P3-011: The role of caspase-3 and caspase-6 in the generation of conformationally changed tau in a neuroblastoma cell model

Aggregation of tau is one of the main hallmarks of Alzheimer's disease and other tauopathies. Tau conformational change is one of the earliest detectable events in the brain of Alzheimer's patients. Therefore from a therapeutic perspective, inhibiting this structural modification is a particularly attractive approach. There is growing evidence that proteolytic processing of tau may play a crucial role in the aberrant change of tau conformation and its aggregation. Several studies have shown that tau can be processed by various proteases and that the tau fragments generated by these proteolytic modifications can themselves aggregate and induce aggregation of full-length tau. The aim of the work presented here was to investigate a potential link between caspase activation and the conformational change of tau in a neuroblastoma cell-based model. We set up a cell-based model with the murine neuroblastoma cell line (N2a) transiently transfected with the longest 2N4R human tau. The relationship between caspase activation and proteolytic cleavage, conformational change and aggregation of tau were followed using a combination of Western blotting, high-speed ultracentrifugation, flow cytometry and conformational MC1-ELISA methodologies. We found that activation of Caspase-6, but not Caspase-3, correlates with tau conformational change in our N2a cell-based model. We demonstrated that caspase activation causes proteolytic cleavage of tau, which leads to MC1-positive conformational change and tau aggregation. We have also shown that the above changes in tau can be slowed down by Caspase-6 and broad-spectrum caspase inhibitors. Our experimental model is suitable for investigating the role of caspases in tau cleavage and downstream conformational change and aggregation. The results suggest that therapeutics aimed at inhibiting caspase-mediated tau cleavage may prove beneficial in slowing cleavage and aggregation, thus potentially inhibiting the pathological cascade in Alzheimer's disease.