changes in cell mechanical properties. We found that altering microtubule structure had little effect on the ability of Aβ to bind cells. However, Aβ-related toxicity was enhanced when cells had disrupted microtubule networks, indicating that they were more sensitive to exposure to Aβ. Cells that had their microtubule networks chemically stabilized were more resistant to Aβ-related toxicity.