Microtubule-associated protein tau is expressed at high levels in neuronal cell types and is essential for stabilizing axonal microtubule assembly. In patients with neurodegenerative disorders such as Alzheimer’s disease, frontotemporal dementia, and Parkinson’s disease, tau aggregates into paired helical filaments (PHFs), which constitutes neurofibrillary tangles. Biochemical and structural studies have provided evidence that PHF tau assumes a characteristic paper-clip conformation. However, determining factors that lead to such pathological conformation of tau remain to be elucidated. In order to decipher the structural and chemical determinants of the pathological conformation of tau, we expressed full length human tau on yeast cell surface. Physiologically important isoforms of the human tau, including the 441-amino acid full-length isoform (2N4R) can be displayed at high levels on yeast cells as assessed using anti-tau antibodies. In the full-length tau displayed on yeast surface, majority of phosphorylation sites found in PHF tau are not phosphorylated, potentially due to endogenous yeast phosphatases. Interestingly, however, tau displayed on yeast cells show clear interaction with two independent anti-tau antibodies specific to the pathological conformation of tau. Moreover, the tau displayed on yeast do not interact with tubulins which constitute microtubules. These results indicate that tau displayed on yeast possesses the paper-clip conformation found in PHF tau. Based on previous finding that increased ionic strength and negatively charged species induce PHF formation, we hypothesize that the negative surface charge in yeast cell wall is responsible for PHF tau conformation. We will present our recent progress on testing this hypothesis by modulating yeast surface charge. The impact of various tau mutations that mimic phosphorylation and acetylation of tau on PHF tau conformation will also be presented. Taken together, yeast surface display provides a novel platform to efficiently identify factors that induce tau conformational change, and may lead to new discoveries on how to detect and prevent the formation of such structural variants.<br/>

Deciphering structural and chemical determinants of pathological tau conformation using yeast surface display

255th National Meeting (2018)

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