Quantitative live cell imaging of a tauopathy model enables the identification of a polypharmacological drug candidate that restores physiological microtubule regulation
Tauopathies such as Alzheimers disease are characterized by the aggregation and increased phosphorylation of the microtubule-associated protein tau. The pathological changes in tau are closely linked to neurodegeneration, making tau a prime candidate for intervention. However, the multiple facets of tau function and the lack of cellular tauopathy models that could support mechanism-based drug development hampers progress. Here we report the development of a live-cell imaging approach to quantitatively monitor pathological changes of human tau as it interacts with axonal microtubules. We show that a full-length aggregation-prone tau construct exhibits reduced interaction with microtubules as it increasingly aggregates. Through chemoinformatic analyses, we identified 2-phenyloxazole (PHOX) derivatives as putative polypharmacological small molecules that inhibit tau aggregation and modulate tau phosphorylation. We found that PHOX15 restores the physiological microtubule interaction of aggregation-prone tau in neurons and inhibits the first phase of tau aggregation in vitro. Furthermore, we report that PHOX15 inhibits the tau kinases GSK3{beta} and Cdk5, alters the kinome activity of model neurons, and reduces tau phosphorylation at disease-relevant sites. Molecular dynamics simulations highlight cryptic channel-like pockets crossing tau protofilaments and indicate that the binding of PHOX15 in one of the channels reduces the protofilaments ability to adopt a PHF-like conformation. The data show that our imaging approach provides a useful tool for identifying compounds that modulate tau-microtubule interaction in axons. We demonstrate that a polypharmacological approach to simultaneously treat tau aggregation and tau phosphorylation is able to restore physiological microtubule regulation, identifying PHOX15 as a promising drug candidate to counteract tau-induced neurodegeneration.