(569d) Yeast Surface Display of Full Length Human Tau for Combinatorial Antibody Profiling

Microtubule-associated protein tau is expressed at high levels in neuronal cell types and is essential for stabilizing axonal microtubule assembly. In neurodegenerative disorders such as Alzheimer’s disease, frontotemporal dementia, and Parkinson’s disease, mutations or post-translational modifications (PTMs) of tau cause its dissociation from microtubules and lead to formation of characteristic tau inclusions. In Alzheimer’s disease, recent evidences show that tau modifications at specific sites cause toxicity in neurons and can be propagated through secretion and uptake of these species. Due to the large number of PTM sites that can potentially affect this process, many antibodies targeting these modified epitopes are being generated. However, methods to rapidly characterize the specificity of these antibodies are lacking. To address this challenge, we recently succeeded in displaying human tau on the surface of yeast cells. In this presentation, we show that physiologically important isoforms of the human tau, including the 441 amino acid full-length isoform can be displayed on yeast cells by genetic fusion to the cell wall protein Aga2. We demonstrate the use of yeast cells displaying human tau to determine the epitope of anti-tau monoclonal antibodies (mAbs) and quantify their specificity. By creating site-directed mutations, we confirmed or newly determined the epitope of several widely used anti-tau mAbs. Using known phospho-specific mAbs, we show that yeast displayed tau is largely non-phosphorylated at the target sites. These sites can be phosphorylated by treatment with kinases such as protein kinase A and glycogen synthase kinase 3 beta, which have been shown to phosphorylate human tau. We show that several antibodies previously thought to be phospho-specific have strong cross reactivity towards non-phosphorylated tau. We also demonstrate combinatorial approaches for de novo identification of anti-tau antibody epitopes using a high-throughput screening. These results show that yeast displayed human tau is a powerful platform for profiling and quality control of anti-tau antibodies.